JP3685389B2 - Focus layer switching method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to an optical disc drive apparatus that performs recording or reproduction on each recording layer of an optical disc having a plurality of recording layers that can be reproduced from one side, and in particular, a method for switching between layers of laser light focus for recording or reproduction.To the lawIt is related.
[0002]
[Prior art]
As an optical disk recording medium, a CD type optical disk such as a so-called CD-ROM, an optical disk called DVD (Digital Versatile Disc) suitable for multimedia use, and the like have been developed. In an optical disc drive device corresponding to these optical discs, data is recorded by irradiating a laser beam on an optical disc rotated by a spindle motor to a track on the optical disc and detecting the reflected light. Reading is performed or data is recorded by irradiating a laser beam modulated by the recording data.
[0003]
In order to perform a recording or reproducing operation with a laser beam, the spot of the laser beam must be kept in focus on the recording surface of the disk. For this reason, the disk drive device has an output end of the laser beam. A focus servo mechanism is mounted that controls the focus state by moving the objective lens in the direction of contact with and away from the disk. As this focus servo mechanism, there is usually a biaxial mechanism having a focus coil that moves the objective lens in the direction of contact with and away from the disk and a tracking coil that can be moved in the radial direction of the disk, and focus from the reflected light information from the disk. It is composed of a focus servo circuit system that generates an error signal (that is, a signal of a deviation amount from the in-focus state), generates a focus drive signal based on the focus error signal, and applies it to the focus coil of the biaxial mechanism. Yes. That is, a focus servo mechanism is configured as a feedback control system.
[0004]
Further, as is well known, the range that can be brought into the in-focus state based on the focus error signal is a very narrow range in which the S-curve is observed as the focus error signal. In order to execute the servo satisfactorily, an operation generally called focus search or focus pull-in is required as an operation for turning on the focus servo loop. In this 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 unfocused state. If the focus error signal is observed at this time, 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 the timing (or zero cross timing) at which the S-shaped curve becomes a linear region.
[0005]
Incidentally, some types of optical disks have a plurality of recording layers. For example, in the case of the above-mentioned 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. The structure of a DVD having these two signal recording / reproducing surfaces will be described with reference to FIG. The DVD is a disk having a diameter of 12 cm, and the thickness of the disk is 1.2 mm as shown in FIG.
[0006]
A DVD with a two-layer structure is a disc made of a transparent synthetic resin material such as a transparent polycarbonate resin, a polyvinyl chloride resin, or an acrylic resin having a high light transmittance and having mechanical resistance or chemical resistance on the disk surface 103 side. A substrate (transparent layer) 104 is formed. On the disk substrate 104, pits are transferred to one main surface 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) 101 is formed. The pits in the 0th layer 101 are formed in the disc substrate 104 as encoded small holes having different circumferential lengths corresponding to predetermined information signals, and constitute recording tracks. . Further, 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 are passed through the first reflective layer 105 corresponding to the zeroth layer 101. Layer 106 is formed. Similarly to the 0th layer 101, the first layer 102 is also formed with pits corresponding to information signals. The second reflective layer 106 has an adhesive surface 107 on which the dummy plate 108 is bonded.
[0007]
For this DVD 1, laser light output from the pickup of the disk drive device is incident from the disk surface 103 side, and information recorded on the 0th layer 101 or the first layer 102 is reflected from each layer 101 or 102. It will be detected by light. 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 beam is focused on the 0th layer 101, the signal recorded on the 0th layer 101 can be read from the reflected light from the first reflective layer 105, and the laser beam is 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, and the signal recorded on the first layer 102 can be read from the light reflected by the second reflective layer 106. .
