Photonics Dictionary

The ratio of the radiant power transmitted by an object to the incident radiant power.

The ratio of diffusely transmitted flux to incident flux.

A hologram having an object wave that has been transmitted through the transparent object media to a mirror, reflected again and recorded on a medium.

The ratio of the radiant power transmitted to the second surface of a medium to the corresponding radiant power that has just passed through the first surface. Internal transmittance does not denote...

The greatest luminous transmittance possible for a specified chromaticity.

The part of incident flux that is transmitted with no scattering.

An instrument that uses optical filtration in order to measure the transmittance for a discrete range or specific number of wavelengths.

Measures the absorption or sample transmittance over a range of specified wavelengths. Sample may be placed within the device and the transmission measured to an accuracy of given percent. The...

Transmittance of a stable solution is an exponential function of the concentration of the absorbing solute.

An optical wedge in which transmittance or density is a function of the location of the wedge, relative to a specific optical system.

A colorimeter is a device used to measure and quantify the color characteristics of an object or a light source. It provides objective and standardized color information, typically expressed in terms...

The logarithm of the reciprocal of diffuse transmittance. Diffuse density results when a sample is diffusely illuminated.

A spectrophotometer in which the beam emitted by the radiation source is split into beams that travel through the sample and a reference cell and are subsequently recombined to fall on the detector....

A type of modulation spectroscopy that measures spectral reflectance or transmittance changes induced by applying a perturbing electric field. It can be performed in contactless modes with no special...

An electrostatic device that uses an electric potential barrier to allow the transmittance of electrons at or above a set level of energy while stopping the passage of those below it.

The face of a cathode-ray tube (CRT) that has a fiber optic sheet attached to its surface. The sheet's fibers are at right angles to the face, allowing the transmittance of the fluorescent trace...

The apparent luminance of the image as seen through an optical system. This brightness of the image is determined by the brightness of the object, as well as the transmittance and etendue - or light...

A hollow sphere coated internally with a white diffusing material and provided with openings for incident beam, specimen and detector used for measuring the diffuse reflectance or transmittance of...

With reference to absorbance, absorptance, transmittance and the like, the processes occurring within a specimen between the entry and exit surfaces.

Transmittance of a solution, or internal transmittance of a transparent solid, is an exponential function of the thickness of the layer.

A computer-generated, phase-and-amplitude, off-axis hologram made by a multi-exposure technique that uses three computer generated transmission masks. Each mask controls one fixed-phase component of...

A measure of a material's inability to transmit light, equal to the reciprocal of its transmittance.

A term describing a substance that is impervious to light; the characteristic of a substance that has no luminous transmittance.

A measure of the transmittance through an optical medium. Optical density equals the log to the base 10 of the reciprocal of the transmittance. where τλ is transmittance. In spectroscopy,...

The transmittance of a point on a photographic negative equal to the log to the base 10 of the reciprocal of the transmittance through the negative at that point.

Photocells of various kinds used to measure photometric quantities; i.e., intensity, luminance and illuminance. Meter readings are used to express illuminance and, by calibration, to measure...

Conceptual formulas that characterize both the transmittance functions of lenses and propagation in the Fresnel zone.

The output of spectral channels written as an integral function of known solar irradiance, atmospheric transmittance and camera spectral responsivity, and the unknown spectral reflectance.

An aperture consisting of a semitransparent central region whose amplitude transmittance only is varied, and the relative phase difference between the central and annular region is fixed as p -...

A television system that uses a slow rate of horizontal scanning to increase its reproduction and transmittance accuracy of printed matter, photographs and illustrations.

The spatial distribution of incident and collected flux contained in the analysis of reflectance, transmittance or densities.

Average wavelength usually determined for light-transmitting devices by taking a weighted average for each wavelength of the spectral energy distribution of incident light, transmittance of the...

A wavelength region of relatively high transmittance, surrounded by regions of low transmittance.

A spectrophotometer is a scientific instrument used to measure the intensity of light at various wavelengths in the electromagnetic spectrum, typically in the visible and ultraviolet regions. It is...

The detection and measurement of spectral reflectance, spectral transmittance or relative spectral emittance, relative to wavelength.

See regular transmittance; the term specular is not properly applied to transmission.

The observed time dependence of the transmittance of a step of radiation through a given medium.

A viewer that uses the transmittance of polarized light through glass or a similar medium to examine strained regions. See polariscope.

The equivalent f number of a fictitious lens that has a circular opening and 100 percent transmittance, which would give the same central illumination as the lens being considered: where...

The internal transmittance per unit thickness of a nondiffusing material.

Also known as UV-VIS spectrometer, a device that measures the absorbance, reflectance or transmittance of light in the ultraviolet or visible wavelengths absorbed, reflected or transmitted. Commonly...