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PI Physik Instrumente - 50 ways hexapod LB 5/24
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Photonics Dictionary

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triple aplanat
A compound lens consisting of two negative lenses of flint glass. A double-convex lens of crown glass is cemented between the two negative lenses. With this system, it is possible to decrease...
triplet
A lens assembly made up of three lens elements that may or may not be cemented.
tristimulus integration
Computation of tristimulus values by integrating or summing, over the visible wavelength region, the product of the relative spectral power of a CIE standard source, the reflectance of the object...
tunable laser
Any form of laser; e.g., a dye laser, having an output that can be adjusted over a wide range of wavelengths. Normally the range is about 70 nm wide.
tungsten diselenide
Tungsten diselenide (WSe2) is a member of the transition metal dichalcogenides (TMDs) family, composed of tungsten (W) and selenium (Se). Similar to other TMDs, tungsten diselenide possesses a...
turbulence propagation medium
Simulation of atmospheric turbulence for laboratory experimentation purposes, achieved by creating an unstable vertical gradient temperature in a tank filled with water.
turret
A rotating plate containing two or more lenses to provide a rapid interchange.
two-six
Referring to compound semiconductor materials combining one element with two valence electrons and one or more with six. Examples include beryllium oxide and zinc selenide. (II-VI).
Twyman-Green interferometer
A testing device that provides a contour map of the emergent wavefront for the observer in terms of the given wavelength of the light.
Twyman-Green interferometry
Twyman-Green interferometry is a technique used in optics to measure the flatness or surface profile of optical components with high precision. It is based on the principles of interference of light...
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...
ultrahigh frequency
The frequency band from 300 to 3000 MHz. The corresponding wavelengths are from 10 to 100 cm.
ultrasonic
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-C
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 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 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 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.
ultraviolet
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...
uncut
A term describing lenses with both surfaces finished but not yet cut to any form.
unit plane -> principal plane
In a lens or lens system, that surface at which the projections of an entering and exiting ray intersect. Also known as the equivalent refracting surface, the principal plane is most often not...
universal wavelength function
One of the four functions that allows the computation of a transparent medium's index of refraction, provided the index has been identified for four standard wavelengths.
unmanned aerial vehicle
An unmanned aerial vehicle (UAV), commonly known as a drone, is an aircraft without a human pilot onboard. UAVs are remotely controlled or autonomously operated, and they can be used for various...
v-coat
A multilayer antireflective thin-film coating, so called because its reflectance rises steeply at wavelengths above and below a narrow band at zero. The v-coat is particularly useful in high-power...
V-number -> normalized frequency
Also referred to as the V number in fiber optics; the normalized frequency is a dimensionless quantity, denoted by the symbol V, given by: where a is waveguide core radius, l is wavelength in vacuum,...
V-value -> Abbe constant
A dispersion relation defined in order to value the reciprocal amount of dispersion. It is defined as the refractivity over the difference in index values of the shortest and longest visible...
vacuum
In optics, the term vacuum typically refers to a space devoid of matter, including air and other gases. However, in practical terms, achieving a perfect vacuum, where there is absolutely no matter...
vacuum apparatus
Equipment dependent on the effects of a vacuum. The principal applications in optics are in the coating of lenses and substrates and the fabrication of multilayer interference filters.
vacuum spectrography
The technique of producing spectrograms in wavelengths beyond 120 nm by the use of a diffraction grating and a Schumann plate in a vacuum environment.
vacuum ultraviolet radiation
Radiation whose spectrum runs between 100 and 300 nm. Any work with these wavelengths requires evacuated equipment.
vacuum ultraviolet source
Any source that emits radiation of wavelengths between 100 and 300 nm. Instruments used to study these sources must be evacuated, as vacuum ultraviolet does not travel freely in air.
vacuum ultraviolet spectroscopy
A method of spectral analysis using wavelengths between 100 and 300 nm that utilizes both emission and absorption techniques.
valence band
In a crystalline substance, the spectral range of states of energy that contains the crystal's binding valence electrons.
valence crystal
A crystal that is held together by covalent bonds.
Van der Waals
Van der Waals forces refer to the attractive or repulsive forces between molecules (or parts of molecules) that arise from fluctuations in electron distribution. These forces are relatively weak...
variable-focus condenser
An Abbe condenser in which the upper lens element is fixed. The lower lens may focus the illumination between the elements so that it emerges from the fixed lens as a large-diameter parallel bundle....
vertex power
The reciprocal of the back focal distance of a spectacle lens.
vertical imbalance
The difference in base up or down prism power at corresponding points located on the two lenses of a pair of spectacles.
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 low frequency
The frequency band from 3 to 30 kHz. The corresponding wavelengths are from 10 to 100 km. (VLF).
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...
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.
vitreous humor
The transparent fluid that fills the portion of the eye between the eye lens and the retina (the posterior chamber).
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...
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...
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...

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