| 摘要 |
PROBLEM TO BE SOLVED: To provide a position measuring apparatus by which position can be measured with high accuracy by means of a simple principle and by which a very small distance and a sufficiently large distance as compared with its resolution can be measured. SOLUTION: In a CCD 60, many cells In, etc., are installed at interval of 11μm, and ten continuous cells form one group. Many slits 511 , etc., are formed at interval of 10μm in a slit mask 50, and nearly parallel light is projected from an upper light source. Out of the light, only light which has passed the slits is projected on the CCD 60. The slit mask 50 can be translated and moved in the x-axis direction. One slit 511 in the slit mask 50 comes directly above the leftmost cell In in a Gn group, and the cell In receives the maximum quanity of receivable light. The position of an adjacent cell Jn and the position of a slit 512 on it are deviated slightly, and the output value of the cell Jn is a little smaller than a maximum value.
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