| 摘要 |
An optical absolute position encoder capable of obtaining absolute position data in a wide range utilizes the fact that the position of a transmitted or reflected light beam is shifted in accordance with the displacement of a grating window and the fact that the grating window can be specified depending upon the characteristics of the light beam which has passed through the grating window. Furthermore, precise position data is obtained by using two gratings which move relatively. The above-described data are combined with each other so that absolute position data revealing high resolution can accurately be obtained for a long stroke.
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