JP2006155722A - Differential push-pull signal adjusting device and optical disk device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable adjustment of a differential push-pull signal so that tracking control can be performed appropriately. <P>SOLUTION: This apparatus is provided with a subtraction part 22 generating a differential push-pull signal DPP in accordance with a balance coefficient (k), a difference value calculating part 24 calculating a top difference value DT and a bottom difference value DB based on respective difference push-pull signals DPP when an objective lens 12B is moved to an inner peripheral side or an outer peripheral side of an optical disk 50, a code discriminating part 25, a balance coefficient setting part 26, and a adjustment control part 21 changing a difference push-pull signal DPP generated next time by decreasing or increasing the balance coefficient (k) by the prescribed change quantity when the top difference value DT and the bottom difference value DB are both positive or negative, and not changing the difference push-pull signal DPP generated next time by deciding the balance coefficient (k) when a code of at least one side of the top difference value DT and the bottom difference value DB is changed from the previous time of at least one side becomes 0. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a differential push-pull signal adjustment device and an optical disc device, and is suitable for application to an optical disc device that records data on an optical disc and reproduces the data from the optical disc, for example.

  2. Description of the Related Art Conventionally, in an optical disc apparatus, a device that records video, music, etc. as data on an optical disc such as a Blu-ray Disc (trademark), and reads the data from the optical disc to reproduce video, music, etc. has been proposed. ing.

  In such an optical disc apparatus, data is recorded by irradiating a laser beam from an optical pickup onto a spirally formed track on the signal recording layer of the optical disc, and the reflection of the laser beam by the optical pickup is performed. Data is reproduced by detecting light.

  At this time, the optical disk device adjusts the position of the optical pickup by the sled motor in the inner or outer peripheral side of the optical disk, that is, in the tracking direction, and moves the position of the objective lens mounted on the optical pickup in the approach or separation direction with respect to the optical disk. That is, by adjusting in the focus direction, the laser beam is irradiated in a state where the desired track is in focus.

  Here, the optical disc apparatus performs tracking control of the optical pickup based on a so-called DPP (Differential Push Pull) method so that the laser beam follows a desired track. That is, as shown in FIG. 8A, the disk device irradiates a desired track TRK in the signal recording layer of the optical disk 50 with three divided laser beams, and the central main beam spot BS1 is a track. The light is irradiated almost at the center of TRK, and the other two side beam spots BS2 and BS3 are irradiated with a predetermined distance from the center of the track TRK in opposite directions.

Then, the optical disc apparatus is configured so that the differential push-pull signal generator 1 shown in FIG.
The two-divided photodetectors 2 to 4 receive the reflected light from the main beam spot BS2 and the side beam spots BS3 and BS4, respectively, and generate detection signals. Based on the detection signals, the differential pusher 5 generates the main push-pull signal MPP. And a difference signal generated by the differential amplifiers 6 and 7 is added by the adding amplifier 8 to generate a side push-pull signal SPP.

  Subsequently, the optical disk apparatus subtracts the side push-pull signal SPP multiplied by a predetermined balance coefficient k from the main push-pull signal MPP by the subtraction unit 9 of the differential push-pull signal generation unit 1 to obtain the following formula:

  DPP = MPP-k · SPP (1)

A differential push-pull signal DPP as shown in FIG. 4 is generated, and a predetermined tracking control process is performed in accordance with the signal.

Further, some optical disk devices have been proposed that generate the optimum differential push-pull signal DPP for each optical disk by adjusting the value of the balance coefficient k for each optical disk 50 (for example, patents). Reference 1).
JP 2002-183992 A (pages 6 to 7)

  By the way, in the optical disk apparatus having such a configuration, in addition to the optical pickup being roughly moved in the tracking direction by the sled motor, the objective lens is finely moved in the tracking direction (that is, the inner or outer peripheral side of the optical disk) by the biaxial actuator. By doing so, tracking control is performed with high accuracy.

  However, in the optical disk apparatus, the differential push-pull signal DPP depends on whether the objective lens is moved to the inner peripheral side or the outer peripheral side of the optical disk by the biaxial actuator due to the influence of aberrations in the optical pickup. The characteristics will change.

  For this reason, even if the optical disc apparatus performs tracking control using such a differential push-pull signal DPP, the problem is that the laser beam cannot correctly follow the desired track, that is, the correct tracking control cannot be performed. was there.

  The present invention has been made in consideration of the above points, and a differential push-pull signal adjustment device for adjusting a differential push-pull signal so that tracking control can be normally performed, and tracking control based on the differential push-pull signal. An optical disc apparatus capable of appropriately performing the above is proposed.

  In order to solve such a problem, in the differential push-pull signal adjusting device of the present invention, the optical disc can move in the proximity direction or the separation direction with respect to the optical disc with respect to a desired track formed on the signal recording layer of the optical disc. The objective lens is moved in the inner circumferential direction of the optical disk by using a plurality of reflected signals based on the reflected light and a predetermined ratio coefficient when the light beam is irradiated through the objective lens that can move in the inner circumferential direction or the outer circumferential direction. Alternatively, a push-pull signal generating means for generating a differential push-pull signal having a substantially sinusoidal shape due to the eccentricity of the optical disk for tracking control to be moved in the outer peripheral direction, and an inner lens in which the objective lens is moved in the inner peripheral direction of the optical disk. In the peripheral state and the outer peripheral state in which the objective lens has moved in the outer peripheral direction of the optical disc, An envelope value generating means for generating an envelope value of the signal, a difference value calculating means for calculating a difference value by subtracting the envelope value of the outer peripheral side state from the envelope value of the inner peripheral side state, and the difference value is positive or negative In some cases, the ratio coefficient is decreased or increased by a predetermined change amount to change the differential push-pull signal to be generated next time, and the sign of the difference value changes from the previous time or the difference value becomes 0 Control means for determining the ratio coefficient and not changing the differential push-pull signal to be generated next time is provided.

  As a result, tracking control is normal in both the inner and outer states by simply changing the ratio coefficient according to the sign of the difference value between the envelope value in the inner peripheral state and the envelope value in the outer peripheral state. It is possible to adjust to a differential push-pull signal that can be performed at the same time.

