JP2006331521A - Optical information recording and reproducing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that the S/N ratio often deteriorates in the push-pull signals with large offset effects when using a disk having shallow grooves with small pitches in a multi-drive, and the offsets of the push pull signals shift largely resulting in tracking errors at the boundary of the recorded and unrecorded areas. <P>SOLUTION: When reproducing, the offsets of the push-pull signals are improved at the boundary of the recorded and unrecorded areas by securing symmetry of the push-pull signals by defocusing the light beam within the limit not degrading the data reading. Thus, even when accessing the area including the boundary of the recorded and unrecorded areas, serious errors such as lens runaway by off-tracking can be avoided. When recording, offsets are applied against tracking errors, by predicting the shifting directions of the push-pull signals. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an information recording / reproducing apparatus for recording information on an optical disc having concentric or spiral tracks on an information recording surface, and reproducing the recorded information, and in particular, tracking servo control by a push-pull method. The present invention relates to a measure for track skipping of the optical information recording / reproducing apparatus used.

  Current consumer optical discs include a read-only type represented by music CDs, CD-ROMs, DVD-ROMs, and DVD-Videos, a once-write type represented by CD-Rs and DVD-Rs, and CD- There are three types of rewritable types typified by RW, DVD-RAM, and DVD-RW, but there are various standards that differ in recording density, rewritability and usage.

  This has been pointed out as a problem causing confusion for general users. Recently, a product of an optical disc apparatus capable of recording and reproducing all these optical discs has been announced as DVD multi.

  The optimum method for detecting the tracking error signal of these DVD-type discs and CD-type discs is different, and for a CD-type disc having a wide track interval, the three-beam method capable of detecting signals easily and stably is advantageous. It is known that a phase difference method that does not require adjustment of the diffraction direction of light emitted from a light source is advantageous for DVD-ROM and DVD-Video disks with narrow track intervals.

  In addition, the phase difference method cannot be used for a rewritable DVD disc, and a push-pull detection method that detects interference on both sides of a groove using a groove that forms a continuous groove or land, and a beam grating. For example, a differential push-pull method in which the difference is detected by applying one beam to the groove and two beams to the land portion, divided into three, for example, is used.

  Among the optical disk tracking detection methods in such an optical disk drive device, the differential push-pull method generates a push-pull signal having opposite phases by dividing the beam into three parts and hitting the groove and the land, and the differential between them. Although there is a merit that offset such as media tilt and lens shift can be reduced by taking the image, on the disc of the standard that is recorded on both the land and the groove such as DVD-RAM, the laser beam In a recording mode with high power, there is a possibility that recorded data is erased or destroyed by irradiating the sub-beam to the track adjacent to the track to be recorded.

  On the other hand, the push-pull method is widely used for recording type optical disk devices because it does not need to separate beams and can use laser light without waste, but on the other hand, offset occurs due to media tilt or lens shift, Since recorded pits tend to deviate from the center of the groove, it is necessary to perform automatic offset correction.

  Also, when the push-pull method is adopted for DVD-R / RW, the push-pull signal is small due to the structural characteristics of the grooves formed in the disk, so the S / N ratio is poor. Although it has the problem of being easily affected by media tilt and lens shift, in DVD multi-drive, in order to perform tracking of all types of discs described above, birefringent materials such as anisotropic optical crystals and liquid crystals are used. By using a method in which the formed polarizing diffraction grating is driven integrally with the objective lens, a method of reducing offset due to lens shift and covering the entire system with a margin distribution design is employed.

  In order to solve this problem, Japanese Patent Application Laid-Open No. 2004-5859 discloses a method of ensuring an SN ratio even for a disc such as a DVD-R / RW with a narrow groove pitch by using a hologram element. .

