JP2001084599A - Optical disk drive - Google Patents

Abstract

(57) [Summary] [Problem] To stably perform a focus jump from a current recording layer to a designated recording layer. SOLUTION: An objective lens 2 for forming a spot on an arbitrary recording layer of an optical disk 1 having a plurality of recording layers, a focus error detection for detecting a focus error signal based on reflected light from the spot and generating a focus error control signal. Means 6, driving means 3 for driving the objective lens based on the focus error control signal, holding means 12 for holding the focus error control signal, additional means for performing a focus jump from the first recording layer to the second recording layer of the optical disc. An acceleration / deceleration pulse generating means 14 for generating a deceleration pulse is provided.
The drive unit is driven based on the sum of the output of the hold unit and the output of the acceleration / deceleration pulse generation unit, and the application timing of the acceleration pulse and the deceleration pulse is determined based on the focus error signal during the focus jump.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk having a plurality of recording layers stacked, for example, an optical disk device having a focus jump function in a DVD.

[0002]

2. Description of the Related Art Numerous devices have been filed for reproducing an arbitrary recording layer in an optical disk having a multilayer recording layer such as a DVD. For example, JP-A-10-12488
Japanese Patent Application Laid-Open No. 3 (1999) -1995 describes a method of jumping from a recording layer currently under focus control to an arbitrary recording layer (hereinafter referred to as a focus jump). FIG.
2 shows a block diagram of the focus jump device. This is a configuration in which functional blocks necessary for focus jump are added to a general focus control loop. During the focus jump, the focus control loop is turned off by the changeover switch 9 for selecting the focus jump provided after the phase compensation block 8, and the focus position of the light spot is moved from the current layer to the target layer instead of the focus control signal. The acceleration / deceleration signal of the focus actuator to be applied is applied. The acceleration / deceleration signal is composed of an acceleration pulse for the focus actuator to escape from the current layer and a deceleration pulse for bringing the target layer to a focusable position.

In FIG. 1, reference numeral 0 denotes a light emitting optical system including a semiconductor LD, 1 denotes, for example, a two-layer DVD (hereinafter abbreviated as DVD-DL) disk, 2 denotes an objective lens, and 3 denotes a rigid body connected to the objective lens 2 and is installed in a magnetic circuit. Focus actuator driving coil, 4 is a half mirror, 5 is a photoelectric conversion element, 6 is a focus error detection block, 8 is a phase compensation block, 9 is a changeover switch, 10 is a driver amplifier, and 11 is a low-pass filter block (hereinafter, an LPF block). , 13 is an addition block, and 14 is an acceleration / deceleration pulse generation block. Function block numbers 1 to 6,
8 and 10 are general configurations of a focus control loop, in which functional blocks 9, 11, 13, and 14 are added to realize a focus jump.

Hereinafter, a brief description will be given of general focus control. In order to reproduce information recorded on the information recording layer of the disk 1, the laser light emitted from the light emitting optical system 0 must always be focused on the information recording layer of the disk 1 by the objective lens 2. . In order to realize this, it is necessary to control the position of the objective lens 2 at a predetermined relative position with respect to the disk 1. The disk 1 has warpage, and its absolute amount is ± 3 in the case of the DVD standard, for example.
It is standardized to not more than 00 μm. Since the disk 1 rotates, the disk 1 moves up and down due to the warp of the disk 1 (hereinafter referred to as "surface run-out"), so that tracking control of the objective lens 2 is essential. In this case, the control object is the objective lens 2
The tracking target is the information recording layer of the disk 1 and the control type is relative position control with respect to the disk 1. Position control of the objective lens 2 is realized by feeding back a signal based on a relative position error signal between the objective lens 2 and the disk 1 to a driving unit of the objective lens 2. The above-described configuration requires a means for detecting a relative position with respect to the disk 1 (functional block numbers 1, 2, 4, and 5) and an error between the relative position and a predetermined relative position (hereinafter referred to as Focus Error Si).
gnal: abbreviated as FES) (functional block number 6: focus error detection block 6);
Phase compensating means (functional block number 8: phase compensating block 8) for stabilizing the position control loop, and driving means (functional block number 3: driving coil 3) for changing the position of the objective lens 2 to be controlled. The phase compensation block 8 is generally formed of a phase lead filter for advancing the phase of a band near 1 KHz. The drive coil 3 is rigidly connected to the objective lens 2 and has a function of moving the objective lens 2 in a direction perpendicular to the disk 1 by applying a drive current to the drive coil 3. A control system in which the drive current is controlled by a focus control signal output from the phase compensation block 8 and the laser light is focused on the information recording layer of the disk 1 is realized.

Next, a conventional focus jump method will be described. The signal applied to the drive coil 3 at the time of the focus jump is defined by the sum of the surface shake compensation signal output from the LPF block 11 and the output from the acceleration / deceleration pulse generation block 14. The addition of the two signals is performed by the addition block 13. The state transition between the focus control state and the focus jump state is controlled by selecting the focus control signal and the focus jump signal output from the phase compensation block 8 with the selection switch 9.

The LPF block 11 has a cutoff frequency higher than the disk rotation frequency, and has a function of extracting only the disk surface shake component of the focus control signal. Further, the acceleration / deceleration pulse generation block 14 generates an acceleration pulse, which is a rectangular wave for acceleration, and a deceleration pulse, which is a rectangular wave for deceleration, and switches timing from the acceleration pulse to the deceleration pulse by the zero cross timing of the FES during the focus jump. I do. The deceleration pulse end timing is when the FES is in focus, and at the same time, the changeover switch 9 is switched to focus control, and if the focus pull-in operation is completed, the focus jump ends.

