Photonics Dictionary: R

A very uncommon lamp in which a tungsten electrode is heated to incandescence by a radio-frequency electrical current.

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

The re-emission of absorbed energy, having the same wavelength as the incident energy, in an arbitrary direction from a particle because of an energy level transition within the material.

A circular lamp or bundles of optical fibers placed around the perimeter of an objective lens to illuminate the object field below it.

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

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,...

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

Half the vertex angle of the cone of light emitted by a fiber.

Essentially, a hologram of a hologram, in which the first-generation hologram is masked with a narrow slit. During image reconstruction, the slit operates as the exit pupil in image space. The...

The absorption of part of the photon energy by a molecule through which there is a slight energy change and the energy balance moves on.

A flexible fiber cable with a small diameter that transports light from the excitation laser to the target. Used in Raman spectroscopy, the probe is capable of obtaining high-quality data at high...

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.

Raman spectroscopy is a technique used in analytical chemistry and physics to study vibrational, rotational, and other low-frequency modes in a system. Named after the Indian physicist Sir C.V. Raman...

Fiber optic cable in which the arrangement of fibers within the bundle has been made random so that output light will be uniformly distributed and not relay the image of the light source at the input...

Rare earth dopants refer to elements from the lanthanide series, also known as rare earth elements, that are intentionally introduced into the crystal lattice of a material to modify its properties....

Rare-earth elements (REEs) are a group of seventeen chemical elements found in the Earth's crust, characterized by their unique properties and scarcity relative to other elements. Despite their name,...

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...

A geometric representation of a light path through an optical device; a line normal to the wavefront indicating the direction of radiant energy flow.

Ray tracing is a rendering technique used in computer graphics to simulate the way light interacts with objects in a scene. It involves tracing the path of rays of light as they travel through a...

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...

A prism system designed to produce a very high dispersion of light.

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...

A read-out integrated circuit (ROIC) is an electronic device used in imaging systems, particularly in infrared (IR) and other sensing technologies. It is designed to interface with an array of...

A reconfigurable optical add-drop multiplexer (ROADM) is a key component in wavelength-division multiplexing (WDM) optical communication networks. It allows for flexible and dynamic routing of...

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

Straight line travel. This denotes the fact that light travels in a straight line when traveling through a medium with a constant refractive index.

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...

The ratio of the first focal length of a lens to the refractive index of the medium containing the incident light; the ratio of the second focal length to the refractive index of the medium...

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

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

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 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...

The thin, transparent film made up of specific substances applied to glass-air surfaces for the purpose of decreasing the amount of reflected light.

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 lamp used in projection that is made with a reflector built into the bulb, normally by coating a portion of its interior with a reflective material to ensure the reflector's optimum position in...

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.