Photon counting for the masses

[George Herold]

Photon counting for the masses.

Last Friday on SEB someone asked about the reverse bias voltages
for LEDs. So I thought I’d try and measure it.
It turned out to be very interesting. The red LEDs that I pulled out
of a drawer are (I think) GaP (Newark #01H9629) from AND
optoelectronics. (AND114-R) (I reported a different part number
Friday, but that appears to be a mistake.)
When reversed biased near 24 V they show big (~100-500mV) RC
‘spikes’ that remind me of low power ~20 Zeners. When biased just
below the ‘avalanche knee’ the RC spikes are photo sensitive, with a
rate that looks proportional to the light intensity. They show every
indication of responding to individual photons, albeit at an extremely
low efficiency. (I don’t know of another photon counting system that
can operate in room light levels.)
So I’m wondering if anyone has heard of such behavior? I tried some
other leds and none show the effect. Is GaP ‘special’ in some way?
If anyone wants a couple of these LEDs to look at drop me an email
with name and address and I’ll stick a few in the mail.

George H.

[spamtrap1888]

The absolute maximum rating for reverse bias for these parts is 5V.
Could you have damaged the LED by driving it to 24V reverse bias?
Could this damage account for the behavior you see, or do you see the
same thing with LEDs right off the bat?

[George Herold]

> same thing with LEDs right off the bat?- Hide quoted text -
>
> - Show quoted text -

Yup, right away... I've got 100k ohm in series with the diode and
monitor the voltage across the resistor. (so not that much power to
hurt the LED). I was counting "room light" photons all day Friday.
Count was fairly stable at 4.5 kHz, for several hours. I tried
different LEDs from the same batch.. same thing (slightly different
Vr)

I don't 'get' the 5 volt number. I tried some other LEDs and couldn't
get them to break down at 50 volts! (that was the limit of the PS I
had on hand.)

George H.

[tm]

"George Herold" <ghe...@teachspin.com> wrote in message
news:53c4e5b0-2cb3-4857...@w7g2000vbg.googlegroups.com...

________________________________-

Do you have access to a curve tracer? If not, you can send me a few and I'll
put them on my 577.


TM

[John Larkin]

I'm not sure you're counting single photons, especially if you're
using room light. It could be some other effect.



--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators
Custom timing and laser controllers
Photonics and fiberoptic TTL data links
VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[John S]

I can't reproduce your photon findings with a red LED I have here. I
detect no reverse current through the LED at 50V reverse bias with the
scope set on 20mV/div. There is some noise present, but nothing like you
describe.

What sweep rate and vertical sensitivity are you using? Digital or
analog scope?

John S

[George Herold]

> John S- Hide quoted text -

>
> - Show quoted text -

Hi John, Digital scope, here are some ‘scope shots.

24.3 V reverse bias x10 scope probe across 100k ohm series resistor.
(C probe ~16pF RC time is mostly 100k ohm and probe)

This first is with 1 second persistence

http://bayimg.com/iAOEoaaDf

Here’s a shot of one pulse
http://bayimg.com/jaoEaaaDf

And the same thing with 1 sec persistence again

http://bayimg.com/jAoEBaADf


I think you need a GaP LED to see this. I saw nothing on the other
LEDs that I tried. Send me an address and I’ll stick a few in the
mail.

George H.


I was just reading that GaP is an indirect semiconductor, and it's
doped with something to use it as an LED.

[George Herold]

On Apr 30, 12:25 pm, "tm" <No_one_h...@white-house.gov> wrote:
> "George Herold" <gher...@teachspin.com> wrote in message

> TM- Hide quoted text -

>
> - Show quoted text -

Thanks TM, no curve tracer here. But I can do an I-V 'by hand'.
Does a curve tracer tell me anything else?

George H.

[George Herold]

On Apr 30, 12:29 pm, John Larkin

<jjlar...@highNOTlandTHIStechnologyPART.com> wrote:
> On Mon, 30 Apr 2012 08:01:09 -0700 (PDT), George Herold
>
>
>
>
>
> <gher...@teachspin.com> wrote:
> >Photon counting for the masses.
>
> >    Last Friday on SEB someone asked about the reverse bias voltages
> >for LEDs.  So I thought I’d try and measure it.
> >It turned out to be very interesting.   The red LEDs that I pulled out
> >of a drawer are (I think) GaP (Newark #01H9629) from AND
> >optoelectronics.  (AND114-R) (I reported a different part number
> >Friday, but that appears to be a mistake.)
> >    When reversed biased near 24 V they show big (~100-500mV) RC
> >‘spikes’ that remind me of low power ~20 Zeners.  When biased just
> >below the ‘avalanche knee’ the RC spikes are photo sensitive, with a
> >rate that looks proportional to the light intensity.  They show every
> >indication of responding to individual photons, albeit at an extremely
> >low efficiency.  (I don’t know of another photon counting system that
> >can operate in room light levels.)
> >  So I’m wondering if anyone has heard of such behavior?  I tried some
> >other leds and none show the effect.  Is GaP ‘special’ in some way?
> >If anyone wants a couple of these LEDs to look at drop me an email
> >with name and address and I’ll stick a few in the mail.
>
> >George H.
>
> I'm not sure you're counting single photons, especially if you're
> using room light. It could be some other effect.

Seems weird to me too! The count rate is linear with the intensity.
(as well as I can measure it.) So what else could it be?

Want a few?
(It's best to see things for yourself)
I do wish someone else would dig up a GaP LED and try.

George H.

>
> --
>
> John Larkin                  Highland Technology Incwww.highlandtechnology.com  jlarkin at highlandtechnology dot com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom timing and laser controllers
> Photonics and fiberoptic TTL data links
> VME  analog, thermocouple, LVDT, synchro, tachometer

> Multichannel arbitrary waveform generators- Hide quoted text -

[John S]

Ok. My LEDs just are not worthy. But, I'll leave the research to you.
Thanks for the offer.

Still, interesting to note that 50V isn't enough to cause reverse
current. Thanks for that tidbit.

John S

[John S]

Well, okay, I relent. I'll try to verify your findings.

Send to:

John Smith
1717 Laurel Ln
Plano, Tx 75074

[Jan Panteltje]

On a sunny day (Mon, 30 Apr 2012 11:07:11 -0700 (PDT)) it happened George
Herold <ghe...@teachspin.com> wrote in
<e006a0f1-fa9a-43b8...@q13g2000vbd.googlegroups.com>:

>>
>> I'm not sure you're counting single photons, especially if you're
>> using room light. It could be some other effect.
>
>Seems weird to me too! The count rate is linear with the intensity.
>(as well as I can measure it.) So what else could it be?

Seems like those diodes that have 'geiger' mode, those
breakdown when biased just below some voltage when hit by radiation.
Does it also do that with a Thorium or other radioactive source as trigger?
And those dides are very expensive, so hold on to those LEDs :-)
What is the null (dark) affect, background radiation + cosmic pulses?

[John S]

On 4/30/2012 1:01 PM, George Herold wrote:

Why do you have negative-going spikes? What does your schematic look like?

John S

[George Herold]

On Apr 30, 3:04 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
> On a sunny day (Mon, 30 Apr 2012 11:07:11 -0700 (PDT)) it happened George

> Herold <gher...@teachspin.com> wrote in
> <e006a0f1-fa9a-43b8-be6c-1d8ea57c2...@q13g2000vbd.googlegroups.com>:

>
>
>
> >> I'm not sure you're counting single photons, especially if you're
> >> using room light. It could be some other effect.
>
> >Seems weird to me too!  The count rate is linear with the intensity.
> >(as well as I can measure it.)  So what else could it be?
>
> Seems like those diodes that have 'geiger' mode, those
> breakdown when biased just below some voltage when hit by radiation.
> Does it also do that with a Thorium or other radioactive source as trigger?
> And those dides are very expensive, so hold on to those LEDs :-)
> What is the null (dark) affect, background radiation + cosmic pulses?

Hi Jan, I don't have any radioactive sources lying around.

In the dark I see no pulses. (Room lights off a little black foam
thing over the LED)

Expensive? I think they cost us $0.07 each.

George H.

Hey I found this paper which at least talks about optical gain in GaP
LEDs.
http://een.iust.ac.ir/profs/Sadr/Papers/omd7.4.pdf

Maybe I should search for "Geiger mode"

G

[George Herold]

Oh, well I was sending them into a little amp I have... to go on into
a counter (50 ohm Z in). And the amp is inverting, the counter wants
postive going pulses... the supply is floating, and I just have
polarities switched around to make it come out the 'right' way in the
end.

George H.

[George Herold]

> Plano, Tx  75074- Hide quoted text -

>
> - Show quoted text -

OK some are in the mail. (The one with the 100k ohm resistor attached
made the pics I posted... guaranteed to work.)

George

[John S]

Thanks. I'll try to duplicate your findings.

John S

[spamtrap1888]

The data sheet says it's a 700nm GaP device. Somewhere one should be
able to find more technical data on GaP red LEDs: a cross section,
what substrate it's grown on, lattice mismatch if any, and a bunch
more stuff

[tm]

"George Herold" <ghe...@teachspin.com> wrote in message

news:8a697e31-d5e3-4941...@z2g2000vba.googlegroups.com...

_______________________-

For a diode, no. Just easier to control the voltage and current. That plus I
can go to 1600 volts.

Also, it will show all four quadrants in one display.

FWIW.

TM

[Tom Del Rosso]

George Herold wrote:
> Photon counting for the masses.

Eyes are said to be able to detect single photons. It's enormously
egalitarian that most of the masses have 2 of them. :)


--

Reply in group, but if emailing add one more
zero, and remove the last word.

[John Larkin]

Don't know.

The thing to do would be to put the detector in a dark box with an
LED, and pulse the LED. The optical path would have to be such that
you'd expect, say, 0.1 photons to hit the detector per pulse. Then
analyze the statistics.

Just had this weird thought: connect two leds in parallel. Expose one
to light. The other one should light up. The efficiency might be low.

>
>Want a few?
>(It's best to see things for yourself)

Thanks, but I really don't have time right now.

--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom laser drivers and controllers

Photonics and fiberoptic TTL data links

VME thermocouple, LVDT, synchro acquisition and simulation

[Adrian Jansen]

I would suggest you do a rough calculation to see how many 'room light'
photons are likely to intersect the LED chip per second. I suspect it
might be a few more than 5000.

--
Regards,

Adrian Jansen adrianjansen at internode dot on dot net
Note reply address is invalid, convert address above to machine form.

[Martin Riddle]

"John Larkin" <jjla...@highNOTlandTHIStechnologyPART.com> wrote in
message news:9cftp7d6n5cdvu173...@4ax.com...

> On Mon, 30 Apr 2012 08:01:09 -0700 (PDT), George Herold
> <ghe...@teachspin.com> wrote:
>
>>Photon counting for the masses.
>>
>> Last Friday on SEB someone asked about the reverse bias voltages
>>for LEDs. So I thought I’d try and measure it.
>>It turned out to be very interesting. The red LEDs that I pulled out
>>of a drawer are (I think) GaP (Newark #01H9629) from AND
>>optoelectronics. (AND114-R) (I reported a different part number
>>Friday, but that appears to be a mistake.)
>> When reversed biased near 24 V they show big (~100-500mV) RC
>>‘spikes’ that remind me of low power ~20 Zeners. When biased just
>>below the ‘avalanche knee’ the RC spikes are photo sensitive, with a
>>rate that looks proportional to the light intensity. They show every
>>indication of responding to individual photons, albeit at an extremely
>>low efficiency. (I don’t know of another photon counting system that
>>can operate in room light levels.)
>> So I’m wondering if anyone has heard of such behavior? I tried some
>>other leds and none show the effect. Is GaP ‘special’ in some way?
>>If anyone wants a couple of these LEDs to look at drop me an email
>>with name and address and I’ll stick a few in the mail.
>>
>>George H.
>
> I'm not sure you're counting single photons, especially if you're
> using room light. It could be some other effect.
>
>

Setup a candle. But from the scope traces, it sure looks like something.

