JP2001222827A - Optical disk reproducing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical disk reproducing device capable of correcting the crosstalk components in an FE signal so as to offset these components. SOLUTION: The optical disk reproducing device having an optical pickup adopting an astigmatism system for focus servo error detection for controlling a light spot for reading in follow-up to the wobbling of a surface in order to read the information recorded on an optical disk 14 has a correction control system 44 which memorizes the push-pull error signal of the main spot and the amplitude and phase relation for one period component crossing in inside and outside diameter directions of a focus stroke in order to suppress the crosstalks to be included into the focus errors by the groove crossing to cross the lands and grooves formed at the optical disk, calls out this relation data with the push-pull signal by the sub-spot or main spot apart about half the track pitch to form a focus stroke signal, makes computation with the focus signal by the main spot and offsets the groove crossing crosstalks. As a result, the crosstalk components in the FE signal are so corrected as to be offset.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an astigmatic optical pickup for reproducing an optical disk having recording tracks formed at a depth where a tracking signal can be easily formed, such as a land / groove of a DVD-RAM system. The present invention relates to an optical disk reproducing device having the same.

[0002]

2. Description of the Related Art In general, an optical disk such as a DVD-RAM disc is a system in which signals are recorded on both lands and grooves having the same width, and the lands and grooves have a depth of 0.74 μm (2 0.6 GB) or 0.615
This is a disk structure formed in μm (in the case of 4.7 GB). Here, λ is the wavelength of the reproduction laser light. When reading information by applying focus servo to an optical disk with such a structure, if the light spot crosses the track due to eccentricity of the optical disk or access operation, the intensity distribution pattern of the reflected light becomes asymmetric due to diffraction development by lands and grooves. As a result, the track traveling direction (Tan direction)
The operation in which the left and right light intensity distributions become asymmetric with a large contrast is repeated on a two-segment photodetector having a dividing line of.

Under such circumstances, in the case of an optical pickup employing a focus error detection method employing an astigmatism method, a change in light intensity distribution due to crossing of the track depends on the adjustment accuracy of the detection system. Is FE crosstalk in which modulation components due to groove crossing leak into the focus error signal because they cannot be canceled by the difference calculation of the diagonal sum of astigmatism signal detection (also referred to as feed-through or groove crossing signal)
There was a problem. In addition, the astigmatism method is a detection method that is susceptible to pattern noise of reflected light due to the influence of the adjustment accuracy. Note that the above FE means a focus error.

[0004] In particular, the dividing line of the photodetector (photodetector) for detecting a signal is located at a position closer to the center of the reflection spot than to the Tan.
If the direction is shifted in the direction or if astigmatism occurs in the reflected light due to the birefringence of the optical disk, the FE crosstalk increases, and an unnecessary signal is superimposed on the detection signal in a state where the focus servo is applied. You. In this state, a focus shift occurs due to the focus servo operation, or an AC (alternating current) signal component due to track traversal mixes into the focus drive system, and is necessary to drive the objective lens in the optical axis direction against surface shake. A component other than the signal in the surface vibration frequency band is mixed, and the driving waveform becomes larger than a required level, and depending on the frequency component, an unnecessary sound is generated.
The component generates heat at a value determined by multiplying the effective value of the level by the coil resistance, and thus causes a problem such as a rise in temperature.

[0005] For example, an example of the analysis result of the cause of the occurrence of the groove crossing stroke of the focus signal is described in the literature Lissajous a.
nalysis of focus crosstalk in optical disk systems
(SPIE Vol. 1499 Optical D
data Storage '91, pp. 354-359
Page), where the ideal optical system and PP (push-pull) under the occurrence of misalignment and various aberrations
The relationship between the signal and the astigmatism error signal is analyzed. In this document, the focus crosstalk in the astigmatism method is such that the division of the pattern on the disk surface in the Tan direction is offset because the center of the light spot on the photodetector does not match the division line of the photodetector. Indicates that the focus crosstalk signal and the PP signal have the same phase. In this document, it is also shown by calculation and experimental results that when there is astigmatism in the return optical system from the reading light spot to the light spot on the photodetector, there is an ellipse with a certain phase difference. Have been.

