Abstract:
An optical disk apparatus is disclosed which can suppress excessive reduction of recording speed on the inner side of a disk and that can assure quick response of accessing operation. When, at the time of access, a write or read operation is performed while returning to a second disk radial position that is located inside a first disk radial position, based on a positional relationship of the first and second disk radial positions with respect to a reference radial position, the rotation control method of the optical disk at the second disk radial position is selected out of a constant linear velocity method and a constant angular velocity method so that, if a user disk area is relatively small and located only on the inner side, writing or reading velocity on the inner side is not reduced or, if the user disk area is relatively large and located both on the inner and outer sides, writing or reading velocity on the outer side is not reduced and, at the time of access, regardless of the size of the user data area, the variation of rotation speed of a disk motor at the second disk radial position is suppressed and quick response is assured.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     The present application is related to and claims priority from Japanese Patent Application No. 2004-159272, filed May 28, 2004, and is hereby incorporated by reference for all purposes.  
       BACKGROUND OF THE INVENTION  
       [0002]     The present invention relates to an optical disk apparatus and, in particular, it relates to a method for controlling rotation speed of an optical disk when it is accessed.  
         [0003]     Examples of the related art related to the present invention include, for example, the technique set forth in Japanese Patent Laid-open No. 2002-269926. This publication describes a technique in that, in the range from the innermost position to a predetermined radial position of an optical disk, the optical disk is rotated using a constant angular velocity method and the write operation is performed according to a write clock of a frequency corresponding to the linear velocity at the write position and, in the range outside the predetermined radial position, the optical disk is rotated using a constant linear velocity method and the write operation is performed according to a write clock of a constant frequency corresponding to the linear velocity of the rotation.  
         [0004]     In the related art described above, based on the fact that the write operation is performed while the optical disk is rotated using the constant angular velocity method from the innermost position to the predetermined radial position of the optical disk, for example, even when the access point is moved further inward from a position inside the predetermined radial position, the write operation is performed while the optical disk is rotated using the constant angular velocity method. Therefore, the recording velocity on the inner side of the disk is reduced.  
       BRIEF SUMMARY OF THE INVENTION  
       [0005]     In view of the circumstances of the related art described above, it is desirable to prevent recording velocity at an inner side of an optical disk from being reduced excessively at the time of access in an optical disk apparatus and to suppress the difference of rotation speed between the inner side and the outer side so that quick response of the accessing operation can be assured.  
         [0006]     In an optical disk apparatus of the present invention, when, at the time of access, a write or read operation is performed while returning to a second disk radial position (the disk radial position to be accessed (the target)) that is located further inside a first disk radial position (the outermost disk radial position of a user data area recorded on an optical disk), if the first disk radial position is located on the outer side of the disk with respect to a reference radial position and the second disk radial position is located on the inner side of the disk with respect to the reference radial position, the rotation of the optical disk is switched from a constant linear velocity (CLV) method to a constant angular velocity (CAV) method.  
         [0007]     On the other hand, if both of the first and second disk radial positions are located at or inside the reference radial position or located at or outside the reference radial position, the optical disk is rotated still using the constant linear velocity method. As a result, the difference of rotation speed of the optical disk between the first disk radial position and the second disk radial position can be suppressed and the write and read operation can be started in a short time.  
         [0008]     According to the present invention, at the time of access in an optical disk apparatus, the need to excessively reduce the recording velocity on the inner side of the optical disk can be eliminated and the difference of rotation speed between the inner side and the outer side can be suppressed and, moreover, quick response of the access can be assured. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]     These and other features, objects and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings wherein:  
         [0010]      FIG. 1  is an exemplary block diagram of an optical disk apparatus provided as an embodiment of the present invention;  
         [0011]      FIGS. 2A  to  2 C are diagrams for describing disk rotation control when the disk is accessed in the optical disk apparatus of  FIG. 1 ; and  
         [0012]      FIG. 3  is a diagram for describing an operational procedure of the optical disk apparatus of  FIG. 1  when the disk is accessed. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     Hereinafter, a best mode for carrying out the present invention will be described with reference to the drawings.  
