Re: gEDA-user: DIY thermographic camera?

[Kipton Moravec <kip@xxxxxxxxxx>]

I second that thought. Except "Sensitivity of silicon is fairly low for
UV light" should be "Sensitivity of silicon is fairly low for IR
(infrared) light"

There are some IR sensors that work at 3-5 micrometer wavelengths, but
they are really more sensitive to things at hotter temperatures. The
best ones for objects at around room temperature are in the 8-12
micrometer band. I have seen both side by side at demonstrations for the
military (German Army), and 8-12 is better for looking at a field for
people and vehicles. Unfortunately 8-12 systems is are more expensive
than 3-5 systems, which are more expensive than light or near infrared
you get from a camcorder. Expect to spend around 7-10 K$ for a little
8-12 camera.


On Wed, 2008-11-05 at 19:25 +0000, Kai-Martin Knaak wrote:
> On Wed, 05 Nov 2008 10:01:37 -0500, Randall Nortman wrote:
> 
> > ould one get reasonably useful results from a hacked camcorder or
> > digital camera with appropriate filters?
> 
> Short answer: No. 
> 
> Long version: The light detector in consumer camcorders and cameras is 
> based on silicon. Sensitivity of silicon is fairly low for UV light, 
> rises towards the red end of the spectrum. It peaks at 950 nm and drops 
> like a rock when going further to the infrared. However, the wavelength 
> of heat radiation of houses is an order of magnitude larger (about 
> 10 µm). The photo diode is essentially insensitive to this kind of 
> radiation. 
> 
> ---<(kaimartin)>---
-- 
Kipton Moravec AE5IB
"Always do right; this will gratify some people and astonish the rest."
--Mark Twain




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