KR100850920B1 - Tracking Servo Control Apparatus and Method of Optical Disk - Google Patents

Abstract

The present invention provides a normal tracking servo by using a DPD block without using a DPP block when playing a CD-based optical disc having poor playback characteristics in a playback apparatus capable of playing both an CD-based optical disc and a DVD-based optical disc. An object of the present invention is to provide a tracking servo control apparatus and a control method of an optical disc. To this end, the apparatus of the present invention is a device for performing a tracking servo by switching between a 1 beam tracking method and a 3 beam tracking method according to the type of the loaded optical disk, the characteristic of detecting the reproduction characteristic of the 3 beam tracking optical disk And detection means and control means for controlling the three-beam tracking optical disc to track by the one-beam tracking method in accordance with the detection result of the characteristic detection means.

Tracking Error, Tracking Servo, Differential Phase Detection (DPD) Method, Differential Push-Pull Method

Description

Tracking Servo Control Apparatus and Control Method for Optical Disks {Tracking Servo Control Apparatus and Method of Optical Disk}             

1 is a schematic block diagram of an optical disc recording / reproducing apparatus to which the present invention is applied;

2 is a block diagram showing a conventional tracking servo controller;

3 is a flowchart of a conventional tracking servo control method;

4 is a view for explaining a general differential push-pull (DPP) method,

5 is a waveform measured when amplifying a low tracking level by the DPP method in some CD-based optical discs;

6 is a waveform measured to explain an offset of a tracking error in an optical disc of some CD series;

7 is a characteristic diagram of a tracking level change by the DPP method in a conventional CD-type optical disc;

8 is a characteristic diagram for explaining the principle of the DPD method used in DVD;

9 is a block diagram showing a tracking servo control device according to a first embodiment of the present invention;

10 is a block diagram showing a tracking servo control apparatus according to a second embodiment of the present invention;

11 is a block diagram showing a tracking servo control device according to a third embodiment of the present invention;

12 is a flowchart of a tracking servo control method according to the present invention;

12 is a flowchart illustrating a modification of the tracking servo control method according to the present invention.

※ Explanation of code for main part of drawing

10 optical disc 11: spindle motor

20: optical pickup 30a: digital recording signal processing unit

30b: digital reproduction signal processor 40: channel bit encoder

41: optical drive unit 50: high frequency (R / F) signal processing unit

  51: level detector 60: servo unit

62: DPD block 64: DPP block

66: switching means 70: drive unit

80: microcomputer 100: reflectance detection unit

110: offset detection unit 120: switching means

The present invention relates to an optical disc recording / playback apparatus, and more particularly, to an apparatus and method for controlling a tracking servo of an optical disc in a composite product capable of playing both an optical disc of a CD (Compact Disk) series and an optical disc of a DVD series. .

In general, the configuration of a composite apparatus capable of recording and playing back CD-based optical discs, such as CD-ROMs and recordable optical discs (e.g., CD-R, CD-WR), and playback of DVD-based optical discs, is illustrated in FIG. As shown in FIG. 1. The apparatus of FIG. 1 includes a digital recording signal processor 30a for adding an error correction code (ECC) or the like to input digital data to convert it into a recording format; A channel bit encoder (40) for reconverting the data converted into the recording format into a bitstream; An optical driver 41 for outputting a light quantity driving signal according to the input signal; An optical pickup (20) for recording a signal on the optical disc (10) in accordance with the light quantity driving signal and for detecting a recording signal from the recording surface; An R / F unit 50 for filtering the signal detected by the optical pickup 20 to output a binary signal; A level detector 51 for detecting the level of the signal reflected by the recording light (the level of the RF signal); A drive unit 70 for driving a spindle motor (not shown) for transferring the optical pickup 20 and a spindle motor 11 for rotationally driving the optical disc 10; A servo unit 60 for controlling the driving of the drive unit 70 from the tracking error (T.E) and focus error (F.E) signals of the optical pickup 20 and the rotational speed of the optical disc 10; A digital reproduction signal processing unit (30b) for restoring the binary signal to original data with its clock synchronized with the binary signal; And a microcomputer 80 for controlling data recording and data reproducing operations for the optical disc 10.                         

