JP4215765B2 - Optical disc apparatus and tilt control method - Google Patents

Description

  The present invention relates to an optical disc apparatus and a tilt control method capable of recording or reproducing high-density information. In particular, the present invention relates to an optical disc apparatus and a tilt control method in which the tilt control technique according to the tilt state of the optical disc is improved.

  In recent years, with the increase in the density of optical disks using short-wavelength lasers, the inclination angle of the optical head (that is, the objective lens) with respect to the recording surface of the disk loaded in the disk drive is spread over the entire surface from the inner periphery to the outer periphery of the disk. Appropriate compensation is required. As a means for compensating for the tilt angle, there is tilt control. By using tilt control together with focus control and tracking (positioning) control for the optical head, recording / reproduction of a high-density optical disc is possible.

  As a conventional technique related to the tilt control, a technique for obtaining a tilt signal from a tracking error signal and performing tilt compensation is generally known. For example, Patent Document 1 discloses a technique for performing tilt detection based on a phase shift between two push-pull signals that are tracking error signals of two beams obtained by dividing a beam irradiated on an optical disk by a diffractive optical element. ing. Patent Document 2 discloses a technique for performing tilt detection based on a phase shift between two phase difference signals that are tracking error signals of two beams obtained by dividing a beam irradiated on an optical disk by a diffractive optical element. ing.

JP 2001-236666 A JP 2003-346365 A

  However, since there is a difference in intensity distribution between the main beam and the sub beam, the amplitude value of the tracking error signal of the sub beam is smaller than the amplitude value of the tracking error signal of the main beam. For this reason, when calculating the tilt signal from the tracking error signal, it is necessary to use a value obtained by multiplying the amplitude value of the tracking error signal by the sub beam by the calculation coefficient.

  This calculation coefficient differs depending on the type of optical disk and the medium of the optical disk. If the value of the calculation coefficient is not appropriate, the tracking error signal is mixed into the tilt signal, so that accurate tilt detection cannot be performed. As a result, there is a problem that optimum tilt control cannot be performed. In particular, when the sub beam is irradiated to the detrack position of the optical disc, it is difficult to set the calculation coefficient, and accurate tilt detection cannot be performed.

  The present invention has been made in view of the above, and provides an optical disc apparatus and a tilt control method capable of performing accurate tilt detection without being aware of the difference between optical discs and performing highly accurate tilt control. With the goal.

In order to solve the above-described problems and achieve the object, the present invention provides a light source for irradiating a beam to an optical disc, and a diffractive optical device that divides the beam emitted from the light source into at least a first beam and a second beam. An element, an objective lens for condensing the first beam and the second beam divided by the diffractive optical element on the optical disc, and light detection for detecting the first beam and the second beam reflected from the optical disc vessel and said first calculates a tracking error signal from the beam, Starring from said second beam, that to calculate the tilt signal producing signals of the tracking signal substantially in phase with a signal for generating the tilt signal and calculation means, the multiplication value of the predetermined calculation coefficient based on the characteristics of each of the optical disk of the tilt signal producing signals and the optical disk is calculated, the calculation coefficient A calculation coefficient adjusting means for adjusting a tilt signal calculation means for calculating a difference between the previous Quito racking the multiplication value and error signal as a tilt signal, said adjusting the tilt of the objective lens based on the tilt signal objective Driving means for performing lens tilt compensation, wherein the calculation coefficient adjustment means adjusts the calculation coefficient so that an amplitude value of the tilt signal is equal to or less than a predetermined value or a minimum value, and the tilt signal An optical disc apparatus that calculates a generation signal and the adjusted multiplication value.

Further, the present invention provides a light source that irradiates a beam to an optical disc, a diffractive optical element that divides the beam irradiated from the light source into at least a first beam and a second beam, and the diffractive optical element that is divided by the diffractive optical element. An objective lens for condensing the first beam and the second beam onto the optical disc, a photodetector for detecting the first beam and the second beam reflected from the optical disc, and a tracking error signal from the first beam. It calculates, from the second beam, and the arithmetic means that to calculate the tilt signal producing signals of the tracking signal substantially in phase with a signal for generating the tilt signal, the tilt signal producing signals and calculating a multiplication value of the calculation coefficients that are predetermined based on the characteristics of each of the optical disk of the optical disk, so that the multiplication value and the tracking error signal becomes equal A calculation coefficient adjusting means for adjusting the arithmetic coefficient, and the tilt signal calculating means for calculating a difference between the multiplied value and the tracking error signal as a tilt signal, and adjust the tilt of the objective lens based on the tilt signal An optical disc apparatus comprising: drive means for performing tilt compensation of the objective lens.
The present invention also provides a tilt control method for the optical disc apparatus.

  According to the present invention, it is possible to always appropriately determine the calculation coefficient without being aware of the difference between the optical disks. Therefore, it is possible to perform accurate tilt detection and to perform highly accurate tilt control.

  Exemplary embodiments of an optical disk device and a tilt control method according to the present invention will be explained below in detail with reference to the accompanying drawings.

(Embodiment 1)
FIG. 1 is a schematic diagram illustrating a configuration of an optical head unit of the optical disc apparatus according to the first embodiment. The optical head unit of the optical disk device according to the present embodiment includes a semiconductor laser 120, a collimator lens 122, a diffractive optical element 105, a polarizing beam splitter 103, objective lenses 102 and 104, a photodetector 106, a track, and a track. The error signal calculation circuits 107 and 109, the tilt signal calculation circuit 111, the calculation coefficient adjustment unit 110, the signal amplitude detection circuit 113, the memory 112, and the drive unit 114 are provided.

