JP2010160864A - Optical recording medium drive, and method of checking the number of recording layers - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correctly check the number of the recording layers of a multilayered recording medium without degrading the performance due to erroneous erasing on the recorded data, for instance. <P>SOLUTION: When checking the number of the recording layers of a loaded optical recording medium, this method checks whether it has a single layer or a number of layers by setting the light to a desirable amount for a single-layer optical recording medium in the first check for a single or multiple layers. When finding that it has a number of layers, it changes the light to a desirable amount for a two-layered optical recording medium, and checks the number of layers of a multiple layered medium as a multiple layer discriminating process. If needed, it repeats to check the number of layers by changing the laser light to the desirable amount for a three-layered optical recording medium, a four-layered optical recording medium, and so on. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical recording medium driving apparatus that performs recording / reproduction on an optical recording medium such as an optical disk, and a method for determining the number of recording layers.

JP 2006-236469 A JP 2006-344301 A JP 2002-352449 A JP 2005-267800 A

  For example, in the case of an optical disc such as a Blu-ray Disc (registered trademark), a single-layer disc having a single recording layer for recording / reproducing information, and a multi-layer disc having a plurality of recording layers have been developed. . In a recording / reproducing apparatus corresponding to a single-layer disc or a multi-layer disc, for example, when an optical disc is loaded, it is necessary to determine the number of recording layers of the optical disc.

Patent Document 1 discloses a method for determining the number of layers in which laser irradiation is performed with the amount of reproduction laser light for a single-layer disc when determining the number of recording layers. Usually, as the number of recording layers increases, it is necessary to increase the laser power (increase the laser light amount) at the time of recording / reproduction, but this is to prevent reproduction deterioration caused by using an excessively large laser light amount.
Patent Document 2 describes that in a so-called focus search operation (operation in which the objective lens is moved up and down in the focus direction), a so-called S-shaped waveform of a focus error signal is detected to detect the number of recording layers.
Patent Documents 3 and 4 describe a spherical aberration correction element, a spherical aberration correction method, and the like.

  As described in Patent Document 1, from the viewpoint of preventing reproduction deterioration, it is appropriate to perform laser irradiation with a light amount suitable for reading information recorded on a single-layer disc when discriminating the number of layers of the disc. is there. However, there are the following problems.

  In discriminating the number of layers of a conventional Blu-ray disc or the like, the maximum number of layers of a commonly used disc is generally two. For this reason, it is possible to obtain a reflected light information signal having a quality sufficient for discriminating the number of layers even when reproduction is performed with a light amount suitable for reading information recorded on a single-layer disc. .

However, recently, in order to secure a larger capacity, introduction of a multilayer disk having three or more layers is being studied. When this multi-layer disc is used, degradation factors such as a decrease in reflectance and the occurrence of a shift in the optimum aberration correction amount in each recording layer must be taken into consideration.
Therefore, unless the reproduction light quantity is set to a value that is considerably large (for example, 2 to 3 times or more) with respect to the light quantity suitable for reading the information recorded on the single-layer disc, the reproduction layer is correctly set due to a decrease in reproduction level or the like. It is expected that it will be difficult to ensure the quality of the reflected light information signal sufficient to determine the number.

  Therefore, in the case of using a multilayer optical recording medium having three or more layers, it is difficult to determine the exact number of layers of the multilayer disc having three or more layers by the method described in Patent Document 1. That is, when laser irradiation is performed with a light amount suitable for reproduction of a single-layer disc and the number of layers is determined using the reflected light information signal, it is possible to determine whether it is one layer or two or more layers. However, in the case of a multi-layer disc having three or more layers, it is difficult to accurately determine the signal change according to each recording layer, and it is difficult to determine the exact number of recording layers.

  Accordingly, an object of the present invention is to provide a technique capable of accurately discriminating the number of recording layers even in a multilayer recording medium such as three layers or four layers without performance deterioration such as erroneous deletion of recorded data. .

  The optical recording medium driving device according to the present invention corresponds to an optical recording medium having a single or a plurality of recording layers, and reproduces or records information by irradiating the mounted optical recording medium with laser light. And a laser driving unit that executes laser light output from the optical head unit with the instructed laser light amount, and a process for determining the number of recording layers of the mounted optical recording medium. Single discriminating process for discriminating whether the number of recording layers is single or plural from reflected light information in a state where the corresponding light quantity is instructed to the laser driving unit and laser light irradiation by the optical head unit is executed. When the number of recording layers is determined to be plural in the single / multiple determination process, the optical head unit is instructed to the laser driving unit the amount of light corresponding to the multiple-layer optical recording medium. Execute laser light irradiation by State, and a control unit for performing a plurality of layers number determination process of determining the number of recording layer from the reflected light information.

Further, the control unit instructs the laser driving unit to supply the light amount corresponding to the two-layer optical recording medium to the laser driving unit as the light amount corresponding to the multi-layer optical recording medium in the multi-layer number determining process.
Further, the control unit instructs the laser driving unit to determine the amount of light according to the two-layer optical recording medium, and performs the laser driving when the determination of the number of recording layers is not completed. The laser drive unit is instructed to input the amount of light corresponding to the optical recording medium having a specific number of layers of three or more as the amount of light corresponding to the multiple-layer optical recording medium, and the multi-layer number determination process is repeated.

In addition, a spherical aberration correction setting unit for laser light is further provided, and the control unit has a substantially intermediate position between the recording layer closest to the laser incident surface and the recording layer farthest from the laser incident surface within the range of the number of recording layers assumed. The spherical aberration correction setting unit sets the spherical aberration so that the spherical aberration is minimized, and the single / multiple discriminating process and the multiple layer number discriminating process are executed.
Alternatively, the control unit performs the single / multiple discrimination process after setting the spherical aberration correction setting unit so that the spherical aberration is minimized in the vicinity of the recording layer in the optical recording medium having a single recording layer, In addition, the spherical aberration correction setting unit is configured so that the spherical aberration is minimized at a substantially intermediate position between the recording layer closest to the laser incident surface and the recording layer farthest from the laser incident surface within the range of the number of recording layers assumed. After the setting, the above-described multi-layer number discrimination process is executed.
Alternatively, the control unit may cause the spherical aberration correction setting unit to perform the recording layer closest to the laser incident surface and the closest laser incident surface within the assumed number of recording layers within the execution period of the multiple layer number discrimination process. Sequentially, spherical aberration correction setting is performed for a plurality of positions between the distant recording layers, and reflected light information corresponding to laser light irradiation is detected, and reflected light information for each spherical aberration correction setting state is detected. The number of recording layers is determined from the detection result.
In the single / multiple discriminating process and the plural-layer number discriminating process, the control unit is configured to obtain an S-shaped signal of a focus error signal obtained as reflected light information when the objective lens of the optical head unit is moved in the focus direction. The number of recording layers is determined by detecting the number of occurrences.

  The method for discriminating the number of recording layers according to the present invention corresponds to an optical recording medium having a single or a plurality of recording layers. As a method for discriminating the number of recording layers of a medium driving device, laser light irradiation is performed on a mounted optical recording medium with a light amount corresponding to the optical recording medium having a single recording layer, and the number of recording layers is simply determined from reflected light information. If the number of recording layers is determined to be plural by the single / multiple determination process and the single / multiple determination process, the laser drive unit uses a light amount corresponding to the multi-layer optical recording medium. Laser beam irradiation is performed, and a multiple layer number discrimination process for discriminating the number of recording layers from the reflected light information is performed.

That is, in the present invention described above, when determining the number of recording layers of the mounted optical recording medium, the light quantity suitable for an optical recording medium having a single recording layer (for example, a single-layer disc) is first set by single / multiple determination processing. In the state, it is determined whether it is a single layer or a plurality of layers. If the determination result is a plurality of layers, the number of layers is determined by changing the light amount to be suitable for a two-layer optical recording medium (that is, increasing the amount of light) as the number of layers determination processing. Do. In some cases, the laser light quantity corresponding to a three-layer optical recording medium, a four-layer optical recording medium, or the like is sequentially changed (increased light quantity), and the multiple-layer number discrimination process is repeated.
As a result, a reflected light information signal with an appropriate signal quality can be obtained for each of the single-layer optical recording medium, double-layer optical recording medium,. Therefore, avoid irradiation with an excessive amount of laser light.
Further, by changing the amount of laser light and appropriately changing the spherical aberration correction setting, a reflected light information signal having an appropriate signal quality can be obtained.

According to the present invention, in order to ensure the quality of the reflected light information signal required to determine the number of layers, the number of layers is increased while sequentially increasing the amount of laser light according to the number of layers of the mounted optical recording medium. Since the discrimination is performed, the number of layers can be accurately discriminated even when a multilayer optical recording medium having three layers, four layers or more is used.
In addition, changing the spherical aberration correction setting also contributes to accurate layer number discrimination.

