Infrared Radiation In Thermal Imaging Cameras

This work was further developed at the Royal Signals and Radar Establishment in the UK when they discovered that mercury cadmium telluride was a photoconductor that required much less cooling. Honeywell in the United States also developed arrays of detectors that could cool at a lower temperature,[further explanation needed] but they scanned mechanically. This method had several disadvantages which could be overcome using an electronic scanning system. In 1969 Michael Francis Tompsett at English Electric Valve Company in the UK patented a camera that scanned pyro-electronically and which reached a high level of performance after several other breakthroughs during the 1970s.[15] Tompsett also proposed an idea for solid-state thermal-imaging arrays, which eventually led to modern hybridized single-crystal-slice imaging devices.[13]

infrared radiation in thermal imaging cameras

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Infrared energy is just one part of the electromagnetic spectrum, which encompasses radiation from gamma rays, x-rays, ultraviolet, a thin region of visible light, infrared, terahertz waves, microwaves, and radio waves. These are all related and differentiated in the length of their wave (wavelength). All objects emit a certain amount of black body radiation as a function of their temperature.

Generally speaking, the higher an object's temperature, the more infrared radiation is emitted as black-body radiation. A special camera can detect this radiation in a way similar to the way an ordinary camera detects visible light. It even works in total darkness because ambient light level does not matter. This makes it useful for rescue operations in smoke-filled buildings and underground.

A major difference with optical cameras is that the focusing lenses cannot be made of glass, as glass blocks long-wave infrared light. Typically the spectral range of thermal radiation is from 7 to 14 μm. Special materials such as Germanium, calcium fluoride, crystalline silicon or newly developed special type of chalcogenide glasses must be used. Except for calcium fluoride all these materials are quite hard and have high refractive index (for germanium n=4) which leads to very high Fresnel reflection from uncoated surfaces (up to more than 30%). For this reason most of the lenses for thermal cameras have antireflective coatings. The higher cost of these special lenses is one reason why thermographic cameras are more expensive.

Images from infrared cameras tend to be monochrome because the cameras generally use an image sensor that does not distinguish different wavelengths of infrared radiation. Color image sensors require a complex construction to differentiate wavelengths, and color has less meaning outside of the normal visible spectrum because the differing wavelengths do not map uniformly into the system of color vision used by humans.

For use in temperature measurement the brightest (warmest) parts of the image are customarily colored white, intermediate temperatures reds and yellows, and the dimmest (coolest) parts black. A scale should be shown next to a false color image to relate colors to temperatures. Their resolution is considerably lower than that of optical cameras, mostly only 160 x 120 or 320 x 240 pixels, although more expensive cameras can achieve a resolution of 1280 x 1024 pixels. Thermographic cameras are much more expensive than their visible-spectrum counterparts, though low-performance add-on thermal cameras for smartphones became available for hundreds of dollars in 2014.[26] Higher-end models are often deemed dual-use military grade equipment, and are export-restricted, particularly if the resolution is 640 x 480 or greater, unless the refresh rate is 9 Hz or less. The export of thermal cameras is regulated by International Traffic in Arms Regulations. A thermal camera was first built into a smartphone in 2016, into the Cat S60.

Thermography finds many other uses. For example, firefighters use it to see through smoke, find people, and localize hotspots of fires. With thermal imaging, power line maintenance technicians locate overheating joints and parts, a telltale sign of their failure, to eliminate potential hazards. Where thermal insulation becomes faulty, building construction technicians can see heat leaks to improve the efficiencies of cooling or heating air-conditioning.

Some physiological activities, particularly responses such as fever, in human beings and other warm-blooded animals can also be monitored with thermographic imaging. Cooled infrared cameras can be found at major astronomy research telescopes, even those that are not infrared telescopes.

Without cooling, these sensors (which detect and convert light in much the same way as common digital cameras, but are made of different materials) would be 'blinded' or flooded by their own radiation. The drawbacks of cooled infrared cameras are that they are expensive both to produce and to run. Cooling is both energy-intensive and time-consuming.

