| 摘要 |
PURPOSE:To improve the detection accuracy by placing a linear pattern being parallel to an incident surface on the same optical axis as a linear pattern being vertical to the incident surface, and setting a reference position of the vertical pattern by an image forming state of an image of the parallel pattern. CONSTITUTION:A luminous flux from a light source 11 illuminates cross-shaped slits 13A, 13B being linear patterns on a slit plate 13 being vertical to an optical axis, and a slit image is projected at an incident angle alpha onto the surface to be inspected 1. Its reflected light is condensed through a diaphragm 22, and the slit image is formed again on a light receiving slit plate 23. Subsequently, by detecting the displacement quantity DELTAy in the direction being parallel to the incident surface on the plate 23 of the pattern 13A being vertical to the incident surface S of the cross-shaped slit, a displacement in the vertical direction of the surface 1 can be detected. Also, by detecting a focus on the plate 23 of the pattern 13B being parallel to the incident surface S, a conjugate relation of the plate 13 and the plate 23 can be set exactly. In such a way, the reference for detecting the displacement of the surface 1 by the pattern 13A can be set with high accuracy. |
