DEVICE FOR SUPERVISING TROUBLE IN LASER BEAM PROJECTING AND RECEIVING APPARATUS

PURPOSE:To prevent misoperation from occurding by projecting laser beam under condition of no existence of a material to be detected, detecting received beam signal and deciding as abnormal at the time of being the prescribed or less. CONSTITUTION:The laser beam L is projected from a laser beam projector 21 and received by a light receiver 23, and the level is detected with a received beam signal level detecting means 36. This is converted into margin for received beam sensibility with laser beam sensibility margin converting means 38 and compared with the preset value with comparison means 40, and at the time of being the preset value or less, trouble alarming display is executed. The margin for sensibility is stored with sample storing means 42, and the data is displayed in order of time with display means 44 and the operator forcasts the timing for exchanging parts and cleaning contamination with the above. As lowering of the received beam sensibility in the laser beam projector is directly detected, the misoperation can be prevented from occurring.