  In the differential push-pull signal adjustment method of the present invention, the desired track formed in the signal recording layer of the optical disc can move in the proximity direction or the separation direction with respect to the optical disc, and the inner circumference direction of the optical disc or The objective lens is moved in the inner circumference direction or the outer circumference direction of the optical disk using a plurality of reflected signals based on the reflected light when the light beam is irradiated through the objective lens that can move in the outer circumference direction and a predetermined ratio coefficient. A push-pull signal generation step for generating a differential push-pull signal having a substantially sinusoidal shape due to the eccentricity of the optical disc, and an inner peripheral side state in which the objective lens has moved in the inner peripheral direction of the optical disc When the objective lens moves toward the outer periphery of the optical disk, the envelope of each differential push-pull signal is detected. An envelope value generation step for generating a difference value, a difference value calculation step for calculating a difference value by subtracting the envelope value of the outer peripheral side state from the envelope value of the inner peripheral side state, and the difference value is positive or negative When the differential push-pull signal to be generated next time is changed by decreasing or increasing the ratio coefficient by a predetermined change amount, and the sign of the difference value changes from the previous time or when the difference value becomes 0, the ratio coefficient And a control step that does not change the differential push-pull signal to be generated next time is provided.

  As a result, tracking control is normal in both the inner and outer states by simply changing the ratio coefficient according to the sign of the difference value between the envelope value in the inner peripheral state and the envelope value in the outer peripheral state. It is possible to adjust to a differential push-pull signal that can be performed at the same time.

  Further, in the optical disc apparatus of the present invention, the desired track formed on the signal recording layer of the optical disc can move in the proximity direction or the separation direction with respect to the optical disc and move in the inner circumferential direction or the outer circumferential direction of the optical disc. A differential push-pull signal having a substantially sinusoidal shape is generated by the eccentricity of the optical disk, using a plurality of reflected signals based on reflected light when the light beam is irradiated through the objective lens to be obtained and a predetermined ratio coefficient The push-pull signal generation means, and the envelope value of each differential push-pull signal in the inner peripheral state where the objective lens moves in the inner peripheral direction of the optical disc and in the outer peripheral side state where the objective lens moves in the outer peripheral direction of the optical disc. The envelope value generation means to be generated and the envelope value of the outer peripheral side are subtracted from the envelope value of the inner peripheral side state. Difference value calculation means for calculating a difference value by changing the differential push-pull signal to be generated next time by decreasing or increasing the ratio coefficient by a predetermined change amount when the difference value is positive or negative, When the sign of the value changes from the previous time or when the difference value becomes 0, the ratio coefficient is determined and the differential push-pull signal to be generated next time is not changed, and based on the differential push-pull signal Tracking control means for performing tracking control for moving the objective lens in the inner circumferential direction or the outer circumferential direction of the optical disk is provided.

  Thereby, the differential push-pull signal can be adjusted only by changing the ratio coefficient according to the sign of the difference value between the envelope value of the inner peripheral side state and the envelope value of the outer peripheral side state. Tracking control can be normally performed in any of the outer peripheral states.

  According to the present invention, tracking can be performed in both the inner peripheral state and the outer peripheral state only by changing the ratio coefficient according to the sign of the difference value between the envelope value in the inner peripheral state and the envelope value in the outer peripheral state. Differential push-pull signal adjustment device and differential push-pull signal that can be adjusted to a differential push-pull signal that can be normally controlled, and thus adjust the differential push-pull signal so that tracking control can be normally performed An adjustment method can be realized.

  Further, according to the present invention, the differential push-pull signal can be adjusted simply by changing the ratio coefficient according to the sign of the difference value between the envelope value in the inner peripheral side state and the envelope value in the outer peripheral side state. An optical disc apparatus capable of normally performing tracking control in both the peripheral side state and the outer peripheral side state can be realized.

  Hereinafter, an embodiment of the invention will be described in detail with reference to the drawings.

(1) Overall Configuration of Optical Disc Device (1-1) Generation of Differential Push-Pull Signal In FIG. 1, 10 shows the overall configuration of the optical disc device according to the present invention as a whole, and an optical disc 50 made of Blu-ray Disc (trademark). On the other hand, video and audio are recorded as data, and the data is read to reproduce video and audio.

  The optical disk apparatus 10 is configured to be controlled in an integrated manner by a control unit (not shown). By driving a thread motor (not shown) via a servo control unit 11 as a tracking control means, the optical pickup 12 is attached to the optical disk 50. It is made to move in the inner or outer peripheral side, that is, in the tracking direction.

  The optical pickup 12 moves the objective lens 12B in the proximity direction or the separation direction (that is, the focus direction) with respect to the optical disc 50 by the biaxial actuator 12A controlled by the servo control unit 11, and moves the objective lens 12B in the inner circumferential direction or It is designed to move in the outer peripheral direction (that is, the tracking direction).

  As a result, the optical disc apparatus 10 focuses the laser beam irradiated from the objective lens 12B of the optical pickup 12 on a desired portion (hereinafter referred to as a desired track) of a spiral track formed on the signal recording surface of the optical disc 50. It is made like that.

  The optical pickup 12 irradiates the signal recording surface of the optical disc 50 with the laser beam divided into three by an optical component (not shown) and the objective lens 12B, and reflects the reflected light in the same manner as the two-divided photodetectors 2 to 4 (FIG. 8). Detected by a photodetector (not shown), detection signals S1 and S2 are generated according to the detection result at this time, and supplied to the main push-pull signal generation unit 13 and the side push-pull signal generation unit 14, respectively.

  The main push-pull signal generator 13 generates a main push-pull signal MPP based on the detection signal S1, and supplies this to the subtractor 22 of the differential push-pull signal adjuster 20. Similarly, the side push-pull signal generation unit 14 generates a side push-pull signal SPP based on the detection signal S2, and supplies this to the subtraction unit 22.

  The subtraction unit 22 includes a main push-pull signal MPP supplied from the main push-pull signal generation unit 13, a side push-pull signal SPP supplied from the side push-pull signal generation unit 14, and a ratio coefficient supplied from the balance coefficient setting unit 26. As a balance coefficient k (details will be described later)

  DPP = MPP-k · SPP (2)

Based on the above, a differential push-pull signal DPP is generated and supplied to the servo controller 11 and the analog / digital converter 23.

  The servo control unit 11 moves the optical pickup 12 roughly in the tracking direction based on the differential push-pull signal DPP, and finely moves the objective lens 12B in the tracking direction, thereby irradiating the laser from the objective lens 12B. Tracking control for causing light to follow a desired track with high accuracy is performed.

