Photonics Dictionary: D

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...

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 --...

The condition in which two or more energy states are identical.

The gradual decrease over time in output signal with constant input light level.

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...

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 distortion created because the different frequencies of a signal have different propagation velocities through a medium.

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

Description of a material, such as a water-soluble salt, that will continue absorbing moisture from the surrounding atmosphere until it dissolves into a liquid.

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.

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...

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 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...

A device that obliterates the polarization of a polarized beam by reflecting the beam in all directions at right angles to its axis.

A critical image parameter in applications where object position may change dynamically relative to the imager; this is a sensitive function of the system's preclosed loop (initial) focal range and...

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

The direct appreciation of the distance between a given object and the observer, or between the front and back of a solid object. Real depth perception is achieved by the retinal disparity formed by...

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...

The interaction of superimposed light from two separate sources that results in a combined intensity that is less than the sum of their individual intensities before they were superimposed.

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...

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

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

A discharge lamp filled with deuterium to produce high-intensity ultraviolet radiation for use in spectroscopic analysis.

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...

Able to rotate the plane of polarization of a transmitted, plane-polarized light beam clockwise as seen by a viewer looking in the same direction as the traveling light. Also called dextrorotary; the...

A caustic formed by refraction.

A telescope that corrects dispersion and spherical aberration through the use of one or more lenses, usually smaller than the objective lens, that are positioned at a distance from the objective lens.

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.

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.