Patent Document

CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is based upon and claims benefit of priority under 35 USC 119 from the Japanese Patent Application No. 2005-314130, filed on Oct. 28, 2005, the entire contents of which are incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to a playback device and a control method therefor.  
         [0003]     An optical disc device rotates an optical disc using a spindle motor. As methods for controlling the rotational speed of a spindle motor, there are proposed various methods. A method for controlling the rotational speed of a spindle motor will be specifically explained.  
         [0004]     Generally, an FG signal generator which generates an FG (Frequency Generator) signal by outputting a pulse with a predetermined shape each time a spindle motor rotates by a fixed angle is attached to the spindle motor.  
         [0005]     An optical disc device can calculate the rotational speed of a spindle motor by detecting pulses of an FG signal output from an FG signal generator and control the rotational speed of the spindle motor on the basis of the calculation result.  
         [0006]     Pits for recording data such as video data are formed in an optical disc. Sync patterns as synchronization signals are also recorded in the pits. An optical disc device can also control the rotational speed of a spindle motor on the basis of sync patterns detected from data obtained by irradiating pits with laser light.  
         [0007]     An optical disc also has wobbles, each composed of a groove formed to wobble in fixed cycles. Each wobble mainly serves as a guide groove. An optical disc device can also control the rotational speed of a spindle motor on the basis of wobble signals obtained by irradiating wobbles with laser light.  
         [0008]     A BCA (burst cutting area) is formed on the inner peripheral side of an optical disc based on a current DVD (Digital Versatile Disc) standard or the HD DVD standard, which is considered to be a leading one of next-generation DVD standards. A barcode-like pattern is formed in the BCA to radiate in the radial direction of the optical disc, depending on data to be recorded. For example, unique identification information assigned to the optical disc and copy protection information are recorded in the BCA.  
         [0009]     As described above, no pits are formed in a BCA of an optical disc based on a DVD standard or the HD DVD standard, unlike a data area. Accordingly, in the BCA, no sync patterns as described above are recorded, and no wobbles are formed.  
         [0010]     For this reason, an optical disc device with such an optical disc controls the rotational speed of a spindle motor on the basis of an FG signal output from an FG signal generator when reading out data from a BCA of the optical disc.  
         [0011]     Assume that no FG signal generator is provided for the spindle motor. In this case, when the optical disc device reads out data from the BCA, it cannot control the rotational speed of the spindle motor. This makes it impossible to stably rotate an optical disc at a fixed rotational speed and reduces data readout accuracy. Accordingly, an FG signal generator needs to be provided for a spindle motor, and the size of an optical disc device increases correspondingly.  
         [0012]     The following is the name of a document pertaining to an optical disc device:  
         [0013]     Japanese Patent Laid-Open No. 11-328857  
       SUMMARY OF THE INVENTION  
       [0014]     According to one aspect of the present invention, there is provided a playback device including 
        a drive unit which rotates a disc-like recording medium having a first recording area with first data recorded and a second recording area with second data recorded different from the first data and needing to be rotated at a predetermined rotational speed to play back the second data from the second recording area,     a playback unit which plays back data from the disc-like recording medium,     a first detection unit which detects a first reference signal serving as a reference for calculating the rotational speed of the disc-like recording medium from data played back from the first recording area,     a second detection unit which detects a second reference signal serving as a reference for calculating the rotational speed of the disc-like recording medium from data played back from the second recording area,     a selection unit which selects and outputs one of the first and second reference signals output from the first and second detection units,     a rotational speed control unit which controls a rotational speed of the drive unit on the basis of the one of the first and second reference signals, and     a control unit which causes the rotational speed control unit to control the rotational speed of the drive unit on the basis of the first reference signal such that the rotational speed of the drive unit becomes almost equal to a rotational speed with which the second data can be played back from the second recording area, by causing the playback unit to move to the first recording area of the disc-like recording medium and causing the selection unit to select the first reference signal, and then causes the rotational speed control unit to control the rotational speed of the drive unit on the basis of the second reference signal by causing the playback unit to move to the second recording area and causing the selection unit to select the second reference signal.        