  Further, as disclosed in Japanese Patent Application Laid-Open No. 11-339286, a push-pull error signal generating unit that generates a push-pull error signal PP from a difference signal of a divided light receiving unit due to light reflected from an optical disk of a light spot, and a push-pull error signal Equipped with a peak hold circuit that holds the peak value, a bottom hold circuit that holds the bottom value of the push-pull error signal, and an arithmetic circuit that calculates the average value of the peak value and the bottom value, and pushes the offset value based on the average value There is also shown a method of performing balance adjustment of the light spot by performing tracking servo so as to be removed from the pull error signal.

  FIG. 2 shows a block diagram of an example of a conventional optical disc recording / reproducing apparatus. In FIG. 2, an optical disk 10 is an optical disk, and a groove is formed in advance. The optical disk 10 is driven by a spindle motor 11 and is controlled to rotate at a constant rotational speed (CAV) or constant linear speed (CLV) by a spindle servo system (not shown).

In addition to the objective lens, the optical pickup 12 has an optical system such as a laser light source and a photodetector that receives reflected light. The optical light source 12 irradiates the optical disk 10 with a light beam from the laser light source, and the reflected light is passed through the objective lens with a photodetector. Receive light.
Although not shown, the optical pickup 12 controls the movement of the objective lens in the radial direction of the optical disc 10 (for tracking control) and also controls the movement of the objective lens in the vertical direction (for focus control). A two-dimensional actuator is provided. As the tracking control method in this case, as described above, the so-called one-spot push-pull method is used.

  In this example, the optical pickup 12 can be moved in the radial direction of the optical disc 10 as a whole by a traverse motor 13. A seek operation or the like is performed by position control of the optical pickup 12 by the traverse motor 13.

  In this example, the photodetector of the optical pickup 12 is configured as a four-divided detector, as shown in FIG. 3, and the light receiving outputs SA and SB from the four light receiving portions A, B, C, and D are used. , SC, SD are supplied to the RF circuits 14-16. In this case, if divided into a set of two light receiving parts A and B and a set of two light receiving parts C and D, the structure is the same as that of a two-divided detector.

  In the RF circuit 14, a reproduction high-frequency signal RF is generated as a sum signal of the four light receiving outputs SA to SD (a sum signal of the outputs of the two light receiving sections if it is a two-divided detector) and supplied to the signal processing circuit 21. . The signal processing circuit 21 reproduces a digital signal and supplies the digital signal to, for example, a host computer.

  Further, the RF circuit 16 generates a focus error signal FE by the calculation of (SA + SC) − (SB + SD). The focus error signal FE is supplied to the drive coil of the focusing actuator of the two-dimensional actuator of the optical pickup 12 via the phase compensation circuit 17 and the drive amplifier 19, and focus control is performed.

  The RF circuit 15 further generates a tracking error signal TE by the calculation of (SA + SB) − (SC + SD). This tracking error signal TE is supplied to the + side input terminal of the differential circuit 26.

  The peak hold circuit 23 and the bottom hold circuit 24 detect and hold the peak level and bottom level of the TE signal during track movement, respectively. In the average value circuit 25, the peak level detected by the peak hold circuit 23 and the bottom level detected by the bottom hold circuit 24 are averaged and supplied to one − side input terminal of the differential circuit 26.

In the differential circuit 26, the median value of the push-pull signal output from the average value circuit 26 is subtracted from the tracking error signal TE output from the RF circuit 15 as an offset, and this is subtracted from the phase compensation circuit 18 and the drive circuit 20. Then, it is supplied to the drive coil of the tracking actuator of the two-dimensional actuator of the optical pickup 12 to perform tracking control.
JP 2004-5859 A JP 11-339286 A

  However, in an optical system tuned by a DVD-RAM having a low signal amplitude, the S / N of the push-pull signal for DVD-R / RW is not sufficient. In particular, in a DVD-RW having a low reflectance, the push-pull signal amplitude is very low and is easily affected by the offset fluctuation of the push-pull signal. In particular, at the boundary between the recorded area and the unrecorded area, the offset changes due to the influence of the mark. In particular, in a disk with a shallow groove depth, even if the tracking error offset is adjusted so that the asymmetry of the tracking error signal is zero in the unrecorded area or the recorded area, the asymmetry may reach 30% at the boundary. In some cases, off-track may occur at the boundary.

