JPH0626022B2 - Disk servo device - Google Patents

Description

The present invention relates to a disc servo device used for a disc reproducing device for reading information recorded on a compact disc or the like.

[Conventional technology]

A disc reproducing apparatus for reproducing music information recorded on a compact disc (CD) or the like has a second type.
As shown in the figure, a disc servo device for focusing the laser beam 4 as a detection medium on the recording track of the CD 2 is installed. CD2 is a linear velocity control signal D
It is rotated at a constant linear velocity by a motor 6 controlled by _CLV . The laser light 4 generated by the laser light source 9 installed in the pickup 8 is focused on the track surface of the CD 2 through an optical system including a half mirror 10 and an objective lens 12 to be emitted as a beam, and reflected from the track surface. The light 14 is reflected by the half mirror 10 and converted into an electric signal by the light receiving unit 16 including a light receiving element and the like. In this case, the focus of the laser light 4 is driven by the focus coil 18 by the focus drive signal FD.
Adjustment is performed by changing the position of the objective lens 12 of the optical system, and the movement of the focal position on the track is performed by driving the tracking coil 20 by the tracking drive signal TD.

Then, the detection signal Vi based on the reflected light 14 obtained by the light receiving unit 16 is added to the focus error detection circuit 22 to detect the focus error. The focus error signal FE representing the focus error output from the focus error detection circuit 22 is applied to the zero cross detection circuit 24 for detecting the zero cross point. The zero-cross detection circuit 24 generates a zero-cross signal FZC representing a zero-cross point by comparing the focus error signal FE with its zero level.

This zero-cross signal FZC is used by the focus search circuit 2
6 is used to detect an appropriate focus point. That is, the focus search circuit 26 receives the zero-cross signal FZC according to the focus search command signal FC.
Outputs a focus control signal for controlling the focus point to an appropriate focus point, and the focus control signal generates a drive signal for driving the focus coil 18 together with the focus error signal FE.
8 and becomes the basis of drive output.

The focus driver 28 generates a drive signal FD according to the focus control signal and drives the focus coil 18. As a result, the focus coil 18 is excited, the optical system is operated to a proper focus point, and the laser beam 4 is focused on the track surface of the CD 2.

[Problems to be solved by the invention]

By the way, such focus search control is performed in the preparation stage before starting reproduction, such as when the power is turned on or when the disc is loaded, in the case of the optical disk reproducing apparatus, and when the reproducing operation is started, the focus search is stopped. It is.

However, since the focus error detection circuit 22 generates the focus error signal FE close to 0V even during the normal reproduction operation, the zero-cross detection circuit 24 detects the zero-cross point of the focus error signal FE and the zero-cross signal as the detection signal. It outputs FZC. Since the zero-cross signal FZC is a pulse signal that switches according to the zero-cross point, it has a sharp level change, and this appears as noise in the EFM reproducing system and the like, which causes a data reading error. .

Therefore, it is an object of the present invention to provide a disk servo device in which the operation of the zero-cross detection circuit is restricted to prevent the zero-cross signal from becoming noise.

[Means for solving problems]

As shown in FIG. 1, the disk servo device of the present invention searches a focus point and outputs a search signal representing the focus search, and a zero-cross detection for detecting a zero-cross point of the focus error signal. A disk servo device including a circuit, wherein the zero-cross detection circuit is operated only during the focus search period in response to the search signal generated by the focus search circuit, and the focus error signal of the focus error signal is generated only during this operation period. The feature is that the zero-cross point is detected.

[Work]

In the disk servo device of the present invention, the operation of the zero-cross detection circuit 30 is performed only during focus search, and the generation of the zero-cross signal FZC in the reproducing state is prevented.
The influence of the zero-cross signal FZC on the reproduction state is avoided.

〔Example〕

FIG. 1 shows an embodiment of the disk servo device of the present invention.

The zero-cross detection circuit 30 is configured to detect the zero-cross point of the focus error signal FE from the focus error detection circuit 22 and to switch its operation arbitrarily from the outside, for example, the zero-cross point level and the focus error signal FE. And a comparator capable of switching the operation for comparing The switch 32 is an operation switching unit that is configured by a transistor or the like for cutting off the supply of the operating current to the zero-cross detection circuit 30 and switching its operation, and can be configured as an internal circuit or an external circuit of the zero-cross detection circuit 30.

The focus search circuit 34 starts its operation by a focus search command signal FC given from the outside when the power is turned on or the disc is loaded, and the search signal FS indicating the start and end of the operation is generated. Output.

Therefore, the search signal FS is applied to the zero cross detection circuit 30.
Used as the operation switching signal of the zero cross detection circuit 30.
This operation is performed only during the focus search period.

By doing so, the zero-cross detection circuit 30 operates during the focus search period, and the zero-cross signal FZC necessary for the focus search is obtained, and the operation of the zero-cross detection circuit 30 is stopped during the other period, that is, in the normal reproduction state. Therefore, even if the focus error signal FE arrives, the zero cross signal FZC is not generated. Therefore, the influence of the zero-cross signal FZC as noise on the EFM reproducing system and the like during reproduction can be avoided, and proper data reproduction can be performed.

〔The invention's effect〕

As described above, according to the present invention, since the zero-cross detection circuit is operated only during the focus search period, it is possible to prevent the zero-cross signal from becoming noise and to avoid the influence of the zero-cross signal on the data reading, thereby reducing the data reading error. Can be reliably prevented.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a disk servo device of the present invention, and FIG. 2 is a block diagram showing a general disk servo device. 30 ... Zero cross detection circuit 34 ... Focus search circuit

Claims (1)

[Claims] 1. A disk servo device comprising: a focus search circuit that searches for a focus point and outputs a search signal representing the focus search; and a zero-cross detection circuit that detects a zero-cross point of a focus error signal. According to the search signal generated by the focus search circuit, the zero-cross detection circuit is operated only during the focus search period, and the zero-cross point of the focus error signal is detected only during this operation period. Characteristic disk servo device.