Optical power meters measure the optical power or light intensity of a beam of light, including laser beams. Other general purpose light power measuring devices are usually called radiometers, photometers, laser power. An optical power meter measures the photon energy in the form of current or voltage from an optical detector such as a semiconductor, a thermopile, or a pyroelectric detector. It details the main components, including sensor heads and display units, and explains the two primary sensor technologies: robust thermal sensors for high powers and. Semiconductor photodiodes are ideal for making measurements of low-level light due to their high sensitivity and low noise characteristics. For light power measurements outside the field of.