Everyone knows about the human body sensing module, but do you know how human motion is sensed by sensors?

Human body sensing module is widely used in our daily life. For example, when we enter the bank ATM, the system sends out warm and safe reminders, the doors of high-level places will automatically open, the lights will automatically turn on when we return home, the burglars will immediately interact with the alarm when they break in illegally, and so on. Many people can send corresponding signals without human control. The human motion sensor and Fresnel lens are indispensable to the scene realization of corresponding actions.

Any heating body will produce infrared rays. The human body emits far infrared rays at all times, and absorbs far infrared rays at all times. According to the measurement, the far infrared wavelength emitted by human body is near 9.6 micron. Now the widely used mobile infrared sensor relies on detecting the infrared radiation emitted by human body.

The control element of human body induction is pyroelectric infrared sensor, which detects the infrared energy change of human body radiation in a non-contact form. It detects infrared radiation by using the characteristics of temperature change, and thus detects the human body's proximity.

Pyroelectric infrared sensors only allow infrared light to pass through a specific wavelength range. In other words, they only work on the human body or objects whose body temperature is similar to human body, excluding light, sunlight and other infrared radiation. No small animal, mobile phone electromagnetic field, light, etc. will interfere with its sensing.

The pyroelectric infrared sensor is the "eye" and the Fresnel lens is the "glasses" of the sensor
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In the process of infrared energy change induced by pyroelectric infrared sensor, the pyroelectric infrared sensor itself is not "accurate", "Fresnel lens", which plays a vital role in the process of "human motion induction".

One is focusing, which effectively concentrates the infrared radiation of the detection space on the sensor, and limits the range of infrared radiation of the human body to the peak wavelength of the incident light. When the Fresnel lens is not used, the detection radius of the sensor is less than 2 meters. When the Fresnel lens is added, the detection radius of the sensor can reach 12 meters.

& nbsp; secondly, the detection area is divided into several bright and dark areas, so that moving objects / people entering the detection area can produce pyroelectric infrared signals in the form of temperature changes on pyroelectric infrared sensors. When no human body moves in the detection area, the pyroelectric infrared sensor only senses the background temperature. When the human body enters the detection area, the pyroelectric infrared sensor senses the difference between the human body temperature and the background temperature. After the signal is collected, it is compared with the existing detection data in the system and judges whether it really exists or not. Human and other infrared sources enter the detection area.

In the research and development and production of Fresnel lens, Shandong Yuying has been focusing on the production and development of Fresnel lens since 1992. It is one of the professional production and supply enterprises of Fresnel lens.

Compared with other lenses, Fresnel lens has the advantages of small size, light weight, compact structure, good focusing and imaging performance, and has great economic applicability. Therefore, it has been widely used in smart home, security, projector, LED lamp, solar power generation and other industries.
In terms of shape, Fresnel lens is divided into plane and sphere. Under the circumstance of not strict aperture and aberration, Fresnel lens generally adopts plane structure because of its convenient processing.

The spherical Fresnel lens solves the problem that the sensitivity is not balanced due to the change of focal length. Through precision processing, the focal lengths of the detecting objects with different distances are equal. The detection angle of the Fresnel lens produced by Shandong Yuying can be extended to 180 degrees, which completely avoids the problem of dead angle just below the detector.
Functionally, Fresnel lenses have wide-angle and curtain-type lenses. Fresnel lenses of curtain-type infrared detectors are designed to be symmetrically aligned in vertical rows with serrated teeth. The angle of detection is small. Fresnel lenses of wide-angle infrared detectors are cut into a small piece of multi-layer multi-view area with regular arrangement of shapes by circular cutting. The more the viewing area, the larger the angle of detection.
& nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; < br /> Nowadays, the focal length, including size and shape of each layer of Fresnel lens used in the market are different. Because of the different detection angles, distances and size shapes, in order to ensure that the Fresnel lens meets the customer's requirements, the design of Shandong Yuying will be customized according to the customer's requirements.