[0006]

SUMMARY OF THE INVENTION Incidentally, in order to solve the above problems, Japanese Patent Application Laid-Open Nos.
-64104 or the 60th Japan Society of Applied Physics, etc.
Measures have been reported. JP-A-10-640
No. 80 describes a method of canceling FE crosstalk due to crossing a groove, which occurs when a photodetector is displaced in the Tan direction by an astigmatism method, using a tangential push-pull signal. However, in this method, although the FE crosstalk component due to the deviation of the photodetector in the Tan direction can be corrected, there is a problem that the crosstalk component due to astigmatism cannot be canceled out because the phase is different.

In Japanese Patent Application Laid-Open No. H10-64104, focus detection by the astigmatism method is performed using two spots shifted by 1/2 track pitch. Since the groove crossing signal mixed in the focus error signal is a signal having a pitch cycle, the FE crosstalk component in the astigmatism signal separated by 1/2 track pitch is shifted by 1/2 track pitch to obtain a phase difference of half cycle. Signal. On the other hand, the focus error signals are in phase.
Therefore, when these two signals are added, the focus error signal of the same phase is doubled, and the focus crosstalk component having a half-period phase difference is canceled out as a signal of almost the opposite phase.
As described above, in this method, when the above-mentioned FE crosstalk is a signal of a track pitch cycle and is symmetric at a half pitch position, an operation of adding an astigmatism error signal formed at a half pitch distance is performed. Then, there is an advantage that the groove-crossing signal can be canceled.

However, in this method, if the land and groove widths do not match or the groove structure does not match, the FE crosstalk at a distance of 1/2 track pitch does not necessarily have the opposite phase, so that the level is reduced to some extent. Sometimes it did not completely cancel.
Also, in the optical pickup for reproducing a DVD-RAM disk using three beams at the 60th Japan Society of Applied Physics, a three-beam reading optical system arranged at a position shifted by 1/2 track pitch on the disk surface is used for focusing. The detection uses an astigmatism method. Of the two detection signals detected by the main spot shifted by 1/2 track pitch and the two front and rear sub-spots, the astigmatism FE signal is an in-phase signal at the spot interval of 20 μm because almost the same surface shake is detected. However, since the FE crosstalk component is a one-track-pitch periodic signal, the cross-talk is symmetric with respect to a half-track pitch, and is substantially in opposite phase. By adding and calculating two focus signals using the characteristics of the two signals, the focus error signal is doubled because it has the same phase, and the FE crosstalk signal is canceled because it has the opposite phase.

Even in this case, if the FE crosstalk is not symmetrical at a half track pitch, complete cancellation cannot be performed, and only a reduction in the crosstalk component to some extent can be achieved. In this method, the photodetector is divided into 12 parts, and D
In order to detect PP (differential push-pull) and astigmatism, it is necessary to connect all outputs of the twelve divided photodetectors, and the number of wirings increases. In order to make the photodetector for the sub-beam the same as the focus detection signal of the main spot, the size of the photodetector is reduced. In addition to the position adjustment, the angle adjustment is required. In addition, after adjusting the focus error detection optimally, the grating is rotated to optimize the detection of the DPP signal, and adjusted so as to be placed on a track on the board at a distance of 1/2 track pitch. Since the position on the container changes, it is necessary to adjust the focus error detection again. As described above, there are problems in that the number of wirings of the photodetector increases, the adjustment accuracy becomes strict, and the number of adjustment steps increases.

[0010] The present invention focuses on the above problems,
The purpose of this invention is to solve this problem effectively. The purpose is to memorize the relationship between FE crosstalk and PP error signal, form a correction waveform signal from a TE signal, and convert this correction waveform signal and the FE signal. It is an object of the present invention to provide an optical disc reproducing apparatus capable of performing a calculation to correct the crosstalk component in the FE signal so as to cancel out the crosstalk component.