(1-2) Adjustment of Differential Push-Pull Signal The differential push-pull signal adjustment unit 20 is controlled by the adjustment control unit 21. When a new optical disc 50 is loaded in the optical disc apparatus 10, the optical disc 50 is adjusted. The balance coefficient k is adjusted according to the individual difference of the optical disc 50, and as a result, the differential push-pull signal DPP according to the individual difference of the optical disc 50 is generated.

  In practice, when a new optical disk 50 is loaded in the optical disk device 10, the adjustment control section 21 first sends a tracking stop command to the servo control section 11 to forcibly stop the tracking control, thereby tracking the objective lens 12B. Do not move in the direction.

  Here, as shown by the solid line and the alternate long and short dash line in FIG. 2A, when the optical disc 50 is loaded, the optical disc apparatus 10 has a slight track on the optical disc 50 due to an accuracy problem at the time of manufacturing the optical disc 50 or the like. The center of rotation and the center of rotation do not coincide with each other, so-called eccentricity occurs.

  At this time, since the tracking control is forcibly stopped and the objective lens 12B is stationary in the tracking direction, the subtracting unit 22 (FIG. 1) is affected by the eccentricity of the rotating optical disk 50, and the subtraction unit 22 (FIG. A differential push-pull signal DPP having a substantially sinusoidal shape as shown is generated.

  Further, the adjustment control unit 21 supplies the tracking drive signal PT as shown on the lower side of FIG. 3A from the servo control unit 11 to the biaxial actuator 12A (FIG. 1), so that the objective lens 12B is first measured for the measurement time. The object lens 12B is forcibly moved only in the inner circumferential direction of the optical disc 50 (hereinafter simply referred to as the inner circumferential side) for tm, and then the objective lens 12B is forcibly moved only in the outer circumference direction of the optical disc 50 for the measurement time tm (see FIG. This is hereinafter simply referred to as the outer peripheral side).

  At this time, as shown in the upper side of FIG. 3A, the subtractor 22 (FIG. 1) causes a difference in waveform between the inner peripheral side and the outer peripheral side, as shown in the upper side of FIG. 3A. A dynamic push-pull signal DPP is generated.

  Incidentally, since the measurement time tm corresponds to n cycles of the differential push-pull signal DPP (where n is an integer of 3 or more), the differential push-pull signal DPP has a maximum value and a minimum value during the measurement time tm. N values will be included.

  The analog / digital converter 23 sequentially converts both the inner and outer differential push-pull signals DPP sequentially supplied from the subtractor 22 into a digital DPP signal D 1, and sequentially converts it to the difference value calculator 24. Supply.

  Based on the digital DPP signal D1 sequentially supplied from the analog / digital converter 23, the difference value calculation unit 24 performs the top hold and the bottom hold for a predetermined time corresponding to one period of the digital DPP signal, thereby performing the digital DPP. The maximum value and the minimum value in one cycle of the signal are acquired. Further, the difference value calculation unit 24 obtains n maximum and minimum values on the inner circumference side by repeating this for the measurement time tm, and then repeats this again for the measurement time tm. Get n local maxima and minima.

  Next, the difference value calculation unit 24 first calculates an average of (n−2) local maximum values excluding the maximum value and the minimum value among the n local maximum values on the inner peripheral side, and calculates this as the inner peripheral side top. The average of (n−2) minimum values excluding the maximum value and the minimum value among the n minimum values is calculated as the value Ti, and this is set as the inner peripheral side bottom value Bi. Subsequently, the difference value calculation unit 24 similarly calculates the average of (n−2) local maximum values on the outer peripheral side and sets this as the outer peripheral side top value To and (n−2) local minimum values. Is calculated as an outer peripheral side bottom value Bo.

  Further, the difference value calculation unit 24 is represented by the following formula:

  DT = Ti-To (3)

The top difference value DT obtained by subtracting the outer peripheral side top value To from the inner peripheral side top value Ti is calculated based on

  DB = Bi-Bo (4)

The bottom difference value DB obtained by subtracting the outer circumference side bottom value Bo from the inner circumference side bottom value Bi is calculated, and the top difference value DT and the bottom difference value DB are supplied to the code determination unit 25.

  The sign determination unit 25 determines the sign of the top difference value DT and the bottom difference value DB, that is, whether the sign is positive, 0, or negative, and supplies the sign determination result to the balance coefficient setting unit 26.

  The balance coefficient setting unit 26 sets a new balance coefficient k according to the code determination result supplied from the code determination unit 25 and supplies this to the subtraction unit 22 (details will be described later).

  In response to this, the subtracting unit 22 generates a new differential push-pull signal DPP based on the new balance coefficient k according to the above-described equation (2).

  The nonvolatile memory 27 stores a reference balance coefficient kr adjusted according to a predetermined reference optical disc when the optical disc apparatus 10 is manufactured at a factory. The balance coefficient setting unit 26 reads the reference balance coefficient kr from the nonvolatile memory 27 based on the control of the adjustment control unit 21 and can set it as the balance coefficient k.

  As described above, the differential push-pull signal adjustment unit 20 uses the main push-pull signal MPP and the side push-pull signal SPP to generate a new balance coefficient k based on the differential push-pull signal DPP generated immediately before by the subtraction unit 22. And the differential push-pull signal DPP is adjusted by the subtracting unit 22 generating a new differential push-pull signal DPP based on the new balance coefficient k.

(2) Push-Pull Signal Adjustment Principle Here, the push-pull signal adjustment principle in the differential push-pull signal adjustment unit 20 will be described.

  As indicated by a broken line in FIG. 3A, the inner peripheral side top value Ti, the inner peripheral side bottom value Bi, the outer peripheral side top value To, and the outer peripheral side bottom value Bo are respectively the differential push-pull signals on the inner peripheral side. An upper envelope value and a lower envelope value in the DPP, and an upper envelope value and a lower envelope value in the differential push-pull signal DPP on the outer peripheral side are shown.

  In addition, as shown by a one-dot chain line in FIG. 3A, assuming a hypothetical intermediate value between the inner peripheral side top value Ti and the inner peripheral side bottom value Bi, this intermediate value is determined in the differential push-pull signal DPP. This represents the center of amplitude, and this is hereinafter referred to as an inner circumference side amplitude center value Ci. Similarly, a virtual intermediate value between the outer peripheral side top value To and the outer peripheral side bottom value Bo is set as the outer peripheral side amplitude center value Co.

