The important function of photoelectric switch sensor is to deal with the change of light intensity: using optical elements to change the light beam in the middle of the media; Use light beams to reflect objects; Make the beam return instantaneously after a long distance. Photoelectric sensor switch is composed of transmitter, receiver and detection circuit. The transmitter aims at the target and emits a beam, which generally comes from light emitting diodes (LEDs) and laser diodes. The beam emits continuously, or changes the pulse width. The radiation intensity of the pulse modulated beam is selected many times in the emission and does not run indirectly towards the target. The receiver is composed of photodiode or photoelectric triode. In front of the receiver, optical elements such as lens and aperture are installed. Behind it is the detection circuit, which can filter out the effective signal and apply the signal.