[0011]

SUMMARY OF THE INVENTION According to the invention defined in claim 1, in order to read information recorded on an optical disk, a focus servo error detection for controlling a light spot for reading by following a surface deviation is used for astigmatism. In an optical disc reproducing apparatus having an optical pickup adopting the aberration method, a push-pull error signal of a main spot and a push-pull error signal of a main spot are used to suppress crosstalk mixed in a focus error due to traversing a groove that traverses a land or a groove formed on the optical disc. Of the focus crosstalk, the amplitude and phase relationship for one cycle traversing in the outer diameter direction is stored, and this relationship is reduced to about 1 /
A crosstalk signal is formed by calling a push-pull signal by a sub-spot separated by two track pitches, and has a correction control system that calculates a focus signal by the main spot and cancels out cross-groove crosstalk.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an optical disk reproducing apparatus according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram showing an example of an optical pickup used in an optical disk reproducing apparatus according to the present invention, FIG. 2 is a block diagram showing a signal processing system for processing a signal from the optical pickup, and FIG. 3 is obtained by the signal processing system. FIG. 3 is a block diagram illustrating a correction control system that corrects a focus error (FE) signal from each signal.

In FIG. 1, this optical pickup 2 is
In the detection method, an optical system uses a DPP method for tracking detection and an astigmatism method for focus detection. In the figure, LD is a laser element for outputting a laser beam L for reproduction, 4 is a grating for obtaining three light beams from the laser beam L, 6 is a polarization beam splitter,
Reference numeral 8 denotes a collimator lens for converting the laser beam L into a parallel light beam, and 1
0 is a λ / 4 plate, 12 is an objective lens for focusing the laser beam L on the optical disk 14, 16 is a cylindrical lens,
Reference numeral 18 denotes a photodetector including a photodetector and the like for detecting light reflected from the optical disk 14. This photodetector 18
A divided segment 18A composed of A, B, C and D, and a first divided segment 1 composed of E1 and E2 on both sides thereof
8B and a second divided segment 1 composed of F1 and F2
8C. The optical disc 14 is irradiated with three light spots, the reflected light of the central light spot enters the four-segment segment 18A as a main spot, and the light spots on both sides of the disc are divided into two-segment segments 18B and 18C, respectively. It will be incident as a sub spot.

FIG. 2 shows a processing system for a signal obtained from the photodetector 18. In the figure, 20, 22, 24, 2
6 is a subtractor, 30, 32, 34, 36, 38 and 40 are adders, and 42 is an amplifier for giving a gain K. Also, 4
Reference numeral 4 denotes a correction control system 44 for forming a correction FE signal from the FEm signal, which is a feature of the present invention. Therefore, each signal in the figure is represented as follows. TEs = E1 + F1− (E2 + F2) TEm = (A + D) − (B + C) FEm = (A + C) − (B + D) SUMs = E1 + F1 + E2 + F2 SUMm = A + B + C + D DPP = (A + D) − (B + C) −K × ｛
1)-(E2 + F2)｝

In the optical pickup and signal processing system configured as shown in FIGS. 1 and 2, the laser light L emitted from the laser
After forming two light beams, the light beams are converted into parallel light by the collimator lens 8 through the polarizing beam splitter 6, and then are incident on the objective lens 12 to form a light spot of three beams on the surface of the optical disk 14. The three light spots are in the track traveling direction (T
In the radial direction (disc radial direction), they are formed on the board at a distance of 1/2 track pitch in the radial direction (disc radial direction). Optical disc 14 is DVD-RAM
Track pitch of the first generation and DVD-RW board is 0.74
μm, but the second generation of 4.7GB RAM is 0.615μ
m and 0.74 μm when shared. The light beam reflected from the optical disk 14 passes through the return optical system, and astigmatism is given to the light beam by the astigmatism detection system including the collimator lens 8 and the cylindrical lens 16, and the segments 18 A, 18 of the photodetector 18 are provided.
B, forming corresponding light spots respectively on 18C,
A signal corresponding to each light intensity is formed.

