Photonics Dictionary: F

A salt of formic acid that can be used to enhance the photosensitivity of silver halide crystals.

A fiber optic preform is a cylindrical glass rod or tube used as the starting material for manufacturing optical fibers. It serves as the precursor from which optical fibers are drawn. The process of...

A wide-field multiobject spectroscopy system used in astronomy, in which a bundle of low-loss optical fibers positioned on the target images is rearranged at its other end into a linear array along...

A transformer that is designed to regulate the amount of current that passes through an electron tube's filament.

A hologram formed by the recording of a plane object situated in the focal plane of a lens so that each object gives rise to a parallel beam of light incident on the plate. A collimated reference...

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).

Freeform mirrors refer to reflective optical components that deviate from traditional symmetric or rotationally symmetric shapes, such as spheres or paraboloids. Unlike conventional mirrors, which...

Freeform optics refers to the design and fabrication of optical surfaces that do not follow traditional symmetric shapes, such as spheres or aspheres. Unlike standard optical components with...

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...

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 device in which slab geometry internally compensates for thermal-optic distortion; the solid host material -- glass or Nd:YAG -- is in the form of a rectangular slab with plane parallel faces. The...

Data gathered by a facsimile system and converted into graphic, readable form; generally used in meteorology. Also known as fax chart or fax map.

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

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...

An amplifying device that returns a portion of its output to its input as a means of modifying the device's performance.

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...

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

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...

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...

A weapon launched from a ground-based platform and controlled by a two-way fiber optic data link. The fiber is payed out from a bobbin in the back of the missile.

A fiber optic gyroscope (FOG) is a type of gyroscope that uses the interference of light waves to detect changes in orientation or rotation. It operates based on the principle of the Sagnac effect,...

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...

A fiber optic transceiver, often simply referred to as an "optical transceiver," is a device used in fiber optic communications to transmit and receive data over optical fibers. It integrates both a...

A method of terminating optical fibers by forming a lens directly on the end of the fiber, eliminating the need for precise end-to-end placement or epoxy sealing in fiber connections.

An image-forming instrument in which a strong electrostatic field causes cold emission of electrons from a sharply rounded point or from an object that is located on that point. The electrons are...

The allowable departure from the given figure or geometrical form. It may be described in terms of fringes or wavelengths.

In optics, the geometrical form of an optical surface.

A device used to scan images or information on photographic film for the subsequent relay of information.

An instrument designed to place nongraphic information, usually generated by a computer, onto photographic film. The information is generally encoded as a series of opaque and translucent spots, or...

A fixed-focus camera designed to record the ink impression of fingerprints that have been impressed on a card or form for record purposes.

Small clefts or fissures that penetrate the glass surface in the form of short-hooked crescents. Fire cracks result from a sudden excessive change in temperature.

The separate spectral lines formed by a diffraction grating that are characterized by one wavelength difference in path length between adjacent slits.

Fizeau fringes are interference fringes observed in an interferometer, specifically in a Fizeau interferometer. The Fizeau interferometer is named after the French physicist Armand Fizeau, who...

The emission spectrum formed by the radiation from a sample that has been evaporated by a nonluminous flame.

Nonimage-forming light, concentrated or diffuse, that is transmitted through the lens to the image. It is frequently the result of reflections from lens surfaces, a lens barrel, shutter or lens mount.

A spectroscopic technique used in the detection of free radicals by virtue of their electronic spectra. In this method, an intense light flash is used to form extensive photolysis and yield a high...

An electronic display in which a flat screen is formed by an orthogonal array of display devices, such as electroluminescent devices, light-emitting diodes or liquid crystal cells.