Photonics Dictionary: R

Also known as reversed telephoto lens. A lens consisting of an ordinary objective with a negative component near its front focal point. Thus, the back focus is large, relative to its focal length....

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.

Retroreflection is a phenomenon in optics where light is reflected back toward its source, typically in a direction nearly parallel to the direction from which it originated. This occurs due to the...

Retroreflectivity refers to the property of a surface or material to reflect light back to its source, regardless of the angle of incidence. Unlike most surfaces that scatter light in various...

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 prism made of two elements cemented together that, depending on its orientation, inverts or reverts an image. It may be used in converging or diverging light. Sometimes referred to as a K prism.

An image whose left side appears to be the right side, and vice versa.

The characteristics of a material that determine its tendency to flow.

Rhodamine refers to a family of fluorescent organic dyes that are widely used in various fields, including biology, chemistry, medicine, and materials science. These dyes are known for their bright...

A reflecting prism that is rhomboidal in shape. It has two parallel transmitting faces, and two parallel reflecting faces; the latter are oblique to the former (usually but not necessarily at...

A photodiode having a conducting grid that covers the surface of the photodiode junction and intercepts and wastes some of the light. In this way, efficient optical- and microwave-frequency design...

A small erect-image telescope for use as a sighting device on a rifle. The chief requirement is a long eye relief to avoid damage to the eye due to recoil. The power may lie anywhere between 1 and...

A type of 45-90-45° prism used to bend a beam of light through a right angle with the surfaces forming the 90° angle acting as transmitting faces.

A ray of an image-forming bundle that passes through the edge of the entrance pupil or aperture stop. Usually used in connection with meridian rays, an upper rim ray is one that passes through the...

A toric lens generated by rotating a specific cross section about an axis beyond its area and used in the formation of annular images.

A flat, round micrometer that is placed in the focal plane of a telescope to measure difference in right ascension and declination.

A system of local area networking in which each node or station is connected to two others, ultimately forming a loop. Data are passed in one direction only, being received by each node and then...

A ring laser gyroscope (RLG) is a type of gyroscope that uses laser light to detect and measure changes in orientation. It operates based on the Sagnac effect, which is a fundamental principle of...

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

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

Measurement of the time elapsed during the current output change from 10 to 90 percent in a photoconductor.

A Risley prism, also known as a Risley prism pair or Risley rotating prism, is an optical device used for controlling the direction of a laser beam or other optical beam by independently rotating two...

A form of Cassegrain telescope having a concave hyperbolic primary and a convex hyperbolic secondary. This form permits the simultaneous correction of spherical aberration and coma.

Robotic arms, also known as robot arms or manipulator arms, are mechanical devices designed to mimic and perform the functions of human arms. They consist of multiple articulated segments, joints,...

Rockwell hardness (Rc) refers to a method for measuring the hardness of a material, primarily metals, using an indentation test. It is named after the Rockwell scale, which was developed by Stanley...

The study of x-rays, their biological effects and technology. Named for W.C. Roentgen, who discovered x-rays in 1895.

Conductor element for use in integrated electro-optic systems that measures current flowing through it.

Rolling shutter artifacts are distortions or visual anomalies that can occur in images or videos captured by cameras with rolling shutter sensors. A rolling shutter is a type of image sensor that...

A defect in the cleaved end face of an optical fiber in which a portion of the edge has broken away; the complement of lip.

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 statistical method of dealing with a series of values where each value is squared, the mean of these squares is calculated, and the square root of that mean is then taken.

A statistical method of dealing with a series of values where each value is squared, the sum of these squares is calculated and the square root of that sum is then taken.

A camera system used for microphotography that has a structure, such as a cylinder or surveyor belt, to rotate the documents to be recorded. The image is fixed relative to film motion and exposure is...

A structured light device using a rapidly rotating laser to project a beam of light that appears to the human eye as a continuous circle; used as a reference marker on walls or landscape for...

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...

A term used to describe a very coarse grinding process.