 
         [0022]     According to one aspect of the present invention, there is provided a playback device including 
        a drive unit which rotates a disc-like recording medium having a first recording area with first data recorded and a second recording area with second data recorded different from the first data and needing to be rotated at a predetermined rotational speed to play back the second data from the second recording area,     a playback unit which plays back data from the disc-like recording medium,     a detection unit which detects a reference signal serving as a reference for calculating the rotational speed of the disc-like recording medium from data played back from the second recording area,     a rotational speed control unit which controls a rotational speed of the drive unit on the basis of the reference signal, and     a control unit which causes the playback unit to move to the second recording area of the disc-like recording medium, stepwise changes the rotational speed of the drive unit by controlling operation of the rotation control unit, and, if the reference signal is supplied from the detection unit, controls the rotational speed of the drive unit on the basis of the reference signal.       
 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0028]      FIG. 1  is a block diagram showing the configuration of an optical disc device according to an embodiment of the present invention;  
         [0029]      FIG. 2  is an explanatory view showing the configuration of an optical disc in the optical disc device;  
         [0030]      FIG. 3  is a flowchart showing a rotational speed control procedure according to the embodiment of the present invention; and  
         [0031]      FIG. 4  is a flowchart showing a rotational speed control procedure according to another embodiment. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0032]     An embodiment of the present invention will be explained with reference to the drawings.  
         [0033]      FIG. 1  shows the configuration of an optical disc device  10  according to the embodiment of the present invention, and  FIG. 2  shows the configuration of an optical disc  20  used in the optical disc device  10 . As shown in  FIG. 2 , an optical disc based on, e.g., the HD DVD standard is used as the optical disc  20 . A data area  30  is formed on the outer peripheral side of the optical disc  20 , and a BCA  40  is formed on the inner peripheral side.  
         [0034]     Pits (not shown) for recording data such as video data are formed in the data area  30 . Sync patterns as synchronization signals are also recorded in the pits. Grooves, i.e., wobbles (not shown) are also formed in the data area  30  to wobble in fixed cycles. Each wobble mainly serves as a guide groove.  
         [0035]     A barcode-like pattern (not shown) is formed in the BCA  40  to radiate in the radial direction of the optical disc  20 . For example, unique identification information assigned to the optical disc  20  and copy protection information are recorded in the BCA  40 . Note that the optical disc device  10  is based on the HD DVD standard and thus configured to play back data recorded in the BCA  40  without fail at the time of playback. This configuration makes it possible to, e.g., prevent unauthorized copying.  
         [0036]     At the time of playback, the optical disc  20  is attached to a rotating shaft  50 , and the optical disc device  10  rotates the optical disc  20  together with the rotating shaft  50 , using a spindle motor  60 . At this time, the optical disc device  10  moves an optical pickup head  70  to a desired position and irradiates, e.g., pits with laser light output from the optical pickup head  70 . The optical disc device  10  receives light reflected from the pits using the optical pickup head  70  and performs predetermined signal processing for obtained electrical signals (RF signals), thereby generating video signals.  
         [0037]     At this time, a signal processing circuit  80  performs the predetermined signal processing for the electrical signals output from the optical pickup head  70 . The rotational speed of the spindle motor  60  is controlled on the basis of the processing result.  
         [0038]     As described above, the optical disc device  10  is based on the HD DVD standard and thus configured to play back data recorded in the BCA  40  without fail at the time of playback, in order to, e.g., prevent unauthorized copying.  
         [0039]     However, the HD DVD standard prescribes a rotational speed for the spindle motor  60  with which data can be played back from the BCA  40 . Even if the optical disc  20  is rotated at a rotational speed different from the prescribed rotational speed, data cannot be played back from the BCA  40 . Accordingly, the optical disc device  10  needs to rotate the optical disc  20  at the predetermined rotational speed prescribed by the HD DVD standard to play back data from the BCA  40 , unlike the case of the data area  30 .  
         [0040]     In this embodiment, when the optical disc device  10  plays back data from the BCA  40 , it first moves the optical pickup head  70  to the data area  30 . The optical disc device  10  controls the rotational speed of the spindle motor  60  such that the rotational speed of the spindle motor  60  becomes almost equal to the rotational speed which is prescribed by the HD DVD standard and with which data can be played back from the BCA  40 , by playing back data from the data area  30 .  
