Photonics Dictionary

The transformation of incident radiant energy into a photoelectric emission current.

A cathode principally designed to emit a photoelectric current.

A system having a photoelectric detector for the measurement of three quantities related by linear combination to tristimulus values of a sample.

The measurement and analysis of color using a photoelectric instrument having three filters with broad spectrum bands.

The constant that, multiplied by the frequency of the radiation-producing emission of photoelectrons, determines the amount of voltage each photoelectron absorbs.

The control of an instrument or electrical circuit by the current produced by varying radiation incident to a photoelectric cell.

A device used to count objects that pass a given point by allowing each object to obstruct a beam of light falling on a photocell. Slow counting rates can be recorded by a mechanical counter, but...

The electron stream emitted by a phototube when the cathode is exposed to light.

The emission of an electron from a surface that occurs when a photon impinges upon the surface and is absorbed. This effect is the means by which photons may be detected.

The electron emission from a substance or instrument whose surface has been bombarded by a suitable amount of radiation.

A device consisting of a microammeter, a photovoltaic cell and a battery. It is used for the measurement of scene brightness and the determination of correct exposure for photographic processes.

A filter fluorometer that uses a photomultiplier tube to detect the fluorescence of a sample.

Also known as light beating. The mixing of two narrowband optical components to produce an AC component in the photocurrent at the optical difference frequency.

A phototube in which the primary photoemission current, before being extracted at the anode, is multiplied many times.

Also known as electronic photometer. A photometer with a photocell, phototransistor or phototube for measuring the intensity of light.

The use of photoelectric sensors to detect and measure the intensity of a light source. This application, as compared to human observation, results in higher speeds of operation, a greater...

An instrument used to measure the temperature of a source through the use of photoelectric cells to detect and measure the intensity of the light emitted by the source.

An input device for a computer that detects and reads the data, in the form of punched holes in cards, by light that is transmitted through the holes.

An instrument that uses a photocell to detect and measure the intensity of incident light.

A photoelectric photometer used to measure the reflectance of a surface.

A relay that opens or closes an electrical circuit depending on the intensity of the light incident to a photoelectric device contained in the relay.

A system mounted a few inches above a moving plane that consists of a light source, lenses and one or more phototubes. In this position, the scanner actuates the control equipment when the quantity...

That property of a material that determines its ability to release electrons when absorbing photons.

A system that consists of a spectrophotometer with a photoelectric detector for measurement of radiant energy.

The ejection of electrons from the surface of a solid by the absorption of a sufficient amount of photons.

The creation of free electrons within a solid by the absorption of a sufficient amount of photons. The effect produces an increase in the conductivity of the solid.

The changing of the kinetic energy of a mobile electron into radiant energy, as in formation of x-rays.

Characteristic of the relationship between photoelectric activity and the wavelength of incident radiation.

An instrument for measuring the brightness (luminance) of a scene. It may be a spot meter, covering an area of a degree or less, or an averaging meter, covering a broad area of the scene. Brightness...

Cathode radiant sensitivity refers to the ability of a photocathode to convert incident radiant energy, typically in the form of light, into an electrical signal. Photocathodes are components used in...

An isotope of cesium that emits negative beta particles and has a half-life of 2.19 years; its applications include photoelectric cells and developmental ion propulsion systems.

Colorless crystals used in photoelectric cells and for photosensitive material in cathodes.

A photoelectric detector consisting of a glass tube internally coated with a low conductance material. Voltage applied along the tube causes photoemission from the photocathode at the end of the tube...

A photoelectrically controlled, alphanumeric reading device that converts characters to audible or sorting signals which can be fed to a computer, electric typewriter, tapepunch or other machine.

1. A device used in chemistry to compare the colors of solutions held in flat-bottomed tubes and viewed along the length of the tube. Often a solid glass plunger is moved along one of the tubes to...

A type of photoelectric proximity mode sensing incorporating a lens system to focus the light from the emitter in a small, concentrated spot at a specific point in front of the sensor. Also referred...

Use of a photoelectric receiver to sense an object's presence by detecting a small amount of the emitter's light that is diffusely reflected by the object.

An instrument that uses a photoelectric system to determine the size and volume of dust particles in a given unit of air.

In photoelectric sensing, the portion of the transmitted beam that actually functions in the system; the diameter of the beam that determines the presence or absence of an object by being blocked or...

A nonmagnetic instrument utilizing an electrofocus and deflection tube with a photocathode for imaging purposes. The optical image is converted into a photoelectric output at the photocathode and is...

A microscope that uses a flying spot scanner, directed through the eyepiece, as a light source to determine the features of a transparent specimen. The flying spot is modulated by the varying density...

A device used to scan, with a small, intensely bright spot, portions of a picture surface and to transform the original picture into a series of electrical signals. In optical character recognition,...