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Photonics Dictionary: V

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viewing filter
A filter, pale purple in color, used in black and white photography to display the brightness values of a subject being recorded on film.
vignetting
In an optical system, the gradual reduction of image illuminance as the off-axis angle increases, resulting from limitations of the clear apertures of elements within the system.
VIM
video-intensified microscopy
VIP
virtual image processing
VIR
vertical interval reference
virtual base
The product of the actual base or baseline of a rangefinder or heightfinder, and the power or magnification of the instrument.
virtual histology
Virtual histology refers to the use of digital technology and computational methods to simulate or recreate histological images and structures without the need for traditional physical slides and...
virtual image
An image that is formed when rays emerging from an optical system are diverging from the optical axis. The virtual image is formed where the bundle of diverging rays appear to intersect each other...
virtual reality
Virtual reality (VR) is a computer-generated simulation of a three-dimensional environment or experience that can be interacted with and explored by an individual using electronic devices, such as a...
virtual retinal display
The use of miniature scanners to project raster-scanned video images directly onto the surface of the human retina, eliminating the need for a projection surface.
VIS
visible
VISDTA
video imaging system for detection, tracking and assessment
visibility
The maximum distance at which the eye can perceive and evaluate objects.
visibility meter
1. An instrument used to determine the visual range in an environment. 2. A type of photometer that artificially reduces an object's visibility to threshold limits and records the quantity of...
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.
visioceilometer
An instrument that uses an erbium:glass laser to determine cloud height from the ground.
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
Having the characteristics of glass.
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.
VLA
very large array
VLBI
very long baseline interferometry
VLD
visible laser diode
VLE
vapor levitation epitaxy
VLF
very low frequency
VLP
video long play
VLSI
very large scale integration
VM
velocity modulation
VME
virtual memory extension
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.

Photonics DictionaryV

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