  The push-pull signal at the recording area / unrecorded area boundary is simply shown in FIG.

  FIG. 4 shows a state when the pickup crosses the track, 2-1 is an RF reproduction signal, 2-2 is a PP signal, and 2-3 is a cross section of the track. Usually, at the center of the track, it becomes an RF signal and the PP signal becomes zero. If there is no difference between the inner and outer circumferences of the unrecorded area in (1) and the recorded area in (3), the amount of light entering the detector is balanced, so there is no offset in the push-pull signal. Does not occur. On the other hand, in the area (2) where the inner circumference side is not recorded and the outer circumference side is recorded, and in the area (4) where the inner circumference side is recorded and the outer circumference side is unrecorded, the balance of the amount of light entering the detector is lost. As shown, the push-pull signal is asymmetric with respect to the center of the push-pull signal. In addition, in the symmetry of the push-pull signal calculated by (P + B) / 2 (P−B), if it exceeds ± 20%, symptoms such as off-track occur.

  An object of the present invention is to reduce the influence of asymmetry of a push-pull signal generated at the boundary between recorded and unrecorded areas.

  In the present invention, in reproduction, defocusing is performed within a range that does not hinder data reading, and the symmetry of the push-pull signal is ensured. In recording, the direction of the symmetry of the push-pull signal is predicted, and the offset to the tracking error is detected. The main feature is to ensure the stability of tracking control by applying.

  The optical information recording / reproducing apparatus of the present invention improves the symmetry of the push-pull signal by defocusing at the time of reproduction with respect to the offset of the push-pull signal generated at the boundary between the recording area and the unrecorded area, Even if access to the recording area and the area including the non-recording area occurs, it is possible to avoid a serious error such as lens runaway due to the off-track, and the recording quality can be predicted by predicting the direction in which the offset occurs during recording. There is an advantage that the tracking control can be stabilized while optimizing the focus position which has a significant influence on the tracking.

  An object of reducing offset of a push-pull signal which is a cause of a track deviation occurring at a boundary between a recording area and an unrecorded area, which is remarkable in a shallow groove or narrow groove width disk such as a DVD-RW in a DVD multi-drive. Was realized without adding new parts.

(Embodiment 1)
FIG. 1 is a block diagram of Embodiment 1 of the optical disk recording / reproducing apparatus of the present invention, and 10 to 26 are the same as those in FIG. Reference numeral 27 denotes a DC offset generating circuit, 28 is a differential circuit, and 29 is a control circuit.

  In the DC offset generation circuit 27, an offset amount to be added to the focus error is determined and added to the negative side input of the 28 differential circuit. The control circuit 29 switches the output of the DC offset generation circuit 27 between reproduction and recording and outputs it.

  Next, the defocus amount added at the time of reproduction will be described with reference to FIG.

  FIG. 5 shows push-pull symmetry and jitter characteristics with respect to defocus during reproduction. The upper graph shows the characteristics of defocus and TE symmetry. (1) shows the TE symmetry when the inner peripheral side is a recording area and the outer peripheral side is an unrecorded area. The upper diagram (2) shows the characteristics when the inner circumference side is an unrecorded area and the outer circumference side is a recorded area, and shows the characteristics opposite to (1). When the track in the unrecorded area and the recorded area is being reproduced, the symmetry is zero as shown in (3). On the other hand, the figure below shows the characteristics of defocus and jitter. Jitter increases as the distance from the defocus point at which the jitter is minimized.

  For example, in a disk having a shallow groove, the TE symmetry at the optimum jitter point may exceed the limit. During playback, defocus can be applied until the jitter limit is reached, so if the symmetry limit defocus amount is smaller than the playback limit defocus amount, defocus is applied to the symmetry limit defocus point. By setting the data, it becomes possible to reproduce the data without causing any trouble such as off track.

