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In mathematics, physics, and engineering, spatial frequency is a characteristic of any structure that is periodic across position in space. The spatial frequency is a measure of how often sinusoidal components (as determined by the Fourier transform) of the structure repeat per unit of distance. The SI unit of spatial frequency is cycles per meter. In image-processing applications, spatial frequency is often expressed in units of cycles per millimeter or equivalently line pairs per millimeter. In wave mechanics, the spatial frequency is commonly denoted by 〔SPIE Optipedia article: ("Spatial Frequency" )〕 or sometimes , although the latter is also used〔As in e.g. Planck's formula.〕 to represent temporal frequency. It is related to the wavelength by the formula : Likewise, the angular wave number , measured in radians per meter, is related to spatial frequency and wavelength by : ==Visual perception== In the study of visual perception, sinusoidal gratings are frequently used to probe the capabilities of the visual system. In these stimuli, spatial frequency is expressed as the number of cycles per degree of visual angle. Sine-wave gratings also differ from one another in amplitude (the magnitude of difference in intensity between light and dark stripes), and angle. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「spatial frequency」の詳細全文を読む スポンサード リンク
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