Zurich Instruments AG - Lock-In Amplifiers 4/24 LB

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253 terms

Photonics Dictionary: F

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flashtube -> electronic flash unit

A small xenon-filled tube with metal electrodes fused into the ends. The gas flashes brilliantly when a condenser is discharged through the tube. The duration of the flash is primarily dependent upon...

far-field diffraction pattern

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.

far-field region

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...

Farnsworth-Munsell test -> color perception test equipment

Equipment for testing an observer's color vision. Some tests require the identification or ordering of colored samples. The commercially available examples include: the Ishihara plates, on which...

FEL

free-electron laser

Felgett advantage

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...

ferroelectric crystal

A crystal capable of being polarized in the reverse direction when an electric field is applied.

ferroelectric domain

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

ferroelectric film

Film in which electric polarization is reversible when influenced by an electric field.

ferroelectric materials

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...

ferroelectricity

The phenomenon whereby certain crystals exhibit spontaneous electric polarization. It is analogous with ferromagnetism.

fiber optic field flattener

A plate consisting of fused optical fibers with both surfaces ground and polished, and having the entrance surface curved to match the image curvature of the input lens system. The plate transmits to...

field

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

field curvature -> curvature of field

A lens aberration that causes a flat object surface to be imaged onto a curved surface rather than a plane.

field effect transistor photodetector

A photodetector employing photoregeneration of carriers in the channel region of an FET structure to provide photodetection with current gain.

field emission display

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...

field emission microscope

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...

field frequency -> field repetition rate

The number of fields scanned per second in a television system. The US standard is 60. Also called field frequency.

field glass

A handheld binocular telescope that is commonly of the Galilean type.

field ion microscope

An extremely powerful microscope that renders individual ionized atoms visible by using an electric field to propel the ions to a fluorescent screen where they are magnified.

field lens

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...

field of collimator

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...

field of view

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...

field pattern

Intensity of emission as a function of direction in a given plane.

field repetition rate

The number of fields scanned per second in a television system. The US standard is 60. Also called field frequency.

field stop

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

field tilt

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

film weld

The butt (edge to edge) splice of two pieces of film produced by a heat splicer that melts the edges together; used in editing motion picture film.

filter wheel

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

Fizeau toothed wheel

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...

flat panel display

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.

flat-field frame

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...

flat-field lens

A lens that focuses on a flat plane because its field of curvature is close to zero.

flow channel

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...

fluorescence correlation spectroscopy

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...

four-level laser

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...

Franz-Keldysh effect

Observed lengthening in wavelengths of the optical absorption edge of a semiconductor with the application of an electric field.

free-electron laser

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...

Frenkel defect

A crystal defect that is a combination of a vacancy and an interstitial created by the removal of an ion from a lattice and its placement in an interstitial position.

fresnel

A unit of frequency equivalent to 1012 cps. Named for Augustin Jean Fresnel, a French physicist known for his work in light and optics.

Fresnel diffraction

1. Also known as near-field diffraction. The field of radiation sent through an aperture in an absorbing screen at large distances as compared with the wavelength and the dimensions of the aperture,...

Fresnel fringe

A single band in a group of light and dark bands that can be viewed in the periphery of Fresnel diffraction shadow.

Fresnel hologram

A hologram formed with an object located close to the recording medium.

Fresnel lens

A Fresnel lens is a type of optical lens that consists of a series of concentric grooves or steps carved into a flat, thin piece of transparent material, typically plastic or glass. This design...

Fresnel loss -> Fresnel reflection loss

Reflection losses incurred at input and output of optical elements because of the difference in refractive index between glass and the immersion medium.

Fresnel mirrors

Two plane mirrors that are not wholly located in the same plane. When light from a point source or slit reflects from the two mirrors, interference bands are revealed in the region where the light...

Fresnel number

In a lens, the square of the radius of its aperture divided by the product of the focal length and the wavelength. It measures the importance of diffraction in the image formed by the lens. A small...

Fresnel reflection

Fresnel reflection refers to the reflection of light at the interface between two different media with different refractive indices. This phenomenon was named after the French engineer and physicist...

Fresnel reflection loss

Reflection losses incurred at input and output of optical elements because of the difference in refractive index between glass and the immersion medium.

Fresnel reflection method

A method for measuring the index profile of an optical fiber by measuring the reflectance as a function of position on the end face.

Photonics DictionaryF