KR100628198B1 - Method and apparatus for controlling record/play of optical record media - Google Patents

Abstract

A method and apparatus for controlling recording and reproducing of an optical record carrier, and in particular, generates RF, FE, TE, and TG signals from an electrical signal proportional to the amount of reflected light output from each photodetecting element of the photodetector, wherein the RF, FE Detects each DC level from the TE and TG signals, and then controls the preset reference level, and then detects the abnormality of each photodetecting device from the RF, FE, TE, and TG signals with the DC level adjusted. By correcting only the signal of the photodetecting element, not only can the phase difference offset caused by the disk itself or the like be efficiently removed, but also the offset due to the cross correlation between the RF, FE, TE, and TG can be removed.

Photo detector, offset correction

Description

Method and apparatus for controlling recording and reproducing of an optical recording medium {Method and apparatus for controlling record / play of optical record media}

1 is a view showing an example of a general photo detector

2 is a block diagram of an optical recording medium recording and reproducing control apparatus according to the present invention;

3 is a detailed block diagram of the offset remover of FIG. 2;

Explanation of symbols for the main parts of the drawings

101: optical disk 102: optical pickup

103: RF and servo error generation unit 104: offset removal unit

105: determination unit 106: servo control unit

107: focus / tracking servo driver

201: DC level detection and correction unit 202: abnormality detection unit

203 to 206: subtractor

TECHNICAL FIELD The present invention relates to recording and reproducing of an optical recording medium, and more particularly, to a method and apparatus for controlling recording and reproducing of an optical recording medium.                         

As the storage capacity of existing CD-ROM titles has reached the limit, digital versatile discs (DVDs) have been in the spotlight as new storage media. The DVD is not much different from the CD in terms of implementation. That is, the data is recognized on the same principle as a CD that recognizes data of 0 and 1 at an angle reflected by a laser. The difference is that the data storage is smaller than the CD.

Also, like a CD, a DVD is a read-only ROM type (e.g., DVD-ROM), a once-writable Worm type (e.g., DVD-R), and repetitive, depending on whether or not repeat recording is possible. It is largely divided into rewritable types (eg, DVD-RW, DVD-RAM, DVD + RW) that can be recorded.

At this time, in the case of the rewritable disc, the recording medium is usually formed of a phase change material. Therefore, the light focused at the optical head is converted to heat, and this heat changes the state of the phase change recording medium so that the reflection amount is changed, thereby forming marks on the phase change type disk to record the pits.

In an apparatus for recording and reproducing an optical disc such as a CD or a DVD, the optical pickup causes the light beam focused on the objective lens to be placed on the signal track of the optical disc, and also focuses the light reflected from the signal recording surface back to the objective lens and then focus It enters the photo detector for detection of the error signal and the tracking error signal. The photo detector consists of a plurality of photo detectors, and outputs an electrical signal proportional to the amount of light obtained from each photo detector.

For example, the photodetector is composed of four photodetecting elements that are specifically divided, i.e., quadrature, in the signal track direction (or tangential direction) and radial direction of the optical disk as shown in FIG. It is assumed that the electrical signals proportional to the amounts of light obtained by the respective photodetecting elements are A, B, C, and D.

Then, the RF signal required for data reproduction can be obtained by (A + B + C + D) the electrical signal output from the photo detector, and the tracking error (TE) signal used for tracking servo is output from the photo detector. The phase difference of the electrical signal in the radial direction can be detected, that is, obtained by (A + D)-(B + C). Further, the focus error (FE) signal used for the focus servo can be obtained by (A + C)-(B + D) the electrical signal output from the photodetector.

At this time, an essential condition for a stable servo is accurate and unbiased servo error. In order to generate this, it is necessary to generate an accurate servo error signal without offset from the optical pickup.

However, even when the light beam is accurately positioned at the track center, the amount of light detected by each photodetecting element of the photodetector may vary due to the mechanical problem of the optical pickup, the problem of the optical disk itself, and other causes. As a result, an offset may occur in the servo error signal even if the light beam is accurately positioned at the track center. In other words, since a wrong signal is provided to the portion generating the servo error, a phase difference offset occurs in the generated servo error signal.

Therefore, conventionally, a method of giving a slight delay in order to remove a phase difference offset of A, B, C, and D has been proposed. However, the amount of delay has to be determined according to the type and condition of the optical disc, which is cumbersome and difficult.

In addition, the generated servo error signal is limited to FE and TE. For example, if an offset occurs in the TE side, the offset is removed by adjusting only A and D or only B and C. In this case, it is not known which photodetecting device has a problem.

