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1,335 terms
Photonics Dictionary
Clear All Filters x
LD x
LD
laser desorption
LDA
laser Doppler anemometry
LDD
laser diode driver
LDEF
Long Duration Exposure Facility
LDR
light-dependent resistor; linear dynamic range
LDS
laser dazzle system
LDV
laser Doppler velocimeter
ablation threshold
The ablation threshold refers to the minimum amount of energy, such as laser energy or intense radiation, required to remove material from a surface through ablation. Ablation itself is the process...
absolute luminance threshold
The absolute luminance threshold is the lowest luminance level of a light source or illuminated object that can be detected by the human eye under specific conditions. This threshold represents the...
absolute purity threshold
Least value of color value combinations which gives white light; minimum purity as determined to be white.
ALD
atomic layer deposition
apparent field
The angular subtense of the field of view in the image space of a telescope, as differentiated from that in the object space (the true field).
averaged threshold receiver
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...
bias buildup
Degradation factor in coherent light systems where the amplitude of the recorded signal is decreased as the number of object points is increased, resulting in poor noise performance.
binary thresholding
An imaging technique that labels all gray pixels as either black or white before processing begins.
binocular threshold
The absolute luminance threshold for detection by the two eyes.
bright-field illumination
The illumination generally used in microscopy, whereby the specimen appears dark against a light background.
bright-field image
An optical image having a brightly lit background.
brightfield
Brightfield refers to a type of microscopy and imaging technique in which the specimen is illuminated with a white light source, and the image is observed or captured against a bright background. In...
cathode-ray tube shield
->
Wehnelt cylinder
Also known as cathode-ray tube grid or shield. A cylindrically shaped electrode that, containing the cathode of a cathode-ray tube with opposite potential, is designed to focus and control the...
cold atom
Cold atoms refer to atoms that have been cooled to extremely low temperatures, typically in the microkelvin (µK) to nanokelvin (nK) range, close to absolute zero (0 Kelvin or -273.15°C). At...
cold cathode
A cathode that emits electrons, not with the influence of heat radiation, but by means of a high-voltage gradient at its surface.
cold coating
A method of applying antireflection coatings to optics that avoids the elevated temperatures normally used. A cold coating will not be as durable as a normal coating.
cold finger
A cryogenically cooled component incorporated into the Dewar of an infrared detector assembly to maintain the sensing elements at the proper temperature (77 K or colder).
cold flow
Deformation of a material caused by mechanical factors, especially constant pressure, and not attributable to thermal effects.
cold mirror
A mirror whose coating serves to reflect visible radiation while transmitting the infrared.
cold shield
That part of an infrared detector-Dewar assembly that limits the solid angle viewed by the sensor; it is maintained at a uniformly cold temperature so that no thermal energy is emitted. Also known as...
cold sputtering
The application of coating without heating of the substrates.
cold-light illumination
A means of illumination from which the infrared component has been removed by absorption or reflection filters within the condenser system.
COLDS
common optoelectronics laser detection system
compression molding
A method of producing large volumes of plastic optical components in which powdered or sheet plastic is pressed between heated dies.
conduction welding
A type of laser welding of thin materials using a defocused or low-power carbon dioxide laser beam. The energy is absorbed by the material through conduction and melts the material to produce an edge...
contrast threshold
That contrast level that exists between two areas whose difference in brightness is just perceivable.
crystal field
The electrostatic field acting locally within a crystal as a result of the microscopic arrangement of atoms and ions in the lattice.
curvature of field
A lens aberration that causes a flat object surface to be imaged onto a curved surface rather than a plane.
dark-field condenser
A condenser that forms a hollow cone-shaped beam of light with its focal point in the plane of the specimen. If it is used with an objective having a numerical aperture lower than the minimum...
dark-field disc
A disc contained within an electronic cell counter for regulating light transmission.
dark-field illumination
The transmission of light by a condenser to observe either very small particles or very fine lines with a microscope.
dark-field microscopy
A technique whereby the sample is illuminated by a hollow cone of light larger than the acceptance angle of the objective, so that only scattered light is seen, revealing any irregularities of the...
dark-field photomicrography
A photomicrographic recording technique that utilizes dark-field illumination to render an image of an object having a refractive index much like that of the medium holding it. The object may be...
depth of field
The distance, on either side of the object plane focused on, through which satisfactory image definition can be obtained. For the special case of an imaging system with lens axis perpindicular to the...
difference threshold
The minimum of change in stimulation needed to effect an awareness of change in sensation that is statistically determined.
ELD
electroluminescent diode
EMRLD
excimer moderate-power Raman shifted laser device
evanescent field theory
A high-frequency approach to the propagation of light in graded-index fibers in which the modal field is represented in terms of an inhomogeneous (evanescent) plane wave with a complex phase, so that...
eye shield
->
eye guard
A shield of rubber, plastic or metal used to protect the eyes of the observer from stray light and wind, and to maintain the proper eye distance.
far-field diffraction pattern
The diffraction pattern of a source such as a light-emitting diode, injection laser diode or the output end of an optical waveguide observed at an infinite distance from the source.
far-field region
A region far from an aperture or source where the diffraction pattern is essentially the same as that at infinity. Changes in diffraction patterns of points within the far-field region are...
fiber optic field flattener
A plate consisting of fused optical fibers with both surfaces ground and polished, and having the entrance surface curved to match the image curvature of the input lens system. The plate transmits to...
field
1. In raster scan television, one of the two scans that are interlaced to make up a frame. 2. See field of view.
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Photonics Dictionary
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