         [0014]      FIG. 1  shows: an optical disk  100 ; a disk motor  300  for rotatably driving the optical disk  100 ; a disk motor driving circuit  310  that acts as disk motor driving circuit for driving the disk motor  300 ; an optical pickup  200  for applying laser light to the optical disk  100  and receiving reflected laser light; a focus/tracking error signal forming circuit  210  for forming a focus error signal or a tracking error signal based on a signal reproduced from the reflected laser light in the optical pickup  200 ; a focus/tracking control circuit  220  for forming a control signal to control an objective lens (not shown) in the optical pickup  200  based on the output of the focus/tracking error signal forming circuit  210 ; a laser driving circuit  430  for driving a laser diode in the optical pickup  200  based on a write signal; a write signal generation circuit  420  for generating the write signal; an RF signal amplification circuit  230  for amplifying an RF signal reproduced from the reflected laser light in the optical pickup  200 ; a data demodulation circuit  250  for demodulating the amplified RF signal; a slide motor  320  for moving the optical pickup  200  in the radial direction of the optical disk  100 ; a slide motor driving circuit  330  for controllably driving the slide motor  320 ; and a microcomputer  500  that acts as control circuit for controlling the disk motor driving circuit  310 , the write signal generation circuit  420 , the focus/tracking control circuit  220  and the slide motor driving circuit  330 .  
         [0015]     In the configuration described above, user data (information) is written while the optical pickup  200  is moved from the inner side to the outer side of the optical disk  100 . At this time, the optical disk  100  is rotated by the disk motor  300  using a constant linear velocity method so that the information is recorded on a recording surface of the optical disk  100  at a constant recording velocity. The microcomputer  500  allows the disk motor  300  to rotate at a given speed via the disk motor driving circuit  310 .  
         [0016]     At the time of access, a write or read operation is performed while returning from a first disk radial position of the optical disk  100  on which the information is recorded as described above (the outermost disk radial position of the user data area recorded on the optical disk) to a second disk radial position that is located further inside the first disk radial position (the disk radial position to be accessed (the target)). In other words, the write or read operation is performed while moving the optical pickup  200  from the first disk radial position to the second disk radial position. In this case, the microcomputer  500  determines whether the first and second disk radial positions are located on the outer or inner side of the disk with respect to a predetermined reference radial position. As a result of the determination, when the first disk radial position is located on the outer side of the disk with respect to the reference radial position and the second radial position is located on the inner side of the disk with respect to the reference radial position, the microcomputer  500  controls the disk motor driving circuit  310  to switch the rotation control method of the optical disk  100  by the disk motor  300  from the constant linear velocity method to a constant angular velocity method.  
         [0017]     On the other hand, as a result of the determination, when both of the first and second disk radial positions are located at or inside the reference radial position or located at or outside the reference radial position, the microcomputer  500  does not switch the rotation control method of the optical disk  100  to the constant angular velocity method but still allows the optical disk to rotate using the constant linear velocity method.  
         [0018]     When the control state is switched to the constant angular velocity method as a result of the determination, the rotation speed of the optical disk  100  according to the constant angular velocity method, to which the control state is switched, is set to a predetermined value. In the state in which the optical pickup  200  is moved to the second radial position and the optical disk  100  is rotating using the constant angular velocity or constant linear velocity method, the focus and tracking of the objective lens in the optical pickup  200  is controlled by the microcomputer  500  via the focus/tracking control circuit  220  and an actuator (not shown) and, in such controlled state, the write or read operation is started.  
         [0019]     As described above, by suppressing the difference of the rotation speed (angular speed) of the optical disk  100  between the first disk radial position and the second disk radial position or, in other words, by suppressing the difference of the rotation speed (angular speed) of the disk motor  300  between the two disk radial positions, the write or read operation at the time of access can be started in a short time and, thus, quick response of the accessing operation can be assured. The microcomputer  500  determines the first and second disk radial positions using radial positional information about the first and second disk radial positions such as an amount of written information at the first and second disk radial positions and information about the rotation speed of the disk motor or optical disk. Here, the reference radial position mentioned above is set to an appropriate value in advance based on the conditions of the servo system such as torque characteristics of the disk motor  300 , the inertia of the body of rotation and the like.  
         [0020]     Hereinafter, the elements of  FIG. 1  used in the description of  FIGS. 2 and 3  are denoted by the same reference numerals as those in  FIG. 1 .  
