Photonics Dictionary

Flux per unit solid angle.

An interferometer that functions by first detecting the light striking each aperture and then combining the two detector outputs. With an intensity interferometer, the primary collectors need not be...

The process in which the electron beam of a cathode-ray tube varies in intensity in accordance with the magnitude of the signals it receives.

A type of fiber optic sensor that responds to a change in the intensity of received light caused by the displacement or other phenomena being measured.

Luminous flux emitted by a source in a given range of directions; the unit of measure is the lumen/steradian, now known as the candela.

The average intensity of a light source measured over all directions.

The average luminous intensity of a point light source measured over all directions.

The radiant energy emitted within a time period per unit solid angle, usually measured in watts per steradian.

The inherent laser amplitude noise relative to the average optical power produced by the laser; the RIN decreases rapidly as current is increased.

A beam instability, induced by index of refraction inhomogeneities and component damage of dirt and dust particles, that exhibits exponential growth and causes both system degradation and energy loss...

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...

The Abney effect, named after its discoverer Sir William de Wiveleslie Abney, refers to a phenomenon in color perception where the appearance of a color is influenced by the brightness of its...

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...

The natural log of the ratio of absorbed intensity over the total intensity which gives a constant value assuming a stable volume as well as energy. In optical physics the absorbance may be defined...

An absorbing wedge is an optical device used to control the intensity of light passing through it by absorbing a portion of the light. It is typically used in experiments and optical systems where...

Absorption is the process by which a material takes in energy from electromagnetic radiation (such as light, heat, or sound) and converts it to other forms of energy, typically internal energy (such...

An absorption band is a range of wavelengths, frequencies, or energies in the electromagnetic spectrum within which a substance absorbs radiation. It appears as a dark band in a spectrum where the...

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 absorption line is a dark line in a spectrum that occurs when a specific wavelength of light is absorbed by atoms or molecules in a medium (such as a gas or a solid) as light passes through it....

An absorption peak refers to a sharp increase or spike in the absorption of electromagnetic radiation at a particular wavelength or energy level. It is a distinctive feature in the absorption...

The measured change in absorption at a single wavelength while altering experimental parameters such as the incident intensity or pulse width.

Acousto-optic deflection refers to a phenomenon where the trajectory of light is altered by acoustic waves propagating through a material. This effect is utilized in acousto-optic devices, which are...

Acoustical holography is a technique used to visualize and analyze sound fields in three-dimensional space. It involves capturing the complex spatial distribution of acoustic waves, much like how...

An acousto-optic deflector (AOD) is a type of device that utilizes the acousto-optic effect to control the direction of light beams. It operates by modulating the refractive index of an optically...

Acousto-optic diffraction refers to the process where light passing through an optically transparent material is diffracted due to the modulation of its refractive index by an acoustic wave...

Acousto-optic modulation refers to the process of using acoustic waves to modulate the properties of light passing through an optically transparent material. This modulation occurs due to the...

An acousto-optic modulator (AOM) is a device that utilizes the acousto-optic effect to modulate the amplitude, phase, frequency, or polarization of a laser beam or other coherent light source. It...

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...

Acousto-optics is a branch of physics that deals with the interaction of sound waves (acoustic waves) and light waves (optical waves) within a medium. It primarily focuses on phenomena where acoustic...

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...

Actinometry refers to the measurement of the intensity of radiation, particularly light, with a specific focus on its ability to cause photochemical reactions. Radiation measurement:...

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-matrix display is a type of flat-panel display technology where each pixel is actively controlled by one or more thin-film transistors (TFTs). This technology is commonly used in liquid...

An active matrix organic light-emitting diode (AMOLED) display is a type of flat-panel display technology that combines the active matrix addressing scheme with organic light-emitting diodes (OLEDs)....

An OLED display that has an integrated electronic backplane as its substrate. Active-matrix OLED displays use at least two thin-film transistors (TFTs) to control the on-current at each OLED cell or...

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 additive color process refers to the method of creating color by combining different wavelengths of light. This process is fundamental in various applications, particularly in: ...

The additivity of luminance refers to a principle in visual perception and color theory where the perceived brightness of a combination of light sources or colors is the sum of the brightness of each...

Adiabatic laser colorimetry is a technique used to measure the color of materials based on the principle of adiabatic demagnetization. Principle: Adiabatic laser colorimetry relies on the...

The adjacency effect refers to a phenomenon in remote sensing and image analysis where the characteristics of an object or area are influenced by its proximity to other objects or features within the...

A glow discharge lamp consisting of a cold cathode and a mixture of inert gases. The intensity of illumination varies with the applied signal voltage. This lamp was commonly used as a source of...

An instrument that reads alphabetic, numerical and special characters by means of a photosensor that measures the varying intensity of the characters reflected from a light source.

An optical instrument that uses a yellow light of varying intensity with red and blue lights of fixed intensity to test for colorblindness.

In image processing, methods of reducing image defects that result from false data. Techniques include sampling, linear intensity, filtering a high-resolution image to produce a low-resolution image,...

Characteristic of an absorber in the IR region, whereby absorption increases as a direct function of the intensity of the incident, continuous radiation.

The second adjustable iris diaphragm in an optical system. In the common microscope condenser system, it usually is located beneath the substage condenser on a transmitted light microscope. When the...

Any irregular motion, variation in intensity or change in color that arises because of atmospheric turbulence during the observation of an astronomical phenomenon or object.

The Atmospheric Correction Now software (ACORN) is a tool used in remote sensing and satellite imagery processing. Its primary function is to correct satellite imagery for atmospheric effects that...

An atomic absorption spectrometer (AAS) is an analytical instrument used to determine the concentration of specific chemical elements in a sample by measuring the absorption of light at...

Attenuation refers to the gradual loss or reduction of intensity, force, or magnitude of a particular property as it propagates through a medium or travels over a distance. This concept is prevalent...