Photonics Dictionary: S

A microdensitometer that contains a scanning stage to provide simultaneous representations of position vs. density.

Seidel aberrations refer to a set of monochromatic aberrations in optical systems, named after the German mathematician and physicist Ludwig von Seidel. These aberrations describe deviations from...

Transmission in different amounts as a function of wavelength, as a result of absorption and scattering, leading to color effects if occurring in the visible wavelength region.

An aperture consisting of a semitransparent central region whose amplitude transmittance only is varied, and the relative phase difference between the central and annular region is fixed as p -...

A photocathode that receives radiation from one side and emits a photoelectric current from the opposite side.

A type of compensator for use with a microscope and consisting of a quarter-wave plate in a fixed position and a rotatable analyzer.

In a radiation detector, the ratio of the output to the input signal.

The optical energy transfer between ions of differing atoms.

An instrument for determining the sensitivity of a photographic film to light. The film is given either a stepped exposure or a continuously varied exposure; after processing, the density is measured...

Primarily the measurement of photographic sensitivity of certain materials such as photographic film. It refers to the measurement of the response of photographic materials, after exposure, to forms...

1. A generic term for detector. 2. A complete optical/mechanical/electronic system that contains some form of radiation detector.

With respect to television, the transmission of the signals that originate from variously colored parts of an image in a particular sequential order.

A mode of data transmission whereby each bit is generated in sequence on a single carrier.

The Shack-Hartmann wavefront sensor is an optical device used for measuring the wavefront aberrations of an optical system. It is widely used in adaptive optics systems to correct distortions and...

The electric conductance of a conductor in which a current of 1 ampere is produced by an electric potential difference of 1 volt.

A convention that defines specific dimensions of an optical system, such as the image distance or radius of curvature of a lens or mirror, as negative or positive to facilitate calculations based on...

A computer architecture used in parallel processing whereby the processing elements are directed by a single, central control unit; generally used for large numbers of relatively simple processing...

A singlet lens is an optical lens made from a single piece of material, typically glass or plastic, with one or both surfaces being spherical or aspherical. It is the most basic type of lens used in...

A lens designed for projection of color transparencies.

A lens that exhibits spherical aberration when used at large aperture settings, and that forms an image with a slightly blurred outline.

Solar radiation intensity existing in free space at the mean solar distance of the Earth. Commonly expressed in g cal cm-2min-1, the constant is equal to the amount of incident radiation -- in unit...

An optical compensator similar to the Babinet compensator, but which produces a phase-change consistent throughout its field, as opposed to the Babinet's phase-change, which occurs progressively...

A photographic objective that uses the thick meniscus principle to obtain its power. It is designed to photograph small fields at large apertures.

Device that uses a coherent reference wave to record the interference patterns produced by incident ultrasonic waves on an object.

A beam instability, induced by index of refraction inhomogeneities and component damage of dirt and dust particles, that exhibits exponential growth and causes both system degradation and energy loss...

With respect to color photography, the measurement, at a given wavelength, of the way the color film modulates the radiant flux in the optical system containing the film.

Measure of a detector's signal during exposure to radiation of a constant power level and varying wavelength.

A sensitometer having a continuously controlled monochromator to measure spectral sensitivity and contrast of photographic materials.

A traveling microscope or an automatic microdensitometer used to measure the spectrum plate obtained in a spectrograph.

See regular transmittance; the term specular is not properly applied to transmission.

A spheric lens, also known as a spherical lens, is a type of optical lens with at least one surface that is part of a sphere. This means that the lens surface is curved in a symmetrical manner,...

A tiny lens (as small as 100 µm in diameter) used to focus light on charge-coupled devices, formed by heating a photosensitive material exposed through a mask, leaving a pattern of raised...

A close-up lens, semicircular in shape, that is mounted in front of a conventional lens focused at infinity. The result is an image made up of two sections; one focused through the split lens on near...

The interference of the two real images formed by a Billet split lens.

A lens derived from the Cooke triplet anastigmat, but with one of the crown elements split in two, resulting in improved speed and correction of aberrations.

The probability that an atom in one state will move spontaneously to a lower state within a given unit of time.

A lens whose focal length is roughly equal to the diagonal of the negative format of the camera on which it is mounted.

The observed time dependence of the transmittance of a step of radiation through a given medium.

Stochastic optical reconstruction microscopy (STORM) is a superresolution microscopy technique that enables imaging of biological specimens at resolutions beyond the diffraction limit of conventional...

In a microscope, the optical assembly that focuses light on the specimen and into the objective.

Superluminal transmission refers to the hypothetical process of transmitting information faster than the speed of light, which is commonly denoted as superluminal or faster-than-light (FTL)...

A meniscus that is often fitted before a camera lens to permit focusing on near objects.

Instruments used for measuring angles and occasionally lengths on the ground. The principal surveying instruments are the level, the stadia telescope, the transit and the theodolite. Laser...

A lens system made up of two sets of similar lenses, each of which compensates for many of the aberrations produced by the other. The lens sets are arranged symmetrically on either side of the...

A mode of transmission whereby the sending and receiving stations operate continuously at a fixed relationship of phase and frequency, generating signals to control the timing of the data that are to...