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uhlbricht sphere -> integrating sphere
A hollow sphere coated internally with a white diffusing material and provided with openings for incident beam, specimen and detector used for measuring the diffuse reflectance or transmittance of...
ultrafast pulsed laser
An ultrafast pulsed laser is a type of laser that emits extremely short pulses of light with durations typically on the order of femtoseconds (10-15 seconds) or picoseconds (10-12 seconds). These...
A form of microfiche that has an information reduction ratio that is greater than 100 to 1.
ultrahigh frequency
The frequency band from 300 to 3000 MHz. The corresponding wavelengths are from 10 to 100 cm.
ultrahigh-speed photography
Photographic recording of rapid events at a rate exceeding 106 frames per second.
A system used to measure very small displacement by electrical means.
The process of microphotography that involves the reduction of the original at a ratio greater than 100 to 1. The process is usually accomplished by the use of a reduced-scale negative, which, in...
A dark-field microscope used to view extremely small objects. These objects are suspended in a gas or liquid in an enclosure having a black background. A convergent pencil of bright light enters from...
ultraphotic rays
The rays (such as ultraviolet rays) lying past the visible region of the spectrum.
ultraprecision cathode-ray tube display
A highly accurate cathode-ray tube used to display information with the utmost efficient stability and resolution. The information is viewed as a series of points, particularly suited for...
ultrashort-pulse laser
A laser capable of generating light pulses that last only a few femtoseconds. This can be achieved by nonlinear filtering to increase bandwidth and compress the pulse or by passive mode-locking or...
ultrasonic camera
A device that uses a piezoelectric crystal to convert ultrasonic sound waves, transmitted through a subject, into a voltage that modulates the electron beam of a cathode-ray tube.
ultrasonic cleaning equipment
Ultrasound used in the cleaning of metal and optical parts by virtue of its vibration rates. Large acoustic forces break off particles and contaminants from surfaces.
ultrasonic cross grating
A two- or three-dimensional space grating formed when ultrasonic beams with varied paths of propagation intersect.
ultrasonic detector
A mechanical, electrical, thermal or optical detector designed to identify and measure ultrasonic radiation.
ultrasonic grating constant
The space between diffracting centers of an ultrasonic wave that is forming certain light diffraction spectra.
ultrasonic holography -> acoustical holography
The optical reconstruction of image information contained in a sound field. First the diffraction pattern, formed by an object irradiated by ultrasonic rays, interferes with a mutually coherent...
ultrasonic imaging
The formation and display of three-dimensional images by ultrasonic energy. In one technique, the energy pulses from an ultrasonic transducer scan the object through a liquid medium and, receiving...
ultrasonic light diffraction
The optical diffraction spectra formed, or the method that produces them, when a light beam is transmitted through a longitudinal sound field.
ultrasonic light modulator
An instrument with a fluid that modulates a light beam traversing it because of the effect of ultrasonic waves passing through the fluid.
ultrasonic stroboscope
A light-interference device whose excitation is determined by the modulation of a light beam by an ultrasonic field.
Ultrasonic refers to sound waves with frequencies higher than the upper audible limit of human hearing, typically above 20,000 Hz. These waves are termed ultrasonic because they are beyond the range...
ultraviolet A
The region of the electromagnetic spectrum from 320 to 400 nm.
ultraviolet absorbing filter
A filter that is opaque from 200 to 400 nm.
ultraviolet B
The region of the electromagnetic spectrum from 280 to 320 nm.
Ultraviolet-C (UV-C) refers to a specific range of ultraviolet radiation with shorter wavelengths than those of visible light. UV-C radiation spans the electromagnetic spectrum with wavelengths...
ultraviolet densitometry
A technique, involving spectrophotometry in the ultraviolet, that is designed to determine the colors of thin-layer chromatographic absorbents after elution.
ultraviolet fiber optics
Ultraviolet (UV) fiber optics refers to optical fibers that are designed and optimized for the transmission of ultraviolet light, which is electromagnetic radiation with wavelengths shorter than...
ultraviolet lamp
A type of lamp that emits a high quantity of ultraviolet radiation. This may be an arc lamp encased in a bulb of a glass that is transparent to ultraviolet rays.
ultraviolet lens
A lens intended for use with wavelengths shorter than about 380 nm. It must be made of quartz, calcium fluoride, lithium fluoride or some other material transparent to ultraviolet radiation, as glass...
ultraviolet lens
A microscope used either to detect selective absorption of various wavelengths by the specimen or to achieve increased resolution by virtue of the short wavelength of ultraviolet radiation. Electron...
ultraviolet microscopy
The study and photographing of microscope specimens in ultraviolet light; using an optical microscope containing fluorite and quartz components to efficiently image wavelengths much shorter than the...
ultraviolet molecular nitrogen laser
A pulsed laser having molecular nitrogen as laser material and a wavelength output of 337 nm in the ultraviolet region. It is essentially a channel flashtube in which a pulse is applied to the...
ultraviolet photoemission spectroscopy
A technique for measuring the energy spectrum of electrons emitted during the absorption of ultraviolet radiation. This spectrum reveals the characteristic ionization energies of the molecules and...
ultraviolet photomicrography
The photographic recording that uses ultraviolet radiation to irradiate the microscope sample being examined and to form an image of the object on a photographic medium. The components of the...
ultraviolet reflectance
Ultraviolet reflectance refers to the ability of a material or surface to reflect UV light. Ultraviolet light is electromagnetic radiation with wavelengths shorter than those of visible light,...
ultraviolet spectrometer
A spectrophotometer designed for use in the 200- to 380-nm range of the electromagnetic spectrum and equipped with a calibrated scale to determine wavelength.
That invisible region of the spectrum just beyond the violet end of the visible region. Wavelengths range from 1 to 400 nm.
ultraviolet-visible spectrometer
Also known as UV-VIS spectrometer, a device that measures the absorbance, reflectance or transmittance of light in the ultraviolet or visible wavelengths absorbed, reflected or transmitted. Commonly...
A connection, typically made up of one or more cables, between a laser head and a separate power supply. Flexible pipes or hoses are sometimes used to protect and stabilize multiple cables.
umbra -> penumbra
A source of light will not cast a distinct shadow of an interfering, opaque object, but will cast a shadow having two parts: 1. the umbra, or the central, totally dark part of the shadow; and 2. the...
The initiation of the beam in a cathode-ray tube.
The process whereby optical elements are removed from a block.
A term describing lenses with both surfaces finished but not yet cut to any form.
Illumination of hologram facets with a beam that covers only a small portion of the hologram in order to optimize laser energy use. See overillumination.
underwater photography
The field of photography concerned with the recording of subjects beneath the water with a watertight, water-resistant camera system.
underwater television system
A television system designed to obtain pictures of objects or scenes beneath the surface of the water. Generally, a low-light-level television camera and a suitable light source are enclosed in a...
undulator magnet
A device used in a free-electron laser to convert the electron-beam's energy into microwave laser radiation by creating a magnetic field of alternating polarity through which the free electrons are...
uniaxial crystal
A doubly refracting crystal having a single axis along which there is an absence of double refraction.
uniform color space
A color space in which equal distances represent equal visually perceived color differences.

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