  At the time of recording, there is a possibility that the quality of a signal to be recorded is greatly lowered due to defocusing. Therefore, countermeasures are taken by off-tracking at the time of recording which does not greatly affect the recording / reproducing quality. The state of control at this time is shown in FIG. Reference numeral 6 denotes an operation when additional recording is performed on a non-recorded area by a linking operation. The section (A) indicates a search operation period, and indicates a period in which a position immediately before the recording start point is searched while repeating track jumps and the like. The section (B) is a track follow-up period, and is a section in which position control and recording clock stabilization are performed in order to perform recording. The section (C) is a section showing a recording operation controlled by WTGT. Section (D) is a track following operation after recording. In the sections (A), (B), and (D), as described above, defocusing is applied to ensure tracking symmetry and stabilize the tracking operation. However, if the same defocus is applied during recording, there arises a problem that the recording quality is greatly impaired. Fortunately, in the operation of appending in this way, since the state that the inner circumference side is not recorded does not occur, it is possible to stabilize the tracking by adding off-track that does not greatly deteriorate the recording / playback quality to the system. Is possible. That is, since the outer peripheral side is always unrecorded during recording, it can be considered that the state (3) in FIG. 4 always occurs. For this reason, recording performance is not significantly impaired by adding off-track during recording and controlling the average value of P3 and B3 in FIG. 4 so as to cause a tracking error.

  As described above, the optical information recording / reproducing apparatus of the embodiment of FIG. 1 ensures the stability of the tracking operation due to the offset of the push-pull signal generated at the boundary between the recording area and the unrecorded area, and the recording / reproducing quality. It can be secured.

(Embodiment 2)
FIG. 7 is a block diagram of Embodiment 2 of the device of the present invention, and 10 to 29 are the same as FIG. Reference numeral 30 denotes a TE symmetry detection circuit.

  The TE symmetry detection circuit 30 measures the TE symmetry near the boundary between the recording area and the unrecorded area, and detects an optimum offset amount.

  In order to explain this procedure, explanation will be given using waveforms of respective parts at the time of detecting TE symmetry at the recording area / unrecorded area boundary of the optical disc apparatus of the present invention shown in FIG.

  In FIG. 8, 8-1) is an RF signal, 8-2) is an ASENV signal obtained by detecting the envelope of the RF signal, 8-3) is a PP signal, and 8-4) is a track jump drive signal. Jump to the inner circumference when positive, and jump to the outer circumference when negative.

  In order to measure the TE symmetry of the boundary, the hold track is released by landing before the boundary (t = τ1). The end of the recording area is searched while looking at the ASENV signal that becomes High level when the envelope of the RF signal exceeds a predetermined level. A timer is started at the timing (t = τ2) when the end of the recording area is detected. A jumpback of two tracks is made at a timing (t = τ3) when a time corresponding to about a half rotation has elapsed from this point. Among these, four extreme values B 1, P 1, B 2 and P 2 are measured and passed to the control circuit 29.

  The control circuit 29 obtains the defocus amount to be added using the four extreme values received from the TE symmetry detection circuit 30. The worst value of TE symmetry at the focus offset = 0 is obtained by (P1 + B1) / 2 (P1-B1). If the focus offset point at which the symmetry of TE is 0 is measured in advance in the drive adjustment process or the like, the TE symmetry limit defocus point can be obtained by calculation using these two points. Of course, the symmetry may be measured at two defocus points and determined by interpolation.

  When it is ensured that the outer peripheral side is not recorded, the offset amount added to the tracking error during recording is set to (P1 + B1) / 2. If it is not possible to determine whether the outer periphery is unrecorded or not, it is determined that the offset value is (P1 + B2) / 2, which is an average value of the minimum value P1 of the peak and the maximum value B2 of the bottom. However, a limiter is set to ensure recording / playback performance.

  In this embodiment, a description has been given on the assumption that a recording boundary, which is a recorded area on the inner periphery and an unrecorded area on the outer periphery, is already prepared. If such an area does not exist, it can be recorded by itself to create such an area.

(Embodiment 3)
In the first and second embodiments, the case has been described in which it is ensured that the TE symmetry is satisfied within the range of the defocus amount that satisfies the recording / playback characteristics as shown in FIG.

