Thermal Imaging

Thermal Imaging - Electronics - February 2002
Electronics February 2002
By Ben Ellison

Some Like It Hot
Adventures in thermal imaging.

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There I was in a Fort Lauderdale hotel lobby, learning about thermal imaging by watching women and seeing a lot. "X-ray glasses, an adolescent boy's dream!" I thought, and wondered if the lads at D&B Technology intended a double meaning when they branded their new line of infrared viewing devices HotEye.

But after further testing at the end of a dark dock, and a long conversation with D&B president Bob Gravely, I'm convinced that HotEye is an innocent product and, though expensive, possibly a real lifesaver. To appreciate the potential of thermal imaging, and particularly to differentiate it from more common night vision tools, you need some background on the technologies.

Visible light is electromagnetic radiation within a certain frequency band, and most everything we see--fires and the like excepted--is reflecting light from another source. That's because a thing has to be darn hot to radiate visible energy. However, every object, even an ice cube, radiates infrared energy--that is, energy below ("infra") the lowest visible frequency (red)--in proportion to its temperature. Back in the 1960s some serious defense industry R&D went into developing an electronic way to distinguish small differences in infrared (IR) radiation and convert them into a visible video signal, ultimately a target.

Meanwhile, other engineers with similar goals developed "light amplifying" electronics that can multiply glimmers of reflected star- or moonlight thousands of times. A high-end modern unit, like ITT's Night Mariner 160, claims a 50,000 amplification factor, able to detect a man at a distance of 1,800 feet in starlight, farther with optional magnification. It has the form of a monocular and retails at around $1,800. (Some night-vision units come with "infrared illuminators" for short-range work in pitch black; they are using "near" IR, which is reflective and of slightly different frequency than thermal IR.)

At any rate, the big plus for mariners with either type of night-vision instrument is the ability to see dangers like floating logs and nonmetallic vessels that radar might easily miss. Both light-amplifying and thermal viewers produce monochromatic, slightly fuzzy images, but the similarity is superficial. For instance, with either tool you can make out a person walking down a pier in near total darkness; but with the thermal imager you might also see his slightly warm footprints trailing behind him. Similarly, harking back to my demo in the hotel lobby, a thermal detector can magically map the way a person's body heat transmits through his or her clothing (note to privacy lawyers: You're not really peering through the clothing, it just looks that way).

So seeing heat is truly different and presents some interesting, even practical, possibilities. If you look around your engine room with something like the HotEye 3x, you might very well see tiny oil or exhaust leaks. If you inspect your hull when the engines are warmed up, you should be able to make out structural elements, perhaps even a bad weld or a cracked frame. This sort of special sight works particularly well on the thermally flat plane of the ocean. The relatively hot head of a man overboard will show up like bright light.

Next page > Some Like It Hot continued > Page 1, 2, 3

This article originally appeared in the January 2003 issue of Power & Motoryacht magazine.

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