  Here, the optical disc apparatus 10 has a top difference value DT> 0 and a bottom difference value DB> 0 as shown in FIG. 3A, that is, an inner circumference side amplitude center value Ci and an outer circumference side amplitude center value Co. When the difference is large, the amplitude center of the differential push-pull signal DPP is greatly different between the inner peripheral side and the outer peripheral side. Therefore, in the tracking control in the case where the objective lens 12B is positioned on the inner peripheral side and the outer peripheral side. The reference position is greatly different, and as a result, tracking control cannot be performed normally.

  Further, the optical disc apparatus 10 also has the inner peripheral amplitude center value Ci in the case of the top difference value DT <0 and the bottom difference value DB <0 shown in FIG. 3C, as in the case shown in FIG. As a result, the tracking control cannot be performed normally.

  On the other hand, as shown in FIG. 3B, if the subtractor 22 (FIG. 1) generates substantially the same differential push-pull signal DPP on the inner peripheral side and the outer peripheral side, the top difference value DT≈0 and The bottom difference value DB≈0, and the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co substantially coincide.

  In this case, the optical disc apparatus 10 always keeps tracking control since the tracking reference position is always substantially constant regardless of whether the objective lens 12B is located on the inner circumference side or the outer circumference side. Can be performed normally (ideal state).

  By the way, as shown in FIG. 4A, when the top difference value DT ≧ 0 and the bottom difference value DB ≦ 0, the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co do not completely match, The difference between the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is small compared to the case shown in FIGS. 3 (A) and 3 (C).

  At this time, since the difference between the inner peripheral side amplitude center value Ci and the outer peripheral side amplitude center value Co is relatively small, the optical disc apparatus 10 has a case where the objective lens 12B is positioned on the inner peripheral side and a case where it is positioned on the outer peripheral side. The tracking reference position shift is small, and as a result, tracking control can be performed almost normally (nearly ideal).

  Also, as shown in FIG. 4B, when the top difference value DT ≦ 0 and the bottom difference value DB ≧ 0, the inner circumference side amplitude center value Ci and the outer circumference are the same as in the case shown in FIG. Since the difference from the side amplitude center value Co is small, the optical disc apparatus 10 can perform tracking control almost normally as a result (similarly, a state close to ideal).

  Therefore, the differential push-pull signal adjustment unit 20 (FIG. 1) according to the present invention is the case where the top difference value DT> 0 and the bottom difference value DB> 0 shown in FIG. When the tracking control cannot be normally performed as in the case of the top difference value DT <0 and the bottom difference value DB <0, the subtraction unit 22, the analog / digital converter 23, the difference value calculation unit 24, the sign determination unit 25 and a series of balance coefficient changing loops by the balance coefficient setting unit 26 are repeated, and the differential push-pull signal DPP is gradually changed by gradually changing the value of the balance coefficient k, so that the top difference value DT and the bottom difference are changed. The value DB was gradually brought closer to “0”.

  By the way, the optical disk apparatus 10 needs to keep the preparation period from when the new optical disk 50 is loaded to when tracking control is performed to start recording and reproduction of data as short as possible. It is desirable to complete in a short time.

  However, since the optical disk apparatus 10 requires a predetermined movement time when moving the objective lens 12B of the optical pickup 12 to the inner peripheral side and the outer peripheral side, the number of movements of the objective lens 12B, that is, the balance coefficient k It is necessary to keep the number of changes as small as possible.

  For this reason, the differential push-pull signal adjustment unit 20 starts changing the balance coefficient k, and when the sign of at least one of the top difference value DT and the bottom difference value DB changes, that is, as shown in FIG. When the top difference value DT ≧ 0 and the bottom difference value DB ≦ 0, or when the top difference value DT ≦ 0 and the bottom difference value DB ≧ 0 shown in FIG. The balance coefficient k at this point was determined to be a necessary and sufficiently appropriate value for the optical disc 50 loaded, assuming that the state can be normally performed.

  As a result, the optical disc apparatus 10 can adjust to the appropriate differential push-pull signal DPP sufficiently and sufficiently by using the balance coefficient k set in such a short time as shown in FIG. 3B. Although it does not necessarily match the “ideal state” shown, the “near-ideal state” shown in FIG. 4 (A) or FIG. 4 (B) can be obtained, and as a result, tracking control is almost normal. Can be done.

(3) Differential Push-Pull Signal Adjustment Processing Procedure Next, when the differential push-pull signal adjustment unit 20 (FIG. 1) gradually changes the value of the balance coefficient k to adjust the differential push-pull signal DPP. The differential push-pull signal adjustment processing procedure RT1 will be described with reference to the flowchart shown in FIG.

  When a new optical disc 50 is loaded in the optical disc device 10, the adjustment control unit 21 of the differential push-pull signal adjustment unit 20 receives a disc loading notification from a control unit (not shown), and the new optical disc 50 is loaded. In response to this, the differential push-pull signal adjustment processing procedure RT1 is started and the process proceeds to step SP1.

  In step SP1, the adjustment control unit 21 temporarily prevents the objective lens 12B from moving in the tracking direction by sending a tracking stop command to the servo control unit 11 (FIG. 1) while the optical disk 50 is rotated. The process proceeds to the next step SP2.

  In step SP2, the adjustment control unit 21 causes the balance coefficient setting unit 26 to read the reference balance coefficient kr from the nonvolatile memory 27, supplies this to the subtraction unit 22 as the balance coefficient k, and proceeds to the next step SP3.

  In step SP3, the adjustment control unit 21 supplies the tracking drive signal PT as shown on the lower side of FIG. 3A from the servo control unit 11 to the biaxial actuator 12A (FIG. 1), thereby moving the objective lens 12B inside. The differential push-pull signal DPP at this time is generated by the subtractor 22 in order to move sequentially to the circumferential side and the outer circumferential side, and the process proceeds to the next step SP4.

  In step SP4, the adjustment control unit 21 causes the difference value calculation unit 24 to acquire the inner circumference side top value Ti, the inner circumference side bottom value Bi, the outer circumference side top value To, and the outer circumference side bottom value Bo. The top difference value DT and the bottom difference value DB are calculated according to the equation (4), and the process proceeds to the next step SP5.

  In step SP5, the adjustment control unit 21 determines whether or not the top difference value DT ≧ 0 and the bottom difference value DB ≦ 0, or the top difference value DT ≦ 0 and the bottom difference value DB ≧ 0, that is, FIG. It is determined whether or not the state is either FIG. 4B or FIG.

