Abstract:
In the present invention, the processing sequence of a microprocessor for restructuring the recording parameters when changing the recording in an optical disk recording apparatus from a constant angular velocity (CAV) mode to a constant linear velocity (CLV) mode is as follows: (1) interrupt the recording process; (2) calculate a linear velocity at a point where the recording linear velocity becomes constant; (3) calculate a third recording parameter in the linear velocity by a linear interpolation based on first and second recording parameters which are corrected by test writing, replacing all the recording parameters for an outer circumference of an optical disk from a radius position where the linear velocity becomes Cx, with the third recording parameter; and (4) restart the recording with the third recording parameter as a recording condition.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to an optical disk recording apparatus, and more particularly to a recording control method for an optical disk recording apparatus capable of quickly dealing with a change in the recording system. 
   2. Description of the Related Art 
   The optical disk recording apparatus is an apparatus for recording information on an optical disk using a laser beam. Examples of the optical disk recording apparatus that are currently marketed include rewritable ones such as DVD-RAM, DVD-RW and CD-RW, as well as recordable ones such as DVD-R and CD-R. Examples of the disk recording system include a CAV (Constant Angular Velocity) system that controls the disk rotation speed to be constant, a CLV (Constant Linear Velocity) system that controls the recording linear velocity to be constant, and a PCAV (Partial Constant Angular Velocity) that uses both the CAV system and the CLV system together. 
   The CAV system is not necessary to change the disk rotation speed when seeking and capable of providing high-speed access. However, because the linear velocity becomes higher as it approaches the outer circumference of the disk, there is a disadvantage that the lower power is insufficient and the recording quality degrades. The CLV system controls the disk rotation so that the linear velocity is kept constant, which makes it possible to realize the maximum recording capacity without any waste occurring in the recording area. Meanwhile, the rotation speed substantially increases when recording on the inner circumference of the disk, so that the apparatus vibrates and the recording quality degrades. In the worst case, the disk could be damaged due to centrifugal force. The PCAV system is a system that employs the CAV system (i.e., CAV mode of operation) as long as the linear velocity does not exceed the maximum linear velocity from the inner circumference of the optical disk toward the outer circumference thereof, and that switches from the CAV mode to the CLV system (i.e., CLV mode of operation) when the linear velocity exceeds the maximum linear velocity at the outer circumference of the optical disk in order to realize high-speed access and large recording capacity. 
   In Japanese Patent Publication Laid-Open No. 2003-141732 there is described a control method in a PCAV system to monitor the recording state in real time and switch the rotation system at a time when the recording state deteriorates, from the CAV mode to the CLV mode regardless of the laser capability. 
   SUMMARY OF THE INVENTION 
   In the above described JP-A-2003-141732, there is a description that a servo circuit is controlled so as to keep the linear velocity immediately before switching, when the rotation system of the disk is switched from the CAV mode to the CLV mode in the case where the linear velocity exceeds the maximum linear velocity after the start of recording. However, there is no description on restructuring of the recording parameters such as recording power and recording pulse width. Furthermore, there is also no description on the linear velocity, recording power and a recording pulse width for switching from the CAV mode to the CLV mode upon detecting that the recording state has deteriorated. Generally, in the event of a change in the rotation speed of the optical disk during recording in the CAV mode, it is necessary to perform again learning of a group of recording parameters at a plurality of radius positions to restructure the recording parameters. However, it is also necessary to interrupt the recording process until the recording parameters are restructured, and a prolonged interruption time until the resumption of recording has a significantly negative impact on the characteristics of the optical disk recording apparatus. Thus, it is an important to solve the problem of how to shorten the record interruption time when switching from the CAV mode to the CLV mode of operation. 
   It is an object of the present invention to reduce the interruption time until the resumption of recording, in the event of a change in the rotation speed of an optical disk during recording in the CAV mode, by quickly derive the recording parameter corresponding to the rotation speed after the change. 