  The light beam emitted from the semiconductor laser 120 is collimated by the collimator lens 122, and is divided by the diffractive optical element into zero-order light as a main beam and ± first-order light as sub-beams. These lights are incident on the polarization beam splitter 103 as P-polarized light, and almost 100% of the light is transmitted and condensed on the optical disk 101 by the objective lens 102. In FIG. 1, only the 0th order light and the + 1st order light divided by the diffractive optical element 105 are shown.

  The reflected light of the main beam and the sub beam from the optical disk 101 is incident on the polarization beam splitter 103 as S-polarized light and is reflected by almost 100%, passes through the objective lens 104 and is received by the photodetector 106. In the present embodiment, the optical disc 101 is intended for a recording medium having a land / groove structure such as a write-once DVD-R or a rewritable DVD-RW.

  The optical disc apparatus according to the present embodiment detects tilt (tilt) of the optical disc 101 and drives the objective lens 102 to perform tilt compensation.

  The photodetector 106 converts the power of the beam into an electric signal. FIG. 2 is a schematic diagram showing the configuration of the photodetector 106 and the arrangement of the light spots. As shown in FIG. 2, the photodetector 106 includes a main beam light receiving unit 108a and a sub beam light receiving unit 108b, and each of the light receiving units 108a and 108b is divided to generate a tracking error signal. . The light spot 123a corresponds to a main beam which is 0th-order diffracted light among the transmitted light from the diffractive optical element 105, and is condensed on the boundary line of the divided light receiving unit 108a. The light spot 123b corresponds to a sub beam that is + 1st order diffracted light among the transmitted light from the diffractive optical element 105, and is condensed on the boundary line of the divided light receiving unit 108b. As can be seen from FIG. 2, the diameter of the light spot of the sub beam is smaller than the diameter of the light spot of the main beam.

  The track error signal calculation circuit 107 calculates a tracking error signal from the main beam received by the light receiving unit 108a of the photodetector 106. The track error signal calculation circuit 109 calculates a tracking error signal from the sub beam received by the light receiving unit 108b of the photodetector 106. In this embodiment, since a land / groove structure recording medium such as a write-once DVD-R or a rewritable DVD-RW is used, a push-pull method is employed as a tracking error detection method. For this reason, the tracking error signal calculation circuits 107 and 109 of this embodiment obtain a push-pull signal as the tracking error signal.

  The tilt signal calculation circuit 111 is based on a difference between a value obtained by multiplying the push-pull signal of the main beam output from the tracking error signal calculation circuit 107 and the push-pull signal of the sub beam output from the calculation coefficient adjustment unit 110 by the calculation coefficient K. The tilt signal is calculated. Specifically, the amplitude value T of the tilt signal is calculated by the following equation (1).

T = MPP-K * SPP (1)
Here, MPP is the push-pull signal amplitude value of the main beam, SPP is the push-pull signal amplitude value of the sub beam, and K is a calculation coefficient.

  In the tilt detection method targeted by the optical disk apparatus according to the present embodiment, tracking error signals obtained from a plurality of main beams and sub beams having different intensity distributions are used. Since the behavior is different, this difference is detected as a tilt signal.

  The calculation coefficient adjustment unit 110 determines the disc type of the optical disc 101 from the record information such as the lead-in area, reads the calculation coefficient (gain) K corresponding to the disc type of the optical disc 101 from the memory 112, and calculates the tracking error signal. The amplitude value of the sub-beam push-pull signal output from the circuit 109 is multiplied by a calculation coefficient K, and a tilt signal from a signal amplitude detection circuit 113 described later is input, so that the amplitude value of the tilt signal becomes zero. The value of the read calculation coefficient K is adjusted.

  FIG. 3A is an explanatory diagram illustrating the state of the amplitude of the push-pull signal of the main beam and the sub beam when the tilt is 0 °. FIG. 3B is an explanatory diagram illustrating a state of the amplitude of the push-pull signal of the main beam and the sub beam when there is a tilt (for example, + 0.5 °). As shown in FIG. 3A, there is no phase shift between the push-pull signal of the main beam and the push-pull signal of the sub beam when there is no tilt, and the zero cross points coincide. On the other hand, as shown in FIG. 3-2, when there is a tilt, the main beam push-pull signal and the sub-beam push-pull signal are shifted in phase, and the intensity distribution of each beam is different. In addition, the amount of phase shift differs for each beam, and the zero cross point becomes inconsistent due to the occurrence of tilt. In the tilt signal calculation circuit 111 of the present embodiment, this phase shift is detected by the equation (1) and used as a tilt signal.

  In this embodiment, since the tilt signal is generated from the tracking error signal, the push-pull signal of the sub beam is multiplied by a calculation coefficient (gain) K in order to remove the influence of the tracking error from the calculated tilt signal.

  In the main beam push-pull signal and the sub-beam push-pull signal shown in FIG. 4A, when the calculation coefficient K is appropriate, a tracking error occurs as shown in FIG. However, if the calculation coefficient K is not appropriate, a tracking error will be detected as a tilt signal as shown in FIG. In the calculation coefficient adjustment unit 110 of the present embodiment, the calculation coefficient K is set to an appropriate value.

  The signal amplitude detection circuit 113 receives a tilt signal from the tilt signal calculation circuit 111 and detects an amplitude value, and is, for example, a peak / bottom detection circuit.

