| 摘要 |
PURPOSE:To obtain an optical measuring apparatus, which can be focused, without utilizing the edge part of an object to be measured itself, by superimposing the image of a knife edge as a pattern filter on a part of lighting light through a projection lighting system. CONSTITUTION:A pattern filter 26 has an edge part. A knife edge image 26A of the knife edge 26 is formed on an object surface to be measured 8 through a projecting lens 14. The knife edge 26 is arranged in this way. A sensor 42 is arranged in the vicinity of an image forming plane IP. When a reconstituted image of the knife 26B of the image 26A through the lens 14 crosses a part in front of the plane IP, a focal point signal (a), which is varied with the variation of occulting light, is outputted. A vibrator 28 vibrates the filter 26 and outputs synchronizing signals d1 and d2 in correspondence with the vibrations. A control circuit operates the vibrator 28 and operates a Z-axis driving device 16 at the same time so that the changing amount of a focal point signal (c) becomes the maximum value. It is judged that the object to be measured is focused at a position, where the changing amount of the signal (c) becomes the maximum value. Thus the focusing can be achieved without using the edge part of the object to be measured itself. |
