Photonics Dictionary

A glass or metal measurement tool having a precisely calibrated angle between two of its faces.

An angle formed by the lines of sight of both eyes when focusing on an object. Also, the rate at which a ray approaches the optical axis.

The angle through which a beam is deflected.

The angle through which a ray of light is deviated by a refracting or reflecting surface, or a prism; the angle between an incident ray and the refracted or reflected ray.

The angle between an instrument's line of sight and a reference horizontal plane.

The angle formed between a ray of light striking a surface and the normal to that surface at the point of incidence.

The angle formed between the normal to a surface and the reflected ray. This angle lies in a common plane with the angle of incidence and is equal to it.

The angle formed between a refracted ray and the normal to the surface. This angle lies in a common plane with the angle of incidence. See also Snell's law of refraction.

A system in which a sequence of direct measurements of the target position is fed into a tracking filter that may produce refined estimates of past, present and future target positions.

The range of angle or solid angle values by which light may enter an optical system.

The angle subtended by an object, determined by the size of the object and its distance from the viewer.

1. In astronomy, the angle measured clockwise (eastward) in a horizontal plane, usually from north (true north, Y-north, grid north or magnetic north). 2. With relation to the plane-polarized light...

A parallel plate of glass in such a position that the refracted and reflected rays of incident parallel light are mutually perpendicular. In this situation the reflected light is plane polarized, and...

For light incident on a plane boundary between two regions having different refractive indices, the angle of incidence at which the reflectance is zero for light that has its electrical field vector...

The angle at which a given mode propagates down an optical fiber.

The solid angle of a detector or system pupil as seen by the source.

The least angle of incidence at which total internal reflection takes place. The angle of incidence in a denser medium, at an interface between the denser and less dense medium, at which the light is...

The angle that lies between the direction of an incident light beam and any resulting diffracted beam.

The angle between a light ray emerging from an optical system and the optical axis of that system.

That angle found between a pair of adjacent faces of a crystal.

The angle between the light input propagation vector and the optical axis of an optical fiber or fiber bundle.

The angle subtended by two points or lines that are just far enough apart to be distinguished as separate. The ability of an optical device to resolve two points or lines is called resolving power...

A diagram used to represent the trichromatic variables of the components in a three-color combination.

The smallest angle through which light is bent by an optical element or system. In a prism, the angle of deviation is a minimum if the incident and exiting rays form equal angles with the prism...

An imaging system designed to highlight small deviations in a planar reflective object such as a mirror. The system can be used to detect minute flaws or to image faint marks that are made in the...

The triangle in a chromaticity diagram joining the chromaticities of the NTSC phosphors, and containing all chromaticities which can be produced by additive mixture of their light.

The angular difference in the direction of an object as seen from two points of observation. The angle subtended at the object by the base length of a rangefinder.

1. The angle between two vectors that represent two simple periodic quantities that vary sinusoidally and that have the same frequency. 2. See phase.

Quantum entanglement is a phenomenon in quantum mechanics where two or more particles become correlated to such an extent that the state of one particle instantly influences the state of the...

Half the vertex angle of the cone of light emitted by a fiber.

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.

The angle between the initial and final paths traveled by a scattered particle or photon.

The angle at which photoelectric sensors are aligned to prevent light from being reflected back to the sensor from the object during retroreflective sensing; also, the angle a measured part is...

The investigation of microstructures by an instrument that generates a narrow, highly collimated beam of x-rays.

The angle subtended by an object at the point of observation.

A common aberration in lenses covering large fields of view; it results in images of objects near the edge of the field being compressed in the radial distortion.

A wide-angle lens is a type of camera lens that has a shorter focal length than a standard or normal lens, allowing it to capture a broader field of view. Wide-angle lenses are characterized by their...

An old name for the rotating arm moving about an axis of rotation over a divided circle used to measure angles. Now the term refers to a small stadia telescope mounted over a ruler for use in...

A reflecting prism that inverts the image. The image is reflected four times internally and emitted laterally. The prism is cut normal to the optical axis while the image is internally reflected from...

A curve expressing an optical fiber's total transmitted power as a function of its launch angle at the input.

An acousto-optic modulator (AOM) is a device that utilizes the interaction between sound waves and light waves to modulate or control the intensity, frequency, phase, or direction of laser beams. It...