Wavefront sensing for testing spherical surfaces and lens systems: a new approach

Some of the techniques used for wavefront sensing that do not require coherent light sources are reviewed and a new arrangement developed by the authors is described. The latter ws produced as part of a study looking at absolute measurement of sphericity. It uses a measurement technique that basically determines the transverse ray-aberration (in effect the wavefront slope) associated with different parts of the pupil of the test piece and from this computes the wavefront distortion. The pixels of a CCD camera define the separate areas of the wavefront and in conjunction with scanning gratings, the signal from each pixel measures the associated wavefront slope. The wavefront distortion is computed from the slope values. The paper describes the results that have been obtained so far using the current breadboard arrangement as well as some of the advantages and disadvantages of the method compared to other techniques.