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Photonics Dictionary: R

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reflective heat mirror -> diathermic mirror
A mirror coated to reflect cold (white) light while transmitting hot (infrared) energy.
reflective spectroscopy
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...
reflective
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...
reflectivity
The ratio of the intensity of the total radiation reflected from a surface to the total incident on that surface.
reflectometer
An instrument for measuring reflectance.
reflector
A type of conducting surface or material used to reflect radiant energy.
reflector lamp
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...
refracted near-field scattering method -> refracted ray method
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...
refracted ray
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.
refracted ray method
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...
refracted wave
A wave of radiation that has undergone refraction.
refracting prism
A prism that often is used as a dispersing element in spectrographs and monochromators.
refracting sphere
A transparent sphere that has an index of refraction that is different from that of the medium surrounding it; used in optics to demonstrate refraction and astigmatic image formation.
refraction
The bending of oblique incident rays as they pass from a medium having one refractive index into a medium with a different refractive index.
refractive index -> index of refraction
The ratio of the velocity of light in a vacuum to the velocity of light in a refractive material for a given wavelength.
refractive index contrast
A measure of the relative difference in refractive index between two optical materials. Most commonly used in fiber optics where the refractive index contrast, D, is given as follows: where n1 equals...
refractive index liquids
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...
refractive index profile
The description of the refractive index along a fiber diameter.
refractive index structure function
The mean square difference in refractive index for two separate points in space.
refractometer
An instrument used to measure the refractive index of solids and liquids. Several types exist, the most common being the Abbe refractometer.
refractometry
The method used to determine the refractive index of a given substance.
refresh rate
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.
regenerative amplifier
A type of multiple-pass amplifier in which no optical leakage is allowed until a finite number of passes has occurred; at this time the entire cavity output is released as one pulse.
regenerative repeater
A repeater that is designed for digital transmission. Also called a regenerator.
region-of-interest processing
Image processing operations performed on one area of an image.
registration shift
A shift in the apparent position of an object when an optical element is added or removed.
regular reflection -> specular reflection
Pertaining to the manner in which light is reflected, as by a mirror or speculum.
regular transmittance
The part of incident flux that is transmitted with no scattering.
relative aperture
The ratio of the diameter of the entrance pupil in an optical system to the equivalent focal length of that system. The relative aperture is denoted as a fraction in which f, the equivalent focal...
relative brightness
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...
relative detector response
A plot showing how the response (ability to detect a signal) varies with wavelength. D(l).
relative dispersion -> dispersive power
A measure of the dispersive properties of a glass. The relative dispersion is defined as: where C, D, and F refer to the material's index of refraction at the three chief Fraunhofer lines in the...
relative equilibrium
The steady state of temperature exhibited by a material that has absorbed and emitted radiation equally.
relative index
The ratio of the velocities of light in two adjacent media, neither of which is air.
relative intensity noise
The inherent laser amplitude noise relative to the average optical power produced by the laser; the RIN decreases rapidly as current is increased.
relative refractive index
The quantity equal to the refractive index of one medium divided by that of a second medium.
relay condenser
A form of lens assembly used in a projection system to maximize efficiency and assure uniform illumination of the object being projected.
relay lens
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.
relief
The discernment of depth or apparent difference in distance that causes the object to stand out from its background because of stereoscopic vision. The impression of relief can be obtained from the...
rem
The unit of the dose of any radiation that produces the same biological effect as one roentgen of x-ray.
REM
rapid eye movement
remote active spectrometer
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 display unit
A display device, such as a cathode-ray tube, that is located at some distance from the source generating the displayed information.
remote inspection
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 laser welding
A robotic process commonly employed by automakers that enables high-speed and flexible production throughput by using swiveling optics for precise beam positioning.
remote sensing
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...
repeatability
The degree to which a predetermined or previous setting of a positioning device can be duplicated by observance of the optical phenomena.
repeater -> optical repeater
In an optical fiber or waveguide communications system, an optoelectronic device or module that receives an optical signal, converts this optical signal to an electrical signal which is then...
repetitively pulsed laser
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...
replica grating
A reproduction made of an original grating -- usually by casting thermosetting plastics onto the original -- to avoid the high expense of making the original gratings.

Photonics DictionaryR

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