Photonics Dictionary: F

1. In raster scan television, one of the two scans that are interlaced to make up a frame. 2. See field of view.

An X-Y electrically addressable series of arrays with individual electron emitters bombarding a phosphor-coated transparent plate. The phosphor is induced into luminescence, similar to traditional...

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...

1. A lens situated at or near the plane of an internal image to project the aperture of a previous objective or erector upon the aperture of a following lens. 2. A lens at or near the plane of a...

An expression of the tolerance of decentration of a laser diode from the optical axis: the region around the axis in the focal plane of the collimator in which the facet can be located and still...

The field of view (FOV) refers to the extent of the observable world or the visible area that can be seen at any given moment through a device, such as an optical instrument, camera, or sensor. It is...

An aperture located at an image plane of an optical system that determines the size and shape of the image.

The angle measured between the focal surface containing the image and a plane normal to the optical axis.

In optics, the geometrical form of an optical surface.

The process whereby the shape of an optical surface is altered by polishing.

The ratio of active to inactive areas on a pixel.

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...

Filoviruses are a family of viruses that are responsible for severe and often fatal hemorrhagic fevers in humans and non-human primates. The name "filovirus" is derived from their filamentous...

A device that holds a number of filters and allows the filter with the desired characteristics to be rotated into an optical aperture.

A low-power telescope with a wide field of view, typically attached to a higher power telescope with a narrower field of view. This enables an observer to locate a celestial object with the...

For a Fabry-Perot interferometer or etalon, a value for the transmission bandwidth which can be calculated as the ratio of the free spectral range to the full width half maximum of the transmission...

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 principal point of a lens relative to the object space.

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

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

The process of grinding the toric surface of a single vision sphero-cylindrical lens.

A type of wide-angle lens that has an angular field above 140° and that exhibits barrel distortion. The most commonly used fish-eye lenses have a field of about 180°, though they are...

Fixed-pattern noise is the measure of the static (nontemporal) differences between pixels when the detector is evenly illuminated. In microbolometers, this effect is mostly caused by mismatch between...

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...

A type of interferometer noted for producing narrow multiple-beam interference fringes. As a result, when compared with the Twyman-Green, the Fizeau interferometer has fewer optical components, does...

A device used to measure the speed of light by adjusting the rotation of a toothed wheel so that light passing through one tooth opening is reflected through the next. This device has since been...

A technique in photometry that uses an oxyhydrogen or oxyacetylene flame to optically excite a solution containing the sample to be analyzed.

Any of a number of instruments that uses a flame to vaporize a solution of the chemical being analyzed so that light may be passed through the vapor. Monochromation of the transmitted light is...

The distance between the locating surface of the lens mount and the image plane.

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 piece of glass having a crude plano surface on each side.

A frame taken with a CCD camera of a surface that is evenly illuminated by diffuse light. This frame shows irregularities in the light-sensing ability of the CCD, such as electronic defects and dust...

An imaging device analogous to a drum scanner, but operating at greater speeds; it uses a row of sensors to traverse an image affixed to a flat surface.

A flexible display refers to a type of electronic visual display that is designed to be bendable, foldable, or rollable, allowing for unconventional form factors and enhanced portability. Unlike...

One of the two major types of optical glass, the other being crown glass. Flint glass is softer than crown glass, has a higher dispersion and usually a higher refractive index.

A material that surrounds a fiber optic cable's buffer tubes to prevent moisture from entering if the jacket is breached.

In various fields such as fluid dynamics, microfluidics, and biotechnology, a flow channel refers to a defined pathway through which a fluid (liquid or gas) flows. The channel can be of various...

Flow chemistry, also known as continuous-flow chemistry, is a chemical manufacturing process where reactions take place in a continuous stream of fluids (liquids or gases) rather than in batch...

Flow cytometry is a powerful technique used in biology and medicine for the quantitative analysis of the physical and chemical characteristics of cells and particles suspended in a fluid. The method...

A flowmeter is a device used to measure the flow rate or quantity of a fluid passing through a particular point in a system. It works by sensing the velocity of the fluid passing through it and...

A technique developed to measure the molecular weight of macromolecules by analyzing the spontaneous fluctuations that occur in the inherent thermodynamic concentration of solute molecules in a...

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...

Optical glass that possesses a refractive index equal to or less than 1.5, and an Abbe number that ranges from 62 to about 85.

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...