Image Processing Reference
In-Depth Information
Figure2.1 The infrared spectrum in relation to visible light.
Figure2.2 A child watching television: left-VIS; right-3-5 micrometers. (Courtesyof
more thermal IR, but the sun itself is only noticeable when it reflects off shiny
objects, and then only in the MWIR band. For this reason, thermal imaging
technology facilitates the detection of many objects in total darkness and, in
many cases, makes it possible to measure their surface temperatures. Midwave
and longwave infrared light can also penetrate smoke, haze and mist, facilitating
observation in conditions that make visible-light imaging impossible. For instance,
a person lost on a moonless night in the woods without a flashlight or signal flare
would be very difficult to find from the air with visible-light imaging. However, this
person (or any warm-blooded animal) displays a natural infrared flare in the form of
his or her body, a flare of thermal energy against a dark (cold) background. Outdoor
backgrounds appear darker than any warm objects in the thermal wavebands, since
trees and grass are much cooler than warm-blooded animals.
When we use technology to image the world in the thermal infrared waveband
of the electromagnetic spectrum, we are exploring unknown territory, seeing things
that no animal has ever seen. This is truly alien vision! Thermal images can look
very different from visible-light images of the same scene. This is especially true
in darkness, or what we call darkness because there is little or no visible light. The
thermal infrared world is never really dark, and objects that are just slightly warmer
Search WWH ::

Custom Search