ABSTRACT

This chapter reviews radiometry, photometry, and light sources in terms of the basic notions and principles of measurement of electromagnetic radiation that are most relevant for optical metrology. It explains the difference between radiometry and photometry, and their quantities and units. The chapter describes a brief survey of conventional light sources and discusses modern light sources such as lasers, light emitting diodes, and super luminescent diodes, which are widely used in the contemporary techniques of optical metrology. For an ideal light source with a perfect electrical-to-optical power conversion, the luminous efficiency is equal to the luminous efficacy. Three-dimensional photometric measurements use spherical photometers to measure the directional luminous flux produced by light sources. They consist of a large-diameter globe with the light source mounted at its center. Colorimetry is a basic method for describing light sources in lighting industry.