Most infrared (IR) systems consist of three major components:
Each of these components is, among other things, a function of wavelength (l), and the overall conversion of useful energy (E) through the system can thus be expressed as: E=Kf∆λSλ●Tλ●Dλ●dλ where K is a constant.
- a source of energy (S),
- a detector (D) and
- an optical system (T) which controls the energy transfer from source to detector.
The ultimate purpose of most IR systems is to detect source emission in the presence of background or unwanted radiation. This can usually be achieved through:
To an IR system designer, it is, therefore, of paramount importance to fully understand, characterize and specify each major component of the system (including the background) by their wavelength and temperature characteristics, size and performance variation with time and/or frequency.
- spectral discrimination,
- spatial discrimination,
- temporal discrimination, or
- any combination of these.