| 摘要 |
PURPOSE:To obtain a high performance encoder free from variations in the intensity of light being received, by comparing a first beam reflected at a reflecting section of a rotary passive reflector from the same light source and a second beam reflected at a slit of the rotary passive plate to calibrate. CONSTITUTION:A group 22 of circular slits are arranged roughly at the center of a surface of a rotary passive reflector 20 facing a fixed plate 6 and a completely reflecting section 24 is formed concentrically on the circumference. Out of beams from a light emitting element L as light source, a beam I passes through slits 7 of the fixed plate 7 via an outgoing optical fiber 9, reflected by a reflecting section 24 and received with a light receiving element via slits 6' and an incoming optical fiber 10 whereby a light power is converted into an electrical signal. After passing through slits 6' of the fixed plate 6via an outgoing optical fiber 9', the other beam II is reflected by a slit 22, passes through the slits 6' again, and received with a light receiving element via a incoming optical fiber 10' whereby light power is converted into an electrical signal. Then, with the comparison and calibration of the beam I and the beam II, an encoder is obtained free from variations in the intensity of light being received.
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