8745-2（57＊25）Fresnel lens (flaky)

Fresnel lens (flaky):

8745-2(57*25)

Focal length: 21MM

Distance: 15M

Angle: 180 degrees

Fresnel optical lenses are mostly sheets made of polyolefin material. The surface of the lens is glossy on one side and the concentric circles from small to large are recorded on the other side. The Fresnel lens is equivalent to a convex lens of infrared and visible light in many cases, and the effect is good, but the cost is much lower than that of an ordinary convex lens. Fresnel lenses can be classified according to their optical design or structure. The Fresnel lens has two functions: one is the focusing effect; the other is that the detection area is divided into several bright areas and dark areas, so that moving objects entering the detection area can be in the form of temperature changes in the PIR (Passive infrared detector). ) Changed the pyroelectric infrared signal.