Abstract: Apparatus (10) for controlling a beam (12) of coherent light includes a reference scale (38, 138) provided with indicia forming a plurality of spokes having two sets of properties. The first of the two sets of properties is an evenly spaced first set of edges (41) arranged for generating a data clock exactly referenced to a position of a first of the two separate, perpendicular directions. A second set of edges (44) are each spaced variably from an associated one of the first set of edges (41) as a function of the other of the two separate, perpendicular directions, making the second of the two sets of properties a variable width of each of the spokes.

Abstract: This data processing system for a pattern generator receives data specifying each quadrilateral element in a pattern to be generated by laser scanning or other technique. The scanning is accomplished by swaths. In the preprocessor, separate vectors are produced for the portion of each quadrilateral edge in each swath. A real time processor, including a "pipeline" or cascaded set of beam processors, is used to generate a bit map from these clipped edge vectors. The bit map itself is skew compensated to take into account relative movement between the laser scanner and the target during pattern generation.