Working Principle and Industrial Application of Infrared Thermal Imager

Infrared thermal imagers are gradually being used in civilian applications. If you still think that thermal imagers are high-end professional equipment and military equipment, and that they are still far away from us, I'm sorry, you're out of date! Thermal imagers in our impression often appear in specialized operations such as military reconnaissance and navigation operations, but now, the application of thermal imagers is almost everywhere around us. In recent years, with the development and popularization of handheld infrared thermal imagers, they have gradually transformed from military professional precision instruments into portable, intelligent, and even civilian popular products with built-in Wi-Fi/cloud thermal imaging. If you are worried about where the water pipe is leaking, where the mobile phone or TV screen has bad pixels, or where there is inflammation in the body, I can tell you with surprise: handheld thermal imagers can solve such problems in one stop, and can also be uploaded to the cloud for storage and big data management. Similarly, many industries are also changing due to the popularity of thermal imagers: for example, if firefighters have a handheld thermal imager, they can accurately determine the location of the fire point and the location of the trapped people; for example, when an earthquake occurs, if the drone is equipped with a thermal imager, it can rush through many obstacles in the first time, find out the situation in the disaster area, and find the trapped people immediately, and the situation that the first batch of rescuers can only "feel the way by feeling the stones" will not happen again, delaying the best rescue time; for example, from ordinary stores or families to countries, the security system uses thermal imagers to accurately determine whether there are unsafe factors; for example, in the process of producing and processing products, many tests that cannot be observed with the naked eye and ordinary instruments have limited accuracy, if there is a thermal imager, then all problems will be "clear at a glance". The application of infrared thermal imagers is now in every corner of our lives, from common medical imaging to spectral detection around us, from food detection that we are gradually understanding to radar modeling used in the military, from the most familiar daily safety inspections to the upcoming autonomous driving and smart life.

FLUKE visual infrared thermometer VT02 is a detection tool for electricians and maintenance technicians. Industrial application scenarios of infrared thermal imagers Perhaps you are not familiar with the industrial applications of infrared thermal imagers. The following is a brief introduction to the application of infrared thermal imagers in industrial automation: Infrared thermal imagers can play an irreplaceable role in five applications, including automated inspection, process control, condition monitoring, fire prevention and monitoring, and continuous optical gas imaging.

Food production line quality control Car windshield defrosting inspection

Controlling the positioning of pipes in automated welding machines Thermal inspection of high-voltage equipment

Hot spots on the ladle indicate possible faults. Continuous monitoring of the warehouse

Detection of fire risk in waste silos Excessive temperature in transformers

Infrared thermal imagers have great development potential and have entered a golden period of development. The development of infrared thermal imaging was once mainly driven by national defense applications, and the latest products were also mainly used in military products. Ten years of development have almost made this phenomenon a thing of the past. Today, the wide application of thermal imaging in firefighting, PVS, maritime, drones, robots, smart buildings, smart homes, and smart stores has made the application prospects of infrared sensors in business very optimistic. Take FLIR, the leader in the thermal imaging market, for example. In the three years since 2015, FLIR has shipped a total of 1 million Lepton movements, which have been integrated into more than 20 products (Lepton is a key infrared movement that has brought great success to FLIR); at the same time, FLIR has opened up a smart strategy to introduce uncooled infrared imaging technology into a wide range of products for various applications, so that uncooled infrared imaging technology can be more widely used and win a larger market. As far as China is concerned, the infrared thermal imaging industry is a high-tech industry with broad development prospects. According to incomplete statistics, the potential demand for infrared thermal imaging technology in my country can reach 50-60 billion yuan, and the current market situation is only in its infancy. By 2020, the infrared imaging market will grow by more than 20%. Domestic leading companies such as Guide Infrared, Dali Technology, SAT Infrared, and Hikvision have also developed rapidly in the past decade, and new products and applications have kept pace with the times. How does an infrared thermal imager work? Infrared thermal imaging is a technology that can convert infrared images into thermal radiation images. This technology can read temperature values ​​from images and is a non-destructive testing technology. Infrared thermal imagers are high-tech products used to detect infrared radiation from target objects and convert temperature distribution images of target objects into video images through photoelectric conversion, electrical signal processing and other means. So how does an infrared thermal imager work? 1. The working range of infrared thermal imagers In nature, any object with a temperature higher than absolute zero (-273°C) can radiate electromagnetic waves. Infrared rays are the most common form of electromagnetic waves in nature. It is a kind of energy, and this energy is invisible to our naked eyes. Any object under normal circumstances will have its own molecules and atoms moving irregularly and continuously radiating thermal infrared energy.

Working spectrum of infrared thermal imager Infrared is part of these electromagnetic waves. Together with visible light, ultraviolet light, X-rays, gamma rays and radio waves, it constitutes a complete and continuous electromagnetic spectrum. As shown in the figure above, electromagnetic radiation with a wavelength range of 0.78μm to 1000μm is called infrared radiation. Infrared radiation electromagnetic waves propagate in the air and are absorbed by the atmosphere, causing the radiation energy to be attenuated. If too much energy is absorbed, it cannot be observed using a thermal imager. The absorption of infrared by the atmosphere, smoke and clouds is also related to the wavelength of infrared radiation. It is transparent to 3~5μm and 8~14μm infrared rays. Therefore, these two bands are called "atmospheric windows" of infrared rays. Using these two windows, infrared thermal imagers can observe in a normal environment without causing infrared radiation attenuation. 2. Thermal imaging principle In layman's terms, infrared thermal imaging is the process of turning invisible infrared radiation into visible thermal images. The radiation capacity of different objects and even different parts of the same object and their reflection strength of infrared rays are different. By utilizing the radiation differences between the object and the background environment and the radiation differences between the various parts of the scene itself, the thermal image can present the radiation fluctuations of each part of the scene, thereby showing the characteristics of the scene. The thermal image is actually an image of the temperature distribution on the target surface. 3. Composition of infrared thermal imager The basic working principle of infrared thermal imager is: infrared rays pass through a special optical lens and are absorbed by the infrared detector. The detector converts the infrared signals of varying strengths into electrical signals, which are then amplified and processed to form a thermal image that can be observed by the human eye and displayed on the screen. The thermal imager consists of two basic parts: the optical system and the detector.

Schematic diagram of the working principle of infrared thermal imagers Thermal imagers are very sensitive and can detect temperature differences of less than 0.1°C. For example, FLIR infrared thermal imagers can identify temperature changes as subtle as 0.02°C. They have advanced detection technology and advanced mathematical algorithms and can accurately measure the temperature of objects from -40°C to +2000°C. 4. Classification of infrared thermal imagers* According to the working temperature, they can be divided into cooled and non-cooled types. Cooled thermal imagers have a low-temperature refrigerator integrated in their detectors. This device can cool the detectors to make the thermal noise signal lower than the imaging signal and improve the image quality. Uncooled thermal imagers do not require low-temperature refrigeration for their detectors. The detectors used are usually based on microbolometers, mainly polysilicon and vanadium oxide detectors.

Cooled thermal imager (left) and uncooled thermal imager (right) imaging effects* According to the function, it can be divided into temperature measurement type/non-temperature measurement type. Temperature measurement infrared thermal imager 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 non-destructive testing instrument, but the effective distance is relatively short. Non-temperature measurement infrared thermal imager can only observe the difference in thermal radiation on the surface of the object. This system can be used as an observation tool with a relatively long effective distance.

Thermal image with temperature information Thermal image without temperature information The heart of the infrared thermal imager - infrared detector Infrared detectors can be divided into: infrared photon detectors and infrared heat detectors based on the detection mechanism.