DISPLACEMENT MEASURING INSTRUMENT

摘要

PROBLEM TO BE SOLVED: To measure displacement with high precision irrelevantly to the surface state of a surface to be measured and to form an image while eliminating aberrations in the width direction of a photodetection surface. SOLUTION: A scanning means 4 makes a scan at constant intervals with an irradiation light which is made incident directly on an object surface 20a of the object 20 to be measured. Scattered lights of the irradiation light are detected by a couple of photodetecting means 6-1 and 6-2 which are provided opposite each other across the irradiation point at equal distances from the irradiation point. The photodetecting means 6-1 and 6-2 are composed of lens arrays 7-1 and 7-2 which converge the scattered lights from the scanning irradiation point orthogonally to the scanning direction at positions corresponding to respective irradiation points and spherical convergence type image forming lenses 8-1 and 8-2 which images the irradiation light on the photodetection surfaces of the photodetecting elements 90-1 and 9-2. Consequently, even if one photodetecting element 6-1 is unable to detect the scattered light owing to a step on the object surface 20a to be measured, the other photodetecting element 6-2 photodetects the scattered light to measure and output the displacement.