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Hi camera bakers,
Temperature is a factor of image quality of CCD and
CMOS cameras. Think of the "photon counting" scientific cameras cooled down e.g.
by peltier elements and fluid nitrogen. (Not only concerning IR and thermo
cameras. There are other reasons.)
First of all there are temperature effects in the
standard electronic circuits (change in bias voltage, amplification, even
in timing, ...). The reason is that
passive elements (capacitors, resistors,
...) change their values with temperature. And of course semiconductors
(diodes, transistors, ICs, ...) too.
Especially the efficiency of the
sensor depends on recombination of electrons and
holes, thermal equilibrium of charges, width of
pn junction, and whatever. And in some certain physical laws
relevant for semiconductors temperature plays an
important role.
Usually degrading of specs is corrected - read: is
kept stable more or less - in a certain temperature range by various electronic
compensations. If you compare the quality at the edges of these temperature
range you might see some changes. Consumer
electronics are roughly designed - and the ingredients are selected accordingly
- for operating between about (0 ...) 10 and (30...) 45
centigrade ambient temperature. Outside this band the electronics are running
out of specs and may degrade in accuracy and lifetime. And the sun can
be really too hot.
Spoken global, in general and very simple: The
effects are different concerning analogue, digital and media
electronics/magnetics. First of all in basic circuits e.g. the sensor noise
(scattered, without pattern) increases with temperature. Hard to correct by
electronics near the source, usullay it is done by firmware/software -
medium filter, bandpass, ... (Of course you can cool the sensor ;-)
Errors deriving from analogue electronics or
sensor structures often show bigger error patterns like stripes,
lines, blocks, loss of contrast/dynamic/brightness ... according to the
channel structure of the sensor, read-out and A/D-conversion lines.
Digital and media errors are somehow similar to
drop-outs of old video tapes - information is just missing. Due to data
structure "scrambling" can take place, but usually not "noise". Well, more valid
for digital media than for analogue ones.
Walter
(PS As long as I'm alive, I'm
immortal)
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