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8,289 terms

Photonics Dictionary

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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.

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...

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.

convertible lens

Any lens with at least two lens elements, each of which can be used singly or in combined configurations.

convex lens -> converging lens

Also known as convergent lens or convex lens. A lens that converges an incident bundle of rays to a focus.

convexo-concave lens -> meniscus lens

A meniscus lens is an optical lens that has one side that is concave (curved inward) and the other side that is convex (curved outward). It can be categorized into two types based on its optical...

Cooke triplet lens

The simplest lens in which all primary aberrations may be corrected. It consists of two positive crown elements on either side of, and spaced away from, a negative flint element.

core-coupled lens

A semispherical or conical lens created directly on the core of an optical fiber to focus light from a laser into the fiber core.

corrected lens

A compound lens, the dimensions and materials of which have been so chosen that the lens is appreciably free of aberrations.

cosmic expansion

The ongoing expansion of the universe based on observations of the recession of distant galaxies from each other as evidenced by the redshift in their spectral lines.

Cotton-Mouton constant

Relative to the Cotton-Mouton effect, the magnetic birefringence constant that, when multiplied by pathlength and the square of the magnetic field strength, yields the phase difference between the...

crystalline lens

The internal lens of the eye. It is semielastic to permit changes in its power when focusing on objects at near distances.

current transient

A sudden, brief increase in current or voltage in a circuit that can damage sensitive components and instruments. Preventive measures include slow-starter circuits, filtering and static control.

cylindrical lens

A cylindrical lens is an optical component that has different curvatures along its two orthogonal axes, resulting in a shape resembling a cylinder. Unlike spherical lenses, which have the same...

dark current density

Dark current density refers to the electric current that flows through a semiconductor device in the absence of any external illumination. It is primarily caused by thermal generation of charge...

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...

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 --...

dense wavelength division multiplexing

Dense wavelength division multiplexing (DWDM) is an optical communication technique used to increase the data-carrying capacity of optical fiber networks by simultaneously transmitting multiple...

densitometer

1. An instrument used to measure the opacity or density of dyes, pigments or dispersed particles that form an image in or on a medium, such as a photographic film. 2. A device used to measure the...

densitometry

The detection and analysis of the transmission and reflection properties of objects and photographic images.

density matrix formulation

The exact mathematical description of the interactions of matter and intense electromagnetic fields, such as those that occur when laser sources are used to excite flame gases for spectroscopic...

density -> optical density

A measure of the transmittance through an optical medium. Optical density equals the log to the base 10 of the reciprocal of the transmittance. where τλ is transmittance. In spectroscopy,...

design and engineering consulting services

Design and engineering consulting services refer to professional services provided by specialized firms or individuals to assist clients in various aspects of product development, system design, or...

dielectric constant

A number that indicates the magnitude of the shift in a solid of positive and negative charges in opposite directions when a voltage is applied across the solid.

dielectric lens

A lens made up of a dielectric material that is capable of influencing radio waves much in the same way an optical lens influences light.

diffraction-limited lens

A lens with aberrations corrected to the point that residual wavefront errors are substantially less than one-quarter the wavelength of the energy being acted upon.

diffractive lens

Any optical device that utilizes diffraction in an image-forming capability. Familiar diffractive lenses are zone plates, holographic lenses, kinoform lenses and binary optics.

diffuse density

The logarithm of the reciprocal of diffuse transmittance. Diffuse density results when a sample is diffusely illuminated.

diffuse modulation transfer function

Modulation transfer function of an optical element when used for transporting images from a lambertian source such as phosphors.

diffuse sensing mode

Use of a photoelectric receiver to sense an object's presence by detecting a small amount of the emitter's light that is diffusely reflected by the object.

diffuse transmission

Transmission accompanied by diffusion or scatter to the extent that there is no regular or direct transmission.

diffuse transmittance

The ratio of diffusely transmitted flux to incident flux.

digital densitometry

Pictorial information processing in which the processed picture shows a family of equidensity lines or bands coded with different printed patterns or colors.

Digital Imaging and Communications in Medicine

Digital Imaging and Communications in Medicine (DICOM) is an international standard for medical imaging created by both the National Electrical Manufacturers Association (NEMA) and the American...

direct radiative transition

An energy transition concerned with photons alone.

direct transmission

Light transmission involving no scatter.

discrete cosine transform

A mathematical transformation used in image and video compression that changes two-dimensional representation of data into data defined by the frequency content. Adapted in JPEG and MPEG standards.

dispersive lens -> diverging lens

A diverging lens is a type of lens that causes parallel rays of light to spread out or diverge. It is thinner in the center than at the edges and is commonly referred to as a concave lens. The most...

display console

A visual display used with a computer to give access to the many elements of data as an array of points. With the display console, an operator may check information in the computer and change it if...

distance-luminosity relationship

In astronomy, the relation that states that the intensity of a star's visible radiation is inversely proportional to the square of the distance from which it is viewed.

divergent lens -> diverging lens

divergent-meniscus lens

A lens with one surface convex and the other concave, the latter having the greater curvature. It also is known as a diverging meniscus lens.

diverging lens

Dogmar/Aviar lens

A general-purpose lens, also known as the Celor lens, used widely in photography and commercial processing; it has the form of a triplet with a split flint element.

double diffuse density

Measurement derived from calculation when incident flux of a negative is entirely diffuse and all radiation transmissions are included.

double-concave lens

A diverging lens with both surfaces concave.

double-convex lens

A converging lens with both surfaces convex.

Photonics Dictionary

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