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8,236 terms
Photonics Dictionary
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vertical imbalance
The difference in base up or down prism power at corresponding points located on the two lenses of a pair of spectacles.
vertical incident illumination
With respect to microscopy, light that is directed down through the objective onto the specimen and then returned by reflection.
vertical leveling mirror
A two-sided mirror suspended by a pendulum mechanism. An autocollimator set normal to such a mirror surface will, by definition, have its optical axis set horizontal.
vertical resolution
In television system specifications, the number of parallel horizontal black and white lines of equal thickness, that can be resolved from top to bottom of the raster. (One line equals either a black...
vertical retrace
With respect to television, the returning direction of the electron beam during the vertical blanking period.
vertical transmitted illumination
With respect to microscopy, light that is directed through the specimen by a substage condenser.
vertical-cavity laser diode
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vertical-cavity surface-emitting laser
A vertical-cavity surface-emitting laser (VCSEL) is a type of semiconductor laser diode that emits light vertically from the surface of a semiconductor wafer. VCSELs are commonly used in various...
vertical-cavity surface-emitting laser
A vertical-cavity surface-emitting laser (VCSEL) is a type of semiconductor laser diode that emits light vertically from the surface of a semiconductor wafer. VCSELs are commonly used in various...
vertical-deflection electrodes
Two electrodes that shift the electron beam vertically on a cathode-ray tube screen using electrostatic deflection.
vertometer
A device that measures the back focal length or vertex power of a lens.
very high frequency
The frequency band from 30 to 300 MHz. The corresponding wavelengths are from 1 to 10 m. (VHF).
very long baseline interferometry
Consists of a pair of radio telescopes concentrated on a single celestial object. This technique creates a single radio telescope with a diameter equal to the distance between the pair, which allows...
very low frequency
The frequency band from 3 to 30 kHz. The corresponding wavelengths are from 10 to 100 km. (VLF).
vesicular image
An image with variations in density due to the differential scattering ability of microscopic bubbles in a transparent layer.
VF
voice frequency
VGA
video graphics array
via
In integrated circuits, a pathway, hole, or other passage through the substrate.
vibrational circular dichroism
Vibrational circular dichroism (VCD) is a spectroscopic technique used to probe the chiral properties of molecules. It measures differences in the absorption of left- and right-circularly polarized...
vibrational spectroscopy
Vibrational spectroscopy is a type of spectroscopy that involves the study of the vibrational states of molecules. It is used to obtain information about the molecular structure, bonding, and...
vibrational transition
A vibrational transition refers to a change in the vibrational energy of a molecule. Molecules consist of atoms that are connected by chemical bonds, and these atoms are not stationary but are in...
vibronic transition
A type of change in the energy levels of molecules in a laser that results in lasing action. Vibronic transitions are those between one electronic level and another.
Vickers microhardness test
A test similar to the Knoop hardness test, but used for fractured material. The indenter is a square-based pyramid-shaped diamond.
video
Referring to the bandwidth and spectrum location of the signal produced by television or radar scanning.
video amplifier
A wideband amplifier used to process video or picture information.
video detector
A device, such as a thermionic or crystal diode, that is introduced into the vision channel of a television receiver to select the signal from the intermediate-frequency carrier.
video graphics array
The video graphics array (VGA) is a display resolution standard introduced by IBM in 1987 for displaying graphics on computer monitors. It quickly became the de facto standard for personal computers...
video measuring gauge
A device that calibrates the size, position or distance of objects imaged on a video screen.
video scan converter
A device that changes the number of lines per frame of a video image to adapt to a lower resolution format, either by deleting lines, compressing lines or by imaging only a part of the original...
video subtractor
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image comparison
A method used in imaging to detect subtle differences between two apparently similar pictures. It can be achieved by superimposing the negative of one photograph over a contact print of another, by...
video-intensified microscopy
The observation of specimens by a microscope linked to a television camera and an image processor.
videodisc
A disc whose surface contains recorded digital data at high-packing densities arranged in concentric rings. The data, representing video frames, are both recorded and read by a laser beam.
videography
Videography refers to the process of capturing moving images and recording them in a digital format. It involves the use of video cameras, lighting equipment, and audio recording devices to create...
vidicon
A small television tube originally developed for closed-circuit television. It is about 1 inch in diameter and 5 inches long. Its controls are relatively simple and can be operated by unskilled...
view camera
A camera that permits adjustments in the perspective of an image; this is accomplished by the camera design, which permits tilt, swing, rise or fall of the image transmitted. Also known as a...
viewfinder
A device, optical or electronic, that may be joined to a camera so that the operator may perceive the scene as the camera does.
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
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.
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.
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