| 摘要 |
PURPOSE:To rapidly check the action of a photosensor in a short waiting time previous to regular detection by interposing a liquid crystal board at a middle position between a light receiving part and a light emitting part which is in an on-state at the time of checking, changing the light transmissivity of the liquid crystal board and measuring the output of the photosensor in accordance with the change. CONSTITUTION:The light emitting part 1 is turned on/off by a driving circuit 4 and the light transmissivity of the liquid crystal board 3 is changed by a control circuit 6. An output signal from the light receiving part 2 is outputted to the outside through an output circuit 5. At the time of checking, the action of the light emitting part 1 already being in the on-state is stable and the light transmissivity of the liquid crystal board 3 is changed with almost no waiting time, so that the output from the light receiving part 2 through the output circuit 5 in accordance with the change of the light transmissivity of the liquid crystal board 3, that means, the output from the photosensor is directly stabilized. Whether the action of the photosensor is normal or abnormal is confirmed without waiting time. Since the light emitting part need not be turned on/off at the time of checking, the waiting time required for stabilizing the output is unnecessary and the regular detection is started earlier by as much as the unnecessary waiting time. |