Here, the main spot is 4 as described above.
The two sub-spots detected in the segment 18A are divided into two segments E1, E2 and F1, F, respectively.
2 is detected. SUMm (RF) signal, tracking signal TEm, focus error signal FE at main spot
m is formed by the following operation. SUMm = A + B + C + D FEm = (A + C) − (B + D) TEm = (A + D) − (B + C) The DPP signal is a subspot PP signal at TEm.
The Es signal is added by adjusting the gain of the spot intensity ratio K. DPP = (A + D) − (B + C) −K × ｛(E1 + F
1)-(E2 + F2)｝

In previous papers and experimental results, there is a correlation that the PP error signal and the FE crosstalk in the astigmatism detection method change depending on the condition of the optical system aberration and the adjustment of the optical pickup. Crosstalk is a signal having a track pitch period, and has a fixed relationship between the PP error signal and the amplitude and phase, so that a Lissajous waveform can be drawn. From this, it can be said that there is a relationship that a signal similar to FE crosstalk can be formed from the PP signal. From the above relationship,
The principle of the present invention will be described in the following two systems. (1) Crosstalk is formed by the PP error signal of the sub spot. (2) Crosstalk is formed by the PP error signal of the main spot.

1) P of sub-spot of three beams for DPP
When forming an FE crosstalk signal using the P signal. The relationship between the TEs signal, which is a sub-PP error signal formed by the signals detected from E1, E2, F1, and F2 of the photodetector 18, and the FE crosstalk signal formed by the astigmatism method formed by the sub-spot will be examined. The TEm signal, which is the PP signal formed from the main spot, and the FE crosstalk component (F
Emc) has a correlation. For the relationship between the amplitudes,
Although the Em signal has a waveform close to a sine wave, the FE crosstalk may be a non-sine wave, and the relationship between the two waveforms is not necessarily linear but may be non-linear. Even in this case, since the two signals are signals having a cycle of the track pitch, the mutual relationship between the amplitudes can be described, and the level relationship can be represented as a general table stored in a ROM or the like. When this is represented by G in amplitude relation (function of level relation) and phase difference term e (jθ), FEmc can be approximated as in the following equation 1. FEmc = G × e (jθ) × TEm (1) The data in the table is the relation data for one period of the track pitch during the movement in the inner diameter direction and the outer diameter direction. Note that j in the equation 1
Indicates the square root of -1, and θ indicates the phase.

Further, as described above, P
Let the P signal be the TEs signal. Further, the FE crosstalk component due to the sub spot is expressed as FEsc. In the configuration of the present invention, since the photodetector for the sub-spot for DPP detection is a two-segment segment, the astigmatism error signal cannot be calculated as in the four-segment segment. If a four-segment segment is formed and the calculation of the focus signal is performed from here, the FE crosstalk FEsc mixed into the FE signal
The components can be said to be the same as the relationship between the PP signal and the FEmc signal in the main spot. This is because the main spot and the sub-spot are separated from each other by 1/2 track pitch in the track traveling direction and the radial direction. However, both spots receive a change in the diffraction distribution due to the groove crossing due to the eccentricity of the disk. Light is passed through the same astigmatism detection optical system to form a spot on the photodetector,
Assuming that the interval between the spots and the interval between the photodetectors and the relative position are the same, the modulation is completely the same, and the difference due to the difference in the spot position occurs, but only the difference in the track position of the FE crosstalk. . From this, the relationship between the PP signal and the FE crosstalk signal is the same in the case of the main spot and the case of the sub spot, and can be described as the relationship shown in Expression 2 below. FEsc = G × e (jθ) × TEs (2)

