Civilian Thermal-Imaging Just Got a Whole Lot Cooler
Getting Cooler All the Time
While thermal-imaging cameras are not just for megayachts, the top of the line continues to climb.
When suspected Boston Marathon bomber Dzhokhar Tsarnaev happened upon a shrink-wrapped boat on a trailer parked in Watertown, Massachusetts, he must have imagined that it would be the start of an escape route from the police manhunt. He was wrong. Tipped off by the suspicious boat owner, police used a thermal-imaging camera to examine the boat, and saw the distinctive shape of a human being, lying in the cockpit.
Thermal-imaging technology is being used by fire and ambulance crews to locate casualties and by doctors to detect disease. Even better, the technology has become more accessible as the price point has fallen, so increasing numbers of technicians are beginning to use such systems to locate all manner of hard-to-find problems, ranging from leaking pipes to defective electrical connections.
And for the same reason, more and more boaters are discovering thermal imaging as the first-choice night-vision system. FLIR, which stands for “Forward-Looking InfraRed,” has long been the market leader, and the company’s stated strategy for capturing both ends of the price spectrum is paying off as boaters and other cost-conscious consumers (such as those in the luxury automotive segment) get familiar with the brand’s lower-priced offerings. Meanwhile, the military-spec units sold to the defense industry have not been accessible to consumer markets. FLIR’s success has paid dividends, as it diversified its product line with the acquisition of Raymarine in 2010. FLIR’s thermal imagers are also compatible with systems from other manufacturers, such as Furuno and Simrad.
Until this year, all thermal imagers sold for recreational vessels have been “uncooled.” They work by using a system of lenses—made from crystals of pure germanium—to focus infrared energy onto a grid of tiny heat sensors called a microbolometer, which converts the infrared picture into a digital image. The basic structure is similar to that of an ordinary visible-light digital camera, in which glass lenses focus light onto a screen that converts light into electricity to create a digital image.
But FLIR’s new MU series gives us another kind of thermal-imaging technology to consider. Lou Rota, FLIR’s vice president of maritime sales, told Power & Motoryacht that FLIR has been making cooled thermal-imaging cameras for military, law-enforcement, and search-and-rescue customers for more than 40 years.
“But until now, cooled technology was only available to these government and military customers,” he added. “The MU-Series is the first cooled thermal-imaging camera available to private yacht owners.” Cooling is significant because thermal imagers rely on the fact that everything in the everyday world radiates infrared energy—even things that are at or below the freezing point. Of course that includes the camera itself, and even the microbolometer that creates the thermal image. The “thermal noise” created within an uncooled thermal-imaging camera reduces the camera’s ability to detect cool objects, and makes it less able to distinguish the subtle variations in temperature that create a clear, contrasty picture.
It’s like when you are using a projector to give a PowerPoint presentation: In a brightly lit room, your slides are difficult to see and their colors look washed out. Reducing the heat within an IR camera turns the lights off in the room, so to speak, and allows the use of much more sensitive detectors, increasing the system’s ability to detect cool objects, and enhancing the contrast in its picture. It lets the fine details of the presentation stand out.
But “cooling,” in this context, seems a bit of an understatement. When I think of “cool,” I think of a beer, at 40 degrees or so. But when Rota says “cooled,” he means “cryogenically cooled,” down towards the temperature of liquid nitrogen, about 300 degrees below freezing.
Neither the precision-engineered cryocooler required to achieve such low temperatures nor the super-sensitive, high-definition sensor required to reap the benefits are low-cost items, but their prices are repaid by the fact that a cooled IR camera can incorporate a long-focal-length lens—the equivalent of fitting a telephoto lens to a visible-light camera—for impressive long-range performance.
The cooled camera in the MU 602, for instance, can detect a human-sized target at a range of 5 miles. That kind of performance is impossible for an uncooled IR camera, because gathering enough IR energy to create a long-range picture would need a bigger objective lens than can be carved from a single germanium crystal.
So if cooled IR cameras are so much better than uncooled cameras, why does the flagship model of FLIR’s MU range—the $230,000 MU602 CLW—pack four different cameras into its goggle-eyed pan-and-tilt mounting? “No one payload is perfect for all applications,” Rota explains. “The cooled thermal-imaging payload is a very narrow field-of-view imager for long-range performance, extremely valuable for navigation as well as for detecting threats at long range.”
“The uncooled payload with its wide field of view provides enhanced short-range situational awareness,” Rota continues. “It gives the captain a wide view of everything in front of the boat, including hazards that radar may not detect ... And in a man-overboard emergency, thermal imaging becomes a valuable safety tool, enabling quick detection of a person in the water.” The two thermal imagers work in tandem to provide critical safety information. What else is in that MU-Series unit?
“The other two cameras are color visible-light and ultra-low-lux payloads for daytime and low-light (dawn and dusk) navigation,” Rota says. Even the low-light camera depends to some extent on infrared. An ordinary digital camera—be it a typical webcam or a pro-quality SLR—can detect infrared. Try it yourself, by using the camera function on your cellphone to look at the business end of a TV remote while someone is changing channels: You’ll see the IR transmitter flashing in your camera screen even though it is invisible to the naked eye!
In normal photography, that’s an unwanted side effect because it tends to defocus the image. Camera manufacturers minimize it by fitting filters that remove most of the infrared. But in a low-light camera it’s a bonus: The “near infrared” energy gives a useful boost to the visible-light image, and behaves enough like visible light to create a reasonably sharp and immediately recognizable picture.
So the four payloads in one device let the captain switch to whichever is best for the job at hand, whether he’s watching for pirates in open water, groping into an inlet in fog, or nudging up to a dock in the dark.
This article originally appeared in the August 2013 issue of Power & Motoryacht magazine.