JP2002074685A - Method for switching focus between layers and optical disk driving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problem that focus jumps frequently fail when a focus is switched between tow recording layers. SOLUTION: When the focus is switched from an L1 layer to an L0 layer (step 12 → Yes), the number of failures of the focus jumps to the L0 layer (jump L0) is confirmed, unless the number is >=3 (step 13 → No), the focus jump is performed to the L0 layer (step 14). When the focus jump to the L0 layer failed (step 15 → No), one is added to the number of the failures (jump L0) (step 17). When the number of the failures (jump L0) becomes three (step 13 → Yes), the focus is switched to a pull-in processing. First, a focus servo is turned off (step 18), an objective lens is moved down to a lower driving limit, the objective lens is raised from there, the focus servo is turned on at a time point of an FE signal becoming a threshold or more, and focusing is performed (step 19).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical disk drive for recording or reproducing information on or from each recording layer of an optical disk having a plurality of recording layers which can be reproduced from one side. The present invention relates to a method for switching between layers of focus and an optical disk drive.

[0002]

2. Description of the Related Art As an optical disk recording medium, so-called C
CD type optical disk such as D-ROM and DVD (Digital Versatile Disc) suitable for multimedia applications
An optical disk called a so-called optical disk has been developed. In an optical disk drive device corresponding to these optical disks, the optical disk rotated by a spindle motor is irradiated with a laser beam from an optical pickup to a track on the optical disk, and the reflected light is detected to detect data. Reading is performed, and data is recorded by irradiating a laser beam modulated by recording data.

In order to perform a recording or reproducing operation using a laser beam, the spot of the laser beam must be kept in focus on the recording surface of the disc. A focus servo mechanism for controlling a focus state by moving an objective lens, which is an end, in a direction approaching and separating from the disk is mounted.
The focus servo mechanism generally includes a two-axis mechanism having a focus coil for moving the objective lens in the direction of moving toward and away from the disk and a tracking coil for moving the object lens in the radial direction of the disk, and a focusing mechanism based on light reflected from the disk. An error signal (that is, a signal of the amount of deviation from the in-focus state) is generated, a focus drive signal is generated based on the focus error signal, and the focus servo circuit system is applied to the focus coil of the two-axis mechanism. I have. That is, a focus servo mechanism is configured as a feedback control system.

Also, as is well known, the range in which a focus state can be drawn based on a focus error signal is a very narrow range in which an S-shaped curve is observed as a focus error signal. Therefore, in order to perform the focus servo satisfactorily, an operation generally called a focus search or a focus pull-in is required as an operation for turning on the focus servo loop. In the focus pull-in operation, a focus drive signal is applied to the focus coil so that the objective lens is forcibly moved within the focus stroke range in the unfocus state. At this time, when the focus error signal is observed, an S-shaped curve is observed when the position of the objective lens is within a certain range.
The focus servo is turned on at a timing (or zero cross timing) at which the S-shaped curve becomes a linear region.

[0005] By the way, depending on the type of optical disk,
Some have a plurality of recording layers. For example, in the case of the DVD, there is an optical disc having a two-layer structure in which two signal recording / reproducing surfaces generally called layer 0 and layer 1 are formed.
FIG. 2 shows the structure of a DVD having these two signal recording / reproducing surfaces.
This will be described with reference to FIG. The DVD is a disc having a diameter of 12 cm, and the thickness of the disc is 1.2 mm as shown in FIG.

A DVD having a two-layer structure has a disc surface 103
On the side, a disk substrate (transparent layer) 104 made of a transparent synthetic resin material such as a transparent polycarbonate resin, a polyvinyl chloride resin, or an acrylic resin having high light transmittance and mechanical resistance or chemical resistance is formed. . Pits are transferred to one main surface of the disk substrate 104 by a stamper incorporated in a molding die, and a first signal recording surface (0th layer: hereinafter also referred to as layer 0 or L0) 10
1 is formed. The pits in the 0th layer 101 are:
Encoded small holes having different lengths in the circumferential direction corresponding to predetermined information signals are formed on the disk substrate 104 to constitute recording tracks. Further, via a first reflective layer 105 corresponding to the 0th layer 101, a second signal recording surface (first layer: hereinafter also referred to as layer 1 or L1) 102 and a second reflection corresponding to the first layer 102 Layer 106 is formed. In the first layer 102, pits corresponding to information signals are formed as in the case of the 0th layer 101. The upper surface of the second reflective layer 106 is an adhesive surface 107, through which the dummy plate 108 is adhered.

