Siemens star

The Siemens & Halske AG, now Siemens, has developed various methods to check the optical quality of all lenses for Siemens cine-film cameras, including the Siemens Half Star, Siemens star and Siemensreflexprüfmethode. When Siemens star is a test pattern, a circle with alternating white and black sectors. An image processing unit can not play perfectly this pattern, it arises in the middle of a blur spot, the so-called gray ring. About the size of the gray ring to determine the resolution of an optical output device or the focus of an optical input device.

With increasing distance from the center of the distance between the white and black bars grows. If the distance is too small, the playback device plays only a gray area. D is the diameter and n is the number of the white and black areas, it is the absolute resolution L:

Example

The figure shows sample recordings of two optical instruments ( eg scanner ) from a 18- rayed Siemens star, that is, there are 18 bright and 18 dark areas and thus n = 36 In the left section of the gray circle has a diameter of d = 0.3 D, right d = 0.15 D.

It follows for the resolution:

If the image is 10 cm tall, solves the optical instrument of the left part of the image to 2.6 mm, right 1.3 mm.

Böhlerstern

For testing of laser scanners, the Siemens star was transmitted as Böhlerstern in the third dimension.