The latest "Photonics Spectra" a photonics trade magazine has an overview of
improving technology used in CMOS imagers vs more mature CCD sensors: "CMOS
and CCD share more than a letter" Sept 2004. p50-58. (The abstract is not on
their website yet)
Bottom line the CMOS sensors are getting more complex in their manufacture
(read costly) and adopting many of strategies used by CCDs to improve
performance to get near CCD performance. They are now starting to use "pinned"
photodiodes, thinned substrates,shared transistors better fill factors and back
illumination for example. CCD's aparently still have an edge especially for
small pixel sizes, but gap is narrowing. Discusses issues of lensing/color
shifts, metalization fill factor etc.
Market numbers project biggest CMOS market in 2004 is telecoms (phones?) which
will double by 2006. Consumer electronics (conventional cameras?) are not
nearly as big. Industrial and data processing segments combined together are
bigger than consumer! It seems longer term car applications may get pretty
big, multiple rear view mirrors etc.?
( http://www.oemagazine.com/fromTheMagazine/jun03/wheels.html )
Quoted from Foveon marketing manager: "As you are shrinking that pixel , the
image is getting worse and worse" "You get to the point where the only thing
you are doing is increasing the number of megapixekls on your box. You are not
increasing the resolution because of course there is an optical limit."
One issue mentioned is the fact that the readout speed becomes a problem for
CCD as the pixel count gets large. TheCMOS devices can readout in parrallel
reducing data rates to the A/D etc if you duplicate digitization. This keeps
amplifier readout/digitization noise down as bandwidth is then greatly reduced.
Some older profesional articles discussing/comparing issues CCD's vs CMOS :
http://www.oemagazine.com/fromTheMagazine/feb02/detectors.html
"Dueling Detectors" This older article is by the guy who is the father of
CCD's from JPL and wrote the classic book on the devices. He explains how good
the performance of Hubbles CCD's are.
http://www.photonics.com/spectra/features/read.asp?artabid=484
2002: "CCD vs. CMOS: The Battle Cools Off "
http://www.oemagazine.com/fromTheMagazine/jan03/specialfocus.html
2003
.....Certainly, CCD technology will hold onto high-end applications like
medical and scientific imaging, says Brian O'Rourke, analyst at InStat/MDR
(Scottsdale, AZ). "CMOS will be big volume, low margin, and CCD will be smaller
volume, higher margin." Hot growth areas for CMOS image sensors include the
cell phone camera market. "That is the one market that just about every CMOS
image-sensor maker is looking at," O'Rourke adds, noting that roughly half a
billion cell phones are manufactured annually. "If you're a CMOS image-sensor
manufacturer, you look at that market and think, 'If I can just get a couple
percent, I can do pretty well.'"
The specter of a big payoff has actually delayed the consolidation of the CMOS
image-sensor market. "I have on record somewhere around 30 manufacturers
worldwide. That's obviously too many players," O'Rourke says. "I had expected
there to be consolidation by now, but that's really only happened to a small
extent. I think that everybody's trying to get into the cell-phone market."
Once the market leaders are sorted out, expect extensive consolidation in two
to four years, he says.
A Biased Dalsa view :
http://www.dalsa.com/markets/ccd_vs_cmos.asp
and
http://www.dalsa.com/shared/content/Photonics_Spectra_CCDvsCMOS_Litwiller.pdf
CMOS related :
http://www.dalsa.com/shared/content/OE_Magazine_Better_Mousetrap_Theuwissen.pdf
a fun animation :
http://microscopy.fsu.edu/primer/java/photomicrography/ccd/quantum/
Regards,
Tim Hughes
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