Coherent 532-200 Question
Jem
I have a Coherent 532-200 Ring Laser which I use for holography.
I accquired a nice optical table and was thinking of mounting the laser
directly on to the table. The problem with this is that there is a cooling
fan in the laser which would need to be switched off before exposure took
place. Once the exposure had been made the fan could be switched back on
again.
Does anyone know if this would be detrimental to the life of the laser, or
if there are likely to be any other problems caused by doing this. If it's
not a good idea at all please say so and i'll continue to use the laser off
the table. It's just that with having the laser off the table if I knock
the laser even slightly all the optics are knocked out of alignment. By
putting the laser on the table I can lock everything down so there is no
movement.
If it is possible to isolate the fan for a few minutes without damaging the
laser can this be done through the 'serial' type prot on the back of the
laser?
Many thanks
Jem
Samuel M. Goldwasser
Switching the fan(s) off for a few seconds or a minute won't hurt anything but
you must not forget to turn it back on! I once tested a setup like that
where the pump diode had died. I don't know if lack of cooling was the
cause though.
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Lostgallifreyan
news:ur5rb1...@repairfaq.org:
> "Jem" <Email not accepted> writes:
>
>> Hi all
>>
>> I have a Coherent 532-200 Ring Laser which I use for holography.
>>
>> I accquired a nice optical table and was thinking of mounting the
>> laser directly on to the table. The problem with this is that there
>> is a cooling fan in the laser which would need to be switched off
>> before exposure took place. Once the exposure had been made the fan
>> could be switched back on again.
>>
>> Does anyone know if this would be detrimental to the life of the
>> laser, or if there are likely to be any other problems caused by doing
>> this. If it's not a good idea at all please say so and i'll continue
>> to use the laser off the table. It's just that with having the laser
>> off the table if I knock the laser even slightly all the optics are
>> knocked out of alignment. By putting the laser on the table I can
>> lock everything down so there is no movement.
>>
>> If it is possible to isolate the fan for a few minutes without
>> damaging the laser can this be done through the 'serial' type prot on
>> the back of the laser?
>
> Switching the fan(s) off for a few seconds or a minute won't hurt
> anything but you must not forget to turn it back on! I once tested a
> setup like that where the pump diode had died. I don't know if lack of
> cooling was the cause though.
>
This sounds like a case for a simple monostable and transistor as switch, so
you can push the button to trigger the monostable to shut off the fan, then
after a few tens of seconds it starts up again automatically. The circuit
would be a standard found in most basic guides to electronics practise
(ideally centred on a 555 IC perhaps), and what's nice about it is the only
mod needed to the laser is a small round hole for a pushbutton, and the
insertion of the circuit into the fan's power line, the circuit being powered
from that same line. You wouldn't even need to mount a bioard that small, it
could just hang on the wire, or on the back of the pushbutton, so long as you
can avoid it touching things it shouldn't.
Jem
"Samuel M. Goldwasser" <s...@repairfaq.org> wrote in message
news:ur5rb1...@repairfaq.org...
Thanks Sam
I was kinda thinking of incorporating a switch into my timer circuit to kill
the fan a minute before the exposure and switch it back on again immediately
afterwards (most exposures are <1minute). Do you know if there is a pinout
for fan control on the 'serial' port on the back of the laser?, if not i'll
have to remove the lid and tap directly into the fan circuit.
Thanks
Jem
Samuel M. Goldwasser
There should be a jumper from pin 5 to pin 9 on the HD15
connector. Removing that will turn off the fans.
It can be an open collector TTL or a relay.
DougD
>"Jem" <Email not accepted> writes:
>
>> Hi all
>>
>> I have a Coherent 532-200 Ring Laser which I use for holography.
>>
>> I accquired a nice optical table and was thinking of mounting the
>> laser directly on to the table. The problem with this is that there
>> is a cooling fan in the laser which would need to be switched off
>> before exposure took place. Once the exposure had been made the fan
>> could be switched back on again.
>>
>> Does anyone know if this would be detrimental to the life of the
>> laser, or if there are likely to be any other problems caused by doing
>> this. If it's not a good idea at all please say so and i'll continue
>> to use the laser off the table. It's just that with having the laser
>> off the table if I knock the laser even slightly all the optics are
>> knocked out of alignment. By putting the laser on the table I can
>> lock everything down so there is no movement.
