Max detection distance of a human body using thermal imaging sensor???

I was wondering if anyone knows what that maximum distance is that you can detect a human body using thermal imaging technology. I know the pixel count makes a big difference. Those steady cams on police helicopters seem pretty good at long range.
-- Shawn
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This will be determined by a few factors. First, what is the resolution of the system? The pixels in a given angular field will be a constraint. Second, what sort of sensitivity does the system have to the temperature difference? Liquid nitrogen cooling can extremely enhance the sensitivity of your detector, and it also helps if the background temperature is low to start with. Third, what is the noise floor of your system? By that I mean, "what sort of image noise is present in the image sensor?" You see, image noise can blot out the heat signature, and in most systems this is helped greatly by cooling (see note above about liquid nitrogen). But even in cooled systems, there is random atomic noise or thermal noise that is generated inside the image sensor, inside the amplifiers, inside every component in the signal path and processing path. Even impedance mismatches can contribute echoes and signal reflections that can add to the noise floor. Fourth, what is the f-stop of your system? Anyone who is familiar with cameras and optical systems is familiar with the effect that your aperture versus its focal length can have on many aspects of image quality. "Speed" is the attribute usually associated with "f-stop", by the simple logic that the larger your input lens, the greater light it can gather, and that greater the magnification, the less effective the available light is in creating an image. In other words, a large primary lens or light collector and a short focal length can give you some very good image gain. On the other hand, you can lose a lot of your image as unfocused light if you use too large an f-stop, trying to compensate for low light (or thermal) levels. There are other factors, and I am sure to have forgotten some important ones, but to be brief, you need a large input lens, short focal length, higher resolution sensor, a cooled or thermally stable system, and a lower outdoors ambient temperature- then, it is possible to detect body heat to distances of kilometers. Experiment and see how these factors add up.
Cheers!
Chip Shults
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Thanks for the info. I just found a company in NM that makes some great TI cams for MIL aps. I'll call them and get educated.
-- Shawn

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On Thu, 29 Jan 2004, Shawn Brown wrote:

Care to share the website info?
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Ooops, sorry....http://www.senspex.com
-- Shawn

TI
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