[0007]

A necessary condition for realizing a stable and reliable focus jump can be defined by whether or not the pull-in of the focus control loop immediately after the focus jump operation is normally performed. Conditions for stably pulling the focus control loop are that the FES for the target layer at the time of the pulling operation is close to zero,
And the relative speed between the lens and the objective lens 2 is close to zero. Conversely, condition 1. FES after jump operation is zero. Condition 2. The relative speed between the objective lens 2 and the disc 1 after the jump operation is zero (hereinafter, abbreviated as the relative speed after the jump). If it can be set to, a stable and reliable focus jump will be realized.

FIG. 10 summarizes description problems to be overcome to realize a focus jump. The contents of FIG. Since the position detection signal is lost during the focus jump, open loop control is performed. Reason: Since the FES detection range (usually about 7 μm) is narrower than the interlayer distance (usually about 40 μm), there is a focus error dead zone during jumping. During the dead zone during jumping, open loop control is performed. Countermeasures because the target disk has runout. Reason: The relative position and the relative speed between the disk 1 and the objective lens 2 change due to the surface fluctuation even during the focus jump. Therefore, if the jump is performed without considering the disk surface fluctuation, the condition 1, especially the condition 2 may be satisfied. difficult.

For example, the above-mentioned conventional focus jump method is limited to a pickup having no dead zone, and is different from a general pickup. Furthermore, although the conventional example has a countermeasure against runout, the non-linear FES during the jump is L
Since it is input as a disturbance to the PF block 11, it cannot be said that the signal is complete, and as a result, there is a problem that the surface shake interpolation signal is affected. Further, in the related art, since the acceleration / deceleration pulse which is the output of the acceleration / deceleration pulse generation block is set by paying attention only to the FES position, zero speed in Condition 2 cannot be guaranteed. Therefore, at the time of focus pull-in after the focus jump, there is a problem that overshooting takes time for signal reading, and in the worst case, the focus pull-in fails.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide an optical disk apparatus capable of realizing a stable focus jump even on an optical disk having a large surface deflection. Still another object of the present invention is to provide an optical disk device capable of reducing the influence on a change in reproduction speed and realizing a stable focus jump.

[0011]

An optical disk device according to the present invention is an optical disk device for optically reproducing information recorded on an optical disk having a plurality of recording layers or optically recording information on the optical disk. An objective lens capable of forming a focused spot on any recording layer of the optical disc, and a focus error detection unit that detects a focus error signal based on light reflected from the focused spot and generates a focus error control signal; A driving unit that drives the objective lens based on the focus error control signal, a holding unit that holds the focus error control signal, and a focus jump from a first recording layer to a second recording layer of the optical disc. An acceleration / deceleration pulse generating means for generating an acceleration / deceleration pulse; Receiving the signal, drives the driving means based on the sum of the output of the holding means and the output of the acceleration / deceleration pulse generating means, and applies an acceleration pulse and a deceleration pulse based on a focus error signal during a focus jump. The timing is determined.

[0012] The optical disk apparatus according to the present invention is characterized in that the holding means is a zero-order hold for holding a value of the focus error control signal at the time of holding.

[0013] The optical disk apparatus according to the present invention is characterized in that the holding means is a primary hold for holding a value and an inclination of the focus error control signal at the time of holding.

[0014] An optical disk apparatus according to the present invention is characterized in that a low-pass filter is disposed in front of the holding means.

An optical disk apparatus according to the present invention is characterized in that the acceleration pulse and the deceleration pulse generated by the acceleration / deceleration pulse generating means are given so that the impulse thereof becomes zero.

The optical disk apparatus according to the present invention is characterized in that the acceleration pulse generated by the acceleration / deceleration pulse generating means is given as an end timing when the focus error signal reaches a first threshold value, After the focus error signal has passed through the zero cross point, the time when the second threshold value is reached is given as the start timing.

An optical disk device according to the present invention is characterized in that the first and second threshold values are determined based on sensitivity characteristics of the driving means.

In the optical disc apparatus according to the present invention, the holding means may be a zero-order hold for holding the value of the focus error control signal at the time of holding, and a holding means for holding the value and inclination of the focus error control signal at the time of holding. A next hold is provided, and these are switched according to the reproduction speed of the optical disk.

An optical disk apparatus according to the present invention is characterized in that the acceleration / deceleration pulse generating means generates a corrected acceleration / deceleration pulse subsequent to the acceleration / deceleration pulse.

In the optical disc apparatus according to the present invention, the correction acceleration pulse is applied for a period until a residual focus error signal, which is a focus error signal after the application of the acceleration / deceleration pulse, reaches a predetermined value, and the correction deceleration pulse is applied. After the correction acceleration pulse is applied, the correction acceleration pulse is applied during the same period as the above period.

The optical disk apparatus according to the present invention is characterized in that the application timing, application time, and application amplitude of the acceleration / deceleration pulse are set based on the shape of the S curve of the focus error signal.

An optical disk apparatus according to the present invention is characterized in that the application amplitude and application time of the deceleration pulse are set based on the ratio between the positive period and the negative period of the focus error signal.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A focus jump requires a function of jumping from a current layer currently under focus control to a target layer and instantly performing focus control on the target layer. This is, from the perspective of the focus control loop,
This is a special mode in which the focus control loop is completely cut during the focus jump, and the focus control loop is closed immediately after the jump. That is, since the FES signal is lost during a jump, it is equivalent to a stable focus pull-in after the jump.
It can be understood that a plane-runout interpolation signal instead of the FES signal is required so that the disc-runout can be followed during the jump period.

