SHAPED APERTURE FOR RASTER SCANNER
Original Publication Date: 1983-Apr-30
Included in the Prior Art Database: 2004-Apr-04
Xerox Disclosure Journal
Illumination reaching the linear imager, such as a Charge Coupled Device (CCD) in a raster input scanner, is non-uniform. Specifically, the illumination is higher in the center of the field than at the ends. This is due to cosine fourth drop off, flare light and lamp end fall off. It is proposed here that a shaped aperture 5 be positioned in front of the imaging lens 6 to control the illumination profile. By using the properly shaped aperture, the non-uniform image characteristic can be greatly improved. In Figure 1, the aperture 5 comprises a slit-like opening 8 having straight sides 9. In Figure 2, an alternate aperture configuration is shown wherein one or both of the sides 10 of the slit-like aperture opening 8 are curved slightly.