Photonics Dictionary: R

In chemistry, a device in which a chemical reaction takes place. In electronics, a device that introduces reactance into a circuit.

The transparent component of an optical reader that transmits the image rays of the characters to be read.

A reagent is a substance or compound that is used in a chemical reaction to bring about a specific transformation or to detect the presence or absence of another substance. Reagents are employed in...

Also known as display primaries. Colors formed by a television receiver that are of constant chromaticity and variable luminance, and that, mixed in certain proportions, form other colors. Red, green...

The fundamental wavelength standard of time or frequency. An atomic standard, it is properly expressed as 9,192,631,770 times the frequency of the transition between the hyperfine structure levels of...

Recombinase polymerase amplification (RPA) is a molecular biology technique used to rapidly amplify specific DNA or RNA sequences under isothermal conditions, meaning it does not require the...

The radiation emitted in semiconductors when electrons in the conduction band recombine with holes in the valence band. If population inversion occurs between portions of the valence and conduction...

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

A type of camera that incorporates a tiny mirror that oscillates in accordance with incoming signals. An illuminated slit is imaged by this tiny mirror on a moving ribbon of sensitized paper or film,...

RGB stands for red, green, blue, which are the primary colors of light used in additive color mixing. The RGB color model is widely used in various electronic displays, such as computer monitors,...

The displacement of spectrum lines, as determined by the increasing distance between, and the relative velocity of, the observer and a light source, causing the lines to move toward the red portion...

In holography, the beam of light that is directed from the beamsplitter to the recording medium, where it interferes with the object beam to generate the hologram.

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

Reflectance confocal microscopy (RCM) is a non-invasive imaging technique that allows for high-resolution, in vivo imaging of biological tissues at the cellular level. It is particularly useful in...

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.

Ratio of the directionally reflected flux to that reflected in the same direction by a perfect reflecting diffuser identically irradiated or illuminated.

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 microscope that uses a reflecting objective; often used with ultraviolet or infrared radiation.

An image-forming system that uses mirrors rather than lenses. Such objectives are frequently used for astronomical telescopes and in ultraviolet microscopes.

A prism having several plane polished surfaces, some to transmit light, some to reflect light, and some to serve both functions in succession. It acts generally as a group of plane mirrors held in a...

A solar spectrograph that uses long focus concave mirrors as its collimator and camera element.

Return of radiation by a surface, without change in wavelength. The reflection may be specular, from a smooth surface; diffuse, from a rough surface or from within the specimen; or mixed, a...

A reflection grating is an optical component that consists of a series of closely spaced, parallel reflecting surfaces or grooves. These grooves are typically ruled or etched onto a flat substrate or...

A hologram that is illuminated by a source from the viewer's side.

A means of high resolution study through the application of soft and hard x-rays onto a sample surface in order to obtain image information from 1-10 nm layers and surfaces. The x-ray source emission...

Reflectance spectroscopy is a technique used to analyze the reflective properties of materials across various wavelengths of the electromagnetic spectrum. By measuring the reflectance of light from a...

The term reflective is an adjective that describes the ability of a surface or material to reflect light or other forms of radiation. It implies the capability of bouncing back or redirecting...

A closely spaced series of well-known chemicals having a refractive index lying between 1.33 for water and 1.95 for a solution of phosphorus in carbon disulfide. They are used to identify powdered...

The method used to determine the refractive index of a given substance.

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

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

A figure of merit corresponding to the amount of light seen by a viewer through binoculars. A higher number indicates a brighter image in low-light situations. The relative brightness value is...

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

The steady state of temperature exhibited by a material that has absorbed and emitted radiation equally.

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

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...

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 degree to which a predetermined or previous setting of a positioning device can be duplicated by observance of the optical phenomena.

A pulsed laser that emits a recurring pulsed output. Frequency of the pulses emitted is known as pulsed recurrence frequency (PRF). When the PRF or duty cycle is very high, repetitively pulsed lasers...

1. In optics, the ability of a lens system to reproduce the points, lines and surfaces in an object as separate entities in the image. 2. The minimum adjustment increment effectively achievable by a...