Curb, gutter, and grating covering a storm drain

A grating is any regularly spaced collection of essentially identical, parallel, 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 to the first (as illustrated). When the two sets are perpendicular, this is also known as a grid. Image File history File linksMetadata Download high resolution version (800x1200, 1121 KB) Summary Curb, gutter, and storm drain, 2006. ... Image File history File linksMetadata Download high resolution version (800x1200, 1121 KB) Summary Curb, gutter, and storm drain, 2006. ... Curb, gutter, and storm drain A curb or kerb (see spelling differences) is the edge where a raised pavement/sidewalk/footpath, road median, or road shoulder meets an unraised street or other roadway. ... Look up Gutter in Wiktionary, the free dictionary. ... A storm drain, storm sewer, or stormwater drain (in Australia) system is designed to drain excess rain and ground water from an area. ... Look up parallel in Wiktionary, the free dictionary. ... Fig. ... GRID can refer to : GRID computing short for gay-related immune deficiency, a former name for AIDS. See also homosexuality and medical science General Repository for Interaction Datasets, a database of biological interactions hosted at Mount Sinai Hospital in Toronto, Canada This is a disambiguation page — a navigational aid...

Gratings as filters

A grating covering a drain (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 vents are used as filters, to block movement of large particles (such as leaves) and to allow movement of small particles (such as water or air). Look up drain in Wiktionary, the free dictionary. ... Ventilation good and very bad Ventilation is air circulation of air, typically between a room, a tunnel, etc. ... In chemistry and common usage, a filter is a device (usually a membrane or layer) that is designed to block certain objects or substances while letting others through. ...

Diffraction gratings

Grating can also be a diffraction grating: a reflecting or transparent sheet on which there are many, fine, parallel, equally spaced grooves. To meet Wikipedias quality standards, this article or section may require cleanup. ... The reflection of a bridge in Indianapolis, Indianas Central Canal. ... Transparent glass ball In optics, transparency is the property of allowing light to pass. ... Parallel is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. ...

Gratings as pictures

Graphs of sine, square, triangle, and sawtooth gratings. The Y axis shows luminance; the X axis shows space or distance.

A grating can also be a picture having the characteristics of a grating. For example, a picture might be of a collection of parallel black bars separated by equal-sized white bars. These sorts of gratings are described by a graph (illustrated). On the y-axis of the graph is the luminance obtained by moving a light meter over the grating perpendicular to the orientation of the grating. On the x-axis of the graph is the distance the light meter moved. The example is a square-wave grating (see second panel of the illustration); the graph consists of flat, low lines (corresponding to the black bars), with abrupt corners leading to flat high lines (corresponding to the white bars). One period (or cycle) of such a grating consists of one black bar and one adjacent white bar. Gratings where the black bars have a different width from the white bars are rectangular and are described by the ratio of black to white, called its duty cycle. Image File history File links Waveforms. ... Image File history File links Waveforms. ... In trigonometry, an ideal sine wave is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C, where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C... A square wave is a kind of basic waveform. ... A triangle wave is a waveform named for its triangular shape. ... This article or section does not cite its references or sources. ... For images in Wikipedia, see Wikipedia:Images. ... Cartesian means relating to the French mathematician and philosopher Descartes, who, among other things, worked to merge algebra and Euclidean geometry. ... Luminance (also called luminosity) is a photometric measure of the density of luminous intensity in a given direction. ... A light meter is a device used to measure the amount of light. ... Orientation can refer to different things. ... Cartesian means relating to the French mathematician and philosopher Descartes, who, among other things, worked to merge algebra and Euclidean geometry. ... A square wave is a kind of basic waveform. ... In mathematics, a periodic function is a function that repeats its values after some definite period has been added to its independent variable. ... In geometry, a rectangle is a defined as a quadrilateral polygon in which all four angles are right angles. ... In telecommunication and electronics, the term duty cycle has the following meanings: The duty cycle D is defined as the ratio between the pulse duration () and the period (T) of a rectangular waveform In a periodic phenomenon, the ratio of the duration of the phenomenon in a given period to...

Gratings are usually specified by four parameters. Spatial frequency is the number of cycles occupying a particular distance (e.g., 10 lines [or cycles] per millimeter). Contrast is a measure of the difference in luminance between the light parts of the grating and the dark parts. It is usually expressed as Michelson contast (Michelson, 1891): the maximum luminance minus the minimum luminance divided by the maximum luminance plus the minimum luminance. Phase is the position of the graph relative to some standard position. It is usually measured in degrees (from 0 to 360 for one complete cycle) or in radians (2π for one complete cycle). Orientation is the angle the grating makes with some standard orientation (such as the y-axis in a picture). It is also usually measured in degree or in radians. The factual accuracy of this article is disputed. ... In mathematics, physics, and engineering, spatial frequency is a characteristic of any structure that is periodic across position in space. ... This article or section is in need of attention from an expert on the subject. ... This article is about a portion of a periodic process. ... A degree (in full, a degree of arc, arc degree, or arcdegree), usually symbolized °, is a measurement of plane angle, representing 1／360 of a full rotation. ... Some common angles, measured in radians. ... Orientation can refer to different things. ... An angle is the figure formed by two rays sharing a common endpoint, called the vertex of the angle. ...

Grating elements can have luminances other than that of sharp-edged bars. If the graph of a grating is sinusoidal (see top panel in the illustration), the grating looks like a set of blurry light and dark bars and it is called a sine-wave grating. A sine wave or sinusoid is a waveform whose graph is identical to the generalized sine function y = Asin[ω(x − α)] + C where A is the amplitude, ω is the angular frequency (2π/P where P is the wavelength), α is the phase shift, and C is the vertical offset. ... The sine wave or sinusoid is a function that occurs often in mathematics, signal processing, alternating-current power engineering, and other fields. ...

Sine-wave gratings are used extensively in optics to determine the transfer functions of lenses. 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. For the book by Sir Isaac Newton, see Opticks. ... A transfer function is a mathematical representation of the relation between the input and output of a linear time-invariant system. ... A lens. ... Harmonic analysis is the branch of mathematics which studies the representation of functions or signals as the superposition of basic waves. ...

Gratings are also used extensively in research into visual perception. Campbell and Robson (1968) promoted using sine-wave gratings by arguing that the human visual performs a Fourier analysis on retinal images. This does not cite any references or sources. ...

References

Campbell, F. W., & Robson, J. G. (1968). Application of Fourier analysis to the visibility of gratings. Journal of Physiology, 197, 551-566.

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.

See also

• Grate