  The drive unit 114 is a drive circuit that performs tilt compensation by inputting the tilt signal obtained by the tilt signal calculation circuit 111 and adjusting the tilt of the objective lens 102 according to the tilt signal.

  The memory 112 stores an operation coefficient correspondence table in which the disk types of the optical disk 101, that is, DVD-ROM, DVD-R, DVD-RW, and the like, and operation coefficients K that are considered to be optimal for these disk types are registered. Storage means. FIG. 5A is an explanatory diagram of an example of a calculation coefficient correspondence table. As shown in FIG. 5A, the calculation coefficient correspondence table associates each calculation coefficient with a disk type such as DVD-ROM, DVD-R, and DVD-RAM. The calculation coefficient K is read by the calculation coefficient adjustment unit 110 as described above.

  In this embodiment, the calculation coefficient adjustment unit 110 adjusts a predetermined calculation coefficient K according to the disk type of the optical disk 101. However, when the optical disk 101 is a multilayer type, each layer is adjusted. The calculation coefficient adjustment unit 110 may be configured such that the calculation coefficient K is determined in advance in the calculation coefficient correspondence table, and the calculation coefficient K corresponding to the layer to be written or read is read and adjusted. FIG. 5B is an explanatory diagram of an example of a calculation coefficient correspondence table in which a calculation coefficient K is determined for each layer. In the example shown in FIG. 5B, the calculation coefficient K for the optical disc 101 for each type of single-layer disc is determined for each layer of the optical disc 101 for each disc type of two-layer type.

  Further, a calculation coefficient K is determined in advance in the calculation coefficient correspondence table for each disk type for each manufacturer, which is the manufacturer of the optical disk 101, and the manufacturer of the optical disk 101 is read from the record information such as the lead-in area to obtain the disk type of the manufacturer. The calculation coefficient adjustment unit 110 may be configured to read out and adjust the corresponding calculation coefficient K. FIG. 5C is an explanatory diagram of an example of a calculation coefficient correspondence table in which a calculation coefficient K is determined for each manufacturer. In the example shown in FIG. 5C, the calculation coefficient K in the optical disc 101 for each disc type for each manufacturer is determined.

  Further, the calculation coefficient K is determined in advance in the calculation coefficient correspondence table for each identification information of the optical disc 101, and the identification information of the optical disc 101 is read from the record information such as the lead-in area, and the calculation coefficient K corresponding to the identification information is determined. The calculation coefficient adjustment unit 110 may be configured to read and adjust. FIG. 5-4 is an explanatory diagram illustrating an example of a calculation coefficient correspondence table in which a calculation coefficient K is determined for each piece of identification information of the optical disc 101.

  Next, the tilt control process by the optical disc apparatus according to the present embodiment configured as described above will be described. FIG. 6 is a flowchart of a tilt control process according to the first embodiment.

  First, focus servo control is performed on the optical disc 101 (step S601). After the focus servo control is completed, the tracking error signal calculation circuit 107 pushes the main beam from the main beam received by the photodetector 106. The pull signal is calculated, and the sub-beam push-pull signal is calculated by the tracking error signal calculation circuit 109 from the sub-beam received by the photodetector 106, and the inclination of the objective lens 102 is set to the maximum amplitude value of the push-pull signal. (Step S602). In this process, since the average disc tilt with respect to the objective lens 102 at the radial position is considered to be zero at the point where the amplitude value of the push-pull signal is maximized, the calculation coefficient K is accurately calculated from the position of the tilt. Zero point adjustment is performed as a zero point for setting.

  Note that the zero point adjustment is not limited to using a push-pull signal, and any signal may be used to perform zero point adjustment as long as there is a correlation with the disc tilt. Also good. For example, if data is recorded on an optical disc, the amplitude of the reproduction signal of the data can be used for zero point adjustment as well. Also, in the case of an optical disc in which pit data is recorded in advance by tracking with a phase difference signal, such as a DVD-ROM, adjustment based on the amplitude of the reproduction signal may be preferable.

  Next, the calculation coefficient adjustment unit 110 reads the disc type of the optical disc 101 from the lead-in area or the like (step S603). Then, the calculation coefficient adjustment unit 110 retrieves the calculation coefficient K corresponding to the read disk type from the calculation coefficient correspondence table stored in the memory 112 (step S604).

  Next, the tilt signal is calculated using equation (1) (step S605). Specifically, the calculation coefficient adjustment unit 110 multiplies the amplitude value of the push-pull signal of the sub beam by the acquired calculation coefficient K, and the tilt signal calculation unit 111 calculates the push-pull of the sub beam from the push-pull signal amplitude value of the main beam. A difference between values obtained by multiplying the signal amplitude value by the operation coefficient K is taken as a tilt signal.

  Then, the amplitude value of the tilt signal is detected by the signal amplitude detection circuit 113 and input to the calculation coefficient adjustment unit 110, and the calculation coefficient adjustment unit 110 determines whether or not the tilt signal amplitude value is minimum ( Step S606). Specifically, by holding the previous tilt signal amplitude value and repeatedly comparing the previous tilt signal amplitude value output from the signal amplitude detection circuit 113 with the previous tilt signal amplitude value. Then, it is determined whether or not it is the minimum tilt signal amplitude value.

  If the tilt signal amplitude value is not minimum (step S606: No), the calculation coefficient K is changed by the calculation coefficient adjustment unit 110 (step S607), and the tilt signal calculation in step S605 and the calculation coefficient K in step S607 are changed. The change is repeatedly executed until the calculation coefficient K is minimized.