         [0041]     After that, the optical disc device  10  moves the optical pickup head  70  to the BCA  40 . At this time, the rotational speed of the spindle motor  60  may change slightly. In this case, the optical disc device  10  plays back the data from the BCA  40  and detects, from the played-back data, a sync pattern (a reference signal serving as a reference for calculating the rotational speed of the spindle motor  60 ) which is a unique bit pattern. With this operation, the optical disc device  10  controls the rotational speed of the spindle motor  60  such that the rotational speed of the spindle motor  60  becomes the rotational speed prescribed by the HD DVD standard.  
         [0042]     As described above, the optical disc can be stably rotated at the predetermined rotational speed by controlling the rotational speed of the spindle motor  60  with high accuracy while playing back the data from the BCA  40 . Accordingly, data readout accuracy can be increased.  
         [0043]      FIG. 3  shows a rotational speed control procedure RT 10  according to this embodiment when playing back data from the BCA  40 . In  FIG. 3 , at the time of playback, the rotational speed control procedure RT 10  starts. A controller  110  of the signal processing circuit  80  rotates the spindle motor  60  at the predetermined rotational speed by controlling the operation of a rotational speed controller  120  and maintains the rotational speed. After that, in step SP 10 , the controller  110  moves the optical pickup head  70  to the data area  30 .  
         [0044]     In this case, the optical disc device  10  irradiates, e.g., pits with laser light emitted from the optical pickup head  70  and receives light reflected from the pits using the optical pickup head  70 . The optical disc device  10  supplies obtained electrical signals to the signal processing circuit  80 . The signal processing circuit  80  inputs the electrical signals to a pit/sync detector  90  and a BCA/sync detector  100 .  
         [0045]     In step SP 20 , the controller  110  turns a switch SW to the side of the pit/sync detector  90  and causes the rotational speed controller  120  to stop maintaining the rotational speed of the spindle motor  60 . In this case, when the pit/sync detector  90  detects sync patterns recorded in the pits of the data area  30  from electrical signals output from the optical pickup head  70 , it notifies the rotational speed controller  120  that the sync patterns are detected.  
         [0046]     In step SP 30 , the rotational speed controller  120  calculates the rotational speed of the spindle motor  60  on the basis of time intervals at which the sync patterns are detected and controls the rotational speed of the spindle motor  60  based on the calculation result. With this operation, the rotational speed of the spindle motor  60  is controlled to be almost equal to the rotational speed which is prescribed by the HD DVD standard and with which data can be played back from the BCA  40 .  
         [0047]     In step SP 40 , the controller  110  controls the operation of the rotational speed controller  120 , thereby maintaining the rotational speed of the spindle motor  60 . After that, the flow shifts to step SP 50 , and the controller  110  moves the optical pickup head  70  to the BCA  40 .  
         [0048]     At this time, the rotational speed controller  120  tries to maintain the rotational speed of the spindle motor  60 . However, since the rotational speed of the spindle motor  60  is not controlled by calculating the actual rotational speed of the spindle motor  60 , the rotational speed of the spindle motor  60  may change slightly.  
         [0049]     In step SP 60 , the controller  110  turns the switch SW to the side of the BCA/sync detector  100  and causes the rotational speed controller  120  to stop maintaining the rotational speed of the spindle motor  60 . In this case, when the BCA/sync detector  100  detects sync patterns recorded in the BCA  40  from electrical signals output from the optical pickup head  70 , it notifies the rotational speed controller  120  that the sync patterns are detected.  
         [0050]     In step SP 70 , the rotational speed controller  120  calculates the rotational speed of the spindle motor  60  on the basis of time intervals at which the sync patterns are detected and controls the rotational speed of the spindle motor  60  based on the calculation result. With this operation, the rotational speed of the spindle motor  60  is controlled with high accuracy to be almost equal to the rotational speed which is prescribed by the HD DVD standard and with which data can be played back from the BCA  40 .  
         [0051]     As described above, according to this embodiment, the optical disc can be stably rotated at the fixed rotational speed when playing back the data from the BCA  40 . Accordingly, the data readout accuracy can be increased.  
         [0052]     This embodiment eliminates the need to provide an FG signal generator for the spindle motor  60  and makes it possible to correspondingly simplify the configuration of the optical disc device  10 .  
