JP2010003340A - Optical disk device and method for controlling seek thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical disk device which includes a liquid crystal element and which shortens a period for a seek operation. <P>SOLUTION: In the optical disk device 1, when the position of an optical pickup 12 is moved by a moving means 13, the drive voltage of the liquid crystal element 124 is sometimes changed. The optical disk device 1 includes a liquid crystal element control means 26 provided with a voltage control function which when the drive voltage of the liquid crystal element 124 is changed, temporarily controls the drive voltage to be an over drive voltage obtained by changing the drive voltage by a changing quantity larger than that required to change the drive voltage into a target drive voltage and after a predetermined period, to be the target drive voltage. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an optical disk apparatus used for reproducing information recorded on an optical disk or recording information on an optical disk, and more particularly, to an optical disk apparatus having a liquid crystal element in its optical system. It relates to seek control technology.

  An optical pickup is provided in an optical disk device used for reproducing information recorded on an optical disk or recording information on an optical disk. The optical pickup is provided with an optical system that guides the light emitted from the light source to the optical disc and guides the return light reflected by the optical disc to the light receiving element.

  By the way, it is known that wavefront aberration (mainly coma aberration) occurs when an optical pickup is used, for example, when there is a warp of an optical disk or an installation error of an objective lens provided in an optical system of the optical pickup. Further, it is known that wavefront aberration (mainly spherical aberration) occurs due to a difference in thickness of the transparent cover layer that protects the information recording surface when the optical pickup is used.

When such wavefront aberration occurs when using the optical pickup, the reproduction and recording quality of the optical disk apparatus deteriorates. For this reason, conventionally, various techniques for reducing the influence of such wavefront aberration have been disclosed. Among them, there is a method of canceling wavefront aberration by disposing a liquid crystal element in an optical system of an optical pickup and giving a phase difference to light passing therethrough (see, for example, Patent Document 1). A method of correcting wavefront aberration using a liquid crystal element is widely used because it has an advantage that the apparatus can be downsized compared to a configuration in which a lens is mechanically moved to correct wavefront aberration.
Japanese Patent Laid-Open No. 10-20263 Japanese Patent Laid-Open No. 2007-80402

  However, in the case of a method for correcting wavefront aberration using a liquid crystal element, it takes a long time (for example, several hundred ms) to stabilize after changing the setting of the liquid crystal element. Have a problem.

  FIG. 7 is a flowchart showing an operation flow at the time of a seek operation in a conventional optical disc apparatus having a liquid crystal element. Here, a case will be described as an example where the liquid crystal element corrects wavefront aberration (coma aberration) caused by warpage of the optical disc, lens attachment error, and the like. In this example, the setting conditions of the liquid crystal element are appropriately changed according to the position (the position in the radial direction of the optical disk) accessed by the optical pickup.

  Referring to FIG. 7, when a seek command is issued, the setting of the liquid crystal element is changed so that the wavefront aberration can be appropriately corrected at the target position (step S101). When the setting of the liquid crystal element is changed, the process waits until the liquid crystal element can exhibit an effect commensurate with the setting condition (that is, the liquid crystal element is stabilized) (step S102). Thereafter, when the liquid crystal element is stabilized, the movement of the optical pickup is started so that the position of the light spot is formed at the target position (target address) (step S103). Then, the position of the optical pickup is moved to the target position (step S104), and the seek operation ends.

  In such a conventional seek operation control method, the time required for the seek operation is approximately the sum of the time until the optical pickup moves to the target position and the time until the liquid crystal element is stabilized. As described above, since the time until the liquid crystal element is stabilized is as long as several hundred ms, for example, there is a problem that the time required for the seek operation becomes too long.

  In this regard, Patent Document 2 proposes an optical disc apparatus that parallelizes the control operation of the aberration correction means (which may be a liquid crystal element) and the control operation of the feeding means that moves the optical pickup in the radial direction of the optical disc. is doing. For this reason, it can be considered that the above-described steps S101 and S103 are started simultaneously with reference to the technique of Patent Document 2. By doing so, the time required for the seek operation is shortened.

  However, when the moving distance of the optical pickup is short, for example, the time until the optical pickup is moved to the target position is short, and eventually it is necessary to wait until the liquid crystal element is stabilized. For this reason, even if the technique of Patent Document 2 is used, it cannot be said that the time required for the seek operation is sufficiently shortened, and it has been desired to further reduce the time required for the seek operation.

