Photonics Dictionary

Also known as a gray body; a nonselective radiator is a thermal radiator that has a constant spectral emissivity with respect to wavelength throughout the spectral range being considered. The...

A radiometric device or system having uniform responsivity relative to all of the radiation parameters, or relative to one or more specified parameters, throughout all parameter intervals in which...

A color whose hue is not produced by a single wavelength in the visible spectrum, but is instead produced by mixing the longest (red) and shortest (blue) wavelengths of the spectrum such as any...

The radiation emitted from a group of charged particles that does not depend on the temperature of the source in which those particles are generated.

Sometimes referred to as the surface normal or 'surface norm'; the normal is an axis that forms right angles with a surface that light is incident upon or with other lines. The normal is used to...

Condition in which a perpendicular surface can be discovered for every ray in a group. This condition is commonly observed when rays emerge from a point source or object that is placed at the center...

Dispersion characterized by an increasing index of refraction in the medium as the frequency of the propagating light increases towards the resonant frequency of the medium. Normal dispersion occurs...

The emergence of a ray along the normal to the emergent surface of a medium.

Light striking a surface at an angle perpendicular to the surface.

Also referred to as the V number in fiber optics; the normalized frequency is a dimensionless quantity, denoted by the symbol V, given by: where a is waveguide core radius, l is wavelength in vacuum,...

Also referred to as a band-stop or band rejection filter; a notch filter is a filter that is designed to screen out a very narrow band of radiation by transmitting most wavelengths with little...

A filtering device that detects what is new in a scene of interest. Often compared to that of a temporal high pass filter, these filters will remove elements that appear repeatedly throughout an...

Equal to 10-3 lux; used in measuring low values of illumination and luminance.

The triangle in a chromaticity diagram joining the chromaticities of the NTSC phosphors, and containing all chromaticities which can be produced by additive mixture of their light.

In physics, nuclear fusion refers to the process in which two atomic nuclei come together to form a heavier nucleus, releasing a large amount of energy. This process powers the sun and other stars...

That branch of spectroscopy that applies to the study of interactions between energy and atomic nuclei. The simultaneous application of a strong magnetic field and the radiation from a...

A phenomenon, exploited for medical imaging, in which the nuclei of material placed in a strong magnetic field will absorb radio waves supplied by a transmitter at particular frequencies. The energy...

A chemical detection technique used to measure molecules that have a magnetic dipole moment. The analysis is directed to nucleuses which have a quadrupole moment which leads to an asymmetric electric...

A photographic emulsion of the silver-halide type that is used to record the path of a charged traveling particle. The tracks recorded on these emulsions are typically observed under a microscope...

A plane along which destructive interference takes place.

A lens used in the optical testing of an aspheric surface. It converts a spherical wavefront into one that precisely matches the surface under test. When the wavefront is reflected from that surface,...

Commonly performed in spectroscopy, the optical null process is a method for radiation detection whereby physical detectors are used to rapidly interchange the intensity between a reference beam and...

The sine of the vertex angle of the largest cone of meridional rays that can enter or leave an optical system or element, multiplied by the refractive index of the medium in which the vertex of the...

Expression of the nondimensional coefficient of the heat transfer in a convection process.

In image acquisition (and sampling theory), the postulate that the pickup sampling frequency must be a minimum of twice as high as the Nyquist rate of brightness change of any detail to be resolved....