[0007] Laser light output from the pickup of the disk drive device is incident on the DVD 1 from the disk surface 103 side, and information recorded on the 0th layer 101 or the 1st layer 102 is applied to each layer 101 or 102. Will be detected by the reflected light. Note that the first reflective layer 105 is a semi-transparent film, and is formed so as to reflect a certain ratio of laser light. Thus, if the laser light is focused on the 0th layer 101, the signal recorded on the 0th layer 101 can be read from the light reflected by the first reflection layer 105, and the laser light can be focused on the first layer 102. If so, the laser light passes through the first reflective layer 105 and is focused on the first layer 102, so that a signal recorded on the first layer 102 can be read from the light reflected by the second reflective layer 106. .

For an optical disc having a plurality of signal recording / reproducing surfaces, such as the DVD 1 having such a two-layer structure, the focus servo mechanism focuses a laser beam on each signal recording / reproducing surface. In other words, the focus pull-in for focusing on one signal recording / reproducing surface from the unfocused state, and the other signal recording / reproducing surface when in focus on one signal recording / reproducing surface. It is necessary to execute a focus jump operation for shifting to an in-focus state. In this focus jump operation, when one of the signal recording / reproducing surfaces is in focus, acceleration and deceleration pulses are applied to the focus driving system to forcibly move the objective lens, and the focus is pulled into the other signal recording surface. This is executed by performing the pull-in by the focus servo at the time when the movement reaches the range (at the time when the S-shaped curve is observed). As a result, the other signal recording / reproducing surface is in focus.

As described above, to switch the focus between two different recording / reproducing layers, the acceleration and deceleration pulses are applied to the focus drive system without cutting the servo loop of the focus servo system. A so-called focus jump to switch was performed. By performing the focus jump, the focus switching between the layers is performed in comparison with the case where the focus pull-in is performed in which the focus is adjusted from the unfocused state to the predetermined layer.
Focus can be adjusted in a short time.

[0010]

However, an optical disk having a plurality of different recording / reproducing layers has eccentricity and thickness unevenness due to manufacturing errors and the like, and an acceleration pulse and a deceleration pulse for performing a focus jump. It is difficult to set the setting of (1) to a value that provides an optimum operation for all the optical disks.

Also, the control means for controlling the focus servo in response to the supply of the error signal from the optical pickup also causes the offset and the asymmetry of the error signal due to, for example, aberrations caused by the thickness unevenness of the optical disk and the thickness unevenness between the recording and reproducing layers. , Focus jumps often failed. If the focus jump fails, the focus jump is retried several times, but if the focus jump is repeated many times,
It takes more time than focus pull-in. In addition, if the optical disc has large eccentricity and uneven thickness, the focus layer cannot be switched no matter how many times the focus jump is performed, resulting in an error. was there.

In view of the foregoing, the present invention provides a method for reliably switching layers between layers by selectively performing a focus jump and a focus pull-in to a target layer in accordance with characteristics unique to each optical disk caused by a manufacturing error or the like. The purpose is to be able to switch.

[0013]

SUMMARY OF THE INVENTION As means for achieving the above object, an object of the present invention is to provide a layer switching method and an optical disk drive device described below.

1. While recording or reproducing an information signal by irradiating a laser beam to each recording layer of an optical disc having a plurality of recording layers that can be reproduced from one side, the laser beam is applied to one of the plurality of recording layers. A focusing layer switching method for switching the laser beam to focus on another recording layer when the laser beam is in focus, and applying acceleration and deceleration pulses to a focus servo system while a servo loop is connected. When the focus jump is performed to switch the focus between layers and the focus jump is not performed successfully even after performing the focus jump a predetermined number of times, the focus of the laser beam is closer to the other recording layer to be focused. Once in the unfocused state, and then focus first Focus interlayer switching method being characterized in that to perform the focus pull-detecting the location.