Therefore, the focus jump signal supplied to the drive coil 3 at the time of the jump includes a plane deviation interpolation signal for following and interpolating the plane deviation during the jump period and a stop speed for stopping the distance between the current layer and the target layer. What is necessary is just to define by the sum with the acceleration / deceleration pulse moved by zero. Hereinafter, the surface deflection interpolation signal and the acceleration / deceleration pulse will be described in detail.

1. Plane runout interpolation signal Let's theoretically describe a plane runout interpolation signal that has the function of following the plane runout regardless of the FES signal during a focus jump. The surface run-out, which is a tracking target, is a periodic function because it occurs when the warped disk rotates as described above. Here, for the sake of simplicity, the runout is defined by a sine wave of the following equation.

(Equation 1)

Here, t is time, X (t) is plane runout, A is plane runout amplitude (m), and B is angular velocity (rad / se) of plane runout.
c). Assuming that the mechanical dynamic characteristic of the focus actuator including the drive coil 3 to be controlled is a secondary system,
Further, a hold period of a function obtained by performing second-order differentiation of X (t) during the focus jump (that is, equivalent to a signal applied to the drive coil 3) is defined as Δ (sec). An error between the hold value and the true value of X (t) after the hold period Δ is defined at each time as a function defined as a result of the hold error function. X (t) is a function obtained by differentiating the second order, that is, the hold of the signal applied to the drive coil 3 includes a zero-order hold for holding the value of the signal at the time of holding, and the value and slope of the signal at the time of holding (change of the signal with time). ) Is held. The error function for the zero-order hold is E0,1
If the error function for the next hold is defined as E1, they can be expressed by the following equations.

(Equation 2)

(Equation 3)

It is apparent from the above two equations that the error function is defined by a time function using the surface runout amplitude A, the surface runout angular velocity B, and the hold period Δ as parameters. Therefore, to discuss the hold error, what values of the above parameters depending on the conditions of use of the system,
As a result, it turns out that it is meaningless without specific numerical values such as how much the error is. For example, the playback disk is DVD-DL, the playback speed is the innermost circumference of 4 × CLV playback, the jump period (= hold period) is 1 msec,
FIG. 7 shows the relationship between the disk surface deflection X (t) and the hold error function when the disk surface deflection amplitude is set to the standard limit of 300 μm (half-wave amplitude). In the figure, waveform A is X
(T), the amplitude is displayed on a 1/10 scale, waveform B is E0, and waveform C is E1. In the case of this condition, surface runout 30
For 0 μm, the maximum hold error is about 13 μm for the zero-order hold and about 2 μm for the first-order hold.

As described above, the error function is the surface runout amplitude A,
8 and 9 show the results when Δ and B are made small with respect to the condition analyzed in FIG. 7 because the angular function is defined by a time function using the surface runout angular velocity B and the hold period Δ as parameters.

FIG. 8A shows an analysis result under the same conditions as in FIG.
FIG. 3B shows that the jump period is from 1 ms to 0.8 ms.
ec is an analysis result set to be small. If Δ is reduced, the amplitude of both error functions EO and E1 is reduced. From this, it is understood that the hold error can be reduced by shortening the jump period.

FIG. 9A shows an analysis result under the same conditions as in FIG.
FIG. 7B shows the analysis result when the reproduction speed is set to a low speed from 4 × speed to 3 × speed. If B is reduced, the error function E
Both O and E1 have small amplitudes. From this, it is understood that the hold error can be reduced by reducing the reproduction speed.

From the above, it can be seen that the hold error has a characteristic that, even when the amplitude of the runout is constant, the value greatly changes depending on the jump period and the reproduction speed, and the error increases as the reproduction speed increases and the jump period increases. ing. In order to discuss more qualitatively, the surface deflection amplitude is set to the DVD-DL standard limit of 300 μm (half-wave amplitude), and the playback speed is increased to 4 × speed (CL
V: the maximum value of the error function amplitude (half-wave amplitude) when the jump period (= Δ) is used as a parameter when V is the innermost circumference
2 shows the results of analyzing. FIG. 11 shows the result of analysis under the above conditions. In the figure, the solid line indicates the maximum position error of the zero-order hold, the small dotted line indicates the maximum position error of the first-order hold, and the dotted line indicates the FES detection limit. The FES has a physically limited detection dynamic range, and is 10 μm or less in a general pickup. Here, the FES detection limit is 10 μm. Therefore, the maximum position error due to hold is FES
If the detection limit is exceeded, FES detection becomes impossible during focus pull-in after holding, and the focus pull-in fails, which must be avoided.

As has been clarified, it can be seen from the figure that the maximum position error due to the hold becomes larger as the jump period becomes longer, and the amount of the maximum position error is smaller in the first-order hold than in the zero-order hold.

FIG. 12 shows the case where the variable speed is changed not only in the jump period but also in the reproduction speed from 1 to 4 times.
7 shows an analysis result of a maximum position error in a zero-order hold.
From this figure, the following is derived to make the maximum position error less than the FES detection limit.・ If the playback speed exceeds 2 times, the jump period will be 1.8m
It must be less than sec. -The higher the playback speed, the shorter the jump period needs to be.