The camera may need several minutes to cool down before it can begin working. The most commonly used cooling systems are peltier coolers which, although inefficient and limited in cooling capacity, are relatively simple and compact. To obtain better image quality or for imaging low temperature objects Stirling engine cryocoolers are needed. Although the cooling apparatus may be comparatively bulky and expensive, cooled infrared cameras provide greatly superior image quality compared to uncooled ones, particularly of objects near or below room temperature. Additionally, the greater sensitivity of cooled cameras also allow the use of higher F-number lenses, making high performance long focal length lenses both smaller and cheaper for cooled detectors.

In principle, superconducting tunneling junction devices could be used as infrared sensors because of their very narrow gap. Small arrays have been demonstrated. They have not been broadly adopted for use because their high sensitivity requires careful shielding from the background radiation.

Uncooled thermal cameras use a sensor operating at ambient temperature, or a sensor stabilized at a temperature close to ambient using small temperature control elements. Modern uncooled detectors all use sensors that work by the change of resistance, voltage or current when heated by infrared radiation. These changes are then measured and compared to the values at the operating temperature of the sensor.

Uncooled infrared sensors can be stabilized to an operating temperature to reduce image noise, but they are not cooled to low temperatures and do not require bulky, expensive, energy consuming cryogenic coolers. This makes infrared cameras smaller and less costly. However, their resolution and image quality tend to be lower than cooled detectors. This is due to differences in their fabrication processes, limited by currently available technology. An uncooled thermal camera also needs to deal with its own heat signature.

Originally developed for military use during the Korean War,[citation needed][31] thermographic cameras have slowly migrated into other fields as varied as medicine and archeology. More recently, the lowering of prices has helped fuel the adoption of infrared viewing technology. Advanced optics and sophisticated software interfaces continue to enhance the versatility of IR cameras.

All objects emit infrared energy, known as a heat signature. An infrared camera (also known as a thermal imager) detects and measures the infrared energy of objects. The camera converts that infrared data into an electronic image that shows the apparent surface temperature of the object being measured.

Many infrared cameras also include a visible light camera that automatically captures a standard digital image with each pull of the trigger. By blending these images it is easier to correlate problem areas in your infrared image with the actual equipment or area you are inspecting.

IR-Fusion technology (exclusive to Fluke) combines a visible light image with an infrared thermal image with pixel-for-pixel alignment. You can vary the intensity of the visible light image and the infrared image to more clearly see the problem in the infrared image or locate it within the visible light image.

Beyond basic thermal imaging capabilities, you can find infrared cameras with a wide range of additional features that automate functions, allow voice annotations, enhance resolution, record and stream video of the images, and support analysis and reporting.

A thermal camera is made up of a lens, a thermal sensor, processing electronics, and a mechanical housing. The lens focuses infrared energy onto the sensor. The sensor can come in a variety of pixel configurations from 80 60 to 1280 1024 pixels or more. This is the resolution of the camera.

The potential uses for thermal cameras are nearly limitless. Originally developed for surveillance and military operations, thermal cameras are now widely used for building inspections (moisture, insulation, roofing, etc.), firefighting, autonomous vehicles and automatic braking, skin temperature screening, industrial inspections, scientific research, and much more.

Thermal, or infrared, detection systems utilize sensors to pick up radiation in the infrared part of the electromagnetic spectrum. An infrared camera detects the thermal energy or heat emitted by the scene being observed and converts it into an electronic signal. This signal is then processed to produce an image. The heat captured by an infrared camera can be measured with a high degree of precision. This means that infrared cameras can be used for things like checking thermal performance and determining the relative seriousness of problems associated with heat. The higher the temperature of a body or object, the more radiation it emits.

However, in the part of the electromagnetic spectrum from 0.7 µm to 4 µm, infrared radiation is measured according to the light reflected off of the material or scene being observed. This capability is very useful in the semiconductor, glass, and steel industries. 2ff7e9595c