2. If switching between focus layers does not succeed even after performing the focus jump a predetermined number of times,
2. The focus interlayer according to claim 1, wherein the result is stored, and when focus interlayer switching is performed on the optical disc, the focus pull-in is performed without performing the focus jump. 3. Switching method.

3. An optical disc drive for recording or reproducing an information signal by irradiating a laser beam to each recording layer of an optical disc having a plurality of recording layers reproducible from one side, wherein one of the plurality of recording layers When the laser beam is in focus, the acceleration and deceleration pulses are applied to the focus servo system while the servo loop is connected, thereby performing a focus jump for switching the laser beam to focus on another recording layer. Means for measuring and storing the number of failures of the focus jump, means for performing a focus pull-in for once detecting an in-focus state after the laser beam is once in an unfocused state, and The focus pull-in method for pull-in A polarity inversion means for inverting the polarity of the error drive signal and the error signal, and when the focus can not be switched between layers even if the focus jump is performed a predetermined number of times, the focus is adjusted before the interlayer is switched. An optical disc drive device, wherein the focus pull-in is performed from a side closer to the other recording layer, which focuses by switching between layers than one recording layer.

4. An optical disk drive for recording or reproducing an information signal by irradiating a laser beam to each recording layer of a DVD having two recording layers of one side of a first layer and a first layer, wherein the two recording layers of one side are provided. When the laser beam is focused on one of the recording layers, the laser beam is focused on the other recording layer by applying acceleration and deceleration pulses to the focus servo system while the servo loop is connected. Means for performing a focus jump, and measuring the number of failures of the focus jump from the 0th layer to the first layer and the number of failures of the focus jump from the 1st layer to the 0th layer. Storage means for temporarily storing the laser beam in an unfocused state and then focusing the laser beam on the zeroth layer. From the first layer to the zeroth layer, comprising: means for performing focus pull-in for detecting the direction; and a polarity inversion means for reversing the lens drive direction and error signal polarity during focus pull-in in the focus pull-in means. If switching between the focus layers cannot be performed even after performing the focus jump a predetermined number of times, the focus pull-in is performed by the focus pull-in means, and a predetermined number of times from the 0th layer to the first layer is performed. If the focus jump cannot be performed even when the focus jump is performed, the polarity inversion means inverts the lens driving direction and the polarity of the error signal at the time of focus pull-in, and then performs the focus pull-in by the focus pull-in means. Optical disc characterized by being configured to perform Operated device.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of a method for switching between focus layers and an optical disk drive according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a main part of an embodiment of an optical disk drive according to the present invention. In FIG. 1, the description of the configuration of the signal processing unit and the like not directly related to the present invention is omitted.

In FIG. 1, an optical disc 1 is loaded on a turntable and a spindle motor (SPM) 2,
During reproduction, a control signal output from a digital signal processing unit (DSP) 8 is supplied to the SPM driver 4 and controlled at a constant linear velocity or a constant angular velocity while the turntable and the spindle motor (SPM) 2 are controlled. It is rotating by.

Although a detailed configuration of the pickup (PU) 3 is not shown, a light source (laser diode), a photodetector for detecting light reflected from the disk 1, and a laser beam output from the light source are collected. 2 (see FIG. 2), a mechanism (tracking) for holding the objective lens 31 movably in the radial direction of the optical disc 1, and a mechanism (moving) for movably holding the objective lens 31 in the direction perpendicular to the reading surface of the disc 1. Focusing). Then, by moving the objective lens 31 in the tracking direction and the focusing direction, a change in a signal obtained from the photodetector is output to the FEP 6 and the FE is output.
At P6, an error signal necessary for control is generated together with the read signal, and output to the DSP 8.

The DSP 8 performs necessary processing on the error signal supplied from the FEP 6 and outputs a drive control signal to the spindle motor driver 4 and the actuator driver 5 to thereby control the spindle motor driver 4.
In addition, it controls the rotation speed of the spindle motor 2 driven by the actuator driver 5 and the tracking and focus position of the pickup 3.