As described above, in the related art, the offset due to the cross correlation between FE and TE cannot be removed, and there is a problem in that all the degrees of freedom of A, B, C, and D cannot be included and all offset cases cannot be considered.

The present invention is to solve the above problems, an object of the present invention is to detect the phase difference in the tangential direction and then apply it to the existing RF, FE, TE signal in the radial direction for each split element of the photo detector The present invention provides a method and apparatus for controlling recording and reproducing of an optical recording medium for detecting and correcting an abnormality.

In the recording and reproducing control method of the optical recording medium of the present invention for achieving the above object, an RF signal, a focus error by receiving an electrical signal proportional to the amount of reflected light output from each of the optical detection elements of the optical detector in the optical pickup Generating a (FE) signal, a tracking error (TE) signal in a radial direction, and a tracking error (TG) signal in a tangential direction, and detecting respective DC levels from the RF, FE, TE, and TG signals. Controlling to the set reference level, and detecting the abnormality of each photodetecting device from the RF, FE, TE, and TG signals whose DC level is adjusted in this step, and correcting the signal of the photodetecting device with the abnormality. It is characterized by comprising.

An apparatus for controlling recording and reproducing of an optical record carrier according to the present invention receives an RF signal, a focus error (FE) signal, and a radial direction by receiving an electrical signal proportional to the amount of reflected light output from each of the optical detectors of the optical detector in the optical pickup. An RF and servo error generator for generating a tracking error (TE) signal and a tracking error (TG) signal in a tangential direction, and a predetermined reference after detecting respective DC levels from the RF, FE, TE, and TG signals. Level detection and correction unit for controlling the level, and abnormality detection for detecting the abnormality of each photodetecting element from the RF, FE, TE, and TG signals whose DC level is adjusted, and correcting the signal of the photodetecting element with the abnormality. And a correction unit.

Other objects, features and advantages of the present invention will become apparent from the following detailed description of embodiments taken in conjunction with the accompanying drawings.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The present invention obtains a tracking error signal (hereinafter, referred to as TG) in the tangential direction from the electrical signals A, B, C, and D obtained by the photodetector, and then tracks the TG signal and the existing RF, FE, and radial error. The signal (hereinafter, referred to as TE) is used to efficiently eliminate offsets caused by the disk itself.

To this end, first, RF, FE, TE, TG from the electrical signals A, B, C, D output from the photodetector as shown in FIG. 1 are obtained as shown in Equations 1 to 4 below.

RF = (A + B + C + D)

FE = (A + C)-(B + D)

TE = (A + D)-(B + C)

TG = (A + B)-(C + D)

In addition, when the above Equations 1 to 4 are expressed as determinants, Equation 5 below.

Herein, assuming that A, B, C, and D are all independent from each other, A, B, C, and D may be calculated as in Equations 6 to 9 below.

A = 1/4 + (RF + FE + TE + TG)

B = 1/4 + (RF-FE + TE + TG)

C = 1/4 + (RF-FE-TE + TG)

D = 1/4 + (RF + FE + TE-TG)

If there is no phase difference offset, the FE, TE, and TG values have zero for a given reference level (ie, DC level). That is, when the above Equations 1 to 4 are combined, the values of A, B, C, and D are the same. However, in the conventional methods that do not consider TG, the same values are not necessarily obtained because of the high degree of freedom of A, B, C, and D.

Thus, the present invention uses this feature to eliminate offsets occurring in the servo error signal.

Fig. 2 is a block diagram of an optical recording medium recording and reproducing apparatus for offset cancellation according to the present invention.

Referring to Fig. 2, an optical disk 101 capable of recording and reproducing data, and an optical pickup 102 for detecting the amount of reflected light from the optical disk 101 and outputting electrical signals A, B, C, and D in proportion thereto. RF and servo error generation unit 103 for generating servo error signals such as RF, TE, FE, and TG by using electrical signals A, B, C, and D output from the optical pickup 102. An offset eliminator that receives the RF, FE, TE, and TG signals generated by the servo error generator 103 to determine whether there is an abnormality of an electrical signal output from each photodetector, and removes a phase difference offset of each servo error signal ( 104), a focus servo required for servo control by receiving the FE and TE signals generated by the determination unit 105 and the RF and servo error generation unit 103 to check whether the offset is removed by the offset removing unit 104; A servo control unit 106 for generating a drive signal and a tracking servo drive signal, respectively; Group comprises a focusing / tracking servo driving unit 107 for driving the focus actuator and the tracking actuator in a focus servo drive signal and a tracking servo drive signal in the servo control section 106, the optical pickup 102.