However, in the case of both the main spot and the sub spot, the FE signal is a signal related to surface deviation, and the PP signal is a signal related to eccentricity. Therefore, there is no correlation between these two signals. Therefore, the FE signal itself cannot be obtained from the PP signal by calculation. It is merely possible to obtain only the crosstalk components related to each other across tracks. The TEse signal and the TEsf signal, which are tracking signals by the photodetectors E1, E2, F1, and F2 forming the TEm signal and the TEs signal, have a phase difference due to the positional relationship between the main spot and the sub spot. However, when a differential operation is performed on the signals before and after to form the TEs signal, a signal having a phase opposite to that of the TEm signal is obtained as described later.
It affects only the amplitude change of the Es signal.

Here, X is the position, Q is the position of the spot set by the grating, and P is the track pitch.
The PP signal by two sub-spots is converted into TEs1 signal, TE
Assuming that the signal is s, the following is obtained. TEm = A × SIN (2πX / P) TEs1 = B1 × SIN (2π (X + Q) / P) TEs2 = B2 × SIN (2π (X−Q) / P) TEs = TEs1 + TEs2 where B1 is three spots for DPP Is the amplitude of the PP signal formed from the spot on the side where the phase is advanced (proportional to the spot light intensity), B2 is the amplitude of the PP signal due to the spot on the side where the phase is delayed (proportional to the spot light intensity), and A is The amplitude of the PP signal by the main spot (proportional to the spot light intensity) is shown.

Here, assuming that B1 = B2 in forming the TEs signal which is a PP signal by the sub spot, the TEs signal is represented by the following equation. TEs = B1 × SIN (2πX / P) × COS (2πQ
/ P) Here, the relationship of COS (Q / P × 2π) represents a change in the amplitude of the TE signal synthesized by the sub-spot in an amplitude term not related to x, and the tracking detection signal is Q to the PP signal by the main spot. When / P <１ ／, in-phase with + amplitude, 1
In the case of / 4 <Q / P <3/4, the phase is reversed at the negative amplitude. DPP
In the case of detecting a signal, the amplitude term of the COS becomes -1 at Q = P / 2, so that the phase is in the opposite phase and has the maximum amplitude.

The sub-spot for DPP is set so that Q = P / 2 when the track pitch P of the DVD-RW is 0.74 μm. For this reason, DVD-RAM
In the case of 4.7 GB, Q = 1.2 × P / 2, and the amplitude is smaller than −1. FE of the PP signal formed at the position of Q and the focus error signal assumed to be detected here
The crosstalk signal has a phase difference determined by the Q / P ratio, but the TEs signal obtained by calculating the front and rear spots has an in-phase or anti-phase relationship. Here, FEsc formed from the TEs signal
The signal can be assumed to be a waveform having a half track pitch phase different from that of the FEmc signal.

In the present invention, in order to harden the relationship (including the amplitude and the phase) of the above equation 1, one cycle of the waveform of the TEm signal is divided in the time axis direction, and the crosstalk component is stored at that timing. . For this reason, the level equally divided in the amplitude direction is compared with the input waveform, the timing when the level is reached is formed, and the FE crosstalk waveform data corresponding to the timing is recorded in the memory. For example, the waveform of the TEm signal is divided into 32 by the AD converter, and the FE crosstalk level at the time when the waveform level matches the waveform level is stored in the memory. However, the FE crosstalk waveform with respect to the waveform of the TEm signal differs depending on the crossing direction of the track, the speed of the crossing, and the focus pull-in point. For this reason, it is necessary to take a procedure for taking in an actual waveform just before correction and storing it.

