Re: News Group Dying?
bob
Check it out if you have'nt already!
http://photonlexicon.com/forums/index.php
"What now?" <news.aei.net> wrote in message news:44291f36_2@aeinews....
> Is it me or this Group is slowly dying? I see less and less postings month
> after month. Maybe the subject is dying or everybody is going
elsewhere!....
>
>
CincyPyro
lurk, as I mostly do.
What we need is a shot of the guy asking about what Xals and Valves he
needs to make his magic-marker-sized CO2 metal cutting and welding
lasers for his grandpappy for the U.S. Naval shipyards.
Somewhere, I've kept a text file of that entire conversation.
Zany, and definitely a troll...but it WAS highly entertaining, I
thought.
I could sure use an episode of "Xtals & Valves - Part 2". By the way,
how come nobody ever posted the information for the magic recipe for
his family-culture "crystals", that even their children made in their
family kitchens?
STEVE ROBERTS
comprehend the FAQ and search for past posts.
I've looked at it, and its not worth my time.
Steve Roberts
bob
"STEVE ROBERTS" <o...@uakron.edu> wrote in message
news:1143568705.3...@g10g2000cwb.googlegroups.com...
RET
For clarification: I started Photonlexicon.com and reside as its sole
Administrator.
Guy, everyone starts somewhere. PL Brings forth many varied people, most
of which do not seem to have the attitude problem and actively avoid it.
When I first heard of your post here I was quite confused... Did you get
a bad cup of coffee this morning? If so: Ill be glad to send you some
Blue mountain courtesy of the users at PL. I wonder why would anyone go
out of his way to slam a "resource".
Its not like we "lowly hobbyists" have many outlets: Candlepowerforums
is full of "pointer jockeys", other forums are terrible, Laserfx is
long dead, lasers.org is dead, and the attitude you displayed above
makes this place feel really closed off.
No one will argue that you have been quite a help here at alt.lasers
over the years. Nor will they argue that you certainly have enriched the
collective pool of knowledge, but this "nose-up snob" attitude of yours
could use some 5,9 di-chlor sulfate thrown in it.
Cant comprehend the FAQ: Sorry guy, Knowledge of lasers and optics do
not come naturally to most people. If it did for you, congrats. I am the
first to point people to the FAQ when there is something I am unable to
answer completely or have limited understanding of.
Searh for past posts: The laserfaq is a tome, as is the history of
alt.lasers. Ive made many searches in the past that did not quite
explain what I wanted to know: Be it "not knowing the right search
query" or "not wanting to sit through 30 dry posts of people arguing
trivial details about "not so common knowledge"
I started PL as a place where people could readily exchange information
they have at their disposal in a non confrontational manner with "peers"
Alt.lasers and the FAQ is wonderful, but they hardly have the feel of a
community. Something many of the PL users have pointed out and keep
coming back for.
While we are on pointed admissions: Due in part to your previous
comment, I have lost a large amount of respect for you. Not that it
means anything to you, ehh Steve-o?
I need you to understand something: for every person such as yourself
there are 100 people who just find lasers to be amazingly fun and sexy
devices. What they lack in "seniority" they make up for in drive,
determination, willpower, and personality.
In short: You are entitled to your opinions, however regressive and
counter productive they may be.
To the original poster: Yes, I feel this place is thinning out although
by looking at the statistics page of PL I can say with relative
certainty that the topic is far from dead. A quick glance at the stats
page shows me that PL has managed 44,795 *unique* page views and 312,587
overall hits just for March.
To Bob: Thank you man, Posts like that are the exact reason why I keep
shelling out cash every month for PL.
-Robert
Lostgallifreyan
Steve, you talk like a guy who worked with signal generators and filters in
the fifties, before the synthesizer inventors started to play with them.
That 'amateur hour' is the time in which people like Robert Moog will
emerge making video and laser instruments that can be used for performing
and new kinds of art. It can't emerge from an ivory tower, any more than
Pink Floyd or Tangerine Dream could have emerged from Ircam. Like Boulez
being appreciated by sternly exacting musicologists, your standpoint will
seem cold and uninviting to so many that it will be left aside for a huge
number of more rewarding ways to make things happen. I've lurked on
PhotoLexicon a few times now, and the rigour there is a very good
compromise between the exact science, and the practical use of it, and the
fun of it. It's not just better than nothing at all, it's better than
anything I've seen before with the single exception of the FAQ, and it
covers lots of things not there, and is always up to date on practical
things like how to get things economically, something the optics industry
is notorious for doing badly. This is why people are getting together, it's
the only way to beat the isolationism you seem to be wanting to maintain.
We don't see such dismissal from Sam, and he wrote (most of) that FAQ, as
far as I know.
Buffo
> photolexicon is amateur hour, with few exceptions, for people who cant
> comprehend the FAQ and search for past posts.
It is precisely this elitist attitude that drives people away from
alt.lasers. Who wants to ask a question here when all it will get them
is a smart-aleck reply from the likes of Steve Roberts?
For the record, Sam's laser FAQ is a great resource, but there is
precious little information in there that deals specifically with
hobbyist laser shows. Likewise, it's a static resource. You can't ask
it questions. (However, I should admit that have spoken directly with
Sam a few times, and he has always been very helpful.)
As for searching past posts to alt.lasers, well, the noise level here
is really high. There may be good information posted from time to
time, but more often than not it's about an obscure topic that is
relevent to only a handful of people.
When you add in the elitist attitude of some of the long-term posters
here, it's no wonder that Robert decided to start PhotonLexicon. The
attidues of the people over there are *much* easier to deal with.
> I've looked at it, and its not worth my time.
Bully for you. I suppose it has never occurred to you that there might
be other people that don't know as much as you do about lasers and
would appreciate a little guidance without the condescending attitude.
As an example of just how long this sort of thing has been going on
here in alt.lasers, allow me to remind you of a discussion back in
October 2004 that you jumped into: We were talking about a phone
conversation I had just had with the CDRH about their jurisdiction with
regard to laser shows that are done for free... (Google for "phone
call CDRH" in alt.lasers and you'll find the post I'm referring to.)
Apart from the snappy, kurt tone of your reply, the substance of your
message was that you had "paperwork that proves otherwise on some of
the statements in the above post" and that you needed "to drive to St
Louis right now and wont be able to post untill tuesday, but I will
reply then". We waited for your reply, but it never came.
Now, I was truely interested in what you had to say back then. Others
spoke highly of your knowlege and experince, so I was pleased that you
had decided to respond. And if you had a document that contradicted
what I was told, it would have been great to have the substance of that
document available. I suspect it would have spawned more calls and/or
letters to the CDRH, and perhaps led to further clarification of the
issue. Instead, you never followed up on the post, the whole thread
died, and the controversy remains. Now - how exactly is this a good
thing?
This pattern is typical of many threads here on alt.lasers - especially
threads that are started by less-experienced laser enthusiasts. Even
if one or two of the replies contain usefull information, they almost
always lead to further questions. But when those one or two
informative posts are buried in a sea of condescending replies, it's no
wonder that people take their questions elsewhere.
Bah! PhotonLexicon is a friendly place to get ANSWERS without the
attitude. It's also a great place to get ideas. The signal-to-noise
ratio is high, and arrogant know-it-alls are in short supply.
Furthermore, at least for laser show enthusiasts, there are several
professionals there that are more than willing to talk about their
craft.
I'm not saying that everyone should be spoon-fed; but a little patience
goes a long way towards bringing a beginner up to speed on a subject.
Saddly, patience is sorely lacking in a lot of alt.laser posts.
Phil Hobbs
> It is precisely this elitist attitude that drives people away from
> alt.lasers. Who wants to ask a question here when all it will get
> them is a smart-aleck reply from the likes of Steve Roberts?
Hmm.
I can't think why we might want to drive these people away from
alt.lasers, can you? We might crush their life's aspirations to be Real
Laser Hobbyists, at which point of course there would be nothing left
for them to do but to enter a Tibetan monastery.
I for one really enjoy having sunshine pounded up my nose by people who
post anonymously from Yahoo and Gmail. The similar way that these
previously-unknown persons write, and the way they all seem to have
gotten offended at once, suggests that there is exactly one poster
involved.
"On the internet, no one can tell you're a dog."
Cheers,
Phil Hobbs
Lostgallifreyan
news:442AB81...@SpamMeSenseless.pergamos.net:
Woof! >:)
LaserLover
Phil,
I agree that some posters on Alt-Lasers are condescending .
I do not consider those posters as Elite, although they might be famous
in their own minds as some academics and pseudo-intellectuals can be.
I would recomend that people retune their attitudes and If you don't
have anything good, positive, constructive to say keep your own
council.
I applaud the efforts and people at Photonlexicon.
Some humble pie could be served now !
Rick
Phil Hobbs
> I agree that some posters on Alt-Lasers are condescending .
Criticising strangers' manners is *not* condescending? Answering a few
lines of personal opinion with reams and reams of flames is not
condescending? Hello?
None of us is going to like everyone's posts, but that's what killfiles
are for--unless people keep changing their pseudonyms, as appears to be
happening here. If you think alt.lasers is bad, try
sci.electronics.design. Lots of people get helped in both places, but
posting BS is not a growth strategy. Usenet is full of trolls, flamers,
and curmudgeons.
> I do not consider those posters as Elite, although they might be famous
> in their own minds as some academics and pseudo-intellectuals can be.
And this is not condescending? Do you know any of these people?
> I would recomend that people retune their attitudes and If you don't
> have anything good, positive, constructive to say keep your own
> council.
So it's not okay to say that some bogus thing is bogus? (I haven't
looked at Photonlexicon, so I'm not expressing an opinion about that.)
> I applaud the efforts and people at Photonlexicon.
> Some humble pie could be served now !
To whom? And what for?
Sorry, but I'm not in favour of a world where people aren't free to
express their opinions....wait, wasn't there some old antiquated
unenlightened 18th-century document that talked about that somewhere?
Cheers,
Phil Hobbs
spam@frontiernet.net C what I mean
"RET" <nnt...@vonhellsing.com> wrote in message
news:EIoWf.246525$vi2....@fe03.news.easynews.com...
yadda yadda yadda.. and on and on and on....
The guy gave his opinion.. if you don't like it.. ok.. but damn.. wrap it up
already... No wonder opinions are so hard to come by on NGs.. flame wars
start so damn easy over such trivial stuff.. get some thickness to your
skin and suck it up..
Craig
bob
putting down people as a bunch of amatures...
Its ok, if you dont feel you like the place or you are above the knowledge
it gives..Cool.. But dont put down the others who enjoy it.... Thats all he
was sayin really...
I made a friendly open welcome to everyone here to come visit..., nothing
more.....
Personally , i think its a great place.
"C what I mean" <no sp...@frontiernet.net> wrote in message
news:vbAWf.4276$kg....@news02.roc.ny...
Lostgallifreyan
> None of us is going to like everyone's posts, but that's what killfiles
> are for--unless people keep changing their pseudonyms, as appears to be
> happening here. If you think alt.lasers is bad, try
> sci.electronics.design. Lots of people get helped in both places, but
> posting BS is not a growth strategy. Usenet is full of trolls, flamers,
> and curmudgeons.
>
Ok, that's twice you've mentioned the possibility of one posting as many,
so I ought to speak for myself to stop that idea getting out of hand. I
will only post in any place with ONE name, often the same name in many
places. I will not troll, or flame. I will spend most of my time either
asking questions or trying to help in answering those I know enough to
attempt answers for.
If you ever see me doing any different I'd like it if you personally let me
know. :)
I haven't used my real name but that doesn't mean I don't have one, or
conduct myself with the same care I'd use if I was talking face to face
with my ID on official record.
I suppose it's always possible that somone could use my name to try to
pretend to be me, as this is usenet, not a forum with controlled
registration, but I doubt anyone would want to. :)
I don't think any of the names posting in this thread have anything other
than a one-to-one relation to posters using them, and it's a very strange
assumption to think otherwise.
Phil Hobbs
> I haven't used my real name but that doesn't mean I don't have one, or
> conduct myself with the same care I'd use if I was talking face to face
> with my ID on official record.
So the reason for the pseudo is.....?
Cheers,
Phil Hobbs
Lostgallifreyan
Fun. I've used it for a long time, and I like using it. The net is full of
such stuff, and most of it is harmless. If you sell on eBay or something,
and I buy from you, you'd know my real name.
As it happens, my real name is 'Crow'. I doubt you'll believe this though
because it's a tad unlikely as real names go, and most computer software is
downright obdurate about expecting other fields to satisfy convention. The
only reason I'm telling you when you don't need to know, is because I'd
feel like a jerk telling you you didn't need to know as the only reason to
with-hold it. It's Crow on official records dating back nearly twenty
years.
Now a question for you: do you judge me only when I fit in your perception
of reality, or would you take any points I made in their own right?
Rhetorical, no need to answer that.. I'm tired and in a silly mood in what
has become a silly thread.
spam@frontiernet.net C what I mean
comment.. didn't see anything wrong with that.. but the one RET went on and
on and on with, just made me shake my head. And then of course everyone
else started "piling on"......
I just see too many flame wars and personal attacks happen on the four NGs I
read.. it just gets old.. ya know? People just need to get some thickness to
their skin and shake it off...
"bob" <b...@knob.com> wrote in message news:jAAWf.20835$%H.14780@clgrps13...
spam@frontiernet.net C what I mean
"Lostgallifreyan">>
Does this name mean you are a lost time lord? ;-)
Buffo
> I can't think why we might want to drive these people away from
> alt.lasers, can you?
