| 摘要 |
PURPOSE:To make it possible to detect the absolute position, by providing a rotary polarizing plate comprising a linear polarizing crystal plate, which is cut along a plane that is perpendicular to both a vibrating surface and a polarizing surface, and providing a light emitting means that is arranged at a position facing a photoelectric conversion means which is arranged so as to face a fixed polarizing plate. CONSTITUTION:When a vibrating surface A of a rotary polarizing plate 2 agrees with a vibrating surface A of a fixed polarizing plate 3, a photoelectric conversion means 4 receives the maximum amount of light. The highest voltage is outputted from terminals 5 and 5'. When the vibrating surface A of the rotary polarizing plate 2 crosses the vibrating surface A of the fixed polarizing plate 3 at a right angle, the photoelectric conversion means 4 receives almost no light. The output from the terminals 5 and 5' becomes almost zero. Namely, the output of the photoelectric conversion means repeats the increase and decrease, with the rotary angle of 180 deg. of a rotary body to be checked as a period. The waveform of the output voltage is approximately close to a sine wave. A DC component including an output due to leaked light is removed. Thus the central potential of the output voltage of the photoelectric conversion means 4 can be made almost zero. The device can be used as the rotary position detector. |
