Infrared Thermal Imaging Technology
Since objects above absolute zero emit infrared light, infrared thermal imaging technology is by absorbing the infrared light radiated by the target object, and then converting the light signal into an electrical signal, that is, the infrared radiation invisible to the naked eye is converted into a visual image.
Meanwhile, there are three infrared atmospheric windows including 1 to 3um (short wave), 3 to 5um (medium wave) and 8 to 14um (long wave).
Infrared thermography usually works in two wavelengths:mid-wave infrared and long-wave infrared. The technology is widely used invarious fields and has the following characteristics.
(1) A wide temperature measurement range, usually -170 to2000°C (or need to add a filter).
(2) High detection accuracy that it can resolve thetemperature of less than 0.1 ℃.
(3) Short response time, and the temperature field of theobject can be measured within a few seconds.
(4) It can be used to measure small targets or point targetobjects.
(5) It is a passive measurement and will not destroy themeasured temperature field (temperature measurement distance can be near orfar, ranging from a few centimeters to astronomical distance).
Application of infrared thermal imager in the civil field
Infrared imaging can be applied to infrastructure construction, urban management, industrial production, traffic control, resource exploration, inspection and quarantine and fire security, etc. The market demand is vast. Due to the wide range of applications and the great convenience it provides for production life, the market demand for infrared imaging is likely to maintain a continuous and stable growth in the future. In addition to the traditional application industry, there will be more emerging market demand to become the infrared imaging market growth point.
Currently, the application of infrared thermal imaging technology is becoming more and more popular, involving electric power, security, border defense, industry, oil, construction, transportation, outdoor, civil aviation, automation and many other fields.
The electric power industry is currently the most mature and stable application in the field of preventive inspection. As the most effective means of online power inspection, infrared imaging technology can quickly overhaul power equipment, thus effectively reducing the time cost of equipment maintenance and improving the reliability of equipment operation.
There are many advantages of using infrared thermal imaging for power inspection: far away from the equipment, strong safety; non-contact temperature measurement, does not affect the operation of equipment; fast scanning speed, saving time; wide range of temperature measurement, high accuracy; monitoring in place, can accurately find equipment defects. Important areas of power generation, distribution and substations can be equipped with high-end infrared imaging monitoring equipment, as shown in Figure 1.
▲Figure 1: Application of infrared thermal imaging technology in the field of electronic power
Many important equipment in the petrochemical field need to work in high temperature and high-pressure environment, which is prone to produce safety hazards. According to the safety production requirements, they need to be monitored in real time to eliminate hidden dangers in time. The use of infrared thermal imaging technology can detect corrosion, rupture, thinning, blockage and gas leakage of product transfer and piping, refractory and insulation materials, various reactors, etc., so as to collect relevant detection information.
Refineries using thermal imaging technology can detect safety hazards such as catalytic cracking units, reactor tail gas equipment and furnaces, leakage of safety valves and condensate valves, and exposed and shallowly buried underground pipelines, etc., which can be quickly and accurately identified and located at an early stage, as shown in Figure 2. The application of these technologies is very effective in preventing accidents and reducing energy consumption.
Early gas leak detection methods used mechanical probes that required close contact or proximity to the inspected target. Detectors may be exposed to unseen harmful chemicals, and this detection method has special requirements for detection environmental conditions, which is not conducive to real-time detection. With the continuous progress of infrared technology, gas leak monitoring technology based on infrared thermal imager will also gradually become popular. Infrared thermal imager can visualize the leaking gas using images, so that the leak point can be locked in real time and quickly.
▲Figure 2: Application of infrared thermal imaging technology in petrochemical industry
Forest fire prevention and environmental monitoring
Information on the surface temperature of an object can be extracted and quantified from the target image observed by an infrared thermal imager. Using this feature can be applied to the field of fire prevention. As shown in Figure 3, in a large area of forest, an inconspicuous hidden fire can easily cause a major fire, which is difficult to detect in time by manual monitoring only, and by the time it is detected, it has developed into an uncontrollable situation. The high-sensitivity infrared imager can analyze the monitoring target in real time by setting the upper limit of the target temperature. If the target temperature reaches the set upper limit, an alarm message will be sent, so that the location and scale of the fire can be quickly determined and forest fires can be eliminated in the nascent stage, thus eliminating fire hazards.
▲Figure 3: Application of infrared thermal imaging technology in forest fire prevention
The human body itself is also a source of infrared radiation, and its tissue cells generate heat during the metabolic process and transfer it to the body surface. When the physiological condition of a part of the body changes or becomes diseased, the surface temperature of that part deviates from the normal value. As shown in Figure 4, medical infrared thermal imager can map this change into a temperature profile. As a non-invasive, non-contact, radiation-free and green diagnostic technology, medical infrared thermography is highly sensitive, comprehensive and fast, and can play the role of early screening, early diagnosis and dynamic monitoring throughout the process, thus achieving the purpose of "treating the disease before it happens".
It is known as one of the five major medical imaging technologies along with MRI, CT, X-ray, and ultrasound. The main applications of medical infrared thermography include physical identification, chronic disease prevention/control (geriatric care), major disease prevention, diagnosis of common diseases, comprehensive assessment of subhealth, rehabilitation services, mental health examination, Chinese medicine identification and efficacy assessment, etc. The application of this technology in the medical field is just beginning, and our society will gradually enter the elderly society, so infrared thermal imager has a huge application market in the medical field.
