JP2012208985A - Optical disk drive, and focus pull-in or focus jump method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent anxiety of such a case that a focusing is erroneously made to a different recording layer in an identification method based on a focus error signal, when a thickness of a cover layer between the recording layers is changed by an increase of the number of recording layers.SOLUTION: A discrimination is executed from a correction amount corresponding to the recording layer whether the recording layer is an objective recording layer, by means of changing a correction amount of an aberration correction element, when position control is performed for positioning a focal point to an arbitrary optical recording layer.

Description

  The present invention relates to an optical disc apparatus that performs data recording or reproduction on an optical disc having a plurality of recording layers.

  Patent Document 1 states that “in this way, in the multilayer optical recording medium of the present invention, the first region having the first reflectance is recorded in the recording layer identification area of some recording layers, and the recording of other recording layers is performed. A second region having a second reflectance is formed in the layer identification area so that at least a portion of the first region and at least a portion of the second region overlap with each other along the recording layer stacking direction. For this reason, if the pickup is set at a position where the first and second regions overlap and a focus jump is performed, the intensity of the reflected light from the detected recording layer differs depending on the reflectance. Can be used as an identification mark for the recording layer. "

  Further, Patent Document 2 describes that “the amplitude of a tracking error (TE) signal, which is an index of track followability, is recorded before a focus jump, and the amplitude of the TE signal after the jump relative to the amplitude of the TE signal before the jump is recorded. When the ratio is equal to or less than a predetermined threshold value, the jump is retried, and when the spherical aberration correction value is changed stepwise after the jump, when the maximum value cannot be detected in the amplitude change of the TE signal, "Retry the jump."

JP2007-26479 JP2009-230781A

  In conventional DVD dual-layer discs and the like, when performing laser control with a laser focus on an arbitrary recording layer, a method is used in which the number of recording layers is counted by a focus error signal obtained from reflected light and the arbitrary recording layer is identified. Has been.

  Currently, a standardized Blu-ray disc (hereinafter referred to as BD) has a plurality of recording layers in the vicinity of 0.1 mm from the surface of the optical disc, and allows access to the plurality of recording layers from one side. The plurality of recording layers are arranged with a cover layer having a thickness on the order of micrometers in the thickness direction of the disc.

  If the number of recording layers increases and the cover layer thickness between recording layers changes, there is a concern that the identification method using the focus error signal may inadvertently focus on different recording layers. In the case where the recording layer is erroneously pulled in, conventionally, there is only an identification method such as reading an address on the optical disk, and further processing time is required to determine a recording layer error.

  In order to solve such a problem, Japanese Patent Application Laid-Open No. H10-228688 discloses a configuration that solves the problem by providing each recording layer with a recording layer identification area for identifying the recording layer separately from the data area as a region having a different reflectance. Proposed.

  However, as disclosed in Patent Document 1, there is a concern that the manufacturing process of the optical disk becomes complicated by the method of determining the recording layer by providing a special area in the structure of the optical disk. In addition, compatibility with conventional disks also decreases.

  The technique described in Patent Document 2 takes into consideration which direction (the surface side of the optical disc or the opposite side) the desired (target) recording layer is relative to the recording layer in which the focal point is erroneously positioned. Absent. Therefore, when an optical disc having three or more layers is applied to a technique such as Patent Document 2, the recording layer in which the focal point is erroneously positioned is not determined to be one, and which recording layer is the recording layer in which the focal point is erroneously positioned. Therefore, even if it is attempted to retry the focus jump, there is a possibility that the focus cannot be positioned on the desired recording layer.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an optical disc apparatus capable of quickly executing focus pull-in or focus jump on a desired recording layer.

  The above-mentioned problem is solved by adopting, for example, the configuration described in the claims.

  According to the present invention, it is possible to provide an optical disc apparatus capable of quickly performing focus pull-in or focus jump on a desired recording layer.

The figure which shows the structural example of an optical disk device Diagram showing spherical aberration correction and recording layer position of optical disc The figure which shows the relationship between the spherical aberration correction amount of a tracking error signal, and a focal point position The figure which shows the relationship between the spherical aberration correction amount of a tracking error signal, and a focal point position The flowchart which shows the process of one implementation of this invention The flowchart which shows the process of one implementation of this invention The flowchart which shows the process of one implementation of this invention The flowchart which shows the process of one implementation of this invention The flowchart which shows the process of one implementation of this invention The flowchart which shows the process of one implementation of this invention The flowchart which shows the process of one implementation of this invention The flowchart which shows the process of one implementation of this invention

  Embodiments will be described below with reference to the drawings. The present invention is not limited to the following examples.

  FIG. 1 shows an embodiment of the present invention. In FIG. 1, reference numeral 101 denotes an optical disc having N (N ≧ 3, N is an integer) recording layers accessible from one side. Reference numeral 102 denotes an objective lens for condensing the laser light on the recording layer of the optical disc 101. Reference numeral 103 denotes driving means (actuator) for driving the objective lens 102. Reference numeral 104 denotes a laser. For example, it is a semiconductor laser, and the laser wavelength is 405 nm. A light receiver 105 receives the laser light reflected from the optical disk 101.

