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799 terms

Photonics Dictionary: C

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conical scan sensor
A device used to determine the location and attitude with respect to the Earth of orbiting spacecraft by detecting the difference in thermal radiance between the Earth's horizon and space.
conjugate autofocus system
A system that determines whether an image is in or out of focus by means of a source of illumination at the conjugate focal point, which reflects off the target; the return beam is mediated by masks...
conjugate focus -> conjugate points
The two points on the principal axis of a mirror or lens so positioned that light emitted from either point will be focused at the other, i.e., object and image points.
conjugate holographic image
Also known as real holographic image. The indistinct, highly distorted image produced on the side of the hologram closest to the observer, in addition to the primary image. When the location of the...
conjugate points
The two points on the principal axis of a mirror or lens so positioned that light emitted from either point will be focused at the other, i.e., object and image points.
conjugate ratio
The ratio between the object distance and the image distance measured along the principal axis of a lens or mirror. An object at the focal point of a lens has an infinite conjugate ratio; an object...
conjugator -> phase conjugation
The use of a reflective device, which can be fashioned from a variety of materials including gases, solids, dyes, aerosols, semiconductor crystals and plasmas, to replicate a laser beam by reversing...
connectome
A connectome refers to a comprehensive map or diagram of neural connections within the brain or nervous system of an organism. It encompasses all the intricate pathways formed by neurons, including...
connector
Hardware installed on fiber cable ends to provide cable attachment to a transmitter, receiver or other cable. Usually a device that can be connected and disconnected repeatedly.
connector loss
Energy loss encountered at connectors in optical fiber transmission systems. The major contributors are mutual core displacement and fiber axis tilt. It is observed in both permanent splices and...
conoscope
An optical instrument, generally a polarizing microscope, that is used to determine the interference figures and optical axis of a sample crystal. Also called a hodoscope.
conservation of radiance
The principle that states that optical instrumentation cannot increase the radiance of a source; the radiance of an image cannot exceed that of the object.
const
constant
constant angle fringes -> Haidinger fringes
Also known as constant angle or constant deviation fringes. The interference fringes observed with dense flat plates near normal incidence. The fringes of the Fabry-Perot interferometer are Haidinger...
constant deviation
That property of certain optical devices, e.g., a penta prism, that maintains the angular relationship between the entering and the emerging rays traversing the system regardless of the orientation...
constant deviation fringes -> Haidinger fringes
Also known as constant angle or constant deviation fringes. The interference fringes observed with dense flat plates near normal incidence. The fringes of the Fabry-Perot interferometer are Haidinger...
constant linear velocity
Method of disk rotation used for optical disk drives, in which the spindle motor decreases the speed of the disk's rotation as the head moves from the inner tracks to the outer, so that the radial...
constant luminance encoder
A device used in broadcast CCD cameras to improve definition in heavily saturated colors by band-limiting the color difference signals after gamma correction.
constant variant enhancement
Technique that uses high-pass filtering to reduce the local average to zero for all regions of the picture and then applies a gain factor equal to the reciprocal of the local standard deviation to...
constrigence
Reciprocal of the dispersive power of an optical material. See Abbe constant.
contact blocking
Also called color blocking. The formation of a block by making optical contact between a number of optical elements and a large optical flat.
contact fluid
A liquid, usually of a specific refractive index and dispersion, serving as an interface between two solids to form a complete light transmission system.
contact fluorography
A fluorographic method whereby the sensitive photographic medium is pressed against a fluorescent screen to form a visible image.
contact laser surgery
Laser surgery by means of a low-power laser system using a synthetic sapphire scalpel that transmits the laser light while in direct contact with the tissue.
contact microradiography
The radiography of small objects having detail too fine to be seen by the unaided eye. The resulting negative, when optically enlarged, can be examined.
contention rate
The maximum number of users who are using a given communication channel. Typically, the number of users at any given time is below this maximum, with the contention rate representing a worst case...
contextual analysis
In optical character recognition systems, the identification of a character facilitated by means of known factors governing its appearance in a particular context; e.g., the first character in the...
continuous dynode electron multiplier -> channel electron multiplier
A photoelectric detector consisting of a glass tube internally coated with a low conductance material. Voltage applied along the tube causes photoemission from the photocathode at the end of the tube...
continuous spectrum
The radiation spectrum of matter found in condensed states, liquid or solid, that is continuous and not a line spectrum. The details of this spectrum are almost independent of the matter emitting the...
continuous wave
Continuous wave (CW) refers to a type of signal or transmission where the signal is constant and does not vary with time. In various contexts, the term is used to describe continuous, uninterrupted...
continuous-wave laser
A laser that emits radiation continuously rather than in short bursts, as in a pulsed laser.
contour analysis
A method in optical character recognition in which a mobile light beam scans the outlines of characters for subsequent reading of these outlines.
contour projection chart
A large-scale, precise drawing of the contours of a perfect mechanical part, often with plus and minus tolerances drawn or indicated. For quality control decisions, enlarged images of mechanically...
contour projector
An inspection device in which the profile of a mechanical part is projected onto a ground-glass screen at a precisely known magnification so that the shape of the part can be compared with a scale...
contouring
Selection of specific brightness values or minimum threshold levels as contingencies for the display of digital data.
contourography
The generation, usually by a cathode-ray oscilloscope, of a two-dimensional image having a three-dimensional appearance.
contrast
The apparent difference in brightness between light and dark areas of an image. For a light target against a dark background, contrast is computed as follows: where Lt is the luminance of the...
contrast control
With respect to television, a potentiometer that allows variation of the intensity of the different elements of an image and that can be used to accentuate the highlights and shadows in an image. In...
contrast filter
A filter designed to improve contrast in an imaging system. For visual and black and white photosystems, a yellow filter is used.
contrast improvement
One area of image enhancement, accomplished by spatial filtering schemes, that usually involves attenuation of phase changes in the complex amplitude over a limited region of the Fourier spectrum of...
contrast threshold
That contrast level that exists between two areas whose difference in brightness is just perceivable.
contrast transfer function -> modulation transfer function
Also called sine wave response and contrast transfer function. The modulation transfer function is the ratio of the modulation in the image to the modulation in the object as a function of frequency...
convergence
1. In optics, the bending of light rays toward each other, as by a convex or positive lens. 2. Turning in the eyes to view a near object. 3. In a television picture tube, the crossing of the...
convergent angle -> angle of convergence
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.
convergent beam sensing mode
A type of photoelectric proximity mode sensing incorporating a lens system to focus the light from the emitter in a small, concentrated spot at a specific point in front of the sensor. Also referred...
converging lens
Also known as convergent lens or convex lens. A lens that converges an incident bundle of rays to a focus.
converging meniscus
A converging lens with one convex and one concave surface.
converging surface
The curved boundary between two optical media of different refractive indices, which causes convergence.
conversion efficiency
In a pumped laser system, the ratio of output energy to pump energy.
convertible lens
Any lens with at least two lens elements, each of which can be used singly or in combined configurations.

Photonics DictionaryC

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