Scanning beam control system and method with bi-directional reference scale

摘要

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.