  In view of the above points, an object of the present invention is to provide an optical disc apparatus that includes a liquid crystal element and that can reduce the time required for a seek operation. Another object of the present invention is to provide a seek control method capable of shortening the time required for a seek operation in an optical disc apparatus having a liquid crystal element.

  To achieve the above object, the present invention provides an optical pickup that irradiates an optical disc with light and receives return light from the optical disc and outputs a signal, and is disposed in the optical system of the optical pickup, and corrects wavefront aberration. An optical disk device comprising: a liquid crystal element that performs the optical pickup; and a moving unit that moves the optical pickup in a radial direction of the optical disk, wherein the position of the optical pickup is moved by the moving unit. When the driving voltage may be changed and the driving voltage of the liquid crystal element is changed, the driving voltage is changed by a change amount larger than a change amount necessary for changing the driving voltage to a target driving voltage. A liquid crystal element control means having a voltage control function for setting an overdrive voltage and setting the target drive voltage after a predetermined time has elapsed is provided.

  According to this configuration, when changing the drive voltage of the liquid crystal element, the liquid crystal element control means may perform voltage control that once sets the drive voltage as the overdrive voltage and then sets the target drive voltage. When such voltage control is performed, the time required until the refractive index of the liquid crystal reaches the target refractive index can be increased as compared with the case where the target driving voltage is immediately set, and the time required for the liquid crystal element to be stabilized. Can be shortened. For this reason, it is possible to shorten the time required for the seek operation that involves changing the setting (drive voltage) of the liquid crystal element.

  In the optical disk apparatus having the above-described configuration, the movement of the optical pickup by the moving unit and the control operation for changing the driving voltage of the liquid crystal element by the liquid crystal element control unit may be performed in parallel. According to this configuration, it is possible to shorten the time required for the seek operation that involves changing the setting (driving voltage) of the liquid crystal element, as compared with the case where the other operation is performed after the operation of either one is completed. .

  In the optical disk apparatus having the above-described configuration, whether the liquid crystal element control unit uses the overdrive voltage based on a moving amount of the optical pickup by the moving unit when the driving voltage of the liquid crystal element is changed. If the overdrive voltage is not used, the target drive voltage may be used instead of the overdrive voltage.

  If the amount of movement of the optical pickup during the seek operation is large, the liquid crystal element drive voltage is not set to the overdrive voltage, and the optical pickup's stability time is shorter than the stability time of the liquid crystal element when it is immediately changed to the target drive voltage. Travel time may be longer. In such a case, it is not necessary to bother to use the overdrive voltage to shorten the stabilization time of the liquid crystal element, and the optical disk apparatus having this configuration can be obtained. In the case of this configuration, since the overdrive voltage is not used more than necessary, the power consumption can be reduced.

  In order to achieve the above object, the present invention provides a seek control method for an optical disc apparatus in which a liquid crystal element for correcting wavefront aberration is arranged in an optical system of an optical pickup, and the optical pickup is moved as a seek operation. When it is necessary to change the driving voltage of the liquid crystal element, it is an overdrive voltage that is changed by a change amount larger than the change amount necessary to change the drive voltage to a target drive voltage. A control operation is performed in which the target drive voltage is set after a predetermined time has elapsed.

  According to this configuration, when the drive voltage of the liquid crystal element is changed, the time until the refractive index of the liquid crystal reaches the target refractive index can be increased compared to the case where the target drive voltage is immediately set, and the liquid crystal element is stabilized. Can be shortened. For this reason, it is possible to shorten the time required for the seek operation that involves changing the setting (drive voltage) of the liquid crystal element.

  In the seek control method of the optical disc apparatus having the above-described configuration, the movement of the optical pickup may be performed in parallel with the control operation of the driving voltage of the liquid crystal element. According to this configuration, it is possible to shorten the time required for the seek operation that involves changing the setting (driving voltage) of the liquid crystal element, as compared with the case where the other operation is performed after the operation of either one is completed. .

  Further, in the seek control method of the optical disc apparatus having the above-described configuration, when it is necessary to change the driving voltage of the liquid crystal element, before setting the overdrive voltage, based on the moving amount of the optical pickup by the moving unit. Determining whether or not to use the overdrive voltage, and when it is determined not to use the overdrive voltage, changing to the target drive voltage without using the overdrive voltage It is also good. According to this configuration, since an overdrive voltage is not used unnecessarily, it is possible to reduce power consumption associated with a seek operation.

