| 摘要 |
PURPOSE:To improve the reliability by judging an optical sensor to be abnormal if the signal level is lower than a prescribed level and checking the operation state of the optical sensor before the optical sensor is in the ready state after power on. CONSTITUTION:When an index sensor 3 is normal, the output level of a light receiving part 3b, and the output of an amplifying circuit 31 is binarized on the basis of the threshold level of a waveform shaping circuit 32 because the output of the circuit 31 has a part higher than this threshold, and a pulse signal output of the waveform shaping circuit 32 which is obtained by binarizing is inputted to an arithmetic circuit 11, and the index sensor 3 is judged to be abnormal by a proper logic utilizing a pulse signal for lamp driving or the like. If the light projecting and receiving face of the sensor 3 is dirty or photoelectric conversion characteristics are degraded, the output of the amplifying circuit 31 is lower than the threshold level, and therefore, the signal from the light receiving part 3b is not inputted to the arithmetic circuit 11, and the index sensor 3 is judged to be abnormal, and an index sensor abnormality flag assigned to a specific bit of a register 11a is set. |