         [0021]      FIGS. 2A  to  2 C are diagrams for describing disk rotation control when the disk is accessed in the optical disk apparatus of  FIG. 1 .  FIGS. 2A  to  2 C illustrate the case when the write operation is performed through the accessing operation.  FIG. 2A  is a radial cross-sectional view of the optical disk  100 ,  FIG. 2B  is a diagram showing a relationship between the disk radial position where the data is written and the rotation speed of the optical disk  100  (disk rotation speed), and  FIG. 2C  is a diagram showing a relationship between the disk radial position where the data is written and the recording velocity.  
         [0022]     In  FIGS. 2A  to  2 C, r i  designates the innermost disk radial position of a user data recording area of the optical disk  100 . r o  designates the outermost disk radial position of the user data recording area. P designates the reference radial position. A 1  shows characteristics of the disk rotation speed in the case of 5× speed recording using the constant linear velocity method (CLV recording). B 1  shows characteristics of the disk rotation speed in the case of recording with the 3× speed rotation using the constant angular velocity method (CAV recording). A 2  shows characteristics of the recording velocity in the case of the 5× speed recording using the constant linear velocity method (CLV recording). B 2  shows characteristics of the recording velocity in the case of recording with 3× speed rotation using the constant angular velocity method (CAV recording). α designates the first disk radial position on the outer side of the disk with respect to the reference radial position P. α′ designates the first disk radial position on the inner side of the disk with respect to the reference radial position P. β designates the second disk radial position on the inner side of the disk with respect to the reference radial position P. β′ designates the second disk radial position on the outer side of the disk with respect to the reference radial position P.  
         [0023]     The user data (information) is initially recorded while moving the optical pickup  200  from the innermost disk radial position r i  of the optical disk  100  toward the outermost disk radial position r o . At this time, the optical disk  100  rotates at the 5× speed using the constant linear velocity method. When the data is recorded from the innermost disk radial position r i  to the outermost disk radial position r o , the disk rotation speed is gradually reduced as the disk radial position where the data is written is moved toward the outer side of the disk (the characteristics A 1 ) while the recording velocity remains constant regardless of the disk radial position (the characteristics A 2 ).  
         [0024]     When, at the time of access, the write or read operation is performed while returning from the first disk radial position α′ on the inner side of the disk with respect to the reference radial position P to the second disk radial position β further inside the first disk radial position α′, the microcomputer  500  determines that both of the first radial position α′ and the second disk radial position β are located on the inner side of the disk with respect to the reference radial position P. As a result of the determination, the microcomputer  500  controls the disk motor driving circuit  310  so that the optical disk  100  continues to rotate at the 5× speed using the constant linear velocity method. At the 5× speed using the constant linear velocity method, the disk rotation speed at the second disk radial position β is ω 4 ′ and the recording velocity remains to be v 1  without any change. There is little difference (ω 4 ′−ω 3 ) between the disk rotation speed ω 4 ′ and the disk rotation speed ω 3  at the first disk radial position α′. Therefore, in this case, the disk motor  300  has a short servo pull-in time and, at the second disk radial position β, the write operation can be started quickly after the focus/tracking control.  
         [0025]     Further, when, at the time of access, the write or read operation is performed while returning from the first disk radial position α to the second disk radial position β′ on the outer side of the disk with respect to the reference radial position P, the microcomputer  500  determines that the first disk radial position α is located on the outer side of the disk with respect to the reference radial position P and the second disk radial position β′ is also located on the outer side of the disk with respect to the reference radial position P. As a result of the determination, the microcomputer  500  controls the disk motor driving circuit  310  so that the rotation control method of the optical disk  100  is not switched to the 3× speed constant angular velocity method but the optical disk  100  continues to rotate at the 5× speed using the constant linear velocity method. At the 5× speed using the constant linear velocity method, the disk rotation speed at the second disk radial position β′ is ω 2  and the recording velocity remains to be v 1  without any change. There is little difference ((ω 2 −ω 1 ) between the disk rotation speed ω 2  and the disk rotation speed ω 1  at the first disk radial position α. Therefore, also in this case, the disk motor  300  has a short servo pull-in time and, at the second disk radial position β′, the write operation can be started quickly after the focus/tracking control.  