FIG. 13 shows the case where the variable parameter is changed not only in the jump period but also in the reproduction speed from 1 to 4 times.
4 shows an analysis result of a maximum position error in the primary hold.
From this figure, the following is derived to make the maximum position error less than the FES detection limit. -Even if the playback speed exceeds 3 times, the jump period will be 2 mse
It does not need to be less than c. -Even if the playback speed is quadrupled, the jump period will be 1 mse
There is no problem if it is set to c or less.

From the above results, it can be seen that as a measure against surface runout during the focus jump period, the problem can be solved by holding the drive signal of the drive coil 3. It can be seen that the zero-order hold is sufficient when the reproduction speed is low, such as for a player, and that the primary hold is used when the reproduction speed is high, such as for a ROM for a computer.

2. Acceleration / deceleration pulse It is assumed that the mechanical dynamic characteristic of the focus actuator including the drive coil 3 to be controlled is a secondary system. Assuming that the position of the objective lens 2 is x (t), the velocity of the objective lens 2 is represented by the time derivative of the position, and the acceleration is represented by the second derivative of the position.
It is as follows.

(Equation 4)

The drive coil 3 has a function of converting an applied signal (applied current) into an actuator driving force (acceleration). Since the force / current characteristic is proportional, the applied signal can be described in terms of acceleration.

FIG. 14 shows a driving coil 3 (= objective lens 2).
3 shows the relationship between the velocity and the position with respect to the applied signal (acceleration). In the figure, (A) shows acceleration, (B) shows speed, and (C) shows position. When the acceleration pulse of the applied signal is a rectangular wave as shown in FIG. 3A, the velocity becomes a linear function and the position becomes a quadratic function. If the acceleration pulse and the deceleration pulse have opposite polarities and the impulse (acceleration * time) is made equal, the speed after application of the deceleration pulse can be guaranteed to be zero.

Next, the above will be proved. The initial speed of the drive coil 3 is set to zero. At this time, the behavior when the rectangular wave acceleration pulse is applied is as follows. Acceleration to height A,
During the period B, the speed becomes a linear function of the slope A,
The rest is AB. That is, in this case, the speed is represented by the product (impulse) of the magnitude A of the acceleration and the acceleration time B. During the zero period after the acceleration pulse, the acceleration becomes zero, and the speed AB is maintained. As for the condition of the deceleration pulse for setting the speed AB to zero, it is understood that the speed after application of the deceleration pulse is always zero if the impulse is reversed and the impulse is made equal.

Embodiments corresponding to various cases based on the above analysis results will be described below.

Embodiment 1 This embodiment describes an application example in a player application where the reproduction speed is not high. FIG. 1 shows a block diagram of this embodiment. In FIG. 1, 7 is a focus control loop switch provided before the phase compensation block 8, 12 is a hold block, and 14 is an acceleration / deceleration pulse generation block. In the figure, the other components are the same as the blocks described in the conventional example, so the description thereof will be omitted, and the operation of the new functional blocks 7, 12, and 14 will be briefly described.

In the conventional example shown in FIG. 23, the FES during the focus jump is input to the phase compensation block 8, the output of the phase compensation block 8 is input to the LPF 11, and the LPF 11
The output was a surface shake correction signal. However, the FES during the focus jump is non-linear, and an FES dead zone may occur depending on the optical system of the pickup. For example, the vertical amplitude of the S curve is asymmetric,
If there is an unnecessary knob, this becomes a disturbance and LPF
The output result of No. 11 is disturbed. The present invention shown in FIG. 1 solves this problem. During the focus jump period, the acceleration / deceleration pulse generation block 14 includes a focus control loop switch 7 provided before the phase compensation block 8.
And the non-linear FES during the focus jump is not transmitted to the subsequent surface shake correction signal generation stages (11, 12).

Further, since the surface shake correction signal during the jump period is generated by the hold block 12, the configuration is such that the error due to the surface shake can be reduced as shown in the above analysis. The hold block 12 is not particularly limited, but is a zero-order hold having a simple configuration here. In this case, the analysis shows that the application is limited to applications having a low reproduction speed, such as a DVD player.

The ON / OFF of the focus control loop switch 7 and the hold of the hold block 12 in the focus jump are controlled by the acceleration / deceleration pulse generation block 14. When receiving a focus jump command from the host device, the block creates acceleration / deceleration pulse switching timing based on the FES. Acceleration / deceleration pulses are output as acceleration mode, zero period,
It has three deceleration pulses, each pulse is a rectangular wave, and makes a state transition in the order of an acceleration pulse, a zero period, and a deceleration pulse. Further, the acceleration pulse and the deceleration pulse have opposite polarities and the impulse is set equal (see FIG. 14). The generation of the acceleration / deceleration pulse switching timing will be described below.

FIG. 15 shows a problem that occurs when the acceleration / deceleration pulse switching timing is set to a fixed value. A in the figure is an acceleration / deceleration pulse as an applied pulse,
The focus actuator having the average current sensitivity is set to move the interlayer distance by 40 μm. C indicates a focus actuator position. The solid line of C is a waveform at the average current sensitivity value of the focus actuator. The current sensitivity of the actual focus actuator always has some variation, and is generally about ± 3 dB with respect to the average value. In this case, the variation in the actuator position caused by the driving with the acceleration / deceleration pulse of A is in the range indicated by the broken line in FIG. The position variation due to this current sensitivity variation is ± 16μ
m, which is wider than the inrush layer FES detection limit ± 10 μm, so that the focus pull-in after the jump may fail.