So you admit that you're intolerant of beginners. Brilliant...
> I for one really enjoy having sunshine pounded up my nose by people who
> post anonymously from Yahoo and Gmail. The similar way that these
> previously-unknown persons write, and the way they all seem to have
> gotten offended at once, suggests that there is exactly one poster
> involved.
And with this statement you just proved that you didn't bother to read
the post from October, 2004 that I referenced above. For if you had,
you would know my identity and also know that your assertation that
"there is exactly one poster involved" is completely false. (How's
your foot taste today?)
It's clear that you don't care about the facts of the matter - you just
want to spout your opinion and sound important. And I grant you that
there is an 18th century document granting you the right to be as
obstinate as you wish. But if you are unwilling to even investigate an
issue before you share your opinion, then your opinion means exactly
nothing.
L. Michael Roberts
What now? wrote:
> Is it me or this Group is slowly dying? I see less and less postings month
> after month. Maybe the subject is dying or everybody is going elsewhere!....
To me, I see this group as quality over quantity. The conversations
are generally enlightening and almost always civil... and there is
remarkably little Spam! :)
--
+==================== L. Michael Roberts ======================+
This represents my personal opinion and NOT Company policy
Goderich, Ont, Canada. To reply, post a request for my valid E-mail
"Life is a sexually transmitted, terminal, condition"
+================================================================+
Adam Aglionby
Though alt.lasers is shrinking like most of usenet that I read anyway
:-(
Personally prefer usenet to moderated forums, moderators neccesarily
shape forums in their own image , usenet as Don Lancaster put it, is
where the sole purpose of posting is to `gang bang the cripples`
YMMV
Adam
Skywise
some comments.
It does seem that more stuff is moving towards web based forums.
Personally, I can't stand them. Terribly inefficient. With usenet
and a good newsreader, I only need one key press to get the next
message. Formatting is a breeze, and threading is maintained
automatically. On web forums, there's a lot of clicking and it
is difficult to know at a glance where the new messages are, or
to jump to them, or....etc...
alt.lasers is very free of spam and other crap. Somewhere in this
thread comment was made about this group having trolls, flame wars,
etc...compared to some groups, this group is tame. For the groups
I read, some of the astro ones are useless as they are almost all
totally kooks and "einstein is wrong" type crap. Not a logical
thought for days at a time. But this is due to the perseverence
of the knwledgeable regulars. I think we don't have these problems
here because we jump all over it and nip it in the bud quite quickly.
Also, I have to wonder what is being discussed in web forums that
can't be discussed in an appropriate newsgroup? From my experience
in the earthquake related groups, I'd say it's because they have
an agenda, and it's usually an anti-science one, and they want a
forum free from facts getting in the way of their 'research'. I
have not read enough of the forum in question in this thread to
determine if that's the case there. It doesn't appear to be so far.
But I find it difficult to imagine that to be the case.
Then there's the issue of searchability and archiving. Thanks to
Google, you can read alt.lasers all the way back to 1996. Web forums
are subject to the whims of the moderator (and any agendas) and
the whims of web hosts crashing and losing all the data.
Usenet will never die. It may get slower, but it will always be
here. How it's used and the quality of its content will be up to
those who take the time to keep the signal to noise ratio high.
As for this entire thread, I think it's been blown out of proportion.
Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
Lostgallifreyan
>
> "Lostgallifreyan">>
>
> Does this name mean you are a lost time lord? ;-)
>
>
>
Ny namesake is. :) I read the books as a kid (no TV), and saw the Tom Baker
shows whenever possible. Only 'hero' I ever had as a kid. What's great
about the handle 'lostgallifreyan' is it's so far unique on the net, (which
is the point of handles, names are often duplicated), it doesn't specify
exactly WHICH Gallifreyan is lost. I have so much fun with that... >:)
spam@frontiernet.net C what I mean
:
>> "Lostgallifreyan">>
>>
>> Does this name mean you are a lost time lord? ;-)
>
> Ny namesake is. :) I read the books as a kid (no TV), and saw the Tom
> Baker
> shows whenever possible. Only 'hero' I ever had as a kid. What's great
> about the handle 'lostgallifreyan' is it's so far unique on the net,
> (which
> is the point of handles, names are often duplicated), it doesn't specify
> exactly WHICH Gallifreyan is lost. I have so much fun with that... >:)
Tom was the first Doctor I ever saw and actually the one I really liked.
The first time I saw the show it was very late at night on PBS. It looked
so Sci-Fi lame that I just had to see what it was. Turned out I watched
every Baker show and some Pertwee, Peter Davidson and a few others.. but Tom
was one that hooked me on the show.
I see it has come back. I watched two episodes and was not that impressed
but I will continue to see if it gets any better. I guess I liked the cheesy
effects and the stories.
Buffo
> It does seem that more stuff is moving towards web based forums.
> Personally, I can't stand them. Terribly inefficient.
You have a good point there. I suppose because I'm also active on a
couple other web-based forums (including boatered.com) I just got used
to the web interface, and phpbb in particular. But I agree that a good
newsreader runs circles around a web forum.
> alt.lasers is very free of spam and other crap.
True. However, most web based forum are equally free of spam, and for
the same reason. The users (and the host, ususally) are just as quick
to squelch spam when it pops up.
> Also, I have to wonder what is being discussed in web forums that
> can't be discussed in an appropriate newsgroup?
Specifically, hobbyist laser topics. Laser show ideas. How-to
articles on building (and troubleshooting) your own DAC. Comments on
the suitability of the various software packages available. Advice
about building your own projector housing. And all of it without the
heavy-handed, "I've been doing this for 15 years, fear me!" attitude.
Don't get me wrong; there are *plenty* of knowlegible folks here on
alt.lasers that have been very helpful and do not display the attitude
I'm speaking about above. But there are a few here that do. And to a
beginniner, it only takes a couple exposures to that sort of attitude
before one stops asking questions.
> From my experience
> I'd say it's because they have
> an agenda, and it's usually an anti-science one, and they want a
> forum free from facts getting in the way of their 'research'.
I understand your concern. PhotonLexicon is not a forum dedicated to
quackery. The members are most certainly not anti-science. However,
the folks there are willing to discuss alternatives to get people
involved with lasers and laser shows, even if they can't afford the
latest and greatest toys.
When I first got started in lasers (~1990 or so), I couldn't afford
much more than a 10 mw HeNe and some spinning mirrors. I was warned
that you couldn't do an indoor laser show with only 10 mw, even if it
was only in my living room... But in reality, 10 mw looks pretty cool
if you have a dark room and enough fog.
Now, I've since learned that 50 mw of argon looks a lot better, and 100
mw of dps green is just about ideal, at least for my living room. But
the people that were trying to tell me that it was hopeless to try a
show with only 10 mw were wrong. And why were they saying that?
Because they were "in the business" and felt that anyone with less than
a large frame water-cooled whitelight didn't belong in their club.
> I have not read enough of the forum in question in this thread to
> determine if that's the case there. It doesn't appear to be so far.
Indeed, it is not. I encourage you to have a look, even though the
interface may not be nearly as efficient. The discussions there run
the gamut from beginner to professional. (As an example of one of the
more advanced threads, a few of the members are developing and
improving their own custom 16-bit DAC that is said to be vastly
superior to the QM 2000 boards from Pangolin. I haven't had the
opportunity to see one in action yet, but it looks like they will be
bringing one to the SELEM this summer.)
> Then there's the issue of searchability and archiving. Thanks to
> Google, you can read alt.lasers all the way back to 1996.
Yup. No arguement there. And your other point about loosing the
contents of a web forum due to a hardware malfuction is equally valid,
though I'm pretty sure Robert's host provider maintains backups of the
forum.
> Web forums
> are subject to the whims of the moderator (and any agendas)
Robert doesn't have an agenda that I'm aware of, apart from creating a
place where laser enthusiasts can share ideas. So far it seems to be
working out quite well. Several commercial laserists post regularly
about their craft, and the rest of the users are learning from them.
This is one aspect of a web forum that you rarely see on USNET: people
spontaneously sharing their experiences without being asked. And
though I haven't been there all that long myself, I can't recall a
single post that was deleted. (Though one post that was clearly an
advert was moved to the for-sale section where it belonged...)
> Usenet will never die.
Probably not. But I believe its utility has decreased. In time, it
may improve, but the fact that alternatives are springing up to take
its place speaks volumes about what is wrong with USNET in general and
with a select few personalities on alt.lasers in particular.
spam@frontiernet.net C what I mean
but I still feel comments are warranted... Please read below.
"Buffo" <buffo...@gmail.com> wrote in message
news:1143729622.4...@e56g2000cwe.googlegroups.com...
> snip<
>> > When I first got started in lasers (~1990 or so), I couldn't afford
> much more than a 10 mw HeNe and some spinning mirrors. I was warned
> that you couldn't do an indoor laser show with only 10 mw, even if it
> was only in my living room... But in reality, 10 mw looks pretty cool
> if you have a dark room and enough fog.
re: your comment about enough fog and a dark enough room.. Well the dark is
correct, but the part about fog is not necessarily correct. Too much fog
will actually hinder your ability to deliver a good beam. What you want is
the right amount of particulate matter, haze is better I think, that the
light will have plenty to reflect off of without attinuating the beam too
much. You may not have meant lots and lots of fog, but many people seem to
have the illusion that more is better when it comes to fog.
>
> Now, I've since learned that 50 mw of argon looks a lot better, and 100
> mw of dps green is just about ideal, at least for my living room. But
> the people that were trying to tell me that it was hopeless to try a
> show with only 10 mw were wrong. And why were they saying that?
> Because they were "in the business" and felt that anyone with less than
> a large frame water-cooled whitelight didn't belong in their club.
Actually the reason they might have been saying that is because 10mW is not
enough to do a quality show in anything much bigger than your living room**.
Just because you can see the beam most of the time doesn't mean you are
delivering what a quality laser show should be. This is one of the pet
peeves of many of the people "in the business". Too many hobbyists, hacks
and wanna bees out there with under powered systems shooting around sub
standard show content, charging a little money for it, and calling it a
professional show. It hurts the industry as a whole because some potential
client see this hobby grade stuff and think that is what a real professional
show looks like. If you want to do a show for your friends with 10mW that
is very cool but the type listed above hurts, not helps, the laser show
industry as a whole.
**10mW of 532nm is bright enough to use in some small, dark clubs for flying
beams around, but nothing much larger. And if they have any ambient light
it really starts washing out the laser beams quickly! But.. it can be done..
And if you are wondering, I am a hobbits myself so I am not considered, "in
the business". (as a matter of fact I haven't had the pleasure of doing a
show in two years) ;-(
>
>> I have not read enough of the forum in question in this thread to
>> determine if that's the case there. It doesn't appear to be so far.
>
> Indeed, it is not. I encourage you to have a look, even though the
> interface may not be nearly as efficient. The discussions there run
> the gamut from beginner to professional. (As an example of one of the
> more advanced threads, a few of the members are developing and
> improving their own custom 16-bit DAC that is said to be vastly
> superior to the QM 2000 boards from Pangolin. I haven't had the
> opportunity to see one in action yet, but it looks like they will be
> bringing one to the SELEM this summer.)
>
>> snip<
I doubt you will get a 16-bit DAC system that is "vastly superior to the
QM2000". Vastly is a very big word and you would have to do some mighty
incredible stuff to obtain a "vastly superior" outcome regarding the DACs
and how they effect a show. Remember, you are driving mechanical devices
with that output and there is only so much that you can do electrically to
noticeably improve the perceived outcome.
STEVE ROBERTS
at Photolexicon is how do I hook up my "KeWL lAsEr Dood" little Chinese
Yags with a few skilled people contributing some real gems. What I dont
like is the attitude there about laser safety, whats shown in many
pictures is SICKENING. How many kids there can pay the 3500$ MRI bill
my mom paid for me to determine if I had a retinal burn or optical
neuropathy when I discovered a vision problem in sunlight driving back
from a all nite rave about 6 years ago when I was not fully employed.
In my case it was neuropathy, not a burn, but..... Too many lax
attitudes at that site. Its my opinion, not a prediction of the end
of the world. Grow up folks.
And Robert, you probably want to put up a disclaimer on there, if you
havent already, before somebody's lawyer gets to you, that reads "
What we do here in the privacy of our own basement is fine, but we
should not provide risk to others when we demo the toy, as we are
considered a "expert" just because we own it, and people will trust us
to know what we are doing."
And other then the few real nutcases who show up wanting the AA battery
powered megalaser to burn people at movies who let their cell phones
ring, when have I EVER dissed some newbie?
26 posts and growing, now we know some people are still on this group.
Steve Roberts
my own opinions only.
Pat B.
novice- a beginner, pursues an area of study with interest
hobbyist - a novice who derives satisfaction from his area of study
amateur- a novice hobbyist who has no education but has some level of
equipment that one should have training on and is probably dangerous
educated- a professionally trained amateur educated with knowledge of
facts
professional- earning a living on his training and education in his
area of study, usually aluf
veteran- a seasoned professional, knowledgeable, forthright, has
provided a significant contribution to the industry in his area of
study
geezer - one that has been there and done that. Quit Whining, Pick a
F*&^%&G box and get in it.
