What is the principle of photoelectric conversion devices?
The principle of photoelectric conversion a very important class of sensor technology is called light sensor.
Light sensors generally refer to sensors in the ultraviolet to infrared wavelength range, and their types can be classified into quantum detectors and heat detectors. This experiment will introduce a commonly used quantum detector or photon detector, which is a detector made by the photoelectric effect of the material, so it is also called photoelectric converter.
The main parameters are responsiveness (sensitivity), spectral response range, response time, and minimum detectable radiant power. The photoelectric conversion device mainly converts an optical signal into an electrical signal by using a photoelectric effect. Since the discovery of the photoelectric effect, the photoelectric conversion device has been developed by leaps and bounds, and various photoelectric conversion devices have been widely used in various industries. Common photoelectric effect conversion devices include photoresistors, photomultipliers, photocells, PIN tubes, CCDs, and the like.
A photomultiplier is an electrical vacuum device that converts weak input into electrons and multiplies electrons. When the intensity of the optical signal changes, the number of photoelectrons emitted by the cathode changes accordingly. Since the multiplication factor of each dynode increases substantially constant, the anode current also changes with the change of the optical signal, which is a simple working process of the photomultiplier tube.
It can be seen that the performance of the photomultiplier tube is mainly determined by the photocathode, the dynode and the interelectrode voltage. After the photocathode is irradiated with strong light, since the rate of electron emission is high, the inside of the photocathode cannot be replenished with electrons, so the sensitivity of the photomultiplier tube is lowered. If the intensity of the incident light is too high, the current in the device is too large, so that the electrocautery and the dynode are decomposed by the emission, which causes the permanent wave of the photomultiplier tube to be broken. Therefore, when using a photomultiplier tube, direct incident of strong light should be avoided.
Photomultiplier tubes are commonly used to measure weak light signals.
A photocell is a device that converts light energy directly into electrical energy and can be used as an energy device, such as a solar cell used on a satellite. It can also be used as a photoelectron detector.
The photodiode has two types of depletion layer photodiodes and avalanche photodiodes. The vicinity of the semiconductor pn junction region becomes a depletion layer, and both sides of the layer are relatively high space charge regions, and electrons and holes are not normally present in the depletion layer. Carriers (electron-hole pairs) are generated in the depletion layer only when the light illuminates the pn junction, and the carriers are accelerated by the electric field in the junction to form a photocurrent. Photodiodes fabricated using this principle are referred to as depletion layer photodiodes. The depletion layer photodiode has a pin layer, a pn layer, a metal-semiconductor type, a heterogeneous type CCD (Charge Coupled Device), that is, a charge coupled device, and the photoelectric signal on the input surface is converted, stored, and transmitted point by point at the output thereof. The terminal generates a timing signal.
With the advancement of technology, CCD technology has been improved day by day, and has been widely used in security, television, industry, communications, distance education, visual Internet telephony and other fields.