Nowadays, infrared sensor technology is very mature and has been integrated into people’s daily lives and plays a huge role.
Before we understand the infrared sensor, first of all, we should understand what is infrared, or infrared light.
We know that light is also a kind of radiated electromagnetic wave. In human experience, it usually refers to the range of light waves visible to the naked eye from 400nm (violet light) to 700nm (red light) which can be felt by human eyes.
We call the radiation outside the red light and between 760nm and 1mm. Infrared light is invisible to the naked eye, but we can still feel it through some special optical equipment.
Infrared is a kind of light that is invisible to the human eye, so it has all the characteristics of all the light of light. But at the same time, infrared also has a very significant thermal effect. All substances above absolute zero, or -273 ° C, produce infrared light.
Therefore, simply speaking, an infrared sensor is a sensor that performs data processing using infrared rays as a medium.
Type of infrared sensor
According to different ways of sending, infrared sensors can be divided into active and passive.
Working principle and characteristics of active infrared sensor
The transmitter of the active infrared sensor emits a modulated infrared beam that is received by the infrared receiver to form a warning line of infrared beams. When it encounters leaves, rain, small animals, snow, sand, and fog, it should not be alarmed. If a person or a considerable volume of objects is blocked, an alarm will occur.
Active infrared detector technology mainly adopts one-shot and one-receipt, which belongs to linear prevention. Now it has developed from the original beam to multiple beams, and it can also double-shot and double-receive, minimizing the false alarm rate and enhancing product stability and reliability.
Because infrared is a non-coherent environmental factor (for sound, lightning, vibration, various types of artificial light sources and electromagnetic interference sources in the environment, with good incoherence), it is also a product with good coherence of target factors ( The alarm will only be triggered if the target of the infrared beam is blocked, so the active infrared sensor will be further promoted and applied.
The working principle and characteristics of passive infrared sensor
Passive infrared sensors work by detecting infrared rays emitted by the human body. The sensor collects infrared radiation from the outside and collects it on the infrared sensor. Infrared sensors usually use pyroelectric components, which release the charge outward when the temperature of the infrared radiation is received, and an alarm is generated after the detection process.
This sensor is aimed at detecting human radiation. Therefore, the radiation sensitive component must be very sensitive to infrared radiation having a wavelength of about 10 μm. In order to be sensitive to the infrared radiation of the human body, its radiation surface is usually covered with a special filter, so that the environmental interference is obviously controlled.
A passive infrared sensor consists of two pyroelectric elements connected in series or in parallel. Moreover, the two polarization directions are exactly opposite. The environmental background radiation has almost the same effect on the two pyroelectric elements, so that the discharge effect is mutually canceled, so that the detector has no signal output.
Once the intruder enters the detection area, the infrared radiation of the human body is focused by the partial mirror and received by the pyroelectric element, but the two pieces of pyroelectric elements receive different heat, and the pyroelectricity is different, which cannot be cancelled, and is processed by signal. And the alarm.
Infrared sensor application
From the current application situation, the infrared sensor has the following advantages:
1. Environmental adaptability is better than visible light, especially at night and in harsh weather;
2. good concealment, generally passive signal receiving target, more secure than radar and laser detection and confidentiality, not easy to be interfered;
3. The ability to identify camouflage targets is better than visible light due to the detection of infrared radiation characteristics caused by the temperature difference between the target and the background and the difference in emissivity;
4. Compared with the radar system, the infrared system is small in size, light in weight, and low in power consumption.
In recent years, the development trend of infrared sensors is mainly reflected in the following four aspects:
First, the use of new materials and processing technology, the sensor’s infrared detection rate is increased, response wavelength is increased, response time is shortened, pixel sensitivity and pixel density are higher, anti-interference performance is improved, and production cost is reduced. For example, Pyroos and Irisys have introduced a new pyroelectric sensitive technology that combines thin films and ceramics to enable the array of sensitive components.
The second is the large-scale and multi-functional sensor. With the development of microelectronics technology and the expanding application fields of sensors, infrared sensors are developing from small, single functions to large-scale and multi-functional.
Large infrared sensors (16×16 to 64×64 pixels) developed by foreign countries can also be used for temperature field measurement, and can also obtain human body detection functions that are not available in advanced and small infrared sensors (ie, can accurately locate individuals in space). The location in the location, even if people are not active, can be identified) or large-area security monitoring and other functions, it is very suitable for home automation, health care, security protection and other applications.
In addition, the development of new multi-spectral sensors has greatly improved the functionality of infrared imaging arrays.
The third is the intelligence of the sensor. The new intelligent infrared sensor usually has multiple microprocessors, advanced digital signal processing or compensation functions such as Fourier transform and wavelet transform, self-diagnosis function, two-way digital communication and other functions, which make the stability, reliability and reliability of the sensor. The performance of noise ratio and convenience is greatly improved.
Fourth, the sensor is further miniaturized and integrated. Using on-chip integration technology (including blind element replacement, non-uniformity correction, partial image processing functions, etc.) and other new device structures and new manufacturing process technologies, in MEMS (Micro Electro Mechanical Systems), and even NEMS based on nanotechnology Driven by electromechanical systems, the size of infrared sensors is greatly reduced, power consumption is greatly reduced, and integration is significantly improved.
Due to the superior performance of infrared sensor, many mainstream instrument research units and manufacturers are increasingly investing in R&D.
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