  It may be configured so that the tilt signal amplitude value is not repeated until the tilt signal amplitude value becomes the minimum, but is repeated until the tilt signal amplitude value becomes a predetermined value or less. In this case, the fixed value that is the determination criterion needs to be appropriately determined from the quality of the optical disc 101, the performance of the optical disc apparatus, and the like. For example, when the optical disk 101 is greatly undulated and there is a large disk tilt, the constant value needs to be set larger.

  On the other hand, if the tilt signal amplitude value is minimized in step S606 (step S606: Yes), the modified computation coefficient K when the tilt signal amplitude value is minimized is used as the computation coefficient correspondence table in the memory 112. Is stored as a calculation coefficient K corresponding to the disk type (step S608).

  Then, tracking servo control is started (step S609), and the objective lens 102 is driven by the drive unit 114 based on the tilt signal to start tilt servo control (step S610).

  As described above, in the optical disc apparatus according to the first embodiment, the difference value between the value obtained by multiplying the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub-beam by the operation coefficient K is equal to or smaller than a predetermined value. After adjusting the value of the calculation coefficient K, the tilt signal is calculated using the adjusted calculation coefficient K and tilt compensation is performed. Therefore, accurate tilt detection can be performed without being aware of the difference in the optical disc, and high-precision tilt. Control can be performed.

(Embodiment 2)
In the optical disc apparatus according to the first embodiment, the calculation coefficient K is set such that a difference value between a value obtained by multiplying the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub beam by the calculation coefficient K is equal to or less than a predetermined value. However, in the optical disc apparatus according to the second embodiment, the value obtained by multiplying the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub beam by the operation coefficient K is equal. Thus, tilt compensation is performed by adjusting the calculation coefficient K.

  FIG. 7 is a schematic diagram illustrating a configuration of an optical head unit of the optical disc device according to the second embodiment. The optical head unit of the optical disc apparatus according to the present embodiment includes a semiconductor laser 120, a collimator lens 122, a diffractive optical element 105, a polarization beam splitter 103, objective lenses 102 and 104, a photodetector 106, and a track error. The signal calculation circuits 107 and 109, the tilt signal calculation circuit 111, the calculation coefficient adjustment unit 710, the signal amplitude detection / comparison circuit 713, the drive unit 114, and the memory 112 are provided.

  Here, the semiconductor laser 120, the collimator lens 122, the diffractive optical element 105, the polarization beam splitter 103, the objective lenses 102 and 104, the photodetector 106, the track error signal calculation circuits 107 and 109, and the tilt signal calculation circuit 111 are implemented. It has the same configuration and function as those of the optical disk device of mode 1. The memory 112 stores a calculation coefficient correspondence table similar to that in the first embodiment.

  In the present embodiment, calculation coefficient adjustment section 710 adjusts calculation coefficient K so that the value obtained by multiplying the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub beam by calculation coefficient K is equal. This is different from the calculation coefficient adjustment unit 110 of the first embodiment.

  Further, the signal amplitude detection / comparison circuit 713 inputs a value obtained by multiplying the push-pull signal of the main beam and the push-pull signal of the main beam by the calculation coefficient K before the calculation of the tilt signal by the tilt signal calculation unit 111, and A beam push-pull signal amplitude value (first term in equation (1)) and a sub-beam push-pull signal amplitude value multiplied by a calculation coefficient K (second term in equation (1)) are detected, and both are detected. The comparison result is output to the calculation coefficient adjustment unit 710.

  Next, the tilt control process by the optical disc apparatus according to the present embodiment configured as described above will be described. FIG. 8 is a flowchart of a tilt control process according to the second embodiment.

  The processing from the focus servo control processing to the acquisition of the calculation coefficient K from the memory 112 (steps S801 to S804) is the same as the processing from steps S601 to S604 in the first embodiment.

  Next, the push-pull signal amplitude value of the main beam is acquired by the signal amplitude detection / comparison circuit 713, and the push-pull signal amplitude value of the sub beam is acquired by the calculation coefficient adjustment unit 710 (step S805). Then, the calculation coefficient adjustment unit 710 multiplies the calculation coefficient K acquired from the memory 112 in step S804 by the push-pull signal amplitude value of the sub beam, and the signal amplitude detection / comparison circuit 713 determines the push-pull signal amplitude value of the main beam and its amplitude. It is determined whether or not the multiplication values are equal (step S806). If the multiplication value of the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub-beam is not equal (step S806: No), the calculation coefficient adjustment unit 110 changes the calculation coefficient K (step S807). The calculation coefficient K is repeatedly changed until they become equal.

  When the multiplication value of the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub beam becomes equal in step S806 (step S806: Yes), the changed calculation coefficient K is stored in the calculation coefficient correspondence table of the memory 112. Is stored as a calculation coefficient K corresponding to the disk type (step S808).

  Then, tracking servo control is started (step S809), and the tilt lens control is started by driving the objective lens 102 by the drive unit 114 based on the tilt signal obtained by calculating the tilt signal calculation circuit 111 according to the equation (1). (Step S810).

  As described above, in the optical disc apparatus according to the second embodiment, the tilt is obtained by adjusting the calculation coefficient K so that the value obtained by multiplying the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub beam by the calculation coefficient K is equal. Since compensation is performed, accurate tilt detection can be performed without being aware of the difference between optical disks, and highly accurate tilt control can be performed.

