[[picture: siemensstern_beispiel1.png|right|thumb|200px|Auswertebeispiele for the illustration of a Siemens star.]]

With the Siemens star it concerns a test sample of the image processing. The Siemens star is alternating a circle with white and black sectors. Image-processing equipment cannot show this sample perfectly, it develops in the center an indistinct mark, the grey ring in such a way specified. Over the size of the grey ring one determines the resolving power of an optical output device or the focus of an optical input device.

With increasing distance of the center the distance zwischenden white and black bar grows. If the distance is too small, the playback unit shows only a grey surface. If D of the diameters, in units of the overall diameters D, is expressed and n the number of the white and black surfaces, then those-absolute dissolution is l:

l = \ frac {\ pi D} {n}

The illustration right shows example photograph two of optical instruments (e.g. scanners). In the left field the grey circle has a diameter of D = 0,3 D, on the right of D = 0,15 D.

From this follows for the dissolution:

left field: l= \ frac {\ pi \ cdot 0,3 \ cdot D} {36} = 0,03 D

right field: l= \ frac {\ pi \ cdot 0,15 \ cdot D} {36} = 0,01 D

If the fig. 10 cm is large, the optical instrument of the left field 3 mm dissolves, right 1 mm.

To the test of laser scanners the Siemens star was transferred as into the third dimension.

Articles in category "Siemens star"

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