Shulou(Shulou.com)11/24 Report--

Infrared thermal imager is a very important application in many applications of infrared sensors. from the beginning, it is limited to military high-tech products, and now it has become more and more popular in the industrial and civilian markets.

In the movie "evaporation order," there is a scene in which Schwarzenegger jumps into a bathtub full of water to avoid being pursued by opponents with thermal imagers, in order to keep his temperature consistent with his surroundings, thus trying to mask his own infrared signal source. avoid detection by thermal imagers.

If you want to know why the thermal camera is so magical, you have to start with how it works.

The principle of infrared thermal imager is that all objects above absolute zero (- 273 ℃) emit infrared radiation. The technology of using some special electronic device to convert the temperature distribution of the object surface into an image visible to human eyes and display the surface temperature distribution in different colors is called infrared thermal imaging technology, and this electronic device is called infrared thermal imager.

The infrared thermal imager uses the infrared detector, the optical imaging objective lens and the optical-mechanical scanning system to accept the infrared radiation energy distribution pattern of the measured target to be reflected on the photosensitive element of the infrared detector. Between the optical system and the infrared detector, there is an optical-mechanical scanning mechanism to scan the infrared thermal image of the measured object and focus on the unit or spectrometer detector. The detector converts the infrared radiation energy into an electrical signal. After amplification, conversion or standard video signal, the infrared thermal image is displayed through the TV screen or monitor.

This kind of thermal image corresponds to the thermal distribution field of the object surface, but because the signal of the infrared radiation distribution map of each part of the measured object is very weak, compared with the visible image, it lacks hierarchy and stereoscopy. in order to judge the infrared thermal distribution field of the measured target more effectively, some auxiliary measures are often used to increase the practical functions of the instrument, such as image brightness and contrast control. Real standard correction, pseudo color drawing contours and squares for mathematical operation and processing, etc.

It should be noted that the thermal image and visible image of the same target are different, it is not the visible image that can be seen by the human eye, but the temperature distribution image of the target surface, that is to say, the infrared thermal image is the thermal image that the human eye can not directly see the surface temperature distribution of the target, and becomes the thermal image that can be seen by the human eye.

The composition of the infrared thermal imager 5 parts of the infrared thermal imager package:

1. Infrared lens: receiving and concentrating the infrared radiation emitted by the measured object.

2. Infrared detector assembly: change the thermal radiation type into an electrical signal

3. Electronic components: processing electrical signals

4. Display components: convert electrical signals into visible images

5. Software: process the collected temperature data and convert them into temperature readings and images.

Classification of infrared thermal imagers infrared thermal imagers are divided into refrigerated and uncooled according to working temperature.

Refrigerated thermal imager: a cryogenic cooler is integrated in the detector, which can cool the detector so that the thermal noise signal is lower than the imaging signal and the imaging quality is better.

Uncooled thermal imager: its detector does not need low temperature cooling, and the detector used is usually based on microbolometer, mainly polysilicon and vanadium oxide detectors.

According to the function, infrared thermal imager can be divided into temperature measurement type and non-temperature measurement type.

Temperature-measuring infrared thermal imager: temperature-measuring infrared thermal imager, which can directly read the temperature value of any point on the surface of the object from the thermal image. This system can be used as a nondestructive testing instrument, but the effective distance is relatively short.

Non-temperature infrared thermal imager: non-temperature infrared thermal imager can only observe the difference of thermal radiation on the surface of the object. This system can be used as an observation tool with a long effective distance.

Compared with the general detection equipment, the infrared thermal imager has the following distinct characteristics:

1. The thermal imager can measure the temperature of moving objects, but it is difficult for ordinary temperature measuring instruments to do this.

