Photonics Dictionary

Electromagnetic energy is transmitted in the form of a sinusoidal wave. The wavelength is the physical distance covered by one cycle of this wave; it is inversely proportional to frequency.

The law stating that the just-perceptible increment of stimulus is a constant fraction of the stimulus.

A photometer that uses a wedge, marked to show its reduction of flux density, to make two light sources equal in intensity for comparison of luminous intensities. This is accomplished by the gradual...

A diffraction pattern sampling unit composed of a 32-element monolithic silicon photodiode array and a readout unit. The intensity on each detector element can be separately read out by means of a...

An optical element having plane-inclined surfaces. Usually the faces are inclined toward one another at very small angles. Wedges divert light toward their thicker portions, and may be circular,...

A statistical means of characterizing the failure of a fiber or device as related to strain or time. Results are plotted on a special graph paper to yield the distribution shape parameter.

The Weissenberg method, named after the German physicist Karl Weissenberg, is a technique used in x-ray crystallography for obtaining high-quality diffraction patterns from single crystals. This...

A well plate, also known as a microplate or microtiter plate, is a flat plate with multiple small wells or depressions arranged in a grid pattern. Each well serves as a separate container for holding...

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...

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...

The state of a carrier signal that corresponds to maximum picture brightness in a television system.

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.

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...

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 (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...

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.

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 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...

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:...

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,...

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.

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...

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.

Specified curved optic intended for maximum collection of light, including off-axis rays, before leaving the exit aperture.

In micropositioning systems, motion (most frequently undesired) about the Z-axis.

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...

A grazing incidence mirror telescope with concentric conic surfaces having a single common point: a paraboloid-hyperboloid combination with two internal reflections.

The phenomenon in which alkali metals are transparent to ultraviolet radiation.

A Cassegrain telescope having a parabolic primary mirror, a spherical secondary mirror and a zero-power doublet in the converging bundle for aberration correction.

1. In a plane Cartesian coordinate system, the horizontal axis, or axis in the left to right direction. 2. In a quartz crystal structure, the refrence axis.

Two flat parallel electrodes that are vertically mounted alongside each other in a cathode-ray tube and produce horizontal deflection of the beam when a difference of potential is applied between...

Radiography using the emission of x-rays to form an image of the structure penetrated by the radiation.

The testing by hypothesizing a likely crystal structure, computing a test x-ray diffraction pattern and comparing this to the observed pattern to evaluate a crystal structure.

The series of processes used to identify and evaluate crystal structure by using crystalline solids to diffract x-rays. In the Laue method, radiation of a wide range of wavelengths is transmitted by...

The study of the celestial bodies, relative to x-ray emission. Satellites launched to study x-ray sources have revealed many new classes of galactic and extragalactic sources, as well as the...

An instrument that measures the wavelengths of an x-ray spectrum by the diffraction of x-rays from a crystal with a given lattice spacing.

The collection and detection of x-rays by virtue of their ionizing properties. The ionization may be perceived directly by a gas-filled ionization chamber, photographically, or by correlating...

One of various types of fluorescent screens used to detect x-ray radiation. Photographic film is mildly sensitive to x-rays, but much more sensitive to light. Hence, in photographing x-ray...

The bending of x-rays by the regular layers of molecules in a crystal acting like a very small diffraction grating. The diffraction pattern so obtained and recorded on film provides a means for...

A film or plate that is usually coated on both sides with a very fast emulsion that is sensitive to x-rays, and used to record x-ray diffraction patterns photographically.

The penetrating capacity of x-rays that is an inverse function of the wavelength.

Irradiation of a cylindrical crystal with an x-ray beam resulting in Bragg diffraction that produces a slightly enlarged image.