[0008]
For an optical disc having a plurality of signal recording / reproducing surfaces such as a DVD 1 having such a two-layer structure, the focus servo mechanism needs to focus the laser beam on each signal recording / reproducing surface. In other words, when the focus is pulled from the unfocused state to one signal recording / reproducing surface, and when the other signal recording / reproducing surface is in focus, the other signal recording / reproducing surface is focused. It is necessary to execute a focus jump operation for shifting to a focus state. This focus jump operation applies the acceleration and deceleration pulses to the focus drive system to force the objective lens to move when one signal recording / playback surface is in focus, and pulls the focus on the other signal recording surface. It is executed by performing pull-in with a focus servo when reaching the range (when the S-shaped curve is observed). As a result, the other signal recording / reproducing surface is brought into focus.
[0009]
Thus, in order to switch the focus between two different recording / reproducing layers, the so-called focus is switched by applying acceleration and deceleration pulses to the focus drive system without cutting the servo loop of the focus servo system. A jump was taking place. By performing the focus jump, the focus switching between layers can be focused in a short time compared to the case of performing the focus pull-in for focusing on a predetermined layer from the unfocused state.
[0010]
[Problems to be solved by the invention]
However, an optical disc having a plurality of different recording / reproducing layers has eccentricity and uneven thickness due to manufacturing errors, etc., and the setting of acceleration pulse and deceleration pulse for performing a focus jump is optimal for all optical discs. It was difficult to obtain a value that would result in proper operation.
[0011]
Also, on the control means side that controls the focus servo when an error signal is supplied from the optical pickup, for example, an offset or error signal asymmetry occurs due to aberrations caused by uneven thickness of the optical disc or uneven thickness of the recording / reproducing layer. , Focus jumps often failed. If the focus jump fails, the focus jump will be retried several times, but if the focus jump is repeated many times, it will take longer than the focus pull-in, and eccentricity and uneven thickness With an optical disc having a large size, there has been a problem that the focus layer cannot be switched no matter how many times the focus jump is performed, resulting in an error.
[0012]
Therefore, according to the present invention, layer switching can be reliably performed by selectively executing focus jump between layers and focus pull-in to the target layer in accordance with the characteristics peculiar to each optical disc caused by manufacturing errors. The purpose is to do so.
[0013]
[Means for Solving the Problems]
  As means for achieving the above-mentioned purpose, it is shown below.How to switch focus between layersIt is something to be offered.
[0014]
  1.During recording or reproduction of an information signal by irradiating 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 method for switching between layers of focus, wherein the laser beam is switched to focus on the other recording layer when the focus is on,
A focus jump method for switching between layers of focus by applying acceleration and deceleration pulses to the focus servo system with the servo loop connected,
Once the focus servo is removed, focus pull-in from the side close to the target layer,
2 focus interlayer switching method,
If focus layer switching is not successful even after a predetermined number of focus jumps, the result is stored, and when focus layer switching is performed on the optical disc, the focus jump is not performed. A method for switching between layers of focus, characterized in that pull-in is performed.
[0018]
DETAILED DESCRIPTION OF THE INVENTION
  An embodiment of a focus interlayer switching method according to the present invention will be described with reference to the drawings. FIG. 1 illustrates the present invention.To explain how to switch focus between layersIt is a block diagram which shows the principal part of one Embodiment of an optical disk drive device. In FIG. 1, the configuration of the signal processing unit and the like not directly related to the present invention is omitted.
[0019]
In FIG. 1, an optical disk 1 is mounted on a turntable and a spindle motor (SPM) 2 and during reproduction, a control signal output from a digital signal processing unit (DSP) 8 is supplied to an SPM driver 4 to obtain a constant line. It is rotated by a turntable and a spindle motor (SPM) 2 while being controlled at a rotational speed of a speed or a constant angular speed.
[0020]
Although a detailed configuration of the pickup (PU) 3 is not shown, a light source (laser diode), a photodetector for detecting reflected light from the disk 1, and a laser beam output from the light source are collected. An objective lens 31 (see FIG. 2), a mechanism for holding the objective lens 31 movably in the radial direction of the optical disc 1 (tracking), a mechanism for holding the objective lens 31 movably in the vertical direction on the reading surface of the disc 1 (focusing), and the like It is comprised by. Then, by moving the objective lens 31 in the tracking direction and the focus direction, a change in the signal obtained from the photodetector is output to the FEP 6, and an error signal necessary for control is generated together with the readout signal in the FEP 6 and output to the DSP 8. ing.
