Retro-reflective sensor: How they work
Transmitter and receiver units are located in the same housing and form a retro-reflective sensor in combination with a reflector. The emitted light hits the reflector and is reflected back to the receiver. If the light signal is interrupted by an object, a switching operation is tripped. The receiver of retro-reflective sensors from autosen comes with a polarisation filter. This is why the retro-reflective sensor only works in combination with the appropriate reflector (prismatic reflector) because it reflects back the light being polarised. The decisive advantage is that reflecting surfaces in the surroundings will not cause undesired switching of the sensor.
Retro-reflective sensor: Advantages and disadvantages
The retro-reflective sensors require more installation expenditure because the sensor and prismatic reflector have to be aligned appropriately. The range does not depend on the degree of reflection, shape, colour and material of the object. Transparent objects cannot be detected by simple light barriers. Retro-reflective sensors are used for mean distances up to 5 m.
Retro-reflective sensor for transparent objects
The optical retro-reflective sensor AO701 from autosen is a special version and suitable to reliably detect transparent films and objects. Common retro-reflective films do not switch if a transparent object is located between transmitter and receiver because the light is not completely weakened by the object. In addition to the reflected light, the optical sensor AO701 also detects the light intensity. That way it is also possible to reliably detect transparent objects weakening the emitted light only. The sensor is so sensitive that even thin films and clear glass are reliably detected.