Image Processing Reference
In-Depth Information
Figure1.5 Robert Wood in the UV band.
The near-infrared band is usually defined as 750 nm to 1100 nm, 750 nm being the
edge of normal human vision and 1100 nm being the cutoff wavelength for silicon
detectors. This is the first infrared band where photographs were taken, and the
first band of invisible light to be used in electronic imaging.
The ability to see in the dark without being detected must be one of mankind's
oldest wishes. Early human beings equipped with modern night-vision devices
would have been able to see if a predator was lurking outside in the darkness
without the predator knowing it was being watched. Night vision is crucial to
modern warfare, and military forces of the world have committed extensive
resources to the problem of target identification in various lighting and weather
conditions. The need for covert night vision led to the development of infrared
viewing systems such as the sniperscope, which enabled Allied soldiers in WWII
to see in the darkness with covert light sources invisible to unaided eyes. The
imaging system was mounted on the M1 carbine rifle, and gave the shooter about
a 70-yard range to accurately hit enemy soldiers in total darkness.
Figure 1.6 illustrates a typical sniperscope design used during the Korean War.
These devices employed an imaging tube similar to a television-camera tube but
sensitive to near-IR light. The soldiers would illuminate the target with searchlights
equipped with special filters that blocked all visible light but passed near-IR light.
This system has the distinct disadvantage that an enemy equipped with a similar
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