>>
>> If it is possible to isolate the fan for a few minutes without
>> damaging the laser can this be done through the 'serial' type prot on
>> the back of the laser?
>
>Switching the fan(s) off for a few seconds or a minute won't hurt anything but
>you must not forget to turn it back on! I once tested a setup like that
>where the pump diode had died. I don't know if lack of cooling was the
>cause though.
I would maybe be a bit concerned about even a small shift in temperature
at a time when you need the laser to be it's most stable.. I don't know
anything about this type of laser, but I can tell you of some of the extreme's
I've had to go through to temp stabablize etalon/cavity combo's on ion's,
the last thing I would consider doing would be to change the temp!!!
If I was stuck with a fan cooled laser and had a true rigid table and
mount system, I'd be inclined to first really nail that laser down to the
table top, and then setup a interferometer to actually see how
bad the contributions from the fan were, and consider using an
active fringe stabilizer instead if I couldn't damp out any fan noise..
just sayin'..
d.
Jem
"DougD" <m...@here.com> wrote in message
news:Y_idnefR5vRftITW...@supernews.com...
Thanks Sam, Doug & Doc :-)
Indeed there is a jumper from pin 5 to 9, that makes things nice and easy
for isolating the fan. What I may try first is mounting the laser on the
table using some vibration isolating mounts, and as you suggest Doug, i'll
set up an interferometer to test the results. I understand exactly what
you're saying about thermal stability.
Not sure i'll need an external circuit as my timer unit should be able to
take care of all the necessary switching ;-)
Thanks for your help guys, much appreciated.
Jem
Samuel M. Goldwasser
FYI, the fan(s) cool two things: The power electronics heatsink and
the laser diode TEC heatsink.
The electronics won't care as long as they don't overheat.
The TEC will take care of 99+ percent of the temperature regulation
of the pump diode. If the pump diode temperature changes, that will
translate into a slight increase or decrease in pump power. The
usual effect is then to shift the lasing wavelength by a very tiny amount
in addition to changing the output power. But this can happen by itself
on any of these lasers. The C532 should keep the mode referenced to the
Nd gain curve.
Jem
Thanks Sam, i'll bear that in mind.
Cheers
Jem
Lostgallifreyan
news:ueina1...@repairfaq.org:
> The TEC will take care of 99+ percent of the temperature regulation
> of the pump diode. If the pump diode temperature changes, that will
> translate into a slight increase or decrease in pump power. The
> usual effect is then to shift the lasing wavelength by a very tiny amount
> in addition to changing the output power. But this can happen by itself
> on any of these lasers. The C532 should keep the mode referenced to the
> Nd gain curve.
>
I think your earlier post was right (not that this isn't), air cooling is not
a 'stiff' reference, it would be like relying on a couple of 100 K resistors
as a voltage divider for a split rail supply without an op-amp voltage
follower to make the reference solid.
I don't know those lasers, but I suspect they don't scrimp on the aluminium
in the heatsink. So the question would only be one of how long it takes for
the temperature to drift beyond the TEC regulators ability to keep up with
it. If the laser was designed to cope with the sharp changes if someone
opened a lab door on a cold day, then it should be fine for the minute or two
you suggested. Hopefully the designers trusted that fan only with the right
purpose of removing heat, not with regulation of any kind beyond that of
keeping the main system in safe limits. If it really takes even 1% of the
regulation load off the TEC system once the temperature is in range,
something's wrong.
Jem
"Lostgallifreyan" <no-...@nowhere.net> wrote in message
news:Xns9CD8339EEF2...@216.196.109.145...
Yeah, i'm kinda hopeful for the small amount of time I need it to be
switched off it's not going to make much difference. I have a sensitive
thermocouple here along with a nice temp readout. I'll stick that on the
heatsink and see if I can measure anything. However, I expect the changes
will be very small and they may not register. I'm not sure how much of a
drift in temp will make a difference to the stability of the laser. Are we
talking 1000ths, 100ths, 10ths, or whole degrees before stability is
affected?
On another note... How are you keeping Doc?, hope life's treating you a
little better :-)
Take care
Jem
Lostgallifreyan
news:ZZudndphBq3spIfW...@pipex.net:
> Yeah, i'm kinda hopeful for the small amount of time I need it to be
> switched off it's not going to make much difference. I have a sensitive
> thermocouple here along with a nice temp readout. I'll stick that on
> the heatsink and see if I can measure anything. However, I expect the
> changes will be very small and they may not register. I'm not sure how
> much of a drift in temp will make a difference to the stability of the
> laser. Are we talking 1000ths, 100ths, 10ths, or whole degrees before
> stability is affected?
