Photonics Dictionary: A

An Abbe refractometer is a scientific instrument used to measure the refractive index of liquids and solids. Named after the German physicist Ernst Abbe, this device operates on the principle of...

An abridged spectrophotometer refers to a simplified or compact version of a traditional spectrophotometer, which is a scientific instrument used to measure the intensity of light at different...

Absolute colorimetric refers to a color management rendering intent used in color profiles and conversion processes, particularly in the context of printing and digital imaging. Absolute...

The absolute luminance threshold is the lowest luminance level of a light source or illuminated object that can be detected by the human eye under specific conditions. This threshold represents the...

The value of the distance of distinct vision, minimum focusing distance or near point, divided by the focal length of the lens. Magnification is produced when the optic is placed at its focal...

Least value of color value combinations which gives white light; minimum purity as determined to be white.

The ratio of the speed of light in a vacuum divided by the speed of light in the medium.

The measurement of heat energy as determined from absolute zero as the zero point on the scale. Increments are identical to the Celsius as well as Kelvin scales.

Absolute white is a term used in color science and imaging to describe a reference white point that represents the brightest, most neutral white achievable. It serves as a standard for measuring and...

A measuring device that uses a light-sensitive cell or detector to determine the amount of light transmitted by a substance.

Measures the absorption or sample transmittance over a range of specified wavelengths. Sample may be placed within the device and the transmission measured to an accuracy of given percent. The...

An accelerometer is a sensor or transducer that measures the rate of change of velocity of an object, or in simpler terms, it measures acceleration. Accelerometers are widely used in various...

The acceptance pattern, often used in the context of antennas and optical systems, refers to the spatial distribution of the sensitivity or responsiveness of a device to incoming signals or light....

An acousto-optic tunable filter (AOTF) is a device that utilizes the acousto-optic effect to selectively filter and transmit light based on its wavelength or frequency. It operates by applying an...

An actinometer is a device used to measure the intensity of radiation, particularly solar radiation or light, often with a focus on its ability to cause photochemical reactions. Here are the key...

An active infrared (IR) system is a type of technology that uses infrared radiation actively emitted and detected by sensors for various purposes. Here are the key features and applications of active...

An active-cavity radiometer is a highly sensitive instrument used to measure radiant energy (power per unit area), often in the form of electromagnetic radiation. The key features of an active-cavity...

The term acute bisectrix is used in mineralogy and crystallography to describe a specific optical property of minerals, particularly in relation to their crystal structure and light behavior. Here's...

An optical adapter typically refers to a device or component used in optical systems to facilitate connections between different types of optical fibers, connectors, or interfaces. Here are a few...

An adaptometer is an instrument used to assess the adaptation of the human eye's sensitivity to changes in ambient light conditions. It typically involves exposing the eye to controlled levels of...

The advanced communication technology satellite (ACTS) was a program developed by NASA (National Aeronautics and Space Administration) in the United States to demonstrate and advance satellite...

A television format with enhanced vertical resolution (400 lines as compared with the standard 330) that, unlike high-definition television, can operate on existing bandwidths and with existing...

Advanced driver assistance systems (ADAS) refers to a set of safety features and technologies designed to assist drivers in the driving process and enhance overall vehicle safety. These systems use...

An aerial reconnaissance system that can transmit, in near real time, image data recorded by IR and visual-spectrum sensors, providing day, night and foul-weather intelligence.

That image remaining on the detector after the primary stimulus has been removed. In the visual system, the after-image commonly appears as the complementary color of the primary stimulus.

The luminosity that remains in a rarefied gas after an electrodeless discharge has traversed the gas.

An AI system-on-chip (SoC) is an integrated circuit that integrates hardware components optimized for performing AI computations efficiently. These components typically include: AI accelerators:...

A category of systems designed to communicate a photo taken from the air (e.g., aircraft, balloon, satellite) to a ground station. It can be done by direct television transmission of the photo, or by...

A host crystal for chromium that emits pulsed or continuous-wave laser light, tunable from about 720 to 790 nm.

An alexandrite laser is a solid-state laser that utilizes a synthetic crystal made from the rare earth element alexandrite (BeAl2O4:Cr3+). This crystal is capable of emitting laser light in the...

An optical tooling instrument consisting of an objective lens, a focusing lens, an optical micrometer, a reticle and an eyepiece. The alignment telescope projects a precise line of sight to which a...

Commonly known as CR39, this thermosetting plastic is used in the casting of eyeglass lenses because of its toughness and clarity.

Alternating current (AC) is an electrical current in which the direction of flow of electric charge periodically reverses. This reversal occurs at regular intervals, typically in a sinusoidal...

The prevailing temperature in the immediate vicinity of the object; the temperature of its environment.

Substances that exhibit the characteristics of both acids and bases and are capable of both P- and N-type conductivity.

A type of fiber optic sensor that detects alteration in position, distance, pressure, liquid level or temperature by transmitting light across a gap to a reflector; a change in the light returned to...

A device that converts an analog signal, that is, a signal in the form of a continuously variable voltage or current, to a digital signal in the form of bits.

An optical system with different focal lengths or magnification levels in perpendicular planes to the optical axis.

A lens that distorts an optical image.

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.

A system used for measuring direct solar radiation.

The measured planar or solid angle of related aspects of an optical system with respect to an optical axis.

A device that prevents electrons from a saturated pixel in a CCD imaging device from spilling into an adjacent pixel. The antiblooming gate drains a pixel of any charge in excess of its full-well...

An APD detector, or avalanche photodiode detector, is a type of photodetector used to detect light or optical signals by converting incoming photons into electrical current. It operates based on the...

An instrument designed to measure the numerical aperture of an objective.

A system that satisfies the Abbe sine condition, and is free from spherical aberration and coma.

An optical system that is corrected chromatically for three colors simultaneously.

Displacement in a direction perpendicular to that of the intended displacement, as in a translation stage with simple flexures that experiences vertical displacement during horizontal motion; it is...

The ability of a machine to perform certain complex functions normally associated with human intelligence, such as judgment, pattern recognition, understanding, learning, planning, and problem...

An optical system having one or more lens or mirror components that have nonspherical surfaces. These surfaces, whether reflecting or refracting, serve to advance or retard the incident wavefront,...