An error signal supplied to the DSP 8 for performing this control includes a focus error signal (FE signal) used for control in the focus direction in the FEP 6, and a tracking error signal (TE) used for control in the track direction.
Signal), which is generated as an actual data signal (RF signal) or the like for the DSP 8 to generate a read clock or detect the number of rotations.

These error signals are supplied to the DSP 8 and output as control signals such as a focus control signal (FOD signal), a tracking control signal (TRD signal), and a spindle motor control signal (EC signal). The drive signal amplified by the motor driver 4 and the actuator driver 5 includes
And the coil of PU3.

The data signal read by the PU 3 from the signal recording / reproducing surface of the optical disc 1 is output to a signal processing block (not shown) via the FEP 6 and the DSP 8.

When a request signal is supplied from a later-stage signal processing block (not shown), the CPU (mechanical control) 7 outputs a control signal to the DSP 8 in response to the request, and performs a seek operation in the track direction or one-way operation. Switching from one to the other recording / playback layer (focus jump)
Is executed. In addition, the CPU 7 controls the FEP 6
It is also possible to make various settings for and DSP8.

In the optical disk drive having such a configuration, the F3 when the PU3 is driven in the focus direction is
The focus error signal (FE signal) output from EP6 will be described.

As shown in FIGS. 2A and 2B, with respect to the DVD 1 having a two-layer structure, the objective lens 31 was driven in the focus direction from the lower drive limit (DD) position to the upper drive limit (DU) direction. In this case, an FE signal as shown in FIG. 3 can be obtained. The graph shown in FIG.
Is a graph showing the position of the FE signal corresponding to the position from the drive lower limit (DD) position to the drive upper limit (DU) position on the vertical axis. Therefore, FIG.
As shown in FIG. 2A, the FE signal at the drive position D0 when the 0th layer 101 is in focus is the value of the FE signal at the D0 position in FIG. 3, as shown in FIG. First
FE at drive position D1 when layer 102 is in focus
The signal is the value of the FE signal at the position D1 in FIG. Note that the polarity of the FE signal shown in FIG. 3 is an example, and the polarity may be reversed as long as the control direction in the DSP 8 matches the output of the FEP 6 correctly. And
By detecting such an S-shaped curve of the FE signal, it is possible to focus on the 0th layer 101 and the first layer 102.

Next, the focus pull-in operation will be described with reference to the waveform at the time of focus pull-in. Usually, the focus pull-in is performed when the recording / reproducing layer is on-focused from an off-focus state such as at the start of reproduction of the optical disc. FIG. 4 is a diagram showing a signal waveform at the time of normal focus pull-in.

The upper waveform in the figure is a signal waveform of a drive voltage (hereinafter referred to as FOD) in the focus direction supplied from the DSP 8 to the actuator driver 5, and the lower waveform is FEP.
6 to the DSP 8 from the focus error signal (F
E signal).

As described above, the normal operation of the focus pull-in operation is to lower the voltage of the FOD, lower the objective lens 31 to the lower drive limit DD (lens down in FIG. 4), and then gradually increase the voltage of the FOD. To drive the objective lens 31 upward (lens up in FIG. 4).
When the E signal drops once and then rises sharply and exceeds a preset threshold value (pull-in point position in FIG. 4), a focus servo loop is connected (focus on), and the 0th layer is turned on. 101 can be focused.

The operation for performing a focus jump (first method) from one recording / reproducing layer to the other recording / reproducing layer will be described. Although there are various methods for the focus jump, here, the simplest fixed pulse jump method will be described.

FIG. 5 shows the first layer (hereinafter referred to as L0 layer) 101 from the 0th layer (hereinafter also referred to as L0 layer) in the DVD 1 having a two-layer structure.
FIG. 3 is a diagram showing a waveform when performing layer switching (focus jump) to a layer (also referred to as one layer) 102. The upper waveform in the drawing is a signal waveform of a drive voltage (hereinafter referred to as FOD) in the focus direction supplied from the DSP 8 to the actuator driver 5, and the lower waveform is a focus error signal (FE signal) supplied from the FEP 6 to the DSP 8. ).

