Patent ID: 9041940
Filing Date: 2015-05-26
Classification: G01B,G02B

Abstract:
1. A three-dimensional shape measuring apparatus using a confocal optical system, comprising: an aperture plate provided with a plurality of confocal apertures which respectively allow light beams from a light source to pass therethrough and which are two-dimensionally arranged to have a predetermined arrangement period; an objective lens configured to converge each of the light beams having passed through the plurality of confocal apertures, at an object side focused point, and again converge each of reflected light beams formed by reflection of converged light beams at a measurement object, at respectively corresponding confocal apertures; a focus position changing unit including a rotating body provided thereon with a plurality of parallel plate type members different from each other at least in one of refractive index and thickness and arranged along a rotation direction so as to cross an optical axis of the objective lens, and a driving portion configured to continuously rotate the rotating body at a predetermined speed, the focus position changing unit being configured to discretely change a position of the object side focused point in an optical axis direction each time the parallel plate type member crossing the optical axis is changed by rotation of the rotating body; a photo-detector group including a plurality of photo-detectors each of which outputs a signal corresponding to an intensity of a reflected light beam having again passed through the confocal aperture; an aperture plate displacement unit configured to displace the aperture plate at a constant speed in a predetermined direction perpendicular to the optical axis direction so as to change a relative positional relationship between the position of the object side focused point and a position of the measurement object in the direction perpendicular to the optical axis direction; an imaging control unit configured to make the photo-detector group perform exposure a plurality of times in a period of constant speed movement of the aperture plate in the predetermined direction perpendicular to the optical axis direction, and to make the photo-detector group perform each of the exposures each time an imaging target region is included in the parallel plate type member, and to control a moving speed of the aperture plate, a rotation speed of the rotating body, and an exposure time and exposure timing of the photo-detector group so that the exposure time of the photo-detector group coincides with a time during which the aperture plate is moved by a distance obtained by multiplying the predetermined arrangement period by a first positive integer; a height determination unit configured to, based on the signal of the photo-detector for each of the positions of the object side focused points discretely changed in the optical axis direction by the focus position changing unit, estimate the position of the measurement object at which the intensity of the reflected beam incident on each of the photo-detectors becomes a maximum; a cover member provided over the aperture plate such that the cover member is displaced integrally with the aperture plate by the aperture plate displacement unit and such that the plurality of confocal apertures are provided in a closed space formed by the cover member and the aperture plate, the cover member being configured to include a transparent body that is provided between the light source and the aperture plate, that allows the light beams of the light source to pass therethrough and that allows the light beams of the light source to be irradiated to the plurality of confocal apertures; and an imaging optical system designed in consideration of optical properties of a whole optical system including the transparent body of the cover member, and configured to guide the reflected light beams having again passed through the confocal apertures to the photo-detector.