Automatic three-dimensional parking system has been more and more attention, and gradually become one of the common supporting buildings in the city. It saves space and parking time, and brings more convenience to the city with traffic congestion. In order to ensure the accuracy of the parking position, automatic three-dimensional parking in the parking system placed a lot of photoelectric sensors. The most common types of photoelectric sensors are counter-reflective photoelectric sensors and laser mirror reflective photoelectric sensors with a polarization design. Why is it important to choose a sensor with polarization?

What is the polarization function of a sensor?
It is often said that photoelectric sensors with polarization are more accurate in detecting objects. This is because mirror-reflective photoelectric sensors are prone to malfunction when detecting highly reflective objects because they may not be able to distinguish whether it is light from the object being detected or light reflected from the mirror. Polarizers can easily solve this problem by using the principle of polarization of light.
A polarizer is placed in the sensor. Polarizer is a grid with many slits, only in line with the direction of its polarization of light waves can pass through the corresponding polarization filter on the slit (horizontal filter can only be horizontally polarized light waves, vertical filter can only be vertically polarized light waves). When there is no object to be detected, the reflector will reflect the horizontally polarized light wave and reverse its polarization direction by 90°, so that the returned vertically polarized light wave can pass through the vertically polarized filter in front of the receiver and reach the phototransistor at the receiving end, and the light beam forms a loop. When the detected object passes through, the reflected beam attenuates a lot and the photoelectric switch outputs a signal. If the detected object is glass or mirror, the reflectivity is very strong, and the intensity of the reflected light wave from its glass surface is constant, but the polarization direction of the light wave does not change. The reflected light remains horizontally polarized, and the horizontally polarized light cannot pass through the vertical polarizer in front of the receiver. Thus, since the receiver cannot receive the light wave, the beam circuit is interrupted and the photoelectric switch outputs a signal.

This is because the exterior material of the vehicle usually constitutes a highly reflective object. In order to ensure accurate detection of the vehicle's positional condition, we usually pick a photoelectric sensor with a polarization function. Moreover, reflective photoelectric sensors are easy to install and are more popular among customers.