Photonics Dictionary: D

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...

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...

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...

A diagram in which the variable frequencies of a spectral band system are plotted corresponding to ascending values of the quantum numbers of the upper and lower energy levels.

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...

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...

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 very hard, highly transparent coating based on forms of carbon, used to protect optical components from abrasion and chemical damage.

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....

A waveguide made up of a dielectric material, such as plastic or mica, in a cylindrical form, through which the waves travel.

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...

A viewfinder whose optical system forms a direct image of a subject, as opposed to those systems that use reflectance in the image formation.

The end of an optical fiber farthest from the source of illumination.

Optical fiber capable of operating at both a shorter and a longer wavelength.

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.

A diode laser is a type of laser that uses a semiconductor diode as the active medium to generate coherent light. Semiconductor diodes are electronic devices that conduct electricity primarily in one...

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...

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

A multilayer coating that manifests both a low radiant reflectance and radiant absorption.

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

The transmission of light by a condenser to observe either very small particles or very fine lines with a microscope.

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 spectrum having some lines that are darker than others or that contrast against a light, continuous-spectrum background.

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

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

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...

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

Decibels referenced to one milliwatt; often used to specify power ratings for semiconductor diode lasers.

The concept of the de Broglie wavelength exploits the wave-particle duality of quantum physics by associating all matter (of all sizes) with wavelike properties. The de Broglie wavelength states that...

A device used in ultrasonic imaging to measure the velocity and attenuation of compressional waves in a transparent liquid by virtue of acoustic waves set up in the liquid. The wavefronts serve as a...

1. The grinding or edging of a lens so that the geometrical center and optical center do not coincide. 2. The shifting of an optical element from the system's optical axis, sometimes done on purpose...

In a single element, any lack of coincidence between the optical and the mechanical axes. In a lens system, any lack of coincidence of optical axes of the lens elements that make up that system.

The standard unit used to express gain or loss and relative power levels. The decibel (dB) = 10 log (P2/P1).

An approach to optical character recognition based on matching the input character against a set of stored prototypes.

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...

A CCD device for sensing longer wavelengths, such as NIR and IR, that has a deeper depletion region than would be necessary for sensing in the visible wavelength range. Because the depth of charge...

An optical fiber, usually a single-mode fiber, that has an outer cladding with nearly the same index of refraction as the core and an inner cladding with a very low index of refraction.