  Further, when the number of layers of the mounted optical recording medium is one, the layer number determination is completed only by the single / multiple determination process using the reproduction laser light amount suitable for reading the information recorded on the single-layer optical recording medium. . When the number of layers of the mounted optical recording medium is two, the layer number determination is completed by a plurality of layer number determination process using the reproduction laser light quantity according to the two-layer optical recording medium. In the case of three or more layers, the multiple layer number discrimination process may be repeated while changing the reproduction laser light quantity. Depending on these processing operations, the layer number discriminating operation with an excessively large amount of reproduction laser light is not performed on the mounted optical recording medium, and the recorded data is erroneously erased, the recording state is deteriorated, or The layer number discrimination can be completed without causing performance degradation such as degradation or breakage of preformat information.

It is a block diagram of the principal part of the disk drive apparatus of embodiment of this invention. It is a flowchart of the layer number discrimination | determination process of 1st Embodiment. It is explanatory drawing of the layer number discrimination | determination operation | movement of 1st Embodiment. It is a flowchart of the layer number discrimination | determination process of 2nd Embodiment. It is explanatory drawing of the layer number discrimination | determination operation | movement of 2nd Embodiment. It is a flowchart of the layer number discrimination | determination process of 3rd Embodiment. It is explanatory drawing of the layer number discrimination | determination operation | movement of 3rd Embodiment. It is a flowchart of the layer number discrimination | determination process of 4th Embodiment. It is explanatory drawing of the layer number discrimination | determination operation | movement of 4th Embodiment. It is a flowchart of the layer number discrimination | determination process of 5th Embodiment. It is explanatory drawing of the layer number discrimination | determination operation | movement of 5th Embodiment.

Hereinafter, embodiments of the present invention will be described in the following order.
[1. Configuration of disk drive unit]
[2. Discrimination of the number of layers in the first embodiment]
[3. Discrimination of the number of layers in the second embodiment]
[4. Discrimination of the number of layers in the third embodiment]
[5. Discrimination of the number of layers in the fourth embodiment]
[6. Discrimination of the number of layers in the fifth embodiment]
[7. Modified example]

[1. Configuration of disk drive unit]

As an embodiment of the optical recording medium driving apparatus of the present invention, a disk drive apparatus that performs recording / reproduction corresponding to a single-layer or multi-layer Blu-ray disc is taken as an example.
FIG. 1 shows a block diagram of a main part of the disk drive device. Note that FIG. 1 shows only a part particularly related to the number of recording layers, and a configuration such as a recording / reproducing system that performs encoding / decoding processing at the time of recording / reproducing, an external interface, and the like is omitted.

An optical disc 90 shown in FIG. 1 is a high-density optical disc called a Blu-ray disc, for example.
An example of physical parameters of the optical disc 90 (Blu-ray disc) will be described.
The optical disc 90 of this example has a disc size of 120 mm in diameter and a disc thickness of 1.2 mm. In other words, these are the same as CD (Compact Disc) type discs and DVD (Digital Versatile Disc) type discs in terms of external appearance.
A so-called blue laser is used as a recording / reproducing laser, and the optical system has a high NA (for example, NA = 0.85), and a narrow track pitch (for example, track pitch = 0.32 μm). By realizing a high linear density (for example, a recording linear density of 0.12 μm), a user data capacity of about 23 G to 25 G bytes is realized in one recording layer in a disk having a diameter of 12 cm.

Such an optical disk 90 of this example includes a single-layer disk with one recording layer, two-layer recording layers, three-layers ... n-layer two-layer disks, three-layer disks ... n-layer disks ( For example, there is a type as an 8-layer disc. A disc having two or more layers is collectively referred to as a “multi-layer disc”.
Of course, the recording capacity can be greatly increased by providing a large number of recording layers.

The configuration of the disk drive device of the present example for recording / reproducing data on the disk 90 will be described.
The optical disk 90 is loaded on a turntable (not shown) and is rotationally driven by the spindle motor 2 at a constant linear velocity (CLV) during recording / reproducing operation.
The optical pickup unit (optical head) 3 performs recording / reproduction on the recording layer on the optical disk 90.

For example, when the optical disc 90 is a recordable disc such as a rewritable disc or a write-once disc, the recording layer of the optical disc 90 is irradiated with a laser having a recording power modulated by the recording data to form a recording mark row. It will be done.
In addition, when the optical disk 90 is either a read-only disk or a recordable disk, the recording layer of the optical disk 90 is irradiated with a laser beam with a reproduction power, and the reflected light information is detected to record on the recording layer. The read information is read out.

  In the optical pickup unit 3, an objective lens 5, a biaxial actuator 4, a laser diode 6, a beam splitter 7, a spherical aberration correction element 8, a mirror 9, a sensor lens 10, a photoelectric conversion element (photo detector) 11, and the like are provided.

The laser diode 6 outputs, for example, a so-called blue laser having a wavelength of 405 nm. The NA by the optical system is 0.85.
The laser diode 6 is driven to emit laser light by a laser drive signal (drive current) from a laser driver 18.
The laser light output from the laser diode 6 passes through the beam splitter 7, travels through the spherical aberration adjustment correction element (expander lens) 8, is reflected by the mirror 9, and is irradiated onto the optical disk 90 from the objective lens 5. Is done.
Reflected light from the optical disk 90 is reflected by the beam splitter 7 through the optical path of the objective lens 5, the mirror 9, and the spherical aberration correction element 8, and enters the photoelectric conversion element 11 through the sensor lens 10.

The objective lens 5 is held by a biaxial actuator 4 so as to be movable in the tracking direction and the focus direction. Since the objective lens 5 can be moved in the focus direction and the tracking direction by the biaxial actuator 4, the focus servo and tracking servo operations can be executed.
The entire optical pickup unit 3 can be moved in the disk radial direction by a sled motor 12.

The spherical aberration correction element 8 has a function of changing the diameter of the laser beam. That is, the expander lens constituting the spherical aberration correction element 8 is movable in the optical axis direction, and the distance between the spherical aberration correction element 8 and the objective lens 5 is varied by this movement, and is applied to the optical disc 90. The diameter of the laser beam is adjusted.
That is, the spherical aberration correction can be executed by controlling the spherical aberration correction element driving driver 17 to perform the back-and-forth movement with respect to the expander lens of the spherical aberration correction element 8.

Reflected light information from the optical disk 90 is detected by the photoelectric conversion element 11, converted into an electrical signal corresponding to the amount of received light, and supplied to the analog signal processing unit 13.
The analog signal processing unit 13 includes a current-voltage conversion circuit, a matrix calculation / amplification circuit, and the like corresponding to output currents from a plurality of light receiving elements as the photoelectric conversion element 11, and generates necessary signals by matrix calculation processing.
For example, a high-frequency signal (also referred to as a reproduction RF signal) corresponding to reproduction data, a focus error signal for servo control, a tracking error signal, a total light amount signal, and the like are generated.
If the optical disk 90 is a writable disk and the wobbling groove is not formed, it is pushed as a signal related to wobbling of the groove, that is, a signal for detecting information such as an address recorded as wobbling. Generate a pull signal.

The reproduction RF signal output from the analog signal processing unit 13 is supplied to a reproduction signal processing system (not shown), and binarization, reproduction clock generation, decoding, error correction, and the like are performed, and reproduction data is generated.
The push-pull signal is supplied to an address decoding system (not shown) to generate address data.
FIG. 1 shows a focus error signal FE, a tracking error signal TE, and a total light amount signal, but these are supplied to the controller 15 for use in servo control, layer number determination processing described later, and the like.

The focus error signal FE is also supplied to the S-shaped detection counter 14. The S-shaped detection counter 14 detects and counts a so-called S-shaped waveform for the focus error signal FE. The S-shaped waveform is a waveform that appears as the focus error signal FE when the objective lens 5 is forcibly moved in the focus direction (during the focus search operation).
The S-shaped detection counter 14 counts the number of S-shaped waveforms that appear in the layer number determination process described later, and supplies the count value to the controller 15.

The controller 15 controls the driving of the optical pickup unit 3 and the spindle motor 2 during recording and reproduction, various servo operations, and the like.
The controller 15 generates various servo drive signals for focus, tracking, and thread from the focus error signal FE and the tracking error signal TE, and executes the servo operation. That is, a focus drive signal and a tracking drive signal are generated according to the focus error signal FE and the tracking error signal TE and supplied to the biaxial actuator driver 16. The biaxial actuator driver 16 drives the focus coil and tracking coil of the biaxial actuator 4 in accordance with the focus drive signal and tracking drive signal. As a result, servo movement in the focus direction and tracking direction of the objective lens 5 is performed. That is, a tracking servo loop and a focus servo loop are formed by the optical pickup unit 3, the analog signal processing unit 13, the controller 15, the biaxial actuator driver 16, and the biaxial actuator 4.