  ADVANTAGE OF THE INVENTION According to this invention, it is an optical disk apparatus provided with a liquid crystal element, Comprising: The optical disk apparatus which can shorten the time which seek operation requires can be provided. In addition, according to the present invention, it is possible to provide a seek control method capable of reducing the time required for a seek operation in an optical disc apparatus including a liquid crystal element.

  Embodiments of an optical disc apparatus and a seek control method for an optical disc apparatus according to the present invention will be described below in detail with reference to the drawings.

  FIG. 1 is a block diagram showing the configuration of the optical disc apparatus of the present embodiment. The optical disc device 1 of this embodiment is a device used for reproducing information recorded on the optical disc 40 and recording information on the optical disc 40. The present invention can also be applied to an apparatus that only reproduces information recorded on the optical disk 40 or an apparatus that only records information on the optical disk 40. Here, an apparatus that can reproduce and record an optical disk is used. This will be described as an example.

  The spindle motor 11 is a motor for continuously rotating the optical disc 40. A chuck portion (not shown) for detachably holding the optical disc 40 is attached to the output shaft of the spindle motor 11. For this reason, when the spindle motor 11 is driven in a state where the optical disk 40 is held on the chuck portion, the optical disk 40 is continuously rotated. The drive of the spindle motor 11 is controlled by the spindle motor control unit 21.

  The optical pickup 12 irradiates the optical disc 40 with light, receives the return light reflected by the optical disc 40, converts the optical information into an electrical signal, and outputs it. The optical system of the optical pickup 12 includes a light source (for example, a semiconductor laser) 121 for irradiating the optical disc 40 with light and an objective lens for condensing the light emitted from the light source 121 on the information recording surface 40 a of the optical disc 40. 122, and a light receiving element 123 that receives the return light from the optical disc 40 and performs photoelectric conversion.

  The objective lens 122 provided in the optical pickup 12 is mounted on the objective lens actuator 125, and is in the focus direction (up and down direction in FIG. 1) parallel to the rotation axis of the optical disc 40 and in the radial direction of the optical disc 40 (left and right direction in FIG. 1). It is possible to move in the track direction parallel to the track. The configuration of the objective lens actuator 125 is a well-known configuration in which the objective lens 125 is moved by moving the holder that holds the objective lens 122 using the electromagnetic action of the current flowing in the coil and the magnetic field generated by the permanent magnet. Since it is a structure, the description is abbreviate | omitted here.

  In the optical system of the optical pickup 12, a liquid crystal element 124 is disposed in the optical path between the light source 121 and the objective lens 122 so that coma aberration (wavefront aberration) can be corrected. In the present embodiment, the liquid crystal element 124 is mounted on the objective lens actuator 125 together with the objective lens 122, and is provided so as to move together with the objective lens 122.

  2A and 2B are diagrams for explaining the configuration of the liquid crystal element 124 included in the optical disc apparatus 1 of the present embodiment. FIG. 2A is a schematic cross-sectional view of the liquid crystal element 124, and FIG. It is a schematic plan view which shows the structure of one transparent electrode 52 provided. As shown in FIG. 2A, the liquid crystal element 124 holds the liquid crystal 51, the two transparent electrodes 52 and 53 sandwiching the liquid crystal 51, and two of the two transparent electrodes 52 and 53, respectively. Glass substrates 54 and 55.

  When a voltage is applied to the liquid crystal 51 by the two transparent electrodes 52, 52, the orientation direction of the liquid crystal molecules changes and the refractive index changes. Depending on the magnitude of the applied voltage, the amount of change in the alignment direction of the liquid crystal molecules varies, and the refractive index also changes. Therefore, by adjusting the voltage applied between the two transparent electrodes 52 and 53, the phase shift (phase difference) applied to the light passing through the liquid crystal element 124 can be adjusted.

