Most cameras capture what we can see. The best-known exception to the rule is the infrared (IR) thermography camera, which detects infrared light—invisible radiant energy that we experience as heat but can’t see. At temperatures above absolute zero (–273.15°C), everything emits thermal radiation. The warmer an object, the more radiation it emits, which makes humans and other warm-blooded animals stand out against cooler backgrounds in an infrared camera image
Long Wavelength Infrared (LWIR) cameras are the most commonly used IR cameras. As their size, weight and costs decline and their performance improves, an ever-widening range of applications is opening up, from unmanned drones helping protect endangered wildlife to diagnostic systems that detect cancer and many other diseases. According to Global Market Insights, Inc., by 2023 the IR camera market will be worth $6.82 billion.
LWIR cameras—the IR sweet spot
Infrared thermography operates in three wavelength bands: Medium Wavelength Infrared (MWIR), Long Wavelength Infrared (LWIR) and Very Long Wavelength Infrared (VLIR).
The VLIR band has the most limited range of applications. It is used primarily for spectroscopy, a laboratory technique for identifying substances by the light they reflect, and high-powered telescopes for astronomy.
The MWIR band is best suited to inspecting high-temperature objects—which is why most MWIR cameras must be cooled to approximately -196 °C, making them relatively large and expensive. By contrast, LWIR cameras are ideal for working in near room temperature, don’t require cooling and are small and inexpensive. Most LWIR cameras are based on a microbolometer, a sensitive electrical detector that processes infrared radiation into temperature ranges to create grey scale or color images. And most are used to either enhance visual information or to precisely measure temperature.
A more complete picture
Because LWIR cameras measure heat rather than light, they are increasingly used in applications where traditional imaging (visible light) just doesn’t reveal enough information, like helping to guide self-driving cars at night or revealing faults in high-powered transformers and electrical panels before they fail.
Recent advances include an application to more efficiently install and monitor roof top solar panels, a clear indication of the versatility of the technology. Using an iOS or Android device, users control a small drone equipped with a LWIR camera. As it flies over the solar panel installation, the drone captures thermal images that generate highly accurate 3D structural models.
For installation, these models ensure optimum placement of panels. For maintenance, they accurately detect panel damage or failure. The system can reduce panel inspection time for commercial installations from days to minutes—and no one has to climb onto a potentially dangerous roof.
Protection from above
The stakes in wildlife conservation are high. Every year, poached wildlife is an $8 to $10 billion business—about the same as human trafficking, illicit drugs or the arms trade. And poaching of endangered wildlife is accelerating—the poaching of rhinos, for example, has increased fifty-fold since 2006, according to the World Wildlife Fund.
Drone-mounted LWIR cameras are helping to transform wildlife conservation. Governments and NGOs around the world are using drones armed with LWIR cameras to keep poachers away from endangered wildlife, including orangutans in Borneo, rhinos in South Africa and elephants in Kenya. By emitting high frequency sounds, the drones can herd wildlife away from areas where they’re likely to be shot. In a recent pilot project in a protected area of Kenya, patrolling with drones reduced elephant and rhino poaching by 96 percent. The Kenyan government now plans to deploy drones in all of its 52 national parks and reserves.
When precision is essential
For some applications, relative temperature information (how warm one object is compared to other objects) provided by LWIR thermography cameras isn’t enough—measures of absolute temperature are required, with a precise value assigned to every pixel in an image. LWIR radiometric cameras offer this precision for applications such as food processing and high-tech manufacturing.
To accurately convert an object’s infrared radiation (measured in in watts per square meter) to temperature, radiometric cameras must take several factors into account. How far away is the object, and what are its thermal properties? What is the temperature and relative humidity of the surrounding environment? These calculations require algorithms an order of magnitude more complex than for LWIR thermography cameras, and they generate large amounts of data that must be processed to produce images.
On the medical frontier
Radiometric LWIR cameras have proven especially useful in medical applications. The association between changes in human body temperature and disease is almost as old as medicine itself, and radiometric imaging is used to diagnose and study diseases in which higher skin temperature reﬂects abnormalities or inﬂammation in underlying tissues—diseases like cancer, inﬂammatory arthritis, osteoarthritis and fibromyalgia. As they become smaller and less expensive, radiometric LWIR cameras will likely become as ubiquitous as X-ray and ultrasound imaging in hospitals and medical clinics.
As the cost and size of LWIR cameras decreases, more kinds of applications become possible. Already there is an LWIR application for reviewing controversial decisions made by the on-field umpires in international cricket matches; if the ball has been in contact with a player’s bat, an LWIR camera shows the heat generated. At international airports, LWIR technology is helping prevent the spread of deadly diseases by identifying passengers with fever. And LWIR cameras mounted on satellites and aircraft are being used by archeologists to identify human-made features hidden beneath the soil surface.
Clearly, the future of LWIR cameras is as unlimited as human ingenuity.