As a basic operation of the focus jump by the fixed pulse, first, the focus servo loop is kept connected (turned on) until immediately before the jump, and
As a signal, a fixed pulse having a predetermined magnitude (a driving voltage having a predetermined height: acceleration pulse) is output for a predetermined time (acceleration pulse in FIG. 4). At the start of the output of the fixed pulse, the focus servo loop is turned off. Then, the acceleration pulse is stopped when a predetermined time has elapsed, and the output of the FOD signal is stopped for a predetermined time (stop in FIG. 4). After a certain period of time, a fixed pulse (deceleration pulse) having a predetermined magnitude in the opposite direction is output as a FOD signal, and the focus servo loop is turned on again when the FE signal level reaches a set threshold (FIG. 4 deceleration pulse).

In the above operation, by applying an acceleration pulse, the direction in which the objective lens 31 focuses on the first layer 102 from the position (D0 in FIG. 2) where the objective lens 31 is in focus (FIG. 2). Since the objective lens 31 is considered to have reached near the position of D1 in FIG. 2 when the FE signal level reaches the set threshold value, the focus servo loop is turned on at this position. , The first layer 102 can be focused. And
In this case, the time for applying the acceleration pulse and the time for stopping the output of the FOD signal are fixed times stored in the CPU 7, and since the objective lens 31 only moves from the position D0 to D1, the switching between the focus layers can be performed at high speed. It can be carried out.

FIG. 6 shows waveforms when performing a layer switch (focus jump) from the first layer 102 to the zeroth layer 101 in the DVD 1 having a two-layer structure. The upper waveform in the figure is a signal waveform of a drive voltage (hereinafter, FOD) in the focus direction supplied from the DSP 8 to the actuator driver 5, and the lower waveform is a focus error signal (FE signal) supplied from the FEP 6 to the DSP 8. It is a waveform. As is apparent from comparison with the layer switching from the L0 layer 101 to the L1 layer 102 shown in FIG. 5, only the polarities of the acceleration pulse and the deceleration pulse are opposite to those in FIG.
The operation of the objective lens 31 is also different in that it moves from the position D1 to the position D0 (drives in the reverse direction), but the other operation contents are the same, and a detailed description is omitted.

In the case where the focus is switched between layers as described above, the focus can be switched at high speed by using the focus jump described with reference to FIGS. There are optical discs that cannot switch between focus layers by focus jump due to eccentricity, thickness unevenness, and thickness unevenness between recording and reproducing layers due to errors and the like. In this case, focus re-pulling described below is performed. In the case where the switching from the L1 layer 102 to the L0 layer 101 is performed by forcible re-pulling, the operation is substantially the same as that of the normal focus pull-in described above with reference to FIG. An example in which switching from the L0 layer 101 to the L1 layer 102 is performed by forced re-pulling will be described with reference to FIG. The upper waveform in FIG. 7 is a signal waveform of a drive voltage (hereinafter referred to as FOD) in the focus direction supplied from the DSP 8 to the actuator driver 5, and the lower waveform is a focus error signal (FE signal) supplied from the FEP 6 to the DSP 8. It is a waveform of.

As is clear from comparison with the normal focus pull-in case shown in FIG.
In the case of forced re-pull-in for switching to the first layer 102, the objective lens 31 is temporarily moved upward (up) to a position closer to the driving upper limit DU than the position D1, and then moved downward ( The focus loop is turned on when the FE signal exceeds a set threshold while moving in the down direction. By detecting the FE signal after setting the objective lens 31 at a position closer to the drive upper limit DU than the position D1, it is possible to focus on the L1 layer 102 where the focus loop is first turned on.

L1 due to the forced re-pull-in of the focus
Switching to the layer 102 is performed by the following steps.

First, the focus servo is temporarily turned off (loop OFF in FIG. 7).

In order to perform pull-in in the direction opposite to the normal focus pull-in, the polarities of parameters necessary for turning on the focus (a drive value for determining the drive direction and an FE threshold for setting the pull-in level) are switched.

After the voltage of the FOD is increased and the objective lens 31 is once increased to the drive upper limit DU, the voltage of the FOD is gradually decreased to drive the objective lens 31 in a lowering direction (up → down in FIG. 7). , When the FE signal once rises and then falls sharply, and falls below a preset threshold value (pull-in point position in FIG. 7), the focus servo loop is connected (focus-on) to perform the first Focusing can be performed on the layer 102.