  If an affirmative result is obtained in step SP5, this indicates that the difference between the virtual inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co in the differential push-pull signal DPP is slight or almost the same. Therefore, it is shown that the tracking control can be normally performed in the optical disc apparatus 10, and at this time, the adjustment control unit 21 already has a necessary and sufficient balance coefficient k at this time for the loaded optical disc 50. The balance coefficient k is determined, and the process proceeds to step SP15.

  On the other hand, if a negative result is obtained in step SP5, this means that the difference between the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is relatively large, so that the optical disc apparatus 10 cannot perform the tracking control normally. At this time, the adjustment control unit 21 proceeds to the next step SP6 in order to change the value of the balance coefficient k.

  In step SP6, the adjustment control unit 21 determines whether or not the top difference value DT> 0 and the bottom difference value DB> 0, that is, whether or not the state is as shown in FIG. If a positive result is obtained here, the adjustment control unit 21 proceeds to the next step SP7.

  Here, when the relationship between the balance coefficient k, the top difference value DT, and the bottom difference value BT is represented on a two-dimensional plane, the top difference value DT and the bottom difference are represented on the two-dimensional plane as shown in FIG. Each value BT is represented as one straight line.

  Incidentally, in this two-dimensional plane, the slopes of the top difference value DT and the bottom difference value BT and the balance coefficients kt and kb, which are intercepts of the respective k axes, are different values for each optical disc 50 (FIG. 1). In addition to kt <kb as shown in FIG. 5, there are cases where kt = kb and kt> kb.

  When the balance coefficient k is within the appropriate area AR1 (where kt <AR1 <kb), the balance coefficient k can generate a differential push-pull signal DPP that allows the optical disc apparatus 10 to perform tracking control normally. , Representing an “appropriate” value.

  Here, the top difference value DT> 0 and the bottom difference value DB> 0 means that the balance coefficient k> kb and the balance coefficient k> kt at this time, for example, the balance coefficient k is the balance coefficient k9. Represents.

  In step SP7, the adjustment control unit 21 decreases the balance coefficient k by a predetermined change value α [dB] in order to decrease the top difference value DT and the bottom difference value DB from the current values, and proceeds to the next step SP8. .

  Incidentally, this means that, for example, in FIG. 6, the balance coefficient k is changed from the balance coefficient k9 to the balance coefficient k8.

  In step SP8, the adjustment control unit 21 sequentially moves the objective lens 12B to the inner peripheral side and the outer peripheral side in the same manner as in step SP3, and proceeds to the next step SP9.

  In step SP9, the adjustment control unit 21 causes the difference value calculation unit 24 to acquire the inner peripheral side top value Ti, the inner peripheral side bottom value Bi, the outer peripheral side top value To, and the outer peripheral side bottom value Bo in the same manner as in step SP4. The top difference value DT and the bottom difference value DB are calculated, and the process proceeds to the next step SP10.

  In step SP10, the adjustment control unit 21 determines whether at least one of the top difference value DT or the bottom difference value DB has become 0 or less, that is, whether the sign has changed. If a negative result is obtained here, this is still the top difference value DT> 0 and the bottom difference value DB> 0, so the difference between the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is also The adjustment control unit 21 returns to step SP7 and changes the value of the balance coefficient k again.

  Incidentally, in FIG. 6, for example, although the balance coefficient k is changed from the balance coefficient k9 to the balance coefficient k8, the balance coefficient k8> kb and the balance coefficient k8> kt, so that the balance coefficient k8 is the top. This means that the difference value DT> 0 and the bottom difference value DB> 0.

  On the other hand, if a positive result is obtained in step SP10, this means that the top difference value DT> 0 and the bottom difference value DB ≦ 0, or the top difference value DT ≦ 0 and the bottom difference value DB> 0 because the balance coefficient k is changed. In other words, is the state shown in FIG. 4 (A) or FIG. 4 (B), and is the difference between the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co small? It shows that both are almost the same. At this time, the adjustment control unit 21 determines that the balance coefficient k has already been changed to an appropriate value necessary and sufficient for the optical disc 50, determines the balance coefficient k, and proceeds to the next step SP15.

  Incidentally, in FIG. 6, for example, the balance coefficient k is sequentially changed from the balance coefficient k9 to the balance coefficient k5 and the bottom difference value DB <0 because the balance coefficient k5 <kb. This means that the balance coefficient k5 is included in the appropriate area AR1.

  On the other hand, if a negative result is obtained in step SP6, this indicates that the top difference value DT <0 and the bottom difference value DB <0, that is, the state shown in FIG. 3C. At this time, the adjustment control unit 21 proceeds to the next step SP11.

  Incidentally, in FIG. 6, this indicates that the balance coefficient k <kb and the balance coefficient k <kt at this time, for example, that the balance coefficient k is the balance coefficient k1.

  In step SP11, the adjustment control unit 21 increases the balance coefficient k by a predetermined change value α [dB] in order to increase the top difference value DT and the bottom difference value DB from the current value, and proceeds to the next step SP12. .

  Incidentally, this means that, for example, in FIG. 6, the balance coefficient k is changed from the balance coefficient k1 to the balance coefficient k2.

  In step SP12, the adjustment control unit 21 sequentially moves the objective lens 12B to the inner peripheral side and the outer peripheral side in the same manner as in step SP3, and proceeds to the next step SP13.

  In step SP13, the adjustment control unit 21 causes the difference value calculation unit 24 to acquire the inner peripheral side top value Ti, the inner peripheral side bottom value Bi, the outer peripheral side top value To, and the outer peripheral side bottom value Bo in the same manner as in step SP4. The top difference value DT and the bottom difference value DB are calculated, and the process proceeds to the next step SP14.

  In step SP14, the adjustment control unit 21 determines whether at least one of the top difference value DT or the bottom difference value DB is equal to or greater than 0, that is, whether the sign has changed. If a negative result is obtained here, since this still remains the top difference value DT <0 and the bottom difference value DB <0, the difference between the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is also In this case, the adjustment control unit 21 returns to step SP11 and changes the value of the balance coefficient k again.

  Incidentally, in FIG. 6, for example, the balance coefficient k is changed from the balance coefficient k1 to the balance coefficient k2. However, since the balance coefficient k2 <kt and the balance coefficient k2 <kb, the top difference value DT <0 and This means that the bottom difference value DB <0 remains unchanged.