[0021]
The DSP 8 is driven by the spindle motor driver 4 and the actuator driver 5 by performing necessary processing on the error signal supplied from the FEP 6 and outputting a drive control signal to the spindle motor driver 4 and the actuator driver 5. The number of rotations of the spindle motor 2 and the tracking of the pickup 3 and position control in the focus direction are performed.
[0022]
An error signal supplied to the DSP 8 for performing this control includes a focus error signal (FE signal) used for controlling the focus direction in the FEP 6, a tracking error signal (TE signal) used for controlling the track direction, This is a signal generated as an actual data signal (RF signal) or the like for generating a read clock or detecting the number of rotations in the DSP 8.
[0023]
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). As a drive signal amplified by the actuator driver 5, the coils of the spindle motors 2 and PU3 are driven.
[0024]
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.
[0025]
Then, when a request signal from a signal processing block (not shown) is supplied, the CPU (mechanism controller) 7 outputs a control signal to the DSP 8 according to the requested content to perform a seek operation in the track direction or from one to the other. The focus is switched to the recording / reproducing layer (focus jump). The CPU 7 can also make various settings for the FEP 6 and the DSP 8.
[0026]
A focus error signal (FE signal) output from the FEP 6 when the PU 3 is driven in the focus direction in the optical disc drive apparatus having such a configuration will be described.
[0027]
As shown in FIGS. 2A and 2B, when the objective lens 31 is driven in the focus direction from the drive lower limit (DD) position to the drive upper limit (DU) direction with respect to the dual-layer DVD 1 as shown in FIGS. An FE signal as shown in FIG. 3 can be obtained. The graph shown in FIG. 3 is a graph in which the horizontal axis indicates the position of the objective lens 31 from the drive lower limit (DD) position to the drive upper limit (DU) position, and the level of the FE signal corresponding to that position is expressed on the vertical axis. is there. Therefore, as shown in FIG. 2A, the FE signal at the driving position D0 when the 0th layer 101 is in focus is the value of the FE signal at the D0 position in FIG. ), The FE signal at the driving position D1 when the first layer 102 is in focus is the value of the FE signal at the D1 position 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. Then, 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.
[0028]
Next, the focus pull-in operation will be described with reference to the waveform at the time of focus pull-in. Normally, focus pull-in is performed when on-focusing is performed from the off-focus state such as at the start of reproduction of the optical disc to the recording / reproducing layer. FIG. 4 is a diagram showing signal waveforms during normal focus pull-in.
[0029]
In the drawing, the upper waveform is a signal waveform of a driving 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 FEP6 to the DSP8. It is a waveform.
[0030]
As described above, the normal operation of pulling in the focus is to lower the FOD voltage and lower the objective lens 31 once to the drive lower limit DD (lens down in FIG. 4), and then gradually increase the FOD voltage to increase the objective lens. When 31 is driven in the direction of raising (lens up in FIG. 4), the FE signal suddenly rises after dropping once and exceeds a preset threshold value (retraction point position in FIG. 4). In addition, the focus can be focused on the 0th layer 101 by connecting a focus servo loop (focus on).
[0031]
An operation when performing a focus jump (first method) from one recording / reproducing layer to the other recording / reproducing layer will be described. There are various methods for focus jumping. Here, the simplest fixed pulse jumping method will be described.
[0032]
FIG. 5 is a diagram showing waveforms when performing layer switching (focus jump) from the 0th layer (hereinafter also referred to as L0 layer) 101 to the 1st layer (hereinafter also referred to as L1 layer) 102 in the DVD 1 having a two-layer structure. is there. In the figure, the upper waveform is a signal waveform of a driving 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 FEP6 to the DSP8. ).
