| 摘要 |
PURPOSE:To enable high-accuracy measurement of deviation of a specimen surface, even if it is of a 3-dimensional free curved surface, by installing a lens system in which 3 convex lenses are aligned on the common optical axis respectively and an image forming position detecting means provided with a CCD line sensor. CONSTITUTION:Convex lenses 2, 4, 6 are installed on the common optical axis, so as their focal points coincide. A laser beam from the source 8 is reflected on a point U of a specimen surface S through mirrors 9, 3 and a hole located at the center of the lens 3 and the reflected beam is developed into an image at a point W after passing through the lenses 2, 4. When a position of the point U is defined as (focal length +Z1) from the lens 2 and that of the point W as (focal length + Z2) from the lens 4, 2, becomes proportional to Z2. Further, a part of the reflected beams passes through 2 pin-holes of a slitted plate 5, converged by the lens 6 and irradiated onto a CCD line sensor 7. As the voltage output of the sensor 7 is provided with 2 peaks, from the difference of the numbers of elements corresponding to them the distance between elements are given. The distance Z2 and subsequently Z1 can be obtained basing on the distance by means of calculation.
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