Next, the FE crosstalk due to the sub-spots is formed according to the above equation (2). This is because when the relationship between the FE crosstalk signal and the PP signal is stored in the memory by the above-mentioned waveform capture, the PP signal by the sub spot is used as an input signal, and the maximum amplitude value of the PP signal when the waveform is captured is obtained. When the data is read out from the memory at the same timing as the amplitude, divided in the amplitude direction and read at the timing corresponding to the level, and converted into an analog waveform, the crosstalk component FEsc based on the relationship of the above equation 2 is formed. become. In this way, the FE crosstalk component due to the sub spot is formed, and this is calculated as the FE crosstalk component due to the main spot. In this case, since the crosstalk components have different waveforms of 1/2 track pitch phase, they are added. Thus, the FE crosstalk component is suppressed to some extent. However, this operation is F
This is only the E crosstalk component, and cannot form any FE signal. There is no improvement in the FE signal by adding the in-phase FE signals as in the known example of the three-spot, four-division system.

2) A case where the periodic component is canceled based on the basic characteristics of the relationship between the PP signal and the FE crosstalk component in the main spot. In this case as well, a focus signal cannot be formed.
Only cancellation of the FE crosstalk component is performed. Since the cancellation is performed by assuming an average crosstalk component without responding to the instantaneous fluctuation of the FE signal, some error of the FE due to the cancellation occurs. In this case, since the periodic component is formed by itself, the FE crosstalk component can be canceled even if it is not a FE crosstalk component symmetrical at a half track pitch. This principle stores the FE crosstalk by the TEm signal in the same process as in the case of the sub spot. This data is read by the TEm signal of the main spot to form a correction waveform, and the correction waveform and the FEm signal are calculated. Since this correction waveform has the same phase as the FEm signal, it is subtracted.

Now, the correction control system 44 (see FIG. 2) for performing the above-described arithmetic processing will be specifically described with reference to FIG. In FIG. 3, reference numeral 50 denotes an A / D signal of the FEm signal.
A / D converter for conversion, 52 is a waveform storage unit for storing the digital signal of the converted waveform, and 54 is this waveform storage unit 5
2 is a D / A converter that converts the digital waveform signal output from 2 into an analog signal to form a corrected waveform signal;
An arithmetic unit that calculates the Em signal and the corrected waveform signal to form a corrected FE signal. SW is a group of changeover switches for switching an input signal between the m side and the s side, and 58 is a TE switch.
A level comparator for comparing signal levels; 60 and 62 each a binarizing circuit for binarizing the TE signal and the SUM signal;
64 is a direction detecting unit for detecting the direction of track crossing, 66
Reference numeral denotes an address forming unit that forms an address signal storing a waveform to be read from the waveform storage unit 52, based on the output signal of the level comparison unit 58 and the output signal of the direction detection unit 64.

Next, the operation of the correction control system 44 will be described. First, among the signals formed by the signal processing system shown in FIG. 2, the FEm signal (focus error signal), TE
m signal (tracking error signal), TEs signal, SU
Each signal of the Mm signal and the SUMs signal is input to the correction control system 44. The FEm signal obtained from the four-segment segment 18A (see FIG. 2) that receives the main spot is A
The digital data is converted by the / D converter 50. Focus error signal is LP of -3dB decrease in 30KHz band
A signal processed by F (low-pass filter).
CLK (clock) of the D conversion is a signal of about 100 KHz. In the illustrated example, the changeover switch group SW is connected to the m side.

The TEm signal, which is a PP error signal formed from the main spot, adjusts the maximum amplitude value to a certain level, and then, for example, a level comparator 58 composed of a level comparator.
Is input to Here, for example, a comparison is made with a voltage level obtained by equally dividing the maximum value into 32. When the input signal reaches the level of equal division, 6-bit address data of that level is output with a sign of ±. This division level is used as an address. In order to perform this operation, the input signal is converted into a digital signal using not only the level comparator but also an A / D converter, and the converted data is compared with a level obtained by equally dividing the maximum amplitude, and the converted data matches the level. Timing may be formed at times. Here, the data to be compared may be located between certain levels, but one of the levels may be used as the address data.

