On Mon, 17 Nov 2003, Jim Richardson wrote:
>...Most CCDs are pretty sensitive to near IR, and so the
>manufacturer puts in a filter to correct for normal human colour
>perception.
...and to minimize problems with the fact that certain fabrics often used
in clothing are opaque to visible light but pass significant amounts of
near IR.
Note that *color* cameras have color filters right on the CCD, and those
will block a lot of the IR, so you want a B&W camera for this.
Sufficiently intense IR emissions can even get through the filters. CCD
cameras reportedly can see aircraft IR jammers (used to confuse the homing
heads of heat-seeking missiles) as flashing lights... and that's not even
near IR, or at least there's not much near IR in it. (But the power output
is very high.)
Henry Spencer
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