| 摘要 |
PROBLEM TO BE SOLVED: To provide a high reliable and efficient optical length gauge for displacement capable of making the distance between members trace, while protecting a light-receiving face. SOLUTION: The optical length gauge is composed from a movable scale with an optical grating at the preset pitch, an illuminant which is placed on one side of the movable scale, irradiating parallel rays toward the optical grating and a light receiving unit which is placed on the other side of the movable scale at the prescribed space, and receiving parallel rays passing through the optical grating. The light-receiving unit is composed from a light-receiving device on the same side of the movable scale placed on a flat plate basis, and a protecting unit covering the light-receiving device and its vicinity. Thus, the movable scale is made so as not to abut against the light-receiving device directly, even if the movable scale is deformed. COPYRIGHT: (C)2005,JPO&NCIPI
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