Through-beam sensors & Retro-reflective sensors

Through-beam sensors

Through-beam sensors have transmitter and receiver units that are set apart. The components are mounted in such a way that the beam of light emitted by the transmitter hits the receiver (e.g. phototransistor) directly (cf. Figure 4.6). If an object, workpiece or even a person enters the path between the transmitter and receiver, the light beam is interrupted and a signal is triggered that initiates a switching operation at the output (ON/OFF).

Retro-reflective sensors

In retro-reflective sensors the transmitter and receiver are arranged side-by-side in a housing. The reflector reflects the light beam from the transmitter to the receiver. It is mounted in such a way that the light beam emitted by the transmitter impinges almost entirely on the receiver. If an object, workpiece or even a person enters the path between the transmitter and reflector, the light beam is interrupted and a signal triggered that initiates a switching operation at the output (ON/OFF).