Photonics Dictionary

A photocell having an alloy junction formed by combining an indium disc with a thin wafer of N-type germanium.

Charged frozen pellets that are rapidly bombarded with a focused high-power laser to form a dense plasma that can be heated and sustained with neutral beams.

The angle between an instrument's line of sight and a reference horizontal plane.

A system used for measuring direct solar radiation.

The point of a planet or comet's orbit that is farthest from the sun.

The angular subtense of the field of view in the image space of a telescope, as differentiated from that in the object space (the true field).

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...

An astronomical telescope is a type of optical instrument designed to gather and magnify light from distant celestial objects for observation and analysis. It typically consists of two main optical...

Formulaic compensation to correct laser ranging data for the effects of horizontal refractivity gradients; it requires the horizontal pressure and temperature gradient at laser sites, which are...

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

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

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

A channel for communication with the source in an otherwise unidirectional network, such as a channel that provides interactive features in a cable television network.

A photovoltaic cell designed so that light travels through the front electrode and a semiconductor before it comes to the barrier layer.

A filter that suppresses a given range of frequencies, transmitting only those above and below that band. Also called bandstop filter.

The negative distortion that causes a square grid pattern to be imaged as barrel-shaped.

The distance between pupil centers in a two-pupil system, measured perpendicularly to the optic axis.

The smallest amount of photon energy to pass a detector window and be counted.

Activity of a radionuclide having one spontaneous nuclear transition per second.

The intensification of a latent image, because of exposure to light to which the emulsion is otherwise insensitive.

In optics, a collapsible structure situated between the lens and film of a camera to allow variation of the distance between them while preventing surrounding light from exposing the film.

Two formulas used in diffractometer analysis, the first giving the individual diffraction patterns of each aperture, the second representing the constant of the degree of an incoherent circular...

A chamfer ground on the edge of a lens or prism. Bevels are used to prevent chipping or to achieve a mechanical fit.

The actual width of a bevel rather than its width projected along the lens aperture.

The level of the television picture signal that corresponds to the maximum limit of black peaks.

The light wavelength for which the direction of reflectance from the groove face is identical to the angle of diffraction for a specified angle of incidence.

The law given by the formula: that is, the frequency of radiation emitted or absorbed by a system when E2 and E1 are the energies of the states among which transition takes place, and h is...

The illumination generally used in microscopy, whereby the specimen appears dark against a light background.

An optical image having a brightly lit background.

Brightfield refers to a type of microscopy and imaging technique in which the specimen is illuminated with a white light source, and the image is observed or captured against a bright background. In...

Broadband dielectric mirrors, also known as broadband mirrors, are optical coatings designed to efficiently reflect or transmit light over a broad range of wavelengths. These mirrors are constructed...

A photoconductive cell having cadmium sulfide as its photoconducting material for the production of a very high dark-light resistance ratio.

SI unit of luminous intensity. It is defined as one sixtieth the normal intensity of one square centimeter of a blackbody at the solidification temperature of platinum. A point source of one candela...

Envelopes for cathode-ray tubes are made by blowing glass in the same manner as light bulbs. They have a fairly flat end face to carry the phosphor material applied internally.

1. A single unit in a device for changing radiant energy to electrical energy or for controlling current flow in a circuit. 2. A single unit in a device whose resistance varies with radiant energy....

A photoemissive detector sensitive to wavelengths up to 1 µm. It has one sharp maximum of sensitivity at 350 nm and a broad maximum at 800 nm.

The number of channels per unit bandwidth handled by a single optical fiber.

A photoelectric detector consisting of a glass tube internally coated with a low conductance material. Voltage applied along the tube causes photoemission from the photocathode at the end of the tube...

The parallel resistance and capacitance appearing between the active guard ring junctions in a silicon photodiode.

The creation of a diode laser structure by liquid-phase epitaxy over a grooved substrate.

A laser having a rare-earth chelate within a plastic host as the lasing material. The chelate laser is easily pumped and has a high quantum efficiency and narrow emission lines.

Any of several compounds capable of binding heavy-metal ions, thereby preventing interaction between the bound ions and the rest of the medium.

A television system that does not broadcast television signals but transmits them over a closed circuit.

A plane mirror mounted on a polar axis that lies parallel to the plane of the mirror. When the mirror is rotated once in 48 hours, celestial objects can be made to appear stationary and are...

That part of an infrared detector-Dewar assembly that limits the solid angle viewed by the sensor; it is maintained at a uniformly cold temperature so that no thermal energy is emitted. Also known as...