ABSTRACT
In the broadest sense, radiometry is the body of science and technology concerned with the accurate measurement of radiant energy. The accuracy of both the measurement and its interpretation depends on understanding, through measurement, what happens to the radiant energy from the source. This understanding is also part of radiometry. How to measure the radiant energy depends on its form. When it is in the form of electromagnetic (EM) radiation, the details of the radiometric measurement system also depend on the spectral region of interest. The focus here will be on the optical region of the EM spectrum, which extends in wavelength from about 100 Å to about 1 mm and embraces what is generally referred to as the ultraviolet, visible, and infrared. However, many of the concepts, quantities, terms, and techniques that will be covered will also apply to some degree to other regions of the EM spectrum.