I too am appalled at all the amateurs with $50.00 to buy a green lasers
and hands it to his stoned friend and says ..."now don't point it at
any ones eyes" and the first thing he does is shine it into his own
eyes or cars or planes. The other box is called "goofy turds"
geezer
Buffo
> re: your comment about enough fog and a dark enough room.. Well the dark is
> correct, but the part about fog is not necessarily correct. Too much fog
> will actually hinder your ability to deliver a good beam. What you want is
> the right amount of particulate matter, haze is better I think,
I agree completely. However, hazers are a lot more expensive that
foggers. (Foggers can be had at Walmart for 40 bucks these days!) I
also discovered that one of my foggers (a Chauvet) produces a very fine
fog that hangs in the air for quite a while. The other one (Walmart
special) makes a thicker fog that tends to occlude the beams - hence I
seldom use that one anymore. The brand of fog juice makes a difference
too!
> but many people seem to
> have the illusion that more is better when it comes to fog.
True. And the way you just explained it, it would be easy for someone
that had the wrong idea to see your point, and learn from it, without
feeling threatened.
> Actually the reason they might have been saying that is because 10mW is not
> enough to do a quality show in anything much bigger than your living room**.
> Just because you can see the beam most of the time doesn't mean you are
> delivering what a quality laser show should be.
See, now this is the attitude that I have a problem with. A hobbyist
isn't going to be able to recreate the Pink Floyd experience in his
living room unless his Dad is Bill Gates. But he might be able to
accomplish some cool beam effects, even if they are monochrome, which
is a start. Assuming that he stays interested in lasers, he may one
day work up to a full-color whitelight system. But to deny him that
initial experience on the grounds that it "isn't what a proper laser
show should be" is just silly.
When I drag out my electric guitar to play, it's not a proper rock
concert either. But I enjoy it, and it sounds good enough to me and my
family. Am I doing Van Halen a disservice by not being as good on the
guitar as Eddie?
> Too many hobbyists, hacks
> and wanna bees out there with under powered systems shooting around sub
> standard show content, charging a little money for it, and calling it a
> professional show. It hurts the industry as a whole because some potential
> client see this hobby grade stuff and think that is what a real professional
> show looks like.
Ok, now if I had actually met *anyone* doing this sort of thing for
hire, I would agree with you. But the few people I've actually met
that do laser shows for a living all have multiple lasers, multiple
scan heads, and usually run either Pangolin or X-29 software (or
both!). As such, they have tens of thousands of dollars invested in
their equipment, and any comparison to the lame effects I can pull off
in my livingroom are downright absurd.
Furthermore, the few times I've seen a laser show in public, it has
been *QUITE* the production. No 10 mw beams here... More like 10
watts or more, and that was in a small theater downtown... Great
visuals, incredible lumina effects, thunderous music, all expertly
choreographed. Best $12 I ever spent... (And I really felt sorry for
the college kids that showed up stoned - they had no idea what they
were missing...)
The hobbyists on Photon Lexicon, taken as a whole, are not out to do
laser shows commercially. (Though there are some people already doing
it for a living that hang out there.) Most members are out to learn
more about the technology and build cool projectors for their own
amusement. That's not to say that some of the hobbyists won't at some
point go commercial, but I think it's going to be a significant
minority. (One of the great things about having a few "professional"
laserists in the group that are willing to share ideas is that you
learn really quick that it's *HARD* to make a lot of money in the laser
business...) And I don't know of anyone there that believes you can
make money with a 10 mw projector...
> And if you are wondering, I am a hobbits myself so I am not considered, "in
> the business". (as a matter of fact I haven't had the pleasure of doing a
> show in two years) ;-(
Well, I've been a hobbyist for 15 years, and I've *never* done a show.
(Unless you count the ones in my living room, that is....)
> I doubt you will get a 16-bit DAC system that is "vastly superior to the
> QM2000". Vastly is a very big word and you would have to do some mighty
> incredible stuff to obtain a "vastly superior" outcome regarding the DACs
> and how they effect a show. Remember, you are driving mechanical devices
> with that output and there is only so much that you can do electrically to
> noticeably improve the perceived outcome.
I thought so as well, until I read up on the issues that the developers
had with Pangolin. Specifically, with the way Pangolin handles the
color pallette, and the way it handles anchor points. Now, I'm no
electrical engineer, and I'm no laser show expert either. But having
read what they've posted about the problems, and having looked at their
solution and the specs they claim for it, I'd say they've done
something quite amazing.
Have a look for yourself and see what you think:
http://www.photonlexicon.com/forums/viewtopic.php?t=268
spam@frontiernet.net C what I mean
<snip>
>> Actually the reason they might have been saying that is because 10mW is
>> not
>> enough to do a quality show in anything much bigger than your living
>> room**.
>> Just because you can see the beam most of the time doesn't mean you are
>> delivering what a quality laser show should be.
>
> See, now this is the attitude that I have a problem with. A hobbyist
> isn't going to be able to recreate the Pink Floyd experience in his
> living room unless his Dad is Bill Gates. But he might be able to
> accomplish some cool beam effects, even if they are monochrome, which
> is a start. Assuming that he stays interested in lasers, he may one
> day work up to a full-color whitelight system. But to deny him that
> initial experience on the grounds that it "isn't what a proper laser
> show should be" is just silly.
This is not an attitude, it is a real reason. I have seen hacks come in
with low power lasers and just fly beams around for about $500 when they are
not legal or good. Unfortuanatly many that make a living doing show and are
professionals have lost a lot of business to the hacks that take the work
for a fraction of what the price should be and fall flat on their faces.
Then when the next time comes around the client is jaded toward lasers.. It
happens a lot. That is why you here so many pros complaining about it.
If you read my post I said "If you want to do a show for your friends with
10mW that is very cool" I made a distinction between the two I thought.
> When I drag out my electric guitar to play, it's not a proper rock
> concert either. But I enjoy it, and it sounds good enough to me and my
> family. Am I doing Van Halen a disservice by not being as good on the
> guitar as Eddie?
Not a good analogy.. here is why.. there are tens of thousands of guitar
players and millions of songs using guitar music. Most people have some
idea of what good playing sounds like and what playing around sounds like.
Not necessarily so with laser shows. They are not that common.
>
>> Too many hobbyists, hacks
>> and wanna bees out there with under powered systems shooting around sub
>> standard show content, charging a little money for it, and calling it a
>> professional show. It hurts the industry as a whole because some
>> potential
>> client see this hobby grade stuff and think that is what a real
>> professional
>> show looks like.
>
> Ok, now if I had actually met *anyone* doing this sort of thing for
> hire, I would agree with you. But the few people I've actually met
> that do laser shows for a living all have multiple lasers, multiple
> scan heads, and usually run either Pangolin or X-29 software (or
> both!). As such, they have tens of thousands of dollars invested in
> their equipment, and any comparison to the lame effects I can pull off
> in my livingroom are downright absurd.
I have met serveral and seen several that have done what I discribed above..
charged for a substandard show.
I started with X-29-2 (the higher end version) and still have two of
them.(wanna buy one?). I also have Pangolin Pros as well, both QM32 (wanna
buy one?) and QM2000s. Even with those, and the many white lasers, Yags,
and scanner sets I have, I still can't consider myself professional. The
paying gigs I have done over the years all started by me explaining to the
clients that I do this as a hobby and I am not a pro. I have done about 15
total jobs over the years. Most for charity or for the neighbors.. But never
too cheap if pay wa involved, and never shorted the job for equipment.
The point of all that was to show you that I didn't compare you to a pro, as
I can't compare myself with one either. I was generically explaining why
the sentiment from people in the business.
>
> Furthermore, the few times I've seen a laser show in public, it has
> been *QUITE* the production. No 10 mw beams here... More like 10
> watts or more, and that was in a small theater downtown... Great
> visuals, incredible lumina effects, thunderous music, all expertly
> choreographed. Best $12 I ever spent... (And I really felt sorry for
> the college kids that showed up stoned - they had no idea what they
> were missing...)
>
THAT IS A VERY GOOD THING!!! And kinda makes some what part of my point.
What if you had seen the hacks first?
> The hobbyists on Photon Lexicon, taken as a whole, are not out to do
> laser shows commercially. (Though there are some people already doing
> it for a living that hang out there.) Most members are out to learn
> more about the technology and build cool projectors for their own
> amusement. That's not to say that some of the hobbyists won't at some
> point go commercial, but I think it's going to be a significant
> minority. (One of the great things about having a few "professional"
> laserists in the group that are willing to share ideas is that you
> learn really quick that it's *HARD* to make a lot of money in the laser
> business...) And I don't know of anyone there that believes you can
> make money with a 10 mw projector...
Actually MY comments had nothing to do with the Photon Lexicon site.
Remember I said it was off topic?
>
>> And if you are wondering, I am a hobbits myself so I am not considered,
>> "in
>> the business". (as a matter of fact I haven't had the pleasure of doing
>> a
>> show in two years) ;-(
>
> Well, I've been a hobbyist for 15 years, and I've *never* done a show.
> (Unless you count the ones in my living room, that is....)
>
>> I doubt you will get a 16-bit DAC system that is "vastly superior to the
>> QM2000". Vastly is a very big word and you would have to do some mighty
>> incredible stuff to obtain a "vastly superior" outcome regarding the DACs
>> and how they effect a show. Remember, you are driving mechanical devices
>> with that output and there is only so much that you can do electrically
>> to
>> noticeably improve the perceived outcome.
>
> I thought so as well, until I read up on the issues that the developers
> had with Pangolin. Specifically, with the way Pangolin handles the
> color pallette, and the way it handles anchor points. Now, I'm no
> electrical engineer, and I'm no laser show expert either. But having
> read what they've posted about the problems, and having looked at their
> solution and the specs they claim for it, I'd say they've done
> something quite amazing.
>
> Have a look for yourself and see what you think:
> http://www.photonlexicon.com/forums/viewtopic.php?t=268
That was interesting, but I would have to reserve judgement until I
physically saw the difference in outcome.. although what they are doing
really isn't something that has to do with the DACs like you stated. It is
more about how they are driving the DACs with the other hardware and
software.
Anyway, good responses.
Skywise
@e56g2000cwe.googlegroups.com:
> Skywise wrote:
<Snipola>
>> Also, I have to wonder what is being discussed in web forums that
>> can't be discussed in an appropriate newsgroup?
>
> Specifically, hobbyist laser topics. Laser show ideas. How-to
> articles on building (and troubleshooting) your own DAC. Comments on
> the suitability of the various software packages available. Advice
> about building your own projector housing. And all of it without the
> heavy-handed, "I've been doing this for 15 years, fear me!" attitude.
All of which I'm sure would be acceptable discussion right here
in this newsgroup. Perhaps that's why this group is so 'dead'?
> Don't get me wrong; there are *plenty* of knowlegible folks here on
> alt.lasers that have been very helpful and do not display the attitude
> I'm speaking about above. But there are a few here that do. And to a
> beginniner, it only takes a couple exposures to that sort of attitude
> before one stops asking questions.
There's a solution to posts by people one does not like. It's called
a killfile. Which is another disadvantage of web based forums. "No
user serviceable filters inside."
Also, what's to prevent this 'attitude' from occuring on the web
forum. I see it on the some of the other forums I read. Many people
including myself have complained about a particular user and the
moderator openly took the other side. Well, we managed to drive off
the problem individual without the help of the moderator. The point
being, it can happen even on PhotonLexicon.
Of course, it's a given that it can happen in an unmoderated newsgroup.
In fact, it should be expected due ot it's very nature. I'd consider
it an intrinsic property of usenet; and alt.lasers is probably the
tamest of the usenet groups I read. But there are tools to get around
that problem - filters and killfiles, which, again, are unavailable on
web forums.
<Snipola>
>> Web forums
>> are subject to the whims of the moderator (and any agendas)
>
> Robert doesn't have an agenda that I'm aware of, apart from creating a
> place where laser enthusiasts can share ideas.
Then that is a unique place. Every web based forum I've been to
has an agenda, else, why would it exist? The people make their
forums so they can be masters of their tiny realm. (no implication
meant on photonlexicon) They can't handle the free form open
discussion on usenet where they might get their noses bloodied
for being idiots. (again, no implication towards photonlexicon,
just making a general point)
<Snipola>
>> Usenet will never die.
>
> Probably not. But I believe its utility has decreased. In time, it
> may improve, but the fact that alternatives are springing up to take
> its place speaks volumes about what is wrong with USNET in general and
> with a select few personalities on alt.lasers in particular.
Actually, the reason usenet is 'dying' is because it was designed
by people who know how to use computers. Now, with every 12th grader
with only a 5th grade education using a computer, everything has to
cater to that lowest common denominator. Computers used to be for
us geeks and nerds. Now it's run amok with a bunch of idiots that
have IMNSHO no business using a computer. Sorry to sound so harsh,
but computers and the internet are not easy to use properly. You
don't just hand the keys to a car without knowing they have a license,
which at least says they've gotten some formal education on how to
use the car, right?
STEVE ROBERTS
bits)
What really catches the eye are the gradients between colors, and 8
maybe 9 bits is enough for that. 16 is overkill, your eye could not
resolve a 1 bit or even a 3 bit (least sig bits) change at 16 bits.
Good pro animations have little dots of different color at the
transitions between colors, to make the gradients.
Researched limit of spatial resolution using a galvo laser scanner, 10
bits, .
Rated bandwidth of a pcaom, 100 khz, actually it can do about 300 Khz.
