Focusing method of oblique incidence multilayer optical disk

Abstract

The invention is a multilayer CD inclinedly incident focusing method, and the related focusing device makes the collimated laser from a laser device inclinedly reach the CD surface after focused by a lens, then reflected by the CD information recording surface and image after focused by the other lens, then pass through a cylindrical mirror and finally form a defocusing signal by a six-quadrant photoelectric detector receiving image difference; and the method includes the steps of: (1) moving the CD to the laser focus for rough focusing; (2) making the laser form foculae on the four-quadrant surfaces of the photoelectric detector through the focusing device; (3) supposing the defocusing signal T is the ratio of the difference between the sum of the first- and third- quadrant light currents and that of the second- and fourth- quadrant light currents of the photoelectric detector to the total light current; (4) changing the positions of the two lenses by a 2D moment device for controlling their positions by T to reduce the defocusing quantity; (5) repeating the steps (2)-(4) until realizing the accurate focusing illumination of the laser foculae on the CD information recording surface.

Description

technical field [0001] The invention relates to optical storage technology, in particular to a focus adjustment technology for multi-layer optical discs when optical storage is read and written. Background technique [0002] High-density and large-capacity data storage is a key research field in information science, one of the important supporting conditions for the rapid development of information society and knowledge economy, and plays a very important role in national economic construction and modern science and technology. Today's optical data storage technologies such as CD and DVD discs have been widely used in audio-visual and computer data storage fields. People are trying to further increase the storage density of optical disc storage, such as the use of large numerical aperture objective lens or the use of shorter wavelength light source. However, today's optical disc storage areal density is close to the spatial resolution limit caused by the electromagnetic wav...

AI Technical Summary

Problems solved by technology

The existing optical disc focusing technology basically adopts the method of vertical incidence and reflection. In the case of multi-layer storage, each storage layer will reflect information at the same time. The information has the same direction and similar intensity, so it is difficult to distinguish them.

Therefore, the existing optical disc focusing technology cannot be used for multi-layer storage

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