  In the optical disk apparatus of the present embodiment, the calculation coefficient K for each disk type for each layer in the multilayer optical disk shown in FIG. 5-2, the calculation coefficient K for each disk type for each manufacturer shown in FIG. A calculation coefficient K for each piece of optical disc identification information shown in FIG. 5-4 may be stored in the memory 112 as a calculation coefficient correspondence table, and the calculation coefficient K may be acquired according to the optical disk 101. Good.

(Embodiment 3)
In the optical disk apparatus according to the first and second embodiments, the calculation coefficient K for each disk type is stored in the memory 112 in advance, and the calculation coefficient K is read according to the disk type of the optical disk to be used. However, in the optical disk apparatus according to the third embodiment, the calculation coefficient K corresponding to the optical disk is held in the innermost circumferential lead-in area of the optical disk, and the calculation coefficient K read from the optical disk is adjusted. Is.

  The configuration of the optical head unit of the optical disk apparatus according to the present embodiment is the same as that of the first embodiment shown in FIG. However, in the present embodiment, the optimum calculation coefficient K for the own optical disc is recorded in advance in the lead-in area of the optical disc so as to be rewritable. In the optical disk apparatus according to the present embodiment, the calculation coefficient adjustment unit 110 reads the calculation coefficient K from the lead-in area of the optical disk instead of the memory 112. Further, in the optical disc apparatus of the present embodiment, the adjusted calculation coefficient K is overwritten on the lead-in area of the optical disc 101.

  Next, the tilt control process by the optical disc apparatus according to the present embodiment configured as described above will be described. FIG. 9 is a flowchart of a tilt control process according to the third embodiment.

  The focus servo control process (step S901) and the tilt setting process (step S902) of the objective lens 102 are performed in the same manner as the processes in steps S601 and S602 in the first embodiment.

  Next, the calculation coefficient K recorded in the lead-in area of the optical disc 101 is read by the calculation coefficient adjustment unit 110 and temporarily stored in the memory 112 (step S903). Then, using the calculation coefficient K temporarily stored in the memory 112, the tilt signal is calculated by the equation (1) as in the first embodiment (step S904), and the signal amplitude detection circuit 113 calculates the tilt signal. The amplitude value is detected and input to the calculation coefficient adjustment unit 110, and the calculation coefficient adjustment unit 110 determines whether or not the tilt signal amplitude value is minimum (step S905). If the tilt signal amplitude value is not minimum (step S905: No), the calculation coefficient K temporarily stored in the memory 112 by the calculation coefficient adjustment unit 110 is changed (step S906), and the tilt signal in step S904 is changed. The calculation and the change of the calculation coefficient K in step S906 are repeatedly executed until the calculation coefficient K is minimized. As in the first embodiment, the configuration may be such that the tilt signal amplitude value does not repeat until the tilt signal amplitude value becomes the minimum, but is repeated until the tilt signal amplitude value becomes a predetermined value or less.

  On the other hand, if the tilt signal amplitude value is minimized in step S905 (step S905: Yes), the changed calculation coefficient K when the tilt signal amplitude value is minimized is stored in the lead-in area of the optical disc 101. Writing is performed (step S907).

  Then, tracking servo control is started (step S908), and the objective lens 102 is driven by the drive unit 114 based on the tilt signal to start tilt servo control (step S909).

  As described above, in the optical disc apparatus according to the third embodiment, the difference value between the value obtained by multiplying the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub-beam by the operation coefficient K is equal to or smaller than a predetermined value. After adjusting the value of the calculation coefficient K, the tilt signal is calculated using the adjusted calculation coefficient K and tilt compensation is performed. Therefore, accurate tilt detection can be performed without being aware of the difference in the optical disc, and high-precision tilt. Control can be performed.

  In the optical disk apparatus according to the third embodiment, the calculation coefficient K corresponding to the optical disk is held in the lead-in area of the optical disk, and the calculation coefficient K read from the optical disk 101 is adjusted. Is not required to be stored in the memory 112 for each disc type, each discriminating information, etc., and there is no need to search the memory for the calculation coefficient K corresponding to the optical disc, and tilt control can be performed with higher accuracy and speed. Can do.

  In the optical disk apparatus of the present embodiment, the calculation coefficient K corresponding to each layer is recorded in each layer of the multilayer optical disk, and the calculation coefficient corresponding to the layer from the layer to be written or read in step S903. The calculation coefficient adjustment unit 110 may be configured to read K and adjust the calculation coefficient K for each read layer. In this case, the adjusted calculation coefficient K can be further recorded in the layer to be written or read from the optical disk.

  Further, in the optical disk apparatus according to the present embodiment, when adjusting the calculation coefficient K read from the optical disk, the calculation is performed on the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub beam as in the first embodiment. Tilt compensation is performed by adjusting the calculation coefficient K so that the difference value of the value multiplied by the coefficient K is equal to or less than the predetermined value, but the push-pull signal amplitude value of the main beam is the same as in the second embodiment. The calculation coefficient K read from the optical disc may be adjusted so that the value obtained by multiplying the push-pull signal amplitude value of the sub beam by the calculation coefficient K becomes equal.

(Embodiment 4)
In the optical disk device according to the third embodiment, the calculation coefficient K corresponding to the optical disk is held in the innermost circumferential lead-in area of the optical disk, and the calculation coefficient K read from the optical disk is adjusted. In the optical disk device according to the fourth embodiment, the memory 112 stores the calculation coefficient K for each disk type in advance, and stores the calculation coefficient K corresponding to the optical disk in the lead-in area of the optical disk. When the calculation coefficient K is not recorded, the calculation coefficient K corresponding to the optical disk is read from the memory 112 and adjusted.