  On the other hand, if an affirmative result is obtained in step SP14, this means that the top difference value DT ≧ 0 and the bottom difference value DB <0, or the top difference value DT <0 and the bottom difference value DB ≧ by changing the balance coefficient k. 4, that is, a state as shown in FIG. 4A or 4B, and the difference between the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is slight. Or the two are almost identical. At this time, the adjustment control unit 21 determines that the balance coefficient k has already been changed to an appropriate value necessary and sufficient for the optical disc 50, determines the balance coefficient k, and proceeds to the next step SP15.

  Incidentally, in FIG. 6, for example, the balance coefficient k is sequentially changed from the balance coefficient k1 to the balance coefficient k4, and the top difference value DT> 0 because the balance coefficient k4> kt, that is, This means that the balance coefficient k4 is included in the appropriate area AR1.

  In step SP15, the adjustment control unit 21 regards that the balance coefficient k can be set to a necessary and adequate value, and assumes that the optical disc apparatus 10 is in a state where tracking control can be normally performed, and issues a tracking start command to the servo control unit 11 ( 1), the tracking control based on the differential push-pull signal DPP generated using an appropriate balance coefficient k is resumed, and then the process proceeds to the next step SP16 to perform the differential push-pull signal. The adjustment processing procedure RT1 is terminated.

(4) Operation and Effect In the above configuration, the differential push-pull signal adjustment unit 20 of the optical disc apparatus 10 temporarily stops tracking control when a new optical disc 50 is loaded in the optical disc apparatus 10. Based on the differential push-pull signal DPP when the objective lens 12B of the optical pickup 12 is forcibly moved to the inner peripheral side and the outer peripheral side, the inner peripheral side top value Ti, the inner peripheral side bottom value Bi, and the outer peripheral side top The value To and the outer peripheral side bottom value Bo are acquired, and the top difference value DT and the bottom difference value DB are calculated.

  After that, when the signs of the top difference value DT and the bottom difference value DB are both positive or negative, the differential push-pull signal adjustment unit 20 decreases or increases the balance coefficient k by the change value α [dB] again and again A series of balance coefficient changing loops such as calculating the top difference value DT and the bottom difference value DB are repeated, and when the sign of at least one of the top difference value DT or the bottom difference value DB changes, the value of the balance coefficient k is set. Determine.

  Therefore, the differential push-pull signal adjustment unit 20 gradually changes the balance coefficient k so that the top difference value DT ≧ 0 and the bottom difference value DB ≦ 0, or the top difference value DT ≦ 0 and the bottom difference value DB ≧ 0. As a result, is the difference between the virtual inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co small as shown in FIG. 4 (A), FIG. 4 (B) or FIG. 3 (B)? Since both can be made to be in substantially the same state, the balance coefficient k can be changed to an appropriate and appropriate balance coefficient k for the optical disk 50 loaded, and an appropriate differential push-pull can be made using the balance coefficient k. The signal DPP can be adjusted.

  In response to this, the optical disk apparatus 10 can perform normal tracking control by the servo control unit 11 based on the appropriately adjusted differential push-pull signal DPP.

  At this time, the differential push-pull signal adjustment unit 20 determines whether the difference between the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is slight when the sign of the top difference value DT or the bottom difference value DB changes. Since it is considered that they are almost in agreement with each other, it is not necessary to repeat the change of the balance coefficient k until the inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co are completely matched. The balance coefficient k can be set with as few changes as possible, that is, in the shortest possible time.

  Furthermore, since the differential push-pull signal adjustment unit 20 can end the change of the balance coefficient k at the time when either one of the codes changes first for both the top difference value DT and the bottom difference value DB, There is a high possibility that the number of times of changing the balance coefficient k can be reduced as compared with the case where the change of the sign is detected for only one of the top difference value DT or the bottom difference value DB.

  In addition, the differential push-pull signal adjustment unit 20 has the top difference value DT and the bottom difference value DB at the time when the top difference value DT and the bottom difference value DB are calculated for the first time, or at least one of the values is 0. In this case, it can be considered that the balance coefficient k has already been appropriately set for the loaded optical disk 50 (step SP5), so that unnecessary change of the balance coefficient k takes time. It can be omitted.

  According to the above configuration, the differential push-pull signal adjustment unit 20 of the optical disc apparatus 10 temporarily stops the tracking control when a new optical disc 50 is loaded, and then moves the objective lens 12B of the optical pickup 12 to the objective lens 12B. The top difference value DT and the bottom difference value DB are calculated based on the differential push-pull signal DPP when forcedly moved to the inner periphery side and the outer periphery side, and the signs of the top difference value DT and the bottom difference value DB are When both are positive or both negative, the balance coefficient adjustment loop is repeated, and when the sign of the top difference value DT and the bottom difference value DB is different from each other or at least one value becomes 0, the value of the balance coefficient k is set. By confirming, the difference between the virtual inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is slight or can be brought into a state in which both are substantially the same. Runode, can be adjusted as quickly as possible a sufficiently proper balance coefficients k required for the loaded optical disk 50, it can be adjusted to an appropriate differential push-pull signal DPP.

(5) Other Embodiments In the above-described embodiment, when the change of the balance coefficient k is terminated when either one of the top difference value DT and the bottom difference value DB changes. However, the present invention is not limited to this, and the difference value with the smaller absolute value before and after the change of one of the signs and the difference value with the smaller absolute value before and after the change of the other sign And the balance coefficient k having the smaller absolute value may be used.

  For example, as illustrated in FIG. 7, the bottom difference value DB1 having a smaller absolute value among the bottom difference values DB1 and DB2 in the balance coefficients k20 and k22 before and after the sign of the bottom difference value DB is changed, and the sign of the top difference value DT are The top difference values DT1 and DT2 in the balance coefficients k12 and k14 before and after the change are compared with the top difference value DT2 having a small absolute value, and the balance coefficient k14 that takes the top difference value DT2 having the small absolute value is determined as an appropriate balance coefficient. Used as k.

  Thereby, although it takes time as compared with the above-described embodiment, the absolute value of the difference value becomes smaller, that is, the difference between the virtual inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is further increased. The balance coefficient k can be changed to a small value.

  Further, in the above-described embodiment, the case where the change of the balance coefficient k is finished when one of the top difference value DT and the bottom difference value DB changes has been described. Not limited to this, the balance coefficient k having a smaller absolute value of the difference value before and after the change of one sign and the balance coefficient k having a smaller absolute value of the difference value before and after the change of the other sign. A balance coefficient k composed of values may be used.

