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Photonics Dictionary: A

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active element
Component that is externally controlled via electronic or photon signal.
active infrared system
imaging system which clearly shows the IR signals in the field of view as well as ambient environment
active layer
That layer in a semiconductor injection laser or light-emitting diode that provides optical gain.
active medium
A material that produces stimulated emission during the process of amplification with a laser system.
active optics
Technology that corrects the shape of reflective optics; primarily applied in large telescope systems, in order to compensate for slowly varying changes in temperature, wind and mechanical stress.
active region
The layer of material in a laser diode from which the optical radiation is emitted; light producing region
active transport
The transport of molecules in a cell which requires the use of a cell's internal energy. The energy used in the cell may be ATP as a primary transport or an electrochemical gradient give as the...
active-matrix display
A type of liquid-crystal display in which each display element contains an active component, such as a thin-film transistor, to maintain its state between refresh scans.
active-matrix liquid crystal display
When applied to LCD grids, the active matrix is a means of supplying power to pixels by use of a transistor and capacitor. The transistor functions with leads in operation with its respective row and...
active-matrix OLED display
An OLED display that has an integrated electronic backplane as its substrate. Active-matrix OLED displays use at least two thin-film transistors (TFTs) to control the on-current at each OLED cell or...
active-matrix
An OLED display that has an integrated electronic backplane as its substrate. Active-matrix OLED displays use at least two thin-film transistors (TFTs) to control the on-current at each OLED cell or...
activity
1. Synonymous with radioactivity. The intensity of a radioactive source illustrated as the number of atoms disintegrating in unit time, or as the number of scintillations or other effects observed...
ACTS
advanced communication technology satellite
actuator
Mechanical device intended for the translation (rotational and linear) using high precision control from electronically operated circuits. See linear actuator; rotary actuator.
acuity, visual -> visual acuity
The numerical definition of the ability of an observer to perceive fine detail. The average value may be taken as one minute, or 6.7 cycles/mm, at 250 mm (normal viewing distance).
acutance
In photography, the density gradient across an edge separating light from darkness, a physically measurable quantity that correlates well with subjectively observed sharpness of definition. By...
acute bisectrix
In biaxial crystals, the principal angle that bisects the smaller angle between the optic axes.
adaptation
Spontaneous changes to the visual system making it more or less sensitive to light.
adapter
1. In optics, the housing, usually cylindrical, that contains the lenses and iris diaphragm of a camera. 2. In fiber optics, a device for coupling two connectors.
adaptive deconvolution
The process of adjusting input pixel by pixel at the filter plane to adapt to nondeal phase behavior in an optical correlator.
adaptive optics
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...
adaptometer
An apparatus used to determine the degree of adaptation of the eye under different conditions.
ADC
analog-to-digital converter; allyl diglycol carbonate
additive color mixing
Process in which two or more lights are combined by superposition.
additive color process
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.
additive manufacturing
Additive manufacturing (AM), also known as 3D printing, is a manufacturing process that involves creating three-dimensional objects by adding material layer by layer. This is in contrast to...
additivity of luminance
The luminance of a mixture of lights is the sum of the luminances of the component lights in the mixture.
address
The code signifying the location of the information being sought on a CD-ROM.
addressability
In display technology, an expression of resolution given by the number of pixels in both the horizontal and the vertical axes of a cathode-ray tube or similar device.
adhesion
The intermolecular attraction between two surfaces, as between a substrate and a coating; it is an important factor in the durability of optical thin films.
adhesive
An intermolecular substance that serves to hold materials together. Two types are used in the optical industry: one, which must be transparent and colorless, to cement lenses together; and a...
adiabatic laser colorimetry
Method for studying absorption coefficients of low-loss materials, in which a sample is allowed to come to thermal equilibrium with its surrounding blackened enclosure. The sample is irradiated with...
adiabatic process
A process during which no heat enters or leaves the system.
adjacency effect
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...
ADM
adaptive delta modulation; add-drop multiplexer
ADP
ammonium dihydrogen phosphate, adaptive Doppler processing
ADPCM
adaptive differential pulse code modulation; varies the binary step interval for the required bandwidth for a given signal-to-noise ratio.
ADS
angular displacement sensor
ADSL
asymmetric digital subscriber line
adsorption
The process by which a substance, usually a solid, attracts and retains on its surface the molecules of another substance.
adsorption indicator
A chemical placed in a solution that will indicate when an excess of a substance or ion has been reached by coloring the precipitate after the chemical itself has been totally adsorbed.
ADT
automatic data transmission; anthradithiophene
advanced compatible television
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
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...
advanced photon source
An accelerator at the Argonne National Laboratory, providing powerful x-ray beams for materials research applications.
advanced tactical air reconnaissance system
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.
AEL
accessible emission limit
aeolight
A glow discharge lamp consisting of a cold cathode and a mixture of inert gases. The intensity of illumination varies with the applied signal voltage. This lamp was commonly used as a source of...
aerial camera
Camera designed for the imaging of the earth's surface in order to obtain high quality aerial images
aerial film
Film designed especially for the needs and conditions encountered in aerial photography. It is produced in a variety of widths, lengths and emulsions.

Photonics DictionaryA

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