In the present invention, in order to solve this problem, the state transition timing of the acceleration / deceleration pulse is determined based on the FES during the jump operation. FIG. 16 shows the state transition timing of the acceleration / deceleration pulse of the present invention. In the figure, A indicates the focus actuator position, B indicates the FES, and C indicates the acceleration / deceleration pulse. As shown in B, a value having hysteresis from the FES zero point is defined as an acceleration pulse end threshold, and a value having hysteresis of a polarity opposite to the acceleration pulse end threshold is similarly defined as a deceleration pulse start threshold. The acceleration pulse is applied immediately after the jump command, and its termination timing is set at the time when the FES becomes equal to or less than the acceleration pulse termination threshold. At the end of the acceleration pulse, a zero period, which is zero output, is reached. When the FES falls below the deceleration pulse start threshold, the application of the deceleration pulse is started, and the end of the deceleration pulse is set at a timing when the acceleration pulse and the impulse absolute value are equal. . In this way, regardless of the actuator current sensitivity, escape from the current layer is guaranteed by the acceleration pulse,
Further, it is ensured that the application timing of the deceleration pulse is near the target layer. As shown in the figure, even if the actuator current sensitivity varies, it is possible to move to a predetermined target position without a positional error, and to further reduce the speed after the movement to zero.

Here, it is assumed that the positive and negative waveform characteristics of the FES are equal. In this case, the absolute values of the acceleration pulse end threshold and the deceleration pulse start threshold are set equal, and
If the pulse height absolute values of the acceleration pulse and the deceleration pulse are set equal, the position error after the movement can be made zero.

Under the above conditions, since the above-mentioned two conditions for stably achieving the focus jump are satisfied, a reliable focus jump can be realized.

Embodiment 2 In the first embodiment, the example in which the hold at zero is used for the disk surface deflection interpolation has been described. However, this is an example effective for a player whose disk reproduction speed is about 1 × speed. In the second embodiment, a system that can be used for a ROM drive of a computer and that can perform a stable focus jump even under the condition that the disk surface deflection is as large as a specification limit and the reproduction speed is three times or more will be described.

FIG. 2 shows a block diagram of this embodiment. In the figure, reference numeral 12A denotes a primary hold block, and the other configuration is the same as that of the first embodiment shown in FIG. As described above, since the hold block for generating the disk surface deviation interpolation signal is a primary hold in this manner, even if the disk surface deviation is at the limit of the standard, the reproduction speed is not less than 3 times. Also, the position error based on the surface shake interpolation signal can be made substantially zero.

The acceleration / deceleration pulse may be the same as that in the first embodiment because the interlayer distance itself does not change even when the reproduction speed is increased.

As described above, a stable focus jump can be realized even during high-speed reproduction.

Embodiment 3 In the second embodiment, the focus jump method corresponding to the high-speed reproduction has been described. Depending on the system configuration, the noise superimposed on the control signal may be large. In this case, if the noise component is held first-order, a problem that the error is enlarged occurs. In a third embodiment, a system that solves this problem will be described.

FIG. 3 shows a block diagram of this embodiment. This embodiment has a configuration in which a zero-order hold block indicated by 12B and a hold selection switch indicated by 12C are added to the second embodiment. A signal is similarly supplied from the LPF 11 to the zero-order hold 12B and the primary hold 12A, and the hold result is output to the hold selection switch 12C. The hold selection switch 12C outputs a zero-order hold 12B output result at the time of low-speed reproduction such as 1-time speed, and outputs a value of 1 at the time of high-speed reproduction such as 3-times speed, based on a reproduction speed-related switching command.
The output result of the next hold 12A is selected and output to the adder 13.

With this configuration, it is possible to select a zero-order hold that is resistant to noise during low-speed playback and a primary hold with a small interpolation error during high-speed playback. In addition, a focus jump system that is resistant to noise superimposed on the control signal is realized.

Embodiment 4 In the first to third embodiments, F
Although a system effective when the positive and negative waveform characteristics of the ES are equal has been described, in the fourth embodiment, the FES
A system that can cope with an unbalanced detection characteristic will be described.

FIG. 17 shows the FES when the focus search is performed at a constant speed. In the case of the figure, the detection characteristics of the positive polarity and the negative polarity of the FES are unbalanced. When the detection characteristics of the FES are unbalanced, the following problems occur. In the method of the first to third embodiments, since the start timing of the deceleration pulse is created based on the waveform in the area a or b in FIG. 17, the start timing of the deceleration pulse is affected by the FES detection characteristic imbalance. . Therefore, after application of the deceleration pulse, zero speed is guaranteed, but zero FES cannot be guaranteed.

In order to correct the residual FES caused by the FES imbalance generated after the application of the deceleration pulse, after applying a general acceleration / deceleration pulse, a correction pulse is further applied to make the FES zero, and then the focus pull-in is performed. Is the goal.

FIG. 4 is a block diagram showing Embodiment 4 of the present invention. Reference numeral 15 denotes an acceleration / deceleration pulse application result determination block. The other configuration is the same as that of the block already described in the above embodiment, and the description is omitted.

Acceleration / deceleration pulse application result determination block 15
Receives the FES as an input and the deceleration pulse application end timing from the acceleration / deceleration pulse generation block 14. The output causes the acceleration / deceleration pulse generation block 14 to generate a corrected acceleration / deceleration pulse generation command generated after the application of the acceleration / deceleration pulse.

The operation of the acceleration / deceleration pulse application result determination block 15 and the acceleration / deceleration pulse generation block 14 are shown in FIG.
This will be described with reference to FIG.

