Photonics Dictionary: D

An organizational method used in optical design computer programs. The technique produces one number (merit function) to measure the state of correction of an optical system. This number, which is...

A lightproof box used for storing photosensitive materials.

The current that flows in a photodetector when there is no optical radiation incident on the detector and operating voltages are applied.

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...

A frame taken to identify electronic noise in a CCD imaging device. A dark frame is recorded without exposing the CCD to any external light by, for example, leaving the shutter of a CCD camera...

The noise produced in a photodetector when the photocathode is shielded from all external optical radiation and operating voltages are applied.

An operate mode in which the sensor is programmed to perform a task such as generating output when the light level falls below a certain threshold.

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...

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...

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...

A room that is light-tight, permitting total darkness or illumination with a safelight when working with photosensitive materials.

A data acquisition (DAQ) system is a combination of hardware and software used to collect, process, and analyze data from physical phenomena or processes. data acquisition system suppliers...

An accurate cathode-ray tube display used to provide visual representation stored in a computer for the interpretation and evaluation of the data.

Data analysis software is a category of software tools used for the systematic examination of data sets to uncover patterns, trends, relationships, and insights. It supports a range of analytical...

A system incorporated into fiber optic data communications characterized by several spatially distributed terminals that are served with the same multiplexed signal.

A method of storing digital data using techniques that consume less memory space than basic methods do. See differential pulse code modulation; run end coding; run length coding.

An incandescent or fluorescent lamp whose emittance spectrum resembles that of daylight.

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 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 (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...

A deep-ultraviolet (DUV) laser is a type of laser that emits light in the deep ultraviolet region of the electromagnetic spectrum, typically with wavelengths ranging from about 200 nm down to 10 nm....

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...

The circuit that regulates an electron beam's deflection in a cathode-ray tube.

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.

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...

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 --...

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...

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...

The interval between direction of signal to a light-emitting diode and attainment of 10 percent output current in the photodetector.

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...

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...

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

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...

The range of image distances that corresponds to the range of object distances covered by the depth of field.

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...

Observed electroluminescence of zinc sulfide phosphors when excited by an electric field. This effect is the basis for the alternating-current phosphor panel technology.

1. A device designed to convert the energy of incident radiation into another form for the determination of the presence of the radiation. The device may function by electrical, photographic or...

A detector array refers to a collection of individual detector elements arranged in a two-dimensional grid or matrix format. Each element within the array is capable of detecting electromagnetic...

A detector-Dewar assembly typically refers to a combination of a detector and a Dewar flask used in scientific instruments, particularly in the field of infrared spectroscopy or other applications...

A chemical solution that changes the silver salts (latent image) of exposed photographic film into black metallic silver (visual image).

The process by which a vitreous or amorphous substance forms a crystal structure at a specified temperature.

Dewetting is a phenomenon in materials science and physics where a thin film or coating spontaneously undergoes a process of breaking up and forming isolated droplets on a substrate. This occurs due...

Diamond turning, also known as diamond machining or diamond cutting, is a precision machining process used to produce high-quality optical surfaces and components with extremely tight tolerances. It...