Implementation of the Ritchey-Common Test for 300 mm Wafers

The requirements are growing daily for large polished flat surfaces made to optical quality figure. The obvious and most reliable way of testing these surfaces is in a collimated space Fizeau cavity. Such a cavity, however, requires 2 or more optics the same diameter as the optical surface under test made to figure accuracies better than the part being tested. This makes for an expensive test. Another approach is to use the Ritchey-Common test where the single test optic is only slightly larger than the optics under test and its radius does not have to be tightly controlled. This less costly solution is traded against the increased computation of the Ritchey-Common test.