[0033]
As a basic operation of the focus jump by the fixed pulse, first, the focus servo loop is kept connected (just turned on) until just before the jump, and a fixed pulse (a driving voltage having a predetermined height: (Acceleration pulse) is output for a predetermined time (acceleration pulse in FIG. 4). The focus servo loop is turned off at the start of the fixed pulse output. Then, the acceleration pulse is stopped when a predetermined time elapses, and the FOD signal output is stopped for a predetermined time (stop in FIG. 4). Thereafter, a fixed pulse (deceleration pulse) having a predetermined magnitude in the reverse direction is output as an FOD signal at a certain time later, and the focus servo loop is turned on again when the FE signal level reaches a set threshold (FIG. 4 deceleration pulse).
[0034]
In the above operation, by applying an acceleration pulse, the objective lens 31 is focused on the first layer 102 from the position where the objective lens 31 is focused on the 0th layer 101 (D0 in FIG. 2) (D1 in FIG. 2). ) And the objective lens 31 is considered to have reached the vicinity of the position of D1 in FIG. 2 when the FE signal level reaches the set threshold value. By turning on the focus servo loop at this position, the first It becomes possible to focus on the layer 102. 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 the objective lens 31 only moves from the position D0 to D1, so that the interlayer switching of the focus is performed. It can be done at high speed.
[0035]
FIG. 6 shows a waveform when performing layer switching (focus jump) from the first layer 102 to the zeroth layer 101 in the DVD 1 having a two-layer structure. In the drawing, the upper waveform is a signal waveform of a driving 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 FEP6 to the DSP8. It is a waveform. As apparent from comparison with the layer switching from the L0 layer 101 to the L1 layer 102 shown in FIG. 5, the polarities of the acceleration pulse and the deceleration pulse are merely opposite to those in FIG. The operation 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 thus detailed description is omitted.
[0036]
As described above, when the focus is switched between layers, the focus jump can be performed at high speed by using the focus jump described with reference to FIGS. There are optical discs in which focus layer switching cannot be performed by focus jump due to eccentricity, thickness unevenness, thickness unevenness between recording / reproducing layers, and the like. In this case, the forced focus re-retraction described below is performed. Note that the case where the switching from the L1 layer 102 to the L0 layer 101 is performed by forcible re-drawing performs almost the same operation as the case of the normal focus pull-in described above with reference to FIG. FIG. 7 illustrates an example in which switching from the L0 layer 101 to the L1 layer 102 is performed by forced re-drawing. The upper waveform in FIG. 7 is a signal waveform of the driving 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 FEP6 to the DSP8. It is a waveform.
[0037]
As is clear from the case of the normal focus pull-in shown in FIG. 4, in the case of the forced focus re-draw for switching from the L0 layer 101 to the L1 layer 102, the objective lens 31 is temporarily raised ( After moving in the up direction to a position closer to the drive upper limit DU than the position D1, it is changed in the down (down) direction, and the FE signal exceeds the set threshold value while moving in the down direction. The focus loop is on. Thus, by detecting the FE signal after the objective lens 31 is positioned closer to the drive upper limit DU than the position D1, the L1 layer 102 where the focus loop is first turned on can be focused.
[0038]
The layer switching to the L1 layer 102 by the forced re-drawing of the focus is performed by the following steps.
[0039]
(1) First, the focus servo is temporarily turned off (loop OFF in FIG. 7).
[0040]
{Circle around (2)} In order to perform the pull-in in the direction opposite to the normal focus pull-in, the polarities of necessary parameters (such as a drive value for determining the drive direction and an FE threshold for setting the pull-in level) are switched.
[0041]
(3) Raise the FOD voltage and raise the objective lens 31 to the driving upper limit DU. Then, gradually lower the FOD voltage to drive the objective lens 31 downward (up → down in FIG. 7). When the FE signal once rises and then falls rapidly and falls below a preset threshold value (the pull-in point position in FIG. 7), the focus servo loop is connected (focus on) to Focusing can be performed on the layer 102.
[0042]
{Circle around (4)} Other operations necessary for reproduction (omitted because they are not directly related to the present invention) are executed and the process ends.
