Device and method for reading multilayer optical disk

Abstract

The invention refers to a device and a method for scanning an optical data carrier (1) by means of a main scanning beam (3) being reflected by the data carrier (1) and being detected by means of a photodetector (10), the data carrier (1) having first and second layers (11,12) to be scanned, the second layer (12) being scanned through the first layer (11), light passing the first layer (11) being shaded dependent on local properties of the first layer (11). An object of the invention is to propose a device having increased performance even for use with multi layer disks (1) having a layer (11) causing light fluctuations on a layer (12) to be scanned, as well as a respective method. According to the invention such device is provided with means (2,7,17) for keeping an output signal (D) of the photodetector (10) independent of variations of shading.

Description

technical field

[0001] The invention relates to a device and a method for reading and / or writing to a dual-layer or multi-layer optical disc, also called scanning of such an optical data carrier. Background technique

[0002] Using multi-layer discs is one possible way to increase the storage capacity of optical discs. Among other methods, phase-change double-layer recording is considered to be one of the most promising techniques for recording optical discs. A dual layer disc is provided with a translucent and partially reflective first layer and a reflective second layer. The second layer is scanned with a beam passing through the first layer. In the case of a partially written first layer or in the case of discs according to the so-called hard disk partition format, the first layer leads to a Light intensity fluctuates. These light fluctuations are also referred to below as shading or shading effects. According to the partitioning format of the hard disk, the partiti...

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