On Mon, 8 Nov 2004 02:55:28 +0000, Karel Kulhavy <[EMAIL PROTECTED]> wrote: > What abut exposing the codes on a sheet of document film, epoxying to a glass > plate and using linear CCD for readout?
It's a gray area (no pun intended)-- the results will depend on construction details, and the output characteristics of your CCD. At the very least, you might want to consider a magnifying lens in front of the CCD or photodiode. There are also some signal processing tricks you can do if the CCD produces a quality analog signal, and you use diffraction techniques to vary the brightness (instead of having sharp on-off transitions). It's like the difference between sigma-delta and Flash ADCs-- for a given sampling speed, you're getting closer to the analog speed of the shaft via better sampling resolution. Check out some of the home pages of high-precision encoder manufacturers-- they may have some useful hints. Renishaw and Heidenhain come to mind, but there are others as well. One thing you might want to search for is sinusoidal outputs. -- - Charles Lepple