The other necessary operations for reproduction (these operations are omitted because they are not directly involved in the present invention) are performed, and the processing is terminated.

In the above description of the embodiment, the FO
Although the polarity of the D signal and the threshold of the FE signal are inverted by software, in the block diagram shown in FIG. 1, the FE signal output from the FEP 6 is inverted by hardware and supplied to the DSP 8. The FOD signal, which is a control signal output from the DSP 8, may be inverted in hardware and supplied to the actuator driver 5.

In the present invention, when the focus is switched between layers, the above-described focus jump and focus re-pulling are selectively switched and executed.

In other words, the normal interlayer switching uses the focus jump which is extremely fast in the time required for the interlayer switching. However, the focus jump fails due to unevenness in the disk thickness, unevenness in the thickness between the disk layers, and deviation of the disk surface. If so, focus re-pulling is performed.

As a criterion for switching to the forced focus re-pulling, for example, the number of executions of the normal focus jump is counted, and when the count (the number of retries) exceeds a certain number, the focus re-pulling is performed. It has been selectively switched to use.

The specific switching operation will be described with reference to the flowchart shown in FIG. Here, a description will be given assuming that switching to focus forced re-pulling is performed when the focus jump fails three times. When an interlayer switching signal is supplied to the CPU 7 from a signal processing circuit (not shown), the CPU 7 instructs the DSP 8 to perform interlayer switching.

First, the values of the number of failed focus jumps to the L0 layer 101 (jumpL0) and the number of failed focus jumps to the L1 layer 102 (jumpL1) are initialized (step 11). It is preferable that this initialization work be performed in advance at the time of turning on the power or at the time of inserting the optical disk 1, not after an instruction to switch between layers has been received.

If the instruction to switch between layers is to switch the focus from the L1 layer 102 to the L0 layer 101 (step 12 → Yes), the number of failed focus jumps to the L0 layer 101 (jump L0) is checked. If not (step 13 → No), a normal focus jump to the L0 layer 101 is performed (step 14). If this focus jump is successful (step 15 → Yes),
The post-processing is performed and the process ends (step 16). When the focus jump to the L0 layer 101 fails (step 15 → No), 1 is added to the number of failures (jumpL0) of the focus jump to the L0 layer 101 (step 1).
7) Return to step 13. This process is repeated until the focus jump to the L0 layer 101 succeeds or the number of failures (jumpL0) of the focus jump becomes three.

The number of failed focus jumps (jumpL
When (0) becomes 3 (Step 13 → Yes), the process is switched to forced focus re-pulling. The focus re-pulling into the L0 layer 101 performs the same operation as the focus pull-in from the initial state described above with reference to FIG. First, turn off the focus servo (step 1
8) The objective lens 31 is moved to the lower drive limit DD, and the objective lens 31 is raised from there. When the focus error signal becomes equal to or larger than the threshold, the focus servo is turned on to perform focusing (step 19). The processing is performed and the processing ends (step 20).

By performing such processing, it is possible to reliably switch the focus to the L0 layer 101 in a short time and irrespective of a disc manufacturing error.

Next, the case of switching the focus from the L0 layer 101 to the L1 layer 102 will be described. If the interlayer switching instruction is a focus switching from the L0 layer 101 to the L1 layer 102 (Step 12 → No), the number of failures of the focus jump to the L1 layer 102 (jumpL1)
Is checked, and if it is not 3 or more (Step 21 → No), a normal focus jump to the L1 layer 102 is performed (Step 22). Then, if the focus jump is successful (step 23 → Yes), post-processing is performed and the process ends (step 24). If the focus jump to the L1 layer 102 fails (step 23 → No), the L1 layer 10
1 for the number of failed focus jumps to 2 (jumpL1)
Is added (step 25), and the process returns to step 21. This process is repeated until the focus jump to the L1 layer 102 succeeds or the number of failed focus jumps (jumpL1) becomes three.