12 Kpps is ~13 microseconds per point, 60 Kpps is ~1.5 microseconds
per point. So blanking points are really for scanner blanked systems,
to get good color at my 24 Kpps with pcaom, I set color lag to about 3
points behind. In the mechanical old days it was color lead and
needed. Why do they claim to need so many blanking points? Anchor
points to straighten out corners are another manner. I can see
needing a few blanking points with some yags that have poor temperature
control so the slow green matches the red. Since its just a matter of
running the color data through a forward backward shift matrix in
software, the issue drops out.
I suspect the makers of that board kept their drive voltages to 0-5,
some color devices, including my Neos, need a little more, and the Neos
is notoriously non-linear when it comes to light output, and that is
mentioned in LMRs book. A opamp set to 1.1 gain usually cures that.
If you really want to see good color, set up the following. You need
one setup for each color modulated. Take a ordinary Isomet 1205 AOM
(ebay- cheap) and its TTL on/off input. This will give you about 80%
throughput at HENE. Run your 0-5 signal through a FLASH Analog to
Digital converter, 8 bits, clock the flash A to D at about 64 khz, this
means it samples each point at 12K 3-4 times. Makes sure the 64K is a
free running clock and it doesnt come from the image source. Apply the
8 bit word to a 8 bit digital comparitor, we used 2 74ls86 chips in
parallel. Use a 8 bit counter clocked at ~1 mhz to hook to the other
side of the comparitor, this gives you a digital ramp signal. What
comes out of the LS86s is a greater then , equal , or less then pulse.
Route the greater then signal to the ttl input of the Isomet driver.
This gives you fast pulse width modulation of the full on hene (or
whatever) beam, and is very near to equal steps of visual brightness,
and it looks great! Did that in 1993 or so when I couldnt afford
color hardware. Someplace on the net is the schematic of that, drawn
by Matt Polak.
Steve Roberts
STEVE ROBERTS
Steve
STEVE ROBERTS
the class IIIA limit is 4.95 mW for a cw visible laser, this is a
limiting level where in something like 9,999 out of 10,000 tries, the
blink reflex works and you dont get damage. The book that was used to
set the standards is by Sliney, et all. Above that there is no well
defined threshold, but eye surgery lasers usually adjust from ~50 mW
to 3 watts with a adjustable aiming beam of up to 7 mW on some. 7 mills
of aiming hurts like hell. Eye surgeons work at 150-250 mW for most
procedures, so your 100 mW of power you mentioned is very risky. If you
took that 100 mW to the fovea, (center of optic nerve) kiss your vision
goodbye.
Steve
STEVE ROBERTS
Lostgallifreyan
>> When I drag out my electric guitar to play, it's not a proper rock
>> concert either. But I enjoy it, and it sounds good enough to me and
>> my family. Am I doing Van Halen a disservice by not being as good on
>> the guitar as Eddie?
>
> Not a good analogy.. here is why.. there are tens of thousands of
> guitar players and millions of songs using guitar music. Most people
> have some idea of what good playing sounds like and what playing
> around sounds like. Not necessarily so with laser shows. They are not
> that common.
>
Actually it is a good argument. :) A show is to entertain. No-one is born
knowing what good guitaring is, or good lasering. If people are in the
least fascinated by either at any stage in their life, they'll try to
experience it more than once, and they'll make their own judegment
according to which entertains them most, and the better quality show has a
very good chance of it.
There are matters of taste as well though, Hendrix made sounds that are
murder to ears adjusted only to Mozart, but he's one of the finest
guitarists who ever played, and if someone manages to improvise a laser
show to produce something with no patterns, no text, no choreographed scene
changes and has no idea of what an anchor point is, and uses only a single
beam, but manages to do thing with it that can make people get up and
dance, is this a bad show, or a good one? :)
Lostgallifreyan
news:1143758289.3...@t31g2000cwb.googlegroups.com:
> Researched limit of the number of colors the eye can see, ~64 (about 6
> bits)
>
> What really catches the eye are the gradients between colors, and 8
> maybe 9 bits is enough for that. 16 is overkill, your eye could not
> resolve a 1 bit or even a 3 bit (least sig bits) change at 16 bits.
> Good pro animations have little dots of different color at the
> transitions between colors, to make the gradients.
>
I must question this one.
On a computer monitor displying colur images with 16 bits per channel, an
image has noticeable countours that disappear when moving to 32 bits.
Context means a lot, I guess, we notice more subtle things when there is a
smooth change in large areas that with temporal changes or fine lines. So I
can see that a laser show is likely to need a lot less than 32 bits, but I
suspect that many people are going to notice the stepping (aliasing) badly
if you limit to as little as eight.
I'd guess that 16 is about right, and as a 16 bit DAC is usually very cheap
it makes sense to use one.
Lostgallifreyan
> If you really want to see good color, set up the following. You need
> one setup for each color modulated. Take a ordinary Isomet 1205 AOM
> (ebay- cheap) and its TTL on/off input.
Thankyou! :) I read the rest of that PWM control idea and it rocks.
Assuming you plan for safety at max power, there is no reason not to do it
this way, given a high enough clock speed to make fades look good to both
eyes and cameras. I've had a different thought to the actual hardware and
not looked deeply at it, but it is this:
A 24 bit 96 KHz 8 channel audio interface costs maybe £200 ($360).
Considering the costs of three PCAOM's, and their drivers, maybe it is
economical to risk buying AOM's and drivers, and an audio interface,
bypassing its decoupling capacitors to allow DC output. At that cost I
doubt there's any point in worrying about excess bit depth and speed, the
point being that there is definitely enough of both. You get two channels
for X/Y, and two for each colour channel, use as appropriate. I've read
that linearity is not ideal in those interfaces, but I suspect it's pretty
good at that level of gear.
Tha advantages are that software can do most of the work, outputting
through a single software driver and hardware output that is prebuilt, and
made cheap by the huge demands of the audio industry.
Tom Yu
Lostgallifreyan> I must question this one. On a computer monitor
Lostgallifreyan> displying colur images with 16 bits per channel, an
Lostgallifreyan> image has noticeable countours that disappear when
Lostgallifreyan> moving to 32 bits.
16 bits per channel? Most computer video hardware I'm familiar with
only goes up to 8 bits per channel... 8 R, 8 G, 8 B, maybe 8 alpha.
---Tom
Lostgallifreyan
space.mit.edu:
True.
Sorry. :)
I got confused by all that high colour and true colour stuff for a moment
and even overlooked the fact that when tweaking colurs I never see more
than 256 possible choiuces for R G or B.
I guess the 16 and 23 bit settings either relate to the way the computer
stores combined values, or accomodates the varying effects of using
multiple pallettes at one time.
Lostgallifreyan
And, I notice that the limit to 8 bits might mainly be acceptable because a
VDU isn't very bright. Given the dynamic range of a laser show, I'd think
that 16 bits might be nicer, and as I mentioned in another post, can be
cheap to do by adapting existing hardware.
Buffo
> with low power lasers and just fly beams around for about $500 when they are
> That is why you here so many pros complaining about it.
> If you read my post I said "If you want to do a show for your friends with
> 10mW that is very cool" I made a distinction between the two I thought.
Indeed, you did make the distinction, which I missed the first time.
My apologies. And I understand your concern about unsafe shows with
careless operators spraying beams around in violation of the CDRH's
rules.
As to operators that simply produce "cheap" shows that are otherwise
*safe*, but merely undercut more professional ones, well, there I don't
really follow your logic.
I have not experienced a show like you've detailed. But I can see how
a hobbyist could get carried away and think that a single laser and a
set of open-loop galvos hooked to a signal generator could constitute a
"laser show". (Mind you, I would never pay decent money to see such a
show!)
But nevertheless, if a club owner or trade-show host is willing to pay
for the service (however lame it may be), then I don't see where the
problem is. The prospective client could always pay more money and get
a full color show from someone more professional instead... I see this
more as a marketing problem for the larger shows than a fault of the
beginner operator. (And, again, I'm assuming that the show is
performed safely and carries a current CDRH variance, and also operates
within those safety limits spelled out in 10 CFR 21...)
I agree that from a personal standpoint, if I were ever to perform a
public laser show I would *NEED* to make it something really special.
Call it pride, call it not wanting to be embarassed, or just call it
wanting to give the customer his money's worth. And I won't have the
kind of equipment to pull off a show like that for quite some time yet.
But that's just me...
> Most people have some
> idea of what good playing sounds like and what playing around sounds like.
> Not necessarily so with laser shows. They are not that common.
Ok, I can understand that. But then is it not the duty of the laser
show provider to sell the potential client on the benefits of a
superior laser show? I just don't see how it's the burden of the
hobbyist...
> I have met serveral and seen several that have done what I discribed above..
> charged for a substandard show.
I'm curious - were the clients themselves dissatisfied with the show(s)
you saw? (IE: Did you ask the customer later on if he/she was happy
with the performance?) The reason I ask is that it may be that, like
me, you assumed that a laser show should always be something
breathtaking. However, I can envision a scenario where a club owner
only has $X budget, and thus a monochrome beam show is all he could
afford. I'm not saying that I'd do business that way, but I don't
think it's right to dictate exactly how other people spend their money.
> I started with X-29-2 (the higher end version) and still have two of
> them.(wanna buy one?).
Sure! I'd love to buy one! You're asking the wrong question though.
If you ask, "Can you afford to buy one?" then you'll get the truth...
(And saddly, the truth is - no... Not yet.)
> I also have Pangolin Pros as well, both QM32 (wanna
> buy one?)
Same answer! (Though I'll keep you in mind when I get the funds...
grin!)
> Even with those, and the many white lasers, Yags,
> and scanner sets I have, I still can't consider myself professional.
Well, that's starting to sound like modesty there... You clearly have
enough equipment to pull off just about any effect you want. And
surely in the years it's taken you to amass all that gear you've
developed a little creativity with regard to creating laser animations.
> The point of all that was to show you that I didn't compare you to a pro, as
> I can't compare myself with one either. I was generically explaining why
> the sentiment from people in the business.
I think the definition of "pro" takes on a different meaning depending
on the venue. If you're doing laser effects to suppliment a dance hall
or concert, that is quite different from performing a stand-alone laser
show where the lasers are the only attraction.
> What if you had seen the hacks first?
Well, I have seen a few 5mw red lissajous boxes running at local dance
clubs over the years. I think most patrons realize that such units are
pretty cheezy though, and are nothing like a real laser show. (Much
like the mirrored ball in a dance hall is cheezy too, but the lights
around the stage at a rock concert are awesome to behold...)
> Actually MY comments had nothing to do with the Photon Lexicon site.
> Remember I said it was off topic?
Point taken; my apologies. I retract my original comments about
PhotonLexicon members.
> >> I doubt you will get a 16-bit DAC system that is "vastly superior to the
> >> QM2000".
> That was interesting, but I would have to reserve judgement until I
> physically saw the difference in outcome.. although what they are doing
> really isn't something that has to do with the DACs like you stated. It is
> more about how they are driving the DACs with the other hardware and
> software.
True... I was using the term DAC in the generic sense, when in truth
they are building an entire controller, of which the DAC is but a small
part. I'm looking forward to seeing the unit perform side-by-side with
a Pangolin QM2000 board this summer at the SELEM...
> Anyway, good responses.
Ditto!
STEVE ROBERTS
Tha advantages are that software can do most of the work, outputting
through a single software driver and hardware output that is prebuilt,
and
made cheap by the huge demands of the audio indu
like linux? then what you want is sorta here, if hes got a timeline
system figgured out yet.
talk to James Lehman and get Laserboy. it likes sound cards, in fact it
only runs on sound cards ;-)
Steve Roberts
STEVE ROBERTS
through a single software driver and hardware output that is prebuilt,
and
made cheap by the huge demands of the audio indu
The galvo resolution tests were done by Pango, using volunteer
observers. details are on their web site.
The color test was done by another laser company some years ago. 16.8
million color possibilities, or however many trillion the QM2000 does,
are a marketing gimmick.
Some time next week I'll dig out my copy of Laser Beam Scanning by
Marshall and pull out the galvo resolution equation, as well as the AO
resolution equation and post them,
Its different for a galvo in a printer with enhancing optics and a
grating for feedback then it it is for the bare eye, yes a galvo can
hit 16 bits in a printer if not 24, but in the outdoor situation
projecting on a screen its much different.
Steve Roberts
Lostgallifreyan
Windows 98. W95 shell on it. :) But if it runs on OpenBSD I'd have more
reason to try exploring that further.
In your other recent post you mentioned galvo tests. I guess you're meaning
that the limiting factor for resolution and repeatability for position are
in those, (not the DAC's, as I read elsewhere)? That makes sense to me, as
physical position sensing is far harder to do accurately. If it were not
so, we might still be using Babbage machines as computers if speed were
unimportant...
Still, we can always use less bits than are offered. :) And off-the-shelf
audio at 16+ bits with 8 channels might be cheaper to buy secondhand than a
2 channel 8 bit system is to build. At least, it is by the time you've
fitted a really solid system together, for a one-off project, even without
counting the value of time spent.
spam@frontiernet.net C what I mean
"Lostgallifreyan" <no-...@nowhere.net> wrote in message
news:Xns979725AD7DE1Dlo...@140.99.99.130...
> "C what I mean" <no sp...@frontiernet.net> wrote in
> news:vhYWf.4409$kg....@news02.roc.ny:
>
>>> When I drag out my electric guitar to play, it's not a proper rock
>>> concert either. But I enjoy it, and it sounds good enough to me and
>>> my family. Am I doing Van Halen a disservice by not being as good on
>>> the guitar as Eddie?
