From: Mike Poulton
Subject: Re: Make infrared goggles inexpensively (like $10!!!)
Date: 17 Sep 2002 08:17:16 GMT
Organization: MTP Technologies
References: <email@example.com> <3D848F5E.91EC2A2F@xympatico.ca> <firstname.lastname@example.org>
On 17 Sep 2002, email@example.com (William J. Beaty) said:
> Jonathan Kirwan wrote in message
> How is the rolloff in the human eye sensitivity function at the
> IR end fundamentally different than the rolloff of human ear
> sensitivity at the ultrasonic end? If you think my analogy is
> misguided, please show this. Are you that confident that you
> can't hear a pure 30KHz tone no matter how loud the signal?
> Are you confident that you can't see a narrow 800nM emission line
> no matter how bright the light?
>> If anyone has the exact filter response data, over wavelength, for
>> these filters, I'd be more than happy to convolve them with the human
>> photopic vision curves to find the resulting response. I think we
>> will find, from that, where the dominant is at. And I rather doubt
>> it will be in the longer than 800nm area.
You can see 808nm. You can actually see 830, too. How do I know? I've
seen both, from laser diode sources. Many others have, too, and it has
been confirmed that this is not due to off-frequency emissions. In
order to see these wavelengths, loads of power is needed -- too much
power. The general rule around near IR diodes is that if you see the
light, you are in danger and should close your eyes INSTANTLY. Indeed,
studies have shown that (within reason) visibility is just a function of
wavelength, even out at the edges of the spectrum.
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