How Do Infrared Cameras Work - FLIR mariner Operator's Manual

8 – Infrared Technology

8.2 How do Infrared Cameras Work?

Infrared energy is part of a complete range of radiation called the
electromagnetic spectrum. The electromagnetic spectrum includes gamma
rays, X-rays, ultraviolet, visible, infrared, microwaves (RADAR), and radio
waves. The only difference between these different types of radiation is
their wavelength or frequency. All of these forms of radiation travel at the
speed of light (186,000 miles or 300,000,000 meters per second in a
vacuum). Infrared radiation lies between the visible and RADAR portions
of the electromagnetic spectrum. Thus infrared waves have wavelengths
longer than visible and shorter than RADAR.
Figure 8-5: Electromagnetic Spectrum
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
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