Further, in order to execute the focus servo, as a precondition, focus search must be performed and the objective lens 5 must be positioned within the focus pull-in range (in the linear region of the S-shaped waveform).
At the time of focus search, the controller 15 gives a search drive signal to the biaxial actuator driver 16 with the focus servo loop turned off to forcibly move the objective lens 5 in the focus direction. Instruct. Then, the focus servo loop is turned on at the position where the S-shaped waveform is observed in the focus error signal FE (near the zero cross point in the linear region of the S-shaped waveform), and servo pull-in is executed.

In the present embodiment, the S-shaped waveform of the focus error signal FE is used for recording layer detection in the later-described layer number discrimination process. For this reason, the forced movement of the objective lens 5 similar to the focus search operation is executed in the layer number discrimination process.
However, in the layer number determination process, since the focus search operation is not moved for focus pull-in, it is simply referred to as “focus movement” as meaning that the objective lens 5 is forcibly moved in the focus direction. Use words.

  Further, the controller 15 generates a thread drive signal based on a thread error signal obtained as a low frequency component of the tracking error signal TE, an access execution request, and the like, and controls the thread motor driver 19. The thread motor driver 19 drives the thread motor 12 based on the thread drive signal from the controller 15. Thereby, the required slide movement of the optical pickup unit 3 is performed.

The controller 15 also controls the spindle motor driver 20 to rotate the spindle motor 2 by, for example, CLV.
In the CLV rotation servo operation of the spindle motor 2, the controller 15 obtains a reproduction clock or wobble clock obtained from a reproduction system (not shown) as current rotation speed information of the spindle motor 2, and compares it with predetermined CLV reference speed information. As a result, a spindle error signal is generated. Then, the spindle motor driver 20 is controlled based on the spindle error signal.

The controller 15 instructs the laser driver 18 on the amount of laser light.
The laser driver 18 supplies a laser drive current to the laser diode 6 based on a strategy waveform formed according to recording data supplied from a recording processing system circuit (not shown) during recording. As a result, laser light emission corresponding to the recording data is performed.
At the time of reproduction, the laser driver 18 gives a laser driving current so that the laser diode 6 emits light continuously based on the control of the controller 15.
The laser driver 18 includes a so-called APC circuit (Auto Power Control), and the laser output is not dependent on temperature or the like while monitoring the laser output power by the output of the laser power monitoring detector provided in the optical pickup unit 3. Control to be constant. Here, the target value (recording laser power / reproducing laser power) of the laser output at the time of recording and at the time of reproduction is given from the controller 15 and controlled so that the respective laser output levels become the target values. Also in the later-described layer number discrimination process, the laser power is set by an instruction from the controller 15.

Further, the controller 15 controls the spherical aberration correction element driving driver 18 to drive the spherical aberration correction element 8 and execute spherical aberration correction.
In the later-described layer number discrimination process, a predetermined position in the thickness direction of the optical disc 90 is designated, and correction is made so that the spherical aberration is minimized.

For example, the controller 15 is provided with a layer number determination processing unit 15a as software for executing a layer number determination process described later. By the processing executed by the layer number determination processing unit 15a, the focus movement, spherical aberration correction, count value determination of the S-shaped detection counter 14, and the like described above are performed, and the number of layers is determined.

[2. Discrimination of the number of layers in the first embodiment]

In the disc drive apparatus 1 as described above, when the optical disc 90 is loaded, it is determined how many recording layers the optical disc 90 has.
An example of the layer number discrimination process for discriminating the number of recording layers for the mounted optical disk 90 will be described below.

The outline of the layer number discrimination process of the first embodiment is as follows.
First, with the reproduction laser light amount adjusted to a first light amount suitable for reading information recorded on a single-layer disc, the number of recording layers of the mounted optical disc 90 is one or more than two layers. Single / multiple discrimination processing is performed.
If it is determined that the number of recording layers is one, the process ends here.
If it is determined that the number of recording layers is a multi-layer disc, the reproduction laser light amount is then changed to a second light amount (> first light amount) suitable for reading information recorded on the two-layer disc. Then, a multiple layer number discrimination process for discriminating the number of layers of the mounted optical disk 90 is performed.
If it is determined that the number of layers is two, the process ends here. Alternatively, even when it is determined that the disk is a multilayer disk other than two layers, when the number of usable multilayer media is limited to one type (for example, only four layers), the number of layers is larger than two layers. When the disc is determined to be a disc, the number of layers is uniquely determined, and the process can be terminated at this stage.

The layer number discrimination processing according to the first embodiment will be described with reference to FIGS.
In the first embodiment, a processing example suitable for a case where the optical disk 90 that may be mounted on the disk drive apparatus 1 is only a single-layer disk, a double-layer disk, and a four-layer disk will be described. For example, this is a processing example based on the premise that there are three types of optical disks 90 distributed in the market.
Note that only one-layer disc, two-layer disc, and three-layer disc may be used. In this case, the “four-layer” portion may be replaced with “three-layer” in the processing described below. Almost the same algorithm can be applied.

FIG. 2 shows the processing of the layer number discrimination processing unit 15a in the controller 15.
When the optical disk 90 is inserted or when the power of the disk drive device 1 is turned on, a routine for determining the number of layers of the optical disk 90 is started, and the number of disk layers is determined according to the following procedure.
In the following, the terms recording layers L0, L1, L2, L3... Are used.
The recording layer L0 indicates the recording layer of a single-layer disc or the first recording layer of a multilayer disc. The recording layers L1, L2, L3,... Are the second, third, fourth,.
In the case of a Blu-ray disc, the recording layer L0 is the recording layer farthest from the laser incident surface, and the recording layers L1, L2, L3,.

First, in step F101, the controller 15 controls the spherical aberration correction element driving driver 17 to set the aberration correction setting to the four-layer intermediate position.
Here, the four-layer intermediate position is a substantially intermediate position between the recording layer closest to the laser incident surface and the recording layer farthest from the laser incident surface within the range of the number of recording layers assumed. In this example, a one-layer disc, a two-layer disc, and a four-layer disc are assumed, and the recording layer closest to the laser incident surface is the fourth recording layer L3 of the four-layer disc. The recording layer farthest from the laser incident surface is the recording layer L0. In other words, the position is an intermediate position between the recording layer L0 and the recording layer L3, and the spherical aberration correction element drive driver 17 drives the spherical aberration correction element 8 so that the spherical aberration is minimized at this position.

Further, the controller 15 sets the reproduction laser light quantity in step F102. For example, first, the spindle motor driver 20 is controlled so that the optical disk 90 is rotated at a predetermined rotational speed. Then, the laser driver 18 is instructed with a first light amount (for example, 0.3 mW) suitable for reading information recorded on the single-layer disc, and the laser diode 6 outputs a blue laser having a wavelength of 405 nm.
Here, the layer number discrimination process of FIG. 2 is performed while the optical disk 90 is rotated by the spindle motor 2, but the layer number discrimination process may be performed while the optical disk 90 is stopped. Good. That is, a processing example in which the spindle motor 2 is started after the layer number discrimination processing in FIG. The same applies to the second to fifth embodiments described later.

Next, in step F103, the controller 15 supplies a focus search signal to the biaxial actuator driver 16, and causes the biaxial actuator 4 to perform a focus movement that forcibly raises and lowers the objective lens 5.
At the time of this focus movement, as the focus error signal FE, a sinusoidal output change (so-called S-shaped waveform) is observed every time the focal position passes through the recording layer. However, the S-shaped waveform is also observed due to the surface reflection of the laser incident surface of the optical disk 90.
The number of S-shaped waveforms observed is counted by the S-shaped detection counter 14, but the controller 15 captures this count value in step F104.
In steps F103 and F104, the number of occurrences of the S-shaped waveform is counted when the objective lens 5 moves in either one of the upward movement and the downward movement.

FIG. 3A shows the waveform of the focus error signal FE observed when a single-layer disc, a double-layer disc, and a four-layer disc are mounted.
In the drawing, a position CT indicates a spherical aberration correction position. As described above, in consideration of the correspondence to the four-layer disc, the adjustment position of the spherical aberration correcting element is adjusted to the vicinity of the two recording layers L1 and L2 in the middle of the four-layer disc.

If the objective lens 5 is moved in the upward direction (direction approaching the optical disc 90) when a single-layer disc is mounted, a relatively small S-shaped waveform is first generated as surface reflection as shown in the figure. May be observed. Thereafter, when the in-focus position passes through the recording layer L0, an S-shaped waveform corresponding to the recording layer L0 is obtained.
For example, the S-shaped detection counter 14 compares the threshold values th1 and th2 shown in FIG. 3 with the focus error signal FE, and counts up as one S-shaped waveform generation by exceeding both the threshold values th1 and th2. That is, when the level of the S-shaped signal exceeds the detection threshold levels th1 and th2 on the + side and − side once, the detection count value is incremented by one.

  As shown in the figure, a signal corresponding to an S-shaped signal may be generated as a reflection signal from the disk surface. However, it is necessary to observe the total light amount signal together, or to consider the interval at which the signal is detected. Thus, this surface reflection signal can be excluded during counting, and only the S-shaped signal corresponding to the recording layer can be extracted.