Cheers

[George Herold]

On Apr 30, 5:50 pm, John Larkin <jlar...@highlandtechnology.com>
wrote:

Well I do have a source of single photons, but they are random. Is
that OK.
(light bulb at low voltage, through green interference filter.)
But linear is enough for me... If it takes two photons, then it should
go as intensity squared.

The dark count is low... but there also appears to be some
hysteresis in the avalanche voltage...
after it photo-conducts it keeps dribbling on, if you set it near the
edge.

>
> Just had this weird thought: connect two leds in parallel. Expose one
> to light. The other one should light up. The efficiency might be low.

I think I saw that the GaP leds have poor effeiciency.

>
>
>
> >Want a few?
> >(It's best to see things for yourself)
>
> Thanks, but I really don't have time right now.

That I understand.

How 'bout this,

A follower to drive a cable to 50 ohm counter.

+V bias--+---+
| |
LED--> ^ |
- |
| |/
+--|
|\>
+------cable---+
| |
1k Ohm 50 Ohm
| |
+--------------+
GND GND

Well, I need something else between the 1k ohm and cable.
Maybe use a darlington?

George H.

>
> --
>
> John Larkin         Highland Technology, Inc
>

> jlarkin at highlandtechnology dot comhttp://www.highlandtechnology.com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom laser drivers and controllers
> Photonics and fiberoptic TTL data links

> VME thermocouple, LVDT, synchro   acquisition and simulation- Hide quoted text -

[George Herold]

On Apr 30, 6:38 pm, Adrian Jansen <adr...@qq.vv.net> wrote:
> On 1/5/2012 2:25 AM, tm wrote:
>
>
>
>
>

> > "George Herold" <gher...@teachspin.com> wrote in message

> Note reply address is invalid, convert address above to machine form.- Hide quoted text -

>
> - Show quoted text -

Hi Adrian, you most likely weren't following the thread on SEB.
The 'gain' is a strong function of the bias voltage. At 24 Volts I
get zero counts in room light,
at 24.5 Volts I get ~400 counts, at 24.9 I get 4k counts, at 25 volts
it starts to avalanche with no light.

I'm not sure how to think about the very low efficiency. I've heard
talk about single 'channels' in the avalanche process. So the 'right'
area, might be a channel area? (whatever that means)

George H.

[Jamie]

I am trying to see how you plan to have that work?

The ASCII art is confusing in terms of the LED orientation. One way
it looks like your operating it as a PV mode, which that will only yield
up to what ever the forward break down of the LED is, in which
case, you have to over come the one diode drop in the Base-Emitter.

If your intention is avalanche mode, then, you still need enough to
get over the one diode drop at the base, which you can do this however,
by the time you have enough photons in that LED, it then looks like a
high band of noise or, if any noise at all other than a slight ripple of DC?

To keep things at a simple level, you could use a JFET with a drain
bias R that has a trimmer in it to adjust the knee threshold to pinch it
in the off state. The LED would then be able to trigger it at the gate.
JFETS have low charge at their gates so this may work well.

I would suggest a 2N7000 type MOSFET however, I don't think the base
capacitance (charge) is going to allow for the 1 uA average current of
the LED to remove the charge fast enough to give you a response that
would be usable?

You must consider the time constants of charge verses what the diode
will be able to deliver to over come that. Going by memory, I don't
think there is enough area to produce the current required as a real PV
cell would generate.

Then of course, we could always select a JFET front end amp. A BiMos I
think they call them. TL081 or something of that order as a comparator.

Jamie

[Phil Hobbs]

Tom Del Rosso wrote:
>
> George Herold wrote:
> > Photon counting for the masses.
>
> Eyes are said to be able to detect single photons. It's enormously
> egalitarian that most of the masses have 2 of them. :)
>

The best I've heard of is bursts of 30 or so photons in the blue.

Cheers

Phil Hobbs

--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

[Tim Williams]

"George Herold" <ghe...@teachspin.com> wrote in message

news:f6446728-7966-4b47...@r32g2000yqj.googlegroups.com...

> I'm not sure how to think about the very low efficiency. I've heard
> talk about single 'channels' in the avalanche process. So the 'right'
> area, might be a channel area? (whatever that means)

Avalanche is dominated by impurities. A transition metal atom acts to
'short circuit' the bandgap, generating leakage current (and seeding
avalanche events), trapping charge carriers (acting as recombination
centers*), and putting a bump in the electric field (acting to worsen
avalanche in the local area).

*Hence the use of gold doping in some high-speed devices, including the
2N2369 and 7400 TTL logic series. It reduces both the breakdown voltage and
storage time. (I don't know for sure what TTL would've operated at without
gold doping, but contemporary processes were doing 30V in NPN bipolar
(LM741, etc.), and 15-18V (CD4000 series) in metal-gate CMOS. TTL breaks
down at 7V.)

Possible the effect the OP describes is due to a small photosensitive
impurity in the crystal. LEDs may generally have low leakage, but it's an
uncontrolled amount (they only spec them to 5V!), so it shouldn't be
surprising there may be poor behavior, like strong avalanche amplification
regions, or photosensitivity (or both), etc.

Tim

--
Deep Friar: a very philosophical monk.
Website: http://webpages.charter.net/dawill/tmoranwms

[Robert Baer]

George Herold wrote:
> Photon counting for the masses.
>

> Last Friday on SEB someone asked about the reverse bias voltages
> for LEDs. So I thought I’d try and measure it.
> It turned out to be very interesting. The red LEDs that I pulled out
> of a drawer are (I think) GaP (Newark #01H9629) from AND
> optoelectronics. (AND114-R) (I reported a different part number
> Friday, but that appears to be a mistake.)
> When reversed biased near 24 V they show big (~100-500mV) RC
> ‘spikes’ that remind me of low power ~20 Zeners. When biased just
> below the ‘avalanche knee’ the RC spikes are photo sensitive, with a
> rate that looks proportional to the light intensity. They show every
> indication of responding to individual photons, albeit at an extremely
> low efficiency. (I don’t know of another photon counting system that
> can operate in room light levels.)
> So I’m wondering if anyone has heard of such behavior? I tried some
> other leds and none show the effect. Is GaP ‘special’ in some way?
> If anyone wants a couple of these LEDs to look at drop me an email
> with name and address and I’ll stick a few in the mail.
>
> George H.

What you report is rather interesting.
So, assuming they are indeed responding to individual photons, is
there an estimate to "efficiency" like one of 10^20 photons are detected?

[Jan Panteltje]

On a sunny day (Mon, 30 Apr 2012 12:41:33 -0700 (PDT)) it happened George
Herold <ghe...@teachspin.com> wrote in
<1add734e-bcc3-4d28...@dc2g2000vbb.googlegroups.com>:

>On Apr 30, 3:04 pm, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
>> On a sunny day (Mon, 30 Apr 2012 11:07:11 -0700 (PDT)) it happened George
>> Herold <gher...@teachspin.com> wrote in
>> <e006a0f1-fa9a-43b8-be6c-1d8ea57c2...@q13g2000vbd.googlegroups.com>:
>>
>>
>>
>> >> I'm not sure you're counting single photons, especially if you're
>> >> using room light. It could be some other effect.
>>
>> >Seems weird to me too!  The count rate is linear with the intensity.
>> >(as well as I can measure it.)  So what else could it be?
>>
>> Seems like those diodes that have 'geiger' mode, those
>> breakdown when biased just below some voltage when hit by radiation.

>> Does it also do that with a Thorium or other radioactive source as trigge=

>r?
>> And those dides are very expensive, so hold on to those LEDs :-)
>> What is the null (dark) affect, background radiation + cosmic pulses?
>
>Hi Jan, I don't have any radioactive sources lying around.
>
>In the dark I see no pulses. (Room lights off a little black foam
>thing over the LED)
>
>Expensive? I think they cost us $0.07 each.
>
>George H.
>
>Hey I found this paper which at least talks about optical gain in GaP
>LEDs.
>http://een.iust.ac.ir/profs/Sadr/Papers/omd7.4.pdf

Very nice paper, the voltages seem really high, like 130V +
From the spectral curve it seems they are only sensitive to 'light'.
That would not stop me from testing them with some radioactive material however.
You can order Thorium containing welding rods on ebay that are a lot safer
to handle than those gass light mantles, the welding rods contain about 2% Th IIRC,
and give several times background on a GM counter,
But as you see no background at all.... n x 0 = 0.

>Maybe I should search for "Geiger mode"

Phil knows all about those diodes.

>G
>

[George Herold]

On Apr 30, 9:37 pm, Jamie

> Jamie- Hide quoted text -

>
> - Show quoted text -

Hi Jamie, (Say I thought for sure you'd like a few of these LED's.)

The circuit was just a late night thing. The LED is reverse biased.
I origianlly drew up a follower.
Maybe like this,

+V bias--+---+
| |
LED--> ^ |
- |
| |/
+--|
| |\>

100k-> R +------cable---+
| | |
bias-> V 1k Ohm 50 Ohm
diode - | |
+--- +--------------+
GND GND

But then I thought it was a waste to use most of the electrons
in the 100 k resistor.... so I cut it out. (I'll give it a try)
(and hang my head in shame when it doesn't work.)

George H.

[George Herold]

On Apr 30, 11:19 pm, "Tim Williams" <tmoran...@gmail.com> wrote:
> "George Herold" <gher...@teachspin.com> wrote in message

Thanks Tim, What's different about the above LED (and also low power
~20V zeners) is that it looks like the whole device discharges at
once. You get a big spike of charge, then the whole thing recharges
for another blast.

"(they only spec them to 5V!), " Yeah that's just strange. Most of
the LED's I tried I couldn't see any leakage (at the ~10nA level) for
voltages up to 50V.

George H.

[George Herold]

> there an estimate to "efficiency" like one of 10^20 photons are detected?- Hide quoted text -

>
> - Show quoted text -

What's the area of an LED? I don't have a good idea for this number.
I also have to take the lens into account. Then there's the unknown
spectral response. But on Friday I did some comparisons between a
photodiode and LED. I could do some handwavy upper bound from those
numbers. So with a yellow LED shinning on a PD and then the reversed
biased LED I generated 25uA of current in the PD and 2500 counts/
second in the LED. (that's 4x10-16 'equivalent amps'... so yeah an
effeciency of at least 10^-10. :^)

The photodiode has an area of 16mm^2.

What is more fun is the 'gain' of the LED. If the total charge
delivered is C*V (~10pF, 100mV) then a gain of 10^7. It's like a PMT,
but with no 'messy' high voltage.

George H.

[George Herold]

On May 1, 4:50 am, Jan Panteltje <pNaonStpealm...@yahoo.com> wrote:
> On a sunny day (Mon, 30 Apr 2012 12:41:33 -0700 (PDT)) it happened George

> Herold <gher...@teachspin.com> wrote in
> <1add734e-bcc3-4d28-92dd-c46a5e7a7...@dc2g2000vbb.googlegroups.com>:

> >G- Hide quoted text -
>
> - Show quoted text -- Hide quoted text -

>
> - Show quoted text -

I was reading in Sze (2nd edition page 101) about the breakdown
voltage in GaP versus the impurity concentration. (They have to dope
GaP to make it an LED.) at 10^17/cm^3 the break down is near 25 volts
and climbs to over 100 at 10^16. So I'm guessing different doping
levels.

That paper also talks about hysteresis effects.

George H.

[John Larkin]

You could use the LED itself as a photodiode, at a lower
non-avalanching voltage. That would roughly calibrate the photon rate
hitting the junction.

I'm guessing you aren't detecting single photons to any meaningful
extent.

