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8,236 terms
Photonics Dictionary
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average power
In a pulsed laser, the pulse energy in joules times the repetition rate in hertz.
averaged threshold receiver
A receiver for optical communications systems consisting of a symmetric binary, pulse-code-modulated transmitter, a log-normal channel and an array of independent photocounting detectors that yield...
aversion response
Eye blink or head movement in response to bright light. Aversion responses such as blinking are sufficient protection from less hazardous lasers, including Class 2 lasers. An eye blink can occur, at...
averted vision
In astronomy, the method of deliberately viewing objects with peripheral vision to take advantage of the eye's greater sensitivity to faint light a few degrees from the optical center.
AVLIS
atomic vapor laser isotope separation
Avogadro's constant
The number of molecules in one gram mole of a substance, numerically approximated by 6.02 x 1023.
AVPIDS
acoustic video processor integrated display station
AVS
American Vacuum Society
AWB
automatic white balance
AWGN
additive white Gaussian noise
AXAF
advanced x-ray astrophysics facility
axial bundle
A bundle of rays that originates from an object point on the optical axis of a lens system.
axial color
A lens aberration that causes axial light rays having different wavelengths to focus at various points along the axis.
axial gradient
In gradient index optics, a gradient profile in which the refractive index varies along the direction of light propagation, or optical axis. Axial gradient lenses can be used to correct spherical...
axial gradient technology
A method of designing lasers whereby the laser rod is cut into elliptical discs and cooled by running water over the disc surfaces. The cooling circuit decreases the radial temperature gradients in...
axial paraxial ray
A paraxial light ray that extends from an object point on the optical axis.
axial propagation constant
The propagation constant evaluated along the axis of a waveguide, that is, in the direction of transmission. Also called axial propagation wave number.
axial slab interferometry
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slab interferometry
The method for measuring the index profile of an optical fiber by preparing a thin sample that has its faces perpendicular to the axis of the fiber, and measuring its index profile by interferometry.
axial vapor-phase deposition
A vapor-phase oxidation process for fabricating graded-index optical fibers. It differs from outside vapor phase deposition in that the preform is developed radially rather than longitudinally. An...
axicon
An axicon is a type of optical component characterized by its conical shape and its ability to transform a collimated Gaussian beam of light into a ring-shaped beam with a gradually increasing...
axis
A straight line, real or imaginary, passing through a body and indicating its center; a line so positioned that various portions of an object are located symmetrically in relation to the line. See...
azadioxatriangulenium
Azadioxatriangulenium is a type of organic compound with a unique triangular molecular structure. It is often abbreviated as ADOTA. This compound belongs to the class of polycyclic aromatic...
azimuth angle
1. In astronomy, the angle measured clockwise (eastward) in a horizontal plane, usually from north (true north, Y-north, grid north or magnetic north). 2. With relation to the plane-polarized light...
azimuth
->
yaw
In positioning, in-plane rotation about the vertical axis. Also known as azimuth.
azimuthal polarization
Azimuthal polarization refers to a specific polarization state of light where the electric field vector of the electromagnetic wave points along the azimuthal direction (around the propagation axis)....
azobenzene
Azobenzene is a chemical compound consisting of two phenyl rings linked by a N=N double bond. It is well-known for its ability to undergo reversible photoisomerization, meaning it can switch between...
b integral
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.
B-scope
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...
Babinet absorption rule
The rule stating that positive uniaxial crystals have greater absorption with respect to the extraordinary component of light, whereas negative crystals have greater absorption for the ordinary...
Babinet compensator
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...
Babinet principle
The principle stating that two diffraction screens, one being exactly the negative of the other, will form the same diffraction patterns.
Babinet-Jamin compensator
A Babinet compensator that contains the controlled motion of one prism with respect to the other. This idea was introduced by Jamin.
back channel
A channel for communication with the source in an otherwise unidirectional network, such as a channel that provides interactive features in a cable television network.
back focal length
The distance from the final optic within a system to the rear image point of the system. See focal length.
back-coated mirror
A glass substrate that has its rear surface coated with a reflective coating. Also known as a back-surface mirror.
back-illuminated CCD
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...
back-side illumination
Back-side illumination (BSI) is a technology used in imaging sensors, particularly in digital cameras, where the light is allowed to enter the sensor from the back side, opposite to where the...
back-surface mirror
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back-coated mirror
A glass substrate that has its rear surface coated with a reflective coating. Also known as a back-surface mirror.
back-wall photovoltaic cell
A photovoltaic cell designed so that light travels through the front electrode and a semiconductor before it comes to the barrier layer.
background luminance
The intensity of the light in the scene behind an object being viewed.
backlash
In a mechanical system, any lost motion between driving and driven elements due to clearance between parts.
backlight compensation
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.
backlighting
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.
backlit
Refers to a display or screen that is illuminated from behind; the light is transmitted as opposed to reflected.
backreflection
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narcissus
A defect in infrared systems that appears as a dark circular area on a displayed image, caused by radiation reflecting into a detector. It can be reduced by low-reflective coatings or by altering the...
backscatter
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...
backscattering coefficient,
b
Fraction of light counter propagating collinear with the incident source. Processes considering backscattering are Raman, Brillouin, Rayleigh and Mie.
backside-illuminated sensor
A backside-illuminated (BSI) sensor is an image sensor technology where the light-sensitive elements (typically pixels) are positioned on the opposite side of the sensor substrate from where light...
backstreaming
The term used in reference to vacuum systems using oil and diffusion pumps, describes the migration of pump fluids and their decomposition products into the vacuum chamber.
backward-wave oscillator
An amplifying device with a wide tuning range in which an electron gun sends a beam of electrons into a slow-wave structure. The electron beam and the electromagnetic wave move in opposite directions...
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Photonics Dictionary
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