Further, as shown in the figure, when a two-layer disc is mounted, a relatively small S-shaped waveform is observed as surface reflection, and thereafter, when the in-focus position passes through the recording layers L1 and L0, the recording layers respectively. S-shaped waveforms corresponding to L1 and L0 are obtained.
Further, when a four-layer disc is mounted, an S-shaped waveform of surface reflection is observed, and thereafter, an S-shaped waveform is obtained when the in-focus position passes through the recording layers L3, L2, L1, and L0. .

Here, since the reproduction laser light amount is a first light amount suitable for a single-layer disc, when a single-layer disc is mounted, an S-shaped waveform corresponding to the recording layer L0 is obtained with a large amplitude. .
On the other hand, since the reproduction laser light amount is the first light amount, when a two-layer disc or a four-layer disc is loaded, the amplitude of the S-shaped waveform corresponding to each recording layer is relatively small.
The amplitude level is also related to the spherical aberration correction position CT, and the larger the S-shaped waveform corresponding to the recording layer near the spherical aberration correction position CT, the larger the amplitude level is obtained.

In this case, if a single-layer disc is loaded, the count value by the S-curve detection counter 14 is obtained as “1”, and since the S-curve amplitude is good, the count value is a highly reliable value. Become.
That is, when the reproduction light quantity is set to the first light quantity, the S layer signal is detected with sufficient amplitude only at the timing of passing through the recording layer because the reflectance of the disk is high in the single-layer disk, and the detection count value is “1”. Therefore, it can be judged without any problem.
Accordingly, in step F105, when the count value = 1, the controller 15 proceeds to step F106, determines that the mounted optical disk 90 is a single-layer disk, and ends the layer number determination process of FIG.
In this case, normally, the data can be recorded / reproduced after continuously performing the calibration operation of various parameters while the reproduction laser light amount is kept at the first light amount.

  On the other hand, if the detected count value of the S-shaped signal is 2 or more, the controller 15 determines that the loaded optical disk 90 is a multi-layer disk having two or more layers, and proceeds to the processing after step F107.

As described above, steps F101 to F106 are performed as a single / multiple discriminating process. In the case of a single-layer disc, the single-disc discriminating process ends the number-of-layers discriminating process. A process for determining the number of multiple layers after F107 is executed.
As shown in FIG. 3A, the multi-layer number discrimination process is executed in the case of a two-layer or four-layer multi-layer disc, the amplitude level of the S-shaped waveform is reduced, and the count value is reliable. This is because it cannot be said.

This will be described.
Speaking of dual-layer discs, the reflectivity of the medium is large enough to detect the S-shaped signal, so the S-shaped signal is correctly detected at the timing of passing through the two recording / reproducing surfaces, and the count value is The detection result corresponding to the number of layers is obtained.
However, in the case of a four-layer disc, since the reflectivity of the medium is low, the amplitude of the S-shaped signal when passing through the recording layer is small. In addition, in the two recording layers L0 and L3 other than the two intermediate recording layers L1 and L2, since the spherical aberration is larger than that in the two intermediate recording layers L1 and L2, the amplitude tends to further decrease. is there.
For this reason, the S-shaped signal can be detected correctly at the timing of passing through the two intermediate recording layers L1 and L2, but the amplitude level of the S-shaped signal is detected in the recording layers L0 and L3 which are the lowermost layer and the uppermost layer. It is almost the same as the threshold level and may not be detected.
If the S-shaped signal is not correctly detected in the recording layers L0 and L3, the detection count value is “2” to “3”, so that it can be determined that the medium has two or more layers. Whether it is a four-layer disc or a two-layer disc cannot be determined yet.

  In order to prevent detection errors in a four-layer disc, it is conceivable to set the detection threshold levels th1 and th2 small. However, if the detection threshold level is too small, erroneous detection occurs when noise or signal fluctuations occur. Since there is a possibility of erroneous determination such as 1 layer → 2 layer, 2 layer → 4 layer, there is a limit to lowering the detection threshold level.

  For this reason, when the count value is not 1 in step F105, it is determined that the determination result is a multi-layer disc, and the number of layers is determined in the multi-layer number determination process after step F107.

In Step F107, the controller 15 controls the laser driver 18 to change the reproduction laser light amount to a second light amount (for example, 0.6 mW) suitable for reading information recorded on the two-layer disc.
In step F108, the controller 15 supplies a search signal to the biaxial actuator driver 16, and again moves the objective lens 5 up and down.
At the time of the focus movement, the S-shaped waveform of the focus error signal FE is similarly observed, and the S-shaped waveform counter is counted by the S-shaped detection counter 14, so that the controller 15 captures the count value in step F109.

  FIG. 3B shows the waveform of the focus error signal FE that is observed when the two-layer disc and the four-layer disc are mounted during the plural-layer number discrimination process.

If the objective lens 5 is moved in the upward direction (direction approaching the optical disc 90) when a two-layer disc is mounted, a relatively small S-shaped waveform is first generated as surface reflection as shown in the figure. S-shaped waveforms corresponding to the recording layers L1 and L0 are obtained when the in-focus position passes through the recording layers L1 and L0.
In this case, since the reproduction laser light amount is the second light amount corresponding to the two-layer disc, as shown in FIG. 3A, an S-shaped waveform with a large amplitude can be obtained. become.
In addition, when a four-layer disc is mounted, an S-shaped waveform of surface reflection is observed, and thereafter an S-shaped waveform is obtained when the in-focus position passes through the recording layers L3, L2, L1, and L0. It is done. Since the laser light is the second light quantity, the S-shaped waveform amplitude is smaller than that in the case of the two-layer disc.

If the detection count value of the number of occurrences of the S-shaped signal is “2” in step F110, the controller 15 proceeds to step F111, determines that the mounted optical disk 90 is a two-layer disk, and determines the number of layers. Complete the operation.
Alternatively, when the detection count value is “3” or more, it is determined that the mounted optical disk 90 is a four-layer disk, and in this case also, the disk layer number determination operation is completed.

In this case, since the laser light is the second light amount, the amplitude level of the S-shaped signal increases in the double-layer disc, and a more accurate S-shaped detection count becomes possible. In the case of a four-layer disc as well, the amplitude level of the S-shaped signal is similarly increased, and an amplitude level that does not cause a detection error is obtained even in the recording layers L0 and L3 having a relatively low amplitude level. For this reason, since the S-curve detection count value is “4”, it is possible to accurately discriminate between the two-layer disc and the four-layer disc at this stage.
Therefore, the detected count value has high reliability, and when the count value is “2”, it can be accurately determined as a two-layer disc, and when it is not “2”, it can be determined as a four-layer disc.

  In the case where it is determined that the disc is a four-layer disc by the determination with the second light amount, a light amount suitable for reading information recorded on the four-layer disc (for example, for the purpose of more accurate discrimination (for example, It is also possible as an optional operation to count the number of occurrences of the S-shaped signal accompanying the focus movement operation again after changing to 1.0 mW).

As described above, according to the number-of-layers discrimination process of the first embodiment, it is possible to accurately discriminate the number of disc layers when it is necessary to deal with a multilayer optical disc such as four layers.
That is, in order to ensure the quality of the focus error signal FE that is necessary for determining the number of layers, the number of layers is determined while sequentially increasing the amount of laser light to be reproduced according to the number of layers of the mounted optical disk 90. Therefore, even when a four-layer disc or the like (which can be applied to a three-layer disc) is used, it is possible to determine the number of layers with high accuracy.

In addition, when the mounted optical disk 90 is a single-layer disk, the number of layers is discriminated with a first light amount suitable for reading information recorded on the single-layer disk, and the higher light amount is applied to the single-layer disk. Do not irradiate. In the case of a multi-layer disc having two or more layers, the number of layers is discriminated with the second light amount, and therefore, laser irradiation with an excessive light amount is not performed on the two-layer disc.
That is, the layer number discriminating operation is not performed with a reproduction laser light amount that is excessively larger than necessary in accordance with the layer number type of the mounted optical disk 90. Therefore, it is possible to complete the layer number determination without causing performance deterioration such as erroneous erasure of recorded data, deterioration of a recording state, deterioration of preformat information, or damage.

In the above processing example, the S-shaped signal of the focus error signal FE is used to determine the number of layers, but it is also possible to use a light amount sum signal of reflected light. In the case of the light amount summation signal, the amplitude level becomes maximum when the recording layer is in a focused state. Accordingly, if the number of times the total light amount signal exceeds a predetermined threshold during focus movement is counted, the count value of the number of recording layers is obtained.
However, since it is generally considered that the S-shaped signal of the focus error is more sensitive (S / N is better), particularly when a multilayer optical disk such as four layers is used, the S of the focus error signal is used. The improvement of the layer number discrimination accuracy can be expected by adopting the method using the character signal.

