Digital Infrared 101 by Jeff B

Infrared comes in basically 3 "colors" or "bands".
Long Wave,8 to 12 microns wavelength,used for long range thermal imaging,survelance, low temp applications. Mid Band, 3 to 5 microns, used for most thermal imaging, predictive maintenance, medical imaging. And Short Wave, or "near IR" .75 to 1.5 microns, used for Fibre optics,,tv remotes,some security (B&W)cameras ( use visible and IR for more low light sensitivity ).

Visible light , by the way, is .4 microns ( 400 nanometers, violet) to .75 microns ( deep red ).

The other in between bands are attenuated by atmospheric H2O and CO2 and look like fog in IR, not much use for imaging ( but great for pollution monitoring)

Glass and most plastics are opaque to all but theshortest wavelengths,,including lenses and filters, a "real" IR camera has optics made from solid germanium or silicon metal, exotic crystals ($$$) and use cryo-chilled platinum ccd chips.

CCD chips are sensitive to SW IR to a point.A B&W CCD security camera with a wratten filter (or without in a very dim room with tungsten light) shows some interesting images. Emissivity (covered in IR-102) is the prime factor. Black jeans and a black shirt can show as white jeans and black shirt in SW IR.

The Big Question,,,finally,, Does a color ccd camera "see" IR ? I'm not sure cause I have not tried it yet. If you can photograph a hot soldering iron,,elect. stove element (just below red hot in a dark room) or the TV remote, then you can see IR. But just barely,,,you might call it "extended red" sensitivity. (quantum mechanics is in IR-301).

The blue and green filtered pixels wont see IR, the red pixel filters,depending on cut off wavelength may pass some IR.But why? adding invisible IR to the red luminance signal would
corrupt the red channel data and throw off the visible red part of the image ! If our eyes, and
printers could see IR ok, ever see IR ink for your printer? Try using the red channel only.
When I take an IR image I set the upper temp. to white,the lower temp. to black and assign a false
color pallet in post processing ( this camera also has real time video (ntsc)output for IR videos.

Emissivity,color temp,Planks curves ( you'll like them )are in IR-102.

JeffB

* For the record I tried photographing several hot items with my e-10 in total darkness, and I am sorry to report that they did not register even at 20+ sec bulb exposure. Bo.

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