  A focus error signal generating unit 106 generates a focus error signal indicating the deviation between the focal point on the optical disc 101 and the recording layer from the laser light received by the light receiver 105. Reference numeral 107 denotes a focus drive signal generating means for generating a focus drive signal for driving the drive means 103 in the focal direction. Reference numeral 108 denotes tracking error signal generation means for generating a tracking error signal indicating the deviation between the focal point on the optical disc 101 and the track groove on the recording layer from the laser light received by the light receiver 105.

  Reference numeral 109 denotes a tracking drive signal generating means for generating a tracking drive signal for driving the drive means 103 in the substantially radial direction of the optical disc 101. Reference numeral 110 denotes drive voltage supply means for supplying a drive voltage to the drive means 103 in accordance with the drive signal. Reference numeral 111 denotes a spherical aberration correction element that corrects spherical aberration at the focal point generated on the optical disc 101.

  Reference numeral 112 denotes spherical aberration correction control means for driving the spherical aberration correction element 111 to correct aberration. Reference numeral 113 denotes reproduction signal generation means for generating a signal indicating information recorded on the optical disc 101 from the reflected light received by the light receiver 105.

  Reference numeral 114 denotes signal amplitude measuring means for measuring the amplitude of the tracking error signal or the reproduction signal. Reference numeral 115 denotes a storage means for storing the measured amplitude amount. The storage unit 115 is implemented by a semiconductor memory, for example. Reference numeral 116 denotes a recording layer determination unit that determines a recording layer from the signal amplitude measured by the signal amplitude measurement unit 114 or the signal amplitude information stored in the storage unit 115. Reference numeral 117 denotes a control means. For example, the control means 117 is mounted by a signal processing circuit such as a CPU.

  In FIG. 1, an optical head 118 is constituted by an objective lens 102, a laser 104, and a spherical aberration correction element 111. The apparatus shown in FIG. 1 focuses laser light emitted from a laser 104 by an objective lens 102 on an optical disc 101 to produce a focal point.

  In this optical disc apparatus, the focus error signal generation means 106, the focus drive signal generation means 107, the tracking error signal generation means 108, the tracking drive signal generation means 109, the drive voltage supply means 110, the spherical aberration correction control means 112, the reproduction signal. The generation unit 113, the signal amplitude measurement unit 114, the storage unit 115, the recording layer determination unit 116, and the control unit 117 are mounted by a single LSI or MPU, for example. Arbitrary means may be mounted by another LSI.

  In FIG. 1, the spherical aberration correction element 111 is disposed in the laser light path between the laser 104 and the objective lens 102. The configuration of the spherical aberration correcting element 111 can correct the spherical aberration by displacing a lens that is inserted in the laser optical path and whose position is approximately variable in the optical axis direction. For example, it is constituted by a so-called beam expander that can correct spherical aberration of a passing light beam by changing and adjusting the distance between the lenses by a combination of two or more lenses having a variable distance between lenses. . The configuration of the spherical aberration correction element 111 is not limited to this, and a liquid crystal element or the like may be used. For example, the liquid crystal element having a concentric pattern can provide the above effect by providing a phase difference between the inner and outer peripheral portions of the light beam. In general, when a combination of lenses is used for the spherical aberration correcting element 111, the price is lower than that of the liquid crystal element and the control is easy. In addition, when a liquid crystal element is used, space can be saved as compared with a combination of lenses, and the driving time is increased.

  FIG. 2 shows the relationship between the spherical aberration correction amount of the spherical aberration correction element 111 and the position of the recording layer on the optical disc 101. In FIG. 2, a case where the optical disc 101 has four recording layers will be described as an example. On the optical disc 101, four recording layers of a third layer, a second layer, a first layer, and a zeroth layer are arranged in order from the surface of the optical disc 101 on the side facing the objective lens. At this time, the position of each recording layer from the 0th layer to the 3rd layer from the surface of the disk is represented by T0 to T3 with the disk surface as a reference (0) (T0> T1> T2> T3).

  On the other hand, the spherical aberration correction amount of the spherical aberration correction element 111 is related to the position of the aberration correction lens constituting the element. When the focus is generated on the 0th layer to the 3rd layer of the optical disc 101, the positions of the aberration correction lenses where the influence of the spherical aberration is most reduced are X0 to X3, respectively. At this time, if the aberration correction lens position is positive in the direction from X3 to X0, the aberration correction lens position has a relationship of X0> X1> X2> X3. Hereinafter, the position of the aberration correction lens is referred to as a spherical aberration correction amount.

  When the focal point is positioned on an arbitrary recording layer on the optical disc 101 and the spherical aberration correction amount is far from the correction amount corresponding to the recording layer, the tracking error signal, reproduction signal, reflected light amount, etc. due to the influence of aberration The signal amplitude decreases.

  As an example, for an optical disc having four recording layers, the relationship between the focal position and the change in signal amplitude due to the spherical aberration correction amount is illustrated in FIGS. 3A and 3B by taking a tracking error signal as an example.

  In FIG. 3 (a), if the recording layer on which the focal point is positioned coincides with the recording layer for which the spherical aberration correction is optimal, a large signal amplitude can be obtained, and either the focal position or the spherical aberration correction is different. It shows that the signal amplitude decreases when changing to a layer. The greater the amount of change in focal position or spherical aberration correction, the greater the amount of signal amplitude reduction.

  When either the focal position or the spherical aberration correction is moved to the adjacent recording layer, the amplitude reduction amount is not always the same when moved in the + direction and when moved in the-direction. Further, the amount of amplitude reduction is not necessarily the same when the focal position is moved to the adjacent layer and when spherical aberration correction is moved to the adjacent layer. The difference in the amount of decrease at this time is determined by the disc structure such as the difference in recording layer distance between adjacent recording layers, the configuration of the optical system, and the like.

