Spherical aberration measurement device and method for optical disk drive

Abstract

The invention relates to a spherical aberration measurement device and method for optical disk drive. The optical disk drive has an objective lens to be driven by a focus actuator with a focus offset for focusing an incident beam onto an optical disk into a spot with a spherical aberration, and a processor to derive a first and a second characteristic from a sensor output signal and obtain a spherical aberration correction value from a pre-determined function, the pre-determined function defining a spherical aberration correction value in dependence on a focus offset difference value. The focus offset difference value is determined from a difference between a second optimal focus offset at which the second characteristic is optimal and a first optimal focus offset at which the first characteristic is optimal. The spherical aberration correction value can be used to achieve a correction to the spherical aberration of the spot.

Description

technical field [0001] The invention relates to a spherical aberration measuring device and its method, in particular to a spherical aberration measuring device and its method for optical drives. Background technique [0002] In the decision method for setting the spherical aberration correction described in the patent application publication number WO 2005 / 034100 A2, it can be applied to the light beam of the data reading and writing device of the optical data carrier, especially for reading and writing Blu-ray Disc and HD- DVD. In the above-mentioned data reading and writing device, the incident light beam generated by it is focused on the optical data carrier to form a reflected light beam, and the spherical aberration correction value can be applied to the incident light beam. When there is relative movement between the incident beam and the optical data carrier, a difference signal is measured, which is the two substantially symmetrical parts of the reflected beam (suc...

AI Technical Summary

Problems solved by technology

[0004] However, the problem with the above known techniques is that the selected combination of objective lens position (focus offset value) and collimator position (spherical aberration correction value) does not always correspond to the best quality

When actually applied to multiple optical discs and multiple optical drives, it is found that the best image quality obtained by measuring one parameter (such as jitter amplitude) is often the best measured by another parameter (such as data jitter (jitter)) The image quality does not correspond, so the combination with better data jitter can retrieve written data satisfactorily, but it has poorer jitter amplitude, i.e., it is less able to recover the position of the data track, or has The combination of better data jitter can retrieve the written data satisfactorily, but has a poor radial error signal, resulting in less stable tracking performance

In addition, sometimes it is not easy to determine the image quality, because the measurement results are not easy to analyze, such as function fitting is difficult

In addition, because the position of the corresponding objective lens must be measured for a large number of collimator positions, this procedure may take considerable time. Although the speed of changing the position of the objective lens can be very fast, it takes some time to change the position of the collimator, so If the change of the collimator position can be reduced, or only one of the positions needs to be changed, such as only changing the position of the objective lens is a better choice

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