8 – Infrared Technology
28
May ’08
334-0001-00-10-LE, rev. 100
8 – Infrared Technology
The primary source of infrared radiation is heat or thermal radiation. Any
object which has a temperature radiates in the infrared portion of the
electromagnetic spectrum. Even objects that are very cold, such as an ice
cube, emit infrared. When an object is not quite hot enough to radiate
visible light, it will emit most of its energy in the infrared. For example, hot
charcoal may not give off light, but it does emit infrared radiation which
we feel as heat. The warmer the object, the more infrared radiation it
emits.
Infrared cameras produce an image of invisible infrared or “heat” radiation
that is unseen by the human eye. There are no colors or “shades” of gray
in infrared, only varying intensities of radiated energy. The infrared imager
converts this energy into an image that we can interpret. Several detector
technologies exist; the sensor in the PathFindIR LE is of the latest solid
state design, offering long life and fully automatic image optimization
(contrast and gain). True thermal imagers should not be confused with
infrared illuminator cameras that are often presented as simply “infrared
cameras.” There are hundreds of low cost infrared illuminated cameras on
the market at prices below $100. These cameras do not produce the same
image because they do not detect heat. They operate in wavelengths near
visible, and require an IR illuminator to provide an image. IR illuminators
have very short range, and require a lot of power to see beyond 5 meters.
Figure 8-5: Electromagnetic Spectrum
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