  When the focal position and the spherical aberration correction position coincide with each other, the amplitude may differ depending on which recording layer the focal position and the spherical aberration correction position are located.

  The operation of the apparatus of FIG. 1 will be described with reference to the flowchart of FIG. As an example, a case where an optical disk having four recording layers as shown in FIG. 2 is mounted on the apparatus shown in FIG. 1 will be described. A case will be described in which the focus is positioned by targeting any recording layer among the four recording layers from a state in which none of the recording layers is in focus. As an example, a case where the focus is to be positioned on the first layer will be described.

  First, the apparatus of FIG. 1 starts focus pull-in (S401). In S402, the spherical aberration correction element 111 is driven and set to the position X1 so that the influence of the spherical aberration is reduced in the first layer.

  In S403, the objective lens 102 is driven in the thickness direction of the optical disc 101 to try to position the focal point on the first layer. At this time, the first layer is detected by the focus error signal or the reflected light amount signal obtained from the reflected light from the recording layer, but the number of recording layers is counted due to variations in the reflected light of the disk or the fluctuation of the reflectance due to unrecorded recording. In some cases, the focal point is positioned on a recording layer different from the first layer which is a desired recording layer.

  In S <b> 404, the amplitude of the tracking error signal generated by the tracking error signal generation unit 108 is measured by the signal amplitude measurement unit 114. The signal to be measured here is a signal generated from the reflected light from the recording layer as long as it is affected by spherical aberration, and may be, for example, a reproduction signal, a reflected light amount, or a wobble signal. The signal amplitude measured here is V1. It should be noted that the reproduction signal and the like are effective in the case of a so-called grooveless multi-layer optical disc having no groove.

  In S405, V1 measured in S404 is compared with a predetermined signal amplitude Vth. Vth is a value lower than the amplitude V11 of the tracking error signal expected to be obtained when the focal position is the first layer when the spherical aberration correction position is X1, and only the focal position is adjacent. This is a fixed value set as a value larger than the amplitude (V10 and V12) of the tracking error signal expected to be obtained when the recording layer (the 0th layer and the second layer) is shifted (V11> Vth, Vth> V10, Vth> V12).

  When the spherical aberration correction position is X1, if the amplitude is larger than Vth, the process proceeds to S410, and it is determined that the focal position is in the target recording layer (first layer).

  When the amplitude is equal to or less than Vth, it is determined that the focal position is not in the target recording layer. In order to determine which direction is shifted, the process proceeds to S406. In S406, the spherical aberration correction amount is shifted from the target recording layer position in the negative direction and set to X2. In step S407, the signal amplitude measuring unit 114 measures the amplitude of the tracking error signal generated by the tracking error signal generating unit 108 again, and the measured signal amplitude is set to V2. In S408, V2 is compared with V1 measured in S404.

  When V2> V1, with respect to the current focal position, the relationship between the spherical aberration correction positions X2 and X1 is an aberration correction position in which X2 is more suitable from the obtained amplitude relationship (V2> V1). It will be. Therefore, although the focus pull-in is performed with the first layer as a target, there is a high possibility that the focus pull-in is erroneously performed on a different recording layer on the second layer side.

  FIG. 3B shows the relationship between the signal amplitude and the aberration correction amount at this time. When V2> V1, since it rises to the right in the range from X1 to X2 in FIG. 3B, it is similar to the amplitude change in the second layer indicated by the circle and broken line in the figure. Therefore, it is considered that the focal point is located on another recording layer on the second layer side (− direction) when viewed from the target first layer.

  In this case, the process proceeds to S415, and it is determined that the focal position is shifted in the negative direction. On the other hand, if V1 ≧ V2, the process proceeds to S409. In S409, the spherical aberration correction amount is shifted in the + direction from the position of the target recording layer and set to X0. In S410, the amplitude of the tracking error signal generated by the tracking error signal generating unit 108 is measured again by the signal amplitude measuring unit 114, and the measured signal amplitude is set to V0.

  In S411, V0 is compared with V1 measured in S404. In the case of V0> V1, the relationship between the spherical focus correction positions X0 and X1 with respect to the current focal position is an aberration correction position where X0 is more preferable based on the obtained amplitude relationship (V0> V1). It will be. Therefore, although the focus pull-in is performed using the first layer as the target layer, there is a high possibility that the focus pull-in is erroneously performed on a different recording layer on the 0th layer side.

  FIG. 3B shows the relationship between the signal amplitude and the aberration correction amount at this time. In the case of V0> V1 and V1 ≧ V2, since it falls to the right in the range of X0 to X2 in FIG. 3B, it is similar to the amplitude change in the 0th layer indicated by the rhombus and the two-dot broken line in the figure. Therefore, it is considered that the focal point is located in another recording layer on the 0th layer side (+ direction) when viewed from the target first layer. In this case, the process proceeds to S413, and it is determined that the focal position is shifted in the + direction.

  On the other hand, if V1 ≧ V0, the process proceeds to S412. In this case, the relationship between the tracking error signal amplitudes V0, V1, and V2 corresponding to the three spherical aberration correction positions X0, X1, and X2 measured in S404, S407, and S410 is V1 ≧ V0 and V1 ≧ V2. When the spherical aberration correction position is the position X1 corresponding to the first layer, the maximum amplitude is obtained.

