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Definitions: B

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barrier layer
In the fabrication of an optical fiber, a layer that can be used to create a boundary against OH-ion diffusion into the core.
baryta -> glass barium
A type of glass containing barium oxide, which is added to increase the refractive index while maintaining a relatively low dispersion.
basal plane
A plane in a crystal that lies parallel to the principal plane of symmetry.
base-altitude ratio
In aerial photography, the ratio derived from a stereoscopic pair of photographs that represents the air-base length divided by the flight altitude.
baseband
The simplest method of transmission on a local area network. The entire bandwidth of the cable is used to transmit a single unmodulated digital signal. Baseband transmission is capable of...
baseband response function -> transfer function
The complex function, H(f), equal to the ratio of the output to input of the device as a function of frequency. The amplitude and phase responses are, respectively, the magnitude of H(f) and the...
baselength
The distance between pupil centers in a two-pupil system, measured perpendicularly to the optic axis.
baseline
The smallest amount of photon energy to pass a detector window and be counted.
basic roughness
The roughness profile shape from which light scattering is expected to occur.
bathymetric lidar
Bathymetric lidar is a remote sensing technique used to measure the depth of water bodies and map underwater terrain features. It employs lidar (Light Detection and Ranging) technology, which uses...
bathymetric map
A surveying map representing measurement of depth, particularly that of the ocean.
baud
A unit of speed of transmission or receipt of a signal, roughly equal to bits per second; common baud rates are 300, 1200, 2400, 4800 and 9600.
Baume scale
The scale for floating hydrometers used to measure the specific gravity of a polishing suspension. The depth of immersion is a linear function of the inverse of the density. The Baume scale is linear...
bay
In optical character recognition, a feature at the boundary of a character.
bayonet coupling
A coupling mechanism designed to quickly lock a connector into an adaptor or a lens into a lens mount. Typically coupling is accomplished by less than a quarter turn of the component being mounted.
BCS theory
Bardeen-Cooper-Schrieffer theory of superconductivity, based on the notion that electrons with opposite momentum and spin are paired as a result of forces arising from lattice vibrations. The theory...
beacon
A device, either visual or electronic, that emits signals to identify set positions for use in the navigation of aircraft and ships along flight paths and channels, or as a warning against entering a...
beaconage
A system of beacons used in navigation.
beam
1. A bundle of light rays that may be parallel, converging or diverging. 2. A concentrated, unidirectional stream of particles. 3. A concentrated, unidirectional flow of electromagnetic waves.
beam attenuator
A device designed to decrease flux density or power per unit area of a light beam through absorption and scattering of the beam.
beam bender
A mirror used to manipulate the beam in a laser system.
beam candlepower
With relation to the equivalent beam candlepower of a searchlight, the candlepower of a bare source that would produce the same illumination at the respective point if located the same distance away.
beam converter
A device used to alter the shape of or energy distribution within a beam of radiation.
beam deflection tube
An electron-beam tube in which the current to an output electrode is regulated by the transverse motion of the tube's electron beam.
beam diameter
1. Calculated distance between two exactly opposed points on a beam at a chosen fraction of peak power (typically 1/e2). 2. The diameter of a circular aperture that will pass a specified percentage...
beam divergence
Increase in the diameter of an initially collimated beam, as measured in milliradians (mrad) at specified points; i.e., where irradiance is a given fraction (often 1/e2) of peak irradiance.
beam divider -> beamsplitter
A beamsplitter is an optical device used to divide a beam of light into two or more separate beams, typically by reflecting a portion of the incident light while transmitting the remainder....
beam expander
A system of optical components designed to increase the diameter of a radiation beam. Usually an afocal system.
beam matrix
1. A geometrical arrangement of two or more light beams for use in laser shows, object detection or other applications requiring arrayed multiple beams. 2. A mathematical 2 X 2 or 3 X 3 matrix for...
beam noise -> noise current
Any noise or current fluctuation that prevents precise measurement of the signal current. Both dark current and signal current have random fluctuations that affect the arrival of pulses. Thermal...
beam optics -> Gaussian beam optics
The area of optics that deals with the propagation of Gaussian laser beams in free space, or any general medium - i.e. lenses- under the paraxial (small divergence angle) approximations. Gaussian...
beam position
In computer graphics, the point on the display screen where the electron beam is located before the display instruction is executed. On directed beam display points, vectors and other graphic...
beam positioner
A device (e.g., prisms, lenses, tubes) used to align a beam in a system.
beam profiler
A device that measures the spatial distribution of energy perpendicular to the propagation path of a radiant beam. An energy or power meter is typically used to monitor the amount of light passing...
beam profiling
Beam profiling is a technique used to characterize and analyze the spatial intensity distribution of a laser beam. It involves measuring and visualizing how the optical power or intensity is...
beam shaper
A beam shaper is an optical device or system designed to modify the spatial profile or intensity distribution of a laser or light beam. The goal is to transform the incoming beam into a desired shape...
beam shuttle
A set of mirrors mounted on solenoids to move them into and out of the path of a laser beam, making it possible for multiple workstations to alternate using the single laser source.
beam spread -> divergence
1. In optics, the bending of rays away from each other. 2. In lasers, the spreading of a laser beam with increased distance from the exit aperture. Also called beam spread. 3. In a binocular...
beam table
Laser light show effects equipment including optics and mechanical devices that reflect, position or distort the laser beam, but not including the laser itself.
beam waist
That point in a Gaussian beam where the wavefront has a curvature of zero and the beam diameter is a minimum.
beam-addressable technology
The application of reversible writing with a laser beam on particular storage materials. In one method, an amorphous film is heated and then crystallized for writing. Bubble writing involves the...
beamsplitter
A beamsplitter is an optical device used to divide a beam of light into two or more separate beams, typically by reflecting a portion of the incident light while transmitting the remainder....
beamsplitting block
A glass block that produces stationary fringes in the region crossed by incident light beams.
beamwidth
The angular width of a radiation beam. With respect to a conical beam of light, it is the vertex angle of the cone. The beamwidth is a measure of the rate of divergence or convergence of a light...
beat
The signal formed when two signals, such as light waves, of different frequencies are present simultaneously in a nonlinear device. The frequency of the beat is equal to the difference in frequency...
beat length
A characteristic of optical fiber used to calculate the fiber's ability to maintain polarization. The beat length describes the length required for the polarization to rotate 360 degrees. For a given...
beauty defect
A defect on or in an optical element that does not appreciably impair the function of the surface.
Becke apertometer
Device used to measure the numerical aperture of a microscope, composed of a 14-mm-thick glass block with numerical aperture gradations carved onto its lower surface.
Becke line
A band of light that appears along the outer edge of a transparent material under microscopic investigation and that moves toward higher refractive indices as the microscope's focus is raised, and...
becquerel
Activity of a radionuclide having one spontaneous nuclear transition per second.

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