[John Larkin]

On Mon, 30 Apr 2012 22:25:03 -0400, Phil Hobbs
<pcdhSpamM...@electrooptical.net> wrote:

>Tom Del Rosso wrote:
>>
>> George Herold wrote:
>> > Photon counting for the masses.
>>
>> Eyes are said to be able to detect single photons. It's enormously
>> egalitarian that most of the masses have 2 of them. :)
>>
>
>
>The best I've heard of is bursts of 30 or so photons in the blue.
>
>Cheers
>
>Phil Hobbs

Rods apparently respond to single photons, but a cluster of rods must
be hit to be perceptible.

http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html

Cool stuff.

I wonder why we don't respond to fewer or single photons. It would
seem to be useful.

As I've noted, I was able to detect the light from a green LED at
about 700 pA DC current. The LED was emitting, very roughly, something
like a million photons per second. My retina was probably getting 1%
of them, poorly focussed into a fuzzy blob.

[John Fields]

On Tue, 01 May 2012 12:02:08 -0700, John Larkin
<jla...@highlandtechnology.com> wrote:


>Rods apparently respond to single photons, but a cluster of rods must
>be hit to be perceptible.
>
>http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
>
>Cool stuff.
>
>I wonder why we don't respond to fewer or single photons. It would
>seem to be useful.

---
The fourth sentence from your link reads: " If we could consciously
see single photons we would experience too much visual "noise" in very
low light, so this filter is a necessary adaptation, not a weakness."

Also, if instead of a single photon triggering a reactive response
from a single rod, several photons from the same source impinging on a
group of rods did, then directional information could be gleaned from
the beam/flash.

Why else, if you see something out of the corner of your eye, do you
swing around to see where it's coming from?

--
JF

[John Larkin]

On Tue, 01 May 2012 17:26:39 -0500, John Fields
<jfi...@austininstruments.com> wrote:

>On Tue, 01 May 2012 12:02:08 -0700, John Larkin
><jla...@highlandtechnology.com> wrote:
>
>
>>Rods apparently respond to single photons, but a cluster of rods must
>>be hit to be perceptible.
>>
>>http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
>>
>>Cool stuff.
>>
>>I wonder why we don't respond to fewer or single photons. It would
>>seem to be useful.
>
>---
>The fourth sentence from your link reads: " If we could consciously
>see single photons we would experience too much visual "noise" in very
>low light, so this filter is a necessary adaptation, not a weakness."

I disagree with that. My night-vision intensifier lets me see stuff
that I can't see with my eyes, useful stuff. If I could resolve single
photons, I'm sure I could figure out where walls and doors and trees
and tigers were. Some nocturnal animals are reported to have
single-photon sensitivity.

>
>Also, if instead of a single photon triggering a reactive response
>from a single rod, several photons from the same source impinging on a
>group of rods did, then directional information could be gleaned from
>the beam/flash.

Why wouldn't you get directional information from a single photon?
What you would see would be a point-source flash of light, same as if
you saw a multi-photon flash.

The only drawback to single photon detection might be a high
background rate in total or near-total darkness, like when you were
asleep. I have that already, a high continuous phosphene rate, and it
doesn't disturb my sleep.

http://en.wikipedia.org/wiki/Phosphene

[Tim Williams]

"George Herold" <ghe...@teachspin.com> wrote in message

news:595eda2d-1281-4bf2...@d20g2000vbh.googlegroups.com...

> Thanks Tim, What's different about the above LED (and also low power
> ~20V zeners) is that it looks like the whole device discharges at
> once. You get a big spike of charge, then the whole thing recharges
> for another blast.

Not unusual for some regimes of avalanche -- 2N3904s reliably go from
reasonable open circuits (<mA leakage) to about 10 ohms in the span of <2ns
(probably under 1ns, but I only have a 200MHz scope to see it).

Though the 2N3904 is rated to 60V or so, actual breakdown is in the 80-110V
range. To achieve reliable avalanche, connect a 2.2k resistor B-E, and
apply voltage C-E through a low current source (usually 100VDC in series
with 10k ohms). Parallel capacitance (C-E) of a few pF helps generate a
visibly sized pulse.

Zener diodes, and intentional avalanche structures in general, are most
likely designed with load balancing in mind. This means either minimizing
impurities to an unusual degree, or ensuring their homogeneity throughout
the junction. Consider a garden variety zener diode: at low currents,
discrete avalanche is visible as short falling edges amid waves of rising
sawteeth (bias charging junction capacitance), but the important
characteristic is the falling edges are very short, fractional volts, and
the amplitude drops with increasing bias (basically mean value theorem in
action, noise is proportional to 1/sqrt(current)).

Surprisingly, to date one of the most accurate, low noise voltage references
remains the buried zener structure. By burying a junction inside the
silicon, surface states and dislocations are avoided. I forget if epitaxy
is used, or if it's formed entirely by diffusion; I seem to recall a few
etch and grow steps are required. This is important because epitaxy
deposits silicon randomly, leading to more dislocations, and can't be
annealed at the same temperature as the whole wafer to fix them (obviously,
that would ruin the doping underneath!). (It's my understanding, the
development of high speed power diodes was made possible by epitaxy: whereas
1N4001 is a simple diffused junction diode, the dislocations of an epitaxial
layer provide more recombination sites, reducing reverse recovery time -- at
the expense of greater voltage drop and junction resistance, I suppose due
to differences in doping profile (longer junction, higher built-in
potential?), necessitated by the lower critical field strength. Ultrafast
diodes even have additional dislocations induced by electron bombardment or
transition metal doping to achieve the best non-schottky speeds.)

> "(they only spec them to 5V!), " Yeah that's just strange. Most of
> the LED's I tried I couldn't see any leakage (at the ~10nA level) for
> voltages up to 50V.

How big are the actual spikes, and what fall time? You said you measured
through an amplifier, so perhaps the amplitude isn't much to begin with?

The risetime on the scope shots wasn't very impressive, likely due to slew
rate limiting. The actual performance of these phenomena can be very fast
indeed! (The next fastest phenomena are step recovery in specially doped
diodes, ranging from 300 down to 20ps or so, and all-out monolithic "shock
line" generators, usually implemented in long InP schottky junctions I think
($$$!). Anything less than that is optical domain -- femtosecond lasers and
such.)

[George Herold]

Hey, that's a good idea!

>
> I'm guessing you aren't detecting single photons to any meaningful
> extent.

Hmm, not sure what you mean by 'meaningful'. But I've got a few uses
for a random pulse generator. I've got count rates up above 10kHz,
but the pulse width is still 1-2uS. If I can get that down to 100ns
and 100kHz pulse rates. That would be wonderful.

A big pile of work today, and no time to play.

George H.

>
> --
>
> John Larkin         Highland Technology, Inc
>

> jlarkin at highlandtechnology dot comhttp://www.highlandtechnology.com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom laser drivers and controllers
> Photonics and fiberoptic TTL data links

> VME thermocouple, LVDT, synchro   acquisition and simulation- Hide quoted text -

[George Herold]

On May 2, 2:01 am, "Tim Williams" <tmoran...@gmail.com> wrote:
> "George Herold" <gher...@teachspin.com> wrote in message

>
> news:595eda2d-1281-4bf2...@d20g2000vbh.googlegroups.com...
>
> > Thanks Tim,  What's different about the above LED (and also low power
> > ~20V zeners) is that it looks like the whole device discharges at
> > once.  You get a big spike of charge, then the whole thing recharges
> > for another blast.
>
> Not unusual for some regimes of avalanche -- 2N3904s reliably go from
> reasonable open circuits (<mA leakage) to about 10 ohms in the span of <2ns
> (probably under 1ns, but I only have a 200MHz scope to see it).
>
> Though the 2N3904 is rated to 60V or so, actual breakdown is in the 80-110V
> range.  To achieve reliable avalanche, connect a 2.2k resistor B-E, and
> apply voltage C-E through a low current source (usually 100VDC in series
> with 10k ohms).  Parallel capacitance (C-E) of a few pF helps generate a
> visibly sized pulse.
>
> Zener diodes, and intentional avalanche structures in general, are most
> likely designed with load balancing in mind.  This means either minimizing
> impurities to an unusual degree, or ensuring their homogeneity throughout
> the junction.  Consider a garden variety zener diode: at low currents,
> discrete avalanche is visible as short falling edges amid waves of rising
> sawteeth (bias charging junction capacitance), but the important
> characteristic is the falling edges are very short, fractional volts, and
> the amplitude drops with increasing bias (basically mean value theorem in
> action, noise is proportional to 1/sqrt(current)).

Earlier this year I revisted zener diode noise, (zeners in the
avalanche range.. above 8 Volts.) The noise was very part dependent.
With maybe a factor of ten spread for one zener voltage. (My model
for this is that the breakdwon is happening in one little section of
the zener. There is some amount of charge 'stored' in that region,
and the pulse size is just how much charged is stored there, so
different devices have a different regions.. different pulse sizes.)
But with a 20V zener (1N5250) the pulse sizes (and noise) are pretty
much all the same. (less than 10% difference.) My modle for this is
that the whole device breaks down when it zeners, so I get a pulse
that is the capactiance of the device, which is pretty much the same
for all of them.

I'm guessing the pulse from the reversed biased LED are similar... the
whole LED is breaking down.

There's a nice article by K.G. McKay (Phys Rev. (94) 887 May 15, 1954)
about avalanche break down in Si.

>
> Surprisingly, to date one of the most accurate, low noise voltage references
> remains the buried zener structure.  By burying a junction inside the
> silicon, surface states and dislocations are avoided.  I forget if epitaxy
> is used, or if it's formed entirely by diffusion; I seem to recall a few
> etch and grow steps are required.  This is important because epitaxy
> deposits silicon randomly, leading to more dislocations, and can't be
> annealed at the same temperature as the whole wafer to fix them (obviously,
> that would ruin the doping underneath!).  (It's my understanding, the
> development of high speed power diodes was made possible by epitaxy: whereas
> 1N4001 is a simple diffused junction diode, the dislocations of an epitaxial
> layer provide more recombination sites, reducing reverse recovery time -- at
> the expense of greater voltage drop and junction resistance, I suppose due
> to differences in doping profile (longer junction, higher built-in
> potential?), necessitated by the lower critical field strength.  Ultrafast
> diodes even have additional dislocations induced by electron bombardment or
> transition metal doping to achieve the best non-schottky speeds.)
>
> > "(they only spec them to 5V!), "  Yeah that's just strange.  Most of
> > the LED's I tried I couldn't see any leakage (at the ~10nA level) for
> > voltages up to 50V.
>
> How big are the actual spikes, and what fall time?  You said you measured
> through an amplifier, so perhaps the amplitude isn't much to begin with?

Oh the pic's I posted were w/o any amp. (I needed an amp to drive the
50 ohm input of the counter.)

http://bayimg.com/jaoEaaaDf

The amplitude grows as the bias voltage gets closer to the avalanche
knee.
So sometimes even a volt or more.

>
> The risetime on the scope shots wasn't very impressive, likely due to slew
> rate limiting.  The actual performance of these phenomena can be very fast
> indeed!  (The next fastest phenomena are step recovery in specially doped
> diodes, ranging from 300 down to 20ps or so, and all-out monolithic "shock
> line" generators, usually implemented in long InP schottky junctions I think
> ($$$!).  Anything less than that is optical domain -- femtosecond lasers and
> such.)

Grin, the fall time is even worse. All done with a 40MHz 'scope,
though that doesn't appear to account for slow rise* time. I needed
the 100k ohm bias resistor, with a 10k ohm the pulses were sharper,
but of constant amplitude and sometimes longer pulse width. (I don't
have any idea why it is like that.)

George H.

(*Well my 'scope shots are inverted so by rise time I assume we are
both talking about the turn-on time.)

[Michael A. Terrell]

John Larkin wrote:

>
> John Fields wrote:
>
> >The fourth sentence from your link reads: " If we could consciously
> >see single photons we would experience too much visual "noise" in very
> >low light, so this filter is a necessary adaptation, not a weakness."
>
> I disagree with that. My night-vision intensifier lets me see stuff
> that I can't see with my eyes, useful stuff.