[3. Discrimination of the number of layers in the second embodiment]

The layer number discrimination process of the second embodiment will be described with reference to FIGS.
The processing example of the second embodiment is more accurate determination even when the number of layers is determined by the first light quantity and the second light quantity, as in the layer number determination process of the first embodiment. This process is suitable for cases where there are many types of multi-layer discs that can be used, and when there is uncertainty in order to accurately determine the number of layers in the second light quantity It is an example.

  In the second embodiment, a processing example suitable for the case where the optical disk 90 that may be mounted on the disk drive device 1 is a single-layer disk, a dual-layer disk, a triple-layer disk, or a four-layer disk. Indicates. For example, this is a processing example based on the premise that there are four types of optical disks 90 distributed in the market.

FIG. 4 shows the processing of the layer number discrimination processing unit 15 a in the controller 15.
When the optical disk 90 is inserted or when the power of the disk drive device 1 is turned on, a routine for determining the number of layers of the optical disk 90 is started, and the number of disk layers is determined according to the following procedure.
Note that steps F101 to F111 in FIG. 4 are the same as those in FIG.

In the processing example of FIG. 4, if the count number of the S-shaped waveform is not “2” in step F110, a three-layer disc or a four-layer disc is assumed on the assumption that there are four types of layers as described above. It will be considered.
Therefore, if the layer number determination does not end in step F106 or F111, the controller 15 proceeds from step F110 to F121, and further performs a multiple layer number determination process.
In step F121, the controller 15 controls the laser driver 18 to change the reproduction laser light amount to a third light amount (for example, 0.8 mW) suitable for reading information recorded on the three-layer disc.
In step F122, the controller 15 supplies a search signal to the biaxial actuator driver 16 to move the objective lens 5 up and down.
At the time of the focus movement, the S-shaped waveform of the focus error signal FE is similarly observed, and the S-shaped waveform counter is counted by the S-shaped detection counter 14, so that the controller 15 captures the count value in step F123.

Here, when the detection count value of the number of occurrences of the S-shaped signal is “3”, the controller 15 proceeds from step F124 to F125, determines that the mounted optical disk 90 is a three-layer disk, and determines the number of layers. Complete the operation.
Alternatively, if the detected count value is greater than “3”, the controller 15 proceeds from step F124 to F126 to F128, and determines that the mounted optical disk 90 is a four-layer disk. In this case, the disk layer number determination operation is also completed. To do.

FIGS. 5A, 5B, and 5C show the S-shaped waveform detected.
In both cases, the spherical aberration correction position CT is a substantially intermediate position between the recording layers L0 and L3 when a four-layer disc is assumed.

FIG. 5A shows a focus error signal waveform observed when the focus is moved in step F103 in the first light quantity state.
When each of the 1-layer disc, 2-layer disc, 3-layer disc, and 4-layer disc is loaded, an S-shaped waveform is observed corresponding to each recording layer. However, since the laser output is performed with the first light amount corresponding to the single-layer disc, an S-shaped waveform having a substantially good amplitude level can be obtained with the single-layer disc and the double-layer disc. The amplitude of the disc is decreasing. In particular, the amplitude drop is significant in the recording layers L0 and L3 that are away from the spherical aberration correction position CT.
Therefore, only when the count value = 1 in step F105, the determination is made in step F106 that the disc is a single-layer disc.

When it is determined that the disc is a multi-layer disc, a multi-layer number discrimination process after step F107 is performed. In this case, the reproduction laser light amount is set as a second light amount corresponding to the two-layer disc. As a result, the focus error signal waveform observed when the focus is moved in step F108 is as shown in FIG.
That is, when each of the two-layer disc, the three-layer disc, and the four-layer disc is loaded, an S-shaped waveform is observed corresponding to each recording layer. In particular, an S-shaped waveform having a sufficient amplitude level can be obtained for discriminating between a dual-layer disc and a multilayer disc having more than that.

Accordingly, if the count value is “2” at this time, the determination result is determined to be a double-layer disc in step F111.
Further, when the count value is “3” or “4”, it may be determined that the disc is a three-layer disc or a four-layer disc, respectively. However, as in the first embodiment described above, there are a plurality of layer type types. In other words, the number of layers is further determined because it cannot be uniquely determined and more accurate determination is expected.

Therefore, in step F121, the reproduction laser light amount is set to a third light amount corresponding to the three-layer disc. As a result, the focus error signal waveform observed when the focus is moved in step F122 is as shown in FIG.
That is, when each of the three-layer disc and the four-layer disc is mounted, an S-shaped waveform having a sufficient amplitude corresponding to each recording layer is observed. Thus, when the count value is “3” or “4”, it can be accurately determined that the disc is a three-layer disc or a four-layer disc, respectively.

  As described above, when it is determined that the disc is a multi-layer disc (here, a three-layer disc or a four-layer disc), a layer number discriminating operation (re-multi-layer number discriminating process) at the third reproduction light quantity is added. This makes it possible to determine the number of disk layers with high accuracy when it is necessary to support a plurality of types of multilayer disks.

Note that when the S-shaped detection count is performed with the third light quantity, the amplitude of the focus error S-shaped signal becomes large due to the influence of spherical aberration in a multi-layer disc depending on the recording layer. The following cases can be considered.
As a countermeasure in that case, when the count value taken in step F123 becomes less than 3, the process proceeds from step F124 to F126 to F127, and in step F127, the detection threshold values th1 and th2 for S-curve detection count are lowered. The process returns to step F122. In this case, the thresholds th1 and th2 are lowered within a range in which the possibility of erroneous detection due to noise or signal fluctuation is small.
Then, again from step F122, the S-shaped detection count operation with the third light quantity is retried. This improves the accuracy of discriminating whether the disc is a three-layer disc or a four-layer disc.

As a modification, it is also possible to lower the detection threshold level for the S-shaped detection count when the S-shaped detection count at the third reproduction light amount is first performed.
However, the detection threshold level for the S-shaped detection count can be lowered only when the S-shaped detection count is performed with the third reproduction light quantity. Accordingly, it is possible to prevent an increase in the risk of erroneous determination of 1 layer → 2 layers, 2 layers → 3 layers, when determining the number of layers with the first light amount or the second light amount.

Further, when it is determined that the disk is a four-layer disk by the determination with the third light quantity corresponding to the three-layer disk, further confirmation processing may be performed for the purpose of more accurate determination. . In other words, it is also possible as an optional operation to change the number of occurrences of the S-shaped signal according to the focus movement again after changing the light amount suitable for reading the information recorded on the four-layer disc (for example, 1.0 mW). It is.

[4. Discrimination of the number of layers in the third embodiment]

An example of processing in the case of assuming a one-layer, two-layer, four-layer, and eight-layer optical disk 90 as the number-of-layers determination processing of the third embodiment will be described with reference to FIGS.
In addition to the above, the following processing examples can also be applied to the case where, for example, a single-layer / two-layer / three-layer optical disk 90 is assumed. In that case, in the following description, the “fourth layer” may be read as “three layers” and the “eighth layer” may be read as “six layers”, and almost the same algorithm can be applied.

A processing example of the controller 15 in this case is shown in FIG.
In this case, steps F102 to F111 in FIG. 6 are the same as those in FIGS. However, although the portion of step F101 is “F101A”, this is to set the spherical aberration correction position CT to an intermediate position between the recording layers L0 and L7 in consideration of the 8-layer disc.
In addition, “A” is added to the step number for processing different from steps F121 to F128 of FIG.

In the processing example of FIG. 6, if the count number of the S-shaped waveform is not “2” in step F110, a four-layer disc or an eight-layer disc is assumed on the assumption that there are four types of layers as described above. It will be considered.
Therefore, if the layer number determination does not end in step F106 or F111, the controller 15 proceeds from step F110 to F121A, and further performs a multiple layer number determination process.
In Step F121A, the controller 15 controls the laser driver 18 to change the reproduction laser light amount to a third light amount (for example, 1.0 mW) suitable for reading information recorded on the four-layer disc.
In step F122, the controller 15 supplies a search signal to the biaxial actuator driver 16 to move the objective lens 5 up and down.
At the time of the focus movement, the S-shaped waveform of the focus error signal FE is similarly observed, and the S-shaped waveform counter is counted by the S-shaped detection counter 14, so that the controller 15 captures the count value in step F123.

If the detection count value of the number of occurrences of the S-shaped signal is “4”, the controller 15 proceeds from step F124A to F125A, determines that the mounted optical disk 90 is a four-layer disk, and determines the number of layers. Complete the operation.
Alternatively, if the detected count value is greater than “4”, the controller 15 proceeds from step F124A → F126A → F128A, and determines that the mounted optical disk 90 is an eight-layer disk. To do.

7A, 7B, and 7C show the S-shaped waveform detected.
In both cases, the spherical aberration correction position CT is set to a substantially intermediate position between the recording layers L0 and L7 when an eight-layer disc is assumed.