  As shown in FIG. 2B, the transparent electrode 52 includes five divided electrodes 52a, 52b, 52c, 52d, and 52e. The five divided electrodes 52a to 52e can be given potentials independently. On the other hand, the transparent electrode 53 serves as one common electrode without being divided. Therefore, different driving voltages can be applied to the liquid crystal 51 sandwiched between the divided electrodes 52a to 52e and the transparent electrode 53, and the light passing through the divided electrodes 52a to 52e is respectively Different phase shifts (phase differences) can be given. As a result, the liquid crystal element 124 can correct coma caused by warpage of the optical disk 40, attachment error of the objective lens 122, and the like.

  FIG. 3 is a schematic diagram illustrating an example of a coma aberration distribution generated in the radial direction of the optical disc 40. As shown in FIG. 3, the coma aberration distribution is point-symmetric with respect to the center of the light spot. For this reason, if the liquid crystal element 124 gives a phase difference in the opposite direction to the coma aberration distribution as shown by the dotted line in FIG. 3, the coma aberration can be canceled (coma aberration correction is performed). The division pattern of the transparent electrode 52 of the liquid crystal element 124 shown in FIG. 3B is formed in consideration of this point.

  The shapes of the divided electrode 52b and the divided electrode 52c, and the divided electrode 52d and the divided electrode 52e are formed in line symmetry. A phase difference is generated between the divided electrode 52b and the divided electrode 52c having substantially the same absolute value but different directions. In addition, the divided electrodes 52d and 52e also generate phase differences having substantially the same absolute value but different directions. Note that the amount of phase difference generated in the light passing through each of the divided electrodes 52a to 52e is an amount determined by an adjustment experiment or the like performed at the time of manufacturing the optical disc apparatus 1.

  In the present embodiment, as shown in FIG. 4, the radial position of the optical disc 40 is classified into three regions, and different setting conditions (drive voltage; this) are applied to each of the first to third regions. The liquid crystal element 124 is driven by determining the amount of phase difference generated by (3). The setting conditions of the liquid crystal element 124 in each region (first to third regions) are stored in advance in the memory 31 as a table.

  In the present embodiment, the regions where the settings of the liquid crystal element 124 are different are the three regions of the first to third regions, but this number may naturally be changed. In this embodiment, the setting conditions of the liquid crystal element 124 are stored in advance as a table. However, the present invention is not limited to this configuration. For example, using a tilt sensor or the like, a setting condition for the liquid crystal element is obtained each time the optical disk 40 is inserted into the optical disk apparatus 1, and the liquid crystal element is obtained using the obtained setting condition. Needless to say, the configuration for performing the above-described driving may be used.

  Returning to FIG. 1, the optical pickup moving mechanism (OPU moving mechanism) 13 is a means for moving the optical pickup 12 in the radial direction of the optical disc 40 (the left-right direction in FIG. 1). The optical pickup moving mechanism 13 can be configured by, for example, a stepping motor, a gear train rotated by the stepping motor, and a rack attached to, for example, a base portion of the optical pickup 12. Control of driving of the optical pickup moving mechanism 13 is performed by the OPU moving mechanism control unit 23.

  The laser control unit 22 controls the laser power of the laser light emitted from the light source (semiconductor laser) 121 of the optical pickup 12. Further, the light source 121 made of a semiconductor laser is oscillated in accordance with the pulse waveform formed by the recording processing unit 29. Note that the recording processing unit 29 receives, for example, recording data to be recorded on the optical disc 40 from the outside, and performs error correction code (ECC) addition and encoding processing. Further, a recording pulse is generated according to a predetermined write strategy (for example, stored in the memory 31).

  The RF amplifier 24 receives the electrical signal output from the light receiving element 123 and generates a reproduction RF signal, a focus error signal (FE signal), a tracking error signal (TE signal), and the like. The generated reproduction RF signal is subjected to waveform equalization processing, data demodulation processing, error correction processing, and the like in the reproduction processing unit 28, and is output as reproduction data.

  The servo control unit 25 generates a focusing drive signal and a tracking drive signal based on the FE signal and the TE signal. The generated focusing drive signal and tracking drive signal are sent to the actuator control unit 27. The servo control unit 25 also supplies a control signal to the OPU movement mechanism control unit 23.

  The liquid crystal element control unit 26 controls a driving voltage for driving the liquid crystal element 124. Details of the control operation related to the setting condition (drive voltage) of the liquid crystal element 124 by the liquid crystal element control unit 26 will be described later.

  The actuator control unit 27 drives the objective lens actuator 125 based on the focusing drive signal and the tracking drive signal output from the servo control unit 25. Thereby, focusing control and tracking control using the objective lens actuator 125 are executed.

