PIR Sensors Lens
PIR sensors are rather generic and for the most part vary only in price and sensitivity. Most of the real magic happens with the optics. This PIR fresnel lens is a pretty good idea for manufacturing: the PIR sensor and circuitry is fixed and costs a few dollars. The lens costs only a few cents and can change the breadth, range, sensing pattern, very easily.
Infrared Fresnel lens is primarily used to transmit infrared light for motion detector use. Passive Infrared PIR Fresnel lenses are molded in a flexible, 0.457mm thick, High Density PE.