FIG. 7A shows a focus error signal waveform observed when the focus is moved in step F103 in the first light quantity state.
When each of the 1-layer disc, 2-layer disc, 4-layer disc, and 8-layer disc is loaded, an S-shaped waveform is observed corresponding to each recording layer. However, since the laser output is performed with the first light amount corresponding to the single-layer disc, an S-shaped waveform having a substantially favorable amplitude level can be obtained with the single-layer disc and the double-layer disc. The amplitude of the disc is decreasing. In particular, the amplitude drop is remarkable for the 8-layer disc.
In addition, the amplitude of the recording layer far from the spherical aberration correction position CT, that is, the recording layer L0 in the case of a four-layer disc, the recording layers L0, L1, L8, L7 in the case of an eight-layer disc, etc. is considerably reduced.
Therefore, only when the count value = 1 in step F105, the determination is made in step F106 that the disc is a single-layer disc.

When it is determined that the disc is a multi-layer disc, a multi-layer number discrimination process after step F107 is performed. In this case, the reproduction laser light amount is set as a second light amount corresponding to the two-layer disc. As a result, the focus error signal waveform observed when the focus is moved in step F108 is as shown in FIG.
That is, when each of the two-layer disc, the four-layer disc, and the eight-layer disc is loaded, an S-shaped waveform is observed corresponding to each recording layer. In particular, an S-shaped waveform having a sufficient amplitude level can be obtained for discriminating between a dual-layer disc and a multilayer disc having more than that. However, with an 8-layer disc, an S-shaped waveform having a sufficient amplitude level corresponding to each recording layer is not obtained.

Accordingly, if the count value is “2” at this time, the determination result is determined to be a double-layer disc in step F111.
When the count value is greater than “2”, the number of layers determination process is further performed. First, in step F121A, the reproduction laser light amount is set to a third light amount corresponding to the four-layer disc. As a result, the focus error signal waveform observed when the focus is moved in step F122 is as shown in FIG.
That is, when each of the four-layer disc and the eight-layer disc is mounted, an S-shaped waveform having a sufficient amplitude corresponding to each recording layer is observed. Thus, when the count value is “4” or “8”, it can be accurately determined that the disc is a four-layer disc or an eight-layer disc, respectively.

  As described above, when it is determined that the disc is a multi-layer disc (here, a four-layer disc or an eight-layer disc), the layer number discriminating operation with the third reproduction light amount (in this case, the light amount corresponding to the four-layer disc) is added. Thus, when it is necessary to support a plurality of types of multi-layer discs, it is possible to determine the number of disc layers with high accuracy.

When the S-shaped detection count is performed with the third light amount as the light amount corresponding to the four-layer disc, for example, in an eight-layer disc, depending on the recording layer, the amplitude of the focus error S-shaped signal is reduced due to the influence of spherical aberration. Since it becomes large, a case where the detection count value becomes 2 or less is considered rarely.
As a countermeasure in that case, when the count value taken in step F123 becomes less than 4, the process proceeds from step F124A → F126A → F127, and in step F127, the detection threshold values th1 and th2 for S-curve detection count are lowered. The process returns to step F122. In this case, the thresholds th1 and th2 are lowered within a range in which the possibility of erroneous detection due to noise or signal fluctuation is small.
Then, again from step F122, the S-shaped detection count operation with the third light quantity is retried. This improves the accuracy of discriminating whether the disc is a 4-layer disc or an 8-layer disc.

As a modification, it is also possible to lower the detection threshold level for the S-shaped detection count when the S-shaped detection count at the third reproduction light amount is first performed.
However, the detection threshold level for the S-shaped detection count can be lowered only when the S-shaped detection count is performed with the third reproduction light quantity. Accordingly, it is possible to prevent an increase in the risk of erroneous determination of 1 layer → 2 layers, 2 layers → 4 layers when determining the number of layers with the first light amount or the second light amount.
Further, in the case where it is determined that the disc is an eight-layer disc by the third light amount corresponding to the light amount corresponding to the four-layer disc, further confirmation processing may be performed for the purpose of performing more accurate discrimination. . In other words, it is also possible as an optional operation to change the number of occurrences of the S-shaped signal according to the focus movement again after changing the light amount suitable for reading the information recorded on the 8-layer disc (for example, 1.5 mW) It is.

As can be seen from the second and third embodiments described above, in a situation where more layers and an increase in the number of layers must be taken into consideration, the discrimination processing is performed while sequentially increasing the laser light quantity. Can be considered.
For example, when there are three or more types of multilayer media (three or more optical discs) that can be used in the disk drive device 1 and it is predicted that the exact number of layers cannot be determined, the reproduction laser light amount is set to the nth light amount ( > (N-1) light quantity). Then, the n-th layer number determination may be performed until the layer number determination is completed.

In addition, from the viewpoint of preventing the deterioration of the recording layer, the reproduction laser light amount to be set is the light amount corresponding to the disc having the smallest number of layers among the possible number of layer types in the multiple layer number discrimination process to be executed. It is appropriate to set to. For example, in the case of the second embodiment, since the number of layers that can be present at the time of step F121 in FIG. 4 is three or four, the light amount is set according to the three-layer disc. In the case of the third embodiment, the number of layers that can be at the time of step F121A in FIG. 6 is four or eight, so the amount of light is set according to the four-layer disc.
In addition, when a large number of layer types are conceivable, the laser light amount may be set by applying such a concept in the multi-layer number determination process performed many times.

[5. Discrimination of the number of layers in the fourth embodiment]

A fourth embodiment will be described.
When the numerical aperture of the objective lens is large, as in the Blu-ray Disc optical system, the reproduction waveform varies greatly depending on the spherical aberration correction state. Must be done appropriately.
As a method for setting the spherical aberration correction state when determining the number of layers, as in the first to third embodiments, the optical disc 90 having the assumed number of layers is set at the beam focal position where the spherical aberration is minimized. Of these, the intermediate position in the one having the largest number of layers can be considered. That is, the number of layers is determined at all stages in a state set near the intermediate position between the recording layer closest to the disk surface (laser incident surface) and the recording layer farthest from the disk surface.

However, an example in which the spherical aberration correction position setting is changed in the course of the layer number discrimination process is also conceivable.
The processing example of the fourth embodiment is a beam that minimizes spherical aberration when performing single / multiple discrimination processing (discrimination of whether it is one layer or two or more layers) with the first light quantity. The number of layers is determined in a state where the focal position is set near the recording layer (L0) in the single-layer optical recording medium.
When performing the next multi-layer number determination process (determination of two layers, three layers, four layers or more) that is executed the required number of times after the second light quantity, the beam focus position with the smallest spherical aberration is set to the maximum number of layers. The number of layers is discriminated after changing to a position near the middle position in the case where there are many. In other words, the optical disk 90 that is supposed to be used is located near the intermediate position between the recording layer closest to the disk surface and the recording layer farthest from the disk surface in the largest number of layers.

This will be described with reference to FIGS.
FIG. 8 is obtained by adding a spherical aberration correction position setting changing process to the process of the second embodiment shown in FIG. Steps that are the same as those in FIG. 4 are given the same step numbers, and detailed descriptions thereof are omitted.
Similarly to the case of FIG. 4, the description will be made on the assumption that there are four types of optical disks 90 that may be mounted on the disk drive device 1, that is, one-layer disk, two-layer disk, three-layer disk, and four-layer disk. .

In the processing example of FIG. 8, the controller 15 first sets the spherical aberration correction position in the vicinity of the recording layer L0 in the single-layer disc in step F131. That is, the spherical aberration correction element drive driver 17 is controlled to drive the spherical aberration correction element so that the spherical aberration is minimized in the vicinity of the recording layer L0.
In step F101, the controller 15 sets the reproduction laser light amount as a first light amount suitable for a single-layer disc, and executes single / multiple determination processing as steps F103 to F106. If it is determined that the disk is a single-layer disc, the layer number determination process is terminated in step F106.

If it is determined that the disc is a multi-layer disc, the controller 15 changes the spherical aberration correction position in step F132.
That is, in this case, the assumed maximum number of layers is four, so in the four-layer disc, a substantially intermediate position between the recording layer (L3) closest to the laser incident surface and the recording layer (L0) farthest from the laser incident surface. The spherical aberration correction element driving driver 17 is instructed so that the spherical aberration is minimized. As a result, the spherical aberration correction element 8 is driven, and spherical aberration correction is performed with the substantially intermediate position as a target.
In step F107, the controller 15 sets the reproduction laser light amount to a second light amount suitable for the two-layer disc, and executes a multi-layer number determination process as steps F108 to F111. If it is discriminated as a two-layer disc, the layer number discriminating process is terminated in step F111.
If the count value is 2 or more in step F110, the multi-layer number discrimination process is further performed in step F121 and subsequent steps. The processing after step F121 is the same as that in FIG.

