Retroreflective photoelectric sensors use a separate reflective module located on the other side of the area, span, or object being monitored. This module reflects the emitted light beam back to the transmitter module, which also houses the photoelectric sensor. A reading is then taken at the light source, interpreting the intensity and behavior of the reflected light.
Advantages of retroreflective sensors include:
- A relatively wide operating distance range
- Easier to install and adjust, as only one end of the device requires wiring, and the reflector typically requires no power
- Unaffected by object color or movement
- Ability to detect translucent or transparent objects, as the light beam passes through the object twice
- Limitations of retroreflective photoelectric sensors include potential blind spots at very short ranges and their inability to detect highly reflective objects. The latter is because the amount of light reflected from any mirror-like object makes it difficult for the sensor to detect the object's presence.