| 摘要 |
PURPOSE:To prevent the error due to the temperature change and the change accompanied with time elapse, by using the variable gain amplifier to stabilize the output of the photodetector of the position detecting device and by outputting a pulse signal when this output is a prescribed voltage or more. CONSTITUTION:The light of light emitting diode 3 which passes through light passage part 2a provided on rotary disc 1 is received by photodetecting diode 4, and the output of a sine waveform is input to variable gain amplifier 5 and control circuit 6. Control circuit 6 controls variable gain amplifier 5 so that the output of variable gain amplifier 5 becomes always the waveform of a fixed amplitude. The signal amplified by amplifier 5 is compared with the reference voltage of voltage setting circuit 8 by comparator 7 and has the waveform shaped by waveform shaper 10 and is taken out from output terminal P3 as a stabilized position signal. |
