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Interesting optical observations

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Conundrum

Sat Mar 24 2012, 08:56AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Hi all.
Is it just me, or can others here see infrared light from NIR LEDs?
Estimate these to be around 720nm or so, its hard to tell without a spectrometer.
Purchased on Ebay, but have confirmed the effect with one from a camcorder.

just did an experiment to confirm that the light I am seeing is indeed infrared.
used an IR filter from a webcam which as no effect at all on visible light,
and the "faint red glow" disappears.
Same effect with the IR blue tinted filter from a broken slide projector.

Any ideas? This is in room lighting, outdoors the effect is not noticeable.

It could be relevant to people who have dyslexia who use tinted glasses.
Perhaps they need to have an infrared filter as well?

Chris Russell

Sat Mar 24 2012, 09:51AM

... not Russel!
Registered Member #1 Joined: Thu Jan 26 2006, 12:18AM
Location: Tempe, Arizona
Posts: 1052

It's not just you. The human eye retains some sensitivity down to 750nm or so, and LEDs can have a fairly wide bandwidth. I can see a faint red glow from most of the IR devices in the house if I use them in total darkness.

Conundrum

Sat Mar 24 2012, 10:55AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

Interesting.
Wonder if thats why my eyes are sometimes painful outside on a very sunny day?
Glasses don't make any difference whatsoever.

-A

Inducktion

Sat Mar 24 2012, 05:23PM

Registered Member #3637 Joined: Fri Jan 21 2011, 11:07PM
Location: Buffalo, NY
Posts: 1068

Conundrum, everyone can see into near IR... I can see a slight red hue from a bunch of IR LED's I hooked together for a night vision camera.

Or for a green laser pointer, if it's cold you can see the non doubled 808 nm IR peek through too.

klugesmith

Sat Mar 24 2012, 06:21PM

Registered Member #2099 Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716

I'll add to those saying "Yup".

I worked in optical fiber datacomm during the transition from selected CD-player laser diodes at 780 nm, to VCSELs at 850 nm. The transmitted power, with fiber unplugged, is strictly limited by eye-safety standards. Max is around 1 mW, IIRC. In a broad cone, not a laser-pointer-like beam.

We could tell the difference between 780 nm Tx ports (red point visible in ordinary room light) and 850 nm Tx ports (red point visible in a pretty dark room). They both appeared as bright, but mis-focused, spots in digital camera images.

Not sure what wavelength is the official beginning in infrared. THe official CIE V_sub_lambda function is table-driven, with values every 5 nm from 380 to 780. The typical human biochemical respnse obviously has longer tails. Maybe there are some mutants among us with significantly different IR vision.

[edit] Couldn't readily find this online, but my old CRC handbook came through.
Standard observer "y bar" (relative visibility), unity at 555 millimicrons, is
first below 0.1 at 470 and 655
first below 0.01 at 425 and 690
first below 0.001 at 405 and 725
given as 0.0001 down to 385 and up to 760.

Proud Mary

Sat Mar 24 2012, 11:08PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

Veterans of the British Atomic Tests of the 1950s reported that they could see the image of the bones in their hands when pressing their clenched fists to their eyes miles from the site of thermonuclear explosions - presumably due to gamma rays.

X-rays too can be perceived by the human eye under certain conditions. See:

Lipetz LE The X-Ray and Radium Phosphenes Brit. J. Opthalm. (1955) 39, 557

Which you can download free here:

Conundrum

Sun Mar 25 2012, 06:58AM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

heh..
One could theorise that if life ever evolved on a planet orbiting around a neutron star, pulsar or white dwarf then the inhabitants could have deposits of a metal sulphide in their "eyes" such as ZnS or BaS and "see" X-rays as we see normal light.

Obviously the sensory organ would probably resemble a fly's eye with metallic tubes in place of lenses.

Question is, would DNA be stable in multiple gigarems per hour doses?
I think it would need some very extensive repair mechanisms, probably involving redundant shielded genomes with quorum sensing to "choose" the correct copy of each gene for replication and apply the repair to the other broken copies.

-A

Steve Conner

Sun Mar 25 2012, 08:08AM

Registered Member #30 Joined: Fri Feb 03 2006, 10:52AM
Location: Glasgow, Scotland
Posts: 6706

Aren't cockroaches supposed to be resistant to radiation? I wonder how they protect their DNA.

Or maybe Conundrum's lifeforms could be based on something other than DNA.

When I worked in telecoms, they were just bringing in DWDM, dense wavelength division multiplexing. The ITU defined a set of standard wavelengths in the 1550nm band, just like radio channels, and you can buy carefully tuned diode lasers for each wavelength, as well as optical filters for separating the channels. Anyway, the result is that you can stuff 10 channels of data down a fibre that could only take 1 before.

1550nm is chosen because the glass used for fibres has its best transmission properties there, but it's inconvenient otherwise. For a start it is pretty much invisible on anything. Even silicon photodiodes struggle with it: you have to use expensive InGaAs ones for good results.

I also used 808nm pump lasers, and we once borrowed a little scope with an image intensifier type tube inside to view light leaking from our setup. They also showed up clearly on cellphone cameras.

I didn't try viewing the output of the 500mW ones directly.

Conundrum

Sun Mar 25 2012, 12:17PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4061

DNA was once theorised to be a triple helix, by Linus Pauling.
Perhaps a DNA analog based on alternating heavy metals as bases ?!

Suggest lead, mercury, thallium and barium.
Gold might also work, but I suspect that it would be too nonreactive for this.
Silver might be possible, but the criteria would be stability with ambient radiation..

Might only work with metals where they selectively bond only with specific metals, or a metal/protein complex with an antisense component?

This would potentially work well, MDNA lifeforms would be far better at using ambient metals in their
environment and potentially exist at far higher temperatures approaching the melting point of lead.

Wonder if NASA has considered this possibility?

-A
#include "youcantbeserious.h"

Proud Mary

Sun Mar 25 2012, 10:12PM

Registered Member #543 Joined: Tue Feb 20 2007, 04:26PM
Location: UK
Posts: 4992

I'm sure that our concept of vision, and what it means to 'see' - ideas dependent on a very small segment of the electromagentic spectrum - are far too conservative and limiting.

Do bats process their return echoes into something we could understand as a 3-D picture? Are the bats 'seeing' with sound?

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