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488 terms

Photonics Dictionary: D

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distributed Bragg reflector
direct current
DC blocking -> zero-order filtering
The removal of the zero-order component of the Fourier spectrum distribution of an object with a small, opaque absorber or reflector in the Fourier plane, to produce images that appear bright on a...
dynamic cross-field photomultiplier
dichromated gelatin
dispersion compensation module
data collection system; digital access and cross-connect systems; dual-cone scanner
doped deposited silica (Corning process)
display electronics
de Broglie wavelength
The concept of the de Broglie wavelength exploits the wave-particle duality of quantum physics by associating all matter (of all sizes) with wavelike properties. The de Broglie wavelength states that...
display electronics assemblies
The removal of optical elements from a block.
Debot effect
The conversion of an internal latent image into a surface latent image through exposure to infrared radiation. The converse of the Herschel effect.
Debye effect
The selective absorption of electromagnetic waves by a liquid made up of molecules with permanent dipole movement.
Debye-Scherrer-Hull method -> x-ray analysis
The series of processes used to identify and evaluate crystal structure by using crystalline solids to diffract x-rays. In the Laue method, radiation of a wide range of wavelengths is transmitted by...
Debye-Sears ultrasonic cell
A device used in ultrasonic imaging to measure the velocity and attenuation of compressional waves in a transparent liquid by virtue of acoustic waves set up in the liquid. The wavefronts serve as a...
1. The grinding or edging of a lens so that the geometrical center and optical center do not coincide. 2. The shifting of an optical element from the system's optical axis, sometimes done on purpose...
In a single element, any lack of coincidence between the optical and the mechanical axes. In a lens system, any lack of coincidence of optical axes of the lens elements that make up that system.
decentration aberration
An aberration occurring in a lens system when one or more of the centers of curvature of the optical surfaces do not coincide with the system's axis.
Sl prefix meaning one tenth, 10-1.
The standard unit used to express gain or loss and relative power levels. The decibel (dB) = 10 log (P2/P1).
The process of reducing the size of an image by removing a certain proportion of the samples produced from the original image.
decision-theoretic character recognition
An approach to optical character recognition based on matching the input character against a set of stored prototypes.
decision-tree classification
A structural method of optical character recognition, used where the input media are variable, as in hand-written or multifont documents. A series of questions (such as "Does the character contain a...
A concave surface that has too much negative power; i.e., its radius of curvature is too short. This condition can be corrected if material is removed from the center section of the polisher.
deep learning
Deep learning is a subset of machine learning that involves the use of artificial neural networks to model and solve complex problems. The term "deep" in deep learning refers to the use of deep...
deep multiphoton microscopy
Deep multiphoton microscopy is an advanced imaging technique used in biological and biomedical research to visualize structures and processes deep within tissues with high resolution. It combines the...
deep ultraviolet
Deep ultraviolet (DUV or deep-UV) refers to a specific range of ultraviolet light with shorter wavelengths than those in the UV-A and UV-B regions. The exact wavelength range considered as DUV can...
deep-depletion CCD
A CCD device for sensing longer wavelengths, such as NIR and IR, that has a deeper depletion region than would be necessary for sensing in the visible wavelength range. Because the depth of charge...
deeply depressed cladding fiber
An optical fiber, usually a single-mode fiber, that has an outer cladding with nearly the same index of refraction as the core and an inner cladding with a very low index of refraction.
defect function -> error function
A single number, defined by the computer program or the user that expresses the performance of an optical system. Also known as merit function and defect function, the error function comprises...
The clarity of an optically reproduced image. Definition is produced by the combination of resolution and acutance.
definition test object
A chart, either printed on paper or prepared photographically on glass plates or film, that consists of 3-bar resolution test objects, sine-wave test objects for modulation transfer function...
Any bending of a wave of radiation away from its expected path, as, for example, by diffraction or by a magnetic field.
deflection circuit
The circuit that regulates an electron beam's deflection in a cathode-ray tube.
deflection focusing
The progressive defocusing of a cathode-ray tube display image that occurs when the deflected electron beam impinges on the cathode-ray tube screen at a slant.
deflection under static load
For an optical table, the amount of displacement that occurs when a heavy load is placed or moved on the surface. To measure deflection under static load, a 113-kg (250 lb) weight is placed in the...
deflection yoke
A metal coil or coils wrapped around the outside of the neck of a cathode-ray tube. Current passing through the coils produces a magnetic field, which can be used as an alternative to deflection...
deformable mirror device
A spatial light modulator consisting of a metallized polymer film stretched over an array of metal-oxide semiconductor field-effect transistors (MOSFETs). Each mirror element in the film can be...
deformation constant
Any of the constants that relate the tendency of the director to remain parallel to restoring torques throughout the media. The three constants of importance in liquid crystal displays are: splay --...
degenerate level
The condition in which two or more energy states are identical.
The gradual decrease over time in output signal with constant input light level.
A tank with a boiling solvent at the bottom and a ring of cold piping higher up that condenses the liquid and returns it to the bottom. Objects such as lenses or small metal parts to be cleaned are...
degree of coherence
A quantitative measurement of the coherence of a light source; equal to the visibility (V) of the fringes of a two-beam interference test: where Imax equals the intensity at a maximum of the...
degrees of freedom
The number of unique ways in which a part can move in an alignment system. In static alignment, there are six: one in the direction of and one in rotation about each of the X, Y and Z axes. In...
SI prefix meaning ten, 101.
Delaborne prism -> 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...
delay distortion
The distortion created because the different frequencies of a signal have different propagation velocities through a medium.
delay line
A device used to delay transmission of a signal for functions such as memory loops, sequential processing or built-in testing. The delay can be achieved by coiling long lengths of coaxial cable or...

Photonics DictionaryD

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