Photonics Dictionary: A

With respect to photography, the change in the density-exposure relations, for small details of the photographic image, that is noted when compared with the density-exposure relations for large...

A television format with enhanced vertical resolution (400 lines as compared with the standard 330) that, unlike high-definition television, can operate on existing bandwidths and with existing...

Advanced driver assistance systems (ADAS) refers to a set of safety features and technologies designed to assist drivers in the driving process and enhance overall vehicle safety. These systems use...

An accelerator at the Argonne National Laboratory, providing powerful x-ray beams for materials research applications.

An aerial reconnaissance system that can transmit, in near real time, image data recorded by IR and visual-spectrum sensors, providing day, night and foul-weather intelligence.

Camera designed for the imaging of the earth's surface in order to obtain high quality aerial images

Film designed especially for the needs and conditions encountered in aerial photography. It is produced in a variety of widths, lengths and emulsions.

The use of optical or electronic recording systems to extract information from the terrain, while aloft, for reconnaissance applications.

The creation of a planned sequence of data input that is obtained while airborne for use in aerial photogrammetry and other types of map making and surveying. The data can be photographic, electronic...

Agri-photonics refers to the application of photonics technologies in agriculture. Photonics involves the generation, manipulation, and detection of light and other forms of radiant energy whose...

A category of systems designed to communicate a photo taken from the air (e.g., aircraft, balloon, satellite) to a ground station. It can be done by direct television transmission of the photo, or by...

The equation devised by Sir G.B. Airy for the analysis of light diffraction near a caustic surface: (d2f/dz2) - zf = 0 where z represents the independent variable, and f is the value of the function.

The central peak (including everything interior to the first zero or dark ring) of the focal diffraction pattern of a uniformly irradiated, aberration-free circular optical element or system.

A host crystal for chromium that emits pulsed or continuous-wave laser light, tunable from about 720 to 790 nm.

An alexandrite laser is a solid-state laser that utilizes a synthetic crystal made from the rare earth element alexandrite (BeAl2O4:Cr3+). This crystal is capable of emitting laser light in the...

A precisely defined series of steps that describes how a computer performs a task.

An old name for the rotating arm moving about an axis of rotation over a divided circle used to measure angles. Now the term refers to a small stadia telescope mounted over a ruler for use in...

A laser, usually employing helium-neon or other gases as the active medium, used for alignment in industrial applications.

An optical tooling instrument consisting of an objective lens, a focusing lens, an optical micrometer, a reticle and an eyepiece. The alignment telescope projects a precise line of sight to which a...

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

A form of high-power microscope objective.

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.

A device that enlarges and strengthens a signal's output without significantly distorting its original waveshape. There are amplifiers for acoustical, optical and electronic signals.

Information presented as a continuously variable relationship between a signal and a standard.

A signal in the form of continuously variable voltage or current.

An analog method of moving a cathode-ray tube beam across a display screen face, commonly used in high-performance vector and character generators.

A device that converts an analog signal, that is, a signal in the form of a continuously variable voltage or current, to a digital signal in the form of bits.

An optical device, such as a Nicol prism, capable of producing plane-polarized light, and used for detecting the effect of the object on plane-polarized light produced by the polarizer.

A lens, usually having one or more cylindrical surfaces, used to produce distorted images and later to restore them to true form.

An optical system with different focal lengths or magnification levels in perpendicular planes to the optical axis.

A cylindrical convex viewing mirror used for viewing distorted pictures formed by photographing the reflections of the objects in a similar type of mirror.

A compound lens combination whose astigmatic difference is zero for one or more off-axis zones in the image plane. In such a lens the other aberrations are sufficiently well-corrected to yield...

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.

The angle formed between a ray of light striking a surface and the normal to that surface at the point of incidence.

The angle formed between the normal to a surface and the reflected ray. This angle lies in a common plane with the angle of incidence and is equal to it.

The angle formed between a refracted ray and the normal to the surface. This angle lies in a common plane with the angle of incidence. See also Snell's law of refraction.

The coefficient Å in Angstrom's formula for the dispersing coefficient for dust present in the atmosphere. The formula is expressed as S × Ål-B where l represents wavelength and B...

A system used for measuring direct solar radiation.

An operational mode for radiometers that analogs the method of operation of an angstrom pyrheliometer. In this mode, the rearward-facing cavity is electrically heated, while the forward cavity is...

An angstrom, symbolized by the Ångström or Å, is a unit of length used to express atomic and molecular dimensions. It is equal to 0.1 nanometers or 1 × 10-10 meters. The...

The angle between the most divergent rays that can pass through the lens to form an image. In a birefringent crystal light modulator or Pockels cell, the maximum angle in the incident light rays that...

The angular spectrum approach is a mathematical and computational technique used in the field of optics to analyze and simulate the propagation of optical waves, particularly in the context of wave...

A visual defect that produces a disparity in the sizes of the images formed by the two eyes.

Anisotropic is a term used to describe a material or substance that exhibits different properties or behaviors in different directions. In other words, the physical or mechanical characteristics of...