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7,300 terms
Photonics Dictionary
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visible spectrum
That region of the electromagnetic spectrum to which the retina is sensitive and by which the eye sees. It extends from about 400 to 750 nm in wavelength.
visible
That term pertaining to the spectral region that can be perceived by the eye.
vision
The processes in which luminous energy incident on the eye is perceived and evaluated.
visual acuity
The numerical definition of the ability of an observer to perceive fine detail. The average value may be taken as one minute, or 6.7 cycles/mm, at 250 mm (normal viewing distance).
visual angle
The angle subtended by an object at the point of observation.
visual axis
An imaginary line between the object, through the nodal point of the eye, and the fovea, or point of finest retinal acuity.
visual binaries
A pair of stars (double star) that can be seen separately with a telescope, generally by setting a filar micrometer for the separation and position angle. Observation of visual binaries improves with...
visual detection and ranging
Visual detection and ranging (ViDAR) is a technology that utilizes optical sensors, such as cameras or other imaging devices, to detect and track objects in the surrounding environment. Unlike...
visual fault locator
A device that enables visual tracing of a fiber optic cable to check for breaks and defects by coupling visible light into the cable. Also called fiber tracer.
visual field
The angular field of view that is seen by the eyes when fixed on a point straight ahead. The normal binocular visual field is approximately 130° in diameter.
visual photometer
A photometer that permits visual comparison of the luminance of two surfaces.
visual range
The value of the expanse of b-particles in an absorber, evaluated by visual examination of breaks in the absorption curve.
visual storage tube
An electron tube that stores and visually displays information by means of a cathode-ray-beam-scanning and charge-storage mechanism.
visual test chart
A series of high contrast block letters or similar objects arranged to permit the evaluation of eyesight in humans.
visually coupled airborne systems simulator
A visual system including a tiny television tube and imaging optics, all contained in a helmet to be worn by pilots in flight simulator training.
visually coupled display
->
helmet-mounted display
A compact optical projection system, mounted on or built into a helmet, and used to project data or a scene directly into the eyes of the wearer. Also called visually coupled display.
vitreous humor
The transparent fluid that fills the portion of the eye between the eye lens and the retina (the posterior chamber).
vitreous silica
->
fused silica
Glass consisting of almost pure silicon dioxide (SiO2). Also called vitreous silica. Frequently used in optical fibers and windows.
VLE
vapor levitation epitaxy
VLP
video long play
VMM
vector matrix multiplication
VOA
variable optical attenuator
void
A blank area (caused by insufficient inking of the paper) that falls within the range of an intended character stroke in an optical character-recognition system.
Voigt effect
The induced birefringence in isotropic gases that results when the gases are placed in strong fields.
voltage contrast analysis
A nondestructive testing method for very large scale integration circuits, using a scanning electron microscope to monitor changes in the electronic state of the chip as it is fed test voltages while...
voltage multiplier
A device that converts alternating voltage to direct voltage, while at the same time increasing its amplitude.
voltaic cell
An electric cell having two electrodes of unlike metals immersed in a solution that chemically affects one or both of them, thus producing an electromotive force.
volume Bragg gratings
Volume Bragg gratings (VBGs) are specialized optical elements that consist of periodic variations in refractive index throughout the volume of a transparent material, typically a photosensitive glass...
volumetric imaging
Volumetric imaging refers to the capture, visualization, and analysis of three-dimensional (3D) information from a volume of space. Unlike traditional two-dimensional (2D) imaging, which provides...
vortex phase plate
A vortex phase plate is an optical device designed to impart a phase singularity, commonly referred to as a vortex or phase vortex, onto a light beam. This singularity results in a phase profile...
VPE
vapor phase epitaxy
VPR
vapor phase regrowth
VPRF
variable pulse repetition frequency
VRD
virtual retinal display
VSTEP
vertical to surface transmission electrophotonic device
VTPR
vertical temperature profile radiometer
VTR
videotape recorder
w-type fibers
->
double-clad fiber
Double-clad fiber (DCF) is a specialized optical fiber that features two concentric cladding layers surrounding a core. The design of double-clad fibers allows them to be used in various...
Wadsworth mounting
A system used for gratings that consists of a concave mirror, a grating and a plate holder mounted normal to the grating to reduce astigmatism and spherical aberration. The mounting yields a...
wafer
In the context of electronics and semiconductor manufacturing, a wafer refers to a thin, flat disk or substrate made of a semiconducting material, usually crystalline silicon. Wafers serve as the...
wafer tube
An image intensifier tube in which the photocathode and the output of the microchannel plate are proximity-focused on the microchannel plate input and output phosphor screen, respectively.
Waidner-Burgess standard
A standard of luminous intensity evaluated as the luminous intensity of 1 cm2 of a blackbody at the melting point of platinum.
water glass
A solution containing colloidal silica particles.
watt
The power that gives rise to the production of energy at the rate of 1 joule per second.
wave
1. An undulation or vibration; a form of movement by which all radiant energy of the electromagnetic spectrum is estimated to travel. 2. A type of surface defect, usually due to improper polishing.
wave function
In quantum mechanics, a wave function (often denoted by the Greek letter Ψ, psi) is a mathematical description that represents the quantum state of a particle or a system of particles. It...
wave number
The frequency of a wave divided by its velocity of propagation; the reciprocal of the wavelength.
wave optics
Also referred to as physical optics - the area of optics in which the wave nature of light is essential when defining its propagation. To exploit the wave phenomena of light, one must interact light...
wave plate
An optical element having two principal axes, slow and fast, that resolve an incident polarized beam into two mutually perpendicular polarized beams. The emerging beam recombines to form a particular...
wave splitting
Any type of interference produced by a beamsplitter.
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Photonics Dictionary
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