CHAPTER 6INFRAREDThe term infrared is a Latin word meaningbeyond the red. Infrared is commonly shortened toIR. The process of detecting or sensing infraredradiation from a target without being in physicalcontact with that target is known as remote sensing.Active and passive systems are used for remotesensing.Active systems send a signal to the target andreceive a return signal. Radar sets are examples ofactive systems. Passive systems detect a signal ordisturbance originating at the target. The signal maybe emitted either by the target or another source.Photography using natural light is an example of apassive system.Humans can see only a small part of the entireelectromagnetic spectrum. However, even though wecannot see them, other parts of the spectrum containuseful information. The infrared spectrum is a smallportion of the entire electromagnetic spectrum. IRradiation is a form of electromagnetic energy. IRwaves have certain characteristics similar to those oflight and RF waves.These characteristics includereflection, refraction, absorption, and speed oftransmission.IR waves differ from light, RF, andother electromagnetic waves only in wavelengths andfrequency of oscillation.The IR frequency range is from about 300gigahertz to 400 terahertz. Its place in theelectromagnetic spectrum (fig. 6-1 ) is between visible6-1Figure 6-1.-Electromagnetic spectrum.
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business