  The system controller 30 includes a microcomputer and appropriately executes control processing according to required operations to be executed by each unit constituting the optical disc apparatus 1. The system controller 30 includes a memory 31. The memory 31 stores, for example, various parameters and operation programs necessary for the system controller 30 to perform various processes.

  Next, details of the control operation related to the setting condition (drive voltage) of the liquid crystal element 124 by the liquid crystal element control unit 26 will be described. In the optical disc apparatus 1 of the present embodiment, when reproducing or recording information, the liquid crystal element 124 is not always driven under fixed setting conditions. As described above, the setting condition of the liquid crystal element 124 may be changed when the optical pickup 12 is moved in the radial direction of the optical disc 40 by the optical pickup moving mechanism 13. That is, when the optical pickup 12 is moved by the optical pickup moving mechanism 13 and the seek operation in which the optical pickup 12 moves from the current address to the target address, the liquid crystal element control unit 26 performs a control operation to change the setting of the liquid crystal element 124. There is. Hereinafter, this control operation will be described with reference to FIG.

  FIG. 5 is a diagram for explaining the control operation of the liquid crystal element control unit 26 provided in the optical disc apparatus 1 of the present embodiment. FIG. 5A is a first control executed by the liquid crystal element control unit 26. FIG. 5B is a diagram for explaining the operation, and FIG. 5B is a diagram for explaining the second control operation executed by the liquid crystal element control unit 26.

  First, the first control operation executed by the liquid crystal element control unit 26 will be described with reference to FIG. In the first control operation, when it is necessary to change the setting condition of the liquid crystal element 124 during the seek operation, the drive voltage of the liquid crystal element 124 is set in advance in the memory 31 as the condition of the target address position simultaneously with the start of the seek operation. It refers to an operation that simply changes to a stored drive voltage. That is, in the first control operation, when the seek operation is started, the liquid crystal element control unit 26 immediately changes the drive voltage of the liquid crystal element 124 from the current setting to the target setting.

  The liquid crystal 51 (see FIG. 2) does not immediately have the target refractive index even when the voltage applied to the transparent electrodes 52 and 53 (see FIG. 2) is changed, but the time lag as shown in FIG. With the target refractive index. In this specification, the time from when the drive voltage is changed to when the liquid crystal element is stabilized at the target refractive index is expressed as the stable time of the liquid crystal element. Stabilization time is required.

  In the liquid crystal element 124 of this embodiment, the transparent electrode 52 has five divided electrodes 52a to 52e, and the drive voltages generated between the divided electrodes 52a to 52e and the transparent electrode 53 are different. For this reason, precisely, the time until the refractive index of the liquid crystal 51 is stabilized differs in each part. In the present embodiment, the longest time is set as the stable time of the liquid crystal element 124. .

  In the first control operation, the time required for the seek operation is determined as follows. When the time required for the optical pickup 12 to move from the current address to the target address (this time is expressed as the movement time in FIG. 5) is longer than the stabilization time of the liquid crystal element 124 (movement time in FIG. 5). In the case of II), the time required for the seek operation is almost determined by the movement time. On the other hand, when the movement time is shorter than the stabilization time of the liquid crystal element 124 (in the case of the movement time I in FIG. 5), the time required for the seek operation is determined by the stabilization time of the liquid crystal element 124.

  By the way, in order to solve the problem of shortening the time required for the seek operation, it is conceivable to shorten the moving time and the stabilization time of the liquid crystal element 124. The time required for the seek operation is shortened by shortening the stabilization time. For this reason, as the control operation performed by the liquid crystal element control unit 26, not only the first control operation but also the second control operation can be performed.

  The second control operation executed by the liquid crystal element control unit 26 will be described with reference to FIG. In the second control operation, when it is necessary to change the setting conditions of the liquid crystal element 124 during the seek operation, the drive voltage of the liquid crystal element 124 is immediately set from the current setting to the target setting simultaneously with the start of the seek operation. Instead, the overdrive voltage is once set, and the target drive voltage is changed after a predetermined time.

  Here, the overdrive voltage is a drive voltage obtained by changing a change amount larger than the change amount (Vn in FIG. 5B) necessary for changing from the current setting to the target setting. Point to. In FIG. 5B, when the drive voltage is originally increased by Vn, an overdrive voltage is obtained by giving a voltage change obtained by adding the overdrive amount Vod to Vn.

