This thesis is focused on the design of phase shifting diffraction grating interferometers for precision optical surface testing. The interferometer employs a single reflective diffraction grating, which performs manifold functions of beam splitting, beam recombination, and phase shifting driven by a piezoelectric micro-actuator. The suggested design allows generating a high quality reference wave from a small active grating area that can be readily fabricated with good homogeneity of grating substrate and uniformity of groove spacing. The test and reference waves encounter no other optical components, so only a small active surface area of the grating affects the test result. And the fiber-optic confocal microscopic design adopted to solve the alignment problem between the grating and the converging wave greatly reduces systematic errors of the interferometer. In addition, the capability of phase shifting provided by translating the grating enables to readily measure figure errors to nanometer accuracy.
It is demonstrated that the grating interferometer can readily be extended to test large aspheric surfaces by incorporating appropriate computer generated holograms (CGH) modifying the optical path of the test wave front. Binary amplitude modulation type CGHs are designed and fabricated by an e-beam lithography system for null testing of large aspheric surfaces. Experimental results of spherical and aspheric surface testing verify the measurement system.
