Tracking balance adjustment device

Abstract

A tracking balance adjustment device carries out a balance adjustment, when laser beams emitted from a laser element are caused to track a track on the optical disk, to bring the DC component of a tracking error signal equal to a preset DC reference value by obtaining two photodetection signals opposite to each other in phase that represent a deviation in the tracking based on return beams of the laser beams from the optical disk and carrying out the tracking servo control based on the tracking error signal obtained from the difference between the two photodetection signals. The tracking balance adjustment device has a first amplifier operable to amplify one of the photodetection signals, a second amplifier operable to amplify the other photodetection signal, and a tracking balance adjustment unit operable to adjust the offset of the first amplifier so as to bring the DC component of the output of the first amplifier equal to the DC reference value and to adjust the offset of the second amplifier so as to bring the DC component of the output of the second amplifier equal to the DC reference value.

Description

technical field [0001] The invention relates to a tracking balance adjusting device. Background technique [0002] When an optical disc device reads out information on a target track recorded on an optical disc, it usually performs tracking servo control based on a tracking error signal to make the laser light emitted from the laser element provided in the optical pickup track (follow) the target track. . [0003] As a method for generating a tracking error signal, a three-beam method will be described as an example. In an optical pickup using a three-beam method, such as Figure 10 As shown, the laser beam is separated into three beams, the main beam and the sub-beams 1 and 2, and emitted. In addition, the main beam is a beam for reading out information recorded on the target track. In addition, the sub-beams 1 and 2 are irradiated to positions that are point-symmetrical to the main beam, respectively, and a tracking error signal is generated by utilizing the difference ...

AI Technical Summary

Problems solved by technology

In addition, in the tracking balance adjustment unit 90, a complicated logic circuit for switching ON / OFF of the selection switches provided on the respective resistors of the ladder resistors 611 and 711 is required based on the DC component of the tracking error signal.

[0013] Therefore, in the case of integrating the resistor ladders 611, 711 or selection switch switching circuits using a CMOS process to form an LSI on one chip, since the resistor ladders 611, 711 have a plurality of resistors or ON / OFF of the selection switches, Due to the influence of the complex logic circuit for OFF switching, the scale of this LSI circuit increases, so there is a problem that integration is difficult

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