Photonics Dictionary: D

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

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 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.

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

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

The removal of optical elements from a block.

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.

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.

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...

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.

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 device used to delay transmission of a signal for functions such as memory loops, sequential processing or built-in testing. The delay can be achieved by coiling long lengths of coaxial cable or...

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...

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...

In optical communication systems, operations in which the amplitude of the pulses, as opposed to their width, determines the distance between repeaters.

A device in which the functions of optical detector and emitter are combined.

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...

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

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...

In an optical rangefinder, the system of wedges that rotate in opposite directions to aid in the detection of deviation in the image axis.

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 dichroic mirror, also known as a dichroic beamsplitter or interference filter beamsplitter, is an optical device that selectively reflects or transmits light based on its wavelength. Dichroic...

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...

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.

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 variation in attenuation among the propagating modes of an optical fiber.

A variation in propagation delay caused by differences in group velocity among modes of an optical fiber. Also called multimode group delay, this effect is commonly due to imperfections or any...

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...

The property of an optical system whereby only the effects of diffraction determine the quality of the image it produces.

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

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

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...

A cosmetic defect on the surface of an optical element. A dig is nearly equal in terms of its length and width. The size is specified numerically by its average diameter in 1/100 of a millimeter;...

A digital camera is a device that captures and records still images or video in digital format. Unlike traditional film cameras, which use photographic film to capture and store images, digital...

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...