Photonics Dictionary: F

The maintenance of the same scanning relationship between the transmitting scanning spot and receiving scanning spot for each scanning line transmitted in a facsimile system.

The process by which the light from the images of photographic film is encoded into electrical signals for video transmission.

A grinding process that employs fine emery.

A method used to produce precision spherical and aspheric molded glass lenses without grinding or polishing.

A finite version of Shannon's sampling theorem that states that a class of functions can be reconstructed exactly by a sufficient number of spectral samples; the reconstructed function is an explicit...

The process of grinding the concave surface of a single-vision spherical lens.

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

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...

The process whereby a rotating wheel carries grains of an abrasive, suspended in a vehicle, across the surface of the optical glass to be ground. The workpieces are forced downward by pneumatic...

Fusion ignition refers to the point in a controlled nuclear fusion reaction where the energy released by the fusion reactions becomes self-sustaining, leading to a continuous release of energy...

Free-space optics (FSO), also known as optical wireless communication or optical wireless networking, refers to the transmission of data using modulated beams of light through free space (air or a...

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 multiple-beam interferometer, usually consisting of two flat plates, with high reflective ability. The plates are set parallel to one another by spacers so that lightwaves may bounce back and forth...

A means of determining a prism's index of refraction by placing the prism so that its emergent face is perpendicular to the incident beam. This arrangement permits the determination of the prism's...

With respect to a unit cell in a crystal structure, the property defining an atom located at the center of each face.

The reproduction of a picture or image, produced by scanning the image and converting it into electrical signals that carry the image to be reproduced. Also known as fax.

In imaging technology, assigning color to black and white images to differentiate features or convey information. Also called colorizing.

A set of rays through a lens originating at a common point and contained in one plane.

The diffraction pattern of a source such as a light-emitting diode, injection laser diode or the output end of an optical waveguide observed at an infinite distance from the source.

A region far from an aperture or source where the diffraction pattern is essentially the same as that at infinity. Changes in diffraction patterns of points within the far-field region are...

A laser with output over a wide range of wavelengths spanning the far-infrared region of the spectrum (30 to 1000 µm); typically, it consists of a metal or dielectric waveguide one to two...

The Faraday effect, named after the English scientist Michael Faraday, is a phenomenon in physics where the polarization plane of light is rotated when the light passes through a transparent medium...

The fiber optic connector standard for Nippon Telephone & Telegraph (NTT) installations, developed with Nippon Electric Co. (NEC).

In image processing and machine vision, the process in which an initial measurement pattern or some subsequence of measurement patterns is transformed to a new pattern feature. In image pattern...

A circuit that permits feedback in an electronic device.

A system designed to control the output quantity of a device by returning a portion of its output signal to its input. This results in the manipulation of the input quantity so that the desired...

The signal-to-noise ratio (SNR) obtained with a Fourier transform spectrometer when detector noise prevails, which exceeds the SNR of a scanning spectrometer in the same time by a factor proportional...

A femtosecond laser is a type of laser that emits ultrashort pulses of light with durations on the order of femtoseconds, where one femtosecond is equal to 10-15 seconds. These lasers are capable of...

The region of a ferroelectric crystal where spontaneous polarization is uniformly directed.

Ferroelectric materials are a type of dielectric materials that exhibit spontaneous electric polarization, meaning they possess a permanent electric dipole moment even in the absence of an external...

The properties of certain materials that cause them to have relative permeabilities that exceed unity. This permeability permits the materials to exhibit hysteresis.

A mechanical fixture, generally a rigid tube, used to confine the stripped end of a fiber or a fiber bundle.

The mechanical centerline through the core of an optical fiber.

The lowest frequency at which the magnitude of the fiber transfer function decreases to a specified fraction of the zero frequency value. Often, the specified value is one-half the optical power at...

A fiber Bragg grating (FBG) is a type of optical filter that is inscribed or "written" into the core of an optical fiber. It consists of a periodic modulation of the refractive index along the length...

Fiber joints, also known as fiber optic splices, refer to the connection points where two optical fibers are permanently joined together to form a continuous optical transmission path. These joints...

A fiber laser is a type of laser in which the active gain medium is an optical fiber doped with rare-earth ions such as erbium, ytterbium, or neodymium. Fiber lasers generate coherent light through...