Photonics Dictionary: R

Rabi oscillations are a fundamental phenomenon in quantum mechanics that describe the periodic and reversible exchange of energy between two quantum states when subjected to an oscillating external...

The radiant energy emitted within a time period per unit solid angle, usually measured in watts per steradian.

A double meniscus system in which two achromatized meniscus lenses are arranged symmetrically on either side of the aperture stop, reducing or eliminating distortion, coma and lateral color.

An image that appears when a hologram is illuminated by a suitable light source, generally a laser beam.

Holographic quantity expressed as the ratio of the reconstructed first-order image to that of the incident reconstructing beam.

The coherent wave used to play back a recorded hologram. It is identical to the reference wave used in the generation of the original hologram; part of it is diffracted by the recording medium and...

The part of incident flux that is transmitted with no scattering.

A plot showing how the response (ability to detect a signal) varies with wavelength. D(l).

The inherent laser amplitude noise relative to the average optical power produced by the laser; the RIN decreases rapidly as current is increased.

A form of lens assembly used in a projection system to maximize efficiency and assure uniform illumination of the object being projected.

A lens or lens system used to transfer a real image from one point within an optical system to another, with or without magnifying it.

Remote inspection refers to the process of inspecting, evaluating, or monitoring assets, equipment, infrastructure, or systems from a distance, typically using remote sensing technologies and...

Remote sensing is a method of data collection and observation where information about objects, areas, or phenomena on Earth's surface is gathered from a distance, typically using sensors onboard...

The number of electrons emitted per photon incident upon a photodetector.

The gain that occurs between light intensity incident on a CCD given by the photocurrent produced.

Also known as reversed telephoto lens. A lens consisting of an ordinary objective with a negative component near its front focal point. Thus, the back focus is large, relative to its focal length....

A sequential scanning device, utilizing a revolving lens, in which the cathode-ray tube image is transformed into a circle of fibers. The rotating lens focuses each fiber successively on a multiplier...

A toric lens generated by rotating a specific cross section about an axis beyond its area and used in the formation of annular images.

A corrective lens system that is placed near the focal plane of a Newtonian telescope to increase its effective field of view by correcting for coma formed by the telescope's paraboloidal mirror.

One of the types of change in the energy levels of molecules or atoms in a laser that can result in lasing action. Because the energy levels between rotational states are small, such lasing action is...

Inactive optically, but having the capacity for resolution into forms of opposed optical activity. The term is derived from racemic acid, an optically inactive, tartaric acid.

A unit of energy absorbed from ionizing radiation, equal to 100 ergs per gram of irradiated material.

The spontaneous visual presentation of radar information by electronic traces on a cathode-ray tube.

The analysis of the photographs taken from the radar display of a survey aircraft and used when recording terrain that is obscured by clouds.

An acronym for radioactive detection, identification and computation. The term refers to the detection and measurement of the intensity of emitted nuclear radiation.

The astigmatism in a lens system that results when light enters the system at an oblique angle.

An alteration in magnification from the center of the field to any point in the field, measured in a radial direction from the center of the field. Some radial distortion is inherent in most optical...

A statistical analysis of facts obtained when the intensity of x-ray diffraction is calculated at different angles. In this way, the interatomic distances of gases and liquids can be deduced, with...

In gradient index optics, a gradient profile in which the index varies in a direction perpendicular to the optical axis. Radial gradient lenses can focus light even when the lens surfaces are flat,...

A grating in which the wires or rods are set radially within a circular structure.

The deviation from the ideal case where a circular variable filter is located at a given wavelength along a radial line (or constant angle of rotation) regardless of the distance from the center of...

The velocity from object to observer, directed along the line of sight.

A reflecting optic whose reflectivity is a function of the radial distance from the optic axis; can be used to convert a Gaussian beam to one of uniform cross section.

The unit angle, within an arc of a circle, equal to the radius of the circle (180/p°, numerically).

Radiant power per unit source area per unit solid angle. Usually it is expressed in watts/m2/steradian.

Ratio of the radiance of the specimen to that of a perfect reflecting or transmitting diffuser identically irradiated.

Pertaining to electromagnetic radiation, with the contributions at all wavelengths of interest weighted equally.

The ratio of the radiant flux emitted by a source to the power supplied.

Radiant power emitted into a full sphere (4p steradians) by a unit area of a source; expressed in watts per square meter.

The energy passed on as electromagnetic radiation; e.g., radio, heat or light waves.

The radiant flux per unit area emitted from a surface.