>>
>> Not a good analogy.. here is why.. there are tens of thousands of
>> guitar players and millions of songs using guitar music. Most people
>> have some idea of what good playing sounds like and what playing
>> around sounds like. Not necessarily so with laser shows. They are not
>> that common.
>>
>
> Actually it is a good argument. :) A show is to entertain. No-one is born
> knowing what good guitaring is, or good lasering. If people are in the
> least fascinated by either at any stage in their life, they'll try to
> experience it more than once, and they'll make their own judegment
> according to which entertains them most, and the better quality show has a
> very good chance of it.
You actually made my point for me. You are right, no one is born with it.
But pretty much everyone is exposed to guitar thru music on the radio, or
CDs or what ever source they hear it from. If they hear a song with bad
playing or they just don't like it, chances are they will hear better
playing on more material. Music is pretty much every where in one sort or
another, so you can't help but to hear the next song. It is almost
impossible for someone to only hear bad guitar playing while they grow up
and hear music, from whatever source. With laser shows that is not
necessarily the case. Some people have never seen a laser show and when
they see their first one, that may set the precedent in their minds as to
what a show is. Most likely they will not see another laser show just in
the coarse of normal day to day life. If you are a corporate client and you
hire someone that sells themselves as a pro and they hack the job, perhaps
next time you won't even listen to the pitch of someone pushing lasers.
This is where an why "the industry" get hurt from hacks. I am not talking
about small clubs with lasers as effects. I am talking shows or events.
>
> There are matters of taste as well though, Hendrix made sounds that are
> murder to ears adjusted only to Mozart, but he's one of the finest
> guitarists who ever played, and if someone manages to improvise a laser
> show to produce something with no patterns, no text, no choreographed
> scene
> changes and has no idea of what an anchor point is, and uses only a single
> beam, but manages to do thing with it that can make people get up and
> dance, is this a bad show, or a good one? :)
Good questions, but honesty not much in the realm of reality. Music would
be the get up and dance thing. The single beam would most likely not
entertain anyone very long, let alone a group of people. Unless of course
you are like me and can't stop watching when "the light" is on the move...
but then again, I am a very small minority.. But even I get bored quickly
from less then creative lasers.
spam@frontiernet.net C what I mean
>C what I mean wrote:
> As to operators that simply produce "cheap" shows that are otherwise
> *safe*, but merely undercut more professional ones, well, there I don't
> really follow your logic.
Ok.. assuming safe is a given, which is often not the case.... it is not
just a matter of cheap, it is also a matter of lack of quality that allows
cheap to happen. If someone is selling the same type of show or at least
the same caliber of show as a pro and they are not a pro themselves... ok..
then let the market decide. But most of the time the hack (for lack of a
shorter word meaning non professional) sells what they can't or don't
deliver. Most don't carry insurance, adhere to the CDRH rules, or have the
staff or equipment necessary to do the show with the same outcome. If the
hack delivers the same caliber of show as the pro and carries the insurance
and abides by the rules.. and they do all the work themselves with no
staff.. ok I have no heartache with that. I have done that myself once or
twice without undercutting the market pricing.
>
> I have not experienced a show like you've detailed. But I can see how
> a hobbyist could get carried away and think that a single laser and a
> set of open-loop galvos hooked to a signal generator could constitute a
> "laser show". (Mind you, I would never pay decent money to see such a
> show!)
Yes.. trust me, some do get carried away! LOL! But let me ask you this..
How would you know until you have paid your money that the show was not a
good show? Unless you have feedback from others on a repeating show... you
can't know.. so you may just pay your money and get disappointed.. But in
all fairness that can happen to a pro show as well. Less likely, but it can
happen.
>
> But nevertheless, if a club owner or trade-show host is willing to pay
> for the service (however lame it may be), then I don't see where the
> problem is. The prospective client could always pay more money and get
> a full color show from someone more professional instead... I see this
> more as a marketing problem for the larger shows than a fault of the
> beginner operator. (And, again, I'm assuming that the show is
> performed safely and carries a current CDRH variance, and also operates
> within those safety limits spelled out in 10 CFR 21...)
Pretty much I am not talking about a few effects in a club. I am talking
corporate shows or full blown laser or multimedia shows. The problem here
again is not that the client can pay more and get more. The problem is that
if the hack sells his show as being the same quality and he doesn't
deliver.. that causes problems for the next time when.. if there ever is a
next time. If the hack delivers.. no problem... and many hack shows do
fine.. and when they do, they leave the door open for the next time.. then
the pro better come to the table with a better proposal or loose out.
Again that assumption of safety.. that is a very big assumption! Trust me
on that one... ;-)
>
> I agree that from a personal standpoint, if I were ever to perform a
> public laser show I would *NEED* to make it something really special.
> Call it pride, call it not wanting to be embarassed, or just call it
> wanting to give the customer his money's worth. And I won't have the
> kind of equipment to pull off a show like that for quite some time yet.
> But that's just me...
Many hacks are like that, including me. It is a good thing.. you don't have
to be a pro to do a good show!
>> Most people have some
>> idea of what good playing sounds like and what playing around sounds
>> like.
>> Not necessarily so with laser shows. They are not that common.
>
> Ok, I can understand that. But then is it not the duty of the laser
> show provider to sell the potential client on the benefits of a
> superior laser show? I just don't see how it's the burden of the
> hobbyist...
It is not always a matter of sales. If a hack comes in and does a sales
pitch that the client buys but does't perform up to the pitch.. that is
where the doors close for later shows by either the hack or the pro.
(again, the work hack is just a short way of non professional)
>> I have met serveral and seen several that have done what I discribed
>> above..
>> charged for a substandard show.
>
> I'm curious - were the clients themselves dissatisfied with the show(s)
> you saw? (IE: Did you ask the customer later on if he/she was happy
> with the performance?) The reason I ask is that it may be that, like
> me, you assumed that a laser show should always be something
> breathtaking. However, I can envision a scenario where a club owner
> only has $X budget, and thus a monochrome beam show is all he could
> afford. I'm not saying that I'd do business that way, but I don't
> think it's right to dictate exactly how other people spend their money.
>
I have seen client just happy as clams. I have also seen them pissed off to
the point of never wanting a laser show again because they think lasers
suck, and all from that one performance. Many times the boss will tell the
people in charge of events not to even entertain lasers cause they don't
like them.. and all from one bad show.. That is mainly my point I guess..
Again.. not talking about clubs with a few beam effects..
> Well, that's starting to sound like modesty there... You clearly have
> enough equipment to pull off just about any effect you want. And
> surely in the years it's taken you to amass all that gear you've
> developed a little creativity with regard to creating laser animations.
Not modest.. just have a good taste of reality.. honestly! I have the
equipment and I think I have the creativity to put shows together, but I
have seen my shows and I have seen real professional shows.. Mine are pretty
good and I carry insurance and have a variance and do it all legally.. but I
still wouldn't pretend to be professional. I am just a hack... The shows I
have done required me to have others draw.. (I couldn't draw a straight line
with a CAD system). I digitize and put the show together with music and I
do the concepts.. but again.. still a hack..
>snip<
>> >> I doubt you will get a 16-bit DAC system that is "vastly superior to
>> >> the
>> >> QM2000".
>> That was interesting, but I would have to reserve judgement until I
>> physically saw the difference in outcome.. although what they are doing
>> really isn't something that has to do with the DACs like you stated. It
>> is
>> more about how they are driving the DACs with the other hardware and
>> software.
>
> True... I was using the term DAC in the generic sense, when in truth
> they are building an entire controller, of which the DAC is but a small
> part. I'm looking forward to seeing the unit perform side-by-side with
> a Pangolin QM2000 board this summer at the SELEM...
Let us know how it looks and if it is really that much better, if it is
better at all.
Lostgallifreyan
they can agree standards and publish them. That's what ILDA and regulations
(not law) are for. You can't stop people from wanting to try to make money
from a lesser show, but you can make their aspirations have a better
direction by making sure that clients know what the standards are. ILDA, as
trade union, or something...
Btw, I meant as accompaniment to music. :) While a laser controller might
be adept as a solo instrument, I doubt either technology or performance are
up to it yet.
STEVE ROBERTS
money
from a lesser show, but you can make their aspirations have a better
direction by making sure that clients know what the standards are.
ILDA, as
trade union, or something."
ILDA's hired a PR firm to start just that.
Plus a ILDA "ONLINE SAFETY TEST" web based varience is in the proposal
stage, see this Months Laser Focus World.
Steve
spam@frontiernet.net C what I mean
Funny you should mention that.. years ago Tim Walsh brought a piece to ILDA
where he used the scanner output to make music. I think what he did was
program the scans so that the output, when put to an audio amp, produced a
type of music. It was a cool concept and we all got a kick out it. Now
there is a good artist! Tim Walsh.. many could learn a thing or two from
him.. me included.
STEVE ROBERTS
meaning
that the limiting factor for resolution and repeatability for position
are
in those, (not the DAC's, as I read elsewhere)? That makes sense to me,
as
physical position sensing is far harder to do accurately. If it were
not
so, we might still be using Babbage machines as computers if speed were
unimportant...
The speed limit for water cooled cambridges with custom amps is about
60-100 Kpps,depending on who you talk to, but it is a angle vs speed
trade off. I can tune probably just about any feedback galvo to 65
kpps at point 1 degrees optical scan angle,but thats useless unless you
have a 1000 foot throw to the screen. So when you at a more practical
7-15 degrees, speed falls way off due to inertia of the rotor. in a
dome sweet dome, (love those planeteria) your gonna want a lot more
then 15". Full dome 180' scanning exists, using a specialized wide
angle lens, but it has a limit on what the scanners can do, and its
still very slow. So you always have to specify "jump time and angle"
or "PPS and Angle and test pattern used." small jumps act much
different then large "ballistic" jumps. and you can tune to favor
large jumps or small jumps. GSI's web site has a excellent discription
of the physics in their mini-sax manual, a free PDF download. So does
Cambridge in their manuals, if you can get one on teh web. Both
usually specify 2 or 4 different types of tuning instructions for
given galvo amp, tradeoffs of speed, angle and accuracy. . Worth a
read. Also , the standard is usually a tradeoff, so just about anybody
can display your image, if your willing to deviate from standard, only
your projector can play it, which is a bad thing when you consider the
time and work to create one minute of animation at pro 15 frames a
second or even amateur 3-4 frames a second. Go to the GSI web site,
and get the book, it would take hours of typing to spill it all out
here, although I could show you one diagram that spills the beans, I
dont have acess to alt.binariies via google.
I cant draw,and like C what I mean, I can only rotoscope from video
or autotrace, or use a image taped to a pen pad, so I'm screwed and
have to have others do my graphics, so I must tune to the ILDA
standard. My actual chorography I can do myself on pango, and beam
shows are not a real problem.
Steve
Lostgallifreyan
I Googled, but did not find, I guess I'd need to me signed up to see it, as
the search results on the LFW site had something that was close, but off-
limits to me right now. :)
That's a cool idea, the online test. If as well as safety it covered some
'general' knowledge of show making, a lot of lesser show makers will be
competing with each other to see if they can pass the test. That way at
least it won't be ignorance that makes a bad show and an empty pocket.
I've asked people in the UK, regarding safety and regulations, and the
responses I've had have been so diverse that there is no consensus at all
in the views I've had, even on basic things like safety requirements. An
online test could be fun, and might solve that problem in a month, if it
were extremely easy to find and have a go at.
Eventually law will take over, especially if eye accidents make politicians
in the House of Commons start asking tough stuff at Prime Minister's
Questions, so the sooner there is good consensus and well-publicised
standards, the more able professionals will be able to protect themselves
from foolish laws made in the absence of good guidance.
I'll enjoy taking that online test if I get a chance, it might teach me
more in five minutes than I've learned in a year.
Lostgallifreyan
That's a damn good idea. For one thing, the idea of performing has to match
the limits in the instrument, and sounding out the instrument as his
example would do might make it faster to see what can work well when using
musical gear as a way to move and modulate light. I have vague visons that
make current animations seem clunky, but no practical idea of how they
might work. One of the visions that truly inspires me is that of Samuel Ray
Delany, read his 'Nova', the passages decribing the 'sensory syrinx'.
STEVE ROBERTS
and is active on standards committess. ELDA or ELSA or ELA something
exists, but I dont know how active they are, other then they
standardize the UK scan failure safeguards. John is a very practical
fellow and actually carries out measurements etc.
I think they changed the agency name, but:
from the ILDA web site.
National Radiological Protection Board (NRPB)
Chilton, Didcot, Oxfon, OX11 ORQ, United Kingdom
Phone: (+44) 1235-822673, Fax: (+44) 1235-822650
E-Mail: john....@nrpb.org, Website: www.nrpb.org
Contact: John O'Hagan
UK public authority which carries out research and provides advice on
all aspects of radiological protection. NRPB works closely with laser
display companies, venue managers, promoters and regulators to ensure
safe laser shows in the UK, and consistent standards worldwide.
Steve
Lostgallifreyan
Thankyou :) I'll save that note. I grabbed that Mini-SAX manual you
mentioned in another post too, I had a quick look at it and it tells it
exactly the way I think I can grasp it. :) The diagrams are especially
clear.
Sleep for me now, was up at 02:00 GMT this morning...
James Lehman
technology of lasers even more so than their own egos or personal
motivations, then yes I agree that PL is a bunch of amateurs.
I was invited to PL some time ago and I have found every bit of the
interaction there to be positive and motivating.