In the above-described optical disc recording and reproducing apparatus, the reproduction tracking servo control apparatus is a main element (A to D) of the light receiving element PD in one beam for the reproduction tracking servo of the DVD-based optical disc as shown in FIG. A DPD (Differential Phase Detect) block 62 which detects a tracking error by using the amount of light received by the control unit; Main beams (A-D) and sub-elements (E-G) of the light-receiving element PD with three beams for reproducing tracking servos of CD-based optical discs such as CD-ROM, CD-R, CD-RW, etc. A DPP (Differential Push-Pull) block 64 for detecting a tracking error by using the amount of light received at the control unit; According to the type of optical disk, the switching means 66 outputs one of the outputs of the DPD block 62 and the DPP block 64 as a tracking error signal under the control of the microcomputer 80.

In the optical disk device configured as described above, when the optical disk 10 is loaded as shown in FIG. 3, the operation of determining the type of the optical disk is performed first (step S10). When the loaded optical disc 10 is a CD-based optical disc such as CD-R, CD-RW, CD-ROM, the microcomputer 80 selects the output of the DPP block 64 by the switching means 66 as a tracking error. (Steps S12 to S14), on the other hand, when the optical disc 10 is a DVD-based optical disc, the microcomputer 80 controls the switching means 66 to select the output of the DPD block 62 as the tracking error. Subsequently (steps S12, S18, S20), the reproduction tracking servo of the optical disc 10 is controlled (step S16).

As shown in FIG. 4, the DPP method calculates a tracking error using the received signal from the four-split light receiving elements A to D of the main beam and the received signal from the two-split light receiving elements E to G of the sub-beam. do. By the way, the optical reflectance is lowered depending on the pit formation state (recording state) and the medium of the optical disk, so that the signal level of the tracking error may drop significantly. In this case, when the signal level is low (see FIG. 5A), increasing the amplification gain to increase the signal level also increases the noise included in the signal (see FIG. 5B), which causes anxiety of the tracking servo. In addition, the DPP method moves to the center level when there is an offset in the tracking error signal (FIG. 6A is an offset in the tracking error signal in the DPP method, and FIG. 6B is an offset does not occur). Offset adjustment 64A, 64B is performed to make the offset. When this offset is a certain amount or more, it is not adjusted to the center level, which causes a servo fail.

In addition, as shown in Fig. 7, in some optical discs, since the level of the tracking error signal is significantly reduced depending on the pit shape of the disc, it is sometimes difficult to drive and maintain the tracking servo by the DPP method.

Accordingly, the present invention has been made to solve the above problems, and in the reproducing apparatus capable of reproducing both CD-based optical discs and DVD-based optical discs, a DPP block is used for reproducing a CD-based optical disc with poor reproduction characteristics. It is an object of the present invention to provide a tracking servo control apparatus and a control method for an optical disc, which can maintain a normal tracking servo by using a DPD block.

In the tracking servo control apparatus for an optical disc according to the present invention for achieving the above object, in the apparatus for performing a tracking servo by switching the one-beam tracking method and the three-beam tracking method according to the type of the loaded optical disk, the three-beam Characteristic detection means for detecting a reproduction characteristic of the tracking optical disc; And controlling means for tracking the optical disc of the three-beam tracking method by the one-beam tracking method according to the detection result of the characteristic detecting means.

Here, the characteristic detecting means includes a light reflecting amount detecting means for detecting a light reflecting amount reflected from the optical disk as a reproduction characteristic, and the control means is a one beam tracking method if the detected amount of the light reflecting amount detecting means is below a predetermined value. It is preferable to control tracking by the.

The characteristic detecting means includes an offset detecting means for detecting an offset in the three-beam tracking method as a reproduction characteristic, and the control means is a one-beam tracking method if the offset detection value of the offset detecting means is a predetermined value or more. It is preferable to control tracking by the.

The control means may include switching means for selectively outputting either one of the one-beam tracking method and the three-beam tracking method according to the detection result of the characteristic detection means, or the detection of the characteristic detection means. According to the result, it is preferable that the light receiving element is configured to include a switching means for switching the switching so as to be input to either one of the one-beam tracking method and the three-beam tracking method.

In addition, the tracking servo control method for an optical disc according to the present invention for achieving the above object, the first step of selecting and setting any one of the one-beam tracking method and the three-beam tracking method by determining the type of the loaded optical disk; ; A second step of testing a reproduction characteristic of the optical disc when the three beam tracking method is set; And a third step of switching and setting the tracking method to the 1 beam tracking method when the tested reproduction characteristic is poor.

