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8,289 terms
Photonics Dictionary
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doma
A primitive crystal possessing two plane surfaces that form a dihedral angle bisected by another plane surface.
dominant wavelength
A single wavelength of light that matches the color of a given sample when combined in suitable proportions with white light and a suitable adjustment of intensity.
donor
An impurity in a material that is capable of inducing electrical conduction in that material by transferring an electron to the conduction band.
donpisha
A type of asynchronous shutter device that is used particularly in CCD sensor applications to capture an image of a high-speed subject with no time delay. The word donpisha is taken from the Japanese...
dopant
The impurity added to a substance to produce desired properties in the substance.
doping
In the context of materials science and semiconductor physics, doping refers to the intentional introduction of impurities into a semiconductor material in order to alter its electrical properties....
Doppler broadening
The spreading of potentially equal radiation frequencies that results in broadening of the spectral line. This effect is brought about when radiating atoms, molecules or nuclei have different...
Doppler effect
The effect produced on a wave frequency because of the relative motion of a source or an observer. The radiation emitted from a source that moves away from an observer appears to be of lower...
Doppler principle
The theory established by Christian J. Doppler in 1842 that states that the rate of change in distance between a perceiver and a radiation source determines the change in frequencies.
Doppler shift
The magnitude, expressed in cycles per second, of the alteration of the wave frequency observed as a result of the Doppler effect.
Doppler signal
A signal traveling from transmitter to receiver that has an altered frequency due to the Doppler effect.
Doppler velocimeter
->
laser Doppler velocimeter
Device which determines particle velocity through the measurement of scattered interference of a beam pair from a single source. The measured light is Doppler shifted which provides information...
Doppler-Fizeau principle
The principle stating that the displacement of spectrum lines is determined by the distance between, and relative velocity of, the observer and the light source. When distance decreases, the lines of...
Doppler-spread imaging
An imaging process, similar to specific Doppler mapping radar techniques, that utilizes a laser, an optical imaging system, and a line array of photodetectors and spectrum analyzers. The laser...
dosage meter
->
dosimeter
A device used to detect and measure the quantity of exposure to nuclear or x-ray radiation, and dependent on the fact that such radiation ionizes a gas.
dosimeter
A device used to detect and measure the quantity of exposure to nuclear or x-ray radiation, and dependent on the fact that such radiation ionizes a gas.
DOT
designating optical tracker
dot matrix display
A display format consisting of small light-emitting elements arranged as a two-dimensional array. Various elements are energized to depict a character. The typical matrix is 5 x 7 dots.
dots per inch
A measurement of the spatial resolution of a line or area array in an optical character recognition scanning device.
double image
->
GHOST
global horizontal and sounding technique
double refraction
The separation of unpolarized light into two plane-polarized elements by a doubly refracting crystal. When a crystal, such as calcite, is placed between the eye and a pinhole in a card, two bright...
double slit
A pair of long, slender parallel apertures used in experiments on diffraction and interference.
double vision
A defect of a binocular instrument causing two images to be seen separately instead of being fused. It is caused when the optical axes of the two telescopes are not parallel. In minor cases, the eyes...
double-beam CRT
A cathode-ray tube that either splits an electron beam from one source or uses beams from two sources to produce two beams, each of which can produce separate traces, but which can overlap.
double-beam spectrophotometer
A spectrophotometer in which the beam emitted by the radiation source is split into beams that travel through the sample and a reference cell and are subsequently recombined to fall on the detector....
double-clad fiber
Double-clad fiber (DCF) is a specialized optical fiber that features two concentric cladding layers surrounding a core. The design of double-clad fibers allows them to be used in various...
double-crucible method
A method of fabricating an optical waveguide by melting the core and clad glasses in two suitably joined concentric crucibles and then drawing a fiber from the combined melted glass.
double-discharge laser
A type of transversely excited laser with a uniform arc-free discharge of large cross-sectional area that can be scaled to very large systems.
double-exposure holography
The formation of an interferogram by means of two holograms on the same recording medium, often used for determining small changes in an object. One hologram produces a primary image that constitutes...
double-focusing mass spectrometer
A mass spectrometer utilizing both radial electrostatic and magnetic field analyzers to improve the focusing and increase resolution.
double-image prism
A prism block that, when used with a lens, is capable of forming two images of one object.
double-layer light amplifier
A device used to create a light output that exceeds light input, the energy being provided by an electric field. It consists of a photoconductive layer with an electroluminescent layer between plates...
double-layer screen
A CRT screen on which two phosphors differing in color and persistence are deposited.
double-pulsed holographic interferometry
Interferometric measurement of the interference pattern recorded when a complex object is illuminated by two laser pulses that interfere and form the pattern to be evaluated.
double-pulsed holography
Holographic recording whereby the object is illuminated by two pulses, separated by a time interval, from a Q-switched laser source. Each pulse is divided into reference and object beams, and...
double-raster format
A mode of laser printing in which each pixel is printed four times, providing sharper lines and a continuous tone from one-quarter the amount of image data, compared with single-raster output.
double-window fiber
Optical fiber capable of operating at both a shorter and a longer wavelength.
doublet
1. A compound lens consisting of two elements. If there is an air space between the elements it is called an "air-spaced doublet.'' If the inner surfaces are cemented together, it is called a...
doubly refracting crystal
A transparent crystalline substance that is anisotropic relative to the velocity of light.
Dove prism
A form of prism invented by H.W. Dove. It resembles half of a common right-angle prism in which a ray entering parallel to the hypotenuse face is reflected internally at that face and emerges...
DPCM
differential pulse code modulation
dpi
dots per inch
DPPM
dynamic pulse position modulation
DPSK
differential phase shift keying
DPT
digital piezoelectric translator
DQE
detective quantum efficiency
DRA
discontinuously reinforced aluminum
DRAM
dynamic random access memory
drawing tower
A system for fabricating optical fiber, consisting of a furnace that heats the materials, a polymer coating stage, a capstan-pulling apparatus that free-draws the preform into a fiber and a drum on...
drift
A gradual change in the output of a circuit or instrument over time.
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Photonics Dictionary
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