Patent ID: 8203719

Claim:
A method of expanding the operating range of a metrology system for measuring aspheric test objects comprising steps of: associating an optical wavefront propagator with a physical test object in a plurality of different relationships for conveying optical measurement wavefronts to the test object; acquiring partially overlapping optical wavefront measurements of the test object in each of the different relationships by measuring shapes of the measurement wavefronts with an optical wavefront-measuring gauge having a limited capture range of wavefront shapes; reshaping the measurement wavefront into an aspheric form with a variable optical aberrator between a limited number of the measurements in the different relationships to maintain the measurement wavefront within the capture range of the wavefront-measuring gauge; incorporating compensators in an operation for assembling the partially overlapping measurements into a composite measurement, and acquiring values for the compensators in the operation for reducing differences between overlapping portions of the measurements that are at least partially attributable to the reshaping of the measurement wavefront by the variable optical aberrator.