Photonics Dictionary

Enhanced picture archiving and communication system (PACS) display (ePAD) is a software tool used in medical imaging to view, manipulate, and analyze radiological images, such as x-rays, CT scans,...

Etaloning is an optical phenomenon that occurs in imaging systems, particularly in devices such as spectrometers, interferometers, and cameras. It is characterized by the appearance of interference...

The maintenance of the same scanning relationship between the transmitting scanning spot and receiving scanning spot for each scanning line transmitted in a facsimile system.

The process by which the light from the images of photographic film is encoded into electrical signals for video transmission.

A grinding process that employs fine emery.

A method used to produce precision spherical and aspheric molded glass lenses without grinding or polishing.

A finite version of Shannon's sampling theorem that states that a class of functions can be reconstructed exactly by a sufficient number of spectral samples; the reconstructed function is an explicit...

The process of grinding the concave surface of a single-vision spherical lens.

Agents used for testing light sources and natural daylight with visual and instrumental assessment using a set of white metameric pairs.

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...

The process whereby a rotating wheel carries grains of an abrasive, suspended in a vehicle, across the surface of the optical glass to be ground. The workpieces are forced downward by pneumatic...

Fusion ignition refers to the point in a controlled nuclear fusion reaction where the energy released by the fusion reactions becomes self-sustaining, leading to a continuous release of energy...

A crystalline semiconductor alloy used as the light confinement layer in both single- and double-heterostructure diode lasers.

A binary semiconductor compound used as a substrate or active layer for diode lasers.

A laser system consisting of a planar PN junction within a single crystal of gallium arsenide. The pair of parallel, semireflective end faces produces a Fabry-Perot resonant cavity, whereas the other...

Gallium arsenide phosphide (GaAsP) is a semiconductor alloy composed of gallium (Ga), arsenic (As), and phosphorus (P). It is commonly used in the fabrication of optoelectronic devices, particularly...

Gallium nitride (GaN) is a compound made up of gallium (Ga) and nitrogen (N). It is a wide-bandgap semiconductor material that exhibits unique electrical and optical properties. Gallium nitride is...

The increase in current of a phototube as a result of the gas in the tube becoming ionized.

The masking of all openings of an optical transform -- except the hole at the symmetrical center -- with a thin wire gauze to attain a more precise image.

A crystalline semiconductor material that transmits in the infrared.

Germanium crystal refers to a crystalline form of the element germanium (Ge), which is a metalloid and semiconductor commonly used in various electronic and optical applications. Germanium crystals...

A type of photoconductive detector in which germanium, usually doped with boron, gallium and indium, serves as a semiconductor and can detect up to and beyond 100 µm.

The Golgi staining technique (also called the black reaction) makes it possible to look at the nervous system by rendering neurons visible under light microscopy. After a long process involving...

A spectrometer or autocollimator used to measure prism angles.

An eyepiece having a rotating index or cross wire linked to an external 360° scale to allow measuring of angles in an image.

A device used to measure directional reflectance, with light collection restricted to a narrow range of angles of which the central angle varies.

The graphed curve illustrating the directional reflectance of a sample for different angles of collection.

Harmonic generation refers to a nonlinear optical process in which incoming photons interact with a material and produce new photons at integer multiples of the frequency of the incoming photons....

An instrument designed to calculate the amplitude and phase of the different harmonic elements of a radiation wave utilizing a graph of the wave.

A gas lamp used in the early 1900s as a physical standard for measurement of luminous intensity. The Hefner unit was superseded by the candle and then by the candela.

A method used in facsimile scanning that sweeps the elemental area across the copy in a spiral motion as the result of the movement of a single turn helix against a stationary bar.

In optical communications, the translation of optical signals into radio signals, lowering their frequency in detection from greater than 1014 Hz to less than 1010 Hz, so that further signal...

High harmonic generation (HHG) refers to a nonlinear optical process in which intense laser light interacts with a gaseous medium, typically an atom or a molecule, to produce harmonics of the...

Also known as HCS, an analytical method designed to collect statistically relevant amounts of quantitative data on many parallel cell populations or processes within cells through the combination of...

Histochemical staining is a laboratory technique used in biology and medicine to visualize specific chemical components within biological tissues. This technique involves the application of various...

The dip or gap in the profile of a laser beam's line width when it is both homogeneously and inhomogeneously broadened. When an inhomogeneously broadened spectral line is saturated by incident light,...

The broadening of a laser's line width in a way that affects every atom (or molecule), and thus the whole system, in the same manner. Examples are collision broadening, and natural or intrinsic...

An ocular having two planoconvex lenses that are formed from similar glass and that are separated by a space equal to half the sum of their focal lengths. This eyepiece is free of lateral chromatic...

A gas laser having a mixture of gases that makes it useful in the lab. The mixture of gases flows through a pressure and gas-flow-rate-regulated, sealed vessel with such a gain that only the...

A magnifying lens fitted with a battery-operated lamp by which an object can be conveniently illuminated during observation.

In computer graphics, the coordinated two-dimensional or three-dimensional area of increased resolution where graphics entities may be defined. The screen represents a viewing window for this area,...

A type of electroluminescent display that will record and maintain an irradiated image on its phosphor screen, provided a DC potential is applied to the screen. Used to record x-ray images, the...

A semiconductor material that is used as an infrared detector for light up to 5 µm in wavelength.

An InGaAs (indium gallium arsenide) camera is a type of imaging device that utilizes InGaAs sensors to capture images in the near-infrared (NIR) spectrum. InGaAs is a semiconductor material that is...

An unbounded quantity, an indefinitely large number. Infinity is commonly expressed by the symbol ∞.

In a microscope, a space reserved to accommodate an optical filter or polarizer.

A thermal infrared imaging procedure developed for quality control of printed circuit boards. The thermogram of each board under test is compared with a standard thermal profile and then with a...

Broadening of a laser's spectral linewidth when the resonance frequencies of the atoms (or molecules) of the medium are not homogeneous on the same transition. An example is Doppler broadening.