  FIG. 3B shows the relationship between the signal amplitude and the aberration correction amount at this time. In the case of V1 ≧ V0 and V1 ≧ V2, in FIG. 3B, there is a signal amplitude pole in the vicinity of X1 in the range of X0 to X2. This is similar to the amplitude change in the first layer indicated by the triangle and the dashed line in the figure. Therefore, it is determined that the focal position is in the first layer which is the target recording layer.

  By any one of the processes of S412, S413, and S415, the current recording layer shift direction with respect to the target recording layer is determined. If the determined result is the target layer (S412), since the focus pull-in is successful, the apparatus can continue other processes. Before performing other processing, the spherical aberration correction is returned to the position of X1 corresponding to the first layer.

  When the determined result is not the first layer which is the target layer, a process of moving the focal position to the target layer can be performed. In both cases of S413 and S415, the spherical aberration correction position is set again to the X1 position corresponding to the first layer, which is the target layer. If it is determined that the position is shifted in the + direction (S413), the focus position is moved in the-direction, so that the focus jump is performed toward the recording layer adjacent to the-side, that is, in the direction toward the target first layer. (S414). If it is determined that the direction is shifted in the negative direction (S415), the focus jump is performed in the direction toward the recording layer adjacent to the positive direction, that is, the target first layer (S416). The process ends through S412, S414, and S416.

  As the aberration correction position set in S406, Xp = i × X1 + (1−i) × X2 (i is a positive number, 0 ≦ i <1) instead of the spherical aberration position X2 that is optimal for the second layer. Xp represented may be used. Thereby, since the spherical aberration correction amount does not fluctuate suddenly, the influence on the stability of the focus servo can be reduced.

  Xp is (| Xp-X1 | / | X2-X1 |)> (Δt / | T1 when the thickness error of each recording layer due to disk manufacture is equal to or less than Δt with respect to the recording layer spacing | T1-T2 | By selecting i such that −T2 |), erroneous determination of the recording layer due to disc thickness error can be suppressed. In the case of BD, Δt is, for example, 5 μm. Degree.

  Similarly, Xm = j × X1 + (1−j) × X2 (j is a positive number, 0 ≦ j <1) instead of the spherical aberration position X0 that is optimal for the 0th layer as the aberration correction position set in S409. Xm represented by) may be used. Similarly to Xp, Xm is (| Xp−X1 | / | X1−X0 |) when the thickness error of each recording layer due to disk manufacture is Δt or less with respect to the recording layer spacing | T1−T0 |. By selecting j such that> (Δt / | T1-T0 |), erroneous determination of the recording layer due to the disc thickness error can be suppressed.

  Further, the recording layer determination step based on Vth in S405 may be omitted. This is because the recording layer can be determined without S405. However, in the case where S404 is present, if the probability that the optical disk apparatus erroneously pulls in the focus is low, the overall processing speed increases.

  Further, the number of recording layers is not limited to four. When the number of recording layers is generalized, that is, N recording layers from the 0th layer to the (N−1) th layer are arranged in order (N is a positive integer, N ≧ 3). Next, processing when focus pull-in is performed on the k layer (k is a positive integer, 0 ≦ k <N) will be described. The flowchart is shown in FIG.

  First, focus pull-in is started (S501). In S502, the spherical aberration correction element 111 is driven to set the aberration correction amount Xk corresponding to the kth layer. In S503, the focus is placed on the k-th layer. In S504, the signal amplitude measuring unit 114 measures an amplitude serving as an index such as a tracking error signal, and this amplitude is set to Vk. In S505, Vk and Vth are compared. If Vk> Vth, the process proceeds to S512, and it is determined that the focal point is located in the kth layer. If Vth> Vk, the process proceeds to S506.

  In S506, the spherical aberration correction element 111 is set to Xk + 1, which is a spherical aberration correction amount corresponding to the (k + 1) th layer adjacent to the + th direction of the kth layer. In S507, the signal amplitude is measured and set to Vk + 1. In S508, Vk + 1 and Vk are compared. If Vk + 1> Vk, the process proceeds to S515, and it is determined that the focal position is shifted to the recording layer in the + direction. In this case, it is determined that the focal point is erroneously positioned in the (k + 1) th layer.

  If Vk ≧ Vk + 1, the process proceeds to S509. Regarding S509 to S511, since the same processing as S409 to S411 is performed for the (k−1) th layer adjacent to the kth layer in the − direction, the description is omitted. In addition, S512 to S517 are the same as S412 to 417, and thus description thereof is omitted.

  As in S406 and S409, the spherical aberration correction amount set in S506 and S509 is not the spherical aberration correction amount corresponding to the adjacent recording layer, but the spherical aberration correction amount between the current recording layer and the adjacent recording layer. From this, the correction amount obtained by a certain ratio may be used.

  In addition, when the k-th layer that is the target of focus pull-in is the recording layer located at the end of the N recording layers arranged side by side (k = 0 or k = N−1), the other recording layers Exists only on either the + side or the-side. In this case, if k = 0 and there is no adjacent recording layer on the + side, the processing from S506 to S508 may be omitted. On the other hand, if k = N−1 and there is no adjacent recording layer on the − side, the processing from S509 to S511 may be omitted. In this case, if the determination processing in S508 is N determination, the process proceeds to S512. As described above, the present invention can also be applied when the number of recording layers is different.

