Photonics Dictionary: R

Plates of glass containing as many heavy metal oxides as can be dissolved in the glass without causing devitrification. The glass is yellow, very heavy and has a high refractive index. It is almost...

Also known as RAMP microscopy, random access multiphoton microscopy is a microscopic technique that uses multiple acousto-optic modulators to enable faster and addressable scanning of 3D cellular...

Essentially, noise that cannot be predicted. Therefore, even if the magnitude of sound or oscillation in a system is known at a given moment, random noise can change in a short time.

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...

1. An optical distance finder that depends on triangulation of two convergent beams on an object from disparate view points. 2. A device that depends on the measurement of time of wave travel from an...

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...

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...

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 description of the refractive index along a fiber diameter.

The mean square difference in refractive index for two separate points in space.

The ratio of the velocities of light in two adjacent media, neither of which is air.

The quantity equal to the refractive index of one medium divided by that of a second medium.

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

Loss mechanisms that degrade the performance of all thin-film optical devices by removing radiant flux out of the specular beams.

A wave that is polarized elliptically or circularly polarized and in which the electric field vector — observed while looking in the direction of propagation — rotates in a right-hand or...

The circle that contains the slit, grating and primary astigmatic focus of a concave diffraction grating.

In spectroscopy, the false images arranged symmetrically on both sides of the true line and caused by irregularities in the ruling of diffraction gratings.

The mounting of a concave diffraction grating and a plate holder at the ends of a rigid bar. The ends follow separate straight tracks that intersect perpendicular to each other. The slit is located...

A digital imaging method whereby the first gray level in the ordered sequence and the position of the first lengths of all runs are specified; used when there are only two possible gray levels...

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,...

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.

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,...

The time rate of flow of radiant energy, expressed in watts (W), and carries the units of Joule per second (J/s). The prefix often is dropped and the term "power" used.

The emission and/or propagation of energy through space or through a medium in the form of either waves or corpuscular emission.

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

The detection and measurement of nuclear and x-ray radiation.

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 film used in photographic dosimetry to record the types and amounts of ionizing radiation, such as x-rays and gamma rays, present in an area for a set interval of time. The negative produced by...

The detection and analysis of naturally formed extraterrestrial electromagnetic radiation within the radio frequency range of the spectrum.

The frequency range for radio and television transmission.

A gas laser in which the electrodes are mounted perpendicular to the optical resonator.

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

A radioactive element that is placed or injected into a system to obtain an autoradiogram of the system. It is used in a number of fields where standard methods of internal imaging, for example,...

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...

The photographic image of a thin specimen having a radioactive isotope that, formed through contact between the specimen and a photographic plate, displays the distribution of the radioactive...

A solid-state panel of the photoconductor-electroluminescent type. The photoconductive layer, sensitive to x-rays, is coated by the electroluminescent, which gives the visible image. When the former...

The study of radioactive substances and high-energy radiations such as x-rays and g-rays.

The analysis, by x-rays, of the crystalline structure and other properties of metals and alloys.

A device used to measure the intensity of radiant energy.

The luminescence displayed when particular minerals are irradiated with β-rays and g-rays, after being exposed to nuclear radiation.

A microscope to which a beamsplitter and illuminated reticle have been added that is used to measure contact lenses.