The Fresnel lens is mostly a thin sheet injected with polyolefin material. One side of the lens surface is smooth, and the other side is inscribed from small to large. In many cases, the Fresnel lens is equivalent to a convex lens for infrared sensing and visible light, and the effect is better, but the cost is much lower than the general convex lens.
Fresnel lenses can be classified according to the design or structure of the optical coating. Let me introduce to you two kinds of cognitions about the principle of Fresnel lens, welcome to read!
There are two perceptions of the Fresnel lens principle:
(1) Assuming that the refractive kinetic energy of a lens is only generated in the optical surface layer (for example, the surface of the lens), remove as much optical material as possible while maintaining the curvature of the surface.
(2) A part of the continuous surface layer of the lens "collapses" in one plane. According to the model, its surface is composed of a series of jagged depressions, partially managed by an elliptical arc at the center. The viewing angle varies between each concave and adjacent concave surfaces, but all focus the light somewhere, creating a central focal point, the focal point of the lens. The shape of each depression can be regarded as an independent small lens, and the light source can be adjusted to a parallel surface light or a tungsten filament lamp. The lens also removes some spherical aberrations.
Fresnel lens:
Externally threaded lenses are mostly thin sheets made of polyolefin materials, and are also made of laminated glass. One side of the lens surface is smooth, and the other side is inscribed with inscribed circles from small to large. The texture is based on the interference and interference of light. Its relative sensitivity and acceptance angle require design and production.
Fresnel lenses are usually made of polyethylene plastic products, and the lenses are divided into the same parts according to certain manufacturing methods. The lens has two functions: one is to focus on natural light; the other is to divide the monitored area into bright and dark areas.
When people enter a certain clear area of the monitoring area, the infrared rays emitted by the human body are focused by a part of the lens corresponding to the clear area, and then irradiated on the sensitive element through the filter of the sensor, so that the sensitive element generates a working voltage; When entering the dark area, the infrared rays of the body cannot reach the sensitive element, and the voltage at both ends of the sensitive element changes, that is, the working voltage at both ends of the sensitive element changes with the light; when entering the dark area, the infrared rays of the human body cannot reach the two ends of the sensitive element. The voltage at both ends changes, that is, the operating voltage across the sensitive element changes with light. The frequency of the sensor output signal is related to the speed of movement between clear and dark areas within the monitoring range. The faster you move, the higher the frequency of the output signal. It is assumed that the monitoring range of the human body is fixed and the working voltage output by the sensor is stable.
The above is the content of the two cognitions about the principle of Fresnel lens today. Thank you for your patience in reading! If you want to know more about Fresnel lens, please contact our online customer service, we will answer you in detail.
