Photosensors & how they work
Photoelectric sensors provide non-contact accurate detection of targets. They emit infrared, red or laser light and the target breaks the light beam or reflects the beam back to the sensor to activate the sensor output. Photoelectric sensing modes are divided into three primary types, those being through-beam, retro-reflective and diffuse. Photoelectric sensors can check for presence, color, distance, size, shape, and many more targets attributes.
Diffuse sensing mode, sometimes referred to as proximity or energetic, uses the reflectivity of the target. Unlike other photoelectric sensing modes, the object reflects the light back to the sensor’s receiver instead of interrupting the light beam to actuate the output.
Retro-reflective sensing mode, occasionally referred to as retro or reflex, requires the use of a reflector or reflective tape to reflect the emitted light back to the receiver. Similar to the through-beam sensing mode, the target must break the light beam to actuate the output.
Through-beam sensors are often the “go-to” photoelectric sensor since no matter what the target object’s color, texture, surface finish, or material, it will be reliably detected. Through-beam sensing mode, sometimes referred to as thru-beam, transmitted beam, opposed mode or beam break, is the oldest photoelectric sensing mode. The light emitter and receiver are in different housings.
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