付元威

Abstract：infrared sensor is a kind of sensor which realizes the independent detection function by using the infrared radiation characteristic of the object.Visible，invisible，infrared，and radio waves are now considered electromagnetic waves.The difference between these waves is only the wavelength.Below is a spectrum of electromagnetic waves arranged by wavelength，called the electromagnetic spectrum.As is known to all，the progress of infrared technology has a large number of applications in the fields of modern science and technology，national defense，industry and agriculture.The infrared sensor works automatically by taking advantage of the infrared radiation characteristics of the object.The pyroelectric infrared sensor introduced in this paper is one of the most widely used sensors.

Key words：infrared radiation;Electromagnetic wave pattern;The sensor

I.Brief introduction of infrared sensor

（1）Definition of infrared sensor

Infrared sensors use the physical properties of infrared to detect objects.Infrared light，also known as infrared light，has the characteristics of reflection，refraction，scattering，interference and absorption.It is also a light invisible to the naked eye.The spectrum does not belong to the red range in visible light，so it is called infrared spectrum.The position of infrared in electromagnetic spectrum can be divided into near infrared，mid infrared，far infrared and far infrared.All objects，as long as they have a certain amount of heat，can emit infrared.

（2）Principle

The infrared sensor uses the infrared radiation produced by the object to realize the automatic detection of the equipment.

Infrared belongs to invisible light wave，whose wavelength is generally between 0.76-600 m.The infrared region can be divided into near infrared（0.73-1.5 m），mid infrared（1.5-10 m）and far infrared（more than 10 m）.Areas over 300 meters are also known as "submillimeter waves.".In recent years，infrared radiation technology has become a new subject with rapid development.Widely used in production，scientific research，military，medical and other fields.

II.Generation and properties of infrared radiation

Infrared radiation is produced by the movement of molecules in an object.This process of motion is caused by the heat generated by the object.Only at absolute zero，all the molecules of the object are at rest.So at absolute zero，nothing emits infrared light.In addition，the object emits infrared light at normal temperature.Flame，bearing，automobile，airplane，plant，animal and even human body are the sources of infrared radiation.Infrared has the characteristics of reflection，refraction，scattering and dry absorption.The thermal effect of infrared is very large，and the vacuum propagation speed is 3 × 108m / s.

Metal has great attenuation to infrared radiation.Generally，metal materials can not pass through infrared rays;most semiconductor materials and some plastics can emit infrared rays;for example，the infrared transparency of water with a thickness of L（mm）is low.When the thickness reaches LCM，the water is almost completely opaque to infrared.Gas also absorbs infrared radiation in different degrees.For example，the atmosphere（water vapor，carbon dioxide，ozone，methane，etc.）absorbs infrared radiation in different degrees.The more transparent wavelength is 1-5m，the infrared radiation between 8-14m is more transparent，and the transparency of other wavelengths is very poor.However，the inhomogeneity of the medium，the impurity of the crystal material，the impurity or the suspended particle can cause the scattering of the infrared radiation.

III.Classification of infrared sensor system

Infrared sensor system is a measurement system with infrared as the medium.According to its functions，it can be divided into five categories：

Conclusion：because of the advantages of infrared sensor，more and more people use this detector，and the demand for it is also growing.The infrared absorption detection rate is high and the time is short.In addition，with the increase of application，the corresponding wavelength of infrared sensor needs to be increased to make the wavelength of detector longer.According to the above requirements，with the development of microelectronics technology and the continuous expansion of sensor application field，infrared sensor will develop towards the direction of unitization，single function integration and multi-function.In addition，due to its good anti-jamming ability and accurate and reliable target information，the two-color and multi-color detectors will receive more attention in the future.In addition，on the basis of the original detector，the infrared sensor is constantly improved，new materials are developed，and high-density infrared focal plane array is developed.Researchers and scholars in this field are working in these directions.It is believed that with the passage of time，more and more better materials will be used to manufacture infrared sensors，and more kinds of infrared sensors will be used in more extensive fields.

Reference

[1] Bai Yanfei.Understanding of the application status and development trend of infrared sensors in China [J].Taiwan Strait science and technology and industry，2017（04）：95-96

About the author：

[1]Fu Yuanwei（1997），male，Han nationality，Neijiang，Sichuan，bachelors degree，research direction：mechanical and Electronic Engineering