The professionals are at the very top!
Take a look at this:
http://www.ilda.wa.org/StandardsDocs/IDTF05-finaldraft.pdf
And then this:
http://www.akrobiz.com/laserboy/ilda_file_format.html
There is most likely one person holding the ILDA spec where it is and a
couple of others who don't care enough about it. That's what I call
professional!
James. :o)
"STEVE ROBERTS" <o...@uakron.edu> wrote in message
news:1143568705.3...@g10g2000cwb.googlegroups.com...
> photolexicon is amateur hour, with few exceptions, for people who cant
> comprehend the FAQ and search for past posts.
> I've looked at it, and its not worth my time.
>
> Steve Roberts
>
STEVE ROBERTS
blanking, the pcaom being in for driver repair.
How good is your current sound card ? Would you get your gang together
and set up a pug raster at 6,8, 9, 10,12 bits of color depth
and get a subjective opinion on limiting resolution, you of all people
know how to do a audio blind A-B test so a visual wouldnt be hard for
you.
Then maybe do it with a abstract and a vector image. I'm thinking,
after seeing a demo of a multimegapixel 10 bit monitor with a 10 bit
camera recently that there is a upper limit well below 24 bits.
I cant do a good test because my pango has that Z depth shading
feature/bug. I'll see if Doug Dulmage (laser video old timer) knows how
many bits to stop at.
Use the MSBs so the outside voltage level is constant? I'm betting
about 10 bits tops for eye with laser. 24 gonna be overkill.
looks like we're gonna end up with ilda1 and ilda2 formats, and of
course they wont make it dot IL2 would they?
Steve
STEVE ROBERTS
DougD
>Then maybe do it with a abstract and a vector image. I'm thinking,
>after seeing a demo of a multimegapixel 10 bit monitor with a 10 bit
>camera recently that there is a upper limit well below 24 bits.
>I cant do a good test because my pango has that Z depth shading
>feature/bug. I'll see if Doug Dulmage (laser video old timer) knows how
>many bits to stop at.
>Use the MSBs so the outside voltage level is constant? I'm betting
>about 10 bits tops for eye with laser. 24 gonna be overkill.
Old Timer!!? Old F*^& maybe...
Anywho... If I was going to build another laser video projector these days, I
would try to stick to the spec's that are laid out in the "Digital Cinema
Initiative" which is still at V.1 as of June 05. They call out 12 bits per any
color component, i.e. RGB, although there are other color space formats
available.
No matter what any type of spec's there are, there are always going to
be hardware limitations that may just waste the bit depth. You'd have to look
at whatever your modulation scheme is going to be, most likely AO. Most AO
modulators have fairly high contrast or extinction ratio's, but that can be
misleading as that typically is for the optical modulator, and not including
the driver. Getting a 10 watt 85mhz driver to be linear through 12 bits of rez
can be tricky, as well as $$. I'm not sure what NEOS spec's are like these
days, they used to be very good for a "production line" device. The thing that
got me into the laser video was that I moonlighted for about 5 years for an
OEM of Crystal Tech. that made all of their custom AO drivers, and I've got
a few thousand hours of coil bending and tweaking on trying to get the
extinction to spec for stuff like Hell print systems, as well as some still
classified satellite devices that were just barely able to do 10 bit (but this
was in the analog 80's).
Try and get your hands on a copy of the DCI, it's a very interesting
read, especially the security aspects which are somewhat mind boggling.
This is going to be the benchmark for all motion imaging within 10 years,
so now is the time to start thinking about having to compete with visual
systems that are going to be able to visually "tweak" a viewer in a raster
format the way that lasers do now in vector..
Again, the old F's $.0000002
D.
--
James Lehman
one example of a color laser projector. The quality of resolution of color
has everything to do with which lines are being used for red, green, and
blue; whether there are other colors in there; whether the red, green or
blue is actually more than one line; the quality and dynamic range of the
PCAOM, etc. etc. If you take a look at this:
http://www.akrobiz.com/laserboy/avi/hue_tint_shade.avi
You will see a spiral scan of some 1530 (I think) hues with each one tinted
to white and shaded to black, plus a strip of gray scale at the bottom. As
you can see in the AVI, there are very distinct boundaries between the color
regions and the only real obvious gradient variations appear at the extreme
ends of tint and shade. In other words, my color setup doesn't have very
good dynamic range.
The point of how-many-bits-should-we-use is purely a computer science issue.
It has very little to do with the huge range of possible laser hardware
setups. It has everything to do with being a best-fit, universal answer.
There are no native 10 or 12 bit data types, so forget that! The idea of 24
bit true color (8, 8, 8) is itself overkill in almost all cases, but it fits
into computer memory just fine. It also leaves just enough room for some
math without having to worry too much about loss of information due to bit
growth. For galvo position, 8 bits is not enough, so 16 is the next logical
choice. Using 24 bit audio for this would be completely absurd. One factor
that will most likely always improve image quality is a higher sample rate.
Finding an audio card that really can do 96 or 192KHz into all 6 or 8
channels would be fabulous!
The issue with the broken ILDA file format is purely an example of what a
stubborn, arrogant person can do to an organization that should have better
goals. Anyone with a passing understanding of computer science and data
types can tell you that the outdated "current" proposal is busted. And it's
really stupid. It doesn't shine a good light on the only organization in the
world that should care about such a thing. And the fact that no one from
outside of the organization can offer any influence is absolutely pathetic.
James. :o)
"STEVE ROBERTS" <o...@uakron.edu> wrote in message
news:1143851641.0...@e56g2000cwe.googlegroups.com...
Lostgallifreyan
news:DJAXf.76998$g91....@tornado.ohiordc.rr.com:
> Using 24 bit audio for this would be completely absurd. One factor
> that will most likely always improve image quality is a higher sample
> rate. Finding an audio card that really can do 96 or 192KHz into all 6
> or 8 channels would be fabulous!
Echo Layla 24/96, £200 secondhand. 8 channels, including an ADAT mode with
8 channels all digital out. It puts out 24 bits depth but you don't have to
use them all. :)
PCI card for these fits MAC's too. Early Laylas can be fussy about
mainboard chipsets, but the echoaudio.com site explains all.
James Lehman
at best. It might let you lay the data in the RAM in 32 bit chunks for
speed, but ultimately it will come out of the lookup table as a value from 0
to 255 for red, green and blue. That is what a monitor needs to work.
There are some special cards out there that can do 12 bits for each color,
but these are very expensive and are made for digital medical imaging, like
X-rays, CAT scans, etc.
The 16 bit color depth setting you see on some video cards is 16 bits for
ALL three colors combined; as in 5 bits for red, 6 bits for green and 5 bits
for blue. It is less color information than 24 bits and if you set your
video card to 16 bits, you can see obvious banding in 24 bit images that
have smooth color transitions.
James. :o)
"Lostgallifreyan" <no-...@nowhere.net> wrote in message
news:Xns9797439F99D06lo...@140.99.99.130...
Buffo
STEVE ROBERTS wrote:
> Pittsburg to East Akron is around a hour and a half.
Huh?
Who lives in Eask Akron? Or Pittsburg for that matter?
(I'm in Charleston, and Robert is in Atlanta...)
Buffo
STEVE ROBERTS wrote:
> Researched limit of the number of colors the eye can see, ~64 (about 6
> bits)
Actually, I had always hear the number quoted as 1 to 10 million, with
the generally accepted average of around 4 million. A cursory google
search seems to confirm this. What is your source for the "64 color"
limit of human eyesight?
> What really catches the eye are the gradients between colors
What is the difference between a "color gradient between colors" and
more colors? Aren't they the same thing?
> Good pro animations have little dots of different color at the
> transitions between colors, to make the gradients.
I think what Yadda and his group were trying to do is give complete
color control to the artist without forcing the artist to do the
dithering by hand. (The artist picks the color and the hardware does
the rest.)
As to whether 16 bits is overkill or not, I think their point was that
8 bits isn't enough, and the next logical step would be 16 bits.
(Especially since everything else in their controller is already
running at that level of precision)
> So blanking points are really for scanner blanked systems,
Yes - Yadda has posted several times that scanner blanked systems are
often easier to set up because everything has the same timing. I think
his comments about blanking points need to be taken in the context of
his other posts about the subject.
> Why do they claim to need so many blanking points?
Good question. Ask him! (I honestly don't have a clue.)
> If you really want to see good color, set up the following. You need
> one setup for each color modulated. Take a ordinary Isomet 1205 AOM
> (ebay- cheap) and its TTL on/off input. <huge snip>
Now this is an interesting idea, and one that we've discussed in
another way on PhotonLexicon before... Namely, using a TTL blanking
device to get analog color control via pulse-width modulation. (Though
we weren't speaking of using an AOM, but rather the TTL blanking on a
DPSS driver... The problem, as always, is that it's not linear due to
the thermal cycling which causes profound power loss...)
Your explaination of the modulation circuit is far superior to the
method we come up with. Come to think of it, I'm sitting on three
1205's with drivers, and I *finally* got the power supply working for
the driver... I'm going to archive your idea and hopefully I can give
it a shot later this summer. (Thanks!)
> Someplace on the net is the schematic of that, drawn
> by Matt Polak.
Even better! Though a quick Google search didn't turn up anything,
I'll be sure to keep an eye out for it.
Buffo
I guess I'll keep it here. (For the benefit of everyone else, the
topic was safety. I had admited to sticking my head inside a scanned
circle to view the spectacular light tunnel effect produced by my 100
mw dpss greenie on numerous occaisions, and was asking if others had
serious misgivings about the practice.)
I agree that 100 mw is way above what is considered eye safe, and I
also recognise that I'm taking a small risk. However, the risk of
total scanner failure is minimal, in my estimation. Add in the chance
that when the scanners fail, they should happen to swing to a point
aimed directly at my eye (when they were scanning way around it) and I
feel the risk is reduced to an extremely low level. Photographs of the
classic "time tunnel" effect by nearly every laserist I've ever run
across seem to suggest that this is a fairly common practice.
More to the point, in the 15-20 years or so that lasers have been
available to hobbyists, laser-related vision injuries are surprisingly
rare. This, despite the fact that you routinely see "professionals"
working around entertainment laser systems without goggles on. (I use
the term "working" loosely; I mean that they are close enough to touch
the beam without protective eyewear.) Likewise, nearly every
photograph or video of a beam show that I've ever seen is taken from a
position within the scan angle of the projector - which is clearly a
no-no as far as the CDRH is concerned...
I do not question that the human eye can be damaged by laser light.
Nor do I dispute the fact that laser eye damage could go unnoticed for
years due to the brain's ability to combine images from both eyes to
compensate for blind spots. (Like the ones we all have where the optic
nerve joins the retina in our eyes.) And for the record, I do own
goggles for both broad-band red lasers and a set for all the argon
wavelengths. I wear the googles whenever I'm doing up-close work, or
working with mirrors/optics/mouts, etc... But when I'm running the
galvos, I normally don't wear them.
It just seems that I've heard far too many anecdotal stories of people
getting "flashed" by 100 mw or more yet suffering no ill effects... I
understand that "anecdote" isn't the same as data, but I'd still expect
to read about lots more eye injuries.
Buffo
> they see their first one, that may set the precedent in their minds as to
> what a show is. Most likely they will not see another laser show just in
> the coarse of normal day to day life. If you are a corporate client and you
> hire someone that sells themselves as a pro and they hack the job, perhaps
> next time you won't even listen to the pitch of someone pushing lasers.
> This is where an why "the industry" get hurt from hacks.
I see where you're coming from now. And while I've certainly seen a
few less-than-steller laser display systems in nightclubs, the true
"laser shows" that I've seen (where the lasers are the star of the
show, and essentially the only form of visual entertainment present)
have all been over-the-top. Evidently I've been fortunate in that
regard.
> The single beam would most likely not
> entertain anyone very long, let alone a group of people. Unless of course
> you are like me and can't stop watching when "the light" is on the move...
> but then again, I am a very small minority..
Not among laser geeks, you aren't! I can watch a beam show for hours -
and up until a few years ago my beam shows in my living room were
produced with nothing more advanced than diffraction gratings and
rotating mounts. (Yeah, yeah, I know... Lame as hell. But it still
looked cool, and I did have RGB color, even if I couldn't blank it back
then.)
Buffo
> >> Also, I have to wonder what is being discussed in web forums that
> >> can't be discussed in an appropriate newsgroup?
> > Specifically, hobbyist laser topics. <snip>
> All of which I'm sure would be acceptable discussion right here
> in this newsgroup. Perhaps that's why this group is so 'dead'?
I agree - they would be acceptable. However, the past discussions on
laser show ideas are in the minority of the posts on this newsgroup.
Sam himself has admitted that he's not really a "show" person. He
loves lasers, and knows a lot about them, but has no aspirations about
building a projector. That doesn't mean that there aren't others here
that *do* enjoy talking about shows and show topics, but the posting
history does seem rather thin in that area... (As a whole, however,
alt.lasers seems to be thriving.)
Furthermore, USNET in general can be trying at times. Lots of old-hand
computer gurus that have answered each and every question a hundred
times, and are now tired of answering it. Patience is sometimes in
short supply. Believe me, I know. Back in the day I used to be quite
active on comp.sys.amiga, and it got downright ugly towards the end.
And I'm no saint either. I got just as impatient as everyone else did
with all the newbies asking lame questions like, "how can I get AGA on
my A500?" or "what games can I play with a Video Toaster?" Grrr...
