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12 micron thermals


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4 hours ago, Duncs said:

For us luddites, what does that mean? :)

Oh dear, for those using the current system using 17 micron devices, not much at all. What it means is that using 12 micron devices you can achieve a higher optical magnification with any given focal length lens. eg. using a device with say a 50 mm lens and 17 microns you get 2 X magnification, using one with a 50 mm lens and 12 microns you get 2.8 X. All due to the smaller FPA size, even when using nominally the same number of pixels. The same effect as as when you use a 384 X 288 sensor and 640 X 480 FPA with the same lens. You get a higher magnification but a slightly lower quality viewed image. Now before anyone gets too excited and raves on about a better smoother image, stop there. The fact that you must interpolate (stretch) the FPA image to the AMOLED to be able to see it, it is therefore "digitally" zoomed by a factor of 1.4, this then produces a "viewed" image of the same quality as that of the same as a 17 micron FPA.

Big deal you say? OK but the cost of germanium lenses is high, so you basically save money with the shorter focal length lens, as the diameter can be smaller diameter and retain the same f speed.

A factor that is not well known is that Military and most Government bodies still require only 17 micron devices. One day that will no doubt change.

In the past 12 micron devices were less sensitive than 17 due to the fact of the area of the pixel covered by IR (IR is the same as visible light, other than wave length and for this subject can be referred to in the same way). Nowadays the 12 micron devices are made from Vanadium oxide rather than Amorphous Silicon and are therefore much the same sensitivity. If you want to know more about that, ring me and I will explain how it works, too hard here.

Be very aware regarding the so called sensitivity figures quoted by many manufacturers, they are BS, two reasons, 1, they just quote a figure knowing there is NO WAY the punter can check or even notice the difference. 2, they do tests on the sensor using higher test target temperatures than the industry standard of 30 degrees C. This way they can say they are tested and the figures are correct, while using the very same sensor. (Talk to FLIR or Linred about this).

For me to try and put all this in understandable words on paper is difficult, hopefully some of this is makes some sense?? We run workshops for this where I use a PP presentation and can discuss at the same time, much easier.

Does any of that help?


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