REGULAR REFLECTION TYPE DISPLACEMENT GAUGE

摘要

PROBLEM TO BE SOLVED: To perform high-speed measurement on objects other than transparent objects and high-accuracy measurement on the transparent objects by using one displacement gauge by scanning a liquid crystal shutter arranged on this side of a photodetector. SOLUTION: A liquid crystal shutter 1 is arranged on this side of the light receiving surface of a photodetector (PSD) 51. A state where only the reflected light from the surface S to be measured of an object 52 to be measured is interrupted and another state where only the reflected light from the rear surface N of a transparent object is interrupted are produced by scanning the light shielding portion 1a of the shutter 1 along the light receiving surface of the PSD 51. When only the reflected light from the surface S to be measured is received by means of the PSD 51 by only interrupting the reflected light from the rear surface N, the displacement of the surface S can be detected accurately by reducing measurement errors even when the object 52 is transparent. In addition, the thickness of the object 52 can be detected based on the difference between the light receiving centers in the state where only the reflected light from the surface S is interrupted and the state where only the reflected light from the rear surface N is interrupted on the PSD 51.