Image Processing Reference
In-Depth Information
Figure2.4 Plastic plant pot on wood chips in sunlight: left—VIS; right—MWIR (3-5 mm).
Figure2.5 Thermal scar left by plant pot: left—VIS; right—MWIR (3-5 mm). (Courtesyof
objects that are at slightly different temperatures. Figure 2.6 illustrates this contrast
effect beautifully: a person walks barefoot into a kitchen and leaves behind heat
footprints which are only a few hundredths of a degree centigrade above ambient
Another interesting effect one can see with MWIR imaging is the variations of
skin temperature in a person's face. Figure 2.7 shows the author imaged in the
MWIR waveband. I have particularly cold cheeks and a cold nose due to a case of
Antarctic frostbite that permanently damaged the capillaries in my skin; therefore,
those areas appear dark. Note the patchy hot spots on the neck and jaw. These hot
spots change with time, and are caused by natural variations in blood flow. The
eyes are the warmest spot on the face, warmed by the copious blood flow near the
surface. The eye's surface is fairly isothermal (all at the same temperature), and
only the surface layer emits MWIR light; all of the detail (iris, pupil) we see with
visible light is hidden, as shown in Fig. 2.8, two images of my eye in visible and
MWIR light. MWIR light is also absorbed by the surface layers of the eye, and thus
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