Detecting Shiny, Unfinished Cans

Detecting the presence of shiny or reflective objects is a challenge in many applications where a retroreflective sensor would normally be the ideal solution due to space, cost, convenience or other considerations.

In retroreflective sensing, the sensor is looking for its emitted light returned by the retroreflector. Shiny objects can act as reflectors themselves, returning enough light to the sensor to cause unreliable sensing. A solution is needed that will only see the light returned from the retroreflector, and not light returned from shiny targets.

WORLD-BEAM Q20 polarized retroreflective mode sensors use polarizing filters to detect only the light returned from the retroreflector, ignoring light returned from shiny objects. Natural light is made up of waves having a variety of polarizations. Photoelectric sensors with polarizing filters emit and detect only light waves of a specific polarization while rejecting unwanted light of other polarizations.

In this application, the sensor is designed to see only the light returned from the retroreflector. When the unfinished cans pass between the sensor and the retroreflector, the light reflected off the cans has a different polarization than the light returned by the retroreflector. As a result, the beam will be blocked by the cans and the output will be triggered.