  FIG. 5B shows a case where the drive voltage is increased when the current setting is changed to the target setting, but the drive voltage may be decreased when the current setting is changed to the target setting. In this case, the overdrive voltage is obtained by further reducing the excessive amount (overdrive amount) of the voltage amount that should be lowered. Thus, in this specification, in order to change from the current setting to the target setting, including not only the case where the driving voltage is higher than the target driving voltage but also the case where the driving voltage is lower than the target driving voltage. All drive voltages obtained by changing the change amount larger than the required change amount are expressed as overdrive voltages.

  When the overdrive voltage is used, the speed at which the refractive index changes can be increased compared to the case where the original drive voltage (corresponding to the target drive voltage) is used. Therefore, as can be seen by comparing FIG. 5A and FIG. 5B, when the overdrive voltage is set for a predetermined time (overdrive time Tod) and then the target drive voltage is set, the target drive is immediately performed. The stabilization time of the liquid crystal element 124 can be shortened compared to the case where the voltage is used.

  The overdrive amount Vod affects the speed of change in the refractive index of the liquid crystal 51. On the other hand, if the overdrive time Tod is too long, the refractive index of the liquid crystal element 124 is too far from the target refractive index, and the stabilization time of the liquid crystal element 124 becomes longer. If the overdrive time Tod is too short, the effect of using the overdrive voltage is reduced. For this reason, optimum values of the overdrive amount Vod and the overdrive time Tod are obtained in advance by experiments so that the stable time of the liquid crystal element 124 is shorter than the movement time. The obtained overdrive amount Vod and overdrive time Tod are stored in the memory 31 as a table.

  Further, as described above, in the liquid crystal element 124 of the present embodiment, the transparent electrode 52 is divided into five divided electrodes 52 a to 52 e, and a drive voltage generated between each divided electrode 52 a to 52 e and the transparent electrode 53. Are different. For this purpose, an overdrive amount Vod and an overdrive time Tod are obtained for each part and stored in the memory 31.

  The first control operation and the second control operation executed by the liquid crystal element control unit 26 are as described above. In the optical disc apparatus 1 according to the present embodiment, the first control operation and the second control operation are performed. Is properly used as follows.

  As described above, when the movement distance of the optical pickup 12 during the seek operation is long, the time required for the seek operation may be determined by the movement time in both the first control operation and the second control operation. . For this reason, in such a case, the first control operation is used. On the other hand, when the movement distance of the optical pickup 12 is short, using the first control operation may require a longer time for the seek operation than the movement time. In such a case, the second control operation is used. In this way, the time spent only for waiting for the liquid crystal element 124 to become stable is eliminated, and the time required for the seek operation can be shortened.

  Note that the movement distance of the optical pickup 12 when the time required for the seek operation is determined by the movement time also as the first control operation is obtained in advance by experiment, simulation, or the like, and is stored in the memory 31 as the threshold value A. Then, the liquid crystal element control unit 26 compares the movement distance of the optical pickup 12 calculated when starting the seek operation with the threshold value A, and determines which one of the first control operation and the second control operation. It is configured to determine whether to use the control operation.

  Next, the seek operation in the optical disc apparatus 1 of the present embodiment will be described with reference to FIG. FIG. 6 is a flowchart showing an operation flow during a seek operation in the optical disc apparatus 1 of the present embodiment.

  A seek operation is started by a seek command from the system controller 30. In starting the seek operation, the system controller 30 calculates the movement amount of the optical pickup 12 from the current address and the target address (step S1). In the present embodiment, the moving distance is calculated as the moving amount. However, the moving distance may be calculated as the number of tracks accompanying the movement.

  Next, it is determined whether it is necessary to change the setting (drive voltage) of the liquid crystal element 124 (step S2). As described above, in the optical disc apparatus 1 of the present embodiment, the radial position of the optical disc 40 is classified into three regions (see FIG. 4), and the liquid crystal element 124 is driven under different setting conditions in each region. I have to. For this reason, when the movement from the current address to the target address is within the same area, the setting of the liquid crystal element 124 is not changed. Therefore, here, it is determined whether or not the movement from the current address to the target address is a movement to another area.