FIGS. 9A, 9B and 9C show the S-shaped waveform detected.
FIG. 9A shows a focus error signal waveform observed when the focus is moved in step F103 in the first light quantity state.
At this time, since the spherical aberration correction is performed in step F131 with the recording layer L0 of the single-layer disc as a target, the spherical aberration correction position CT1 is in the vicinity of the recording layer L0 as illustrated.
When each of the 1-layer disc, 2-layer disc, 3-layer disc, and 4-layer disc is loaded, an S-shaped waveform is observed corresponding to each recording layer.
In particular, since the laser output is performed with the first light amount corresponding to the single-layer disc and the spherical aberration correction setting corresponding to the single-layer disc is performed, the S-shaped waveform can be obtained very well in the case of the single-layer disc. . Even with a two-layer disc, an S-shaped waveform having a substantially satisfactory amplitude level can be obtained. In this case, due to the spherical aberration correction setting, the S-shaped waveform for the recording layer L1 has a smaller amplitude than the S-shaped waveform for the recording layer L0.
On the other hand, the amplitude is lowered in the three-layer disc and the four-layer disc. In particular, the amplitude drop is significant in the recording layers L2, L3, etc., away from the spherical aberration correction position CT1.
Therefore, only when the count value = 1 in step F105, the determination is made in step F106 that the disc is a single-layer disc.

When it is determined that the disc is a multi-layer disc, a multi-layer number discrimination process after step F107 is performed. In this case, the reproduction laser light amount is set as a second light amount corresponding to the two-layer disc. Further, in step F132, the spherical aberration correction setting is changed, and a substantially intermediate position between the recording layers L0 and L3 when a four-layer disc is assumed is set as a spherical aberration correction position CT2.
As a result, the focus error signal waveform observed when the focus is moved in step F108 is as shown in FIG.
That is, when each of the two-layer disc, the three-layer disc, and the four-layer disc is loaded, an S-shaped waveform is observed corresponding to each recording layer. In particular, an S-shaped waveform having a sufficient amplitude level can be obtained for discriminating between a dual-layer disc and a multilayer disc having more than that.

Accordingly, if the count value is “2” at this time, the determination result is determined to be a double-layer disc in step F111.
In addition, when the count value is “3” or “4”, it may be determined that the disc is a three-layer disc or a four-layer disc, respectively.

That is, in step F121, the reproduction laser light amount is set to a third light amount corresponding to the three-layer disc. As a result, the focus error signal waveform observed when the focus is moved in step F122 is as shown in FIG.
As shown in the figure, when each of the three-layer disc and the four-layer disc is mounted, an S-shaped waveform having a sufficient amplitude corresponding to each recording layer is observed. Thus, when the count value is “3” or “4”, it can be accurately determined that the disc is a three-layer disc or a four-layer disc, respectively.

  As described above, in the fourth embodiment, the single / multiple discrimination process is performed after setting the spherical aberration to be minimum in the vicinity of the recording layer L0 of the single-layer disc. Further, spherical aberration is minimized at a substantially intermediate position between the recording layer (L3) closest to the laser incident surface and the recording layer (L0) farthest from the laser incident surface within the range of the number of recording layers (for example, 4 layers). The multiple layer number discrimination process is executed with the spherical aberration correction setting. This makes it possible to determine the number of disk layers with high accuracy.

Further, since the spherical aberration correction setting is performed in accordance with the single-layer disc during the single / multiple discriminating process, it is necessary to readjust the spherical aberration correction element when the mounted optical disc 90 is a single-layer disc. Therefore, it is possible to quickly shift to a calibration operation for various parameters. For this reason, there is an advantage that the activation time can be shortened.
If it is determined that the disc is a multi-layer disc, the beam focal position where the spherical aberration is minimized is changed to the vicinity of the intermediate layer in the usable optical disc 90 having the largest number of layers. I have to. For this reason, it is possible to prevent an extreme decrease in the amplitude level of the reflected light information signal in the recording layers (the lowermost layer (L3) and the uppermost layer (L0)) at both ends, and it is possible to improve the accuracy of determining the number of layers in the case of a multilayer disc. Become.

[6. Discrimination of the number of layers in the fifth embodiment]

A fifth embodiment will be described. This is an example in which the spherical aberration correction setting is changed within the execution period of the multiple layer number discrimination process. In other words, laser light irradiation is performed by sequentially setting spherical aberration correction at a plurality of positions between the recording layer closest to the laser incident surface and the recording layer farthest from the laser incident surface within the range of the number of recording layers assumed. The reflected light information corresponding to the is detected. Then, the number of recording layers is determined from the detection result of the reflected light information for each spherical aberration correction setting state.

  FIG. 10 shows the processing of the controller 15, and FIG. 11 shows the focus error signal FE waveform in each case. As in the first embodiment of FIG. 1, it is assumed that there are three types of optical discs 90 that are assumed: a single-layer disc, a dual-layer disc, and a four-layer disc.

Steps F101 to F106 in FIG. 10 are the same as those in FIG. Single / multiple determination processing is performed in steps F101 to F106.
In step F101, as shown in FIG. 11A, the controller 15 sets the spherical aberration correction position CT3 as a substantially intermediate position assuming a four-layer disc.
In step F102, the controller 15 instructs the laser driver 18 to supply a first light amount (for example, 0.3 mW) corresponding to the single-layer disc.
In steps F103 and F104, it is determined whether the disc is a single-layer disc or a multi-layer disc. The focus error signal waveform for each disk is as shown in FIG. 11A. In the case of a single-layer disk, the determination can be made accurately.

If the disc is discriminated as a multi-layer disc in step F105, the multi-layer number discriminating process is performed in step F151 and thereafter.
In this case, first, in Step F151, the controller 15 sets the spherical aberration correction setting to the spherical aberration correction position CT4 shown in <State 1> in FIG. This is intended to minimize the spherical aberration at a substantially intermediate position between the recording layers L3 and L4 after the assumed maximum number of layers is four.
In step F152, the controller 15 instructs the laser driver 18 to supply a second light amount (for example, 0.6 mW) corresponding to the two-layer disc.

In step F153, the controller 15 supplies a search signal to the biaxial actuator driver 16 to move the objective lens 5 up and down.
At the time of the focus movement, the S-shaped waveform of the focus error signal FE is observed as shown as <State 1> in FIG. 11B, and the S-shaped waveform counter is counted by the S-shaped detection counter 14.
However, here, in the S-shaped detection counter 14, a count valid period is set.
As shown in the bottom of FIG. 11B <state 1>, the range from time t1 to t2 from the timing at which the S-shaped waveform of surface reflection is detected is defined as a count effective period TC1. This is a period obtained from the focus moving speed and the distance from the normal disk surface of the recording layers L2 and L3. The spherical aberration correction position CT4 is a position within a range passing through the count effective period TC1.
The controller 15 instructs the S-curve detection counter 14 to perform such a count valid period TC1, and causes the S-curve detection count to be executed. In step F154, the count value within the count valid period TC1 is captured.

  Subsequently, in Step F155, the controller 15 sets the spherical aberration correction setting to a spherical aberration correction position CT5 shown in <State 2> in FIG. This is intended to minimize the spherical aberration at a substantially intermediate position between the recording layers L0 and L1, with the assumed maximum number of layers being four.

In step F156, the controller 15 supplies a search signal to the biaxial actuator driver 16 to move the objective lens 5 up and down.
At the time of the focus movement, the S-shaped waveform of the focus error signal FE is observed as shown as <State 2> in FIG. 11B, and the S-shaped waveform counter is counted by the S-shaped detection counter 14.
Also in this case, the controller 15 sets the count valid period in the S-shaped detection counter 14.
As shown in the bottom of FIG. 11B <state 2>, the range from time t2 to time t3 from the timing at which the S-shaped waveform of surface reflection is detected is defined as a count effective period TC2. This is a period obtained from the focus moving speed and the distance from the normal disk surface of the recording layers L0 and L1. The spherical aberration correction position CT5 is a position within a range that passes during this count effective period.
The count valid periods TC1 and TC2 are mutually exclusive periods so that a part of the period is not covered.
The controller 15 instructs the S-curve detection counter 14 to perform such a count valid period TC2, and causes the S-curve detection count to be executed. In step F154, the count value within the count valid period TC2 is captured.

Thereafter, in step F158, the controller 15 sums the count values of the count valid periods TC1 and TC2 fetched in steps F154 and F157, and sets this as the detected S-character detection count value.
If the total count value is “2”, the process advances from step F159 to F160 to determine a two-layer disc. If the total count value is 3 or more, the process advances from step F159 to F161 to determine that the disc is a four-layer disc.

