There is an interesting article in EE Times this week on a digital
camera developed by Foveon Inc., a "startup backed by Carver Mead." It
uses 3 analog chips versus one CCD chip, where the colors have to be
interpolated, according to the article. The quality of the image is
targeted at medium format quality. It generates a 48M file,
4000x4000-pixel file. Because there is no interpolation of the colors,
"artifacts like moire patterns" don't occur as they do in traditional
digital cameras. This camera splits the incoming light with prisms into
3 beams.
check out:
http://www.techweb.com/se/directlink.cgi?EET19990712S0011
quote from the article:
Foveon avoids the color-interpolation problem by using a different
technique, which splits the incoming light into three beams with a
prism. The prism focuses the red light on a red sensor, the blue light
on a blue sensor and the green light on a green sensor. That approach
uses three times as many sensor chips, plus a multifaceted prism, but
eliminates the moire-pattern problem.
Foveon attaches its sensors directly to the prism faces with glue
that has the same index of refraction as the optical glass of the
prisms. This scheme eliminates the reflection and blurring problems of
earlier designs. The company has a patent pending for the process it
uses to attach its sensors directly to the prism.
Foveon employs analog VLSI chips modeled on the optical properties of
real film. For instance, a magnified Foveon image will show grain, even
though there is no film used anywhere in the process. Film has grain
because the particles that change color when exposed to light are of
varying sizes-big ones for dark areas with little detail and small ones
for light areas of greater detail in an image. Foveon's sensors mimic
that property of film.
"Our sensor works more like real film that has a gamma curve, which
slopes smoothly from low-density to high-density areas, corresponding
to the statistical distribution of coarse and fine grains, whereas CCDs
have a completely linear curve," said Mead.
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