Object detection on conveyor

Object presence detection by photoelectric sensor.

There is a light emitter that emits light and a light receiver that receives light, and an object is detected by shutting the light.
This is the most stable and reliable method for detecting objects other than transparent objects (opaque objects), but it needs both emitter and receiver.

Light emission and light reception are housed in one case (no need for emitters and receivers), and an object is detected by its light reflection.
However, detection is not stable depending on the material and shape of the object. (Black color, specular surface, cylinder is not stable)

Objects are detected by blocking the reflected light from the retroreflector. Since only the reflected light from the reflector is received, it is not easily affected by the material and shape of the object.
(A technology called polarization is used to prevent the reflected light from the object to be detected.) However, a reflector is required.