  In FIG. 5, the focus pull-in is described, but the same processing may be performed during the focus jump. For example, in an optical disc in which N recording layers from the 0th layer to the (N−1) th layer are arranged in order (N is a positive integer, N ≧ 3), the a-th layer (a is a positive integer) , 0 ≦ a <N) to the k-th layer (k is a positive integer, 0 ≦ k <N), layer discrimination can also be performed. An example is shown in FIG.

  In the focus jump in FIG. 6, while the focal position is moved from the a-th layer (a is a positive integer, 0 ≦ a <N) to the k-th layer (k is a positive integer, 0 ≦ k <N), The position of spherical aberration correction is not the position Xk corresponding to the kth layer, but the position Xj (Xj = Xj) determined by the positions Xa and Xk corresponding to the ath layer and the coefficient h (h is a positive number, 0 ≦ h <1). Setting is performed at a position of h × Xk + (1−h) × Xa). In this case, the position of spherical aberration correction is adjusted to Xk after the focal position is moved. Thereby, since the spherical aberration correction amount does not fluctuate suddenly at the time of a focus jump, it is possible to suppress focus servo deviation.

  In step S601, a focus jump is started from the a-th layer to the k-th layer. At this time, the focal position is in the a-th layer, and the aberration correction position is in the position Xa corresponding to the a-th layer. In step S602, the spherical aberration correction element 111 is driven, and the aberration correction position is set to a position Xj (Xj = h × Xk + (1−h) × Xa (h is a positive number, 0 ≦ h <1)). h is set in the same range as i described above. In step S603, the objective lens 102 is driven in the focus direction, the focus position is moved to the kth layer, and the focus servo is operated in the kth layer.

  In step S <b> 604, the amplitude of the tracking error signal generated by the tracking error signal generation unit 108 is measured by the signal amplitude measurement unit 114. The amplitude at this time is Va. In S605, the spherical aberration correction element 111 is driven to set the aberration correction position Xk corresponding to the kth layer.

  In S606, the signal amplitude measuring unit 114 measures the amplitude of the tracking error signal generated by the tracking error signal generating unit 108, and this signal amplitude is set to Vk. In S607, Vk measured in S606 is compared with a predetermined signal amplitude Vth. If the amplitude is equal to or greater than Vth, the process proceeds to S612 and it is determined that the focal position is in the target recording layer.

  When the amplitude is equal to or less than Vth, it is determined that the focal position is not in the target recording layer. In order to determine which direction is shifted, the process proceeds to S608. In S608, Vk is compared with Va measured in S604. In the case of Va> Vk, the relationship between the current focal position and the aberration correction positions Xk and Xh is a correction position where Xh is less affected by aberrations because of the magnitude relationship of the obtained amplitudes. Therefore, although the focus jump is performed with the kth layer as the target layer, it is highly likely that the focus jump is mistaken for a different recording layer on the ath layer side as viewed from the kth layer.

  In this case, the process proceeds to S614, and it is determined that the focal position is shifted in the direction of the a-th layer. On the other hand, if Vk ≧ Vh, the process proceeds to S609. In step S609, the spherical aberration correction position is set from the Xk position to the Xb position opposite to Xa. In step S <b> 610, the amplitude of the tracking error signal generated by the tracking error generation unit 108 is measured again by the signal amplitude measurement unit 114. The amplitude at this time is Vb.

  In S611, Vk is compared with Vb measured in S610. In the case of Vb> Vk, the relationship between the current focal position and the spherical aberration correction positions Xb and Xk is the aberration correction position where Xb is more suitable from the obtained amplitude relationship (Vb> Vk). It will be. Therefore, although the focus jump is performed with the kth layer as the target layer, there is a high possibility that the focus jump is mistaken for a different recording layer on the opposite side to the ath layer.

  In this case, the process proceeds to S612, and it is determined that the focal position is shifted to the side opposite to the a-th layer when viewed from the k-th layer. If Vk ≧ Vb, the process proceeds to S612. In this case, the relationship between the tracking error signal amplitudes Vh, Vk, and Vb corresponding to the three spherical aberration correction positions Xj, Xh, and Xb measured in S604, S606, and S610 is Vk ≧ Vh and Vk ≧ Vb, The maximum amplitude is obtained when the spherical aberration correction position is the position Xk corresponding to the k-th layer. For this reason, it is determined that the focal position is in the kth layer which is the target recording layer.

  By any one of S612, S613, and S615, the current recording layer shift direction with respect to the target recording layer is determined. Since S614 and 616 are the same as S414 and 416 of FIG.

  Further, when the kth layer that is the target of the focus jump is the recording layer located at the end of the N recording layers arranged side by side (when k = 0 or k = N−1), they are adjacent. The recording layer exists only on the side of the a-th layer that is the focus jump source. In this case, the processing from S609 to S611 may be omitted. In this case, if the determination process in S608 is N, the process moves to S612.

  In the focus jump of FIG. 6, the process of S602 is a process included in a normal focus jump operation. In the normal focus jump, the setting of the spherical aberration correction amount Xk for the target k-th layer in S605 is completed, and the focus jump process is completed. In the embodiment of FIG. 6, the number of times of setting the spherical aberration correction amount can be reduced by adding the amplitude measurement for recording layer determination in addition to the normal focus jump processing in S604, and the total processing time can be reduced. It is shortened.

