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Photonics Dictionary: W

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WG
waveguide
Wh
watt-hour
whispering gallery mode
Whispering gallery mode (WGM) refers to a phenomenon in wave physics, particularly in optics, where waves, such as light or sound waves, are trapped and circulate along the periphery of a curved...
white balance
A feature of some imaging devices, such as digital cameras, that allows them to compensate for different lighting conditions by adjusting the color balance based on the difference between a white...
white level
The state of a carrier signal that corresponds to maximum picture brightness in a television system.
white light
Light perceived as achromatic, that is, without hue.
white noise
The random noise having a spectral density that is substantially independent of the frequency over a specified frequency range. White noise is widely used in the random vibration testing of devices.
white-light continuum
An extremely wide emission spectrum generated by the nonlinear effects created when a high peak power from a short-pulse laser is focused into a water or carbon tetrachloride cell. The resulting...
white-light hologram -> rainbow hologram
Essentially, a hologram of a hologram, in which the first-generation hologram is masked with a narrow slit. During image reconstruction, the slit operates as the exit pupil in image space. The...
white-light interferometer -> optical profiler
Also known as a white-light interferometer. Measures surface texture and shape from nanometer-scale roughness to millimeter-scale step heights. A standard arrangement includes an illumination source,...
whiteness measurement
The use of whiteness formulas to replace visual assessment.
Whittaker-Shannon theorem
The theorem stating that, when the sampling period in a recorded sample hologram is matched to the object spectrum, the resulting image does not suffer any loss of information content.
whole slide imaging
Whole slide imaging (WSI), also known as virtual slide microscopy or digital pathology, is a technology that involves the digitalization of entire glass slides containing histological or cytological...
WIC
wavelength-independent coupler
wide-angle distortion
A common aberration in lenses covering large fields of view; it results in images of objects near the edge of the field being compressed in the radial distortion.
wide-angle lens
A wide-angle lens is a type of camera lens that has a shorter focal length than a standard or normal lens, allowing it to capture a broader field of view. Wide-angle lenses are characterized by their...
wide-field eyepiece
An eyepiece or magnifier capable of covering a field of view that is greater than 50°.
wide-field fluorescence microscopy
Wide-field fluorescence microscopy uses either naturally occurring structures or staining with fluorescent tags that are activated by specific wavelengths of light and then emits a different...
Wien's displacement law
The formula that gives the wavelength of maximum spectral radiant emittance of a perfect blackbody: λmax = 2898/T(µm) The radiation at this λmax can be calculated as follows:...
Wiener experiment
After putting a thick photographic emulsion on a front-faced mirror, and exposing the emulsion to monochromatic incident light normal to the face, Wiener discovered, upon developing the emulsion,...
Wiener filtering
A method that embraces the classical approach to image restoration and attempts to minimize the mean square difference between the original ungraded signal and the restoration.
Wiener spectrum -> optical power spectrum
Also known as the Wiener spectrum or the noise power spectrum, the optical power spectrum is a fundamental quantity in film-screen image quality evaluation. It is a means of describing image content...
wiggler magnet -> 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...
Williams refractometer
A refractometer that has a greater resolving power than a standard refractometer, and that uses a pentagonal prism to split the light from a single slit into two beams.
Winchester drive
A sealed, hard, magnetic disc drive used for the storage of data in a computer system.
window
1. A piece of glass with plane parallel surfaces used to admit light into an optical system and to exclude dirt and moisture. 2. A particular region of the electromagnetic spectrum that has been...
windowing
A technique for reducing data processing requirements by electronically defining only a small portion of the image to be analyzed, all other parts of it being ignored.
Winston cone
Specified curved optic intended for maximum collection of light, including off-axis rays, before leaving the exit aperture.
WL
wavelength
wobble
In micropositioning systems, motion (most frequently undesired) about the Z-axis.
Wollaston prism
A polarizing prism consisting of two calcite prisms cemented such that they deviate the two emerging beams (which are mutually perpendicularly polarized) by nearly equal amounts in opposite...
Wolter telescope
A grazing incidence mirror telescope with concentric conic surfaces having a single common point: a paraboloid-hyperboloid combination with two internal reflections.
wood effect
The phenomenon in which alkali metals are transparent to ultraviolet radiation.
wood lens
A type of radial gradient lens that can focus light even though its surfaces are flat.
woods glass -> cobalt glass
Glass that transmits near-ultraviolet radiation but is opaque in the visible region. Also known as woods glass.
word
In digital image processing, a unit equal to 16 bits.
working aperture
The maximum aperture of a lens at which it will still give a sharp image, even though its physical aperture may be larger.
working distance
In microscopy, the clear distance between the specimen being viewed and the first optical element of the objective lens.
WORM
write once, read many
Wp
watt peak
WPD
wave particle duality
WRD
wedge ring detection
write once, read many (WORM)
An optical data storage device that permits the user to store data (write) and play it back (read), but not to erase or change the stored material.
writing rate
Term for the brightness of an oscilloscope trace.
WRR
World Radiometric Reference
WSM
wavelength selective mirror
wt
weight
Wynne-Rosin telescope
A Cassegrain telescope having a parabolic primary mirror, a spherical secondary mirror and a zero-power doublet in the converging bundle for aberration correction.

Photonics DictionaryW

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