Doesn't that work mostly or completely in the IR range? The ones I
worked with only detected IR, which you can't see. Early '70s in the US
Army when they were being cold weather tested.


--
You can't have a sense of humor, if you have no sense.

[John Larkin]

Night-vision intensifiers can work in the visible and IR, and UV for
that matter; depends on the photocathode material. I have a cheap
ebay, probably Russian gen-1 unit, that does both. It does have an IR
illuminator. When it's on, I can see stuff 50 feet below in our
garden, like snakes and skunks and cats. Off, it amplifies scenes
illuminated by moonlight or night lights. I was playing with it last
night in a very dark room, with just a little street light leaking in
through windows. Under a desk I spotted Comet, our black cat, who was
invisible otherwise. (Our other cat is Ajax. Very clean cats, if
somewhat abrasive.)


--

John Larkin Highland Technology Inc
www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

VME analog, thermocouple, LVDT, synchro, tachometer
Multichannel arbitrary waveform generators

[John Larkin]

Mark Kahrs recently sent me this:

http://dl.dropbox.com/u/53724080/Circuits/6377480.pdf

--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom laser drivers and controllers

Photonics and fiberoptic TTL data links

[John Fields]

On Tue, 01 May 2012 15:50:51 -0700, John Larkin

<jla...@highlandtechnology.com> wrote:

>On Tue, 01 May 2012 17:26:39 -0500, John Fields
><jfi...@austininstruments.com> wrote:
>
>>On Tue, 01 May 2012 12:02:08 -0700, John Larkin
>><jla...@highlandtechnology.com> wrote:
>>
>>
>>>Rods apparently respond to single photons, but a cluster of rods must
>>>be hit to be perceptible.
>>>
>>>http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
>>>
>>>Cool stuff.
>>>
>>>I wonder why we don't respond to fewer or single photons. It would
>>>seem to be useful.
>>
>>---
>>The fourth sentence from your link reads: " If we could consciously
>>see single photons we would experience too much visual "noise" in very
>>low light, so this filter is a necessary adaptation, not a weakness."
>
>I disagree with that. My night-vision intensifier lets me see stuff
>that I can't see with my eyes, useful stuff.

---
Of course it does, and the reason it does is because it supplies your
eyes with many more photons than it - the intensifier - receives.

The price paid is the graininess in the images supplied to your eyes.
---

>If I could resolve single photons, I'm sure I could figure out where
>walls and doors and trees and tigers were.
>Some nocturnal animals are reported to have single-photon sensitivity.

---
As are we, but our brains integrate several single-photon events over
about 100 milliseconds before our brain allows us to consciously
recognize it as a flash.
---

>>Also, if instead of a single photon triggering a reactive response
>>from a single rod, several photons from the same source impinging on a
>>group of rods did, then directional information could be gleaned from
>>the beam/flash.
>
>Why wouldn't you get directional information from a single photon?

---
You would; my mistake.
---

>What you would see would be a point-source flash of light, same as if
>you saw a multi-photon flash.

---
Agreed.
---

>The only drawback to single photon detection might be a high
>background rate in total or near-total darkness, like when you were
>asleep. I have that already, a high continuous phosphene rate, and it
>doesn't disturb my sleep.
>
>http://en.wikipedia.org/wiki/Phosphene

---
The disturbance or lack of disturbance to your sleep isn't germane;
what is is being able to pick valid single-photon events from a high
background rate, as the fourth sentence from your:

http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html

link points out.

--
JF

[John Larkin]

On Wed, 02 May 2012 14:51:21 -0500, John Fields

Why would single photons be associated with "a high background rate"?

>
>link points out.
>

Well, I disagree. If you're trying to find your way around in the
dark, I can't see how being blind is better than having a noisy
single-photon-resolution image. There are animals with much better
night vision than we have, probably single-photon. And image
intensifiers can help one survive. Our rod cells apparently detect
single photons but they are neurologically filtered out. I wonder why.
There must be an evolutionary advantage or tradeoff somewhere, but I
can't imagine what it is.

[John Fields]

On Wed, 02 May 2012 13:21:08 -0700, John Larkin

>>link points out.

>>
>Why would single photons be associated with "a high background rate"?

---
A "high background rate" would represent noise, be it from phosphenes,
stray light, scintillation, or whatever, so in that sense
single-photon events would be associated with a high background rate
in that it would be more difficult to detect them than if the
background were quiet.
---

>Well, I disagree. If you're trying to find your way around in the
>dark, I can't see how being blind is better than having a noisy
>single-photon-resolution image.

---
The point is that if you can resolve single photons consciously, then
you might as well be blind if you can't tell the difference between
them and noise.
---

>There are animals with much better
>night vision than we have, probably single-photon.

---
And probably tuned to moonlight.
---

>And image intensifiers can help one survive.

---
Indeed, but hardly relevant to the discussion.
---

>Our rod cells apparently detect
>single photons but they are neurologically filtered out. I wonder why.

---
My guess would be that instead of waking the machine up with
trivialities, the grunts tally up enough similarly related events in a
given amount of time to warrant telling The Boss that something's up.
---

>There must be an evolutionary advantage or tradeoff somewhere, but I
>can't imagine what it is.

---
It's called "survival".

--
JF

[John Larkin]

On Wed, 02 May 2012 18:51:40 -0500, John Fields

If the tiger can see me, and I can't see the tiger, I don't survive.

[George Herold]

Neat, but where can I get a "Model 416 Lawn Genie Electronic Sprinkler
Timer"?

:^)

George H.

>
> --
>
> John Larkin         Highland Technology, Inc
>

> jlarkin at highlandtechnology dot comhttp://www.highlandtechnology.com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom laser drivers and controllers
> Photonics and fiberoptic TTL data links

> VME thermocouple, LVDT, synchro   acquisition and simulation- Hide quoted text -

[George Herold]

Maybe being too twitchy makes you neurotic. "Relax, it's only a
single photon, no need to worry till there's five or more."

A few beers serves the same purpose.

George H.

>
> --
>
> John Larkin         Highland Technology, Inc
>

> jlarkin at highlandtechnology dot comhttp://www.highlandtechnology.com

>
> Precision electronic instrumentation
> Picosecond-resolution Digital Delay and Pulse generators
> Custom laser drivers and controllers
> Photonics and fiberoptic TTL data links

[Les Cargill]

Beer - nature's low-pass filter.

> George H.
>>
>> --
>>
>> John Larkin Highland Technology, Inc
>>
>> jlarkin at highlandtechnology dot comhttp://www.highlandtechnology.com
>>
>> Precision electronic instrumentation
>> Picosecond-resolution Digital Delay and Pulse generators
>> Custom laser drivers and controllers
>> Photonics and fiberoptic TTL data links
>> VME thermocouple, LVDT, synchro acquisition and simulation- Hide quoted text -
>>
>> - Show quoted text -
>

--
Les Cargill

[John Larkin]

Another thing I like about San Francisco: there are practically no
lawns.

--

John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

[Chiron]

On Wed, 02 May 2012 13:21:08 -0700, John Larkin wrote:

<snip>

>
> Why would single photons be associated with "a high background rate"?
>
>
>>link points out.
>>
>>
> Well, I disagree. If you're trying to find your way around in the dark,
> I can't see how being blind is better than having a noisy
> single-photon-resolution image. There are animals with much better night
> vision than we have, probably single-photon. And image intensifiers can
> help one survive. Our rod cells apparently detect single photons but
> they are neurologically filtered out. I wonder why. There must be an
> evolutionary advantage or tradeoff somewhere, but I can't imagine what
> it is.

I'm not sure whether this is the case, but maybe it's because the nervous
system itself sends the occasional spurious signal? IIRC, neurons can
sometimes fire without being stimulated, just randomly. So the brain
would do well to filter out the occasional flash, even if some of those
flashes happened to be from actual photons. Something like the way
digital cameras account for "hot" CCD elements and filter them out.

Just a thought.


--
Brain off-line, please wait.

[Chiron]

On Wed, 02 May 2012 17:48:18 -0700, John Larkin wrote:

> If the tiger can see me, and I can't see the tiger, I don't survive.
>

Absolutely right. But if you're always seeing tigers when there aren't
any, you still don't survive because you don't get to eat.

This is (apparently) Nature's way of saying it's better to miss the
occasional tiger, than to see them all over the place.

--
When bad men combine, the good must associate; else they will fall one by
one, an unpitied sacrifice in a contemptible struggle.
-- Edmund Burke


--
Walk softly and carry a megawatt laser.

[Chiron]

On Wed, 02 May 2012 20:46:35 -0500, Les Cargill wrote:

> Beer - nature's low-pass filter.

Beer - because breakfast is your most important meal.



--
Slurm, n.:
The slime that accumulates on the underside of a soap bar when
it sits in the dish too long.
-- Rich Hall, "Sniglets"

[Jeroen Belleman]

Like in engineering: It's probably a compromise of some kind,
or may be we are stuck in a local optimum different from, say,
nocturnal animals.

We are diurnal animals. It's a choice evolution has made for
us at some point. Acute colour vision must have been a better
choice than raw sensitivity. We survive in daylight. At night
we can hide to survive.

Increasing the sensitivity of low-light vision certainly also
causes more false triggers. There is no point in adding gain
if it only gets you higher-amplitude noise. I also believe
that light is not a stream of photons. A 'photon' is merely
the amount of energy exchanged with an electromagnetic field
by its interaction with matter. The interactions are discrete
events, but the EM field isn't quantized.

Jeroen Belleman

[John Fields]

---
Precisely the reason most folks don't go prowling around in the jungle
at night. ;)

--
JF

[Jan Panteltje]

On a sunny day (Wed, 02 May 2012 17:48:18 -0700) it happened John Larkin
<jla...@highlandtechnology.com> wrote in
<icl3q713061q6t85l...@4ax.com>:

>If the tiger can see me, and I can't see the tiger, I don't survive.

That is total bull.
We have the ability to make tools, and live in houses
where at night the tiger cannot enter.

The tiger may see me on TV too, and me not the tiger, and
it would not worry me a bit, or through bullet proof glass,
or sitting on top of a tree, or a tree house,
or a car, or a plane or a balloon, use imagination
for more cases...

[Jan Panteltje]

On a sunny day (Thu, 03 May 2012 09:20:32 +0200) it happened Jeroen Belleman
<jer...@nospam.please> wrote in <jntbjv$25m$1...@speranza.aioe.org>:

>if it only gets you higher-amplitude noise. I also believe
>that light is not a stream of photons. A 'photon' is merely
>the amount of energy exchanged with an electromagnetic field
>by its interaction with matter. The interactions are discrete
>events, but the EM field isn't quantized.
>
>Jeroen Belleman

Exactly.

[Martin Brown]

On 01/05/2012 23:50, John Larkin wrote:
> On Tue, 01 May 2012 17:26:39 -0500, John Fields
> <jfi...@austininstruments.com> wrote:
>
>> On Tue, 01 May 2012 12:02:08 -0700, John Larkin
>> <jla...@highlandtechnology.com> wrote:
>>
>>
>>> Rods apparently respond to single photons, but a cluster of rods must
>>> be hit to be perceptible.
>>>
>>> http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
>>>
>>> Cool stuff.
>>>
>>> I wonder why we don't respond to fewer or single photons. It would
>>> seem to be useful.
>>
>> ---
>> The fourth sentence from your link reads: " If we could consciously
>> see single photons we would experience too much visual "noise" in very
>> low light, so this filter is a necessary adaptation, not a weakness."
>
> I disagree with that. My night-vision intensifier lets me see stuff
> that I can't see with my eyes, useful stuff. If I could resolve single
> photons, I'm sure I could figure out where walls and doors and trees

No. You would be swamped by the noise floor and a massive waste of
bandwidth that could be better used for peripheral motion detection.

