What is optical sensors?
Answer:
I think, you are talking about the optical sensors for detecting objects.
- Thru beam. The light source shines onto the light detector across the path of the objects that need to be detected (e.g. across a hallway or across a conveyor belt). An object interrupts the beam of light between the source and detector and sets off the sensor.
- Reflective. The detector senses the light reflected from the object of interest. The source doesn’t shine at the detector directly.
- Retroreflective. Just as in the case of thru beam sensor, the light from the source goes across the path of the object. But instead of a detector, there is a mirror on the other side, which reflects the light to the detector. The latter is located next to the light source. To set off the sensor, the object of interest interrupts the direct beam from the source, the reflected beam from the mirror or both.
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They are the sensors which are able to detect radiation in the visual spectrum - light energy - (your eye is a good example of an optical sensor). In Earth observation, optical sensors are dependent on having adequate sunlight which reflects off an object (the Earth) in order to for the sensor to pick it up. Its performance is restricted in the presence of clouds, fog, smoke or darkness.An optical sensor detects the intensity or brightness of light.
Thru-Beam Sensor
The photocell paired with a pointer laser makes a thru-beam sensor. The Thru-beam can be use to detect if a body has crossed into an area; a passing body interrupts the laser beam aimed at the photocell and the light intensity drops (resistance value of the photocell increases). The micro-controller is programmed to trigger an event when input from the photocell drops below a determined value.
Optical Reflective Sensor
Optical reflective sensor is a kind of photo-reflective sensor which can accurately determine the object position and a micrometer resolution. It is designed for short distance sensing and is independent of object reflectivity and ambient light. The key features of the sensor components include small size measuring (only less than 10mm in each dimension) and light in weight, which enable the mounting on fast moving parts
Retro-reflective sensors
With the emitter and receiver in the same housing this sensor transmits a pulsed infrared or red light beam which is reflected back from a "triple prism" reflector or reflective tape. The sensor switches when the light beam is interrupted. These devices recognize objects independent of their surface qualities, as long as they are not too shiny.
For a retroreflective sensor, transmitter and receiver are integrated into one housing. The reflector directs the light beam back to the receiver. A reflector is mounted opposite to the sensor and returns transmitted light back to the receiver. Compared to a thru-beam application, retroreflective sensors are used for medium range or average excess gain applications.When the target is directly in front of the reflector, it must be at least as large as the reflector. Smaller objects can be detected if they are located closer to the sensor and they are at least as large as the optics.
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