Now, again I have to admit that most of the people here on alt.lasers
have resisted the urge to succumb to "curmudgeon's disease", and the
bulk of the posts here are civil.
> There's a solution to posts by people one does not like. It's called
> a killfile. Which is another disadvantage of web based forums. "No
> user serviceable filters inside."
This is actually one of the features that I sometimes don't like about
USNET, and rarely if ever use myself... It's too easy to ignore people
that you don't want to listen to. Granted, there are times when it's
needed, but using a killfile can limit the discussion. (To make a
really bad analogy, it's like having mod points on slashdot, and then
browsing the comments you want to moderate at + 3... You'll never find
anything good unless you slog through EVERYTHING at -1 looking for the
few gems that have been either posted anonymously or modded down
unfairly.)
> Also, what's to prevent this 'attitude' from occuring on the web
> forum. I see it on the some of the other forums I read.
That's where a strong sense of community comes in to play. And there's
nothing magical about a web based forum. The same community can
develop (and has developed) on newsgroups. Though I do believe that
one positive aspect of a web forum is the sharing of pictures via the
linked gallery. That does seem to pull people together a bit. (And
like it or not, I think Avatars help too - bandwidth hogs though they
may be.)
> the point
> being, it can happen even on PhotonLexicon.
Granted. I hope it doesn't, but we'll see.
> > Robert doesn't have an agenda that I'm aware of, apart from creating a
> > place where laser enthusiasts can share ideas.
> Then that is a unique place. Every web based forum I've been to
> has an agenda, else, why would it exist?
Well, then I'd have to say that you haven't been to very many happy web
forums... The ones I frequent are founded by hard working people that
are fiercely passionate about the topic they are interested in. That's
not to say they're out to be lords of their domain (no pun intended!),
but rather that they want to enjoy their hobby and learn from others.
> They can't handle the free form open
> discussion on usenet where they might get their noses bloodied
> for being idiots.
Ok, I know what you mean there, and I've been to a few sites that would
meet that sort of definition. But they don't last long. The forums
that last are not started by idiots. For that matter, I don't have
time to waste on forums that are started by, or frequented by,
idiots...
If you'll permit me to dive off-topic for a moment here, let me offer
you an example of another sucessful web forum. Boatered.com was
started by George Van Parrys and Les Hall - two marine engineers that
had decades of experience in the boating industry. George in
particular had no ego to stroke - he'd been there and done that (and
has the publication record and engineering awards to back it up) so he
doesn't need more accolades. Likewise, Les is retired from the
industry after a sucessful career. But they wanted a forum where
boaters could discuss every facet of boating, from repair, to
purchases, to rules of the road. It's grown into a great place in the
5 years I've been there. (They've been on-line for over 8) Granted,
the site is loosely associated with their boatfix.com supply business,
but that business derives less than 3% of it's total orders from the
boatered forums. (The boating suply business pre-dates the forum by
over a decade and already enjoyed a global reach long before the forum
was concived.) Anyway, I offer it as an example of a sucessful web
forum where the founders most certainly were not afraid of getting
their noses blooddied here in usnet, but rather wanted to create a
better place for people to share information about boats.
I don't know enough about the laser industry - or Robert in particular
- to be able to make the same assessment of his skills. But I do know
that he is quite easy to talk to, and seems genuinely interested in
helping people to SAFELY discover lasers... Likewise, the site is quite
open and friendly, and as yet I've not found any hidden agenda.
> Actually, the reason usenet is 'dying' is because it was designed
> by people who know how to use computers. Now, with every 12th grader
> with only a 5th grade education using a computer, everything has to
> cater to that lowest common denominator. Computers used to be for
> us geeks and nerds.
I know lots of computer geeks. I still consider myself to be one, even
though I'm nearly 40. I also know that most of my peers are moving
away from usnet, and they all say the same thing... USNET is not what
it used to be.
For what it's worth, the new generation of computer geeks - by and
large - don't even bother checking out USNET... They jump straight to
the web, and stay there. This is another factor in the decline of the
newsgroups.
I don't mind keeping the 12th graders out, especially the ones with a
5th grade education. They've got no business fooling around with
lasers anyway - they need to spend more time in school learning how to
communicate properly. But the college kids (and the smarter high
school ones) that have more than half a brain would be welcome - if
they bothered to check the newsgroups. Saddly, many of them do not.
> You
> don't just hand the keys to a car without knowing they have a license,
Ugh - don't get me started on the whole "AOL user" stereotype. I used
to do a little computer support work on the side.
Must-control-fist-of-death....
Skywise
@i39g2000cwa.googlegroups.com:
<Snipola of whole reply>
Well, it seems you and I are pretty much on the same page on
everything. I'll have to try checking out PL.com more often and
see what's happening there. I guess I just got kinda irked at
the idea of calling alt.lasers "dead". Slower than most groups?
Yes. Dead? No.
Brian
--
http://www.skywise711.com - Lasers, Seismology, Astronomy, Skepticism
Seismic FAQ: http://www.skywise711.com/SeismicFAQ/SeismicFAQ.html
Quake "predictions": http://www.skywise711.com/quakes/EQDB/index.html
Sed quis custodiet ipsos Custodes?
Lostgallifreyan
> Just about any standard true color video card can only show you 24 bit
> color at best. It might let you lay the data in the RAM in 32 bit
> chunks for speed, but ultimately it will come out of the lookup table
> as a value from 0 to 255 for red, green and blue. That is what a
> monitor needs to work.
>
The old EGA used digital input, a VGA uses analog, so the monitor would use
whatever it is given as analog input, wouldn't it? I doubt it converts back
to digital before display, though if it did I imagine it would be just 8
bits oper channel.
Point taken about the use of bits in the computer though, I'd mentioned
contours, which is the banding you mentioned.
Lostgallifreyan
news:1143947234.6...@z34g2000cwc.googlegroups.com:
Steve is in Akron. :) See mail address... The Pittsburgh bit foozled me too
though.
Sam Goldwasser
> "Buffo" <buffo...@gmail.com> wrote in news:1143952471.955385.142460
> @i39g2000cwa.googlegroups.com:
>
> <Snipola of whole reply>
>
> Well, it seems you and I are pretty much on the same page on
> everything. I'll have to try checking out PL.com more often and
> see what's happening there. I guess I just got kinda irked at
> the idea of calling alt.lasers "dead". Slower than most groups?
> Yes. Dead? No.
Right, because the signal to noise ratio is so much higher, usually. :)
--- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html
Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.
James Lehman
red, green and blue signal lines out of the card. These lookup tables are
ALWAYS indexed with an 8 bit number for each, even when the card is in
palette mode.
James. :o)
"Lostgallifreyan" <no-...@nowhere.net> wrote in message
news:Xns97994CF37C7EAlo...@140.99.99.130...
Buffo
Lostgallifreyan wrote:
> Steve is in Akron. :) See mail address... The Pittsburgh bit foozled me too
> though.
Hmmm... I think "Introspectivell" on e-bay is also from Akron, OH.
His real name is Tom, and he professes to be getting out of the
business. (He recently moved to Charleston and has been selling all
his equipment on E-bay.) I met him once, and we were always going to
try and get together again, but lately he's become impossible to reach
via phone or e-mail... Wonder if he and Steve ever crossed paths
though...
As for Pittsburgh, yeah - I still haven't a clue. (But at least I'm
not alone in that regard!)
STEVE ROBERTS
drive. I was the laserist, and I can assure you, there was no dangerous
scanning.
fourtuanely the neuropathy damage was limited to a bit of trouble with
my left optical nerve, I still have soime troubles on days when the sky
haze matches the terrain, Ie driving in flat terrain on bright overcast
days, when sky and ground are a equal "grey"
Steve
Buffo
> Pittsburgh is where the rave I found my eye problem at .. not a 6 hour
> drive. I was the laserist, and I can assure you, there was no dangerous
> scanning.
Ahhh... I mis-read your later post about the drive home following the
rave and confused the fact that it happened 6 years ago with the time
it took you to drive home. My bad.
Still, if you were the laserist involved, then why did you suspect a
retinal burn and not some other eye malady? I mean, you said there was
no dangerous scanning going on during the show, so what was your basis
for thinking that your vision had been damaged by the lasers? Surely
if you had been flashed by the laser you would have remembered it, no?
> I still have soime troubles on days when the sky
> haze matches the terrain, Ie driving in flat terrain on bright overcast
> days, when sky and ground are a equal "grey"
Hmmm... I've met lots of people that wear glasses that complain of
similar troubles... Do you also have problems dealing with the high
contrast of on-coming headlamps when driving at night?
Skywise
news:6wy7yor...@saul.cis.upenn.edu:
> Skywise <in...@oblivion.nothing.com> writes:
>
>> "Buffo" <buffo...@gmail.com> wrote in news:1143952471.955385.142460
>> @i39g2000cwa.googlegroups.com:
>>
>> <Snipola of whole reply>
>>
>> Well, it seems you and I are pretty much on the same page on
>> everything. I'll have to try checking out PL.com more often and
>> see what's happening there. I guess I just got kinda irked at
>> the idea of calling alt.lasers "dead". Slower than most groups?
>> Yes. Dead? No.
>
> Right, because the signal to noise ratio is so much higher, usually. :)
Agreed. And pretty damned good considering it's unmoderated.
Mike Anton
"Buffo" <buffo...@gmail.com> wrote in message
news:1143949375.0...@v46g2000cwv.googlegroups.com...
<snip>
>
> It just seems that I've heard far too many anecdotal stories of people
> getting "flashed" by 100 mw or more yet suffering no ill effects... I
> understand that "anecdote" isn't the same as data, but I'd still expect
> to read about lots more eye injuries.
>
Well, I've owned a large 14W argon for the last 15 years, and never
had any eye damage issues with it, but then I am very careful. But,
I did get a retinal burn from my 120mW DPSS when I caught an
accidental flash. Note that my optometrist cannot find the spot
(though I hear this is not uncommon), but I can see it when I look for it.
It's been over a year now, so my brain has done a pretty good job of
mapping it out. Now I'm even more careful...
So, I can say that it is very easy to suffer from eye damage resulting
from 100mW size lasers. Perhaps it is even easier, as it is less
obvious as to where the beam actually is, and they are often of
much smaller diameter, than say large frame argons.
Just my 2 cents,
Mike
Buffo
> I did get a retinal burn from my 120mW DPSS when I caught an
> accidental flash. Note that my optometrist cannot find the spot
> (though I hear this is not uncommon), but I can see it when I look for it.
If you don't mind talking about it, I'm curious as to how the burn
manifests in your vision? As a blind spot, or some other abberation?
How do you go about "looking" for it? (I'm assuming something like the
two-spot test that is used to demonstrate the blind spot caused by the
optic nerve?)
Speaking of the optic nerve's blind spot - is your burn as large as the
blind spot where the optic nerve attaches to the retina? Larger?
Smaller? I'm not trying to be morbid here, I'm just genuinely curious.
Also, was there any pain associated with the incident? (Well, apart
from the natural reaction of "Damn! That was bright...")
> It's been over a year now, so my brain has done a pretty good job of
> mapping it out.
This makes sense - the brain is pretty good at things like that...
> So, I can say that it is very easy to suffer from eye damage resulting
> from 100mW size lasers. Perhaps it is even easier, as it is less
> obvious as to where the beam actually is, and they are often of
> much smaller diameter, than say large frame argons.
Interesting point... I know I'd be more concerned around a 14 watt
argon too, but perhaps that concern is misplaced. Either way, thanks
for sharing your experience!
Mike Anton
> Mike Anton wrote:
> > I did get a retinal burn from my 120mW DPSS when I caught an
> > accidental flash. Note that my optometrist cannot find the spot
> > (though I hear this is not uncommon), but I can see it when I look for
it.
>
> If you don't mind talking about it, I'm curious as to how the burn
> manifests in your vision? As a blind spot, or some other abberation?
> How do you go about "looking" for it? (I'm assuming something like the
> two-spot test that is used to demonstrate the blind spot caused by the
> optic nerve?)
It pretty much just looks like a green afterglow image, the kind you see
after
looking at something really bright, but it never goes away.
To find it, I usually just blink fast. Sometimes it shows up against
certain
colors and bright, or dark backgrounds.
>
> Speaking of the optic nerve's blind spot - is your burn as large as the
> blind spot where the optic nerve attaches to the retina? Larger?
> Smaller? I'm not trying to be morbid here, I'm just genuinely curious.
>
It's not very large, probably smaller than the optic nerve spot. I think my
spot is actually a cluster of two, one larger, and one smaller.
> Also, was there any pain associated with the incident? (Well, apart
> from the natural reaction of "Damn! That was bright...")
>
Nope no pain. Just "damn that was stupid, I hope it goes away."
<snip>
> Interesting point... I know I'd be more concerned around a 14 watt
> argon too, but perhaps that concern is misplaced. Either way, thanks
> for sharing your experience!
>
You're welcome. I'm glad I could provide you with a real incident. I must
admit, that it was a foolish thing, but at the same time it feels like a
small
badge of honor (a retina tatoo), though, I won't be repeating it, as it
could have been far worse. There are others on this group that have
also told their stories, so you might find them by searching.
Mike
highfi...@gmail.com
more laser-show oriented, whereas I see mostly technical discussions of
lasers on alt.lasers. Case in point: the president of Pangolin has
started discussing a number of laser show technicalities on PL that I
can't forsee having come up on alt.lasers.
spam@frontiernet.net C what I mean
<highfi...@gmail.com> wrote in message
news:1144072357.5...@e56g2000cwe.googlegroups.com...
and the "color bit" discussion. That is what sent him there in the first
place.. so although he is there, it came from here...