>
Which side? If the air-cooled side, then several degrees, probably. 'Room
temperature' is never expected to be strictly controlled. if you have the
maker's specs, they probably tell what ambient range is acceptable. So long
as the sink never falls out of range, the onky other question is how fast it
changes temperature, and I imagine the heatsink is built heavily enough that
there is NO way it can change fast enough when only coupled to flowing air,
even if the sink is at one extreme of ambient range and the air at the other.
:) Cheap DPSS lasers might fail such a test (hence the insistence that they
be mounted on a solid baseplate) but I doubt that a self-contained unit from
Coherent will suffer from that kind of weakness.
> On another note... How are you keeping Doc?, hope life's treating you a
> little better :-)
>
> Take care
>
> Jem
>
>
Thankyou. :) Not too bad. Running 5 miles a day and too weary for a great
deal else, making the most of it while I still have it. Might look into PL
though, as I am thinking of selling some lasers. I just stopped using them,
started maing GPS loggers and software to process and display info, and maybe
getting into shortwave listening. I just found that working with lasers
stopped being exciting for me (I know, blasphemy, but such is life..). I
still have hopes of completing a laser driver design for 200 KHz analog mod
that models fine in LTspice, based on an LM317. Most people say no way that
fast, but LTspice says yes, and a crude early construction seems to bear that
out. But it just doesn't happen, I think it's depression, I don't feel bad or
anything I just kind of really don't care so it doesn't happen. Nothing I've
seen motivates me enough to continue, or evidently I would do it. It's not
even that hard, I got far enough already, just don't feel like following
through somehow. Maybe just impending middle age. I kind of feel that no-one
would give a damn even if I DO finish the thing, so really, it might actually
not happen now. Certainly no point trying to convince devotees of Pangolin et
al that I have the slightest jot or tittle to offer of any interest
whatsoever. But just maybe I might still be able to sell the two green DPSS
lasers I still have. I never use them now. Got several PBS cubes that no-one
wants, and soem red diodes, too. Several tiny but efficient TEC's as well. I
had big plans, but I just ran aground, and don't want to do them now.
Jem
The GPS stuff sounds interesting, shame about the lasers though. I'm still
well and truly bitten by the bug that makes me addicted to coherent light.
I love making holograms, still find them absolutely fascinating. I just
need to improve my methods though, but it's a slow process as I lack time,
space and stability. Nevertheless, i've never lost the passion :-)
Also, I still have my RGB laser projector. Again, this facinates me,
there's just something about the beams and the colours. I sit and watch
lasers shows just for fun. A complete waste of time, but it helps me to
unwind ;-)
It would be good to see you over on PL again, even if it's just to sell a
few items. I, and i'm sure many others, really miss your input.
All the very best, take care.
Jem
Lostgallifreyan
Thankyou. I don't think I have much to add there though, I never really did
much. Most of those people are pros who wouldn't notice me if I came, spent 6
months, then vanished again. I might take the time to put together some pics
and detailed info on some stuff that might be worth selling though. beats
eBay, which I haven't sold anythign on for over a year now, since they
changed so much I couldn't keep up with it.
Jem, if you use GPS for any kind of slow track stuff, the kind it's not
normally rated to be accurate for, (walking, running, short-distance
sailing), let me know if you can use somethign to display a log and let you
select start and end points to get stats for the track. I'll send you the
program so you can try it. (You'd need wxLua to run it, but that's a neat
painless system, and also very good to make tools with for people who aren't
dedicated programmers versed in C and C++. My GPS thing can give you an idea
of some of its capabilities, it has a lot. If someone figures out realtime
sound output for it, it could be used to code laser show software because
it's easy and fast).
Jem
Thanks
Can't really say I have much use for GPS, well, outside of the car anyway.
Sounds like a good program though.
I think you greatly underestimate your input on PL. I, and i'm sure many
others, always felt you had valuable things to contribute. You're far more
intelligent than i'll ever be, and I learned an awful lot from your posts as
i'm sure did many others.
Anyway, keep smiling :-)
Jem