FIG. 3 is a detailed block diagram of the RF and servo error generator 103 and the offset remover 104 of FIG. 2.

In the present invention configured as described above, the electrical signals A, B, C, and D which are proportional to the amount of reflected light detected by the respective photodetecting elements of the photodetector in the optical pickup 102 are output to the RF and servo error generating unit 103. . The RF and servo error generator 103 receives the electrical signals A, B, C, and D, and generates RF, FE, TE, and TG signals in a determinant as shown in Equation 5, and offset offset unit 104. ) Is output to the DC level detection unit 201. Here, the determinant of Equation 5 is an embodiment of the present invention, and may generate the above-described servo error signals through another method, that is, the calculation as in Equations 1 to 4 described above.

In addition, the RF signal is output for data reproduction, and the FE and TE signals are output to the servo controller 106 for servo control.

At this time, since the A, B, C, and D signals are high frequency, it is difficult to detect the DC level carried in each signal. As a result, it is difficult to compare the levels of the signals for offset detection, and thus the A, B, C, and D signals are output to the DC level detection and correction unit 201 through the RF and servo error generation unit 103.

The DC level detection and correction unit 201 performs low pass filtering on the servo error signals, that is, the RF, FE, TE, and TG signals, respectively, to remove the AC component included in each servo error signal, and to apply the servo error signal. Detect the included DC level. The detected DC level is compared with a preset reference level, that is, a reference DC level.

In this case, in the case of the servo error signal in which the detected DC level is out of the reference DC level, the DC level of the detected servo error signal is controlled to be the reference level and then output to the abnormality detecting unit 202. That is, the DC level detection and correction unit 201 corrects low frequency components of the servo error signal that deviate from the reference DC level.

At this time, the DC level detection and correction unit 201 sets the pass band of the low pass filter LPF so that the true servo error signal is not filtered.

Since the signal output to the abnormality detection unit 202 is a low frequency component corrected signal, the servo error signal input to the DC level detection and correction unit 201 and the DC level detection and correction unit 201 are output. The servo error signal may be different. Accordingly, in the present invention, as shown in FIG. 3, the servo error signal input to the DC level detection and correction unit 201 is represented by RF, FE, TE, and TG, and is output from the DC level detection and correction unit 201. The servo error signal is indicated by RF ', FE', TE ', and TG'.

The abnormality detecting unit 202 detects the abnormality of each photodetecting device from the RF ', FE', TE ', and TG' signals output from the DC level detecting and correcting unit 201.

That is, the abnormality detection unit 202 receives RF ', FE', TE ', and TG' signals output from the DC level detection and correction unit 201 to obtain A ', B', C ', and D'. If this is expressed as a determinant, Equation 10 below.                     

Here, the determinant of Equation 10 is an embodiment of the present invention, and the above-mentioned servo error signals A ', B', C ', and D' may also be obtained through another method, that is, the operation as described in Equations 6 to 9 described above. Can be generated.

At this time, if there is no abnormality in the signal output from each of the photodetecting elements, the A ', B', C ', D' signals all have a value of 0 with respect to the reference DC level. However, if any of the photodetecting elements is abnormal, only the output of the abnormal photodetecting element is not zero.

For example, if there is an error in the PDB photodetector in the photodetector as shown in FIG. In this case, it may be determined that there is a problem with the device that receives the light. In this case, only the B signal needs to be controlled. In addition, if only B 'and D' signals are non-zero, it is determined that a radial tilt has occurred, and accordingly, if only A 'and B' signals are non-zero, it is determined that a tangential phase difference offset has occurred. Can be performed.

That is, the servo error signals A ', B', C ', and D' are first to fourth subtractors to correct electrical signals A, B, C, and D output from the respective photodetecting elements of the photo detector. Feedback is made to (203 to 206). For example, the first subtractor 203 corrects the A signal by subtracting the A 'signal of the abnormality detector 202 from the A signal output from the photodetector and outputs the RF signal to the RF and servo error generator 103. do. The remaining second to fourth subtractors 204 to 206 are also corrected in the manner described above for the B, C, and D signals output from the photodetector. Here, the first to fourth subtractors 203 to 206 may be configured within the optical pickup 102 or may be configured outside the optical pickup 102 as shown in FIG. 3.

This process continues until the values of the servo error signals A ', B', C ', and D' all become zero.

The determination unit 105 is provided between the optical pickup 102 and the offset removing unit 104 to determine and control this.