The molecules in individual rods are sensitive to a single photons once
full dark adaptation is achieved and all the pigment is sensitive. The
figure of merit quoted is something between 1 and 10 photons to fire an
individual cell but to have the signal passed on to the brain takes
several adjacent rods to trigger. The eye's dynamic range is quoted as
10^9 and in some individuals 10^10. That is pretty good! You can
incidentally boost your eye sensitivity by breathing pure oxygen
especially at altitude but it isn't a good idea to do it for long.

Our high resolution fovea where the cones are located is 10x less
sensitive. All amateur astronomers know that to see the faintest objects
in total darkness you look to one side of them and jiggle slightly.
Averted vision will allow you to maximise vision in the dark.

> and tigers were. Some nocturnal animals are reported to have
> single-photon sensitivity.

But they pay for it in terms of resolution. Cats have asymmetric irises
to close tighter in strong light and retro-reflective structures at the
back of the eye so their retina gets two bites of the cherry.

The cats eye is about 6x more sensitive than a humans, but it is the
enhanced lateral resolution and motion detecting tricks that allow it to
home in on prey.

>> Also, if instead of a single photon triggering a reactive response
>>from a single rod, several photons from the same source impinging on a
>> group of rods did, then directional information could be gleaned from
>> the beam/flash.
>
> Why wouldn't you get directional information from a single photon?
> What you would see would be a point-source flash of light, same as if
> you saw a multi-photon flash.
>
> The only drawback to single photon detection might be a high
> background rate in total or near-total darkness, like when you were

We already have that approximately once you become properly dark adapted
- which takes about an hour or so with no white light at all and minimal
illumination of any kind. The quantum efficiency is a lot less than for
modern CCDs though but quite good for mere chemistry.

> asleep. I have that already, a high continuous phosphene rate, and it
> doesn't disturb my sleep.
>
> http://en.wikipedia.org/wiki/Phosphene

You only really find out what your background noise floor looks like
when you spend extended periods working in total darkness. These days
most city dwellers have never seen the milky way or experienced anything
even close to a dark night well away from light pollution.

--
Regards,
Martin Brown

[John Larkin]

On Thu, 03 May 2012 07:03:39 GMT, Chiron
<chiron613.no.spam.@no.spam.please.gmail.com> wrote:

>On Wed, 02 May 2012 17:48:18 -0700, John Larkin wrote:
>
>> If the tiger can see me, and I can't see the tiger, I don't survive.
>>
>
>Absolutely right. But if you're always seeing tigers when there aren't
>any, you still don't survive because you don't get to eat.
>
>This is (apparently) Nature's way of saying it's better to miss the
>occasional tiger, than to see them all over the place.

Does the tiger see goats all over the place? Does a gen-3 night vision
scope show illusory enemies? Single-photon imaging has low resolution,
but it is useful. I just wonder why we don't have it, when it's useful
and other critters do.

No.

--

John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

[Jan Panteltje]

On a sunny day (Thu, 03 May 2012 07:18:53 -0700) it happened John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote in
<cq45q795k6bbu0ekl...@4ax.com>:

>On Thu, 03 May 2012 07:03:39 GMT, Chiron
><chiron613.no.spam.@no.spam.please.gmail.com> wrote:
>
>>On Wed, 02 May 2012 17:48:18 -0700, John Larkin wrote:
>>
>>> If the tiger can see me, and I can't see the tiger, I don't survive.
>>>
>>
>>Absolutely right. But if you're always seeing tigers when there aren't
>>any, you still don't survive because you don't get to eat.
>>
>>This is (apparently) Nature's way of saying it's better to miss the
>>occasional tiger, than to see them all over the place.
>
>Does the tiger see goats all over the place? Does a gen-3 night vision
>scope show illusory enemies? Single-photon imaging has low resolution,
>but it is useful. I just wonder why we don't have it, when it's useful
>and other critters do.
>
>No.

'single photon' vision is complete bullocks.

Just as a hint, and I predicted that not so long ago,
some guys did light measurements on LEDs with super low current,
and found the efficiency was > 100%.

Some time before that I pointed out (sci.physics) that theoretically
due to thermal and other environmental effects, electrons
may just get enough kinetic energy so that they require less than Planck's
idea of energy to leave.
In the same way electron orbital changes can emit quanta of light when triggered
by less energy than your f*cking non existing photon.
Lets just say: disturbance of the ether.

In a living being, with high temperature, this effect must be huge.
This is totally contradictory to QM ideas of detectors needing to be at close to zero temperatures.
Next time I hear somebody use the word 'photon' I .... <censored>
But you WILL notice it :-)

[John Larkin]

On Thu, 03 May 2012 10:24:09 GMT, Jan Panteltje
<pNaonSt...@yahoo.com> wrote:

>On a sunny day (Wed, 02 May 2012 17:48:18 -0700) it happened John Larkin
><jla...@highlandtechnology.com> wrote in
><icl3q713061q6t85l...@4ax.com>:
>
>>If the tiger can see me, and I can't see the tiger, I don't survive.
>
>That is total bull.
>We have the ability to make tools, and live in houses
>where at night the tiger cannot enter.
>

It's true that people tend to cluster in groups at night for safety,
sing around the campfire and such. Even warfare, competition between
groups, is mostly conducted by daylight, at least was until radar and
night-vision devices were invented.

So, what is the evolutionary payoff? What about our visual system is
so improved that it's worth trading away night vision? People here
seem to be arguing that night vision is in itself useless or
detrimental, and that doesn't make sense.

Possibly high quality color vision is more useful to humans than raw
photon sensitivity, and they trade off.

--

John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

[John Larkin]

That's probably the tradeoff. Weapons, construction of shelter, fire,
socialization allow us to cluster and defend ourselves at night. So we
can fill our retinas with cones and improve our daytime color vision
and resolution at the expense of night vision. So we probably evolved
away our photon sensitivity fairlty recently, few hundred thousand
years maybe, as we became more human. I wonder if, to this day, some
groups around the world are different as ragards this tradeoff. After
all, most research is done on Western college students.

Still, single-photon sensitivity would be cool.

>
>Increasing the sensitivity of low-light vision certainly also
>causes more false triggers. There is no point in adding gain
>if it only gets you higher-amplitude noise. I also believe
>that light is not a stream of photons. A 'photon' is merely
>the amount of energy exchanged with an electromagnetic field
>by its interaction with matter. The interactions are discrete
>events, but the EM field isn't quantized.

You can certainly use a gen-3 image intensifier to see
photon-delineated scenes in near-total darkness. And those scenes are
sufficiently useful that police and the military pay big bucks for the
equipment. Light sure behaves as if it's made of discrete photons.

--

John Larkin Highland Technology Inc

www.highlandtechnology.com jlarkin at highlandtechnology dot com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom timing and laser controllers

Photonics and fiberoptic TTL data links

[John Larkin]

On Thu, 03 May 2012 11:38:18 +0100, Martin Brown
<|||newspam|||@nezumi.demon.co.uk> wrote:

>On 01/05/2012 23:50, John Larkin wrote:
>> On Tue, 01 May 2012 17:26:39 -0500, John Fields
>> <jfi...@austininstruments.com> wrote:
>>
>>> On Tue, 01 May 2012 12:02:08 -0700, John Larkin
>>> <jla...@highlandtechnology.com> wrote:
>>>
>>>
>>>> Rods apparently respond to single photons, but a cluster of rods must
>>>> be hit to be perceptible.
>>>>
>>>> http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
>>>>
>>>> Cool stuff.
>>>>
>>>> I wonder why we don't respond to fewer or single photons. It would
>>>> seem to be useful.
>>>
>>> ---
>>> The fourth sentence from your link reads: " If we could consciously
>>> see single photons we would experience too much visual "noise" in very
>>> low light, so this filter is a necessary adaptation, not a weakness."
>>
>> I disagree with that. My night-vision intensifier lets me see stuff
>> that I can't see with my eyes, useful stuff. If I could resolve single
>> photons, I'm sure I could figure out where walls and doors and trees
>
>No. You would be swamped by the noise floor and a massive waste of
>bandwidth that could be better used for peripheral motion detection.

Then why is there a market for night-vision intensifiers? Why can I
see a black cat under a desk in a dark room, with my cheap gen-1
Russian intensifier, that I can't see without it?

[Martin Brown]

On 03/05/2012 16:32, John Larkin wrote:
> On Thu, 03 May 2012 10:24:09 GMT, Jan Panteltje
> <pNaonSt...@yahoo.com> wrote:
>
>> On a sunny day (Wed, 02 May 2012 17:48:18 -0700) it happened John Larkin
>> <jla...@highlandtechnology.com> wrote in
>> <icl3q713061q6t85l...@4ax.com>:
>>
>>> If the tiger can see me, and I can't see the tiger, I don't survive.
>>
>> That is total bull.
>> We have the ability to make tools, and live in houses
>> where at night the tiger cannot enter.
>
> It's true that people tend to cluster in groups at night for safety,

Mainly because you can come badly unstuck moving around in darkness.

> sing around the campfire and such. Even warfare, competition between
> groups, is mostly conducted by daylight, at least was until radar and
> night-vision devices were invented.

Ninja and the like tended to use cover of darkness.

>
> So, what is the evolutionary payoff? What about our visual system is
> so improved that it's worth trading away night vision? People here

Motion detection - and our night vision is only inferior to the big cats
by about a factor of three on retinal sensitivity. They get an extra
factor of two from the mirror structure behind their retina (and have to
live with the quirks of an asymmetric point spread function from an
elongated iris - which allows greater mechanical adaptation).

> seem to be arguing that night vision is in itself useless or
> detrimental, and that doesn't make sense.

Yes it does. You don't want the brain overloaded with random shot noise
so the does local processing. The human vision threshold is pretty close
to the optimum for the eye. Our lateral vision is better at night than
looking straight ahead and the eye is optimised for spotting movement at
the edge of visual field even at low light levels.

In strong light the utility of the eye is reversed the cones give full
colour high resolution imaging but at a fraction of the sensitivity.

>
> Possibly high quality color vision is more useful to humans than raw
> photon sensitivity, and they trade off.

No. It is spotting movement either predator or prey in the visual field.
You have to tolerate some loss of absolute sensitivity to get reliable
detection of movement without too many false positives.

--
Regards,
Martin Brown

[Martin Brown]

On 03/05/2012 16:46, John Larkin wrote:
> On Thu, 03 May 2012 11:38:18 +0100, Martin Brown
> <|||newspam|||@nezumi.demon.co.uk> wrote:
>
>> On 01/05/2012 23:50, John Larkin wrote:
>>> On Tue, 01 May 2012 17:26:39 -0500, John Fields
>>> <jfi...@austininstruments.com> wrote:
>>>
>>>> On Tue, 01 May 2012 12:02:08 -0700, John Larkin
>>>> <jla...@highlandtechnology.com> wrote:
>>>>
>>>>
>>>>> Rods apparently respond to single photons, but a cluster of rods must
>>>>> be hit to be perceptible.
>>>>>
>>>>> http://math.ucr.edu/home/baez/physics/Quantum/see_a_photon.html
>>>>>
>>>>> Cool stuff.
>>>>>
>>>>> I wonder why we don't respond to fewer or single photons. It would
>>>>> seem to be useful.
>>>>
>>>> ---
>>>> The fourth sentence from your link reads: " If we could consciously
>>>> see single photons we would experience too much visual "noise" in very
>>>> low light, so this filter is a necessary adaptation, not a weakness."
>>>
>>> I disagree with that. My night-vision intensifier lets me see stuff
>>> that I can't see with my eyes, useful stuff. If I could resolve single
>>> photons, I'm sure I could figure out where walls and doors and trees
>>
>> No. You would be swamped by the noise floor and a massive waste of
>> bandwidth that could be better used for peripheral motion detection.
>
> Then why is there a market for night-vision intensifiers? Why can I

Because it extends the range of what we can do with the unaided eye. You
might just as well ask why we can't see in the thermal band IR - some
snakes can and it definitely helps them find warm blooded prey.