In addition, a tracking servo control method for an optical disc according to the present invention includes a first step of determining a type of a loaded optical disc to select and set one of a corresponding one beam tracking method and a three beam tracking method to perform tracking control; A second step of continuously checking the reproduction characteristic of the optical disc during the tracking control when the three beam tracking method is set; And if the checked reproduction characteristic is poor, a third step of switching the tracking method to the 1 beam tracking method and continuing the tracking control.

Best Mode for Carrying Out the Invention Preferred embodiments of the tracking servo control apparatus and control method for an optical disc according to the present invention will be described in detail with reference to the accompanying drawings.

The present invention provides a composite device capable of recording and reproducing a CD-based optical disc such as a CD-ROM and a recordable optical disc (e.g., CD-R, CD-WR) and the like, and reproducing a DVD-based optical disc. When the signal level of the tracking error signal due to the DPP method drops considerably or a certain amount of offset occurs due to the recording pit shape and the medium of the series optical disc, the optical disc of the corresponding CD series is determined by the DPD method instead of the DPP method. Tracking control. In the DPD method, as shown in FIG. 8, the phase difference between the light receiving signals [(A, C) and (B, D)] received by the main elements A to D of the light receiving element PD is compared. Since the tracking error signal is obtained only by the beam, it is not affected by the weak tracking signal level or excessive offset.

9 is a block diagram illustrating a tracking servo control apparatus according to a first embodiment of the present invention. The same components as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the present embodiment, when the optical disc 10 is a CD series, the amount of light reflection reflected from the optical disc 10 based on the light reception signal received by the main elements A to D of the light receiving element PD in the reflection amount detection unit 100 is calculated. The detection signal is provided to the microcomputer 80. The microcomputer 80 blocks the tracking signal by the DPP block 64 and outputs the tracking signal by the DPD block 62 when the detected amount of light reflection is less than or equal to a predetermined value. That is, to prevent tracking servo errors that may occur when the tracking signal level is too low when tracking by the DPP method.

10 is a block diagram showing a tracking servo control apparatus according to a second embodiment of the present invention. In the present embodiment, when the optical disc 10 is a CD series, the offset detector 100 detects an offset in the DPP block and provides the detection signal to the microcomputer 80. The microcomputer 80 blocks the tracking signal by the DPP block 64 and outputs the tracking signal by the DPD block 62 when the detected offset is greater than or equal to a predetermined value. That is, to prevent tracking servo errors that may occur when the offset of the tracking signal is too high when tracking by the DPP method.

Although not shown here, the present invention merges FIGS. 9 and 10 (i.e., by installing the offset detector of FIG. 10 in the circuit of FIG. 9), so that the amount of light reflection from the optical disk and the DPP block for the CD-based optical disk is reduced. In consideration of both the offsets, the controller may be configured to select either the tracking servo by the DPP block or the tracking servo by the DPD block.

11 is a block diagram showing a tracking servo control apparatus according to a third embodiment of the present invention. In the present embodiment, when the optical disc 10 is a CD series, the amount of light reflection reflected from the optical disc 10 based on the light reception signal received by the main elements A to D of the light receiving element PD in the reflection amount detection unit 100 is calculated. The detection signal is provided to the microcomputer 80. In addition, the offset detection unit 100 detects the offset in the DPP block and provides the detection signal to the microcomputer 80. The microcomputer 80 blocks the light receiving signal input to the DPP block 64 when the detected light reflection amount is equal to or less than a predetermined predetermined value or the detected offset is equal to or larger than a predetermined predetermined value and the light receiving signal is a DPD block ( The switching means 120 is controlled to be input only to 62. Thus, the tracking signal by the DPD block 62 is used as the tracking servo control signal. That is, to prevent the tracking servo error that may occur when the tracking signal level is too low or when the offset of the tracking signal is too high when performing tracking by the DPP method.

Next, a tracking servo control method for an optical disc according to the present invention will be described with reference to the flowchart of FIG.

First, when the optical disc 10 is inserted and seated, the microcomputer 80 determines the type of the optical disc by a conventional disc determination method (step S10), and checks whether the corresponding optical disc 10 is a CD-based optical disc (step S10). S12).