FIG. 18 is a diagram for explaining the operation of the present embodiment. A in the figure is a focus actuator position,
B is an FES, and C is an acceleration / deceleration pulse, each showing a time change during a focus jump. As can be seen from FIG. B, this drawing is an example in which the FES negative electrode side is large. When receiving the focus jump command from the host device, the acceleration / deceleration pulse generation block 14 generates an acceleration pulse. The end of the acceleration pulse is the time when the FES crosses the acceleration pulse end timing generation threshold. Further, the acceleration pulse application time T0 is measured. Until the deceleration pulse start timing generation threshold is crossed, the acceleration / deceleration pulse has a zero period. FES
Applies a deceleration pulse for a period of T0 from the point at which it crosses the deceleration pulse start end timing generation threshold. At this time,
The acceleration pulse and the deceleration pulse have the same amplitude. Next, the FES immediately after the application of the deceleration pulse was observed, and the value of the
ES, (corresponding value FES = X0 in the figure), residual F
Until the ES becomes a predetermined value, for example, 1/2, a correction acceleration pulse is applied in a direction in which the residual FES decreases. At this time,
The application time T1 of the correction acceleration pulse is measured. Immediately after the application of the correction acceleration pulse, a deceleration pulse having the same amplitude as the correction acceleration pulse is applied in a direction opposite to the correction acceleration pulse for a period of T1.

With the above configuration, the total impulse of the acceleration / deceleration pulse and the corrected acceleration / deceleration pulse is zero, so that the speed is guaranteed to be zero, and the FES is also guaranteed to be substantially zero. Therefore, since two conditions for stably realizing the focus jump are satisfied, a reliable focus jump is realized.

FIG. 19 is a diagram for explaining the operation in the case where the FES unbalance characteristic is opposite to that of FIG. 18, that is, the positive polarity is relatively larger than the negative polarity. The operation is exactly the same as that described with reference to FIG. 18, and as in FIG. 18, the speed is zero and the FES is also substantially zero, so that a stable focus jump can be realized.

Embodiment 5 Continuing from Embodiment 4,
A system that can cope with an unbalanced FES detection characteristic will be described.

In this embodiment, the S-curve imbalance of the FES is measured in advance, and an acceleration / deceleration pulse at the time of a focus jump is output in accordance with the S-curve imbalance characteristic. Hereinafter, a configuration for realizing the above will be described.

FIG. 5 is a block diagram of Embodiment 5 of the present invention. 16 is a focus search block, 17 is a focus loop switch control block, and 18 is an S-curve imbalance detection block. The other configuration is the same as that of the block already described in the above embodiment, and the description is omitted.

The operation at the time of detecting the S-curve imbalance will be described. The focus search block 16 uses the FE
In order to detect the S-curve imbalance of S, a search signal for moving the objective lens 2 at a constant speed is output. The focus loop switch control block 17 selects a focus search block output side with the focus jump selection switch 9, and outputs a control signal for turning off the focus control loop switch 7. The S curve unbalance detection block 18 captures the S curve during the focus search, measures the positive period and the negative period of the S curve, and further calculates the ratio of the positive period to the negative period.

FIG. 20 is a diagram for explaining the detection elements of the S-curve unbalance detection block 18. The waveform in the figure is an S curve during focus search. The positive polarity period and the negative polarity period of the S curve are detected by an FES unbalance detection threshold having a predetermined value a hysteresis with respect to the FES zero level. That is, the S curve positive polarity period Tp is defined as a period in which the S curve is larger than a, and the S curve negative period Tn is defined as a period in which the S curve is smaller than -a. Note that the absolute value of a is determined by the S / N of the S-curve and the like, but it is desirable to select as small as possible. Furthermore, S curve unbalance detection block 1
8, the ratio of the measured Tp and Tn, ie, Tp
/ Tn and Tn / Tp are calculated and stored.

Next, the operation of the acceleration / deceleration pulse generation block 14 during a focus jump will be described. FIG.
FIG. 4 is a diagram illustrating the operation of the present embodiment. A in the figure
Represents a focus actuator position, B represents an FES, and C represents an acceleration / deceleration pulse, and each represents a time change during a focus jump. As can be seen from FIG.
This is a case where the S negative electrode side is large.

When a focus jump command is received from a host device, the acceleration / deceleration pulse generation block 14 generates an acceleration pulse. The end of the acceleration pulse is the time when the FES crosses the acceleration pulse end timing generation threshold. Further, the acceleration pulse application time T0 is measured. At this time, the amplitude of the acceleration pulse is defined as an arbitrary value X2. Further, the acceleration pulse end timing generation threshold is set to the FES unbalance detection threshold a.

The acceleration / deceleration pulse has a zero period until the deceleration pulse start end timing generation threshold is crossed.

A deceleration pulse is applied for a period of T0 * (Tn / Tp) from the time when the FES crosses the deceleration pulse start timing generation threshold value. At this time, the amplitude of the deceleration pulse is set to X2 * (Tp / Tn).

With the above-described configuration, the total impulse of the acceleration / deceleration pulse and the corrected acceleration / deceleration pulse is zero, so that the speed after application of the acceleration / deceleration pulse is guaranteed to be zero. Since the application timing, application time and application amplitude of the acceleration / deceleration pulse are determined and output based on the unbalance characteristics, substantially zero is guaranteed.
Therefore, since two conditions for stably realizing the focus jump are satisfied, a reliable focus jump is realized.

In the case where the FES unbalance characteristic is opposite, that is, the case where the positive polarity is relatively larger than the negative polarity, the same operation as described above is performed, and in the same manner, substantially zero speed and almost zero FES are assured. It is self-evident that the jump can be realized, and a description thereof will be omitted.

