Photonics Dictionary: D

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...

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...

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...

A chart, either printed on paper or prepared photographically on glass plates or film, that consists of 3-bar resolution test objects, sine-wave test objects for modulation transfer function...

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 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...

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...

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

A measure of the sensitivity of a detector; the reciprocal of noise equivalent power (NEP). See D*.

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...

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 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 device that produces an interferogram that can be directly related to the temperature gradient and thereby provides a direct measure of the convective heat transfer coefficients.

The measurement of the spectrum bands formed by a spectroscopic sample, based on the differences between the sample and the reference cell it is placed in.

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...

A measurement device used to study the structure of matter using the diffraction of electromagnetic radiation.

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 instrument used to measure expansion of solids, liquids and gases.

A scale located on the eyepiece focusing screw and used to measure the amount of defocusing of the eyepiece in diopters. The reciprocal of the image distance in meters is a measure of the amount of...

A unit of optical measurement that expresses the refractive power of a lens or prism. In a lens or lens system, it is the reciprocal of the focal length in meters. For example, if a lens has a focal...

A telescopic system having an eyepiece, a reticle and an objective. The instrument measures wavefront power in diopters.

A device that provides simple and reliable laser power and energy measurement. Essentially a heat flux sensor producing an output proportional to the power, rather than the energy input.

A measure of the dispersive properties of a glass. The relative dispersion is defined as: where C, D, and F refer to the material's index of refraction at the three chief Fraunhofer lines in the...

A distributed feedback laser (DFB laser) is a type of semiconductor laser diode designed to emit coherent, narrow-bandwidth light with precise control over the wavelength. It achieves this through a...

A spectroscope having a divided circle and a means for the rapid reversal of prisms for the measurement of refractive index of the prism for a specific wavelength.

A spectrophotometer that measures the amount of ozone in the atmosphere through a comparison of solar energy at two wavelengths in the ozone's absorption band. This comparison is achieved by...

A device used to detect and measure the quantity of exposure to nuclear or x-ray radiation, and dependent on the fact that such radiation ionizes a gas.

A measurement of the spatial resolution of a line or area array in an optical character recognition scanning device.

Measurement derived from calculation when incident flux of a negative is entirely diffuse and all radiation transmissions are included.

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.