Classification and working principle of photoelectric sensors

A photoelectric sensor is a sensor device for detecting an optical signal and converting it into an electrical signal, which can be used for detecting non-electricity such as light intensity, illuminance, radiation temperature measurement, gas composition analysis, etc., which can directly cause changes in light quantity, and can also be used for Detecting part diameter, surface roughness, strain, displacement, etc. can be indirectly converted to non-electricity of light quantity change. Because of its high performance, fast response, non-contact and other characteristics, photoelectric sensors have important applications in industrial automation devices and robotics. Especially in recent years, the generation of image sensors has opened a new chapter for the further development of photoelectric sensors.

How photoelectric sensors work

Photoelectric sensors are mainly composed of three parts: transmitter, receiver and detection circuit. The transmitter is used for aligning a target light beam emitted by a semiconductor light source, a light emitting diode, a laser diode, an infrared emitting diode, etc. The receiver can be further divided into a photodiode, a phototransistor, a photocell, etc., and a lens and an aperture are also mounted in front of the receiver. The optical component is mainly used for receiving the target beam and converting the received optical signal into an electrical signal; the detecting circuit is configured to detect the received electrical signal and filter out the valid signal, and transmit it to the next module to perform the electrical signal. Practical application.

Classification of photoelectric sensors

(1) slot type photoelectric sensor

Mounting a light emitter and a receiver face to face on either side of a slot is a trough optoelectronic. The illuminator emits infrared or visible light, and the optical receiver can receive light in an unobstructed condition. However, when the object to be detected passes through the slot, the light is blocked and the photoelectric switch operates. A switch control signal is output to cut or turn on the load current to complete a control action. The detection distance of the slot switch is usually only a few centimeters due to the limitation of the overall structure.

(2) Optotype photoelectric sensor

If the illuminator and the illuminator are separated, the detection distance can be increased. A photoelectric switch composed of an illuminator and a light collector is called an off-beam split type photoelectric switch, and is simply referred to as an on-beam type photoelectric switch. Its detection range can be several meters or even tens of meters. In use, the illuminator and the light receiver are respectively mounted on both sides of the path of the detection object, and when the detection object passes, the light path is blocked, and the light receiver outputs a switch control signal.

(3) Reflective type photoelectric switch

A reflector-reflective (or mirror-reflective) photoelectric switch is installed in which the illuminator and the illuminator are housed in the same device, a reflector is placed in front of it, and the photoelectric control function is performed by the reflection principle. Under normal circumstances, the light emitted by the illuminator is reflected by the reflector and received by the light receiver; once the light path is blocked by the object, and the light receiver receives no light, the photoelectric switch operates to output a switch control signal.

(4) Diffuse reflective photoelectric switch

Its detector head is also equipped with an illuminator and a light receiver, but there is no reflector in front. Under normal circumstances, the light collector emitted by the illuminator cannot be found. When the detection object passes, the light is blocked, and the light is partially reflected back, and the light receiver receives the light signal and outputs a switching signal.