# Grating > Mediated Wiki article. Canonical URL: https://mediated.wiki/source/Grating > Markdown URL: https://mediated.wiki/source/Grating.md > Source: https://en.wikipedia.org/wiki/Grating > Source revision: 1356035284 > License: Creative Commons Attribution-ShareAlike 4.0 International (https://creativecommons.org/licenses/by-sa/4.0/) {{short description|Framework of spaced bars that are parallel to or cross each other}} {{For|the process of grating food|Grater}} {{Wiktionary|grating}} [[File:Metro ventilation grid, Alameda Afonso Henriques, Lisbon, Portugal julesvernex2.jpg|thumb|A metro ventilation grating in [Lisbon](/source/Lisbon)]] A '''grating''' is any regularly spaced collection of essentially identical, [parallel](/source/Parallel_(geometry)), elongated elements. Gratings usually consist of a single set of elongated elements, but can consist of two sets, in which case the second set is usually [perpendicular](/source/perpendicular) to the first (as illustrated)."[http://www.supshitl.com/] {{Webarchive|url=https://web.archive.org/web/20140702173530/http://www.supshitl.com/|date=2014-07-02}}" by sanorient, [The frp Demonstrations Project](/source/The_frp_Demonstrations_Project). When the two sets are perpendicular, this is also known as a grid (as in [grid paper](/source/grid_paper)) or a [mesh](/source/mesh). == As filters == A grating covering a [drain](/source/drain_(plumbing)) (as illustrated) can be a collection of iron bars (the identical, elongated elements) held together (to ensure the bars are parallel and regularly spaced) by a lighter iron frame. Gratings over drains and [air vent](/source/air_vent)s are used as [filter](/source/filter_(chemistry))s, to block movement of large solids (e.g. people) and to allow movement of fluids. A [register](/source/Register_(air_and_heating)) is a type of grating used in [heating, ventilation, and air conditioning](/source/heating%2C_ventilation%2C_and_air_conditioning), which transmits air, while stopping solid objects. File:Vindobona Hoher Markt-71.JPG|Grating - drain cover, [ancient Roman architecture](/source/ancient_Roman_architecture) at [Vindobona](/source/Vindobona), [Austria](/source/Austria). File:Montreal Sewer Cover.jpg|Sewer grating ([manhole cover](/source/manhole_cover)) that can be driven on despite letting water pass through File:Tree grating, Washington, D. C. (3678939694).jpg|[Tree grating](/source/Tree_grate) that can be walked on despite letting water pass through == As decking == {{see also|Anti-slip grating}} Grating can also come in panels that are often used for [decks](/source/Deck_(bridge)) on [bridge](/source/bridge)s, [footbridge](/source/footbridge)s and [catwalks](/source/Footbridge). Grating can be made of materials such as [steel](/source/steel), [aluminum](/source/Aluminium), [fiberglass](/source/fiberglass). Fiberglass grating is also known as [FRP grating](/source/FRP_grating). They are used to optimize bending stiffness while minimizing weight. File:Grating at the historic John Street Roundhouse, Toronto.jpg|Close up view of [anti-slip grating](/source/anti-slip_grating) File:Puente rejilla.jpg|Bridge showing deck grating driving surface File:Stahlbau mit Gitterrosten.JPG|Walkway gratings at a power plant ==Optical grating== [[File:Moire2grd.png|thumb|Superimposed transparent gratings generating a [Moiré pattern](/source/Moir%C3%A9_pattern)]] [[File:Waveforms.svg|thumb|Graphs of [sine](/source/sine_wave), [square](/source/Square_wave_(waveform)), [triangle](/source/triangle_wave), and [sawtooth](/source/sawtooth_wave) profiles.]] As optical elements, optical gratings are images having the characteristic pattern of alternating, parallel lines. The lines alternate between high and low [reflectance](/source/reflectance) (black-white gratings) or high and low [transmittance](/source/transmittance) (transparent-opaque gratings). The grating profile is the function of the reflectance or transmittance perpendicular to the lines. This function is generally a [square wave](/source/Square_wave_(waveform)), in that every transition between lines is abrupt. A grating can be defined by six parameters: * ''[Spatial frequency](/source/Spatial_frequency)'' is