  For example, in FIG. 7, the balance coefficient k20 that takes the bottom difference value DB1 having a small absolute value among the bottom difference values DB1 and DB2 in the balance coefficients k20 and k22 before and after the sign of the bottom difference value DB changes, and the top difference value DT The balance coefficient k17 that is the midpoint of the balance coefficient k14 that takes the top difference value DT2 having a small absolute value among the top difference values DT1 and DT2 in the balance coefficients k12 and k14 before and after the sign change is used. As a result, the balance coefficient k can be changed such that the difference between the virtual inner circumference side amplitude center value Ci and the outer circumference side amplitude center value Co is remarkably reduced.

  Furthermore, in the above-described embodiment, the balance coefficient k is increased or decreased by each change value α [dB], and the balance coefficient k is changed when one of the top difference value DT and the bottom difference value DB changes. Although the case where the change is finished has been described, the present invention is not limited to this, and when the sign of one of the top difference value DT and the bottom difference value DB changes, the balance coefficient k is changed to the change value. When it is increased by α [dB], it is finally decreased by α / 2 [dB]. When the balance coefficient k is decreased by the change value α [dB], finally α / 2 [dB] ] May be increased.

  For example, in FIG. 7, when the balance coefficient k is decreased by k24, k22, k20 and the change value α [dB], the balance coefficient k20 to α is changed when the sign of the bottom difference value DB changes in the balance coefficient k20. The balance coefficient is changed to k21 increased by / 2 [dB]. When the balance coefficient k is increased by k10, k12, and k14 and the change value α [dB], the balance coefficient k14 is changed from the balance coefficient k14 to α / 2 [dB] when the sign of the top difference value DT changes. ] Is changed to the balance coefficient k13 that is decreased by the same amount.

  As a result, the balance coefficient k21 and the top difference value DT which are likely to be closer to the balance coefficient kb where the bottom difference value DB intersects the balance coefficient k axis in FIG. 7 is closer to the balance coefficient k20. A balance coefficient k13 that is likely to be closer to the balance coefficient kt intersecting the axis than the balance coefficient k14 can be used as an appropriate balance coefficient k.

  Further, in the above-described embodiment, the case where the differential push-pull signal DPP is adjusted with respect to the optical disc 50 having only one signal recording layer has been described. However, the present invention is not limited to this, and the signal recording is performed. For an optical disc 50 having two or more layers, an appropriate balance coefficient k is set in each signal recording layer, and the differential push-pull signal DPP is adjusted by using a different balance coefficient k for each signal recording layer. Control may be performed.

  Further, in the above-described embodiment, a case has been described in which the balance coefficient k is changed to the appropriate balance coefficient k by changing the change value α [dB] in increments. The relationship between the balance coefficient k, the top difference value DT, and the bottom difference value DB (that is, the relationship shown in FIGS. 6 and 7) is stored in advance in the nonvolatile memory 27 in the form of a table or the like. Anyway. In this case, first, the top difference value DT and the bottom difference value DB are calculated only once using the reference balance coefficient kr, and the optimum value of the balance coefficient k may be calculated using the table. The time required for changing k can be greatly reduced.

  Furthermore, in the above-described embodiment, a case has been described in which it is determined whether or not the sign has changed for both the top difference value DT and the bottom difference value DB after changing the balance coefficient k. However, the present invention is not limited to this, and it may be determined whether or not the sign has changed by focusing on only one of the top difference value DT and the bottom difference value DB.

  Furthermore, in the above-described embodiment, the case where the balance coefficient k is adjusted by a constant change value α [dB] has been described. However, the present invention is not limited to this, for example, the top difference value DT and the bottom difference value. The change value α [dB] may be changed according to the DB value.

  Further, in the above-described embodiment, the case where the present invention is applied to the optical disc apparatus 10 corresponding to the optical disc 50 made of the Blu-ray Disc (trademark) has been described. However, the present invention is not limited to this, and a CD (Compact Disc), You may make it apply this invention to the various optical disk apparatus which can move the objective lens of an optical pick-up corresponding to various optical disks, such as DVD (Digital Versatile Disc), in a tracking direction.

  Further, in the above-described embodiment, the subtracter 22 as the push-pull signal generation unit, the difference value calculation unit 24 as the envelope value generation unit and the difference value calculation unit, the adjustment control unit 21 as the control unit, the sign determination Although the case where the differential push-pull signal adjustment unit 20 as the differential push-pull signal adjustment device is configured by the unit 25 and the balance coefficient setting unit 26 has been described, the present invention is not limited thereto, and other various circuit configurations are used. The push-pull signal generation unit, the envelope value generation unit, the difference value calculation unit, and the control unit may constitute a differential push-pull signal adjustment device.

  The present invention can also be used in various optical disk devices that can move the objective lens in the tracking direction.

1 is a schematic block diagram showing a configuration of an optical disc apparatus according to the present invention. It is a basic diagram which shows the example of a differential push pull signal when an optical disk has eccentricity. It is an approximate signal waveform figure showing relation (1) of a movement of an objective lens, and a differential push pull signal. FIG. 10 is a schematic signal waveform diagram showing a relationship (2) between the movement of the objective lens and the differential push-pull signal. It is a flowchart which shows a differential push pull signal adjustment process procedure. It is a basic diagram which shows the relationship between a balance coefficient and a difference value. It is a basic diagram which shows the relationship between the balance coefficient and difference value by other embodiment. It is a basic diagram with which it uses for description of the production | generation of the conventional differential push pull signal.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Differential push-pull signal generation part, 9 ... Subtraction part, 10 ... Optical disk apparatus, 11 ... Servo control part, 12 ... Optical pick-up, 12A ... Biaxial actuator, 12B ... Objective lens, 20 …… Differential push-pull signal generation unit, 21 …… Adjustment control unit, 22 …… Subtraction unit, 24 …… Difference value calculation unit, 25 …… Sign determination unit, 26 …… Balance coefficient setting unit, 27 …… Non-volatile Memory, 50 ... Optical disc, MPP ... Main push-pull signal, SPP ... Side push-pull signal, DPP ... Differential push-pull signal, k ... Balance factor, DT ... Top difference value, DB ... Bottom difference value.

