Photonics Dictionary: A

An Abbe condenser is a type of optical component used in microscopy to enhance the illumination of the specimen. Named after the German physicist Ernst Abbe, who developed it in the 19th century, the...

A dispersion relation defined in order to value the reciprocal amount of dispersion. It is defined as the refractivity over the difference in index values of the shortest and longest visible...

An aberration sensor typically refers to a component or feature in optical systems, especially in telescopes or cameras, that detects and quantifies aberrations. Aberrations are imperfections or...

An absorption lens is a type of optical lens that not only focuses or diverges light but also significantly absorbs certain wavelengths of the incident light. This dual function makes it different...

An achromatic lens is a type of optical lens designed to minimize chromatic aberration, which is the inability of a lens to focus all colors of light to the same convergence point. Chromatic...

Active transport is a biological process by which cells move molecules or ions across their cell membrane against their concentration gradient, meaning from a region of lower concentration to a...

Transformation of an image, such as a change in position or scale, that does not alter the linearity of the original image.

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 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 lens, usually having one or more cylindrical surfaces, used to produce distorted images and later to restore them to true form.

A lens that distorts an optical image.

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

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,...

An aspheric lens is a type of lens whose surface profiles deviate from the traditional spherical shape. Unlike spherical lenses, which have a constant curvature across their surfaces, aspheric lenses...

A method of data multiplexing that can provide large, instantaneous bandwidths for busy traffic while permitting slow traffic to use that bandwidth between bursts. Very short, fixed-length packets or...

A mode of data transmission whereby each bit of information is generated separately, with some stop/start code to indicate the interval between bits.

The real part of the axial propagation constant for a particular mode. The attenuation coefficient for the mode power is twice the attenuation constant.

A device for automatic exposure control in which a motor-driven diaphragm adjusts the aperture in response to a signal from a photocell detecting ambient light.

Automated optical inspection (AOI) is a technology used in manufacturing processes, particularly in electronics, to automatically inspect and detect defects or anomalies in products. AOI systems use...

A system for automatic industrial process control or measurement, consisting of an optical module for image acquisition, a segmentation processor to isolate the image from its background, and an...

Eye blink or head movement in response to bright light. Aversion responses such as blinking are sufficient protection from less hazardous lasers, including Class 2 lasers. An eye blink can occur, at...

The number of molecules in one gram mole of a substance, numerically approximated by 6.02 x 1023.

The propagation constant evaluated along the axis of a waveguide, that is, in the direction of transmission. Also called axial propagation wave number.

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....

In various fields of science and technology, an active element typically refers to a component or substance that actively participates in or facilitates a process, operation, or reaction. Here are...

In the context of a laser diode, the active region is a critical part of the device where the primary light generation occurs. Laser diode active region: The active region in a laser diode is...

An antigen is any substance that is capable of triggering an immune response in an organism. Antigens are typically proteins or large polysaccharides, although other types of molecules can also act...

Also known as aplanatic lens. A lens corrected for spherical aberration and coma.

An apochromat, often referred to as an apochromatic lens or apochromatic objective, is a type of optical system designed to minimize chromatic aberration. Chromatic aberration occurs when different...

An aspheric mirror is an optical mirror surface that deviates from the shape of a perfect sphere, having a non-spherical surface profile. Unlike traditional spherical mirrors, which have a curved...

Ray oriented and assumed to propagate orthogonal to the optical axis

Abaxial spherical aberration, also called oblique spherical aberration, refers to a specific type of optical aberration that occurs in lens systems. It is a form of spherical aberration that affects...

Image of a uniform source through the sample of a microscope image system. Light from the sample plane is reimaged by the objective into the image plane.

A form of roof prism used to invert an image. The prism has faces cut normal to the optical axis; therefore, the prism may be placed within the optical path of a system and invert the image without...

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 Abbe-Porro prism, often referred to simply as a Porro prism, is an optical prism used in binoculars and other optical instruments to invert and reverse an image. It is named after the Italian...

The ablation threshold refers to the minimum amount of energy, such as laser energy or intense radiation, required to remove material from a surface through ablation. Ablation itself is the process...