By such processing, it is possible to more accurately determine the number of layers even for a multilayer disc such as a four-layer disc.
That is, in the case of <state 1> in FIG. 11B, the spherical aberration correction position CT4 is located near the intermediate position between the two recording layers L3 and L2 on the side close to the laser incident surface (lower side) of the four-layer disc. It was. For this reason, in the four-layer disc, S-shaped waveforms with sufficient amplitude are obtained in the recording layers L2 and L3 close to the spherical aberration correction position CT4, and these detection errors are eliminated.
Further, in the case of <state 2> in FIG. 11B, the spherical aberration correction position CT5 is located near the intermediate position between the two recording layers L0 and L1 on the far side (upper side) of the laser incident surface of the four-layer disc. It was. For this reason, an S-shaped waveform with sufficient amplitude is obtained in the recording layers L0 and L1 close to the spherical aberration correction position CT5 in the two-layer disc or the four-layer disc, and these detection errors are eliminated.
Therefore, the count value corresponding to the number of layers is accurately obtained as the total count value of the count valid periods TC1 and TC2.

  In addition, it is possible to define an improvement in accuracy by determining a multi-layer disc by acquiring a plurality of reproduction waveforms (focus error S-shaped signal waveforms) in a plurality of spherical aberration correction states. That is, even if there is a decrease in the amplitude level of the reproduction waveform (focus error S-shaped signal waveform) due to the deviation from the optimum spherical aberration correction position in each recording layer, it is possible to obtain a multi-layer by complementing it using a plurality of acquired waveforms. It is possible to improve the layer number discrimination accuracy in the case of a disc.

Note that the operation of this example is also effective when the number of types of recording layers of the optical disc 90 is assumed to be larger.
For example, assuming an 8-layer disc,
State 1: Near the middle position of four recording layers (L4 to L7) close to the laser incident surface of the eight layers State 2: Four recording layers (L4 to L7) far from the laser incident surface of the eight layers It is conceivable to perform the same processing as above in the vicinity of the intermediate position.

It is also possible to increase the spherical aberration setting position to three points. In this case, for example, the following combinations may be used. For example, assuming a four-layer disc,
State 1 ′: Near the middle position of two intermediate recording layers (L2 and L1) of the four layers State 2 ′: Near the recording layer (L3 layer) closest to the laser incident surface of the four layers State 3 ': Near the recording layer (L0 layer) farthest from the laser incident surface among the four layers

In this case, it is disadvantageous that the number of waveform counting operations for the reflected light information signal (for example, the focus error signal FE) is increased from 2 times to 3 times by moving the focus. However, if the single / multiple discrimination process is performed with the same setting as in the state 1 ′, it is not necessary to change the adjustment position of the spherical aberration at the first waveform acquisition in the multi-layer number discrimination process.
In addition, the third spherical aberration adjustment position in the multiple layer number discrimination process is near the recording layer (L0 layer) farthest from the surface, and lead-in data is usually written in the recording layer L0. For this reason, when layer number discrimination can be completed at the stage of multiple layer number discrimination processing, verification of the layer number discrimination result by reading lead-in data can be performed in a short time without changing the spherical aberration position. It also has the advantage of. Further, at this stage, when it is determined that the mounted optical disk 90 is a two-layer disk, the same advantage is obtained if the surface thickness of the two-layer disk up to the recording layer L0 is the same as that of the four-layer disk. Have

If the spherical aberration is set at 3 points and an 8-layer disc is assumed,
State 1 ′: Near the middle position of the central two recording layers (L4 and L3) of the eight layers State 2 ′: Near the recording layer (L6) closest to the laser incident surface of the eight layers State 3 ': It can be considered to be in the vicinity of the layer (L1) immediately before the recording layer farthest from the laser incident surface among the eight layers.

[7. Modified example]

The present invention is not limited to the examples of the various embodiments described above, and various modifications can be considered.
For example, there are the following processing examples.
Regarding the single / multiple discriminating processing operation with the first light quantity and the multiple layer number discriminating processing operation with the second light quantity, the spherical aberration correction state is the same as in the first embodiment or the fourth embodiment. Set in the same way.
In the case where the result of the multiple layer number discrimination process with the second light quantity is a multi-layer disc having 3 to 4 layers, the multi-layer number discrimination process is performed once or multiple times by changing the light quantity. It can be considered that the spherical aberration correction position is changed as in the fifth embodiment.
Alternatively, at least the n-th multi-layer number discrimination process for final discrimination may be performed while changing the spherical aberration correction position as in the fifth embodiment.
In addition to this, various combinations of the processes of the first to fifth embodiments are assumed.

  In the embodiment, the disk drive device capable of using a multi-layer Blu-ray disc has been described as an example, but the present invention is an optical recording medium driving device and a method for determining the number of layers for various other optical recording media. Applicable. For example, the present invention can be applied to other types of multilayer optical recording media such as multilayer optical recording media other than a Blu-ray disc using a blue laser and multilayer DVD media using a red laser.

  1 disk drive device, 2 spindle motor, 3 optical pickup unit, 4 biaxial actuator, 5 objective lens, 6 laser diode, 8 spherical aberration correction element, 14 S-curve detection counter, 15 controller, 15a layer number discrimination processing unit, 16 2-axis actuator driver, 17 spherical aberration correction element drive driver, 90 optical disk

Claims (8)

An optical head unit corresponding to an optical recording medium having a single or a plurality of recording layers, and reproducing or recording information by irradiating the mounted optical recording medium with laser light;
A laser drive unit for executing laser light output from the optical head unit with the instructed laser light amount;
As a process of discriminating the number of recording layers of the mounted optical recording medium, the laser drive unit is instructed to execute the laser beam irradiation by instructing the laser driving unit the amount of light corresponding to the optical recording medium having a single recording layer. , A single / multiple discriminating process for discriminating whether the number of recording layers is single or plural from reflected light information, and if the single / multiple discriminating process determines that the number of recording layers is plural, the laser drive Multiple layer number discrimination processing for discriminating the number of recording layers from reflected light information in a state in which the laser drive unit is instructed to emit light corresponding to a multi-layer optical recording medium to the unit and laser light irradiation is performed by the optical head unit A control unit for performing
An optical recording medium driving device comprising:   2. The control unit according to claim 1, wherein the control unit instructs the laser driving unit to supply the light amount corresponding to the two-layer optical recording medium to the laser driving unit as the light amount corresponding to the multiple-layer optical recording medium. The optical recording medium driving device according to claim.   The control unit instructs the laser driving unit to determine the amount of light depending on the two-layer optical recording medium. 3. The apparatus according to claim 2, wherein the laser drive unit is instructed with a light quantity corresponding to an optical recording medium having a specific number of layers of three or more as a light quantity corresponding to the multi-layer optical recording medium, and the multi-layer number discrimination process is repeated. The optical recording medium driving device according to claim. Further comprising a spherical aberration correction setting unit for laser light,
The control unit includes the spherical aberration so that the spherical aberration is minimized at a substantially intermediate position between the recording layer closest to the laser incident surface and the recording layer farthest from the laser incident surface within the range of the number of recording layers assumed. The optical recording medium driving device according to claim 1, wherein the single / multiple discriminating process and the plural-layer number discriminating process are executed after being set in a correction setting unit. Further comprising a spherical aberration correction setting unit for laser light,
The control unit performs the single / multiple determination process after setting the spherical aberration correction setting unit so that the spherical aberration is minimized in the vicinity of the recording layer in the optical recording medium having a single recording layer, and The spherical aberration correction setting unit is set so that the spherical aberration is minimized at a substantially intermediate position between the recording layer closest to the laser incident surface and the recording layer farthest from the laser incident surface within the assumed number of recording layers. The optical recording medium driving device according to claim 1, wherein the multi-layer number discrimination process is executed. Further comprising a spherical aberration correction setting unit for laser light,
The controller controls the spherical aberration correction setting unit to record the recording layer closest to the laser incident surface and the recording layer farthest from the laser incident surface within the range of the assumed number of recording layers within the execution period of the multiple layer number discrimination process. Spherical aberration correction settings are sequentially performed for a plurality of positions between layers to detect reflected light information according to laser light irradiation, and the detection result of reflected light information for each spherical aberration correction setting state The optical recording medium driving device according to claim 1, wherein the number of recording layers is determined from the information. The control unit
In the single / multiple discriminating process and the multiple layer number discriminating process, the number of occurrences of the S-shaped signal of the focus error signal obtained as reflected light information when the objective lens of the optical head unit is moved in the focus direction is detected. The optical recording medium driving device according to claim 1, wherein the number of recording layers is determined. As a method for discriminating the number of recording layers of an optical recording medium driving device that corresponds to an optical recording medium having a single or a plurality of recording layers and reproduces or records information by irradiating the mounted optical recording medium with laser light. ,
Laser light irradiation is performed on the mounted optical recording medium with an amount of light corresponding to the optical recording medium having a single recording layer, and whether the number of recording layers is single or plural is determined from reflected light information. Single discrimination processing,
If it is determined in the single / multiple determination process that the number of recording layers is plural, the laser driving unit is irradiated with laser light with an amount of light corresponding to the multiple-layer optical recording medium, and the number of recording layers is calculated from the reflected light information. Multiple layer number discrimination processing to discriminate;
A method for determining the number of recording layers.

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