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Application of Fresnel lens in infrared sensor system

Time:

2020-03-02

Infrared sensor system can be divided into five categories according to its function, which is a measurement system using infrared as the medium . According to the detection mechanism, it can be divided into photon detector and heat detector. Infrared sensor technology has been widely used in modern science and technology, national defense, industry and agriculture and other fields .

Now, infrared technology has been well known. This technology has been widely used in modern science and technology, national defense science and technology, industry and agriculture science and technology. Infrared sensor system is a measurement system with infrared as the medium. According to its function, it can be divided into five categories: ( 1 ) radiometer, which is used for radiation and spectrum measurement; ( 2 ) search and tracking system, which is used to search and track infrared targets, To determine its spatial position and track its movement; ( 3 ) thermal imaging system, which can produce the distribution image of the whole target infrared radiation; ( 4 ) infrared ranging and communication system; (5) hybrid system, which refers to the combination of two or more of the above systems.

It is mainly made of a kind of material with high thermoelectric coefficient, such as lead zirconate titanate series ceramics, lithium tantalate, titanium triglyceride sulfate and so on, which are 2 * 1mm detection elements. One or two detection elements are installed in each detector, and two detection elements are connected in series with reverse polarity, In order to suppress the interference caused by the increase of its own temperature, the infrared radiation detected and received is transformed into a weak voltage signal by the detection element, which is amplified by the field effect tube installed in the probe and then output outwards. In order to improve the detection sensitivity of the detector and increase the detection distance, a Fresnel lens is generally installed in front of the detector, which is made of transparent plastic, The upper part and the lower part of the lens are divided into several equal parts to form a lens with a special optical system. It can amplify the signal by more than 70 decibels in combination with the amplifying circuit, so that the human actions within 10-20 meters can be measured. Now the infrared sensor system with Fresnel lens has be en widely used in many fields, such as: human body temperature sensing, intelligent home system, robot AI field, and so on.

The central wavelength of infrared radiation of human body is 9-10-um, while the wavelength sensitivity of detection element is almost constant in the range of 0.20-um. A window equipped with Fresnel lens is opened at the top of sensor, which can pass through the wavelength range of 7-10-um, which is good for the detection of infrared radiation of human body, while the infrared radiation of other wavelengths is absorbed by Fresnel lens, In this way, an infrared sensor for detecting human radiation is formed.