YY-4315 Fresnel PIR Sensor Lens with 8.5m distance 360 degree detect range
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Fresnel PIR lens has two functions: 1. It is the focusing effect, that is, the pyrolysis infrared signal is refracted (reflected) on the PIR. 2. The detection area is divided into a number of bright areas and dark areas, so that the moving object entering the detection area can generate a modified pyroelectric infrared signal on the PIR in the form of temperature change.
Fresnel lenses play a dual role in Passive Infrared (PIR) sensors. Firstly, they focus the thermal infrared signal onto the PIR sensor. Secondly, they divide the detection area into distinct bright and dark zones. This segmentation allows moving objects to generate thermal infrared signals on the PIR sensor when entering the detection area.
Origins and Structure
The concept of Fresnel lenses originates from the work of French optophysicist Augustin-Jean Fresnel. These lenses, typically 0.5mm thick, feature engraved concentric circles that vary in size and depth, creating a serrated profile. The concentric circles have large induction angles and long focal lengths, with the depth of the circular arc recording adjusted for different focal points.
Concentric Ring Arrangement
Infrared light becomes more concentrated and intense as it passes through the concentric rings of the Fresnel lens. Each row of concentric rings forms a vertical sensing area, while horizontal sensing sections are established between the rings. The number of vertical induction zones determines the vertical induction angle, and the length of the lens affects the number of sensing segments and the horizontal sensing angle.
Impact on Motion Detection
The number of sections in the Fresnel lens directly impacts the detection of human body movement. More sections result in smaller movement amplitudes, while fewer sections lead to larger movement amplitudes. By interlacing concentric circles in different areas, blind spots between sections are minimized, enhancing the overall detection performance of the sensor.
Classification and Varieties
Due to the limitations of the infrared probe's field of view angle, the vertical and horizontal sensing angles of the Fresnel lens are constrained. Fresnel lenses are categorized based on their appearance as long, square, or circular, and based on their function as single-zone multi-segment, double-zone multi-segment, or multi-zone multi-segment lenses. Each type offers specific advantages in effectively detecting and responding to thermal infrared signals.
Product classification of Fresnel PIR lens
Fresnel infrared sensor lens produced by our company is divided into five series according to the appearance and size.
1. Helical series below Φ30mm ----Easy to install, easy to conceal
2. Φ30mm or more hemispherical series ----- mostly used for ceiling lamps, large sensing angle
3. square sheet series ------ mostly used in security series, long sensing distance, large horizontal sensing angle
4. circular sheet series ----- mostly used for infrared thermometer, small diameter, small focal length
5. special shape series ------ customer special requirements open mold