2. The temperature of a target of several microns or even smaller can be measured with the help of a microscopic lens.

3. The thermal diagnosis of the equipment can be done quickly.

4. It will not interfere with the measured temperature field.

5. The range of temperature measurement is wide. According to the type, the range of 0 ℃-2000 ℃ can be measured.

6. It has high sensitivity and can distinguish 0.1 ℃ or less temperature difference according to different model.

7. Safe to use. Because of the non-contact of the measurement, the thermal imager is very safe to use.

The development of infrared thermal imager in 1800 years, the British astronomer F.W. Herschel found infrared.

In the 1970s, thermal imaging systems and charge-coupled devices were successfully applied.

At the end of the last century, infrared devices represented by focal plane array (FPA) were successfully applied.

The core of infrared technology is infrared detector. According to its characteristics, infrared detector can be divided into four generations:

The first generation (1970s-80s): optical serial / parallel scanning imaging is mainly carried out with units and multiple devices.

The second generation (1990s-2000s): the scanning focal plane represented by 4x288

The third generation: staring focal plane

The fourth generation: the developing system chip, which is mainly characterized by large area array, high resolution, multi-band and intelligent dexterity, has the function of high-performance digital signal processing, and even has the ability of single-chip multi-band detection and recognition.

At present, the mainstream technology of uncooled focal plane detector is thermistor micro-bolometer, which can be divided into vanadium oxide detector and amorphous silicon detector according to the different thermistor materials used.

With the development of uncooled focal plane array detectors, its performance can meet some military applications and almost all civilian fields, and truly achieve miniaturization, low price and high reliability. it has become a promising and market potential development direction in the field of infrared detection and imaging.

Advantages and disadvantages of infrared thermal imager advantages of infrared thermal imager

1. Infrared thermal imaging technology is a kind of passive non-contact detection and recognition with good concealment.

Because the infrared thermal imaging technology is a kind of passive non-contact detection and recognition of the target, it has good concealment and is not easy to be detected, which makes the operator of the infrared thermal imager safer and more effective.

2. Infrared thermal imaging technology is free from electromagnetic interference and can accurately track thermal targets from a long distance and accurately guide them.

Because the infrared thermal imaging technology uses thermal infrared, it is not subject to electromagnetic interference. The infrared search and tracking system using advanced thermal imaging technology can accurately track thermal targets from a long distance and track multiple targets at the same time to maximize the effectiveness of weapons.

Infrared thermal imaging technology can be used for accurate guidance, so that guided weapons have high intelligence and the ability to do nothing after launch, and can be destroyed by finding the most important targets, thus greatly improving the hit accuracy of ammunition and increasing its combat power by dozens of times.

3. Infrared thermal imaging technology can really achieve 24-hour all-weather monitoring.

Infrared radiation is the most widespread radiation in nature, while the atmosphere and smoke clouds can absorb visible light and near infrared, but it is transparent to infrared rays of 3 ~ 5 μ m and 8 ~ 14 μ m. These two bands are called infrared "atmospheric windows".

Therefore, using these two windows, the target to be monitored can be clearly observed in a completely dark night, or in a harsh environment covered with rain, snow and other clouds. Because of this characteristic, infrared thermal imaging technology can really achieve 24-hour round-the-clock monitoring.

4. Infrared thermal imaging technology has strong detection ability and long distance.

The detection ability of infrared thermal imaging technology is strong, and it can be observed beyond the range of enemy defense weapons, and its effect is far away.

At present, hand-held thermal imagers and thermal imagers installed on light weapons can allow users to see clearly the human body above 800m; and aim and shoot at a distance of 2cm 3km; observe the water surface on warships up to 10km; find the activities of individual soldiers on the ground on helicopters with high 1.5km; find people on the ground and moving vehicles on high 20km reconnaissance planes, and analyze changes in sea water temperature to detect underwater submarines.

5. Infrared thermal imaging technology can use a variety of display methods to increase human senses from five to six.

Only when the temperature of the object reaches more than 1000 ℃ can visible light be seen by the human eye. And all objects with temperatures above absolute zero (- 273 ℃) will constantly emit thermal infrared. For example, the thermal infrared energy emitted by a normal person is about 100W.