  However, depending on the characteristics of the disc, the above conditions may not be satisfied. FIG. 9 shows the relationship between defocus and TE symmetry, and defocus and jitter in this case. In this case, since it is not possible to swing the focus offset to the symmetry limit defocus point, it is necessary to secure reproduction performance by other means.

  In the present embodiment, a coping method in the case of FIG. 9 will be described using the configuration diagram of an embodiment of the optical disc apparatus shown in FIG.

  FIG. 10 is a block diagram of Embodiment 3 of the apparatus of the present invention, and 10 to 30 are the same as FIG. Reference numeral 31 denotes a jitter detection circuit.

  The jitter detection circuit 31 measures the jitter while changing the defocus, and measures an allowable defocus amount. Further, as in the second embodiment, the defocus limit point at which TE symmetry is ensured is measured. When the symmetry limit defocus amount is smaller, the symmetry limit defocus amount is set as the defocus amount, and data is reproduced. If the target limit defocus amount is large, the reproduction limit defocus amount is set as the defocus amount, and the tracking operation is stabilized by adding an offset to the tracking error signal in order to stabilize the tracking operation.

  FIG. 11 shows an example of TE symmetry and jitter defocus characteristics tuned when there is a recording area on the inner circumference side and an unrecorded area on the outer circumference side. That is, after setting the reproduction limit defocus point, the TE symmetry shortage is added as an offset of the tracking error signal. FIG. 12 shows TE symmetry and jitter defocus characteristics when there is an unrecorded area on the inner circumference side and a recorded area on the outer circumference side.

The offset application timing will be described with reference to FIG. 13 showing waveforms of respective parts that will occur when reading from the beginning of the recording area. In FIG. 13, 13-1) indicates an RF signal, and 13-2) indicates an offset amount to be added to the tracking error. 13-3) is a PP signal at that time.
When it is detected at the timing of τ1 that the target position has passed, it jumps back and starts moving to the target position. When returning to a predetermined position, the track follows in the vicinity of the target track (t = τ2). When the start of the recording area is detected (t = τ3), an offset is applied for one rotation starting from that point, and then the offset is gradually returned to zero (t = τ4). That is, since one rotation from the recording start end should be unrecorded on the inner periphery and the symmetry of TE is broken, the tracking operation is stabilized by off-tracking. After one revolution, the inner circumference side is also in a recorded state, so there is no need to add off-track. Therefore, the tracking can be further stabilized by releasing the applied offset.

  As described above, when only the TE offset improvement by defocus is insufficient, the minimum recording / playback can be performed even for a disk having a large TE offset by applying the TE offset.

  Further, when it is known which direction the symmetry of the push-pull signal is shifted, the direction in which the offset is applied can be fixed.

  The optical information recording / reproducing apparatus according to the present invention is effective for recording / reproducing discs having different track pitches with the same optical system, and the push-pull signal is symmetric due to in-plane changes in the groove depth of the disc. This method is also effective as a retry process when it becomes impossible to secure.

