METHOD AND APPARATUS FOR MEASURING THE ILLUMINATION UNIFORMITY IN A RING FIELD PROJECTION SYSTEM

摘要

This invention relates to a method and apparatus for measuring the exposure variation in the cross scan direction in an optical projector and scanning apparatus of the type that uses an annular aperture or slit. This measuring is achieved by measuring the light intensity from point to point along the arcuate illuminated area. Where the illuminated area is tapered so as to accommodate a pivoting carriage the system of this invention processes the intensity signal to yield a uniformity signal that only indicates departures from the ideal.