Photonics Dictionary

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

A device that measures the intensity of photochemically active radiation, particularly from the sun. One form of this instrument determines the fluorescence initiated by the radiation.

Actinometry refers to the measurement of the intensity of radiation, particularly ultraviolet (UV) radiation or sunlight. It is commonly used in atmospheric science, environmental monitoring, and...

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 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...

An axicon is a type of optical component characterized by its conical shape and its ability to transform a collimated Gaussian beam of light into a ring-shaped beam with a gradually increasing...

A ball lens is a small, spherical optical component typically made of glass or other transparent materials. It is characterized by its spherical shape, with both its front and back surfaces forming...

Beam profiling is a technique used to characterize and analyze the spatial intensity distribution of a laser beam. It involves measuring and visualizing how the optical power or intensity is...

Cathode radiant sensitivity refers to the ability of a photocathode to convert incident radiant energy, typically in the form of light, into an electrical signal. Photocathodes are components used in...

A photometer that uses a set of color filters to measure the intensity of light in various regions of the spectrum.

A multidimensional array of values that is commonly used in programming to describe a time series of image data. Each dimension in the data cube represents a new attribute, while the cells of the...

A quantitative measurement of the coherence of a light source; equal to the visibility (V) of the fringes of a two-beam interference test: where Imax equals the intensity at a maximum of the...

A detector-Dewar assembly typically refers to a combination of a detector and a Dewar flask used in scientific instruments, particularly in the field of infrared spectroscopy or other applications...

Diffraction efficiency is a measure of how effectively a diffractive optical element (DOE) or diffraction grating directs light into specific diffraction orders or achieves a desired optical effect....

A diffraction grating is an optical component consisting of a surface with a periodic structure of equally spaced, parallel grooves or rulings. These rulings act as an array of closely spaced slits...

Diffuse reflectance spectroscopy (DRS) is a nondestructive analytical technique used to investigate the optical properties of materials, particularly in the field of spectroscopy. Unlike traditional...

Intensity distribution in the image of an edge. The gradient of the edge-response curve is a measure of the image quality of the optical system under test.

An enzyme-linked immunosorbent assay (ELISA) is a laboratory technique used to detect and measure the presence of specific substances, such as antibodies, antigens, proteins, hormones, or other...

Fluorescence imaging technique in which the excitation light from the objective is directed into the sample producing emission at all angles. Light emitted into the objective is measured allowing the...

Etaloning is an optical phenomenon that occurs in imaging systems, particularly in devices such as spectrometers, interferometers, and cameras. It is characterized by the appearance of interference...

A fiber optic sensor is a device that uses optical fibers to detect and measure physical, chemical, biological, or environmental parameters. Unlike traditional electrical sensors, fiber optic sensors...

A fiber optic spectrometer is a device used for measuring the spectral content of light. It utilizes optical fibers to transmit light from a source to a spectrometer unit, where the light is...

An optical recording technique that uses light source(s), a beamsplitting cube, light detector(s) and an optical fiber chronically implanted in animal brain to deliver excitation light to neurons...

Fluence is a term used in various scientific and technical disciplines to describe the amount of something per unit area. The specific meaning of fluence can vary depending on the context in which it...

Fluorescence lifetime imaging (FLIM) is an advanced imaging technique that provides information about the lifetime of fluorescence emissions from fluorophores within a sample. Unlike traditional...

FTIR (Fourier transform infrared) spectrometer is a powerful analytical instrument used to obtain an infrared spectrum of absorption or emission of a solid, liquid, or gas sample. It operates based...

The full width at half maximum (FWHM) is a measure used in various fields, particularly in spectroscopy, signal processing, and imaging, to characterize the width or extent of a distribution, peak,...

Functional near-infrared spectroscopy (fNIRS) is a non-invasive neuroimaging technique that measures changes in hemoglobin concentration in the brain. It utilizes near-infrared light to penetrate the...

A gas lamp used in the early 1900s as a physical standard for measurement of luminous intensity. The Hefner unit was superseded by the candle and then by the candela.

Hyperspectral resolution refers to the level of detail or granularity in the spectral information captured by a hyperspectral imaging system. In hyperspectral imaging, the electromagnetic spectrum is...

An infrared detector is a device that is used to detect and measure infrared radiation, which lies beyond the visible spectrum of light. These detectors are utilized in various applications,...

A thermistor that uses a semiconductor that is sensitive to infrared radiation to measure the radiation's intensity.

Integration time, in the context of optics, imaging systems, and sensor technology, refers to the duration over which a sensor collects and accumulates incoming light or signal. It is a crucial...

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.

A material that is present or added to a sample undergoing spectroscopic analysis, to serve as an intensity reference for spectral measurements.

A unit of measurement of luminous intensity based on a physical standard, a set of calibrated carbon filament lamps. The old candle unit was superseded by the new candle or candela.

The laser damage threshold refers to the maximum level of laser intensity that a material can withstand without experiencing damage. It is a critical parameter in laser applications and is...

A lumen is a unit of measurement used to quantify the amount of luminous flux, which is the perceived power of light. In other words, the lumen measures the total amount of visible light emitted by a...

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.

A magnetometer is a scientific instrument used to measure the strength and/or direction of a magnetic field. It can detect and quantify the intensity of magnetic fields in its vicinity. Magnetometers...

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 measurement of the intensity of spectral lines by the examination of a very small area under a microscope and the measurement of the density at any point of the image.

In optics, "mode beating" refers to an interference phenomenon that can occur in laser systems with multiple longitudinal modes. Longitudinal modes are specific electromagnetic field patterns that...

A near-infrared (NIR) spectrometer is an analytical instrument used to measure the absorption, transmission, or reflection of light in the near-infrared region of the electromagnetic spectrum....

A monitoring technique used to measure the oxygen saturation levels in the brains of patients, commonly in operating room and neonatal intensive care unit settings. The technique, which is based on...