We introduce a novel common-path interferometric measurement setup for optical quality testing The setup is based on an optimized diffractive lens which produces two diffraction orders with equal efficiency and thus forms two interfering beams without any beam splitting or mirror alignments The fabrication steps of the diffractive element are presented and the testing of the setup with injection molded millimeter scale lenses is briefly discussed

Common-path interferometer with diffractive lens.

A point diffraction interferometer with random-dot filter

A new type of interferometer is developed by putting a filamentary spatial filter on the diffraction plane of a double-diffraction optical system. A small phase object is placed in the object plane of the system. The light passing through the uniform region around the phase object is scattered by the filter. This scattered light interferes with the light passing through the phase object in the image plane; a common path interferometer is constructed. In order to obtain good visibility of the interference fringes in the image plane, optimum conditions are discussed from scalar diffraction theory and are confirmed experimentally. By displacing the filter along the optical axis, we can change the phase difference between object and scattered light. Therefore, the phase acceleration or retardation at a point in the object can be precisely determined by analysing the intensity change at the conjugate point in the image plane during the displacement of the filter. Experimental results show that the error in suc...

The Interferometer Using a Filamentary Spatial Filter and Its Application to Phase Measurement

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C.P. Grover

Papers

Random partial diffuser as beam splitter in a new, common path interferometer