  When the control as shown in FIG. 6 is not performed, for example, the focus jump is performed in the procedure of the focus jump start in S601, the aberration correction amount Xj setting in S602, the focus control to the k-th layer in S603, and the aberration correction amount Xk in S605. After this, it is conceivable to perform the recording layer determination process from S401 as shown in FIG.

  As described above, according to the present embodiment, there is provided an optical disc apparatus capable of quickly performing focus pull-in or focus jump on a desired recording layer when the focal point is mistakenly positioned on a recording layer different from the desired recording layer. Can do.

  Note that the order of processing may be interchanged between S406 to S408 in which the aberration correction is driven to the negative side and measurement is performed and S409 to 411 in which the aberration correction is driven to the positive side and measurement is performed. That is, first, the aberration correction may be driven to the + side for measurement. A flowchart showing this is shown in FIG. S701 to 705 and S712 to 717 are the same as S401 to 405 and S412 to 417. Depending on the characteristics of the optical disc apparatus, it may be determined whether the process for driving aberration correction to the negative side is performed first or the process for driving aberration correction to the positive side is performed first. Further, depending on the direction in which the focus jump or focus pull-in is performed, it may be determined whether the process for driving the aberration correction to the negative side is performed first or the process for driving the aberration correction to the positive side is performed first. For example, in FIG. 2, when performing a focus jump from the third layer to the first layer, it is highly possible that the focus is accidentally focused on the zeroth layer, and the process of driving aberration correction to the + side is first performed. If there is a high possibility that the second layer is erroneously focused, the aberration correction may be performed first. Thereby, the processing speed can be improved.

  Further, the determination processing in S407 and S410 does not necessarily have to be performed immediately after the amplitude measurement processing in S406 and S409. That is, it may be performed after two amplitude measurements are completed. An example of a flowchart showing this is shown in FIG. Further, as shown in FIG. 9, S810 and S811 in FIG. 8 may be interchanged.

  The focus jump performed in S414 and S416 may be a focus jump process to an adjacent recording layer regardless of the number of recording layers existing between the currently positioned recording layer and the target recording layer. In this case, by performing the determination process from S404 again after performing the focus jump, if the process is performed after determining whether the recording layer after the focus jump is the target recording layer, the difference in the number of recording layers is two or more. Even if it is a deviation, the focus recording to the adjacent recording layer is repeatedly performed, so that it can finally be positioned to the target recording layer. Focus jump to the adjacent recording layer is shorter than the focus jump for multiple recording layers at the same time. The operation stability can be improved by performing the process of repeatedly performing the focus jump. The same applies to S514 and S516 in FIG. 5, S614 and S616 in FIG. 6, S714 and S716 in FIG. 7, and S814 and S816 in FIG.

  This embodiment will be described with reference to the flowcharts of FIGS. The difference from the first embodiment is that it is considered to determine which recording layer is the recording layer in which the focal point is erroneously positioned.

  Since S1001 to S1013 and S1015 in FIG. 10A are the same as S501 to S513 and S515 in FIG.

  The processing after S1015 will be described with reference to FIG. Although it is determined in S1015 that it is shifted in the-direction, there is a possibility that the recording layer is shifted in the other-direction. Therefore, in S1017, the spherical aberration correction element 111 is driven and set to the position of Xk + 2. In step S <b> 1018, the signal amplitude measuring unit 114 measures the amplitude of the tracking error signal generated by the tracking error signal generating unit 108. The amplitude at this time is Vk + 2.

  In S1019, Vk + 2 is compared with Vk + 1 measured in S1007. In the case of Vk + 2> Vk + 1, the relationship between the current focal position and the aberration correction positions Xk + 2 and Xk + 1 is a correction position where Xk + 2 is less affected by the aberration because of the magnitude relationship of the obtained amplitudes. Therefore, although the focus jump is performed using the kth layer as the target layer, it is highly possible that the focus jump is erroneously performed by two recording layers as viewed from the first layer. Therefore, in this case, it is determined that there is a shift of two layers in the negative direction (S1020). Then, the position of spherical aberration correction is set again to the position of Xk corresponding to the kth layer as the target layer, and a focus jump is performed from the currently focused (k + 2) layer to the target kth layer (S1021). ).

  On the other hand, in the case of Vk + 2 ≦ Vk + 1, Xk + 1 is a correction position with less influence of aberration, because of the magnitude relation of the obtained amplitude. Therefore, in this case, it is determined that the position is shifted by one layer in the negative direction (S1022). Then, the position of spherical aberration correction is set again to the position of Xk corresponding to the kth layer as the target layer, and a focus jump is performed from the currently focused (k + 1) th layer to the target kth layer (S1023). ). After such processing, the processing ends (S1016). Since the processing after S1013 (processing after B) is almost the same as FIG. 10B, the description thereof is omitted.

  Note that it is possible to cope with the case where there is a possibility that the focus pull-in or the focus jump may be erroneously performed by three or more layers by the same method.

  As described above, according to the present embodiment, while determining which recording layer is the recording layer in which the focus is erroneously positioned, when the focus is erroneously positioned on a recording layer different from the desired recording layer, It is possible to provide an optical disc apparatus capable of quickly executing focus pull-in or focus jump on a desired recording layer.