         [0053]     This embodiment also eliminates the need to provide an FG signal detector for detecting an FG signal in the signal processing circuit  80  and makes it possible to correspondingly simplify the configuration of the signal processing circuit  80 . This eliminates the need to provide an input terminal for inputting, to the signal processing circuit  80 , an FG signal output from an FG signal detector.  
         [0054]     Note that the above-described embodiment is merely an example and not intended to limit the present invention. For example, it is also possible to control the rotational speed of the spindle motor  60  by detecting anything other than a sync pattern as a reference signal for calculating the rotational speed of the spindle motor  60  when playing back the data from the BCA  40 . Examples of the reference signal include a resync pattern which is another type of synchronization pattern, a preamble indicating the start of data, and a postamble indicating the end of data.  
         [0055]     It is also possible to control the rotational speed of the spindle motor  60  by detecting not sync patterns obtained from pits but wobble signals obtained from wobbles when playing back data from the data area  30 .  
         [0056]     As the optical disc  20 , an optical disc based on a DVD standard may be used instead of an optical disc based on the HD DVD standard.  
         [0057]     When the controller  110  plays back data from the BCA  40 , it may move the optical pickup head  70  to the BCA  40  without playing back data from the data area  30 . After that, the controller  110  may try to detect sync patterns recorded in the BCA  40  while changing the rotational speed of the spindle motor  60 . The rotational speed of the spindle motor  60  may be controlled only if the detection of the sync patterns is successful. In this case, the controller  110  turns the switch SW to the side of the BCA/sync detector  100  in advance.  
         [0058]      FIG. 4  shows a rotational speed control procedure RT 20  according to another embodiment when playing back data from a BCA  40  without playing back data from a data area  30 . In  FIG. 4 , at the time of playback, the rotational speed control procedure RT 20  starts. In step SP 100 , a controller  110  of a signal processing circuit  80  rotates a spindle motor  60  at a predetermined rotational speed by controlling the operation of a rotational speed controller  120 . At the same time, the controller  110  moves an optical pickup head  70  to the BCA  40 .  
         [0059]     In step SP 110 , the rotational speed controller  120  determines whether it is notified by a BCA/sync detector  100  that sync patterns are detected. If an affirmative result is obtained in step SP 110 , the flow shifts to step SP 120 , and the rotational speed controller  120  controls the rotational speed of the spindle motor  60 . After that, the flow shifts to step SP 130 , and the procedure RT 20  ends.  
         [0060]     On the other hand, if a negative result is obtained in step SP 110 , the flow shifts to step SP 140 , and the rotational speed controller  120  determines whether a current rotational speed is equal to a predetermined upper limit. If a negative result is obtained in step SP 140 , the flow shifts to step SP 150 . In step SP 150 , the rotational speed controller  120  increases the rotational speed of the spindle motor  60  by a predetermined value, and the flow returns to step SP 110  to repeat the above-described operation. Attempts are made to detect a sync pattern while stepwise increasing the rotational speed of the spindle motor  60 .  
         [0061]     On the other hand, if an affirmative result is obtained in step SP 140 , the flow shifts to step SP 160 . In step SP 160 , the rotational speed controller  120  determines whether it is notified by the BCA/sync detector  100  that sync patterns are detected. If an affirmative result is obtained in step SP 160 , the flow shifts to step SP 120 , and the rotational speed controller  120  controls the rotational speed of the spindle motor  60 . After that, the flow shifts to step SP 130 , and the procedure RT 20  ends.  
         [0062]     On the other hand, if a negative result is obtained in step SP 160 , the flow shifts to step SP 170 . In step SP 170 , the rotational speed controller  120  determines whether the current rotational speed is equal to a predetermined lower limit. If a negative result is obtained in step SP 170 , the flow shifts to step SP 180 . In step SP 180 , the rotational speed controller  120  reduces the rotational speed of the spindle motor  60  by a predetermined value, and the flow shifts to step SP 160  to repeat the above-described operation. Attempts are made to detect a sync pattern while stepwise reducing the rotational speed.  
         [0063]     On the other hand, if an affirmative result is obtained in step SP 170 , the flow returns to step SP 110 , and the rotational speed controller  120  repeats the above-described operation. Attempts are made again to detect a sync pattern while stepwise increasing the rotational speed of the spindle motor  60 .

Technology Category: g