Photonics Dictionary

A photometer used to measure sky brightness and polarization associated with zodiacal light, background starlight, F-region airglow and spacecraft corona.

Also called Geiger-Müller counter. An instrument designed to detect and measure radioactivity through the use of a gas-filled metallic tube containing a needle electrode. Radiation traveling...

A specific gas-filled tube designed to illustrate the luminous effects of discharges through rarefied gases.

A rapid roughing process for the quick removal of glass, the first step in manufacture of a curved lens surface. It is accomplished with coarse emery or a diamond-impregnated tool.

The curved mark formed when, in the process of generating, a loose or coarse diamond particle from the generating tool scores the work so deeply that subsequent fine grinding or polishing cannot...

A device used to lock the internal synchronization generator of a television camera to an external source.

Trade name referring to an instrument that determines surface distances by measuring the length of time it takes for a modulated lightwave to reach a mirror and be reflected to its point of origin.

The physical center of the lens; it is on the axis of the lens, halfway between the front and rear vertex. It is sometimes referred to as the mechanical center of the lens.

The position and shape of the image of a point source, as predicted by geometric optics alone. The geometric image is to be differentiated from the diffraction image, which is determined from...

Metamerism that occurs when the geometry of illumination or viewing is changed.

In image processing, mathematical operations that change spatial geometry, as for instance scaling, translating, rotating or otherwise manipulating the perspective. Also called geometric manipulation.

A field of physics that deals with light as if it truly were composed of rays diverging in various directions from the source and abruptly bent by refraction or turned by reflection into paths...

A technique used to create an achromatic phase shift based on the principle of geometric phase. The phase shift is experienced by a light beam as a result of a cyclic change in its state of...

The area of optics in which the propagation of light is described by geometrical lines (or rays) governed by Fermat's Principle. Geometrical optics is useful as long as the objects in which the light...

The superposition of satellite or aerial images with a map in order to process and remove distortion. Uses reference points from map to align and apply information.

A man-made satellite that orbits 35,680 km from the Earth at a rate of one orbit per 24-hour period, thereby retaining its initial relative alignment with the Earth.

A type of glass used in near-infrared optical components, in which germanium is used as a cation instead of silicon.

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.

Germicidal ultraviolet (GUV) refers to a specific range of UV radiation that has disinfectant properties capable of killing or inactivating microorganisms, including bacteria, viruses, and fungi. The...

In vacuum deposition, a device that removes contaminants from the vacuum chamber.

An instrument that uses optical filtration in order to measure the transmittance for a discrete range or specific number of wavelengths.

A doped or absorbing transparent medium cut or molded into a wedge in order to measure the real and imaginary components of the refractive index. An internally reflected Gaussian beam is interfered...

That image remaining on the detector after the primary stimulus has been removed. In the visual system, the after-image commonly appears as the complementary color of the primary stimulus.

Left- and right-hand circularly polarized beams that are produced at different velocities by passing plane-polarized light through an optical substance. When recombined, they exhibit different phases...

In computer graphics, a character generator that produces alphabetical and numerical characters with some punctuation and symbols.

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

An angle formed by the lines of sight of both eyes when focusing on an object. Also, the rate at which a ray approaches the optical axis.

An antigen is any substance that is capable of triggering an immune response in an organism. Antigens are typically proteins or large polysaccharides, although other types of molecules can also act...

The point on an elliptical orbit about the Earth that is the farthest distance from the Earth.

The electric arc that is a particular discharge between two electrodes in a gas or vapor which is characterized by high cathode densities and a low voltage drop.

The ability of a machine to perform certain complex functions normally associated with human intelligence, such as judgment, pattern recognition, understanding, learning, planning, and problem...

The particular orientation of the image, such as normal, canted, inverted or reverted.

Localized variations in the purity and the index of refraction of the atmosphere.

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.

In a pulsed laser, the pulse energy in joules times the repetition rate in hertz.

A receiver for optical communications systems consisting of a symmetric binary, pulse-code-modulated transmitter, a log-normal channel and an array of independent photocounting detectors that yield...