Photonics Dictionary

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...

Angular deviation from the optimum alignment of source to optical waveguide, waveguide to waveguide, or waveguide to detector, resulting in a loss of optical power.

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...

The measured planar or solid angle of related aspects of an optical system with respect to an optical axis.

A laser radar application in which a sequence of direct measurements of target position is fed into a tracking filter to produce refined estimates of both present and future target positions.

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

A light source that emits an uneven distribution of radiant energy through the visible range.

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...

Anisotropy refers to the property of exhibiting different values or characteristics when measured in different directions. In various fields, including physics, materials science, and geology,...

The process of heating and slowly cooling a solid material, like glass or metal, to stabilize its thermal, electrical or optical properties or, as in semiconductor materials, to reverse lattice...

An oven or furnace that possesses the design requirements and heat control necessary to anneal glass for the optical industry.

Gamma ray radiation released when matter and antimatter, such as electron and positron, unite and eliminate each other, transforming completely into energy. The resulting gamma ray spectrum depends...

A type of solar eclipse that occurs when the sun is at perihelion and the moon is at apogee. Because the apparent size of the moon is insufficient to cover the sun, the outer edge of the solar disc...

The part of an electrical circuit in which the electrons leave (a cathode-ray tube) or enter (an electrolytic cell) a unit in the circuit.

An optical instrument that uses a yellow light of varying intensity with red and blue lights of fixed intensity to test for colorblindness.

Dispersion that occurs when the medium's index of refraction decreases as the frequency of the propagating light increases. For a given medium, some wavelength ranges may produce anomalous dispersion...

A spectral phenomenon in which the degree of the photoresponse of an illuminated semiconductor is determined by the wavelength composition of the incident light.

Irregular propagation of a wave due to variations in the medium's density or refractive index.

Color vision whereby abnormal proportions of three colors are needed for color matching.

Having human characteristics or behavior.

In image processing, methods of reducing image defects that result from false data. Techniques include sampling, linear intensity, filtering a high-resolution image to produce a low-resolution image,...

Characteristic of an absorber in the IR region, whereby absorption increases as a direct function of the intensity of the incident, continuous radiation.

A device that prevents electrons from a saturated pixel in a CCD imaging device from spilling into an adjacent pixel. The antiblooming gate drains a pixel of any charge in excess of its full-well...

The elimination of magnetic moments and decrease in magnetic susceptibility with a decrease in temperature due to the equal power of atomic magnets.

A coating that is capable of stopping the condensation of moisture on an optical surface.

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...

A waveguide that has a core with a lower refractive index than the refractive index of the cladding. This structure can limit the power of the transmitted beam by removing unwanted radiation, for...

Light-absorbing material that is applied to the back support of any bright image under inspection to prevent the formation of a secondary image.

An antireflection coating (AR coating) is a thin film or coating applied to optical surfaces, such as lenses or windows, to minimize unwanted reflections and increase the transmission of light...

Literally the opposite of resonance, antiresonance occurs when any variation in excitation frequency results in an increased response.

The point to which the extension of the straight line, reaching from the sun to the observer's eye after penetrating the atmosphere of the Earth, is projected.

An electrically conductive layer for carrying off static charges that might accumulate on a surface.