Photonics Dictionary

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

Resonance can be defined in various contexts, including physics, chemistry, and music. Here are definitions for resonance in a few different fields: Physics: In physics, resonance refers to the...

That radiation emitted by an atom or molecule that has the same frequency as that of an incident particle; e.g., a photon. It generally involves a transition to the lowest energy level of the atom or...

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...

A reticle, also known as a reticule or graticule, is a pattern or set of markings placed in the focal plane of an optical instrument, such as a microscope, telescope, riflescope, or camera, to...

The retina is a light-sensitive tissue layer located at the back of the eye, opposite the lens. It plays a crucial role in the process of vision by converting light into neural signals that are sent...

A special-purpose camera used by ophthalmologists to photograph the retina of the eye. The optical system operates through the eye pupil, and the illuminant must be able to send light into the eye...

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...

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 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...

The formation of a block by attaching optical elements to a plate with a ring of pitch or other thermoplastic material.

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 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...

An interferometric method for describing the surface shape of large coated or uncoated optical flats. The procedure uses a commercially available small-aperture phase-shifting interferometer for...

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...

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...

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 precision positioning device used to produce rotary motion.

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...

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 camera, with a rotating prism, that is capable of forming multiple exposures on a constantly moving strip of film.

A circular optical wedge (prism of small refracting angle) mounted to be rotated in the path of light rays to divert the line of sight to a restricted degree.

One of the types of change in the energy levels of molecules or atoms in a laser that can result in lasing action. Because the energy levels between rotational states are small, such lasing action is...

A roughening laser is a laser-based surface modification technique aimed at altering the surface texture of a material to achieve specific properties such as enhanced adhesion, light diffusion, or...

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 Rugate filter is a type of optical filter that is designed to have a continuously varying refractive index profile throughout its thickness, rather than the discrete layers found in traditional...

A ruticon is an opto-electronic device in which light going through it can be modulated by an electric field. The intensity distribution of the resulting image can be precisely controlled....

The term "Rydberg atom" refers to an atom in a highly excited state where one or more of its electrons are in a Rydberg orbital. A Rydberg atom is characterized by having an electron orbit that is...

The movement of the eye as it focuses on details of a scene. Some imaging systems mimic this movement by small, rapid scanning motions of the sensor.

A crude area on the polished surface, produced during coarse grinding, that subsequent fine grinding does not remove, owing, to some extent, to coarse grains of grinding sand that mixed with finer...

Sapphire crystal refers to a transparent, single-crystal form of aluminum oxide (Al2O3) known as corundum. It is one of the hardest known materials, second only to diamond on the Mohs scale of...

Sapphire optical fiber is a type of optical fiber made from single-crystal sapphire, which is a form of aluminum oxide (Al2O3) that is highly transparent in the infrared region of the electromagnetic...