Optical information detection method, optical pickup, and optical information recording and reproducing apparatus

Abstract

An interference-type optical pickup, an optical information detection method, and an optical information recording and reproducing apparatus, which allow easy adjustment of a path difference between two lights, have a high signal amplification effect and are suitable for size reduction of an optical system, are provided. A signal light reflected from an optical disk and a reference light branchedfrom the same light source and guided into detectors without being projected onto the optical disk are caused to interfere with each other on detectors. Detector outputs in four interference states inwhich phase relationships between the reference light and the signal light are different from each other by degrees are simultaneously obtained and calculated. Accordingly, a readout signal RF that is always stable and amplified with high quality is obtained even when an optical path changes due to disk undulations. The four detector outputs are simultaneously obtained by use of four quadrant photo detectors, and are calculated, to thereby also obtain a servo signal.

Description

technical field [0001] The present invention relates to an optical information detection method, for example, to improving the signal-to-noise ratio (S / N) of a reproduced signal in an optical disc device. Background technique [0002] With the commercialization of Blu-ray Disc (BD) using blue semiconductor lasers and high NA objective lenses, the resolution of the optical system has almost reached its limit, and it is expected that the multilayer will continue to increase in size in the future. become a powerful direction. In a multi-layer optical disk, since the amount of detection light from each layer needs to be almost equal, the reflectance from a specific layer has to be reduced. However, since the increase in the capacity of the optical disk requires an increase in the dubbing speed of video and the like, the transfer rate is also increasing. If this is the case, the S / N ratio of the reproduced signal cannot be sufficiently ensured. Therefore, it is necessary to inc...

AI Technical Summary

Problems solved by technology

Furthermore, as another problem, it can be mentioned that the method of adjusting the optical path difference of the two lights is not particularly described, and there are difficulties in practical use.

In Patent Document 2, regarding this problem, it is described that a reference mirror for obtaining interference light is provided separately from the recording film on the disk, but this proposes a disk of a new standard, and does not improve the S / N of the existing disk.

Images