If it is confirmed in the step S12 that the CD-based optical disk is not (ie, the DVD-based optical disk), the microcomputer 80 controls the switching means 66 or 120 to generate a tracking signal by the DPD method. (Step S14), and controls to perform tracking control by this set DPD method (step S16).

On the other hand, when it is confirmed in step S12 that the optical disk 10 is a CD-based optical disk, the switching means 66 or 120 is controlled to generate a tracking signal by the DPP method (step S14). Thereafter, the reproduction test of the optical disc 10 is performed by the DPP method of the optical disc 10 (step 100), and it is confirmed whether the reproduction characteristics are good (step S110).

Here, the reproduction characteristic is at least one selected from the light reflection amount of the optical disc and the offset amount in the three beam tracking method. When the reproduction characteristic is a light reflection amount, in step S110, it is determined whether the detected light reflection amount is equal to or less than a predetermined predetermined amount, and when it is higher than that, the reproduction characteristic is good, and when it is lower than that, the reproduction characteristic is poor. In the case where the reproduction characteristic is an offset, in step S110, it is determined whether the detected offset is a predetermined amount or more, and when it is less than or equal, the reproduction characteristic is good, and when the reproduction characteristic is higher, the reproduction characteristic is poor.                     

If it is determined in step S110 that the reproduction characteristics are good, the microcomputer 80 controls to perform tracking control by the set DPP method (step S16).

On the other hand, if it is determined in step S110 that the reproduction characteristic is poor, the microcomputer 80 changes the tracking method to the DPD method (step S20), and controls to perform tracking control by the changed DPD method. (Step S16).

On the other hand, in the above-described embodiment of FIG. 12, when the optical disk is a CD-based optical disk when the optical disk is loaded, the tracking signal is generated by either the DPP method or the DPD method according to the reproduction characteristics thereof. As shown in the following example, in the case of a CD-based optical disc, when the reproducing characteristic is judged to be good during the test of step S100, and the reproducing characteristic of the optical disc becomes poor during tracking servo for generating a tracking signal by the DPP method, You may control to generate a tracking signal by DPD method immediately.

On the other hand, the present invention is not limited to the above-described typical preferred embodiments, but can be carried out in various ways without departing from the gist of the present invention, various modifications, alterations, substitutions or additions are common in the art Those who have knowledge will easily understand. If the implementation by such improvement, change, replacement or addition falls within the scope of the appended claims, the technical idea should also be regarded as belonging to the present invention.

 The tracking servo control apparatus and control method for an optical disc according to the present invention as described above can maintain a normal tracking servo by using a DPD block without using a DPP block when playing an optical disc of a CD series having poor reproduction characteristics. It is a useful invention.

Claims (10)

An apparatus for performing a tracking servo by switching between a 1 beam tracking method and a 3 beam tracking method according to a loaded optical disc, Characteristic detecting means for detecting a reproduction characteristic of the three-beam tracking optical disc; And controlling means for tracking the three-beam tracking optical disc by one beam tracking according to the detection result of the characteristic detecting means. The characteristic detecting means comprises an offset detecting means for detecting an offset in the three beam tracking method as a reproduction characteristic, And the control means controls tracking by the one beam tracking method if the offset detection value of the offset detection means is equal to or greater than a predetermined value. delete delete The method of claim 1, And the control means includes switching means for selectively outputting either one of the one-beam tracking method and the three-beam tracking method according to the detection result of the characteristic detection means. . The method of claim 1, And the control means includes switching means for switching the received signal of the light receiving element to be switched to either one of the one-beam tracking method and the three-beam tracking method according to the detection result of the characteristic detecting means. Tracking servo control. Determining a type of the loaded optical disc and selecting and setting one of a one beam tracking method and a three beam tracking method; A second step of testing a reproduction characteristic of the optical disc when the three beam tracking method is set; And a third step of setting and switching the tracking method to the 1 beam tracking method when the tested reproduction characteristic is poor. And the reproduction characteristic is at least one selected from an amount of light reflection of the optical disc and an offset amount in the three beam tracking method. delete delete The method of claim 6, And the reproduction characteristic defect is judged whether or not the light reflection amount is equal to or less than a predetermined value when the reproduction characteristic is an amount of light reflection of the optical disc. The method of claim 6, And when the reproduction characteristic is an offset amount of the optical disc, the reproduction characteristic defect is determined by whether or not the offset amount is a predetermined value or more.

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