Embodiment 6 FIG. In the sixth embodiment, an example in which the fourth embodiment is applied to the fifth embodiment in order to further ensure the fifth embodiment will be described.

FIG. 6 is a block diagram showing Embodiment 6 of the present invention. The functional blocks constituting this figure are the same as the blocks already described in the above-mentioned embodiment, and the description is omitted.

Next, the operation of the acceleration / deceleration pulse generation block 14 during a focus jump will be described. FIG.
FIG. 4 is a diagram illustrating the operation of the present embodiment. A in the figure
Represents a focus actuator position, B represents an FES, and C represents an acceleration / deceleration pulse, and each represents a time change during a focus jump. As can be seen from FIG.
This is a case where the S negative electrode side is large.

An acceleration / deceleration pulse is applied in the same manner as in the fifth embodiment. In the figure, a residual error X0 occurs in the FES after the application of the acceleration / deceleration pulse. This is because the detection accuracy of the S-curve detection block 18 is poor, for example, the focus search speed is not constant, or the surface shake is large, so
And the relative speed of the disk 1 and the disk 1 changes. When the residual error X0 occurs for the above-described reason, the present embodiment has the function of the fourth embodiment, and further applies a correction acceleration pulse and a correction deceleration pulse for correcting the residual error X0 to zero. The setting of the corrected acceleration / deceleration pulse is the same as that in the fourth embodiment, and has already been described, so that the description will be omitted.

In FIG. 22, the case where the residual error X0 has a negative polarity has been described. However, it is clear from the description of the fourth embodiment that the case where the residual error X0 has a positive polarity can be similarly corrected. Further, in FIG. 22, the case where the FES unbalance characteristic is larger in the negative polarity than in the positive polarity is described. However, even in the opposite case, the speed is almost zero and the FES is almost zero by the same operation, and a stable focus jump can be realized. Is self-evident, and its description is omitted.

[0081]

Since the present invention is configured as described above, it has the following effects.

According to the optical disk apparatus of the present invention, in an optical disk apparatus for optically reproducing information recorded on an optical disk having a plurality of recording layers or optically recording information on the optical disk, any of the optical disks An objective lens capable of forming a focused spot on the recording layer of
A focus error detection unit that detects a focus error signal based on reflected light from the condensed spot and generates a focus error control signal; and a driving unit that drives the objective lens based on the focus error control signal. Hold means for holding a focus error control signal, and acceleration / deceleration pulse generation means for generating an acceleration / deceleration pulse for performing a focus jump from the first recording layer to the second recording layer of the optical disc, When receiving, the driving means is driven based on the sum of the output of the hold means and the output of the acceleration / deceleration pulse generating means, and the application timing of the acceleration pulse and the deceleration pulse based on the focus error signal during the focus jump. Is determined so that the runout is large. Stable focus jump can be realized even in the disk.

According to the optical disk apparatus of the present invention, since the holding means is a zero-order hold for holding the value at the time of holding the focus error control signal, a stable focus jump can be realized with a simple configuration. .

According to the optical disk apparatus of the present invention, since the holding means is a primary hold for holding the value and inclination of the focus error control signal at the time of holding, the reproduction speed such as triple speed or quadruple speed is high. Thus, a stable focus jump can be realized even in the case where the focus jump is performed.

According to the optical disk apparatus of the present invention, since the low-pass filter is arranged at the preceding stage of the holding means, the influence on the noise superimposed on the focus error control signal is reduced, and a stable focus jump is achieved. Can be realized.

According to the optical disc apparatus of the present invention, the acceleration pulse and the deceleration pulse generated by the acceleration / deceleration pulse generating means are given so that the impulse becomes zero, so that the relative speed after the focus jump is reduced to zero. And a stable focus jump becomes possible.

According to the optical disk apparatus of the present invention, the acceleration pulse generated by the acceleration / deceleration pulse generation means is given as the end timing when the focus error signal reaches the first threshold value, and the deceleration pulse is output. Since the timing when the second threshold value is reached after passing through the zero cross point of the focus error signal is given as the start timing, the variation in the current sensitivity of the driving means is suppressed, and a stable focus jump is realized. it can.

According to the optical disk device of the present invention, since the first and second threshold values are determined based on the sensitivity characteristics of the driving means, the threshold values are stable without being influenced by the characteristics of the driving means. Focus jump can be realized.

According to the optical disc apparatus of the present invention, the hold means holds the zero-order hold for holding the hold value of the focus error control signal, and holds the hold value and inclination of the focus error control signal. Since the primary hold is performed, and these are switched according to the reproduction speed of the optical disc, a stable focus jump in which the influence of the reproduction speed is suppressed can be realized.

According to the optical disk apparatus of the present invention, since the acceleration / deceleration pulse generating means generates the corrected acceleration / deceleration pulse following the acceleration / deceleration pulse, the focus error signal waveform is unbalanced. This also enables a stable focus jump.

According to the optical disc apparatus of the present invention, the correction acceleration pulse is applied for a period until a residual focus error signal, which is a focus error signal after application of the acceleration / deceleration pulse, reaches a predetermined value, and the correction deceleration pulse is applied. ,
Since the correction acceleration pulse is applied during the same period as the period after the application of the correction acceleration pulse, a stable and reliable focus jump can be performed.

According to the optical disk apparatus of the present invention, since the application timing, application time and application amplitude of the acceleration / deceleration pulse are set based on the shape of the S-curve of the focus error signal, the focus error signal characteristic is improved. A stable focus jump is possible even in an unbalanced state.