Humans evolved in an arms race with their preditors and prey. The eye we
ended up with is the one which on average maximises survival. Spotting
movement of something you can eat or is intending to eat you is actually
more valuable than absolute sensitivity.

> see a black cat under a desk in a dark room, with my cheap gen-1
> Russian intensifier, that I can't see without it?

I am surprised you can see anything useful though a gen-1 image
intensifier they almost all have huge background noise levels of
ghoulish green glow. Maybe modern gen-1 gear is better but I doubt it.
You would see things a lot better if you had the patience to become dark
adapted which takes more than an hour in near total darkness.

Image photon counting came of age in the late 1970's when a combination
of microchannel plates, video cameras and fast electronics were used to
make image photon counting detectors for astronomy at Imperial College
London - the technique still has a few niche uses even today!

http://www.ing.iac.es/Astronomy/observing/manuals/html_manuals/general/obs_guide/node221.html

--
Regards,
Martin Brown

[John Larkin]

On Thu, 03 May 2012 17:10:29 +0100, Martin Brown

My only patent (7,019,307), which I discovered accidentally some years
after it was issued, involves a microchannel plate stack and a 2-d
delay-line detector. This can resolve the X-Y-time of single ion or
photon hits on a surface. Most people hang a CCD after the MCP stack,
but electronically detecting every pulse in real time has uses. Makes
you almost want to believe in photons.

Just call me "et al"

[Phil Hobbs]

Interesting paper, thanks. I need to build a test gizmo to see how fast
I can turn off a LED by applying a honking reverse bias, and using an
avalanche transistor would be fun. I have a bunch of NOS metal-can
2N2369s that I've been wanting to try out for avalanching.

Cheers

Phil Hobbs

Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics

160 North State Road #203
Briarcliff Manor NY 10510
845-480-2058

hobbs at electrooptical dot net
http://electrooptical.net

[Chiron]

On Thu, 03 May 2012 07:18:53 -0700, John Larkin wrote:

> On Thu, 03 May 2012 07:03:39 GMT, Chiron
> <chiron613.no.spam.@no.spam.please.gmail.com> wrote:
>
>>On Wed, 02 May 2012 17:48:18 -0700, John Larkin wrote:
>>
>>> If the tiger can see me, and I can't see the tiger, I don't survive.
>>>
>>>
>>Absolutely right. But if you're always seeing tigers when there aren't
>>any, you still don't survive because you don't get to eat.
>>
>>This is (apparently) Nature's way of saying it's better to miss the
>>occasional tiger, than to see them all over the place.
>
> Does the tiger see goats all over the place? Does a gen-3 night vision
> scope show illusory enemies? Single-photon imaging has low resolution,
> but it is useful. I just wonder why we don't have it, when it's useful
> and other critters do.
>
> No.

Good point. It may be that tigers do better with "false positives." Or
perhaps they use other senses (smell, hearing) to confirm what their eyes
are seeing.

But, different animals, different dietary needs, different modes of
behavior, different diurnal cycle - different heredity. What works for
tigers may simply be useless or even a hindrance to us.

Back in the olden days, we slept at night and did our hunting, gathering,
farming, and other stuff during the day. AFAIK, this was a worldwide
phenomenon across all ancient peoples - and still is among those who lack
artificial lighting. I am unaware of any cultures that operated at
night, before the invention of artificial illumination. That being the
case, there wasn't a great need for night vision. We were sleeping.

Nocturnal creatures do need such enhancements. Some of these are
actually blind in ordinary daylight. Cats have versatile pupils that can
stop down enough to allow them to see. But at night they can open up
completely, and their reflective retinas add to their ability to see in
very low light.

But they hunt at night.

--
You have a massage (from the Swedish prime minister).

[Spehro Pefhany]

On Thu, 03 May 2012 08:32:48 -0700, John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote:

>On Thu, 03 May 2012 10:24:09 GMT, Jan Panteltje
><pNaonSt...@yahoo.com> wrote:
>
>>On a sunny day (Wed, 02 May 2012 17:48:18 -0700) it happened John Larkin
>><jla...@highlandtechnology.com> wrote in
>><icl3q713061q6t85l...@4ax.com>:
>>
>>>If the tiger can see me, and I can't see the tiger, I don't survive.
>>
>>That is total bull.
>>We have the ability to make tools, and live in houses
>>where at night the tiger cannot enter.
>>
>
>It's true that people tend to cluster in groups at night for safety,
>sing around the campfire and such. Even warfare, competition between
>groups, is mostly conducted by daylight, at least was until radar and
>night-vision devices were invented.
>
>So, what is the evolutionary payoff? What about our visual system is
>so improved that it's worth trading away night vision? People here
>seem to be arguing that night vision is in itself useless or
>detrimental, and that doesn't make sense.
>
>Possibly high quality color vision is more useful to humans than raw
>photon sensitivity, and they trade off.

A friend took a ton of photos in Kruger recently, and as he's a B&W
aficionado they were reproduced in B&W. Predators are a LOT better
camouflaged in monochrome. If that's the trade-off, I think I'll take
high-def color vision.

[John Larkin]

On Thu, 03 May 2012 14:31:30 GMT, Jan Panteltje
<pNaonSt...@yahoo.com> wrote:

>On a sunny day (Thu, 03 May 2012 07:18:53 -0700) it happened John Larkin
><jjla...@highNOTlandTHIStechnologyPART.com> wrote in
><cq45q795k6bbu0ekl...@4ax.com>:
>
>>On Thu, 03 May 2012 07:03:39 GMT, Chiron
>><chiron613.no.spam.@no.spam.please.gmail.com> wrote:
>>
>>>On Wed, 02 May 2012 17:48:18 -0700, John Larkin wrote:
>>>
>>>> If the tiger can see me, and I can't see the tiger, I don't survive.
>>>>
>>>
>>>Absolutely right. But if you're always seeing tigers when there aren't
>>>any, you still don't survive because you don't get to eat.
>>>
>>>This is (apparently) Nature's way of saying it's better to miss the
>>>occasional tiger, than to see them all over the place.
>>
>>Does the tiger see goats all over the place? Does a gen-3 night vision
>>scope show illusory enemies? Single-photon imaging has low resolution,
>>but it is useful. I just wonder why we don't have it, when it's useful
>>and other critters do.
>>
>>No.
>
>'single photon' vision is complete bullocks.
>
>Just as a hint, and I predicted that not so long ago,
>some guys did light measurements on LEDs with super low current,
>and found the efficiency was > 100%.

Over-unity, perpetual motion at last!

--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom laser drivers and controllers

Photonics and fiberoptic TTL data links

[John Larkin]

It certainly help for PCB layout.

--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom laser drivers and controllers

Photonics and fiberoptic TTL data links

[Phil Hobbs]

_Photodetection_ behaves as though light were discrete photons.
Essentially no other process does, at least not in the 0-5 eV range.
Even where the idea of photons helps the bookkeeping, e.g. in figuring
out the frequency shift in an acousto-optic cell, there are wave ways to
do the calculations.

Cheers

Phil Hobbs

--

[Tom Del Rosso]

Jeroen Belleman wrote:
>
> Increasing the sensitivity of low-light vision certainly also
> causes more false triggers. There is no point in adding gain
> if it only gets you higher-amplitude noise. I also believe
> that light is not a stream of photons. A 'photon' is merely
> the amount of energy exchanged with an electromagnetic field
> by its interaction with matter. The interactions are discrete
> events, but the EM field isn't quantized.

If wave-particle duality was that simple, they should have said so 100 years
ago.


--

Reply in group, but if emailing add one more
zero, and remove the last word.

[Jan Panteltje]

On a sunny day (Thu, 03 May 2012 08:32:48 -0700) it happened John Larkin
<jjla...@highNOTlandTHIStechnologyPART.com> wrote in
<kr85q79tq5tg89n6j...@4ax.com>:

>On Thu, 03 May 2012 10:24:09 GMT, Jan Panteltje
><pNaonSt...@yahoo.com> wrote:
>
>>On a sunny day (Wed, 02 May 2012 17:48:18 -0700) it happened John Larkin
>><jla...@highlandtechnology.com> wrote in
>><icl3q713061q6t85l...@4ax.com>:
>>
>>>If the tiger can see me, and I can't see the tiger, I don't survive.
>>
>>That is total bull.
>>We have the ability to make tools, and live in houses
>>where at night the tiger cannot enter.
>>
>
>It's true that people tend to cluster in groups at night for safety,
>sing around the campfire and such. Even warfare, competition between
>groups, is mostly conducted by daylight, at least was until radar and
>night-vision devices were invented.
>
>So, what is the evolutionary payoff? What about our visual system is
>so improved that it's worth trading away night vision? People here
>seem to be arguing that night vision is in itself useless or
>detrimental, and that doesn't make sense.
>
>Possibly high quality color vision is more useful to humans than raw
>photon sensitivity, and they trade off.

Our ability to make tools (that can, among other things, make us see at night)
helps us survive.
I agree with you that the ability to see at night is important to
some extent, for example for warfare or perhaps even hunting.

I do not see any conflict in that, last week I did read some article
on more and more 'bionic', oops, no it was a German science TV program,
limbs coming, some better than our original limbs from flesh and blood
as far as performance in some fields is concerned (they showed this
runner who had 2 artificial legs, he was excluded from the Olympics
because he was faster with his artificial legs).
So maybe in a couple of hundred or thousand years we will be half man
and half machine.
They also showed somebody with a chip implant that generated a feeling of happiness...
Where does it go? Sure if we evolve and learn to make these things
we will become a very different looking 'species'.
But is not that what evolution was doing in the first place?
Creating ever different species, adapted to ever different environments.
Maybe we will travel space that way, as a brain supported by machines,
And then at one point transfer our awareness to a sort of electronic
or chemical or quantum stuff net.
Would be interesting to time warp a thousand years ahead.
It is also possible that we do not make it and dinos are our example.

[Jan Panteltje]

On a sunny day (Thu, 03 May 2012 11:22:57 -0700) it happened John Larkin
<jla...@highlandtechnology.com> wrote in
<t5j5q7luet6hv551b...@4ax.com>:

>On Thu, 03 May 2012 14:31:30 GMT, Jan Panteltje
><pNaonSt...@yahoo.com> wrote:
>
>>On a sunny day (Thu, 03 May 2012 07:18:53 -0700) it happened John Larkin
>><jjla...@highNOTlandTHIStechnologyPART.com> wrote in
>><cq45q795k6bbu0ekl...@4ax.com>:
>>
>>>On Thu, 03 May 2012 07:03:39 GMT, Chiron
>>><chiron613.no.spam.@no.spam.please.gmail.com> wrote:
>>>
>>>>On Wed, 02 May 2012 17:48:18 -0700, John Larkin wrote:
>>>>
>>>>> If the tiger can see me, and I can't see the tiger, I don't survive.
>>>>>
>>>>
>>>>Absolutely right. But if you're always seeing tigers when there aren't
>>>>any, you still don't survive because you don't get to eat.
>>>>
>>>>This is (apparently) Nature's way of saying it's better to miss the
>>>>occasional tiger, than to see them all over the place.
>>>
>>>Does the tiger see goats all over the place? Does a gen-3 night vision
>>>scope show illusory enemies? Single-photon imaging has low resolution,
>>>but it is useful. I just wonder why we don't have it, when it's useful
>>>and other critters do.
>>>
>>>No.
>>
>>'single photon' vision is complete bullocks.
>>
>>Just as a hint, and I predicted that not so long ago,
>>some guys did light measurements on LEDs with super low current,
>>and found the efficiency was > 100%.
>
>Over-unity, perpetual motion at last!

Well, you have google, of COURSE it was not really >100%, but the light
output was > then the electric energy put in at those low elves.
I think the article is at physicsworld.com:
http://physicsworld.com/cws/article/news/2012/mar/08/led-converts-heat-into-light

If you google sci.phycis you can see I predicted it, those guys tested it.
And this works both ways.

