| 摘要 |
PROBLEM TO BE SOLVED: To specify the surface of a lens involved in the generation of flair light while detecting very weak flair light by detecting the flair light generated by an optical system to be measured based on a received light signal from a photodetecting means corresponding to an interference fringe generated by conversion of an optical path length by an optical path length conversion means. SOLUTION: A second reflection mirror 140 is moved by a reflection mirror drive means 800 and when the optical path length of the reference light K1 matches that of the control light K2, a relatively intense interference fringe is generated. In other words, an output amplitude of a photo detecting means 200 is increased, a position which is defined as reference position. Moreover, when an increment optical path lengthΔof a control optical path due to the movement of the second reflection mirror 140 with the reflection mirror drive means 800 is equal to an optical path lengthΔF increased by a flair of the lens, slightly weaker interference fringe is generated and an output signal with a smaller amplitude is produced from the photodetecting means 200. Thus, the optical path lengthΔF increased by the flair on the surface of the lens is determined by measuring a moving valueΔ/2 up to the generation of the interference fringe from the reference position of the reflection mirror 140, thereby enabling specifying of a lens involved in the generation of the flair.
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