The TEm signal is binarized by the binarization circuit 60 to detect the direction of track crossing. The sum signal of the main spot is input as a SUMm signal.
Similarly, a TEs signal as a PP error signal and a SUMs signal as a sum signal due to the sub spot are input. SUM
The m signal is binarized by the binarization circuit 62 and digitally processed by the direction detection unit 64 with the binarized TEm signal to detect the direction of track crossing. Here, FIG. 4 shows the state of the signal waveform in the direction detection unit together with the area division and the direction signal. In this illustrated example, the time when the vehicle is traversing inward is shown on the left, and the time when the vehicle is traversing outward is shown on the right. The phase difference between the TEm signal and the SUMm signal changes by ± 90 degrees depending on the transverse direction. The level of the SUMm signal at the time of the rising of the PP signal is H level when traversing inside, and L level when traversing outside, and differs depending on the direction of track crossing, and a direction signal is formed.

Also, 0-90 °, 90-180 of the PP signal
2 bits (addresses AD6 and AD7) for detecting and discriminating each area of 180-270 ° and 270-360 °
Is used. As described above, the waveform of the TEm signal is, for example, 32 levels (6 bits AD5 to A5) in the level comparing section 58.
D0), and a timing and an address to reach the level are formed. Also, if the direction signal is the address AD
Used as 8. As a result, a timing corresponding to the level of the PP signal is formed. At this timing, the A / D converted data of the FE crosstalk waveform is recorded in the waveform storage unit 52 at the address corresponding to the level of the TEm signal, whereby 1 Data relating to the period of the PP signal and the FE crosstalk waveform is recorded.

When the correction waveform is read and the pickup is fed at a low speed by the feed mechanism or when the still (single track jump) is distinguished, the speed is added as the address AD9. As a result, the FE crosstalk voltage is stored in the waveform storage unit 52 identified by the 10-bit addresses AD9 to AD0. If the signal change in high-speed feeding is small, the address AD
9 may be omitted and a 9-bit address may be used as a whole. After the disk is started, the FE crosstalk signal is initially recorded in the waveform storage unit 52 for one cycle while only the focus servo is applied. In the process of recording the FE crosstalk signal first, after the focus servo operation, the FE crosstalk signal corresponding to the PP signal is recorded in the waveform storage unit 52 by the TEm signal and the SUMm signal. This is because the servo loop gain is relatively low and F
The FE crosstalk signal may be recorded in the waveform storage unit 52 after the track crossing is captured once or plural times in the inner circumferential direction and the outer circumferential direction while the E crosstalk signal error level remains unchanged.

Next, crosstalk during track crossing is corrected. This operation is a step of extracting the waveform data recorded in the waveform storage unit 52 using the TEs signal by the sub spot. Here, similarly to the above, the TEs signal and the SUMs signal by the sub spot are combined with the TEm signal of the main spot and S
It is input in place of the UMm signal. Thus, direction detection and area detection are performed, and the TEs signal is
And the address data is formed. The address data is input to the waveform storage unit 52, and FE crosstalk waveform data corresponding to the level corresponding to the TEs signal is read out.
A conversion is performed to form a corrected waveform signal S1. Here, since the phase of the PP signal due to the sub spot has a phase difference of 180 degrees from the TEm signal, an FE crosstalk signal having a phase difference of 180 degrees is formed as a correction waveform signal S1. FE by adding
A corrected FE signal having a reduced crosstalk component is formed.

FIG. 5 shows an example in which the FE crosstalk component is a sine wave similar to the TEs signal and has a phase difference. Here, as shown in FIG.
FIG. 5 shows a case where E crosstalk has a phase difference of about 40 degrees (FIG. 5).
(See (B)), an FE crosstalk waveform is recorded by the TEm signal, a crosstalk (corrected waveform signal) is formed from the TEs signal by the sub spot, and the operation of canceling the crosstalk component is performed. As a result, the opposite phase can be corrected, and the component of the groove crossing is reduced (FIG. 5C).
reference). As a result, the FE crosstalk signal mixed in the corrected FE signal is canceled, the high frequency signal component is reduced, the focusing error is reduced, the unnecessary high frequency component flowing through the focus drive coil is reduced, and the generation of sound and heat generation Can be prevented and operation stability can be ensured.