These are invisible to the human eye, but the thermal radiation energy of the object is directly related to the temperature of the surface of the object. This characteristic of thermal radiation enables people to use infrared thermal imaging technology for non-contact temperature measurement and thermal state analysis of objects, and can be displayed in a variety of display modes.

If the video signal is processed in false color, the thermal images of different temperatures can be displayed by different colors; if the inverse video signal is processed by analog-to-digital conversion, the temperature values of each point of the object can be displayed digitally, so as to see clearly what is invisible to the human eye. So it can be said that infrared thermal imaging technology increases the number of human senses from five to six.

6. Infrared thermal imaging technology can directly display the temperature field of object surface, which is not affected by strong light and is widely used.

The infrared thermometer can only display the temperature value of a small area or a certain point on the object surface, while the infrared thermal imager can measure the temperature of each point on the object surface at the same time, directly display the temperature field of the object surface, and display it in the form of an image.

Because the infrared thermal imager detects the infrared thermal radiation energy of the target object, it does not appear halo or turn off when the low light level is in the strong light environment like the intensifier, so it is not affected by the strong light.

In addition to the main military applications, infrared thermal imaging technology can also be widely used in civil fields such as industry, agriculture, medical treatment, fire protection, archaeology, transportation, geology, public security reconnaissance and so on. Moreover, this technology can be widely applied to the field of security monitoring to facilitate the realization of intelligent security monitoring.

Disadvantages of infrared thermal imager:

1. The image contrast is low, and the ability to distinguish details is poor.

Because the infrared thermal imager relies on the temperature difference to image, but the general target temperature difference is not large, so the infrared thermal image contrast is low, which makes the detail resolution worse.

2. You can't see the target through transparent obstacles, such as window glass.

Because the infrared thermal imager relies on the temperature difference to image, and transparent obstacles such as window glass, the infrared thermal imager can not detect the temperature difference of the subsequent object, so it can not see the target clearly through the transparent obstacle.

3. High cost and high price

At present, the cost of infrared thermal imager is still the biggest factor that limits its wide use, but with the emergence of uncooled infrared focal plane array, it provides an effective means to obtain high resolution and high reliability devices at low cost. With the development of science and technology, the breakthrough of key technologies, and the improvement of processing efficiency, the cost will be greatly reduced in the future.

4. It is impossible to achieve long-distance monitoring, and the monitoring screen can only distinguish whether there are suspicious people entering, but can not clearly see the face and appearance features.

Infrared thermal imager is widely used in both military and civilian fields. With the maturity of thermal imaging technology and the advent of a variety of low-cost thermal imaging cameras suitable for civilian use, it plays a more and more important role in all sectors of the national economy.

In industrial production, many equipment are often used in high-temperature, high-pressure and high-speed operation. Infrared thermal imager is used to detect and monitor these equipment, which can not only ensure the safe operation of the equipment, but also find abnormal conditions in order to eliminate hidden dangers in time.

At the same time, the use of infrared thermal imager can also carry out industrial product quality control and management. In addition, infrared thermal imager has important applications in many fields, such as medical treatment, public security, fire protection, archaeology, transportation, agriculture, geology and so on.

Such as building heat leakage search, forest fire detection, fire source search, sea rescue, ore fracture discrimination, missile engine inspection, public security reconnaissance and non-destructive inspection of various materials and products, etc.

After years of development, infrared thermal imaging technology has expanded from its main military purpose to a wide range of civilian fields, such as industrial monitoring and temperature measurement, law enforcement and drug detection, security and criminal prevention, medical and health, remote sensing, equipment early fault diagnosis and maintenance, maritime rescue, astronomical detection, night vision enhanced observers for vehicles, aircraft and ship drivers, and so on. Infrared thermal imaging technology is moving towards glory. Play a role in the current struggle against novel coronavirus.

This article is from the official Wechat account: sensor Technology (ID:WW_CGQJS). Author: sensor Technology.

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