The working principle of pyroelectric devices is to use the radiation thermal effect to make the detector elements receive radiation energy and cause the temperature to rise, thus changing the temperature dependence performance in the detector. Radiation can be detected by detecting a change in one of the properties. In most cases, radiation is detected by thermoelectric changes. When elements are irradiated and cause non-electric physical changes, the corresponding electric changes can be measured through appropriate transformation.

Some crystals, such as lithium tantalate and triethylene sulfate, will generate equal and opposite charges at both ends of the crystal when heated. 1842, Brewster officially named this polarization phenomenon caused by temperature change as "pyroelectric", that is, pyroelectric effect.

Infrared pyroelectric sensor is a pyroelectric infrared sensor based on pyroelectric effect, with simple and firm structure and stable technical performance. Widely used in infrared detection and alarm, infrared remote control, spectral analysis and other fields, it is the most widely used infrared sensor at present.

The filter of pyroelectric sensor is a band-pass filter, which is packaged at the top of the sensor housing, so that infrared radiation with a specific wavelength can selectively pass through, but infrared radiation that reaches the pyroelectric detector+beyond its cutoff range cannot pass through.

Pyroelectric detector is the core component of pyroelectric sensor, which is made by plating metal electrodes on both sides of pyroelectric transistor and adding polarization, which is equivalent to a flat capacitor with pyroelectric transistor as dielectric. When it is irradiated by infrared light with non-constant intensity, the temperature change changes the charge density of its surface electrode, thus generating pyroelectric current.

Extended data

The driving of pyroelectric emission tube can be divided into two driving modes: level type and pulse type. The pyroelectric emission array constitutes a separate photoelectric sensor. The innovation of the sensor is that it can resist the strong light interference from the outside.

The sunlight contains pyroelectricity that interferes with the pyroelectric receiving tube, which can turn on the pyroelectric receiving diode, causing misjudgment of the system and even paralysis of the whole system. The advantage of this sensor is that it can set up multi-point acquisition, and the spacing and array number of emitter arrays can be selected according to requirements.

Pyroelectric technology has been widely used in speed measurement system, and many products have realized the research of speed measurement and detection by pyroelectric technology. When pyroelectric is used in the field of speed measurement, the most difficult thing to overcome is the interference from many light sources containing pyroelectric, such as strong sunlight. The interference of external light sources has become the bottleneck of pyroelectric application in this field.

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