Polygram Gmbh

Polygram International Holding B.v.

Dieter Schulz

Harald Ahrens

In a method of aligning objects and in particular, of aligning optically readable disc-shaped information carrier. The objects are preferably optically scanned line-by-line in a direction transverse to their direction of movement. A reference picture line with an optically characteristic picture content is detected to allow alignment relative to known positions. To detect the reference picture line, the picture contents of all the picture lines are compared with each other and the corresponding correlation coefficients are determined. The reference picture line is that picture line whose picture content correlates least with the picture content of any other picture line.

Method of aligning objects by detecting a reference picture line therein

A centering device for the manufacture of a center hole in disks, particularly metallized video disks with spiral information tracks and an information-free center, employs a measuring head for the emission of a light beam onto the disk surface. The light beam is precisely situated at a boundary between the information portion and the information-free portion of the disk during a full disk revolution (a transition criterion) and that said criterion is evaluated for the identification of the center. An electronic control circuit is provided for the control of the displacements required for the measuring head and of the disk centered in planes which are parallel relative to one another.

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Hanover, Germany

Dieter Schulz