  The configuration of the optical head unit of the optical disk apparatus according to the present embodiment is the same as that of the first embodiment shown in FIG. However, in the present embodiment, the optimum calculation coefficient K for the own optical disc is recorded in advance in the lead-in area of the optical disc so as to be rewritable. Further, in the optical disc apparatus according to the present embodiment, the operation coefficient K corresponding to the disc type is stored in the memory 112 as an operation coefficient correspondence table. In the optical disc apparatus according to the present embodiment, the calculation coefficient adjustment unit 110 first reads the calculation coefficient K from the lead-in area of the optical disc, and when it is recorded, the calculation coefficient K recorded in the lead-in area. If the calculation coefficient K is not recorded in the lead-in area of the optical disc, the calculation coefficient K corresponding to the disc type is read out from the calculation coefficient correspondence table in the memory 112 and adjusted. Further, in the optical disc apparatus of the present embodiment, the adjusted calculation coefficient K is overwritten on the lead-in area of the optical disc 101 and the memory 112.

  Next, the tilt control process by the optical disc apparatus according to the present embodiment configured as described above will be described. FIG. 10 is a flowchart of a tilt control process according to the fourth embodiment.

  The focus servo control process (step S1001) and the tilt setting process of the objective lens 102 (step S1002) are performed in the same manner as the processes of steps S601 and S602 in the first embodiment.

  Next, the calculation coefficient adjustment unit 110 reads out the calculation coefficient K recorded in the lead-in area of the optical disc 101 (step S1003). At this time, it is determined whether or not a calculation error K has been recorded in the lead-in area and a read error has occurred (step S1004).

  When the calculation coefficient K is not recorded in the lead-in area (step S1004: Yes), the disk type of the optical disk 101 is read from the lead-in area or the like by the calculation coefficient adjustment unit 110 (step S1005). Then, the calculation coefficient adjustment unit 110 retrieves the calculation coefficient K corresponding to the read disk type from the calculation coefficient correspondence table stored in the memory 112 (step S1006). Then, the calculation coefficient K acquired from the memory 112 is adjusted in the subsequent processing.

  On the other hand, when the calculation coefficient K is recorded in the lead-in area in step S1004 (step S1004: No), the processing of steps S1005 and S1006 is not performed and the calculation coefficient K read from the lead-in area of the optical disc 101 is performed. Will be adjusted in subsequent processing.

  Next, using the calculation coefficient K read from the lead-in area or the calculation coefficient K acquired from the memory 112, the tilt signal is calculated by the expression (1) as in the first embodiment (step S1007). The amplitude value of the tilt signal is detected by the amplitude detection circuit 113 and is input to the calculation coefficient adjustment unit 110, and the calculation coefficient adjustment unit 110 determines whether or not the tilt signal amplitude value is minimum (step S1008). If the tilt signal amplitude value is not the minimum (step S1008: No), the calculation coefficient adjustment unit 110 changes the calculation coefficient K (step S1009), and the tilt signal calculation in step S1007 and the calculation coefficient K in step S1009 are changed. The change is repeatedly executed until the calculation coefficient K is minimized. Note that, similarly to the first embodiment, it may be configured such that the tilt signal amplitude value is not repeated until the tilt signal amplitude value becomes the minimum, but is repeated until the tilt signal amplitude value becomes a predetermined value or less.

  On the other hand, if the tilt signal amplitude value is minimized in step S1008 (step S1008: Yes), the changed calculation coefficient K when the tilt signal amplitude value is minimized is stored in the lead-in area of the optical disc 101. Write (step S1010). Next, the changed calculation coefficient K is stored as the calculation coefficient K corresponding to the disk type in the calculation coefficient correspondence table of the memory 112 (step S1011).

  Then, tracking servo control is started (step S1012), and the objective lens 102 is driven by the drive unit 114 based on the tilt signal to start tilt servo control (step S1013).

  As described above, in the optical disc apparatus according to the fourth embodiment, the difference value between the value obtained by multiplying the push-pull signal amplitude value of the main beam and the push-pull signal amplitude value of the sub-beam by the operation coefficient K is equal to or smaller than a predetermined value. After adjusting the value of the calculation coefficient K, the tilt signal is calculated using the adjusted calculation coefficient K and tilt compensation is performed. Therefore, accurate tilt detection can be performed without being aware of the difference in the optical disc, and high-precision tilt. Control can be performed.

  In the optical disc apparatus according to the fourth embodiment, the calculation coefficient K for each disc type is held in the memory 112 in advance, and the calculation coefficient K corresponding to the optical disc is held in the lead-in area of the optical disc. When the calculation coefficient K is not recorded in the lead-in area, the calculation coefficient K corresponding to the optical disk is read out from the memory 112 and adjusted. Therefore, regardless of whether or not the calculation coefficient K is recorded on the optical disk, Tilt control can be performed with high accuracy.

  In the optical disk apparatus of the present embodiment, the calculation coefficient K for each disk type for each layer in the multilayer optical disk shown in FIG. 5-2, the calculation coefficient K for each disk type for each manufacturer shown in FIG. A calculation coefficient K for each piece of identification information of the optical disk shown in FIG. 5-4 is stored in the memory 112 as a calculation coefficient correspondence table. When the calculation coefficient K is not recorded in the lead-in area of the optical disk, The calculation coefficient K may be acquired.