  When changing the setting of the liquid crystal element 124, the liquid crystal element control means 26 determines whether or not the movement amount calculated in step S1 is smaller than the threshold value A (step S3). When the movement amount is smaller than the threshold value A, the liquid crystal element control means 26 executes the second control operation in order to forcibly shorten the stabilization time of the liquid crystal element 124.

  That is, the liquid crystal element control unit 26 refers to a table stored in advance in the memory 31 and sets the drive voltage for driving the liquid crystal element 124 to the overdrive voltage (step S4). Almost simultaneously with step S4, the system controller 30 instructs the OPU moving mechanism control unit 23 to start moving the optical pickup 12 by the optical pickup moving mechanism 13 (step S5).

The liquid crystal element control unit 26 checks whether or not a predetermined time (overdrive time Tod) stored in the memory 31 has passed in advance (step S6), and when the predetermined time Tod has passed, the driving voltage of the liquid crystal element 124 is checked. Is changed to the target drive voltage stored in advance in the memory 31 as the drive voltage at the target position (step S7). In this way, the movement time of the optical pickup 12 becomes longer than the stabilization time of the liquid crystal element 124. For this reason, thereafter, the system controller 30 checks whether or not the optical pickup 12 has reached the target address (step S11), and the seek operation is completed when the optical pickup 12 reaches the target address.

  In step S3, when the movement amount is equal to or greater than the threshold A, the liquid crystal element control unit 26 executes the first control operation because it is not necessary to forcibly shorten the stabilization time of the liquid crystal element 124. That is, the drive voltage of the liquid crystal element 124 is changed to the target drive voltage stored as the drive voltage of the liquid crystal element 124 at the target position without setting it as the overdrive voltage (step S8). Almost simultaneously with step S8, the system controller 30 instructs the OPU moving mechanism control unit 23 to start moving the optical pickup 12 by the optical pickup moving mechanism 13 (step S9).

  Also in this case, the movement time of the optical pickup 12 is longer than the stabilization time of the liquid crystal element 124. For this reason, thereafter, the system controller 30 checks whether or not the optical pickup 12 has reached the target address (step S11), and the seek operation is completed when the optical pickup 12 reaches the target address.

  If it is determined in step S2 that the setting of the liquid crystal element 124 is not changed, the liquid crystal element control unit 26 maintains the drive voltage at the current setting. Therefore, in this case, the system controller 30 simply issues a command to the OPU movement mechanism control unit 23, and the movement of the optical pickup 12 by the optical pickup movement mechanism 13 is started (step S10). Then, it is confirmed whether or not the optical pickup 12 has reached the target address (step S11), and the seek operation is completed when the optical pickup 12 reaches the target address.

  When the seek operation is controlled as described above, there is no waiting time that is spent only for waiting for the liquid crystal element 124 to stabilize. For this reason, it is possible to shorten the time for the seek operation.

  The embodiment described above is an example, and the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the object of the present invention.

  For example, in the present embodiment, the liquid crystal element control unit 26 performs the first control operation (not using the overdrive voltage) and the second control operation (overdrive voltage) according to the amount of movement of the optical pickup 12 during seeking. Used) and used properly. However, the present invention is not limited to this. In other words, the second control operation that always uses the overdrive voltage may be used as the control operation of the liquid crystal element 124.

  In the present embodiment, when the seek operation is performed, the movement start of the optical pickup 12 and the change of the setting condition of the liquid crystal element 124 are performed almost simultaneously. However, the present invention is not limited to this configuration. That is, for example, the timing for changing the setting conditions of the liquid crystal element 124 and the timing for starting the movement of the optical pickup 12 may be shifted.

  In some cases, the optical pickup 12 may be moved after waiting for the liquid crystal element 124 to stabilize on the premise that the above-described second control operation is used (overdrive voltage is used) The setting conditions of the liquid crystal element may be changed after the movement of the pickup 12 is completed. Even in such a configuration, since the stabilization time of the liquid crystal element 124 is shortened, it can be a means for shortening the seek operation time. However, the control operation for changing the driving voltage of the liquid crystal element 124 by the liquid crystal element control unit 26 and the movement of the optical pickup 12 are preferably performed in parallel.

  In the present embodiment, the configuration in which the present invention is applied when the liquid crystal element is used to correct coma is shown. However, the present invention can be widely applied to an optical disc apparatus including a liquid crystal element in which setting conditions may be changed during a seek operation.

