| 摘要 |
There is provided an encoder in which the absolute angle can be detected with high accuracy even when the irradiated position of light to be detected with respect to a scale is displaced from a reference, and a photodetecting device for an encoder used for such an encoder. In the encoder 1, by passing light to be detected through a straight-line light transmitting portion 17, a bright portion 19 to which the light to be detected is irradiated is formed in an area of a scale plate 11 containing mutually separate parts of arranged lines L 1 and L 2 and also a dark portion 20 to which no light to be detected is irradiated is formed in the other area. Accordingly, a relative angle between light intensity peaks P 1 and P 2 (reference relative angle) can be uniquely calculated based on the shape of the light transmitting portion 17. Therefore, in the encoder 1, even if the irradiated position of the light to be detected with respect to the scale plate 11 is displaced from the reference, the absolute angle can be detected with high accuracy by calculating a deviation amount of a relative angle on detecting the angle from the reference relative angle as a corrected amount alpha°.
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