Photonics Dictionary: A

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...

An absorption hologram is a type of hologram in which the image is formed by variations in the absorption of light within the recording medium. Unlike traditional holograms that rely primarily on...

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

Actinic focus refers to the point or plane within an optical system where ultraviolet (UV) light or other actinic radiation converges to form the sharpest possible image. Here are the key aspects: ...

Actinic glass is a type of glass specifically designed to filter or block ultraviolet (UV) light and other forms of actinic radiation. UV filtering: Actinic glass effectively absorbs or...

Actinic radiation refers to electromagnetic radiation that has enough energy to induce photochemical reactions. This type of radiation is primarily in the ultraviolet (UV) range but can also include...

Actinochemistry refers to the branch of chemistry that studies the chemical effects of radiation, particularly light, on substances and chemical reactions. Here are the key aspects of...

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-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...

Visual adaptation refers to the process by which the visual system adjusts to changes in the environment or stimuli over time. It allows the eyes to maintain sensitivity and perception under varying...

Optical addressability refers to the capability to control or manipulate individual elements that emit or modulate light (such as pixels in a display or light sources in an optical network) using...

An ammonia maser is a device that amplifies microwave radiation using ammonia gas molecules in a process analogous to how lasers amplify visible light through stimulated emission of radiation. The...

In digital data transmission, the representation of a bit by change in amplitude of the outgoing signal. Amplitude shift keying (ASK) is less sensitive than phase-shift keying, but can tolerate...

Attenuated total reflectance (ATR) spectroscopy is a technique used in analytical chemistry to obtain IR spectra of samples. It is particularly useful for analyzing solid and liquid samples without...

An attenuator is an electronic or optical device used to reduce the power or intensity of a signal without significantly affecting its waveform or other characteristics. Attenuators are commonly used...

An attoampere (aA) is a unit of electric current in the International System of Units (SI). It is equal to one quintillionth (10-18) of an ampere. The ampere, symbolized as "A," is the base unit of...