SURFACE SHAPE MEASURING DEVICE

摘要

PROBLEM TO BE SOLVED: To stably and precisely perform the surface shape measurement of an object in a surface shape measuring device utilizing the interference of light and used for the measurement of the surface shape of a disc medium or the like. SOLUTION: A plurality of partial polarization plates 32 differed in size of a circular part 33 (the circular part 33 passes 2-frequency laser beam 29 as it is, and an annular part 34 passes only a linear polarization component having a vibrating surface parallel to the paper surface) is prepared. The partial polarization plate 32 is replaceably arranged in the optical path of a 2-frequency laser beam 29 outputted from a 2-frequency laser beam source 28 and having a linear polarization component having a vibration surface perpendicular to the paper surface and a linear polarization component having a vibrating surface parallel to the paper surface, so that the emitting size of a reference light 33 on a disc 26 can be varied.