Optical scanning apparatus with dynamic scan path control

摘要

The system includes a primary scanner which produces a scanning optical beam, and a photoresponsive error sensor which measures over the scan path the successive differences between the actual position of the scanning beam and the desired position of the scanning beam and produces error signals. The secondary scanner is connected to the error sensor for response to the error signals to dynamically correct the position of the scanning beam during the course of the scan. The primary scanner provides a main optical scanning beam and an auxiliary optical scanning beam traversing substantially the same optical path. The error sensor includes a graticule mask having a substantially uniform optical density along the desired scan path and a graded optical density transverse to the desired scan path of the auxiliary scanning beam.