| 摘要 |
PURPOSE:To extremely reduce the effect of dust in an image sensor while the resolving power in a measuring direction is kept high, by projecting the image of an article to be measured onto the image sensor in a measuring direction at a magnification higher than that in the direction forming a right angle to said measuring direction. CONSTITUTION:A first image sensor 220 is arranged in the direction wherein the picture element thereof crosses the surface of paper at right angles and the image of a member 10 is projected on the first image sensor 22 at a 20 times magnification by an objective lens 212. Negative and positive columnar lenses 237, 238 are oriented so that the column axes thereof are at right angles to the surface of the paper and the negative columnar lens 337 is arranged so as to obtain emitted luminous flux in the plane parallel to the surface of the paper and, therefore, by moving the positive columnar lens 238 on an optical axis in the plane parallel to the surface of the paper, the advance of said lens 238 is enabled. The projection magnification in the plane parallel to the surface of the paper comes to 1/2 by the negative and positive columnar lenses 237, 238. A second image sensor 239 has a plurality of picture elements arranged in the direction at right angles to the surface of the paper. By this method, the image of the member 10 is projected at a 1,000 times magnification in the plane at right angles to the surface of the paper and at a 500 times magnification in the plane parallel to the surface of the paper.
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