Photonics Dictionary: D

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...

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...

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...

Deep multiphoton microscopy is an advanced imaging technique used in biological and biomedical research to visualize structures and processes deep within tissues with high resolution. It combines the...

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 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...

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 square of the ratio of the measured detectivity to the theoretical maximum detectivity.

The process by which a vitreous or amorphous substance forms a crystal structure at a specified temperature.

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 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 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...

Exhibiting the quality of dichroism.

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...

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...

The ratio between two given absorption coefficients.

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 device used to investigate the dichroism of crystals.

An eyepiece used in a polariscope or polarizing microscope to give a comparison view of the same object under illumination by the two complementary rays of polarized light.

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 shallow, fine-pitch diffraction grating having a precise dielectric overcoating that experimentally has absorbed wavelength-specific incident light that is polarized in the P-plane.

A high-reflectance coating consisting of alternating layers of quarter-wave film of a higher refractive index and lower refractive index than the substrate. Such coatings can be made very specific to...

A number that indicates the magnitude of the shift in a solid of positive and negative charges in opposite directions when a voltage is applied across the solid.

A crystal that is characterized by its relatively poor electrical conductance.

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

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 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....

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

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...

The scanning of photographs or transparencies of images, either by a vidicon camera or flying spot scanner, for the conversion of the images to digital form for storage on magnetic tape.

An optical system that uses refraction to form an image.

The branch of optics that deals with the study of the refraction of light, particularly by the transmitting medium of the eye, and by lenses.

Interferometric measurement of the interference pattern recorded when a complex object is illuminated by two laser pulses that interfere and form the pattern to be evaluated.

A microscope that has been modified to permit the quantitative analysis of dust samples.

A type of erasable data storage device that uses a medium deposited on the disc in two layers, each dyed to absorb a different wavelength of laser light. To record data, the lower layer is heated by...

The superimposition of a pilot object on each hologram. The fixed relative position of the scanning and pilot beam during the recording process ensures that sensing and fixing the pilot beam position...

Stress applied to an optical fiber at a constant rate.