In depth analysis of pyroelectric infrared sensors and Fresnel lens technology

1. Principle of Pyroelectric Infrared Sensor:
The pyroelectric infrared sensor uses detection elements made of high thermoelectric coefficient materials to convert infrared radiation into weak voltage signals, which are amplified and processed before being output. The detection components are usually connected in reverse polarity series, so that the received infrared radiation can be converted into detectable electrical signals, which are processed by field-effect transistors and chips to achieve operation.

2. Principle and Characteristics of Fresnel Lenses:
Fresnel lenses utilize special optical principles to create alternating "blind spots" and "high sensitivity zones" in front of the detector, improving detection and reception sensitivity. Lens materials often use polyethylene plastic sheets (HDPE), which are transparent to infrared wavelengths of 7-14um, while human infrared radiation wavelengths are 9-10um, making them suitable for detecting human infrared radiation.

3. Sensitivity of Pyroelectric Infrared Sensors to Working Environment Temperature:
The working temperature range of pyroelectric infrared sensors is wide, but they are highly sensitive to environmental temperature. If the ambient temperature is close to or equal to the radiation temperature of the human body, the sensitivity of the sensor will decrease and it is susceptible to interference. To improve the detection effect, a Fresnel lens is often installed in front of the sensor, which amplifies the signal through a special optical system and increases the detection distance.

4. Application Field:
The combination of pyroelectric infrared sensors and Fresnel lenses is widely used in various fields such as human temperature measurement systems, infrared sensing control systems, smart home sensing systems, industrial automation control systems, etc., playing a key role in improving detection accuracy and stability.