RE: [Histonet] flat bed scanners (and 3D objects)

From:Bill Blank

At 9:08 AM -0800 3/17/04, Morken, Tim - Labvision wrote:
>I'm not clear to me how, as Bill suggests, the detector of a scanner could
>have an effect of depth of field. Isn't the detector essentially like film -
>a flat surface? It seems to me it is the optics that determines the depth of
>field and that maybe Bill's CCD scanner simply has different optics than the
>cmos scanner he mentions.

My Experience is completely empirical. I have tried reading the 
photonics and optical reasons, but have not really understood them. 
There was a recent article (in the last year) about CMOS detectors in 
Photonics magazine which I no longer have. What I remember is the big 
advantage of CMOS is that it is cheaper. The dynamic color range and 
something called the fill factor are still inferior to CCD, but 
getting closer. I did a quick search on Google this AM, but really 
only found things about digital cameras where the optic effect is 
more obvious (at least to me when one can vary the aperture of a lens)

The CCD scanners tend to be the higher end scanners and it may be, as 
Tim said, that the optics are different.

With my PL III's I can get 3D objects almost an inch thick in focus. 
With one of the CMOS scanners I got free with something, I couldn't 
get an entire high relief coin in focus (say 1/8th inch). I gay that 
scanner away. besides, it was USB 1 and too slow.
Bill Blank (Celtic studies and numismatics)

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