Photonics Dictionary: F

Fluorescein is a synthetic organic compound extensively used as a fluorescent tracer in various applications, particularly in medicine and biology. It belongs to the xanthene dye family and is known...

Fluorescence is a type of luminescence, which is the emission of light by a substance that has absorbed light or other electromagnetic radiation. Specifically, fluorescence involves the absorption of...

A powerful method, referred to as FCS, for determining the average diffusion coefficients of fluorescent molecules in solution or membranes. FCS measurements rely on recording the transition of...

A device, also called a fluorescence lifetime instrument, that measures decay curves of fluorescing samples. It generally consists of a gated pulsed flashlamp or a cavity dumped dye laser...

Fluorescence lifetime refers to the average time it takes for a fluorophore, a molecule that absorbs light at one wavelength and emits it at another, to return to its ground state after being excited...

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...

Fluorescence microscopy is a specialized optical imaging technique used in biology, chemistry, and materials science to visualize and study specimens that exhibit fluorescence. Fluorescence is the...

The photographic recording of a subject that exhibits luminescence only for an extremely short time (10-8 s) after the exciting source is removed. In the process, the subject may be illuminated by...

A type of optical microscope that allows the specimen being viewed to be irradiated by ultraviolet, violet and occasionally blue radiation, causing the specimen to fluoresce.

Fluorescent proteins are proteins that exhibit the property of fluorescence, which is the ability to absorb light at a specific wavelength and emit light at a longer wavelength. These proteins are...

A fluorescent screen refers to a phosphorescent or fluorescent-coated surface that emits visible light when exposed to other forms of electromagnetic radiation, such as x-rays or ultraviolet light....

Agents used for testing light sources and natural daylight with visual and instrumental assessment using a set of white metameric pairs.

The combination of the organic dye in a stained specimen and the antibodies produced that is detected by exposure to light.

An instrument used to measure the duration of fluorescence emanating from a biological sample to monitor and evaluate its condition.

The analysis and measurement of the fluorescence emitted by a source. Fluorometric processes are more sensitive than light absorption methods and are rapidly being applied in medical and biological...

A fluorophore is a molecule or a portion of a molecule that has the ability to emit light upon excitation by an external energy source, such as ultraviolet or visible light. The process by which a...

The study and analysis of images produced by a fluoroscope.

A method of synthesis for crystals such as KTP. The process involves the use of a high-temperature solution called flux to enable crystal growth. Flux dissolves the elements of the desired crystal,...

An alteration in the direction of the magnetic induction at the interface between two media of different permeability.

Time elapsed during the radiant output change from 10 to 90 percent of maximum in a light-emitting diode or laser. Usually expressed in nanoseconds and measured from the moment of onset of the...

The moving spot of light emitted by a source, generally a cathode-ray tube, to illuminate specific points of an area carrying light and dark regions according to a specific pattern.

A microscope that uses a flying spot scanner, directed through the eyepiece, as a light source to determine the features of a transparent specimen. The flying spot is modulated by the varying density...

A device used to scan, with a small, intensely bright spot, portions of a picture surface and to transform the original picture into a series of electrical signals. In optical character recognition,...

FMCW lidar stands for frequency-modulated continuous wave lidar. It is a type of lidar (light detection and ranging) technology used for remote sensing, distance measurement, and 3D mapping. FMCW...

The focal length of a lens is the distance between the lens's optical center (or principal point) and the image sensor or film when the lens is focused at infinity. In simple terms, it is the...

A linear or two-dimensional matrix of individual detector elements, typically used at the focus of an imaging system.

A single-particle scattering technique in which an incident laser beam is tightly focused by means of lenses to yield a focal spot in the scattering material with a diameter on the order of the...

A retroreflector that can focus a beam of light, with one planar reflective surface, one spherical and a third that is either planar or convex cylindrical.

Unit of illuminance equal to one lumen per square foot. (fc).

Unit of luminance equal to 1/p candela per square foot. (fl).

The application of ultraviolet, x-ray, infrared and conventional photography to law enforcement.

A night-vision device that uses one or more infrared transducers to scan a scene in the 3- to 5-µm or 8- to 12-µm spectral region, convert the infrared radiation to electronic data and...

The Foucault test is performed by moving a knife edge laterally into the image of a small point source. The eye, or a camera, is placed immediately behind the knife edge, and the exit pupil of the...

A polarizing prism formed from calcite that is like the Nicol prism but has the two parts divided by a thin air-film and cut to such angles that the extraordinary beam will be transmitted and the...

A solid-state laser consisting of active atoms or ions of a transition metal, rare-earth metal or actinide, imbedded in a crystal or glass material, often garnet. Excitation and transfer to different...

A phenomenon that occurs in WDM and DWDM systems when three closely spaced signal wavelengths near the zero-dispersion wavelength interact with each other, producing a fourth wavelength that...

An instrument using a Michelson interferometer, a beamsplitter, two plane mirrors and a detector to give Fourier analysis of the detector signal to provide the desired spectrum.

Any of the various methods of decomposing a signal into a set of coefficients of orthogonal waveforms (trigonometric functions).

The central portion of the retina that has the greatest sensitivity to form and color.

A method used to generate graphics within a computer system. Rather than dots or lines, fractal graphics work with mathematical formulas that represent the natural curves of the object.

1. To center an image or place it in any part of the television screen desired. Also applies to stills. 2. A single image of the connected multiple images on motion-picture film. 3. The size of the...

Frame rate refers to the frequency at which consecutive images, or frames, are displayed in a video sequence. It is typically measured in frames per second (fps) and determines the smoothness and...

The number of separate images exposed by a cine camera in a second or the number illuminated by a cine projector in a second. By varying the number of images recorded per second, films can be created...

A far-field pattern holographically reproduced image that is categorically considered with three-dimensional lensless photographs.

The dark absorption lines observed in the spectrum of the photosphere of the sun. There are thousands of these lines, the most prominent of which were observed and named by Fraunhofer early in the...

A free-electron laser (FEL) is a type of laser that generates coherent, high-intensity electromagnetic radiation by using a beam of accelerated electrons as the lasing medium. Unlike traditional...

A type of internal photonic connection in an integrated circuit in which a holographic grating is used to focus light at points on a silicon chip, maximizing the speed of signal propagation.