The number of focus jump failures (jumpL
When 1) becomes 3 (Step 21 → Yes), the process is switched to focus re-pulling. The focus re-pulling into the L1 layer 102 is the focus pull-in from the initial state as described above with reference to FIG.
The operation has the opposite polarity. First, the focus servo is turned off (step 26), the value of the drive signal of the objective lens 31 and the polarity of the threshold of the focus error signal are inverted (step 27), and the objective lens 31 is moved to the drive upper limit DU. Then, the objective lens 31 is lowered, and when the focus error signal falls below the threshold, the focus servo is turned on to perform focusing (step 2).
8) After the value of the inverted drive signal of the objective lens 31 and the polarity of the threshold value of the focus error signal are returned to the original (step 29), post-processing is performed and the process is terminated (step 3).
0).

By performing such processing, it is possible to reliably switch the focus to the L1 layer 102 in a short time and irrespective of disc manufacturing errors.

In the above-described embodiment, the focus jump is repeatedly performed a predetermined number of times (three times), and then the forced focus re-pulling is performed. However, for an optical disc on which focus jumping has been performed repeatedly after failing the focus jump a predetermined number of times,
When switching between focus layers again, there is a high probability that a focus jump will fail. Therefore, performing focus re-pulling immediately without performing a focus jump can result in high-speed switching between focus layers. As another embodiment of the present invention, a case will be described in which when focus forced re-pulling is performed in the previous focus layer switching, focus jump is not performed in the second and subsequent focus interlayer switching.

For example, after inserting a certain optical disk 1 into the optical disk recording / reproducing apparatus, until the optical disk 1 is replaced or the power of the optical disk recording / reproducing apparatus is turned off, various adjustments at the time of initial startup or The number of times the focus jump failed when entering the playback state and the jump direction (jmp in the flowchart of FIG. 8)
L0 and jmpL1), and when it is necessary to switch layers next time, according to the stored contents,
From the beginning, the focus is switched between layers using the forced focus re-pulling. Specifically, the values of jmpL0 and jmpL1 are held in the CPU 7 until the optical disk 1 is exchanged or the power of the optical disk recording / reproducing apparatus is turned off, and step 11 in FIG. Then, when the focus jump has failed three times or more at the time of various adjustments at the time of the initial start-up or the previous layer switching, the forced focus re-pulling is automatically executed.

Further, with respect to the optical disk which has failed the focus jump three or more times, the unique identification information for individually identifying the optical disk is read, and it is determined by the CPU that the focus jump cannot be performed together with the unique identification information.
If the optical disk is once recognized as not being able to perform the focus jump, the optical disk does not perform the focus jump even after the power of the optical disk recording / reproducing apparatus is turned off or the optical disk is replaced. Then, it is possible to immediately execute the forced re-pull-in of the focus and switch the focus layer.

[0058]

The focus interlayer switching method and the optical disk drive of the present invention use a focus jump that enables high-speed focus interlayer switching for an optical disk having a small error such as eccentricity or thickness unevenness. Since focus pull-in is performed for an optical disc for which switching between layers is impossible, there is an effect that switching between layers of focus can be performed as quickly and reliably as possible according to the characteristics of each optical disc.

Further, in the invention according to the second aspect, for an optical disk in which a focus jump has failed, the fact is stored, and in the next and subsequent switching between focus layers, the focus pull-in is performed without performing the focus jump. Therefore, it is possible to omit the time for repeating the retry due to the failure of the focus jump, and it is possible to switch the focus between layers at a higher speed with respect to an optical disc having a large error.

Further, in the optical disk drive according to the third and fourth aspects, when switching between focus layers is performed by pulling in the focus, the focus pulling in is performed from the side closer to the recording layer to be focused by pulling in. Therefore, there is an effect that it can be realized with a simple configuration.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of an optical disk drive of the present invention.

FIG. 2 is a diagram for explaining a focus position on a 0th layer and a first layer of a DVD.

FIG. 3 is a diagram for explaining a focus error signal (S curve) generated when the DVD passes through the 0th layer and the 1st layer.

FIG. 4 is a graph showing waveforms of an FOD signal and an FE signal during a normal focus pull-in operation.

FIG. 5 is a graph showing waveforms of an FOD signal and an FE signal during a focus jump operation from the L0 layer to the L1 layer.

