From: Jonathan Kirwan
Subject: Re: Make infrared goggles inexpensively (like $10!!!)
References: <firstname.lastname@example.org> <3D848F5E.91EC2A2F@xympatico.ca>
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NNTP-Posting-Date: Sun, 15 Sep 2002 19:47:36 GMT
Organization: AT&T Broadband
Date: Sun, 15 Sep 2002 19:47:36 GMT
On Sun, 15 Sep 2002 09:47:10 -0400, Joseph Legris
>Jonathan Kirwan wrote:
>> On Sun, 15 Sep 2002 12:00:47 +0100, "Prai Jei"
>> >No comprendo. If you can see it, it is (by definition) not IR.
>> Yes. The only possibility I could imagine here was anti-Stokes
>> fluorescence with up-conversion phosphors. Unlikely.
>> I think his argument on principle is that "very loud" 30kHz can be
>> heard. Which isn't anywhere close to a valid analogy, regardless.
>There are various definitions of the shortest wavelength boundary of
>infrared (760, 770, 800 nm), and the human eye responds weakly beyond
>760nm (some 6 order of magnitude down from the maximum sensitivity). I
>have a reference that shows measurable response past 800 nm. Conclusion:
>we can see IR, but not very well.
Yes, I have the same information. For example, the three color
sensitive cone pigments show a response factor of 1.0254E-5, 3.97E-6,
and 0 for 800nm.
But 5-6 orders down sensitivity is still asking too much. The flux of
the sun in the visible range as compared to only 100nm or 200nm
further out, will be rather similar in magnitude. Yet the filter
response curves aren't 5-6 orders down in the visible range where they
only "mostly" block. Not even at three-ply.
>Bill Beatty's descriptions more or less match the appearance of objects
>viewed with infrared cameras.
The simplest explanation for what our poster observed comes from
simply convolving the two filter responses he talked about. The
curves shown are in linear scale response, not logarithmic, and there
is probably substantial flux remaining almost across the spectrum,
though most of it will be in the 650+nm area. Certainly, there will
be plenty of 680nm light available, given the curves I saw. And that
There is no need to pull out some incorrect analogy to explain being
able to see some odd looking things. It's enough to use traditional
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.