Photonics Dictionary: R

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

An instrument used to recognize and identify incident radiation by the ionizing or stimulating properties of the radiation.

Any of the many devices used to detect the presence of radiation from a specific region of the electromagnetic spectrum.

Relative power distribution as a function of position or angle.

Also known as radiation thermometer. A pyrometer in which the radiant intensity from the source to be measured is used to calculate its temperature. The usual detector is a thermocouple, thermopile...

The temperature of a complete radiator that has a total radiant emittance identical to that of an unknown resource.

An instrument designed to collect naturally formed extraterrestrial electromagnetic radiation within the radio frequency range of the spectrum in amounts sufficient to be measured.

An instrument used to detect radioactive materials: alpha particles or helium nuclei; beta particles or free electrons; and gamma rays, which are x-rays of very short wavelength. They may be detected...

A device used to measure the intensity of radiant energy.

Raman scattering, also known as the Raman effect or Raman spectroscopy, is a phenomenon in which light undergoes inelastic scattering when interacting with matter, such as molecules, crystals, or...

A device that changes the frequency of light by inducing the Raman effect on a beam passing through it.

A photographic camera and processing system used to form a usable record of the subject in a short time, usually a few seconds, for immediate analysis.

The pattern of lines traced by rectilinear scanning in display systems.

In imaging technology, a device that converts raster or line-scan data to pixel form for further processing.

A display in which regeneration takes place serially at a fixed speed in a set pattern through the scan lines.

Raster scanning is a technique used in imaging and scanning systems to systematically capture and process information from a two-dimensional area or surface. It involves moving a sensor or scanning...

The vertical or horizontal distance between two addressable points on a display screen; indicates the basic resolution element of a terminal.

An electronic device that minimizes short-term drift effects and random measurement error inherent in alternate ellipsometric measurement of two signals.

A graph of the intersections of a fan of rays with the final image plane, plotted as a function of the positions of the rays in the pupil of the system.

When a lens system with a circular aperture is free of aberrations, the image of a point object will appear as a disc of finite size surrounded by concentric rings. When two points are separated such...

A device that is used to determine the index of refraction of a gas or liquid through the interference patterns formed by two beams of light, one of which has been transmitted by the sample. A single...

Rayleigh scattering is a phenomenon that occurs when light waves interact with particles or molecules that are much smaller than the wavelength of the light. It is named after the British scientist...

In an optical data storage system, denoting the optical head's ability both to record information and to detect it for playback.

That part of a magnetic or optical tape or disc drive that retrieves data from or records data on the recording media.

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

An optical system that is corrected for distortion and spherical aberration and therefore forms the image of a straight line as a straight line.

The light from a nonselective diffuse reflector due to the standard illumination of the scene to be televised.

The output of spectral channels written as an integral function of known solar irradiance, atmospheric transmittance and camera spectral responsivity, and the unknown spectral reflectance.

An instrument that spectrally analyzes the flux reflected from a material. The reflected flux may be total, diffuse or specular. Often the instrument measures the reflectance factor instead of the...

An exposure meter that indicates the amount of light reflected from the subject of interest.

The light ray leaving a reflecting surface, indicating the path of light after reflection.

A photographic method used to obtain an image of a subject by means of its reflectance of incident ultraviolet radiation. An ultraviolet source is used to irradiate the subject, while the reflected...

A galvanometer having a small mirror that is mounted on a moving element and that reflects a light beam onto a scale.

A telescope that uses a reflecting objective to focus an image of a distant object at a focal point.

An instrument for measuring reflectance.

A light ray that has had its direction altered because of its traversing an air-to-glass interface at some angle. In an optical waveguide, a ray that is refracted from the core into the cladding.

The technique for measuring the index profile of an optical fiber by scanning the entrance face with the vertex of a high numerical aperture cone and measuring the change in power of refracted...

A wave of radiation that has undergone refraction.

An instrument used to measure the refractive index of solids and liquids. Several types exist, the most common being the Abbe refractometer.

Rate at which an image on a computer screen is redrawn (usually 50 or 60 Hz) to prevent flicker caused by the decay of the visual image.

A repeater that is designed for digital transmission. Also called a regenerator.

Image processing operations performed on one area of an image.

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 device employed to identify toxic agents lingering on the ground or in the air from up to three miles away, by using laser beams to detect infrared light-absorption patterns that can be analyzed to...

A display device, such as a cathode-ray tube, that is located at some distance from the source generating the displayed information.

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...

A robotic process commonly employed by automakers that enables high-speed and flexible production throughput by using swiveling optics for precise beam positioning.