grating(redirected from Foucault grating)
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In spectrophotometry, the element used in a monochromator that disperses white light into the visible spectrum. It is composed of finely etched lines in the reflecting material.
A series of black and white parallel bars of equal width used to measure visual acuity, contrast sensitivity, and resolution of optical systems. The grating can be either square-wave (also called Foucault grating or Foucault pattern), in which the luminance across a bar is constant, or sine-wave, in which the luminance varies sinusoidally (Fig. G6). See cycle per degree; contrast sensitivity function.