  In the first and second embodiments, the signal amplitude at the spherical aberration correction amount corresponding to the recording layer different from the target recording layer is acquired after the start of focus pull-in or focus jump (for example, FIG. 3). V2), for example, this signal amplitude may be acquired in advance (for example, during a focus sweep) at the time of setting up the optical disk apparatus and held in the storage means 115. However, when the spherical aberration correction element is driven and the signal amplitude is acquired after the start of focus pull-in or focus jump as in the first and second embodiments, it is effective in shortening the setup time.

  In the first and second embodiments, the layer determination is performed using different spherical aberration correction setting values for each recording layer. However, if the optimum setting value is different for each recording layer, another setting value is set. It may be used. For example, a coma aberration correction amount that is a set value of an element that corrects the relative tilt between the disk and the objective lens may be used.

  Further, by applying not only spherical aberration correction but also coma aberration correction to the first and second embodiments, it becomes possible to consider the influence of the tilt of the optical disc, so that the focus can be drawn into a desired recording layer with higher accuracy. Focus jump can be executed.

  Further, while the signal amplitude is measured by the signal amplitude measuring means 114, the tracking drive signal generating means 109 may be in a state where no tracking drive signal is generated, and the position of the objective lens 102 is a fixed position in the track crossing direction. It may be controlled to maintain.

  Further, an arbitrary waveform may be applied as a tracking drive signal to drive the objective lens 102 with an arbitrary pattern. For example, by applying a waveform of a sine wave pattern and driving the laser light focus to traverse a plurality of tracks on the optical disc 101, a track error signal can be stably output.

DESCRIPTION OF SYMBOLS 101 Optical disk 102 Objective lens 103 Drive means 104 Laser 105 Light receiver 106 Focus error signal generation means 107 Focus drive signal generation means 108 Tracking error signal generation means 109 Tracking drive signal generation means 110 Drive voltage supply means 111 Spherical aberration correction element 112 Spherical aberration Correction control means 113 Reproduction signal generation means 114 Signal amplitude measurement means 115 Storage means 116 Recording layer determination means 117 Control means 118 Optical pickup

Claims (22)

