| 摘要 |
PURPOSE: To widen the extent within which the position of a surface to be inspected can be accurately detected at the time of detecting the position of the surface to be inspected by using an oblique incidence system. CONSTITUTION: One slit image is projected upon a surface to be inspected and a slit image 25 having a width D is again formed on a light receiving plate 18A by condensing the luminous flux reflected by the surface to be inspected. Three light receiving slits 21A-21C having widths D are arranged on the slit plate 18A by deviating the images 21A-21C from each other by D in x-direction. The deviated amount of the slit image 25 in x-direction is found based on the signals outputted from photoelectric conversion elements 23A-23C on the back of the slits 21A-21C which are formed by vibrating the slit image 25 in x- direction. |
