A tri-linear CCD or, more commonly these days, an offset hex-linear CCD,
or hyperCCD, is used in flatbeds. The filters are built into the CCD
itself - a layer of dye deposited on top of the photocells in each line.
That's *very good* to know!!!
I was a bit apprehensive about scanning B&W photos in color. On the
one hand color gives more information to facilitate editing but I was
concerned about the extra step of light going through filters.
But if the filters are built-in and even a "B&W scan" actually scans
in color, then there's no difference on that account.
Out of curiosity, how is a B&W scan done then? Are the three color
components combined (i.e. ~60% green, ~30% red, ~10% blue), or is one
(e.g. green) simply declared as the "B&W scan"?
Instead each line of the CCD simply samples a different point in the
image, then the head steps to the next position. After a few lines, the
green CCD line gets to the position that the red one was at earlier and
samples the green component of that line of pixels - then a few lines
later and the blue CCD line arrives and samples the data. So the CCD is
sending our red green and blue data all the time, but for different
lines. The scanner driver sorts it all out - as well as correcting for
the positions of odd and even pixels in the hyperCCDs.
And that explains something else! A (very!) slight apparent
misalignment of three colors (also noticed for the first time on a B&W
photo). I always wondered about that, but now it makes sense.
Don.