As for this NG being dead.. just look at how many replies to just this
thread. When there is a subject.. there is interest.
scribe4u2
>
> Funny you should mention that.. years ago Tim Walsh brought a piece to ILDA
> where he used the scanner output to make music. I think what he did was
> program the scans so that the output, when put to an audio amp, produced a
> type of music. It was a cool concept and we all got a kick out it. Now
> there is a good artist! Tim Walsh.. many could learn a thing or two from
> him.. me included.
Okay, I have lurked through this thread for a few days. Most don't
know me, few will remember me and even less could care less.
I ran with Pat B., was there for the inital ILDA concept around beers,
and knew Tim Walsh when he knew nothing about lasers.
Lasers have changed. What you can pick up on the open market is similar
to comparing the original computers on board NASA to todays super
laptops. Or as Pat would say, there ain't no comparison. You can buy
any power for mere pennies, and they are readily available without any
control.
BE VERY CAREFUL. Use your laser with care. Respect the business and
give deference to the older "geezers". They can still answer a quesion
or two and if it weren't for them, Argon would still be the beam of
choice. We grew up in the business and sit in awe of the talent that
is emerging.
Yes, I applaud Tim, Pat, Jimmy, Steve, Tom, Walt and any other pioneer
I have forgotten.
My hat is off to all of them. Someone should start a Laser Hall of
Fame. I will be the first to stand in line for that ticket.
Oh, well, just another geezer sounding off.
Best,
Scribe....
Lostgallifreyan
> LOL.... ok, Whatever....
>
> "STEVE ROBERTS" <o...@uakron.edu> wrote in message
> news:1143568705.3...@g10g2000cwb.googlegroups.com...
>> photolexicon is amateur hour, with few exceptions, for people who cant
>> comprehend the FAQ and search for past posts.
>> I've looked at it, and its not worth my time.
>>
>> Steve Roberts
>>
>
>
>
Oh man, this again. :) That viewpoint certainly changed, didn't it? But if
the focus of any of our groups steers back to subject and away from whose
group is better than whose, neither the original perspective, or the sharp
change, would occur. Human politics being what it is, maybe it will happen
anyway, but at least that BBC policy change I linked to in the earlier post
indicates that someone has found a way to deal with the problem by simply
removing the incentive to 'fit in'. If their new system is so public that
forums follow it with methods that reduce the need for 'membership' to
maintain good SNR, forums might be more attractive to people on Usenet, and
vice versa.
I'm really done now. I promise.
Phil Hobbs
with a geophysical instruments startup. (It's a great outfit, one that
you'll be hearing more about.)
One of the things I'm doing for them is developing highly stable lasers
for, *ahem*, hostile and size-constrained environments. I have a few
books on laser locking, e.g. Ohtsu, but I really need a more recent
summary of the field so I don't miss anything important.
Any suggestions for reviews or monographs on laser locking?
Thanks
Phil Hobbs
--
Dr Philip C D Hobbs
Principal
ElectroOptical Innovations
55 Orchard Rd
Briarcliff Manor NY 10510
845-480-2058
email: hobbs (atsign) electrooptical (period) net
http://electrooptical.net
Salmon Egg
Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:
> So, I have this one-week-per-month consulting gig in New Mexico, working
> with a geophysical instruments startup. (It's a great outfit, one that
> you'll be hearing more about.)
>
> One of the things I'm doing for them is developing highly stable lasers
> for, *ahem*, hostile and size-constrained environments. I have a few
> books on laser locking, e.g. Ohtsu, but I really need a more recent
> summary of the field so I don't miss anything important.
>
> Any suggestions for reviews or monographs on laser locking?
>
> Thanks
>
> Phil Hobbs
That is what libraries and laser conferences are for. But you know that.
Of course you can hire a consultant. Tony Siegman who is on this group
from time to time is emeritus. Intota offers some consulting. I am not
up to snuff on the subject.
Bill
--
An old man would be better off never having been born.
Phil Hobbs
Thanks.
If I had a library or laser conference right handy, that would be great.
;)
I don't need someone to do it for me. I just need to make sure I know
what relevant things other folks have done, to double-check that my
approach is the right one for the job. For instance, although I'm using
R-T locking with an optically-contacted ULE glass etalon, it might be
that there's an approach using molecular absorption lines that would
work better or be cheaper overall. A bunch of things like that have
been tried, and my most recent reference is over a decade old.
Besides, it's been too quiet round here, so I thought I'd ask.
Cheers
Lostgallifreyan
news:4D838387...@electrooptical.net:
> Besides, it's been too quiet round here
Until today, perhaps. :) My only excuse is that I haven't been here for ages.
Skywise
news:Xns9EACAC29E74...@216.196.109.145:
> Until today, perhaps. :) My only excuse is that I haven't been here for
> ages.
What do you mean ages? Just hop in that TARDIS of yours and pop
around the space-time continuum.
And don't allow any bloody Daleks follow you!!!
:)
AES
Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:
>
> I don't need someone to do it for me. I just need to make sure I know
> what relevant things other folks have done, to double-check that my
> approach is the right one for the job. For instance, although I'm using
> R-T locking with an optically-contacted ULE glass etalon, it might be
> that there's an approach using molecular absorption lines that would
> work better or be cheaper overall. A bunch of things like that have
> been tried, and my most recent reference is over a decade old.
>
For those kinds of questions, Jan Hall would be much more the guy to
chat with -- and he's approachable, and a serious need might also be a
motivator for him.
--AES
Phil Hobbs
I was visiting JILA earlier this week, coincidentally, and discussed the
problem with Jan, Jun Ye, and Dana Anderson. Great bunch of folks who
do amazing things. They're working in kind of a different regime,
though....locking to doubly-forbidden absorption lines in lattices of
trapped strontium atoms, for instance. Bose-Einstein condensations too.
Magic.
I got to visit the clock guys at NIST as well, which was neat.
What I was looking for here was a book or review paper published in the
last 10 years or so.
Lostgallifreyan
news:3AVgp.77869$BQ7....@newsfe22.ams2:
> Lostgallifreyan <no-...@nowhere.net> wrote in
> news:Xns9EACAC29E74...@216.196.109.145:
>
>> Until today, perhaps. :) My only excuse is that I haven't been here for
>> ages.
>
> What do you mean ages? Just hop in that TARDIS of yours and pop
> around the space-time continuum.
>
> And don't allow any bloody Daleks follow you!!!
>
>:)
>
> Brian
That TARDIS is SO nonfunctional, sadly...
In other news, apparently I am no longer the only Lostgallifreyan on the net.
襘O I had to get my old domain back before it got nabbed. This was easy
because not even the domain name squatters were prepared to hang on to it,
but suddenly it seems that at least two people were about to use it. But this
isn't about lasers either...
Lostgallifreyan
> Bose-Einstein condensations too.
> Magic.
>
Awesome. It seems like magic to me too, all I know is that they slow light to
a crawl, and that alone is weird enough.
Actually, these new discoveries have two aspects that seem at odds, one is
that they sometimes confirm things I've suspected for decades, like
macroscopic quantum solids existing on scales people can look at unaided, but
other times the findings are totally strange. It's hard to understand because
I don't get much info that I can grasp. Sometimes I suspect the only way to
really grasp it is to be there, to see how it connects to the world as
experienced. Quantum or no quantum, I doubt that's changed much.
Helpful person
> Phil Hobbs <pcdhSpamMeSensel...@electrooptical.net> wrote innews:4D8483C1...@electrooptical.net:
As one with no knowledge of the conditions to slow light down I have a
question. Presumably the materials have a very high refractive
index. Can conditions exist to create a lens?
Phil Hobbs
Slow light is usually made using a very narrow resonance in e.g.
rubidium vapour. The Kramers-Kronig relations (known as the causality
condition in electronics) give the relationship of phase to amplitude
variation. Group velocity is d_omega/d_k, which is very small in the
interior of a very sharp resonance.
There are other methods too, e.g. people have used spectral hole burning
to record and play back an optical pulse, so if you're willing to use a
Hollywood definition of propagation velocity, it can be as small as you
like.
Phil Hobbs
I'm not an expert, but AFAIK 'slow light' is usually made using a very
narrow resonance in e.g. rubidium vapour. The Kramers-Kronig relations
(known as the causality condition in electronics) give the relationship
of phase to amplitude variation. Group velocity is d_omega/d_k, which
is very small in the interior of a very sharp resonance.
There are other methods too, e.g. people have used spectral hole burning
to record and play back an optical pulse, so if you're willing to use a
Hollywood definition of propagation velocity, it can be as small as you
like.
Cheers
Salmon Egg
<652f443e-2cf3-4617...@17g2000prr.googlegroups.com>,
Helpful person <rrl...@yahoo.com> wrote:
Having worked on microwaves long before optics, the use of slow wave
structures such as helices and coupled resonator wave guides were not
strange. The basic idea was that the radial part of the wavefunction had
a modified bessel function rather than a bessel function dependence. Not
only that, but it was possible to have interactions when phase and group
velocities were in opposite directions. That is how backward wave
oscillators operated.
Not having studied modern slow light, is there a quantum version of the
regular vs modified bessel function approach to describe slow light?
Salmon Egg
Phil Hobbs <pcdhSpamM...@electrooptical.net> wrote:
> Slow light is usually made using a very narrow resonance in e.g.
> rubidium vapour. The Kramers-Kronig relations (known as the causality
> condition in electronics) give the relationship of phase to amplitude
> variation. Group velocity is d_omega/d_k, which is very small in the
> interior of a very sharp resonance.
In Bode's book on feedback amplifiers, he discussed realizability of
network functions. I believe those are equivalent to the Kramers-Kronig
relations. I do not know which version was discovered first.
Jürgen Appel
>>> One of the things I'm doing for them is developing highly stable lasers
>>> for, *ahem*, hostile and size-constrained environments. I have a few
>>> books on laser locking, e.g. Ohtsu, but I really need a more recent
>>> summary of the field so I don't miss anything important.
> If I had a library or laser conference right handy, that would be great.
> ;)
>
> I don't need someone to do it for me. I just need to make sure I know
> what relevant things other folks have done, to double-check that my
> approach is the right one for the job. For instance, although I'm using
> R-T locking with an optically-contacted ULE glass etalon, it might be
> that there's an approach using molecular absorption lines that would
> work better or be cheaper overall. A bunch of things like that have
> been tried, and my most recent reference is over a decade old.
As far as I know Pound-Drever-Hall-locking to an ULE cavity in vacuum is
still the state-of-the art technique to lock away frequency noise at high
sideband frequencies down to the few Hz-range. It's main advantage is that
it gives a great signal-to noise ratio and therefore needs little averaging
time. That makes it appropriate for fast feedback loops. For higher sideband
frequencies than your feedback can achieve (for example there is a nasty
180° phase shift in the transfer function for frequency modulation via diode
injection current somewhere between 1-10 MHz for most diodes) it might make
sense to protocol your error signal and correct your measurement instead, if
that is possible.
In optical atomic clock applications very low sideband frequency phase noise
(<-> frequency drifts) matters too, and thus the next step then is to lock
your stable laser to a frequency comb and from there to a frequency chain of
oscillators with lower and lower sideband frequency noise - the last and
slowest step is the lock to an atomic transition.
If the requirements are not so high, or if the power consumption or the
budget don't allow this, finding some kind of an atomic transition line
close to your laser frequency indeed gives an alternative way to avoid long
term drifts of your resonator.
Among the newer approaches that I have heard about to replace the medium- to
high phase-noise sideband frequency locks by
* Ultra-High-Q glass resonators (such as bottle-resonators or disk-
resonators made out of single crystals or glas).
* Temperature-stabilized fiber interferometers.
Unfortunately I don't have references at hand right now, but maybe I can
find some during the week.
It really depends what kind of measurements you are going to do, to what
kind of phase/frequency noise you are sensitive to, but of course you also
know that.
All the best,
Jürgen
Jürgen Appel
> Not having studied modern slow light, is there a quantum version of the
> regular vs modified bessel function approach to describe slow light?
As long as it's linear optics, the quantum mechanical equations are
identical to the classical ones and therefore their solutions are as well.
To see any quantum optical effects that are more interesting than what you
could get with a set of beam splitters you need nonlinearities.
Cheers,
Jürgen
Jürgen Appel
> As one with no knowledge of the conditions to slow light down I have a
> question.
As already mentioned for slow light no Bose-Einstein-Condensate is needed.
All you need is a spectrally narrow transparency window (or gain) in your
medium, then the Kramers-Kronig relations which relate Dispersion and
absorpton to each other lead to a group velocity < c.
The effect is first described already in
Sommerfeld, A. Über die Fortpflanzung des Lichtes in dispergierenden Medien
Annalen Der Physik, 1914, 349, 177-202
and more specifically in
Garrett, C. G. B. & McCumber, D. E. Propagation of a Gaussian Light Pulse
through an Anomalous Dispersion Medium Physical Review A, 1970, 1, 305-313
[Bose-Einstein-Condensates]
> Presumably the materials have a very high refractive
> index. Can conditions exist to create a lens?
Yes. That's actually one of the main problems when one wants to couple them
to optics: Huge optical densities in the center and strong density gradients
together with a size that is not much bigger than an optical wavelength make
BECs more often than not behave more than a scatterer than a nice optical
element.
Cheers
Jürgen