Photonics Dictionary: A

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...

The ratio of aperture area over receiving area for a specific lens. Also called geometric concentration.

A two-lens arrangement intended to image light into a microscope slide sample. The primary aberrations present are red and blue rings observed around the image focus.

A dispersion relation defined in order to value the reciprocal amount of dispersion. It is defined as the refractivity over the difference in index values of the shortest and longest visible...

Image of a uniform source through the sample of a microscope image system. Light from the sample plane is reimaged by the objective into the image plane.

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.

A reflecting prism that inverts the image. The image is reflected four times internally and emitted laterally. The prism is cut normal to the optical axis while the image is internally reflected from...

Designed for the function of optical wavefront analysis. Shack-Hartmann camera aberration sensors use a lens array to image the wavefront to the CCD image plane. Live feedback may be applied through...

Ablation applied to polymers and chemical solids. Process of material removal that minimizes edge damage but will not heat the surrounding portion of the sample.

A high-brightness, short-duration source in which low-pressure gas initiates the discharge to vaporize material from the tube wall, leading to a high-pressure discharge of ionized wall material.

The alteration and reduction of color with the addition of white light. The perceived color shift that occurs as the monochromatic-white combination meets the eye and is interpreted by the brain. The...

Optical surface damage due to abrasive rubbing. Abrasion damage affects are less than the thickness of the optical coating layers. Surface investigation may be achieved by aluminization of the coated...

The minimum value of luminance for vision. The value may vary with age as well as dark adaption period. (Measured range approximately log luminance -3 through 2.) About 10 -2 ml at the fovea, 10 -5...

An optical lens manufactured to control the transmission of light over a specified wavelength range. Low absorption lenses are produced which are anti-reflection coated for UV, VIS and IR wavelengths...

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...

Measures the absorption or sample transmittance over a range of specified wavelengths. Sample may be placed within the device and the transmission measured to an accuracy of given percent. The...

Fraction absorption over a specified range of wavelengths.

The measured change in absorption at a single wavelength while altering experimental parameters such as the incident intensity or pulse width.

An accelerometer is a sensor or transducer that measures the rate of change of velocity of an object, or in simpler terms, it measures acceleration. Accelerometers are widely used in various...

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

A broadband continuum resonator that confines a wide range of wavelengths. From the optical confinement a single wavelength may be released by means of a tuning grating.

Also cellulose acetate film. The emulsion layer applied to the substrate of a photographic surface. The emulsion layer is composed of small particles suspended in gelatin solution.

An achromat, in the context of optics, refers to a type of lens or lens system designed to reduce chromatic aberration. Chromatic aberration is an optical phenomenon where different colors of light...

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.