         [0026]     Still further, when, at the time of access, the write or read operation is performed while returning from the first disk radial position α on the outer side of the disk with respect to the reference radial position P to the second disk radial position β on the inner side of the disk with respect to the reference radial position P, the microcomputer  500  determines that the first disk radial position α is located on the outer side of the disk with respect to the reference radial position P and the second disk radial position β is located on the inner side of the disk with respect to the reference radial position P. As a result of the determination, the microcomputer  500  controls the disk motor driving circuit  310  to switch the rotation control method of the optical disk  100  to the 3× speed constant angular velocity method. At the 3× speed using the constant angular velocity method after the switching, the disk rotation speed is constant regardless of the disk radial position (the characteristics B 1 ) and the recording velocity is increased proportional to the outward movement of the disk radial position (the characteristics B 2 ).  
         [0027]     As a result of the switching to the 3× speed constant angular velocity method, at the second disk radial position β, the disk rotation speed is ω 4  and the recording velocity is v 4 . There is little difference (ω 4 −ω 1 ) between the disk rotation speed ω 4  at the second disk radial position β after switching the rotation control method and the disk rotation speed ω 1  at the first disk radial position α before switching the rotation control method. Therefore, the disk motor  300  has a short servo pull-in time and, at the second disk radial position β, the write operation can be started quickly after the focus/tracking control. In this connection, when the rotation control method of the optical disk  100  is switched to the 3× speed constant angular velocity method, the microcomputer  500  controls the write signal generation circuit  420  to adjust the frequency of the write clock so as to assure the recording velocity v 1  of the 5× speed constant linear velocity method at the reference radial position P.  
         [0028]     Though the disk rotation control when the write operation is performed at the time of access is described above with reference to  FIGS. 2A  to  2 C, it is to be noted that the disk rotation control when the read operation is performed at the time of access is basically similar to that described above.  
         [0029]      FIG. 3  is a diagram for describing an operational procedure of the optical disk apparatus of  FIG. 1  when the disk is accessed.  
         [0030]     In  FIG. 3 ,  
         [0031]     (1) First, the microcomputer  500  issues an instruction signal so that the optical disk apparatus starts accessing operation (step S 301 );  
         [0032]     (2) The microcomputer  500  detects the current disk radial position of the optical pickup  200  or the first disk radial position and the disk radial position to which the optical pickup  200  moves for accessing or the second disk radial position (step S 302 );  
         [0033]     (3) The microcomputer  500  compares information about the both detected disk radial positions with information about a predetermined reference radial position and determines the positional relationship of the both disk radial positions with respect to the reference radial position (step S 303 );  
         [0034]     (4) As a result of the determination, when both of the first disk radial position and the second disk radial position are located at or inside the reference radial position or located at or outside the reference radial position, the microcomputer  500  does not switch the rotation control method of the optical disk  100  but still allows the optical disk  100  to rotate in the current constant linear velocity method (step S 305 );  
         [0035]     On the other hand, as a result of the determination, when the first disk radial position is located on the outer side of the disk with respect to the reference radial position and the second disk radial position is located on the inner side of the disk with respect to the reference radial position, the rotation control method of the optical disk  100  is switched from the current constant linear velocity method to the constant angular velocity method (step S 304 );  
         [0036]     (5) When the rotation control method of the optical disk  100  is set to the constant angular velocity method in step S 304  above, the optical pickup  200  is moved toward the second disk radial position of the optical disk  100  and the optical disk  100  is rotated using the constant angular velocity method (step S 306 );  
         [0037]     On the other hand, when the rotation control method of the optical disk  100  is set to the constant linear velocity method in step S 305  above, the optical pickup  200  is moved toward the second disk radial position of the optical disk  100  and the optical disk  100  is rotated still using the constant linear velocity method (step S 306 );  
         [0038]     (6) The focus/tracking control of the objective lens in the optical pickup  200  is performed (step S 307 ); and  
         [0039]     (7) The write or read operation is started at the second disk radial position (step S 308 ).  
         [0040]     According to the embodiment of the present invention described above, the need to excessively reduce the recording velocity on the inner side of the optical disk can be eliminated and the difference of rotation speed between the inner side and the outer side can be suppressed.