That is, the loop formed by the focus servo drive signal and the tracking servo drive signal output from the servo controller 106 is for high frequency control, and the loop formed by the signal output from the offset remover 104 is for low frequency control.

In the present invention, since four photodetecting elements of the photodetector are configured, four servo error signals RF, FE, TE, and TG are used to remove the offset. The number of servo error signals used for cancellation may vary.

As described above, the present invention can identify which photodetecting device has a problem, and can control each of the photodetecting devices that have an abnormality, so that a correct source can always be provided to the servo control unit.

As described above, according to the recording and reproducing control method of the optical recording medium according to the present invention, four types of servo error signals (e.g., RF, FE, TE, TG) obtained by the electric signal output from the optical detection element are used. Therefore, not only the phase difference offset generated due to the disk itself or the like can be efficiently removed, but also the offset due to the cross correlation between the RF, FE, TE, and TG can be removed.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the spirit of the present invention.

Therefore, the technical scope of the present invention should not be limited to the contents described in the embodiments, but should be defined by the claims.

Claims (11)

Receives an electrical signal proportional to the amount of reflected light output from each photodetector of the photodetector in the optical pickup, receiving an RF signal, a focus error (FE) signal, a radial tracking error (TE) signal, and a tracking error in the tangential direction Generating a (TG) signal; Detecting each DC level from the RF, FE, TE, and TG signals and then controlling the predetermined DC level; And And detecting the abnormality of each photodetecting device from the RF, FE, TE, and TG signals whose DC level is adjusted, and correcting the signal of the photodetecting device with the abnormality. Recording playback control method. The method of claim 1, The signal generation step of the recording and reproduction control method of the optical recording medium, characterized in that for generating the RF, FE, TE, TG signal by applying the following matrix.

The method of claim 1, wherein the DC level control step Detecting a DC level of each signal by low pass filtering the RF, FE, TE, and TG signals, respectively; And adjusting a DC level outside the reference level by comparing the detected DC level with a preset reference level. The method of claim 1, wherein the correcting step A recording and reproducing control method for an optical recording medium, characterized by detecting the presence or absence of an abnormality of each light detecting element by applying the following determinant.

Receives an electrical signal proportional to the amount of reflected light output from each photodetector of the photodetector in the optical pickup, receiving an RF signal, a focus error (FE) signal, a radial tracking error (TE) signal, and a tracking error in the tangential direction Generating a (TG) signal; Detecting each DC level from the RF, FE, TE, and TG signals and then controlling the predetermined DC level; Detecting an abnormality of each photodetecting device from the RF, FE, TE, and TG signals whose DC level is adjusted in the step, and correcting a signal of the abnormal photodetecting device; And And generating a focus drive signal and a tracking drive signal from the FE and TE signals in the above step to perform focus and tracking servo. Receives an electrical signal proportional to the amount of reflected light output from each photodetector of the photodetector in the optical pickup, receiving an RF signal, a focus error (FE) signal, a radial tracking error (TE) signal, and a tracking error in the tangential direction An RF and servo error generation unit for generating a (TG) signal; A DC level detection and correction unit configured to detect respective DC levels from the RF, FE, TE, and TG signals and then control the preset reference levels; And And an abnormality detection and correction unit for detecting the abnormality of each photodetecting device from the RF, FE, TE, and TG signals of which the DC level is adjusted, and correcting a signal of the photodetecting device having an abnormality. An apparatus for controlling recording and reproducing of a recording medium. The method of claim 6, The RF and servo error generator And a RF, FE, TE, and TG signal are generated by applying the following determinant.

The method of claim 6, wherein the DC level detection and correction unit Optical recording, wherein the RF, FE, TE, and TG signals are low pass filtered, respectively, to detect the DC level of each signal, and then the DC level outside the reference level is adjusted by comparing the detected DC level with the reference level. Device for controlling recording and reproducing of media. The method of claim 6, wherein the abnormality detection and correction unit An apparatus for recording and reproducing an optical record carrier, characterized by detecting the presence or absence of an abnormality of each light detecting element by applying the following determinant.

The method of claim 9, wherein the abnormality detection and correction unit And a light detection element value other than zero with respect to a reference DC level among the obtained light detection element values A ', B', C ', and D'. The method of claim 1, wherein the abnormality detection and correction unit The difference between the signal values (A ', B', C ', D') of the photodetecting device in which the abnormality is detected and the source signal values (A, B, C, D) output from the respective corresponding photodetecting devices is obtained. And outputting to the RF and servo error generating unit.

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