| 摘要 |
PURPOSE:To make it possible to simultaneously and accurately measure the degree of parallelism of a matter to be measured without turning over the same and without receiving the effect of dust etc., by arranging Fizeau type interferometers to the front and back sides of the matter to be measured in opposed relation to each other. CONSTITUTION:In using the titled apparatus, opposed reference plates 16, 26 are set as a first stage while an interference fringe is observed so as to bring the degree of parallelism between both plates to zero. Next, a plane-parallel plate 30 being a matter to be measured is set at a predetermined position. In this setting, the parallel plane plate 30 is supported by a support mechanism constituted so as to be three-dimensionally movable on the common optical axis of first and second Fizeau type interferometers. In such a state that the plane-parallel plate 30 is held as it is, the degree of parallelism between said plate 26 and the back surface 32 of the matter to be measured is calculated using the second Fizeau type interferometer. By the above mentioned measuring procedure, the degree of parallelism of the front surface 31 and back surface 32 of the plane-parallel plate 30 can be easily measured.
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