  Further, the optical disc apparatus according to the present embodiment is configured to first determine whether or not the calculation coefficient K is recorded on the optical disc 101 and to read the calculation coefficient K from the memory 112 when it is not recorded. However, the calculation coefficient K may be read from the memory 112 first, and when the calculation coefficient K is not held in the memory 112, the calculation coefficient K recorded on the optical disc 101 may be read. .

  Further, in the optical disc apparatus of the present embodiment, when adjusting the calculation coefficient K read from the optical disc or the memory 112, the push-pull signal amplitude value of the main beam and the push-pull signal amplitude of the sub beam are adjusted as in the first embodiment. Tilt compensation is performed by adjusting the calculation coefficient K so that the difference value of the value obtained by multiplying the value by the calculation coefficient K is minimized. As in the second embodiment, the push-pull signal amplitude value of the main beam is The calculation coefficient K read from the optical disc or the memory 112 may be adjusted so that the value obtained by multiplying the push-pull signal amplitude value of the sub beam by the calculation coefficient K becomes equal.

  In the optical disc apparatus according to the first to fourth embodiments, the tilt signal is calculated from the push-pull signal. However, the optical disc 101 has a structure having a recording pit like a read-only disc such as a DVD-ROM. In this case, a phase difference (DPD: Differential Phase Detection) signal can be used as the tracking error signal, and the adjustment of the tilt signal and the calculation coefficient K from the phase difference signal is applied in the same manner as in the first to fourth embodiments. can do.

  In the optical disc apparatuses according to the first to fourth embodiments, the zero point adjustment process is performed by setting the inclination of the objective lens 102 to the inclination that maximizes the push-pull signal amplitude value (steps S602, S802, S902, S1002), and such processing may be omitted.

2 is a schematic diagram showing a configuration of an optical head unit of the optical disc apparatus according to Embodiment 1. FIG. It is a schematic diagram which shows the structure of the photodetector 106, and arrangement | positioning of a light spot. It is explanatory drawing which shows the state of the amplitude of the push pull signal of a main beam and a sub beam in case a tilt is 0 degree. It is explanatory drawing which shows the state of the amplitude of the push pull signal of a main beam and a sub beam in case there exists a tilt (for example, +0.5 degree). It is explanatory drawing which shows the push pull signal of a main beam, and the push pull signal of a sub beam. It is explanatory drawing which shows the state of the tilt signal when a calculation coefficient is appropriate. It is explanatory drawing which shows the state of the tilt signal when a calculation coefficient is not appropriate. It is explanatory drawing which shows an example of a calculation coefficient corresponding | compatible table. It is explanatory drawing which shows an example of the calculation coefficient corresponding | compatible table which defined the calculation coefficient K for every layer. It is explanatory drawing which shows an example of the calculation coefficient corresponding | compatible table which defined the calculation coefficient K for every manufacturer of the manufacturer. 6 is an explanatory diagram showing an example of a calculation coefficient correspondence table in which a calculation coefficient K is defined for each piece of identification information of the optical disc 101. 4 is a flowchart illustrating a procedure of tilt control processing according to the first embodiment; FIG. 6 is a schematic diagram illustrating a configuration of an optical head unit of an optical disc device according to a second embodiment. 10 is a flowchart illustrating a procedure of tilt control processing according to the second embodiment; 10 is a flowchart illustrating a procedure of tilt control processing according to the third embodiment; 10 is a flowchart illustrating a procedure of tilt control processing according to the fourth embodiment;

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Optical disk 102,104 Objective lens 103 Polarization beam splitter 105 Diffractive optical element 106 Photo detector 107,109 Track error signal calculation circuit 108a Main beam light reception part 108b Sub beam light reception part 110,710 Calculation coefficient adjustment part 111 Tilt signal calculation circuit 113 signal amplitude detection circuit 112 memory 114 drive unit 120 semiconductor laser 122 collimator lens 123a, 123b light spot 713 signal amplitude detection / comparison circuit

Claims (11)