1 is a block diagram of an optical information recording / reproducing apparatus according to Embodiment 1 of the present invention. Block diagram of a conventional optical information recording / reproducing apparatus Schematic diagram showing an example of a conventional optical pick Explanatory diagram of problems with conventional optical disk devices (PP signal characteristics at the recording / unrecording boundary) Operational explanatory diagram of the optical information recording / reproducing apparatus in Embodiment 1 of the present invention Explanatory drawing of operation | movement at the time of recording the unrecorded area | region of the optical information recording / reproducing apparatus in Embodiment 1 of this invention Block diagram of an optical information recording / reproducing apparatus in Embodiment 2 of the present invention FIG. 5 is a timing chart for explaining a measurement procedure of TE symmetry of a recording area and an unrecorded area of the optical information recording / reproducing apparatus in Embodiment 1 of the present invention. Operation explanatory diagram of the optical information recording / reproducing apparatus in Embodiment 2 of the present invention Block diagram of an optical information recording / reproducing apparatus in Embodiment 3 of the present invention Operation explanatory diagram of the optical information recording / reproducing apparatus in Embodiment 3 of the present invention Operation explanatory diagram of the optical information recording / reproducing apparatus in Embodiment 3 of the present invention Operation explanatory diagram at the time of reproducing the recording area head portion of the optical information recording / reproducing apparatus in Embodiment 3 of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Optical disk 11 Spindle motor 12 Lens 13 Traverse motor 14 RF amplifier 15 RF amplifier (TE calculation)
16 RF amplifier (FE calculation)
17 Phase compensation circuit 1
18 Drive circuit 1
19 Phase compensation circuit 2
20 Drive circuit 2
21 Signal Processing 22 DC Offset Generation Circuit 2
23 Peak hold circuit 24 Bottom hold circuit 25 Averaging circuit 26 Subtractor 2
27 DC offset generation circuit 1
28 Subtractor 1
29 Control circuit 30 TE symmetry detection circuit 31 Jitter measurement circuit

Claims (9)

By irradiating a light spot to the land or groove formed on the optical disk with an optical pickup, information is recorded on the land or the groove, or information is reproduced from the optical pickup, and the optical spot is read from the optical disk. Focus error signal generating means for generating a focus error signal indicating a deviation between the light spot and the information recording surface from the difference signal of the divided light receiving section due to reflected light, and an offset of the push-pull signal at the boundary between the recording area and the unrecorded area An optical information recording / reproducing apparatus, wherein the optical pickup is driven by performing focus servo so that a focus offset within a predetermined range is removed from the focus error signal. 2. The optical information recording / reproducing apparatus according to claim 1, wherein a focus offset is applied so that an offset of a push-pull signal generated at a boundary portion between a recording area and an unrecorded area is within a predetermined range only during reproduction. A push-pull error signal generating means for generating a push-pull error signal indicating a deviation between the light spot and the track from a difference signal of the divided light receiving unit due to the reflected light from the optical disc of the light spot, and at least one focus position; Based on the output results of the TE symmetry detection means for measuring the offset amount of the push-pull signal generated at the boundary between the recording area and the unrecorded area, and the TE symmetry detection means at least at two focus points, the TE symmetry is The optical information recording / reproducing apparatus according to claim 1, further comprising: a focus offset generating unit configured to generate a focus offset within a predetermined range. 4. The optical information recording according to claim 3, wherein a defocus point at which the symmetry of TE becomes 0 is stored in advance in a nonvolatile memory in the drive, and a TE offset is generated using this information. Playback device. 2. The optical information recording / reproducing apparatus according to claim 1, wherein an upper limit of the focus offset is set. The reproduction limit defocus amount detection means for measuring the jitter while changing the focus and measuring the limit defocus condition, wherein the reproduction limit defocus amount is set as an upper limit value of the focus offset. 5. The optical information recording / reproducing apparatus according to 5. When a defocus amount exceeding the upper limit of the focus offset is detected, the remaining difference is subtracted from the push-pull signal, and tracking servo is performed at one of the positions of the land or the groove, whereby the optical 6. The optical information recording / reproducing apparatus according to claim 5, wherein the pickup is driven. By irradiating a light spot to the land or groove formed on the optical disk with an optical pickup, information is recorded on the land or the groove, or information is reproduced from the optical pickup, and the optical spot is read from the optical disk. Push-pull error signal generating means for generating a push-pull error signal indicating a deviation between the light spot and the track from the difference signal of the divided light receiving part due to reflected light, and an offset of the push-pull signal at the boundary between the recording area and the unrecorded area The optical pickup is driven by performing tracking servo at either the land or the groove so that the offset within the predetermined range is removed from the push-pull error signal. Characteristic optical information recording / reproduction Location. 9. The optical information recording according to claim 8, wherein the offset is applied to the push-pull signal so that the offset of the push-pull signal generated at the boundary between the recording area and the non-recording area is within a predetermined range only during recording. Playback device.

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