[0043]
In the description of the above embodiment, the polarity of the FOD signal and the threshold value of the FE signal are inverted by software. However, in the block diagram shown in FIG. The FOD signal that is a control signal output from the DSP 8 may be inverted and supplied to the actuator driver 5 by hardware inversion.
[0044]
In the present invention, when the focus is switched between layers, the focus jump and the forced re-drawing described above are selectively switched and executed.
[0045]
In other words, normal interlayer switching uses focus jumps that are overwhelmingly faster in interlayer switching, but when focus jumps fail due to disc thickness irregularities, disc layer thickness irregularities, disc surface deflection, etc. Performs forced re-drawing of the focus.
[0046]
As a reference for switching to focus forced redrawing, for example, the normal number of focus jump executions is counted, and when the count (retry number) exceeds a certain number, focus forced redrawing is used. Switch to selectively.
[0047]
This specific switching operation will be described with reference to the flowchart shown in FIG. Here, the description will be made on the assumption that when the focus jump fails three times, the focus is switched to the forced re-drawing. When an interlayer switching signal is supplied from a signal processing circuit (not shown) to the CPU 7, the CPU 7 instructs the DSP 8 to perform interlayer switching.
[0048]
First, the values of the number of focus jump failures (jumpL0) to the L0 layer 101 and the number of focus jump failures (jumpL1) to the L1 layer 102 are initialized (step 11). This initialization operation is preferably performed in advance when the power is turned on or when the optical disc 1 is inserted, not after an instruction for switching between layers is received.
[0049]
If the layer switching instruction is a focus switching from the L1 layer 102 to the L0 layer 101 (step 12 → Yes), the number of focus jump failures (jumpL0) to the L0 layer 101 is confirmed, and must be 3 or more. If (step 13 → No), a focus jump to the normal L0 layer 101 is performed (step 14). If this focus jump is successful (step 15 → Yes), 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 focus jump failures (jumpL0) to the L0 layer 101 (step 17), and the process returns to step 13. This process is repeated until the focus jump to the L0 layer 101 succeeds or the focus jump failure count (jumpL0) becomes 3.
[0050]
When the number of focus jump failures (jumpL0) reaches 3 (step 13 → Yes), the process is switched to forced focus redrawing. Forcibly redrawing the focus to the L0 layer 101 performs the same operation as the focus pulling from the initial state described above with reference to FIG. First, the focus servo is turned off (step 18), the objective lens 31 is moved to the drive lower limit DD, the objective lens 31 is raised from there, and the focus servo is turned on when the focus error signal exceeds the threshold value. Focusing is performed (step 19), post-processing is performed, and the process is terminated (step 20).
[0051]
By performing the processing in this way, it is possible to reliably switch the focus to the L0 layer 101 in a short time and regardless of disc manufacturing errors.
[0052]
Next, the case of focus switching 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 failed focus jumps to the L1 layer 102 (jumpL1) is confirmed, and if it is not 3 or more ( Step 21 → No), a focus jump to the normal L1 layer 102 is performed (step 22). If this focus jump is successful (step 23 → Yes), post-processing is performed and the process ends (step 24). When the focus jump to the L1 layer 102 fails (step 23 → No), 1 is added to the number of focus jump failures (jumpL1) to the L1 layer 102 (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 focus jump failures (jumpL1) becomes 3.
[0053]
When the number of focus jump failures (jumpL1) becomes 3 (step 21 → Yes), the processing is switched to focus re-retraction. As described above with reference to FIG. 7, the forced focus re-drawing to the L1 layer 102 is an operation having a polarity opposite to that of the focus pulling from the initial state. First, the focus servo is turned off (step 26), the drive signal value of the objective lens 31 and the polarity of the threshold value of the focus error signal are inverted (step 27), and then the objective lens 31 is moved to the drive upper limit DU. When the objective lens 31 is lowered and the focus error signal becomes equal to or less than the threshold value, the focus servo is turned on to perform focusing (step 28). The value of the inverted drive signal of the objective lens 31 and the focus error signal After the threshold polarity is restored (step 29), post-processing is performed and the process ends (step 30).