As described above, when each of the above waveforms is close to a sine wave, a canceling waveform can be formed with an opposite phase, and there is an effect of correction. However, as shown in FIG. 6, when the FE crosstalk becomes a distorted waveform, and when the waveform delayed by 1/2 track pitch is not a symmetrical waveform, the crosstalk at a position separated by 1/2 track pitch is completely lost. Since the signal does not have the opposite polarity, the effect of cancellation is small and the effect as in the previous example cannot be obtained. Further, as described above, the waveform of the crosstalk signal formation may be formed by the TEm signal by the main spot. Here, in the previous example, the extraction of the waveform recorded in the waveform
Although this was performed with the s signal, this is performed with the TEm signal itself.

In the above system, the signal input for recording and correcting the FE crosstalk waveform is switched, but in this system, the signal is not switched. In this case, since the FE crosstalk is obtained at the same phase, the calculation in the calculation unit 56 is a subtraction. FIG. 7 shows a waveform diagram of the system using the main spot. In the case of the main spot, since the polarity can be reversed, crosstalk can be suppressed by canceling. Also,
During the servo operation, the waveform of the FE crosstalk becomes smaller following the loop operation in the low-frequency component. Therefore, in this area, the level of the FE crosstalk is detected and the operation is limited so that the correction operation is not performed. There is also.

[0037]

As described above, according to the optical disk reproducing apparatus of the present invention, the following excellent functions and effects can be exhibited. As a result of correcting crosstalk by this method, when an error signal is detected on the land-groove type optical disk by the focus detection by the astigmatism method, the FE crosstalk signal mixed into the FE signal is canceled, and the high-frequency signal component is reduced. Decreased,
Reduces focusing error, reduces unnecessary high-frequency current components flowing through the focus drive coil, prevents sound generation and coil heat generation, ensures stable servo operation, and stabilizes element temperature characteristics. .

[Brief description of the drawings]

FIG. 1 is a configuration diagram showing an example of an optical pickup used in an optical disk reproducing device according to the present invention.

FIG. 2 is a block diagram showing a signal processing system for processing a signal from an optical pickup.

FIG. 3 is a block diagram showing a correction control system for correcting a focus error (FE) signal from each signal obtained by a signal processing system.

FIG. 4 is a diagram showing a state of a signal waveform in a direction detection unit together with a region division and a direction signal.

FIG. 5 is a diagram illustrating an example in which an FE crosstalk component is a sine wave similar to the TEs signal and has a phase difference.

FIG. 6 is a diagram showing an FE correction waveform signal.

FIG. 7 shows a crosstalk waveform diagram of a system using a main spot.

[Explanation of symbols]

2 optical pickup, 4 grating, 6 polarization beam splitter, 10 λ / 4 plate, 14 optical disk,
16: cylindrical lens, 18: photodetector, 44 ...
Correction control system, 52: waveform storage unit, 56: calculation unit, 58 ...
Level comparison unit, 64: direction detection unit, 66: address formation unit

Claims (1)

[Claims] 1. An optical disc reproducing apparatus having an optical pickup adopting an astigmatism method for detecting a focus servo error for controlling an optical spot for reading to follow a surface deviation in order to read information recorded on an optical disc. In the apparatus, in order to suppress crosstalk mixed in a focus error due to traversing a groove crossing a land or a groove formed on the optical disc, one of the push-pull error signal of the main spot and the crosstalk in the outer diameter direction among the focus crosstalk is suppressed. The amplitude and phase relationship for the period is stored, and this relationship data is called up by a push-pull signal by a sub spot or a main spot separated by about 1/2 track pitch to form a focus crosstalk signal. Calculate to eliminate crosstalk An optical disc reproducing apparatus having a correction control system.