Fresnel lens, also known as threaded lens, Fresnel lens is mostly made of polyolefin material, the surface of the lens is smooth, and the other side is filled with concentric circles from small to large. Its texture is designed to utilize the interference of light and to be based on relative sensitivity and acceptance angle requirements. The quality requirement of the lens is very high. A good lens must have a smooth surface, clear texture. Its thickness varies with the application and normally about 0.6 mm. The lens characteristics are wider surface, thinner and farther detection distance.
There are two functions of Fresnel lens: one is the focusing effect; the other is to divide the detection area into several bright and dark areas, so that the moving object entering the detection area can produce the change of heat release on the PIR in the form of temperature change. It is what we called Infrared signal. We can say that fresnel lens help to strengthen the infrared signal and to make PIR work well.
The Fresnel lens is a convex lens that is equivalent to infrared and visible light in many cases, and the effect is better, but the cost is much lower than that of a conventional convex lens. It is often used in applications where accuracy is not critical, such as slide projectors, thin film magnifiers, infrared detectors, etc.
Normally the lens’ shapes are dome and flat. But these years as the smart home is more and more popular, different lens are needed to match with different controllers. Senba can help customers to design and mould the lens they want.