[John Larkin]

On Thu, 03 May 2012 19:16:27 GMT, Jan Panteltje

Heck, if I heat an LED to 135C, I can get it to emit infrared energy
with no electrical input.

[George Herold]

On May 3, 2:36 pm, Phil Hobbs <pcdhSpamMeSensel...@electrooptical.net>
wrote:

> John Larkin wrote:
>
> > On Thu, 03 May 2012 09:20:32 +0200, Jeroen Belleman
> > <jer...@nospam.please> wrote:
>
> > >On 2012-05-02 22:21, John Larkin wrote:
> > >> On Wed, 02 May 2012 14:51:21 -0500, John Fields

> > >> <jfie...@austininstruments.com>  wrote:

>
> > >>> On Tue, 01 May 2012 15:50:51 -0700, John Larkin

> > >>> <jlar...@highlandtechnology.com>  wrote:

>
> > >>>> On Tue, 01 May 2012 17:26:39 -0500, John Fields

> > >>>> <jfie...@austininstruments.com>  wrote:

>
> > >>>>> On Tue, 01 May 2012 12:02:08 -0700, John Larkin

> > >>>>> <jlar...@highlandtechnology.com>  wrote:

How else do we know about E&M radiation if not by detection?
I thought the heralded photon experiments pretty much required the
'photon' picture. "There's this much energy at this wavelength at it
will arrive at your detector at this time." Still you need a
detector.

George H.
(agnostic when it comes to the existence or non-existence of photons)

>
> --
> Dr Philip C D Hobbs
> Principal Consultant
> ElectroOptical Innovations LLC
> Optics, Electro-optics, Photonics, Analog Electronics
>
> 160 North State Road #203
> Briarcliff Manor NY 10510
> 845-480-2058
>

> hobbs at electrooptical dot nethttp://electrooptical.net- Hide quoted text -
>
> - Show quoted text -

[Phil Hobbs]

That's exactly right. But when people talk about light being "made up"
of photons, it assumes two things that aren't true:

1. a photon is a thing like an electron or a billiard ball
2. a photon has a definite location.

If you start thinking of little billiard balls bouncing around, you
_never_ get the right answer.

Cheers

Phil Hobbs

[John Larkin]

Light energy is certainly quantized; see Einstein, 1905. Monochromatic
light is made up of a measurable number of packets, each an
indivisible amount of energy. Attenuation and partial reflection don't
change the energy or the wavelength of these bundles, so we may as
well call them photons. Their *location* is different; one photon is
sort of all over the place until it's detected.

Photons are extremely considerate: they are particles when you want
them to be, and they are waves when you want them to be. Who can gripe
about something so helpful?

--

John Larkin Highland Technology, Inc

jlarkin at highlandtechnology dot com

http://www.highlandtechnology.com

Precision electronic instrumentation
Picosecond-resolution Digital Delay and Pulse generators

Custom laser drivers and controllers

Photonics and fiberoptic TTL data links

[Tim Williams]

"Chiron" <chiron613.no.spam.@no.spam.please.gmail.com> wrote in message
news:f5qor.78123$YM2....@newsfe05.iad...

>> If the tiger can see me, and I can't see the tiger, I don't survive.
>
> Absolutely right. But if you're always seeing tigers when there aren't
> any, you still don't survive because you don't get to eat.
>
> This is (apparently) Nature's way of saying it's better to miss the
> occasional tiger, than to see them all over the place.

Yeah, but I can clearly tell the difference between noise, or phosphenes, or
graininess, or whatever I'd get with low level visibility, and a tiger.
That's what brains are for. Brains are excellent pattern matching machines.
Easy to tell if it's a false positive, sit and wait and see if the pattern
changes over time. Move your head to see if it follows the field of view
("stuck pixels", or more likely with biological sight, dead spots). If
you're a concerned prey item, you'll probably be watching intently anyway to
see if it moves. And if it moves, one way or another, you're going to be
running your ass off. Better to be able to tell if it's anything at all,
let alone if it's moving.

Something that may've been forgotten: biology does an edge detect (spacial
and temporal derivative) in the eye, then reconstructs the image later.
This works well for spotting sharp changes, and it works particularly well
for tracking motion. Every time a photon appears, the derivative with
respect to time and space results in a magnified blotch of change, which
worsens the noise at high frequencies -- in essence, it goes from white
noise to blue noise. But again, these components are easily filtered by
biological processes (integration) or simply concentrating on them (same
idea, higher level).

More pertinent comparisons might include birds. Do any birds ever hunt at
night? Birds are renouned for their excellent eyesight, several times
sharper than humans', and color is definitely a requirement, but if they
also have poor night vision, that would be another part of the story. There
are a number of oceanic species with large eyes, the largest being the giant
squid's. Size is mainly for receiving any light at all (equivalent to the
Super Kamiokande's array of PMTs); I don't know if anyone has studied its
resolution.

Certainly, structures like the reflective retinal layer worsen resolution,
so there is necessarily some tradeoff in ability. Large eyes also take up
more space (the human head shields its moderate sized eyes within orbits of
bone, big eyes would require huge caveman brows and cheekbones to maintain
cover).

[John S]

On 5/3/2012 6:38 PM, Tim Williams wrote:

> More pertinent comparisons might include birds. Do any birds ever hunt
> at night? Birds are renouned for their excellent eyesight, several times
> sharper than humans', and color is definitely a requirement, but if they
> also have poor night vision, that would be another part of the story.

Owls. Not only is their night vision excellent, they have hearing that
can pinpoint a scurrying mouse beneath a layer of snow.

John S

[John Fields]

---
The same would be true if you cooked one of your toes, but what does
that have to do with the discussion?

--
JF

[k...@att.bizzzzzzzzzzzz]

On Thu, 03 May 2012 07:05:11 GMT, Chiron
<chiron613.no.spam.@no.spam.please.gmail.com> wrote:

>On Wed, 02 May 2012 20:46:35 -0500, Les Cargill wrote:
>
>> Beer - nature's low-pass filter.
>
>Beer - because breakfast is your most important meal.

Beer and Wheaties - The Breakfast of Ex-Champions

[Tom Del Rosso]

Tim Williams wrote:
>
> Something that may've been forgotten: biology does an edge detect
> (spacial and temporal derivative) in the eye, then reconstructs the
> image later. This works well for spotting sharp changes, and it works
> particularly well for tracking motion. Every time a photon appears,
> the derivative with respect to time and space results in a magnified
> blotch of change, which worsens the noise at high frequencies -- in
> essence, it goes from white noise to blue noise. But again, these
> components are easily filtered by biological processes (integration)
> or simply concentrating on them (same idea, higher level).

As I remember it, edge detection is a product of motion detection, rather
than the other way around. Our eyes vibrate slightly so that, combined with
motion detection, edges are highlighted.

That's just from old reading about neural nets, so it's not directly from
biology texts.

[Tom Del Rosso]

John Belushi's Olympic training routine started with mini chocolate donuts.

[Jan Panteltje]

On a sunny day (Thu, 03 May 2012 12:44:30 -0700) it happened John Larkin
<jla...@highlandtechnology.com> wrote in
<6qn5q71imcttelnmr...@4ax.com>:

>>output was > then the electric energy put in at those low elves.
>>I think the article is at physicsworld.com:
>> http://physicsworld.com/cws/article/news/2012/mar/08/led-converts-heat-into-light
>>
>>If you google sci.phycis you can see I predicted it, those guys tested it.
>>And this works both ways.
>
>Heck, if I heat an LED to 135C, I can get it to emit infrared energy
>with no electrical input.

Yes, the thought occured to me if they looked in the proper frequency bands,
or what filters they used.
But it was done at an US lab...

[Jan Panteltje]

On a sunny day (Thu, 03 May 2012 15:44:05 -0700) it happened John Larkin
<jla...@highlandtechnology.com> wrote in
<nr16q7lrog3uvptgr...@4ax.com>:

>>
>>1. a photon is a thing like an electron or a billiard ball
>>2. a photon has a definite location.
>>
>>If you start thinking of little billiard balls bouncing around, you
>>_never_ get the right answer.
>>
>>Cheers
>>
>>Phil Hobbs
>
>Light energy is certainly quantized; see Einstein, 1905. Monochromatic
>light is made up of a measurable number of packets, each an
>indivisible amount of energy.

No.
little EM wave disturbances when an electron changes orbit can
best be seen as ripples in a pond where a stone is dropped.

You will notice the ripples move in all (now 2 D) directions.
Of course the pressure wave moves in ALL directions.
A lower amplitude than <given some mass and size, say energy for the 'stone'>
is possible when 'light' (EM wave) is generated in a different way.
Not even to mention the superposition of all the stuff.


Just an idea, would moving a quark create an EM disturbance?
LOL

In short, all effects seen can be explained from the wave perspective,
including the photo-electric effect.
Not all effects seen can be explained from the particle perspective,
you get a crazy picture that way.

This Einstein fella has caused more confusion than he ever solved.
And people keep parroting that, thinking it makes them look 'learned'.
I prefer the term 'brain dead', voila[1] our education system.

[l]Freely translated in the context: 'Welcome to'

[Bob Masta]

On Fri, 4 May 2012 00:53:40 -0400, "Tom Del Rosso"
<td...@verizon.net.invalid> wrote:

>As I remember it, edge detection is a product of motion detection, rather
>than the other way around. Our eyes vibrate slightly so that, combined with
>motion detection, edges are highlighted.
>
>That's just from old reading about neural nets, so it's not directly from
>biology texts.

Edge detection in the eye doesn't require motion. Receptors
have inhibitory connections on their neighbors ("inhibitory
surrounds"). This increases contrast, so the edges stand
out.

What you may be thinking of is that if the image on the
retina is stationary, it fades away due to adaptation of the
receptors and their subsequent neurons... they are
essentially "AC coupled".

As far as I know, all sensory systems and most neurons in
general respond more strongly to stimulus onset, then adapt
to a lower firing level as the stimulus continues, or stop
completely. Some neurons also have a burst of offset
activity as well.

Best regards,



Bob Masta

DAQARTA v6.02
Data AcQuisition And Real-Time Analysis
www.daqarta.com
Scope, Spectrum, Spectrogram, Sound Level Meter
Frequency Counter, FREE Signal Generator
Pitch Track, Pitch-to-MIDI
Science with your sound card!

[Jan Panteltje]

I wrote:

>No.
>little EM wave disturbances when an electron changes orbit can
>best be seen as ripples in a pond where a stone is dropped.
>
>You will notice the ripples move in all (now 2 D) directions.
>Of course the pressure wave moves in ALL directions.
>A lower amplitude than <given some mass and size, say energy for the 'stone'>
>is possible when 'light' (EM wave) is generated in a different way.
>Not even to mention the superposition of all the stuff.

PS
Our 'wave detector' is very crude.
It basically consists of a rubber ball[1] glued to a piece of concrete[2],
embedded in the water, where the waves from the stone's entry travel.

When the wave amplitude at the point of the ball is so big that the glue breaks,
we catch the ball and cry: "A PHOTON IS DETECTED".

Even to the complete imbeciles it must be clear that the quantization
observed this way depends 100% on the detector (glue strength, etc), not on the wave.

[1] electron
[2] nucleus

[Bob Masta]

I have no quibble with the idea that light *can* be
quantized, but I wonder whether it *must* be quantized. All
of our common techniques for measuring light, and most of
those for emitting it, depend upon exciting electrons, so
we can expect the measurements to be quantized simply
because electron energy levels are quantized.

But for EM radiation in general, as far as I can tell, all
that is needed is accelerating charge. I confess that I'm
not smart enough to follow the math of synchrotron
radiation, but I imagine that a whirling charge doesn't say
to itself "Ooh, time to throw off a blue photon... no,
wait, I just did that... better make it green this time".

All of the "photon" discussions seem to fizzle as we get
down to radio frequencies. I understand that some folks
claim that microwaves are quantized, but as far as I can
tell they use resonant cavities in their tests. But lower
down, I don't recall ever hearing anybody discuss how a
continuous sinusoidal motion of electrons in an antenna can
give rise to discrete photons of RF. Where does one end and
the next begin? Instead we get hand-waving and mumbling
about "wave-particle duality", except I've never heard a
"particle" side to RF.

