With the emergence and development of microelectronics technology, optoelectronic semiconductor technology, optical fiber technology, and grating technology, photoelectric sensor types are also increasing, photoelectric sensors are increasingly used. And photoelectric sensors have other sensors that can not replace the superiority, so it has great prospects for development. The physical basis of the photoelectric sensor is the photoelectric effect, it is composed of photoelectric material devices, both for the detection of non-electricity directly caused by the change in the amount of light, and also can be used to detect other non-electricity can be converted into the amount of light changes.

Photoelectric switch (photoelectric sensor) is the abbreviation of photoelectric proximity switch, which is used to detect the presence or absence of an object by using the blocking or reflection of the light beam by the detected object, and the circuit is selected by the synchronous circuit. The photoelectric switch converts the input current on the transmitter into a light signal to be emitted, and the receiver then detects the target object according to the received light intensity or the presence or absence of light. Most photoelectric switches use infrared light waves with wavelengths close to visible light. Photoelectric switch transmitter mostly uses medium frequency (about 40kHz) narrow pulse currently driven semiconductor light-emitting diode (LED) as the light source, emitting modulated light pulse. Accordingly, the output signal of the receiving photosensitive element (phototransistor) is processed by a 40kHz frequency-selective AC amplifier and a special demodulation chip, which can effectively prevent interference from sunlight and fluorescent lamps, and can reduce the power consumption of the transmitting LED.

Features of photoelectric sensors:

(1) Non-contact measurement can be realized. Photoelectric measurement without direct contact with the object to be measured, the long service life of the sensor, and no damage to the object to be detected.

(2) Color discrimination can be realized. Using the reflectivity and absorption of light by the object to be measured, the color of the object to be measured is detected according to the difference between the wavelength of the light being projected and the color combination of the object to be measured.

(3) High detection accuracy and reliability. High resolution can be achieved by designing so that the light beam can be focused on small light points or by constituting a special light-receiving optical system, which allows the detection of tiny objects and high-precision position detection.

(4) Few restrictions on the object to be measured. The photoelectric sensor detection of objects to detect objects caused by shading, reflection, and direct radiation is the detection principle, so can be detected on almost all objects such as metal, wood, and liquid.

(5) Fast response, high response frequency. Light wood bodies with high-speed characteristics and the sensor circuit are electronic devices constitute, so does not contain mechanical working time, the response time is extremely short, making the frequency of response per unit of time increase.

(6) simple structure, measurable parameters. Generally, there is only a light source, optical path, and photoelectric components. Can achieve the measurement of speed, acceleration, displacement, temperature, concentration, turbidity, and other parameters.