A technique for measuring three dimensional deformation of diffusely reflecting plane object by hologram interferometry is proposed. By using two optical systems, one with two symmetrically oblique illuminating directions to the object plane and another with normal illuminating direction, three kinds of interference fringes can be obtained in one hologram plate. Two types of fringes obtained through optical system with two illuminating directions are then superimposed additively in one case and multiplicatively in another case. Then in both cases, two types of moire fringes (additive and subtractive) are obtained through superimposed interference fringes. Then by comparing these moire fringes with the third interference fringes, information about three dimensional deformation can be derived.

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In recent years, with the development of coherent optics and holographic techniques, it is often necessary to measure the optical path difference in a microscopic phase object using a high magnification and high resolution interference microscope for transmitted light.
For this purpose, a high resolution interference microscope for transmitted light applying a holographic real-time interference method has been realized corresponding with a Mach-Zehnder type interference microscope, and the problems for realizing such an instrument are discussed.

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