Photonics Dictionary: R

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...

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,...

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

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.

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 resonator is a device or system that exhibits resonance, which is a phenomenon that occurs when an external force or stimulus is applied at a specific frequency, causing the system to oscillate...

Two lenses, separated by a distance equal to the sum of their focal lengths, and retroreflecting mirror assemblies, one of which is coaxial with the lenses and the other slightly translated off-axis.

A retroreflector is an optical device or structure that reflects incident light or electromagnetic waves back to their source, regardless of the direction from which the light approaches. Unlike...

A laser using a dye solution as the active medium whose resonator is formed into a ring (or a triangle or another shape) by means of multiple mirrors.

A test method for determining high-reflectivity levels by monitoring cavity decay within a resonant cavity formed by two mirrors under test.

A transparent plate ruled with black lines and equal, clear spaces. It is used as a multiple knife-edge for testing a concave mirror.

More efficient than the Foucault knife-edge test, this test examines curved mirrors by using a transmission grating with 40 to 200 lines per inch in place of the knife-edge, and a section or slit of...

A corrective lens system that is placed near the focal plane of a Newtonian telescope to increase its effective field of view by correcting for coma formed by the telescope's paraboloidal mirror.

Developed for use in military reconnaissance systems, it consists of a polygonal mirror, drive motor, interface between motor and mirror, and control electronics. Also used in broadband video...