Photoelectric sensor
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![Certain types of smoke detector use a photoelectric sensor to warn of smoldering fires.](/Images/godic/202502/02/Heimrauchmelder4632.jpg")
A photoelectric sensor, or photo eye, is an equipment used to discover the distance, absence, or presence of an object by using a light transmitter, often infrared, and a photoelectric receiver. They are largely used in industrial manufacturing. There are three different useful types: opposed (through beam), retro-reflective, and proximity-sensing (diffused).