Photonics Dictionary: D

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

A multidimensional array of values that is commonly used in programming to describe a time series of image data. Each dimension in the data cube represents a new attribute, while the cells of the...

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.

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

A tool made by imbedding small particles of diamond in the working edge. In the optical field, the most commonly used diamond tools are glass saws, cup-shaped tools for curve generators, and diamond...

A color filter that is designed to gradually increase or decrease its absorption with wavelength.

In a camera, the focusing of an image on the screen located at the camera's film plane. Once the image is in complete focus, the recording medium is inserted in place of the screen.

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.

A mass spectrometer utilizing both radial electrostatic and magnetic field analyzers to improve the focusing and increase resolution.

See periscopic lens; rapid rectilinear lens.

A technique used in astronomy that requires a radio telescope to be directed at a point in the sky west of the object under observation. The Earth's rotation causes the object to drift through the...

The minimum electrical current input needed to initiate lasing.

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...

A telescope similar to the customary Cassegrain telescope, but having a primary mirror that is ellipsoidal and a secondary that is spherical.

A Dammann grating is a type of diffractive optical element (DOE) used to create an array of equally spaced, uniform-intensity spots or beams. It is named after its inventor, Dr. Herbert Dammann. The...

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...

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

The selective absorption of electromagnetic waves by a liquid made up of molecules with permanent dipole movement.

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.

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 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 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...

The clarity of an optically reproduced image. Definition is produced by the combination of resolution and acutance.

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...

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...

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

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 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...

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.

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...

An evacuated, double-walled container for storing liquids at low temperatures. Often made of glass, the vessel resembles a Thermos bottle.

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 refers to a precision machining process used to produce complex optical components, particularly lenses and mirrors, from materials such as metals, plastics, and crystalline materials...

A flanged or plain ring with a restricted aperture, located in an optical system at any of several points, that cuts off marginal light rays not essential to image formation. Diaphragms are used as...

A dichroic coating, also known as a dichroic filter or dichroic mirror, is an optical coating designed to selectively transmit or reflect certain wavelengths of light while simultaneously absorbing...

A polarizer that consists of dichroic polarizing material embedded in a plastic sheet, and that transmits light that is almost completely plane polarized with an intensity that is half that of the...

Dichroism refers to the property of certain materials to exhibit different colors or absorbance of light depending on the direction of light propagation or polarization. The term is commonly used in...

Die bonding is a critical process in semiconductor manufacturing and microelectronics assembly, where a semiconductor die or chip is attached and electrically connected to a substrate or a package....

Differential interference contrast (DIC) microscopy, also known as Nomarski interference contrast microscopy, is an optical imaging technique used in microscopy to enhance the contrast of transparent...

The slope of the curve when output is plotted against input for quantum efficiency in a device.

Diffraction efficiency is a measure of how effectively a diffractive optical element (DOE) or diffraction grating directs light into specific diffraction orders or achieves a desired optical effect....

A diffraction grating is an optical component consisting of a surface with a periodic structure of equally spaced, parallel grooves or rulings. These rulings act as an array of closely spaced slits...

Elastic scattering that occurs when inelastic processes eliminate particles from the beam.