Photonics Dictionary

A liquid, usually of a specific refractive index and dispersion, serving as an interface between two solids to form a complete light transmission system.

A fluorographic method whereby the sensitive photographic medium is pressed against a fluorescent screen to form a visible image.

The maximum number of users who are using a given communication channel. Typically, the number of users at any given time is below this maximum, with the contention rate representing a worst case...

The radiation spectrum of matter found in condensed states, liquid or solid, that is continuous and not a line spectrum. The details of this spectrum are almost independent of the matter emitting the...

Continuous wave (CW) refers to a type of signal or transmission where the signal is constant and does not vary with time. In various contexts, the term is used to describe continuous, uninterrupted...

A method in optical character recognition in which a mobile light beam scans the outlines of characters for subsequent reading of these outlines.

A large-scale, precise drawing of the contours of a perfect mechanical part, often with plus and minus tolerances drawn or indicated. For quality control decisions, enlarged images of mechanically...

Selection of specific brightness values or minimum threshold levels as contingencies for the display of digital data.

The apparent difference in brightness between light and dark areas of an image. For a light target against a dark background, contrast is computed as follows: where Lt is the luminance of the...

A filter designed to improve contrast in an imaging system. For visual and black and white photosystems, a yellow filter is used.

One area of image enhancement, accomplished by spatial filtering schemes, that usually involves attenuation of phase changes in the complex amplitude over a limited region of the Fourier spectrum of...

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...

Also known as convergent lens or convex lens. A lens that converges an incident bundle of rays to a focus.

Convex is an adjective used to describe a surface or shape that curves outward, bulges, or has a rounded and outwardly extending appearance. In the context of geometry or optics, a convex shape is...

A powerful and flexible machine-learning approach that can be used in machine vision to help solve difficult problems. Inspired by biological processes, multiple layers of neurons process portions of...

A telephoto lens form noted for its lack of distortion.

An early type of nonvacuum photocell consisting of a layer of copper oxide on a metallic substrate, with a thin transparent layer of a conductor over the oxide. When light falls on the cell, a small...

A threadlike inclusion within a blank of optical glass. Rarely found in quality optical materials.

A semispherical or conical lens created directly on the core of an optical fiber to focus light from a laser into the fiber core.

A corner cube, also known as a corner reflector or retroreflector prism, is a type of optical device used to reflect light or electromagnetic waves back towards their source with minimal deviation in...

The removal of a slight overlap that may be found on a blank or pressing.

A compound prism formed by cementing together two 30° prisms, one of right-handed and one of left-handed quartz. It has good ultraviolet-transmitting qualities and no double refraction.

A prism formed by dividing a Nicol prism in a plane parallel to the path of vibration of the transmitted light and taking out the wedge-shaped piece. After the pieces are rejoined, the planes of...

An optical wedge of very small angles that admits light while sealing out moisture and dirt and that may be rotated to compensate for the errors in the entire system. Correction windows are sometimes...

An optical element designed to correct each zone of a reflector or refractor for spherical aberration.

A technique for removing thermal noise and drift from focal plane assemblies by sampling the system output between views of scene elements and then subtracting the resulting value from the subsequent...

Bohr's formulation that every new theoretical principle must correspond to the salient classical predecessor. The principle imposes mathematical limits on theoretical discovery and implies, for...

Translucent collector developed to compensate for the partial blocking of a flat surface's collection angle that normally occurs in spectroradiometry. The device samples radiant flux according to the...

A set of mirrors along a telescope's polar axis designed to redirect light to a fixed position without being affected by the motion or position of the telescope. From the French word for "elbow."

The scattering of charged particles, moving through matter, by the electrostatic force exerted by other charged particles.

The concave portion of a surface, formed on a blank, on which the disk of higher refractive glass will be fused to form a multifocal spectacle lens.

A rangefinder on a camera that is integrated with the focusing mechanism so that when an object's range is determined, the camera is automatically in focus.

1. In color development, the chemical that combines with certain by-products of the development procedure to form a dye. 2. Device for distributing optical power among two or more ports. 3. Device...

A crystal formed by covalent bonds that are generally highly directional by nature. The electric characteristics of these crystals classify them as semiconductors.

A coverslip, also known as a cover glass or cover slip, is a thin and flat piece of transparent material typically made of glass or plastic. It is used in microscopy to cover a specimen mounted on a...

The deformation of a material at high levels of stress, often associated with elevated temperatures.

Cresyl violet, also known as cresyl violet acetate or cresyl echt violet, is a synthetic organic compound belonging to the class of triarylmethane dyes. It is commonly used in histology and...

In an optical system, the aperture size at which the lens gives its best overall performance.

Recombination of only the light that is correctly dispersed by the first stage of a polychromator through its wide intermediate slit (common during Thomson scattering experimentation), which is...

Fine lines, wires or threads used in the focal plane of many optical instruments to point out and locate particular objects in the field of view. They were formerly made from a single strand of...

A surface scratch or series of scratches formed by mishandling.