According to the optical disk apparatus of the present invention, since the application amplitude and application time of the deceleration pulse are set based on the ratio of the positive polarity period to the negative polarity period of the focus error signal, the focus error signal waveform Focus jump is possible even if is unbalanced.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a focus jump method according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a focus jump method according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a focus jump method according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a focus jump method according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a focus jump method according to a fifth embodiment of the present invention.

FIG. 6 is a block diagram showing a focus jump method according to a sixth embodiment of the present invention.

FIG. 7 is a diagram showing a position error generated when a focus control signal is held on a disk having a surface runout.

FIG. 8 is a diagram showing a position error that occurs when a focus control signal is held on a disk having a runout.

FIG. 9 is a diagram showing a position error generated when a focus control signal is held on a disk having a surface runout.

FIG. 10 is a diagram showing a main technical problem of a focus jump.

FIG. 11 is a diagram illustrating a jump period versus a maximum position error during zero-order hold.

FIG. 12 is a diagram illustrating a comparison between a jump period and a maximum position error according to a hold type;

FIG. 13 is a diagram illustrating a jump period versus a maximum position error during a primary hold.

FIG. 14 is a diagram illustrating a behavior of the focus actuator with respect to an applied pulse.

FIG. 15 is a diagram illustrating a position error due to variation in actuator sensitivity when a fixed acceleration / deceleration pulse is applied.

FIG. 16 is a diagram showing the behavior of the actuator when the acceleration / deceleration pulse application timing is set based on the FES amplitude.

FIG. 17 is a diagram illustrating a case where the FES detection characteristics are unbalanced.

FIG. 18 is a diagram showing a behavior of the fourth embodiment of the present invention.

FIG. 19 is a diagram showing a behavior of the fourth embodiment of the present invention.

FIG. 20 is a diagram illustrating a case where the FES detection characteristics are unbalanced.

FIG. 21 is a diagram showing a behavior of the fifth embodiment of the present invention.

FIG. 22 is a diagram showing a behavior of the sixth embodiment of the present invention.

FIG. 23 is a diagram showing a conventional focus jump method.

[Description of Signs] 0 LD, 1 optical disk, 2 objective lens, 3 focus actuator drive coil, 4 half mirror,
5 photoelectric conversion element, 6 focus error detection block, 7 focus control loop switch, 8 phase compensation block, 9 changeover switch, 10 driver amplifier, 11 low pass filter block, 12 hold block, 13 addition block, 14 acceleration / deceleration pulse generation block, 15. Acceleration / deceleration pulse application result determination block, 16 focus search block, 17 focus loop switch control block, 18S curve unbalance detection block.

Claims (12)

[Claims] 1. An optical disc apparatus for optically reproducing information recorded on an optical disc having a plurality of recording layers or optically recording information on the optical disc, forming a condensed spot on an arbitrary recording layer of the optical disc. An objective lens that can be formed, a focus error detection unit that detects a focus error signal based on reflected light from the condensed spot, and generates a focus error control signal; and the objective lens based on the focus error control signal. Driving means for driving; holding means for holding the focus error control signal; acceleration / deceleration pulse generation means for generating an acceleration / deceleration pulse for performing a focus jump from a first recording layer to a second recording layer of the optical disc; When a focus jump command is received, the output of the hold means and the adjustment An optical disc configured to drive the driving means based on the sum of outputs of the speed pulse generating means and determine application timings of an acceleration pulse and a deceleration pulse based on a focus error signal during a focus jump. apparatus. 2. The optical disk apparatus according to claim 1, wherein said hold means is a zero-order hold for holding a value of the focus error control signal when the focus error control signal is held. 3. The optical disk apparatus according to claim 1, wherein said hold means is a primary hold for holding a value and an inclination of the focus error control signal when the focus error control signal is held. 4. The optical disk device according to claim 1, wherein a low-pass filter is arranged before said holding means. 5. The optical disk apparatus according to claim 1, wherein the acceleration pulse and the deceleration pulse generated by the acceleration / deceleration pulse generation means are given such that their impulse becomes zero. 6. The acceleration pulse generated by the acceleration / deceleration pulse generation means is given as a termination timing when the focus error signal reaches a first threshold, and the deceleration pulse is a signal of the focus error signal. 2. The optical disk device according to claim 1, wherein a timing when the second threshold value is reached after passing through the zero cross point is given as a start timing. 7. The optical disk device according to claim 6, wherein said first and second thresholds are determined based on sensitivity characteristics of said driving means. 8. The hold means has a zero-order hold for holding the value of the focus error control signal when the focus is held, and a primary hold for holding the value and slope of the focus error control signal when the hold is performed. 2. The optical disk device according to claim 1, wherein the switching is performed according to a reproduction speed of the optical disk. 9. The optical disk apparatus according to claim 1, wherein said acceleration / deceleration pulse generating means generates a corrected acceleration / deceleration pulse subsequent to the acceleration / deceleration pulse. 10. The correction acceleration pulse is applied until a residual focus error signal, which is a focus error signal after application of the acceleration / deceleration pulse, reaches a predetermined value, and the correction deceleration pulse is applied after the application of the correction acceleration pulse. 10. The optical disk device according to claim 9, wherein the voltage is applied during the same period as the period. 11. The optical disk device according to claim 1, wherein the application timing, application time, and application amplitude of the acceleration / deceleration pulse are set based on the shape of the S curve of the focus error signal. 12. The optical disk device according to claim 1, wherein the application amplitude and application time of the deceleration pulse are set based on a ratio between a positive polarity period and a negative polarity period of the focus error signal.