Photonics Dictionary: B

The intensity of the light in the scene behind an object being viewed.

The measured wavelength of the most distinct edge of a spectral band.

A spectrum that originates from molecules and that is composed of bands which, in turn, consist of many closely spaced lines. Band spectra are used to determine nuclear spin and statistics, and...

A filter that suppresses a given range of frequencies, transmitting only those above and below that band. Also called bandstop filter.

The emission of a photon by the return of an excited carrier from the conduction band to the valence band of a semiconductor along a radiative recombination path. The resulting photoluminescence...

In semiconductor physics, the term bandgap refers to the energy range in a material where no electronic states are allowed. It represents the energy difference between the valence band, which is the...

The range of frequencies that will pass through a filter or other device. Synonymous with passband.

A filter with a transmission that is high for a particular band of frequencies, but that falls to low values above and below this band.

The range of frequencies over which a particular instrument is designed to function within specified limits. See also fiber bandwidth.

In fiber optics, the limitation on performance imposed by the system bandwidth rather than the amplitude of the signal.

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...

A mirror used to manipulate the beam in a laser system.

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.

A system of optical components designed to increase the diameter of a radiation beam. Usually an afocal system.

The loss of optical power in an optical fiber because radiation escapes through its bends. The radiation loss caused by fiber bending is proportional to the bend radius.

The radius of curvature that an optical fiber can bend without breaking.

1. That action occurring when light passes through an optical interface at other than normal incidence, i.e., refraction. 2. The curving of a path of light that passes close by a massive object, due...

A small convergent lens, located between the objective and eyepiece of a microscope, that focuses an image of the upper focal plane of the objective in the focal plane of the eyepiece. It is commonly...

A data transfer function that moves a rectangular group of pixels between bit maps. Often used in displaying cursors and pop-up windows.

A ground-based navigation beacon that emits pulsed signals which are picked up by aircraft making an instrument (blind) approach in landing. The signal is transmitted to the aircraft's L-scan...

The spot on the retina where the optic nerve is attached; it is incapable of sensing light because of the absence of light receptors.

The inability to perceive visual images (visible radiant energy). In human beings, blindness is defined as a visual acuity of less than one-tenth normal vision.

A Bose-Einstein condensate (BEC) is a state of matter that forms at temperatures close to absolute zero. It is named after Satyendra Nath Bose and Albert Einstein, who independently predicted the...

In optical character recognition, an intermediate step between character location and feature extraction.

One of the constants h, k, f or I, used to demonstrate any set of parallel planes in a crystal of the hexagonal system.

A parallel plate of glass in such a position that the refracted and reflected rays of incident parallel light are mutually perpendicular. In this situation the reflected light is plane polarized, and...

Indicating a capability to deal with a relatively wide spectral bandwidth.

Broadband dielectric mirrors, also known as broadband mirrors, are optical coatings designed to efficiently reflect or transmit light over a broad range of wavelengths. These mirrors are constructed...

A broadband filter is an electronic or electromagnetic device designed to pass a range of frequencies or signals within a specified bandwidth while attenuating or rejecting signals outside of that...

A conical or cylindrical package of light rays emanating from a common point on the object.

Calculates the exponential growth of the least stable spatial frequency in a laser beam, and is the numerical equivalent of the nonlinear phase shift along the laser system's optical axis.

A cathode-ray display where information is represented visually as spots. Each spot's location is represented by a horizontal coordinate showing its bearing angle, and a vertical coordinate showing...

A device containing two opposed quartz wedges of equal angle, one wedge being movable along its length by a micrometer screw. The wedges are cut so that their fast directions are along, and...

The distance from the final optic within a system to the rear image point of the system. See focal length.

A CCD that has been reduced in thickness by etching so that light passes through the back layers of the CCD. This type of CCD typically has higher sensitivity, especially to blue light, and higher...

A photovoltaic cell designed so that light travels through the front electrode and a semiconductor before it comes to the barrier layer.

In a mechanical system, any lost motion between driving and driven elements due to clearance between parts.

The ability of a camera to compensate in cases where a subject with a large amount of background light would otherwise be obscured by blooming or silhouetting.

The forming of a clear silhouette of an object by placing a light source behind it. Used in machine vision when surface features of an object are not important.

Refers to a display or screen that is illuminated from behind; the light is transmitted as opposed to reflected.

Backscatter refers to the phenomenon in which radiation or waves are scattered backward, opposite to the direction of the incident beam. This occurs when the incident radiation encounters a target or...

Fraction of light counter propagating collinear with the incident source. Processes considering backscattering are Raman, Brillouin, Rayleigh and Mie.