FIG. 6 is a graph showing waveforms of an FOD signal and an FE signal during a focus jump operation from the L1 layer to the L0 layer.

FIG. 7 is a graph showing waveforms of an FOD signal and an FE signal when focusing is performed at the time of switching between layers from the L0 layer to the L1 layer.

FIG. 8 is a flowchart illustrating an embodiment of a focus interlayer switching method according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Optical disk (DVD) 2 Turntable and spindle motor (SPM) 3 Pickup (PU) 4 Spindle motor driver (SPM driver) 5 Actuator driver 6 Front end processor (FEP) 7 CPU (storage means, mechanical control) 8 Digital signal processing part (Means for performing focus jump, means for performing focus pull-in, means for reversing polarity, DS
P) 101 First signal recording / reproducing surface (recording layer, 0th layer, L0
Layer) 102 Second signal recording / reproducing surface (recording layer, first layer, L1
Layer) 31 objective lens

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Claims (4)

[Claims] An optical disk having a plurality of recording layers that can be reproduced from one side is irradiated with a laser beam to record or reproduce an information signal, and one of the plurality of recording layers is recorded. A layer switching method for focusing, wherein the laser beam is focused on another recording layer when the laser beam is focused on a layer, wherein the acceleration and deceleration pulses are generated while the servo loop is connected. When the focus jump is performed by applying to the focus servo system and performing the interlayer switching of the focus, and the interlayer switching of the focus is not successful even after the focus jump is performed a predetermined number of times, the focus of the laser beam is adjusted to the focus. First to the unfocused state on the side close to the recording layer Focus interlayer switching method being characterized in that to perform the focus pull detecting a position fit Kas. 2. If focus interlayer switching is not successful even after performing a predetermined number of focus jumps, the result is stored. If focus interlayer switching is performed on the optical disc, the focus jump is performed. 2. The method according to claim 1, wherein the focus pull-in is performed without performing the focus pull-in. 3. An optical disk drive for recording or reproducing an information signal by irradiating a laser beam to each recording layer of an optical disk having a plurality of recording layers that can be reproduced from one side, wherein: When the laser beam is focused on one of the recording layers, the acceleration and deceleration pulses are applied to the focus servo system while the servo loop is connected so that the laser beam is focused on the other recording layer. Means for performing a focus jump to be switched; storage means for measuring and storing the number of times the focus jump has failed; and performing focus pull-in for once detecting the position where the focus of the laser beam is brought into an unfocused state and then focusing first. Means and a focus pulling means in said focus pulling means. A polarity reversing means for reversing the lens driving direction and the polarity of the error signal at the time of focusing, and when the focus can not be switched between layers even if the focus jump is performed a predetermined number of times, the focus is switched before the interlayer is switched. An optical disk drive device, wherein the focus pull-in is performed from a side closer to the other recording layer, which is focused by switching between layers than the one recording layer that has been matched. 4. An optical disk drive for recording or reproducing an information signal by irradiating a laser beam to each recording layer of a DVD having two recording layers on one side, a 0th layer and a 1st layer, When the laser beam is focused on one of the two recording layers, the laser is applied to the other recording layer by applying an acceleration and deceleration pulse to the focus servo system while the servo loop is connected. Means for performing a focus jump for switching to focus the beam, the number of failures of the focus jump from the zeroth layer to the first layer, and the failure of the focus jump from the first layer to the zeroth layer Storage means for measuring and storing the number of times, respectively, and setting the focus of the laser beam to an
The first layer, comprising: a focus pull-in unit for detecting a position where a layer is focused; and a polarity reversing unit for reversing a lens driving direction and an error signal polarity during focus pull-in in the focus pull-in unit. If the focus can not be switched between layers even after performing the focus jump a predetermined number of times from the 0th layer to the 0th layer, the focus pulling is performed by the focus pulling means, and the focus pulling is performed from the 0th layer to the first layer. If the focus can not be switched between layers even after performing the focus jump to the layer a predetermined number of times, the polarity reversing means reverses the lens driving direction and the polarity of the error signal at the time of focusing, and then performs the focusing. The focus pull-in by the means for performing Optical disk drive according to claim.