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In optics, chromatic aberration (CA), also called chromatic distortion, color aberration, color fringing, or purple fringing, is a failure of a lens to focus all colors to the same point. [ 1 ] [ 2 ] It is caused by dispersion : the refractive index of the lens elements varies with the wavelength of light .
How interference works. The distance between the bright fringe (a) and the dark fringe (b) indicates a change in the light path length of 1/2 the wavelength, so a change of the width of the gap of 1/4 wavelength. So the distance between two bright or dark fringes indicates a change in the gap of 1/2 wavelength.
The gap between the surfaces is constant along a fringe. The path length difference between two adjacent bright or dark fringes is one wavelength λ of the light, so the difference in the gap between the surfaces is one-half wavelength. Since the wavelength of light is so small, this technique can measure very small departures from flatness.
Figure 2. Formation of fringes in a Michelson interferometer Figure 3. Colored and monochromatic fringes in a Michelson interferometer: (a) White light fringes where the two beams differ in the number of phase inversions; (b) White light fringes where the two beams have experienced the same number of phase inversions; (c) Fringe pattern using monochromatic light (sodium D lines
A white light fringe pattern can be considered to be made up of a 'spectrum' of fringe patterns each of slightly different spacing. If all the fringe patterns are in phase in the centre, then the fringes will increase in size as the wavelength decreases and the summed intensity will show three to four fringes of varying colour.
From here we obtain the well known formula for the period p m of the superposition image: [2] p m = p b ⋅ p r p b − p r . {\displaystyle p_{m}={\frac {p_{b}\cdot p_{r}}{p_{b}-p_{r}}}.} For the case when the revealing layer period is longer than the base layer period, the distance between moiré bands is the absolute value computed by the ...
In photography (particularly digital photography), purple fringing (sometimes called PF) is the term for an unfocused purple or magenta "ghost" image on a photograph.This optical aberration is generally most visible as a coloring and lightening of dark edges adjacent to bright areas of broad-spectrum illumination, such as daylight or various types of gas-discharge lamps.
Haidinger fringes are interference fringes formed by the interference of monochromatic and coherent light to form visible dark and bright fringes. Fringe localization is the region of space where fringes with reasonably good contrast are observed. [further explanation needed] Haidinger fringes are fringes localized at infinity.