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...

A disc contained within an electronic cell counter for regulating light transmission.

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

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...

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...

The minimum of change in stimulation needed to effect an awareness of change in sensation that is statistically determined.

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...

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.

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

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...

Any bending of a wave of radiation away from its expected path, as, for example, by diffraction or by a magnetic field.

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...

A spatial light modulator consisting of a metallized polymer film stretched over an array of metal-oxide semiconductor field-effect transistors (MOSFETs). Each mirror element in the film can be...

A tank with a boiling solvent at the bottom and a ring of cold piping higher up that condenses the liquid and returns it to the bottom. Objects such as lenses or small metal parts to be cleaned are...

The term delta error (delta-E) generally refers to the difference or change in error between two values or states. The word "delta" is often used in mathematics and science to represent a change or...

A compact, folded version of a Dove prism, made of high-index glass with a silvered base and used for image rotation.

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 region at the PN junction in a semiconductor radiation detector where the potential energies of the two materials create an energy barrier, which results in an electrical field that depletes the...

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.

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 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 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...

1. An optical device used for projection of enlarged images of transparencies or lantern slides on a screen. 2. A device designed to hold and backlight transparencies so that their images can be...

A mirror coated to reflect cold (white) light while transmitting hot (infrared) energy.

Dichalcogenides are a class of compounds composed of two atoms of a chalcogen element bonded to a single atom of a metal or metalloid element. Chalcogens are the elements in group 16 of the periodic...

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....

Exhibiting the characteristic of materials that are electrical insulators or in which an electric field can be sustained with a minimum dispersion of power. They exhibit nonlinear properties, such as...

A lidar (light detection and ranging) technique used in pollution monitoring. Two light beams are emitted simultaneously, one at a wavelength that will be absorbed by the target particles, and the...

A spectrograph that uses a diffraction grating as its dispersive element in place of a prism, and yields greater resolving power, more dispersion and a linear spectrum.

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...

1. The ring patterns of light that seem to encircle particles in the field of a microscope. 2. See Newton's rings.

Optical elements that use diffraction to control wavefronts. Diffractive optical elements include diffraction gratings, surface-relief diffractive lenses, holographic optical elements and...

Diffuse reflectance spectroscopy (DRS) is a nondestructive analytical technique used to investigate the optical properties of materials, particularly in the field of spectroscopy. Unlike traditional...

An optical diffuser is an optical component or material designed to scatter or diffuse light that passes through it. It is used to create a more even or uniform illumination, reduce glare, or soften...

Denoting the use of binary notation; i.e., the representation of data by bits (1 or 0).

Digital holographic microscopy (DHM) is an advanced imaging technique that combines holography and digital image processing to capture and reconstruct three-dimensional images of objects. This method...

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...

Digital signal processing (DSP) refers to the manipulation and analysis of signals, which are representations of physical quantities that vary over time or space. In the context of DSP, these signals...

A digital twin refers to a virtual representation or digital counterpart of a physical object, system, or process. This digital replica is created using real-time data and simulation models, allowing...