the number of cycles occupying a particular distance (e.g. 10 line pairs per millimeter). The period of the grating is the inverse of the spatial frequency, measured in distance (e.g. 0.1 mm). * ''[Duty Cycle](/source/Duty_Cycle)'' is the relative thickness of high and low lines. The duty cycle is the ratio of the width of the low line (black or opaque) to one whole grating period. * ''[Profile](/source/Square_wave_(waveform))'' is the shape of the repeating pattern, which is typically a square wave but can also be any periodic pattern ([sine wave](/source/sine_wave), [triangle wave](/source/triangle_wave), [sawtooth wave](/source/sawtooth_wave), etc.). * ''[Contrast](/source/contrast_(vision))'' is a measure of the difference in luminance between the high lines of the grating and the low lines. It is usually expressed as [Michelson contrast](/source/Michelson_contrast):Michelson, A. A. (1891). On the application of interference methods to spectroscopic measurements. I. The London, Edinburgh, and Dublin Philosophical Magazine and Journal of Science, Fifth Series, 31, 338-346 and Plate VII. the difference between maximum and minimum luminance divided by their sum. * ''[Orientation](/source/Orientation_(geometry))'' is the [angle](/source/angle) the grating makes with some reference orientation (such as the y-axis in a picture or of another grating). It is usually measured in degree or in radians. * ''[Phase](/source/Phase_(waves))'' is the position of the grating profile relative to some reference position. It is usually measured in [degree](/source/degree_(angle))s (from 0 to 360 for one complete cycle) or in [radian](/source/radian)s (2π for one complete cycle). For example, two identical transparent gratings of 50% duty cycle and the same orientation will appear fully opaque only if the relative phase is π (180 degrees). Gratings with sine wave profiles are used extensively in [optics](/source/optics) to determine the [transfer function](/source/transfer_function)s of [lenses](/source/lens_(optics)). A lens will form an image of a sine wave grating that is still sinusoidal, but with some reduction in its contrast depending on the spatial frequency and possibly some change in phase. The branch of mathematics dealing with this part of optics is [Fourier analysis](/source/Fourier_analysis) while the associated branch of study is [Fourier optics](/source/Fourier_optics). Gratings are also used extensively in research into [visual perception](/source/visual_perception). Campbell and Robson promoted using sine-wave gratings by arguing that the human visual performs a Fourier analysis on retinal images.Campbell, F. W., & Robson, J. G. (1968). Application of Fourier analysis to the visibility of gratings. Journal of Physiology, 197, 551-566. ===Diffraction gratings=== {{main|Diffraction grating}} Grating can also refer to a [diffraction grating](/source/diffraction_grating): a [reflecting](/source/reflection_(physics)) or [transparent](/source/transparency_(optics)) optical component on which there are many fine, [parallel](/source/parallel_(geometry)), equally spaced grooves. They [disperse](/source/Dispersion_(optics)) light, so are one of the main functional components in many kinds of [spectrometer](/source/spectrometer)s, which decompose a light source into its constituent wavelength components. ==See also== * [Grate (disambiguation)](/source/Grate_(disambiguation)) * [Grille (architecture)](/source/Grille_(architecture)) * [Manhole cover](/source/Manhole_cover) * [Pedestrian infrastructure](/source/%3ACategory%3APedestrian_infrastructure) ==References== * Palmer, Christopher, ''Diffraction Grating Handbook'', 8th edition, MKS Newport (2020). [https://www.gratinglab.com/Information/Handbook/Handbook.aspx] {{commons category|Gratings}} Category:Drainage Category:Road infrastructure Category:Pedestrian infrastructure Category:Garden features Category:Building stone Category:Pavements Category:Street furniture --- Adapted from the Wikipedia article [Grating](https://en.wikipedia.org/wiki/Grating) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Grating?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.