  Specifically, for example, when the optical disc to be reproduced or recorded by the optical disc apparatus is a multilayer optical disc (an optical disc having a plurality of information recording surfaces in the thickness direction), a focus jump may be accompanied during a seek operation. Here, the focus jump refers to a case where the position where the light spot is formed moves from one information recording surface to another information recording surface. When such a focus jump is performed, a spherical aberration is generated. Therefore, a liquid crystal element is used to correct this, and a setting condition of the liquid crystal element is changed. The liquid crystal element in this case is different from the case of the present embodiment in the division pattern of the transparent electrode 52 and is a pattern divided into a plurality of concentric regions.

  Even in such a case, the overdrive voltage is changed by a change amount larger than the change amount necessary for setting the drive voltage of the liquid crystal element as the target drive voltage. If voltage control is performed, the time required for the seek operation may be shortened. For this reason, the present invention is applicable also in such a case.

  According to the present invention, it is possible to reduce the time required for a seek operation in an optical disc apparatus including a liquid crystal element. That is, the present invention is a useful technique for an optical disc apparatus including a liquid crystal element.

These are block diagrams which show the structure of the optical disk apparatus of this embodiment. These are figures for demonstrating the structure of the liquid crystal element with which the optical disk apparatus of this embodiment is provided. These are schematic diagrams showing an example of a coma aberration distribution generated in the radial direction of the optical disc. These are the figures for demonstrating the relationship between the setting conditions of a liquid crystal element and the position of the radial direction of an optical disk in the optical disk device of this embodiment. These are figures for demonstrating control operation of the liquid crystal element control part with which the optical disk device of this embodiment is provided. These are flowcharts showing an operation flow during a seek operation in the optical disc apparatus of the present embodiment. These are the flowcharts which show the operation | movement flow at the time of the seek operation | movement in the conventional optical disk apparatus which has a liquid crystal element.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical disk apparatus 12 Optical pick-up 13 Optical pick-up moving mechanism (moving means)
26 Liquid crystal element control unit (liquid crystal element control means)
40 Optical disk 124 Liquid crystal element

Claims (6)

An optical pickup that irradiates the optical disc with light and receives return light from the optical disc, and outputs a signal;
A liquid crystal element disposed in the optical system of the optical pickup for correcting wavefront aberration;
Moving means for moving the optical pickup in a radial direction of the optical disc;
An optical disc device comprising:
When the position of the optical pickup is moved by the moving means, the driving voltage of the liquid crystal element may be changed,
When the drive voltage of the liquid crystal element is changed, the overdrive voltage is changed by a change amount larger than the change amount necessary for changing the drive voltage to the target drive voltage, and after a predetermined time has elapsed. An optical disc apparatus comprising liquid crystal element control means having a voltage control function for setting the target drive voltage.   2. The optical disc apparatus according to claim 1, wherein the movement of the optical pickup by the moving unit and the control operation for changing the driving voltage of the liquid crystal element by the liquid crystal element control unit are performed in parallel. The liquid crystal element control means is provided to determine whether or not to use the overdrive voltage based on a moving amount of the optical pickup by the moving means when the driving voltage of the liquid crystal element is changed. ,
3. The optical disc apparatus according to claim 1, wherein when the overdrive voltage is not used, the target drive voltage is used instead of the overdrive voltage. A seek control method for an optical disc apparatus in which a liquid crystal element for correcting wavefront aberration is arranged in an optical system of an optical pickup,
When it is necessary to change the driving voltage of the liquid crystal element by moving the optical pickup as a seek operation,
Once the overdrive voltage is changed by a change larger than the change necessary to change the drive voltage to the target drive voltage, a control operation is performed to make the target drive voltage after a predetermined time has elapsed. A seek control method for an optical disk device.   5. The seek control method for an optical disc apparatus according to claim 4, wherein the movement of the optical pickup is performed in parallel with a control operation of the drive voltage of the liquid crystal element. When it is necessary to change the driving voltage of the liquid crystal element, it is determined whether to use the overdrive voltage based on the moving amount of the optical pickup by the moving means before setting the overdrive voltage. Has steps,
6. The seek control method for an optical disc apparatus according to claim 4, wherein when it is determined that the overdrive voltage is not used, the target drive voltage is changed to the target drive voltage without setting the overdrive voltage. .

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