Photonics Dictionary: D

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

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

Light emitted by one or more sources and characterized by a high degree of scatter.

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...

In image processing, a device that transforms the digital data into an analog video image that can be viewed on a monitor or printed.

Light produced by visible radiation that moves from the light source to the object without reflection. With respect to microscopy, this is the light that directly strikes the stage of the microscope...

Reflectance in a specified direction, for a specified direction of incident illumination.

The degree to which a vision system is capable of sensing differences in light intensity between two regions.

A circuit incorporated into counter systems that records only pulses that have amplitudes between two preselected limits.

In optics, the production of maxima and minima by the superimposition of two sets of interference fringes from light of two different wavelengths.

Atmospheric aberration caused by the Earth's rotation; the degree varies from 0 at the poles to a maximum of 0.31 s of arc at other locations.

Phase shift in electromagnetic signals caused by daily variations in the ionosphere, often during sunrise or sunset.

A single wavelength of light that matches the color of a given sample when combined in suitable proportions with white light and a suitable adjustment of intensity.

A signal traveling from transmitter to receiver that has an altered frequency due to the Doppler effect.

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.

An optical correlator incorporating a binary phase-only spatial light modulator made from an iron garnet magneto-optic solid crystal and used in target recognition systems.

A spectroscopic technique used to display the intensity of an optical pulse as functions of time and frequency simultaneously.

A type of mosaic detector array that combines features of scanning and staring sensors by using a small rapid scanning motion (see saccadic motion) over a few pixels at a time.

The theoretical explanation and analysis of the interactions between electron waves and crystals used in studying electron diffraction.

In electrical equipment, power variations that are temporary (as opposed to the permanent, cumulative effects of drift).

A value used to designate the relative sensitivity of a detector. The higher the D* value, the better the detector.

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 ability of the human eye to adjust itself to low levels of illumination.

In a gas, an electrical discharge that has no luminance.

A frame taken to identify electronic noise in a CCD imaging device. A dark frame is recorded without exposing the CCD to any external light by, for example, leaving the shutter of a CCD camera...

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

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 room that is light-tight, permitting total darkness or illumination with a safelight when working with photosensitive materials.

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...

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...

The conversion of an internal latent image into a surface latent image through exposure to infrared radiation. The converse of the Herschel effect.

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...

The process of reducing the size of an image by removing a certain proportion of the samples produced from the original image.

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...