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radiance Dictionary Terms

cosine law of illumination
Law relating the illuminance (or irradiance) of a surface to the cosine of the angle, q, between the normal to the surface and the direction of the incident wave.
minimum spot size
The smallest linear diameter to which a laser or other beam of radiant energy is capable of being focused, depending on the...
static beam shaping
A technique for creating optimal performance in a system by producing a specific beam irradiance distribution, usually...
scintillation
1. The variation in intensity of a light beam as it travels through the atmosphere. 2. In radiation physics, a light flash...
radiance
Radiant power per unit source area per unit solid angle. Usually it is expressed in watts/m2/steradian.
reflectance estimate
The output of spectral channels written as an integral function of known solar irradiance, atmospheric transmittance and...
near-field scanning
A measurement technique used to determine the spatial distribution profile of an electrical or optical quantity of interest...
etendue
A product of the area of a light beam (normal to its direction of propagation) and the solid angle that the beam includes;...
blackbody source
A blackbody source, often simply referred to as a blackbody, is a theoretical or practical physical object that absorbs all...
irradiance
Radiant flux incident per unit area of a surface. Also called radiant flux density.
pulsed radiance
The integral of the radiance over exposure time.
conical scan sensor
A device used to determine the location and attitude with respect to the Earth of orbiting spacecraft by detecting the...
conservation of radiance
The principle that states that optical instrumentation cannot increase the radiance of a source; the radiance of an image...
superradiance
Directional and coherent radiation pulses that result from an ensemble of coherently prepared states in an optical medium.
time-averaged holographic interferometry
Multiple exposures of holograms, one for each position of a vibrating image, that are used for vibration analysis and that...
mode field diameter
For a single-mode fiber, the measurement of the irradiance distribution at the fiber's end face.
emissivity
The ratio of an object's radiance to that emitted by a blackbody radiator at the same temperature and at the same wavelength.
photographic exposure
The product of exposure time and irradiance or illuminance.
Lambert's cosine law
Flux per unit solid angle leaving a surface in any direction is proportional to the cosine of the angle between that...
reciprocity law
With respect to photography, the law stating that the optical density of an exposed emulsion with standard development is a...
acoustical holography
The optical reconstruction of image information contained in a sound field. First the diffraction pattern, formed by an...
lambertian surface
A perfectly diffusing surface; the intensity of the light emanating in a given direction from any small surface component is...
limiting aperture
The maximum circular area over which radiance and radiant exposure can be averaged.
spectral irradiance
Irradiance per unit wavelength interval at a given wavelength, expressed in watts per unit area per unit wavelength interval.
integrated radiance
spectral radiance
Radiance per unit wavelength interval at a given wavelength, expressed in watts per steradian per unit area per wavelength...
noise equivalent irradiance
The amount of spatial noise detected equivalent to the output emission location of the giving source.
radiance factor
Ratio of the radiance of the specimen to that of a perfect reflecting or transmitting diffuser identically irradiated.
solar simulator
A solar simulator is a device used to replicate the spectrum and intensity of sunlight in a controlled environment for...
bidirectional reflectance distribution function
Unified notation for specification of reflectance in terms of both incident- and reflected-beam geometry; i.e., the ratio of...
inverse square law
The law stating that the illuminance (or irradiance) from a point source varies as the inverse square of the distance...
nonlinear scattering
Direct conversion of a photon from one wavelength to a lower energy photon of another wavelength(s) due to inelastic...
shading
1. The sorting of lenses by their color. 2. In an optical system, an irradiance or brightness gradient in the image that is...
Johnson's curve
The graph of a curve describing the spectral irradiance of extraterrestrial sunlight.
beam divergence
Increase in the diameter of an initially collimated beam, as measured in milliradians (mrad) at specified points; i.e.,...

(35 results found)

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