Photonics Dictionary

A form of roof prism used to invert an image. The prism has faces cut normal to the optical axis; therefore, the prism may be placed within the optical path of a system and invert the image without...

Device which measures the index of refraction of glass as well as the dispersion over visible range.

An absorption peak refers to a sharp increase or spike in the absorption of electromagnetic radiation at a particular wavelength or energy level. It is a distinctive feature in the absorption...

The range of angle or solid angle values by which light may enter an optical system.

A lens consisting of two or more elements, usually of crown and flint glass, that has been corrected for chromatic aberration with respect to two selected wavelengths. Also known as achromat.

Cemented prisms of differing refractive indices which refract incident light and, due to differing refractive indices, will not spatially separate individual wavelengths.

The optical reconstruction of image information contained in a sound field. First the diffraction pattern, formed by an object irradiated by ultrasonic rays, interferes with a mutually coherent...

An acousto-optic modulator (AOM) is a device that utilizes the interaction between sound waves and light waves to modulate or control the intensity, frequency, phase, or direction of laser beams. It...

Adaptive optics (AO) is a technology used to improve the performance of optical systems by reducing the effects of atmospheric distortions. The Earth's atmosphere can cause light passing through it...

A process of color photography in which colors are added one to another in the form of light, rather than as colorants, to obtain color synthesis.

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...

The creation of topographical maps and charts from a stereographic record produced through the overlapping of consecutive aerial photographs by more than 50 percent.

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.

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...

Also known as roof prism. A type of prism designed by G.B. Amici. It consists of a roof edge produced upon the long reflecting face of a right-angle prism. Used as an erecting system in elbow and...

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 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.

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...

An APD detector, or avalanche photodiode detector, is a type of photodetector used to detect light or optical signals by converting incoming photons into electrical current. It operates based on the...

A physical constraint, often a lens retainer, that limits the diameter of the axial light bundle allowed to pass through a lens.

An apochromat, often referred to as an apochromatic lens or apochromatic objective, is a type of optical system designed to minimize chromatic aberration. Chromatic aberration occurs when different...

Displacement in a direction perpendicular to that of the intended displacement, as in a translation stage with simple flexures that experiences vertical displacement during horizontal motion; it is...

An aspheric lens is a type of lens whose surface profiles deviate from the traditional spherical shape. Unlike spherical lenses, which have a constant curvature across their surfaces, aspheric lenses...

An aspheric mirror is an optical mirror surface that deviates from the shape of a perfect sphere, having a non-spherical surface profile. Unlike traditional spherical mirrors, which have a curved...

A gas, such as oxygen, that improves the speed and efficiency of a laser cutter or welder when applied to the work surface, or an inert gas, such as argon, that helps to clean or shield the work...

A lens aberration that results in the tangential and sagittal image planes being separated axially.

An astronomical mirror, also known as a telescope mirror or primary mirror, is a key component of a reflecting telescope. It serves as the primary optical element responsible for gathering and...

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...

An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical elements in a sample by measuring the absorption of light at...

An atomic force microscope (AFM) is a high-resolution imaging and measurement instrument used in nanotechnology, materials science, and biology. It is a type of scanning probe microscope that...

The efficiency of scattering by an atom in a particular direction, expressed as: where AA is the amplitude of the wave from the atom and AE is the amplitude of the wave from a free electron.

An electronic transducer, either fixed or adjustable, that reduces the amplitude of a wave without causing significant distortion. See also beam attenuator.

An autocollimator is an optical instrument used for measuring small angular deviations with high precision. It operates on the principle of autocollimation, where a light source is directed onto a...

Autofluorescence refers to the natural emission of fluorescence exhibited by certain biological structures or molecules when exposed to light. Unlike fluorescence that results from the application of...

A system for automatic industrial process control or measurement, consisting of an optical module for image acquisition, a segmentation processor to isolate the image from its background, and an...

A straight line, real or imaginary, passing through a body and indicating its center; a line so positioned that various portions of an object are located symmetrically in relation to the line. See...

Azimuthal polarization refers to a specific polarization state of light where the electric field vector of the electromagnetic wave points along the azimuthal direction (around the propagation axis)....

The distance from the final optic within a system to the rear image point of the system. See focal length.

The range of frequencies over which a particular instrument is designed to function within specified limits. See also fiber bandwidth.

A negative lens used to increase the effective focal length of a telescope objective.

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

A beamsplitter is an optical device used to divide a beam of light into two or more separate beams, typically by reflecting a portion of the incident light while transmitting the remainder....

An experimental lens used to produce interference fringes. A positive lens is cut into halves along its center, and the halves are separated. This produces a double image of a slit source set...

A type of piezoelectric translator that uses two thin strips of piezoelectric material, one expanding while the other contracts, to produce movement.

Optical elements, often created by micromachining, lithography or vacuum deposition, that rely on diffraction of the collected energy as opposed to the more common refracting or reflecting optics....

Designating any instrument in which both eyes can be used to view the image to achieve a stereoscopic effect, or merely to facilitate observation. See also prism binoculars.

A microscope designed with two eyepieces (oculars), permitting the use of both eyes when viewing through the instrument.

A term pertaining to devices (generally optical) designed for use with both eyes viewing through a single exit pupil. The term may be distinguished from binocular in that biocular instruments contain...

Also called proximity focus image intensifier. A compact image intensifier that utilizes a microchannel plate intensification stage. This is an in-line device that does not invert the image.