But I'd love to hear the explanation!

[George Herold]

Hi Bob,

I think it has to be "turtles all the way down". You can't have
quantized E&M (photons) at optical wavlengths and then say, "but not
at RF".

So here's a system where there are quantized energy states in the RF
region.
(I'm sure there are others.)

If you look at a magnetic moment (spin of the electron or nucleus) in
a magnetic field, you will find that quantum mechanically the
projection of the magnetic moment along the magnetic field direction
is quantized. It can only have certain values. Furthermore to change
from one state to the other (flip the spin for the case of a free
electron.) you need 'exactly' the right frequency of magnetic dipole
radiation. I will sometimes speak of an RF photon causing the spin to
change state. I don't think there is anything fundamentally wrong
with this statement. I guess you should always remember that all of
science is just a model for how nature works. There's nothing saying
that the model is what’s really going on.

George H.

>
> Best regards,
>
> Bob Masta
>
>               DAQARTA  v6.02
>    Data AcQuisition And Real-Time Analysis
>              www.daqarta.com
> Scope, Spectrum, Spectrogram, Sound Level Meter
>     Frequency Counter, FREE Signal Generator
>            Pitch Track, Pitch-to-MIDI

>           Science with your sound card!- Hide quoted text -

[Tom Del Rosso]

Jan Panteltje wrote:
>
> PS
> Our 'wave detector' is very crude.
> It basically consists of a rubber ball[1] glued to a piece of
> concrete[2],
> embedded in the water, where the waves from the stone's entry travel.
>
> When the wave amplitude at the point of the ball is so big that the
> glue breaks,
> we catch the ball and cry: "A PHOTON IS DETECTED".
>
> Even to the complete imbeciles it must be clear that the quantization
> observed this way depends 100% on the detector (glue strength, etc),
> not on the wave.
>
> [1] electron
> [2] nucleus

Einstein had detractors almost a century ago, and as I said, if
wave-particle duality was that simple, they should have said so.

It's not that I see a flaw in this viewpoint, but I would like to know that
some peer-reviewed source agreed with it.

[John Larkin]

On Fri, 04 May 2012 10:28:48 GMT, Jan Panteltje
<pNaonSt...@yahoo.com> wrote:

>On a sunny day (Thu, 03 May 2012 15:44:05 -0700) it happened John Larkin
><jla...@highlandtechnology.com> wrote in
><nr16q7lrog3uvptgr...@4ax.com>:
>
>>>
>>>1. a photon is a thing like an electron or a billiard ball
>>>2. a photon has a definite location.
>>>
>>>If you start thinking of little billiard balls bouncing around, you
>>>_never_ get the right answer.
>>>
>>>Cheers
>>>
>>>Phil Hobbs
>>
>>Light energy is certainly quantized; see Einstein, 1905. Monochromatic
>>light is made up of a measurable number of packets, each an
>>indivisible amount of energy.
>
>No.
>little EM wave disturbances when an electron changes orbit can
>best be seen as ripples in a pond where a stone is dropped.
>
>You will notice the ripples move in all (now 2 D) directions.

But photons move in one direction. That's why you have a shadow.

>Of course the pressure wave moves in ALL directions.

A gamma ray looks more like a particle than a wave. But all photons
are the same, just different energy levels. It's just more obvious
with gammas.

>A lower amplitude than <given some mass and size, say energy for the 'stone'>
>is possible when 'light' (EM wave) is generated in a different way.
>Not even to mention the superposition of all the stuff.
>
>
>Just an idea, would moving a quark create an EM disturbance?
>LOL
>
>In short, all effects seen can be explained from the wave perspective,
>including the photo-electric effect.
>Not all effects seen can be explained from the particle perspective,
>you get a crazy picture that way.
>
>This Einstein fella has caused more confusion than he ever solved.

He said a lot of new and radical stuff, and 100% has been right. He
regretted proposing the Cosmological Constant, but even that turned
out to be right.

[John Larkin]

On Fri, 04 May 2012 11:37:12 GMT, Jan Panteltje
<pNaonSt...@yahoo.com> wrote:

>I wrote:
>
>>No.
>>little EM wave disturbances when an electron changes orbit can
>>best be seen as ripples in a pond where a stone is dropped.
>>
>>You will notice the ripples move in all (now 2 D) directions.
>>Of course the pressure wave moves in ALL directions.
>>A lower amplitude than <given some mass and size, say energy for the 'stone'>
>>is possible when 'light' (EM wave) is generated in a different way.
>>Not even to mention the superposition of all the stuff.
>
>
>PS
>Our 'wave detector' is very crude.
>It basically consists of a rubber ball[1] glued to a piece of concrete[2],
>embedded in the water, where the waves from the stone's entry travel.
>
>When the wave amplitude at the point of the ball is so big that the glue breaks,
>we catch the ball and cry: "A PHOTON IS DETECTED".

Bad analogy. The rest of the water wave is still sloshing around the
pond after part of it breaks your glue. Some of it even reflects off
your detector. With a photon, once it's detected, all of it is gone,
everywhere. Even though its extent was miles (as interferance requires
it to be) it collapses instantly, and deposits 100% of its energy,
into the detector. Your pond ripples don't do that; they are divisible
and not quanta.

Face it: there is no humanly comprehensible explanation of quantum
mechanics.

[Jan Panteltje]

On a sunny day (Fri, 04 May 2012 11:34:11 -0700) it happened John Larkin
<jla...@highlandtechnology.com> wrote in
<ov78q7d6u1ejiac2n...@4ax.com>:

>>Of course the pressure wave moves in ALL directions.
>
>A gamma ray looks more like a particle than a wave. But all photons
>are the same, just different energy levels. It's just more obvious
>with gammas.

A 'photon' is just a mathematical construct: p=h.v
when h is Planck' constant, and v the frequency.

>>This Einstein fella has caused more confusion than he ever solved.
>
>He said a lot of new and radical stuff, and 100% has been right. He
>regretted proposing the Cosmological Constant, but even that turned
>out to be right.

He tried to replace understanding with a simple formula.
Physics has been stuck with it ever since, putting the breaks on any advancement.

Math is just an engineering tool, to get quantities.
understanding is possibly a construct in the human neural net that
encompasses much more.

The wormhole - , singularity - , and string fruitcakes are products of silly applications
(say wrong applications or applications to phantasy) of math, without ANY understanding.
For example any idiot knows everything has it limits, but mathematicians
playing Einstein's formulas gladly arrive at singularities, and those
sell bigtime in the world of phantasy, Hollywood makes lots of money
with their crap, just too bad when you ask for the wormhole travel ticket then they shy away,
Its the sickness of this time, : math - Einstein - CERN, ITER, LIGO.
Shortage of resources will fix that, I am very happy the gravity wave spacecraft was ditched
I heard today and replaced by a mission to the Jupiter moons.
NASA pulled out (no money) and Europe decided to only go to Jupiter.
Now that is interesting looking for life.
LIGO (the gravity wave detector) has had updates to improve its sensitivity by orders
of magnitudes, and still sees nothing, so much for Einstein's phantasy world.
Either that or they cannot even do basic math, as it should have shown a signal years
ago WITHOUT the sensitivity updates.
HAHAHA
Einstein should never have gotten a Nobel for 'photon', and some should not have gotten a Nobel piece price,
its all politics, and it destroys or puts the break on any scientific advancement.
Why do you think US cannot go to moon anymore, and now mars, but only drive
around the block using a Russian taxi? Politics.
Peer review? Like in global warming?
HAHAHA
Imagine a whole lot of Slow Mans with an agenda so thick that the trees cut to make the paper
for it heat the earth to the points of stone melting into lava.
Harvard (IIRC) just made the announcement that they will no longer subscribe to the 'peer reviewed'
journals, because they say 'We do the research and make it available for free, and then need to buy it back from the journals (that do the peer reviews'.
Now there is 2012, and it probably will get worse.

[Jan Panteltje]

On a sunny day (Fri, 04 May 2012 11:42:48 -0700) it happened John Larkin
<jla...@highlandtechnology.com> wrote in
<j988q7l80nis8kd76...@4ax.com>:

>On Fri, 04 May 2012 11:37:12 GMT, Jan Panteltje
><pNaonSt...@yahoo.com> wrote:
>
>>I wrote:
>>
>>>No.
>>>little EM wave disturbances when an electron changes orbit can
>>>best be seen as ripples in a pond where a stone is dropped.
>>>
>>>You will notice the ripples move in all (now 2 D) directions.
>>>Of course the pressure wave moves in ALL directions.
>>>A lower amplitude than <given some mass and size, say energy for the 'stone'>
>>>is possible when 'light' (EM wave) is generated in a different way.
>>>Not even to mention the superposition of all the stuff.
>>
>>
>>PS
>>Our 'wave detector' is very crude.
>>It basically consists of a rubber ball[1] glued to a piece of concrete[2],
>>embedded in the water, where the waves from the stone's entry travel.
>>
>>When the wave amplitude at the point of the ball is so big that the glue breaks,
>>we catch the ball and cry: "A PHOTON IS DETECTED".
>
>
>Bad analogy. The rest of the water wave is still sloshing around the
>pond after part of it breaks your glue. Some of it even reflects off
>your detector. With a photon, once it's detected, all of it is gone,

Not correct, only you ball detectors cannot see the now less amplitude waves anymore.

>everywhere. Even though its extent was miles (as interferance requires
>it to be) it collapses instantly, and deposits 100% of its energy,
>into the detector. Your pond ripples don't do that; they are divisible
>and not quanta.
>
>Face it: there is no humanly comprehensible explanation of quantum
>mechanics.

In my mind I often simply replace 'quantum' with 'probability'.

If you look up the Feynman lectures (videos are on the net) then that is
the way he explains things on that big blackboard.

Maybe some understanding now 'tunnels'.
LOL

[John S]

On 4/30/2012 2:52 PM, George Herold wrote:

>>
>>>>> Last Friday on SEB someone asked about the reverse bias voltages
>>>>> for LEDs. So I thought I’d try and measure it.
>>>>> It turned out to be very interesting. The red LEDs that I pulled out
>>>>> of a drawer are (I think) GaP (Newark #01H9629) from AND
>>>>> optoelectronics. (AND114-R) (I reported a different part number
>>>>> Friday, but that appears to be a mistake.)
>>>>> When reversed biased near 24 V they show big (~100-500mV) RC
>>>>> ‘spikes’ that remind me of low power ~20 Zeners. When biased just
>>>>> below the ‘avalanche knee’ the RC spikes are photo sensitive, with a
>>>>> rate that looks proportional to the light intensity. They show every
>>>>> indication of responding to individual photons, albeit at an extremely
>>>>> low efficiency. (I don’t know of another photon counting system that
>>>>> can operate in room light levels.)
>>>>> So I’m wondering if anyone has heard of such behavior? I tried some
>>>>> other leds and none show the effect. Is GaP ‘special’ in some way?
>>>>> If anyone wants a couple of these LEDs to look at drop me an email
>>>>> with name and address and I’ll stick a few in the mail.
>>
>>>>> George H.
>>

>
> OK some are in the mail. (The one with the 100k ohm resistor attached
> made the pics I posted... guaranteed to work.)
>
> George

Hi, George -

The LEDs arrived about 30 minutes ago. Thank you.

I promptly verified your observations with my own. I have not tried to
measure frequency of the pulses, but I agree that they are a function
light. However, there is a much stronger correlation to the applied
reverse voltage. There is a voltage which brings on these pulses even in
total darkness. Maybe it is counting cosmic rays that get through.

I'm not sure I know what to think of this.

Cheers,
John S

[Jeroen]

If you google around for Willis Lamb, you should be able to dig up
some writings that (seem to?) fulfill that last requirement.

Jeroen Belleman