Photonics Dictionary

An arrangement of optical fibers in a bundle whereby the geometric configuration of the input end differs from that of the output end without changing the total area; for example, a circular bundle...

An instrument for determining the sensitivity of a photographic film to light. The film is given either a stepped exposure or a continuously varied exposure; after processing, the density is measured...

An avalanche photodiode in which the light-absorbing area is a low-bandgap material and the PN junction is placed in an area of high-bandgap material, reducing dark current and increasing gain.

Three filters used in making a color print of a color negative, red, green and blue-violet, respectively. Each filter transmits about one-third of the visible spectrum onto the print.

A device used in measuring attenuation in optical fiber. The loss caused by the bends in a short reference length of fiber approximates that of a much longer fiber under test.

An interferometer in which interference is produced between wavefronts that are sheared in the sample object by a small lateral distance.

A filter that is transparent to shorter wavelengths, but opaque to longer wavelengths.

A mechanical or electronic device used to control the amount of time that a light-sensitive material is exposed to radiation.

A device used to measure the opening time of a shutter. The most common devices depend on the charging or discharging of an electrical condenser, or on the production of a curve of open area against...

An instrument that uses a blackened silver-disc reflector with a shutter to create temperature fluctuations that are proportional to the intensity of the solar radiation incident upon it. Using the...

A test chart whose luminance changes uniformly in one direction according to a sinusoidal rule. These charts carry groups of black lines on a white ground, the intensity profile across the lines...

A medical imaging method in which gamma camera heads rotate about the patient to detect radionuclides, enabling physicians to monitor functions within the body such as metabolism or blood flow.

A filter designed to decrease the luminosity of the sky without decreasing that of the landscape in the foreground. A filter that has a depth of tint that decreases from top to bottom is used in...

The method for measuring the index profile of an optical fiber by preparing a thin sample that has its faces perpendicular to the axis of the fiber, and measuring its index profile by interferometry.

A television system that uses a slow rate of horizontal scanning to increase its reproduction and transmittance accuracy of printed matter, photographs and illustrations.

The investigation of microstructures by an instrument that generates a narrow, highly collimated beam of x-rays.

The letter form used on visual performance test charts. The overall letter height is equal to five times the thickness of individual strokes. Normal 20/20 vision is represented by the ability to...

A filter that creates spherical aberration resulting in an image with a soft outline.

A series of solar cells arranged to collect solar radiation and to generate a given amount of electrical energy.

A type of birefringent filter, similar in principle to the Lyot filter, consisting of many identical birefringent elements, often arranged in a "fan" or "folded" configuration, positioned between two...

A solid-state drive (SSD) is a storage device that stores data electronically using solid-state memory chips. Unlike traditional hard disk drives (HDDs) that use spinning disks and mechanical...

An imaging system that uses a mosaic of tiny light-sensitive semiconductors (phototransistors) to produce individual outputs that are then converted into a coherent video signal.

An electroluminescent semiconductor that emits low intensity radiation in the green or red regions. Used as an indicator lamp.

A solid-state laser is a type of laser that uses a solid gain medium (as opposed to a liquid or gas) to produce coherent light. The term "solid-state" refers to the fact that the active medium, where...

A light valve that uses a crystal as the control layer medium and that operates on the principle of the electro-optic effect.

Device that uses a coherent reference wave to record the interference patterns produced by incident ultrasonic waves on an object.

On a test chart, the pattern designed to direct and measure geometric distortion.

1. Generally, an emulsion mask having a clean annular region in an otherwise opaque region. It is designed to eliminate undesired information. 2. A pinhole in a metal plate, placed at a focal plane...

In image processing, the enhancement of an image by increasing or decreasing its spatial frequencies.

A beam instability, induced by index of refraction inhomogeneities and component damage of dirt and dust particles, that exhibits exponential growth and causes both system degradation and energy loss...

Spatial light interference microscopy (SLIM) is an optical microscopy technique that belongs to the category of quantitative phase imaging methods. It is designed to provide high-resolution,...

Of evaporative coatings, a condition resulting when small chunks of material fly from the hot crucible onto the substrate surface and adhere there.

A power intensity pattern produced by the mutual interference of partially coherent beams that are subject to minute temporal and spatial fluctuations.

With respect to color photography, the measurement, at a given wavelength, of the way the color film modulates the radiant flux in the optical system containing the film.

Any pyrheliometer that has a filter placed over its sensor to limit the range of solar radiation it will detect; used to determine the distribution of solar radiation over its visible and into its...

A combination spectrometer and bolometer that is designed to measure a narrow band of radiation from a star.

An automatic scanning instrument that is used to study a substance's fluorescence over a wide range of wavelengths. It consists of a radiation source, a grating that functions as the monochromator in...

A high-contrast transparency of the gas sought, or an array of exit slits that correlates with some features of the spectrum. No standardized formula for positioning, number or thickness has been...

A kind of spectrograph in which some form of detector, other than a photographic film, is used to measure the distribution of radiation in a particular wavelength region.

Gas detection measurement technique that uses a built-in capacitative microphone to calculate the amount of absorbed laser power in a gas cell according to variations of gas pressure.

A spectrophotometer is a scientific instrument used to measure the intensity of light at various wavelengths in the electromagnetic spectrum, typically in the visible and ultraviolet regions. It is...

An instrument for plotting the rotatory dispersion of a substance at different wavelengths.

A spectroradiometer is a device used to measure the intensity of light at different wavelengths across the electromagnetic spectrum. It provides a detailed spectral distribution of light, breaking...

A spectrophotometer specially designed to measure spectral reflectance.