| 摘要 |
PURPOSE:To detect the abnormality of an encoder before performing feedback control and to prevent the disordered operation of an optical system, by counting A-phase and B-phase pulses and, when the A-phase and B-phase pulses do not stay at fixed values within a fixed time, generating an abnormality signal. CONSTITUTION:A rotary encoder 7 is connected with the interruption circuit of a CPU 1 and outputs A-phase and B-phase signals, whose phases are different from each other by 90 deg., and an abnormality detecting circuit 8 outputs an abnormal output signal and turns on a LED, etc., when the signal of the encoder 7 is abnormal. When an optical system comes out of its home position, the encoder 7 permits interruption of A-phase and B-phase and actuates a timer 4 to count addresses. It is discriminated that the A-phase and B-phase signals are normally outputted when the number Np of pulses generated during one rotation of a motor 5 within a limited time does not stay in a range Np-1<=Address B<=Np. When address A=Np is not realized within the limited time, the abnormality detecting circuit 8 stops the motor 5 and turns on a LED, etc., by outputting an abnormality detecting output. |