▲Figure 4: Application of infrared thermal imaging technology in the medical field
Infrared thermal imaging technology in security applications include anti-theft monitoring, camouflage and concealed target identification, night and bad weather conditions of the security patrol, key departments, buildings, warehouses security work, fire monitoring, land and port pass security, airport monitoring and other areas, as shown in Figure 5. High-end infrared imaging equipment has the advantages of high concealment, low false alarm rate and no need for any auxiliary light source at night, which can discover the target and record the scene in time, so as to accurately locate the location of people crossing the border.
Ports, airports, nuclear power plants, etc. belong to important areas and are vulnerable to theft and even terrorist attacks. The use of thermal imagers can play an important role in protection. Airports, hydroelectric power plants, refineries, oil and gas pipelines and any other large infrastructure can have perimeter boundaries of several kilometers. This is where thermal imagers can provide a secure perimeter alarm solution. Infrared thermal imaging technology has been used in security screening with good results during SARS in 2003.
In addition, thermal imagers can also be used for monitoring and warning of "low, slow and small" targets such as drones, aerial models, and airborne balloons. Because these targets have small radar scattering area, slow movement and other characteristics, radar technology means difficult to monitor them. The infrared thermal imaging technology is not limited by the above characteristics, and can monitor and warn the "low, slow and small" targets in the airspace in real time, so as to achieve effective detection and repulsion of "low, slow and small" targets.
▲Figure 5: Application of infrared thermal imaging technology in the field of security monitoring
Infrared thermal imaging technology is highly effective inthe maritime environment, meeting the needs of customers in port, waterway andcoastal security, maritime security, maritime illegal entry detection, maritimelaw enforcement, anti-piracy and threat detection, fishing fleet protection,ship tracking and observation, search and rescue operations, and environmentalprotection. Even objects that cannot be detected by radar systems (e.g. sailboats,wooden boats and floating objects) can be detected using infrared thermalimaging technology.
Thermal imaging imager can provide an "early warningsystem" for common hazards by showing the invisible heat emitted bypotential hazards (Figure 7), including floating objects, route traffic,anchored ships and small boats; man-made structures such as floating, bridgepiers and piers; and the identification of icebergs and shallow swimmingwhales.
The infrared thermal imager can help tankers pass safely throughice-covered waters, see everything at night, and see any detailed informationon other vessels, including the cockpit, bridge building, anchor gear, and allother details. It can also be used for search and rescue missions at sea.Search and rescue personnel can use the infrared thermal imager to accuratelyfind and locate victims, and then successfully launch the search and rescuework in the water.
Infrared thermal imaging technology can also help maritimepersonnel understand what is going on land, set up a perimeter around a crimescene or search area, and provide observed information to law enforcementofficers on land, facilitating efficient and safe cooperation between maritimeand waterfront law enforcement officers.
▲Figure 6: Application of infrared thermal imaging technology in the maritime field
Infrared thermal imaging technology also has a wide range of applications in industrial manufacturing (Figure 7). As electronic components become smaller and smaller, it has become extremely difficult to accurately understand their thermal information. However, engineers can easily visualize and quantify the thermal image of manufacturing equipment with the help of infrared thermal imaging technology.
At the same time, thermal imaging can be used to pre-optimize designs in the early stages of circuit design. The microscope combined with infrared thermal imaging technology becomes a thermal imaging microscope, capable of accurately measuring the temperature of targets as small as 3um. Researchers can use thermal imaging microscopy to characterize the thermal properties of components and semiconductor substrates in a non-contact manner.
Infrared thermal imaging technology can help automotive engineers improve the design of airbag systems, verify the efficiency of heating and cooling systems, quantify the effects of thermal shock on tire wear, check the performance quality of joints and welds, and more. New drug development with infrared technology. Scientists study the changes that occur in titration trays by observing temperature changes in chemical reactions. With the help of infrared thermography, manufacturing industries can shorten their R&D cycles and improve product quality, thereby increasing company profitability.
Infrared non-destructive testing is a widely used method for evaluating the properties of materials, components, and systems without causing damage to the object being inspected. Infrared thermal imaging technology is capable of performing advanced inspections such as nondestructive testing, stress mapping and surface cracking, but it can also be used to detect small temperature differences down to 1mK.
Infrared NDT is able to detect internal defects based on target excitation by observing thermal differences on the target surface. This technique is valuable for detecting holes, layer separation and water hiding in composite materials.
Stress testing and fatigue testing are common testing methods in mechanical engineering and materials science but provide only limited information for complex structures. Even with geometrically complex components, infrared thermography for thermal stress mapping can provide thousands of stress measurements simultaneously. This technique provides researchers with faster and more complete information than strain gauges.
▲Figure 7: Application of infrared thermal imaging technology in industrial field
With the continuous development of modern aviation science and technology, the safety of civil aircraft is getting higher and higher. After equipped with the Integrated Surveillance System (ISS), aircraft can provide the crew with comprehensive information on ground and air traffic, flight meteorology, complex terrain, etc., so that the air environment perception capability is continuously enhanced.
However, the ISS system only solves the safety problem when the aircraft is in the air, but does not provide an effective solution to the safety problem of landing and being located on the runway in low visibility and bad weather conditions such as fog or thunderstorms.
The existing ISS system has two shortcomings.
First, the pilot does not have full knowledge of the runway conditions when the aircraft is landing.
Second, aircraft cannot detect and identify their surroundings while moving on the runway, resulting in frequent collisions with other aircraft and injuries to ground crew. This defect can be compensated by adding infrared assist system under the front of the aircraft.
Since infrared thermal imaging technology can detect and identify the runway and the surrounding environment, navigation by means of infrared visual images can improve the takeoff and landing level of the aircraft, thus enhancing the safety of aircraft takeoff and landing, as shown in Figure 8.
▲Figure 8: Infrared detection in the field of civil aviation