Photonics Dictionary

Concerned with the transmission and reception of both sight and sound. An audiovisual system communicates pictorial images and audio signals.

The radiation-free transition that takes place within an ion, in which inner-shell vacancies in neutral atoms are filled by outer-shell electrons, thereby transferring energy to other electrons,...

The energy analysis of electrons released in a secondary step following initial excitation or ionization.

Augmented reality (AR) is a technology that integrates digital information, typically in the form of computer-generated graphics, images, or data, with the real-world environment in real-time. AR...

The indistinct, less luminous portion lying immediately outside an electric arc whose spectrum often differs from that of the core.

The strongest light emitted by the Earth's upper atmosphere. It most often can be viewed in the Arctic as the aurora borealis, and in the Antarctic as the aurora australis.

The green line, in the spectrum of the aurora borealis, that has a wavelength of 5577 Å; it is caused by a forbidden transition in oxygen.

A device for automatic exposure control in which a motor-driven diaphragm adjusts the aperture in response to a signal from a photocell detecting ambient light.

A spectrograph in which the refracted beam returns almost along the path traveled by the incident beam, and is brought to a focus by the lens that collimates the incident beam.

Technique of projecting an illuminated target at infinity and receiving the target image after reflection from a flat mirror surface.

An autocollimator is an optical instrument used for measuring small angular deviations with high precision. It operates on the principle of autocollimation, where a light source is directed onto a...

A signal-averaging device that improves signal-to-noise ratio by comparing a sampled signal with a time-delayed form of itself.

Autofluorescence refers to the natural emission of fluorescence exhibited by certain biological structures or molecules when exposed to light. Unlike fluorescence that results from the application of...

A means of adjusting the sharpness of an image automatically, with a sensor for estimating distance or contrast and a drive mechanism to adjust the lens. Active systems generate a light source to...

A CCD sensor that provides feedback to the motion control system for a telescope, allowing the telescope to follow a particular object or section of sky automatically.

The luminescence of a substance that is produced by energy within it (e.g., radioactive material).

Automated optical inspection (AOI) is a technology used in manufacturing processes, particularly in electronics, to automatically inspect and detect defects or anomalies in products. AOI systems use...

A method of producing an essentially constant output signal from an electronic circuit despite variations in the strength of the input signal.

A system for automatic industrial process control or measurement, consisting of an optical module for image acquisition, a segmentation processor to isolate the image from its background, and an...

In fiber optics, the use of a detector to study the range of refractive indices achieved at various wavelengths. This information is calculated electronically to establish the divergence between...

A direct reading spectrograph having a photomultiplier assembly in place of a photographic plate. The output from the photomultiplier assembly is received by a microammeter or a pen recorder.

Any photographic medium that, when chemically developed, produces an exact photographic reproduction of the original.

The photographic recording of the distribution and location of radioactive substances found in a specimen. The record formed is the autoradiograph.

A microscope to which a beamsplitter and illuminated reticle have been added to measure the radius of curvature of a spherical surface by locating both surface and center and calculating the distance...

A low-power telescope placed at the eyepiece of an optical system to increase overall magnification. Most often used to evaluate image quality.

A glass or metal measurement tool having a precisely calibrated angle between two of its faces.

A unit of speed of transmission or receipt of a signal, roughly equal to bits per second; common baud rates are 300, 1200, 2400, 4800 and 9600.

The scale for floating hydrometers used to measure the specific gravity of a polishing suspension. The depth of immersion is a linear function of the inverse of the density. The Baume scale is linear...

A defect on or in an optical element that does not appreciably impair the function of the surface.

A sheet of thin brass, one edge of which has been accurately cut to a known and marked circular radius. It is used to check the radius of curvature of a rough-ground lens by contact.

A caustic formed by reflection.

A surface that envelops a bundle of rays or bundle of normals to the wave surface. It may be observed as a hollow, luminous cusp in a turbid medium.

A system that determines whether an image is in or out of focus by means of a source of illumination at the conjugate focal point, which reflects off the target; the return beam is mediated by masks...

Observed electroluminescence of zinc sulfide phosphors when excited by an electric field. This effect is the basis for the alternating-current phosphor panel technology.

A caustic formed by refraction.

The principle stating that the displacement of spectrum lines is determined by the distance between, and relative velocity of, the observer and the light source. When distance decreases, the lines of...

A fast, wide-angle lens used in television and photographic cameras, with excellent overall correction, but subject to residual oblique spherical aberration.

An interferometer spectrometer designed to measure thicknesses of thin films or layers by recording the interferogram and by having a computer within the instrument to establish the distance between...

Fizeau fringes are interference fringes observed in an interferometer, specifically in a Fizeau interferometer. The Fizeau interferometer is named after the French physicist Armand Fizeau, who...

A type of interferometer noted for producing narrow multiple-beam interference fringes. As a result, when compared with the Twyman-Green, the Fizeau interferometer has fewer optical components, does...

A device used to measure the speed of light by adjusting the rotation of a toothed wheel so that light passing through one tooth opening is reflected through the next. This device has since been...

The Foucault test is performed by moving a knife edge laterally into the image of a small point source. The eye, or a camera, is placed immediately behind the knife edge, and the exit pupil of the...

A polarizing prism formed from calcite that is like the Nicol prism but has the two parts divided by a thin air-film and cut to such angles that the extraordinary beam will be transmitted and the...

A rotating mirror coupled with a distant mirror and used in a system by Foucault to compute the velocity of light. Light moving from the rotating mirror to the distant mirror and back was following...