An optical disc apparatus capable of recording or reproducing information on an optical disc having three or more recording layers,
A laser that emits laser light;
An objective lens for condensing the laser light emitted from the laser onto the optical disc;
A drive unit for moving the objective lens;
A light receiving portion for receiving the laser light reflected from the optical disc;
A reflected light signal generation unit that generates a signal corresponding to the reflected light received by the light receiving unit;
A spherical aberration corrector for correcting spherical aberration generated at the focal point of the laser beam condensed on the optical disc;
A spherical aberration correction control unit for controlling the spherical aberration correction element,
Focus control is performed by causing the focus position of the laser beam to follow the recording layer with a focus jump or focus pulling as a target for any first recording layer of the recording layers, and is set by the spherical aberration correction control unit. When the spherical aberration correction amount is set to a second spherical aberration correction amount different from the first spherical aberration correction amount for correcting the spherical aberration generated when the focal point is positioned on the first recording layer. Based on the signal amplitude of the reflected light signal obtained from the reflected light signal generation unit, the positional relationship between the recording layer that the focal point of the laser beam follows by the focus control and the first recording layer is determined. An optical disk device. The optical disc apparatus according to claim 1,
When the spherical aberration correction amount is set to the first spherical aberration correction amount, the first signal amplitude obtained by the reflected light signal generation unit and the spherical aberration correction amount are set to the second spherical aberration correction amount. The second signal amplitude obtained by the reflected light signal generation unit is sometimes compared. When the second signal amplitude is large, the second recording layer side corresponding to the second spherical aberration correction amount is compared. An optical disc apparatus, wherein the focal position is moved in a direction from the recording layer existing in the first recording layer to the first recording layer. 3. The optical disc apparatus according to claim 2, wherein when the second signal amplitude is smaller than the first signal amplitude, the first spherical aberration correction amount and the second spherical aberration correction amount are different. When the third spherical aberration correction amount is set and the third signal amplitude obtained from the reflected light signal generation unit is larger than the first signal amplitude when the third spherical aberration correction amount is set. An optical disc apparatus characterized by moving the focal position in a direction from the recording layer on the side of the third recording layer corresponding to the third spherical aberration correction amount to the first recording layer. The optical disk device according to claim 3,
The optical disc apparatus according to claim 3, wherein the third recording layer is a recording layer opposite to the second recording layer as viewed from the first recording layer. The optical disc device according to claim 2,
An optical disc characterized by determining in which direction the second recording layer exists as viewed from the first recording layer in accordance with a direction in which the laser beam focus is displaced during focus jump or focus pull-in apparatus. The optical disc apparatus according to claim 1,
When the first recording layer is the recording layer located at the extreme end, the second spherical aberration correction amount is a spherical aberration correction amount corresponding to a recording layer adjacent to the first recording layer. An optical disk device. The optical disc device according to claim 2,
The second spherical aberration correction amount includes a spherical aberration correction amount set when the focus is positioned on the first recording layer, and a spherical aberration correction amount set when the focus is positioned on the second recording layer. An optical disc apparatus characterized by a spherical aberration correction amount corresponding to The optical disc device according to claim 2,
When the second signal amplitude is larger than the first signal amplitude, a fourth spherical aberration correction amount different from the first spherical aberration correction amount and the second spherical aberration correction amount is set.
When the signal amplitude obtained when the fourth spherical aberration correction amount is set is larger than the second signal amplitude, the recording layer corresponding to the fourth spherical aberration correction amount is changed to the first recording layer. An optical disc apparatus characterized in that the focal position is moved in the direction of. The optical disc apparatus according to claim 1,
The reflected light signal generation unit is a tracking error signal generation unit that generates a tracking error signal indicating a positional deviation between a laser beam focus and a track groove on the recording layer of the optical disc, and a reproduction signal of information recorded on the optical disc. An optical disc, or a reflected light amount signal generating portion for generating a reflected light amount signal indicating the intensity of laser light reflected from the optical disc and received by the light receiving portion. apparatus. The optical disc apparatus according to claim 1,
The optical disc apparatus characterized in that the spherical aberration correction element includes a lens driving element or a liquid crystal element for driving a position variable lens inserted in a laser optical path from the laser to the objective lens. The optical disc apparatus according to claim 1,
An optical disc apparatus comprising a coma aberration correction unit that corrects a relative inclination between the optical disc and the objective lens, instead of the spherical aberration correction element. A method of focus pull-in or focus jump in an optical disc apparatus capable of recording or reproducing information on an optical disc having three or more recording layers,
Emits laser light,
Condensing the laser beam on the optical disc;
Receiving the laser beam reflected from the optical disc,
Generating a reflected light signal corresponding to the reflected light received;
Spherical aberration generated at the focal point of the laser beam condensed on the optical disc is corrected by a spherical aberration correction unit,
Focus control is performed by causing the focus position of the laser beam to follow the recording layer with a focus jump or focus pulling as a target for any first recording layer of the recording layers, and is set by the spherical aberration correction control unit. Obtained when the spherical aberration correction amount is set to a second spherical aberration correction amount that is different from the first spherical aberration correction amount for correcting the spherical aberration that occurs when the focal point is positioned on the first recording layer. Focus pull-in or focus jump characterized in that, based on the signal amplitude of the reflected light signal, the positional relationship between the recording layer and the first recording layer that the focal point of the laser beam follows by focus control is determined. the method of. A method of focus pull-in or focus jump according to claim 12,
It is obtained when the spherical aberration correction amount is set to the second spherical aberration correction amount, rather than the first signal amplitude obtained when the spherical aberration correction amount is set to the first spherical aberration correction amount. When the second signal amplitude is large, the recording layer existing on the second recording layer side corresponding to the second spherical aberration correction amount is transferred from the recording layer to the first recording layer. A method of focus pull-in or focus jump, wherein the focus position is moved in the direction of heading. A method of focus pull-in or focus jump according to claim 13,
When the second signal amplitude is smaller than the first signal amplitude, a third spherical aberration correction amount different from the first spherical aberration correction amount and the second spherical aberration correction amount is set. If the third signal amplitude obtained from the reflected light signal generation unit when set to the third spherical aberration correction amount is larger than the first signal amplitude, it corresponds to the third spherical aberration correction amount. A focus pull-in or focus jump method, wherein the focal position is moved in a direction from the recording layer on the third recording layer side toward the first recording layer. The method of focus pull-in or focus jump according to claim 14,
The focus pull-in or focus jump method is characterized in that the third recording layer is a recording layer opposite to the second recording layer as viewed from the first recording layer. A method of focus pull-in or focus jump according to claim 13,
The focus is characterized in that in accordance with the direction in which the laser beam focus is displaced at the time of focus jump or focus pull-in, the direction in which the second recording layer is present as viewed from the first recording layer is determined. How to pull in or focus jump. A method of focus pull-in or focus jump according to claim 12,
When the first recording layer is the recording layer located at the extreme end, the second spherical aberration correction amount is a spherical aberration correction amount corresponding to a recording layer adjacent to the first recording layer. Focus pull-in or focus jump method. A method of focus pull-in or focus jump according to claim 13,
The second spherical aberration correction amount includes a spherical aberration correction amount set when the focus is positioned on the first recording layer, and a spherical aberration correction amount set when the focus is positioned on the second recording layer. A method of pulling in focus or focus jumping, characterized in that the amount of correction of spherical aberration corresponding to A method of focus pull-in or focus jump according to claim 13,
When the second signal amplitude is larger than the first signal amplitude, a fourth spherical aberration correction amount different from the first spherical aberration correction amount and the second spherical aberration correction amount is set.
When the signal amplitude obtained when the fourth spherical aberration correction amount is set is larger than the second signal amplitude, the recording layer corresponding to the fourth spherical aberration correction amount is changed to the first recording layer. A focus pull-in or focus jump method characterized by moving the focal position in the direction of. A method of focus pull-in or focus jump according to claim 12,
The reflected light signal is a tracking error signal indicating a positional deviation between a laser beam focus and a track groove on a recording layer of the optical disc, a reproduction signal for generating a reproduction signal of information recorded on the optical disc, or from the optical disc. A method of focus pull-in or focus jump, characterized in that it is one of reflected light quantity signals indicating the intensity of the reflected and received laser light. A method of focus pull-in or focus jump according to claim 12,
The spherical aberration correction element includes a lens driving element that drives a position-variable lens inserted in a laser optical path from the laser to the objective lens, or a liquid crystal element. Focus jump method. A method of focus pull-in or focus jump according to claim 12,
A focus pull-in or focus jump method comprising a coma aberration correction unit that corrects a relative inclination between the optical disk and the objective lens in place of the spherical aberration correction element.

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