[0054]
By performing the processing in this way, it is possible to reliably switch the focus to the L1 layer 102 in a short time and regardless of disc manufacturing errors.
[0055]
In the above-described embodiment, the focus forcible re-drawing is always performed after repeating the focus jump a predetermined number of times (three times). However, for an optical disc that has been subjected to focus re-entry after failing the focus jump a predetermined number of times, there is a high probability that the focus jump will fail when the focus layer is switched again. As a result, it is possible to perform focus layer switching at a higher speed when the forced re-drawing is performed. As another embodiment of the present invention, a description will be given of a case where focus jump is not performed in the second and subsequent focus interlayer switching when the focus forcible re-drawing is performed in the previous focus interlayer switching.
[0056]
For example, after an optical disk 1 is inserted 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 start-up or the reproduction state The number of failed focus jumps when entering and the jump direction (values of jmpL0 and jmpL1 in the flowchart of FIG. 8) are stored, and when the layer needs to be switched next time, they are stored. Depending on the content, focus layer switching is performed from the beginning using forced re-drawing. Specifically, the values of jmpL0 and jmpL1 are held in the CPU 7 until the optical disk 1 is replaced or the optical disk recording / reproducing apparatus is turned off, and step 11 in FIG. 8 is omitted when layer switching is performed. In this case, if the focus jump has failed three or more times during various adjustments at the time of initial startup or the previous layer switching, the forced focus re-drawing is automatically executed.
[0057]
Further, for an optical disc that has failed the focus jump three or more times, the unique identification information for individually identifying the optical disc is read, and the fact that the focus jump cannot be performed together with this unique identification information is stored in the CPU 7 once. For an optical disc that is recognized as being unable to perform a focus jump, even if the optical disc recording / playback device is turned off or the optical disc is replaced, the focus is re-engaged immediately without performing a focus jump. Thus, the focus layer can be switched.
[0058]
【The invention's effect】
The focus interlayer switching method and the optical disk drive apparatus according to the present invention use a focus jump that enables high-speed focus interlayer switching for optical disks with small errors such as eccentricity and thickness unevenness, and cannot perform interlayer switching with a focus jump. Since the focus pull-in is performed with respect to the optical disc, there is an effect that the focus layer switching can be performed surely and as fast as possible in accordance with the characteristics of each optical disc.
[0059]
  MoreAndFor the optical disc that failed the focus jump, it is memorized and the focus switching is performed without performing the focus jump in the next and subsequent focus layer switching. This can be omitted, and there is an effect that the focus layer switching can be performed at a higher speed for an optical disc having a large error.
[Brief description of the drawings]
FIG. 1 of the present inventionTo explain how to switch focus between layersIt is a block diagram which shows one Embodiment of an optical disk drive device.
FIG. 2 is a diagram for explaining in-focus positions 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 an L1 layer to an L0 layer.
FIG. 7 is a graph showing waveforms of an FOD signal and an FE signal when focus pull-in is performed at the time of interlayer switching from the L0 layer to the L1 layer.
FIG. 8 is a flowchart showing an embodiment of the focus interlayer switching method of the present invention.
[Explanation of symbols]
  1 Optical disc (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 controller)
  8 Digital signal processor (focus jumping means, focus pulling means, polarity reversing means, DSP)
  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

Claims (1)

During recording or reproduction of an information signal by irradiating 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 method for switching between layers of focus, wherein the laser beam is switched to focus on the other recording layer when the focus is on,
  A focus jump method for switching between layers of focus by applying acceleration and deceleration pulses to the focus servo system with the servo loop connected,
  Once the focus servo is removed, focus pull-in from the side close to the target layer,
2 focus interlayer switching method,
  If focus layer switching is not successful even after a predetermined number of focus jumps, the result is stored, and when focus layer switching is performed on the optical disc, the focus jump is not performed. A focus interlayer switching method characterized by pulling in.

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