Patent ID: 7244917

Claim:
A photoelectric switch, comprising: a projection head having a light projecting device for projecting a sensed light to a sensing area; a controller having a controlling portion provided separately from the projection head, for controlling a light projected from the light projecting device and executing a sensing operation based on sensing information of a light receiving device that receives a light from the sensing area of the light projecting device; and a head cable for connecting electrically the projection head and the controller; wherein the projection head includes a monitoring light receiving device for receiving a part of a light that the light projecting device emits, and a projected light quantity controlling device for executing a control such that a monitor signal obtained by the monitoring light receiving device is kept constant to maintain a quantity of projected light of the light projecting device at a predetermined value, and the controlling portion of the controller senses an abnormality of the projection head based on the monitor signal obtained from the monitoring light receiving device to be monitored via the head cable, and suppress the light projected from the light projecting device.