A light source for irradiating the optical disc with a beam;
A diffractive optical element that divides the beam emitted from a light source into at least a first beam and a second beam;
An objective lens for condensing the first beam and the second beam divided by the diffractive optical element on the optical disc;
A photodetector for detecting a first beam and a second beam reflected from the optical disc;
Calculating a tracking error signal from said first beam from said second beam, and the arithmetic means that to calculate the tilt signal producing signals of the tracking signal substantially in phase with a signal for generating the tilt signal ,
Calculation coefficient adjustment means for calculating a multiplication value of a predetermined calculation coefficient based on the tilt signal generation signal and the characteristics of the optical disk for each of the optical disks, and adjusting the calculation coefficient;
A tilt signal calculation means for calculating a difference between the previous Quito racking the multiplication value and error signal as a tilt signal,
Drive means for adjusting the tilt of the objective lens based on the tilt signal and performing tilt compensation of the objective lens,
The calculation coefficient adjustment unit adjusts the calculation coefficient so that an amplitude value of the tilt signal is a value equal to or smaller than a predetermined value or a minimum value, and calculates the tilt signal generation signal and the adjusted multiplication value. An optical disc device characterized by the above. A light source for irradiating the optical disc with a beam;
A diffractive optical element that divides the beam emitted from a light source into at least a first beam and a second beam;
An objective lens for condensing the first beam and the second beam divided by the diffractive optical element on the optical disc;
A photodetector for detecting a first beam and a second beam reflected from the optical disc;
Calculating a tracking error signal from said first beam from said second beam, and the arithmetic means that to calculate the tilt signal producing signals of the tracking signal substantially in phase with a signal for generating the tilt signal ,
On the basis of the tilt signal producing signals and the characteristics of each of the optical disk of the optical disk by calculating a multiplication value of the predetermined operation coefficients, the calculation coefficient as the multiplication value and the tracking error signal becomes equal Arithmetic coefficient adjusting means for adjusting
A tilt signal calculating means for calculating a difference between the multiplied value and the tracking error signal as a tilt signal,
Driving means for adjusting the tilt of the objective lens based on the tilt signal and performing tilt compensation of the objective lens;
An optical disc apparatus comprising: Storage means for storing the type of the optical disc and the calculation coefficient in association with each other;
The calculation coefficient adjusting means determines the type of the optical disc, reads the calculation coefficient corresponding to the determined type from the storage means, calculates the multiplication value, and sets the adjusted calculation coefficient to the storage means. The optical disk apparatus according to claim 1, wherein the calculation coefficient corresponding to the type of the optical disk is stored. The storage means further stores a manufacturer of the optical disc and the calculation coefficient in association with each other,
The calculation coefficient adjustment unit determines a manufacturer of the optical disc, reads the calculation coefficient corresponding to the determined manufacturer from the storage unit, calculates the multiplication value, and sets the calculated calculation coefficient to the storage unit. 4. The optical disk device according to claim 3, wherein the optical disk apparatus stores the calculation coefficient corresponding to a type of the manufacturer of the optical disk. Storage means for storing the identification information unique to the optical disc and the calculation coefficient in association with each other;
The calculation coefficient adjustment unit determines identification information of the optical disc, reads the calculation coefficient corresponding to the determined identification information from the storage unit, calculates the multiplication value, and calculates the calculated calculation coefficient, The optical disk apparatus according to claim 1 or 2, wherein the storage means stores the calculation coefficient corresponding to the identification information of the optical disk. The storage means further stores each layer of the optical disc composed of a plurality of layers in association with the calculation coefficient,
The calculation coefficient adjustment unit determines a layer to be written to or read from the optical disc, reads the calculation coefficient corresponding to the determined layer from the storage unit, calculates the tilt signal, and performs the calculation after adjustment. 6. The optical disk apparatus according to claim 3, wherein a coefficient is stored in the storage unit as the calculation coefficient corresponding to the layer of the optical disk.   The calculation coefficient adjustment means reads the calculation coefficient from the optical disk on which the calculation coefficient is recorded, calculates the multiplication value, and records the adjusted calculation coefficient on the optical disk. 3. An optical disc apparatus according to 1 or 2.   The calculation coefficient adjusting means reads the calculation coefficient for a layer to be written to or read from the optical disc having a plurality of layers in which the calculation coefficient is recorded for each layer, calculates the multiplication value, and the adjusted value 8. The optical disc apparatus according to claim 7, wherein a calculation coefficient is recorded on the optical disc as the calculation coefficient for the layer to be written or read. And further comprising storage means for storing the calculation coefficient,
The tilt signal calculation means reads the calculation coefficient from the optical disc when the calculation coefficient is recorded on the optical disc, and from the storage means when the calculation coefficient is not recorded on the optical disc. 3. The optical disc apparatus according to claim 1, wherein the calculation coefficient is read to calculate the multiplication value, and the adjusted calculation coefficient is recorded in the optical disc and the storage unit. Light for detecting the first beam and the second beam reflected from the optical disk by condensing the first beam and the second beam obtained by splitting the beam emitted from the light source by the diffractive optical element onto the optical disk by the objective lens. A detection process;
Calculating a tracking error signal from said first beam from said second beam, and computing means that to calculate the tracking signal and the tilt signal producing signals having substantially the same phase a signal for generating the tilt signal,
A calculation coefficient adjustment step of calculating a multiplication value of a predetermined calculation coefficient based on the tilt signal generation signal and the characteristics of the optical disk for each of the optical disks, and adjusting the calculation coefficient;
A tilt signal calculating step for calculating a difference between the multiplied value to the previous Quito racking error signal as a tilt signal,
A drive step of adjusting the tilt of the objective lens based on the tilt signal and performing tilt compensation of the objective lens,
The calculation coefficient adjustment step adjusts the calculation coefficient so that an amplitude value of the tilt signal is equal to or less than a predetermined value or a minimum value, and calculates the tilt signal generation signal and the adjusted multiplication value. And a tilt control method. Light for detecting the first beam and the second beam reflected from the optical disk by condensing the first beam and the second beam obtained by splitting the beam emitted from the light source by the diffractive optical element onto the optical disk by the objective lens. A detection process;
Calculating a tracking error signal from said first beam from said second beam, and the calculation step you calculate the tracking signal and the tilt signal producing signals having substantially the same phase a signal for generating the tilt signal,
On the basis of the tilt signal producing signals and the characteristics of each of the optical disk of the optical disk by calculating a multiplication value of the predetermined operation coefficients, the calculation coefficient as the multiplication value and the tracking error signal becomes equal A calculation coefficient adjustment process for adjusting
A tilt signal calculating step for calculating a difference between the multiplied value and the tracking error signal as a tilt signal,
A driving step of adjusting the tilt of the objective lens based on the tilt signal and performing tilt compensation of the objective lens;
Including a tilt control method.

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