Claims (11)

A light beam is transmitted through an objective lens that can move in a proximity direction or a separation direction with respect to the optical disc with respect to a desired track formed on a signal recording layer of the optical disc and can move in an inner circumferential direction or an outer circumferential direction of the optical disc. Eccentricity of the optical disc for performing tracking control for moving the objective lens in the inner circumferential direction or the outer circumferential direction of the optical disc using a plurality of reflected signals based on the reflected light when irradiated and a predetermined ratio coefficient A push-pull signal generating means for generating a differential push-pull signal having a substantially sinusoidal shape,
An envelope value for generating an envelope value of each differential push-pull signal in the inner peripheral state in which the objective lens moves in the inner peripheral direction of the optical disc and in the outer peripheral state in which the objective lens moves in the outer peripheral direction of the optical disc Generating means;
Difference value calculating means for calculating a difference value by subtracting the envelope value of the outer peripheral side state from the envelope value of the inner peripheral side state;
When the difference value is positive or negative, the differential push-pull signal generated next time is changed by decreasing or increasing the ratio coefficient by a predetermined change amount, and the sign of the difference value changes from the previous time or A differential push-pull signal adjustment device comprising: control means for determining the ratio coefficient when the difference value becomes 0 and not changing the differential push-pull signal generated next time. The envelope value generating means includes
In the inner peripheral side state and the outer peripheral side state, respectively, a top envelope value or a bottom envelope value of the differential push-pull signal is generated,
The difference value calculating means includes:
The difference value is calculated by subtracting the top envelope value or the bottom envelope value in the outer peripheral state from the top envelope value or the bottom envelope value in the inner peripheral state. The differential push-pull signal adjustment device described. The envelope value generating means includes
In the inner peripheral state and the outer peripheral state, a top envelope value and a bottom envelope value of the differential push-pull signal are respectively generated,
The difference value calculating means includes:
A top difference value and a bottom difference value are respectively calculated by subtracting the top envelope value and the bottom envelope value of the outer peripheral side state from the top envelope value and the bottom envelope value of the inner peripheral side state, respectively.
The control means includes
When the sign of the top difference value and the bottom difference value is both positive or negative, the differential push-pull signal to be generated next time is changed by decreasing or increasing the ratio coefficient by a predetermined change amount, and the top difference When the sign of one of the value and the bottom difference value is positive and the other sign is negative, or when at least one of the top difference value or the bottom difference value is 0, the ratio coefficient is determined and next time The differential push-pull signal adjustment apparatus according to claim 1, wherein the differential push-pull signal to be generated is not changed. The control means includes
The differential push-pull signal adjustment device according to claim 1, wherein the amount of change of the ratio coefficient is changed according to the magnitude of the difference value. The control means includes
The differential push-pull signal adjustment device according to claim 1, wherein when the optical disc has a plurality of signal recording layers, the change amount of the ratio coefficient is changed for each signal recording layer. The control means includes
If the difference value is positive or negative, the change of the ratio coefficient by the change amount is decreased or increased, so that when the sign of the difference value changes or becomes zero, the change is smaller than the change amount. The differential push-pull signal conditioner according to claim 1, wherein the ratio coefficient is increased or decreased by an amount. The control means includes
A reference coefficient adjusted in advance using a predetermined reference optical disk is stored in a predetermined storage means, and a characteristic curve representing a relationship between the difference value and the ratio coefficient is stored in the storage means. The differential push-pull signal adjustment device according to claim 1, wherein the coefficient is read out and used as an initial value of the ratio coefficient, and the ratio coefficient is directly calculated based on the characteristic curve according to the difference value. . The control means includes
The differential push-pull signal that is different for each signal recording layer is adjusted by changing the ratio coefficient for each signal recording layer when the optical disc has a plurality of signal recording layers. The differential push-pull signal conditioner described in 1. The control means includes
For each signal recording layer in a plurality of types of optical discs having different numbers of signal recording layers, each reference coefficient adjusted in advance using a plurality of types of reference optical discs corresponding to the plurality of types of optical discs is stored in a predetermined storage means. The differential push-pull signal adjustment device according to claim 1, wherein the differential push-pull signal adjustment device is stored and each stored reference coefficient is used as an initial value of the ratio coefficient. A light beam is transmitted through an objective lens that can move in a proximity direction or a separation direction with respect to the optical disc with respect to a desired track formed on a signal recording layer of the optical disc and can move in an inner circumferential direction or an outer circumferential direction of the optical disc. Eccentricity of the optical disc for performing tracking control for moving the objective lens in the inner circumferential direction or the outer circumferential direction of the optical disc using a plurality of reflected signals based on the reflected light when irradiated and a predetermined ratio coefficient A push-pull signal generation step for generating a differential push-pull signal having a substantially sinusoidal shape,
An envelope value for generating an envelope value of each differential push-pull signal in the inner peripheral state in which the objective lens moves in the inner peripheral direction of the optical disc and in the outer peripheral state in which the objective lens moves in the outer peripheral direction of the optical disc Generation step;
A difference value calculating step of calculating a difference value by subtracting the envelope value of the outer peripheral side state from the envelope value of the inner peripheral side state;
When the difference value is positive or negative, the differential push-pull signal generated next time is changed by decreasing or increasing the ratio coefficient by a predetermined change amount, and the sign of the difference value changes from the previous time or A differential push-pull signal adjustment method, comprising: a step of determining the ratio coefficient when the difference value becomes 0 and not changing the differential push-pull signal generated next time. A light beam is transmitted through an objective lens that can move in a proximity direction or a separation direction with respect to the optical disc with respect to a desired track formed on a signal recording layer of the optical disc and can move in an inner circumferential direction or an outer circumferential direction of the optical disc. Push-pull signal generation means for generating a differential push-pull signal having a substantially sinusoidal shape due to the eccentricity of the optical disc, using a plurality of reflected signals based on the reflected light when irradiated and a predetermined ratio coefficient;
An envelope value for generating an envelope value of each differential push-pull signal in the inner peripheral state in which the objective lens moves in the inner peripheral direction of the optical disc and in the outer peripheral state in which the objective lens moves in the outer peripheral direction of the optical disc Generating means;
Difference value calculating means for calculating a difference value by subtracting the envelope value of the outer peripheral side state from the envelope value of the inner peripheral side state;
When the difference value is positive or negative, the differential push-pull signal generated next time is changed by decreasing or increasing the ratio coefficient by a predetermined change amount, and the sign of the difference value changes from the previous time or Control means for determining the ratio coefficient when the difference value becomes 0 and not changing the differential push-pull signal to be generated next time;
An optical disc apparatus comprising: tracking control means for performing tracking control for moving the objective lens in an inner circumferential direction or an outer circumferential direction of the optical disc based on the differential push-pull signal.

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