   In order to achieve the above object, a recording control method for an optical disk recording apparatus according to an embodiment of the invention includes the steps of: 
   reproducing control data from a control data area of the optical disk, and extracting recording parameters from the control data to create a recording parameter table; 
   performing test writing at two or more radius positions of the optical disk to correct the recording parameters in the recording parameter table; 
   performing recording, in a CAV mode, from an inner circumference of the optical disk toward an outer circumference thereof based on the corrected recording parameters; 
   interrupting the recording process when a change to a CLV mode occurs during recording in the CAV mode, and calculating linear velocity at the point of the change; 
   calculating the recording parameter in the calculated linear velocity based on the corrected recording parameters; 
   replacing the corrected recording parameters for the outer circumference side from a radius position at the point of the change, with the calculated recording parameter; and 
   restarting recording based on the replaced recording parameter. 
   Further, in order to achieve the above object, an optical disk recording apparatus according to an embodiment of the present invention has: 
   a spindle motor for rotating an inserted optical disk; 
   an optical head for recording data by irradiating a laser beam onto the optical disk, detecting reflected light from the optical disk, and outputting a servo signal and a reproduction signal; 
   a servo circuit for inputting the servo signal from the optical head to control a position of the optical head; 
   a signal reproduction block for inputting the reproduction signal and outputting demodulated data and an address signal; and 
   a microprocessor for inputting the outputs of the signal reproduction block to control the respective sections described above, 
   under the control of the microprocessor, the optical disk recording apparatus reproducing the control data from the control data area of the optical disk to create a recording parameter table, performing test writing at two or more radius positions of the optical disk to correct the recording parameters in the recording parameter table, performing recording in the CAV mode from an inner circumference of the optical disk toward an outer circumference thereof based on the corrected recording parameters, interrupting the recording process when a change from the CAV mode to the CLV mode occurs during recording to calculate a linear velocity at the point of the change, calculating the recording parameter at the calculated linear velocity based on the corrected recording parameters, replacing the corrected recording parameters for the outer circumference of the optical disk from the radius position at the point of the change with the calculated recording parameter, and then restarting recording based on the replaced recording parameter. 
   According to the invention, even in the event of a change in the rotation speed of the optical disk during recording in the CAV mode, it is possible to quickly derive the recording parameter corresponding to the rotation speed after the change, so that the interruption time until the resumption of recording can be reduced. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a diagram for illustrating a recording control method according to an embodiment of the invention, which shows the relation of the disk radius position, the recording linear velocity, and the disk rotation speed; 
       FIG. 2  is a diagram for illustrating a recording control method according to an embodiment of the invention, which shows the relation between the disk radius position and the recording parameter; 
       FIG. 3  is a schematic block diagram of an optical disk recording apparatus to which the recording control method according to an embodiment of the invention is applied; 
       FIG. 4  is a perspective view of an optical disk which shows a recording area and a control area of the optical disk; 
       FIG. 5  is a block diagram of a recording parameter table corrected by performing test writing; 
       FIG. 6  is a block diagram of a restructured recording parameter table according to an embodiment of the invention; and 
       FIG. 7  is a diagram of the recording waveform of an optical disk (DVD-RAM) according to an embodiment of the invention. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   The general configuration of an optical disk recording apparatus will be described with reference to  FIG. 3 . An optical disk recording apparatus  1  has a spindle motor (motor)  12 , where an optical disk  11  loaded to a rotary shaft of the spindle motor  12  is rotated by the spindle motor  12 . The optical disk recording apparatus  1  further has an optical head  2  which is provided with a laser light source  25 , a collimating lens  24 , a beam splitter  28 , an objective lens  23 , a hologram element  29 , a servo detector  26 , and a signal detector  27 . A laser beam projected from the laser light source  25  is made a substantially parallel optical beam  22  through the collimating lens  24 . The optical beam  22  is irradiated on the optical disk  11  through the objective lens  23  to form a spot  21 . A portion of the optical beam  22  reflected from the optical disk  11  is guided to the servo detector  26  and to the signal detector  27  through the beam splitter  28 , the hologram element  29  and the like. 
   Signals from the respective detectors are subjected to a subtraction process to be servo signals such as a tracking error signal and a focus error signal, and the servo signals are input to the servo circuit  3 . The servo circuit  3  controls the positions of an objective lens actuator  31  and the entire optical head  2  via an automatic position controller  4  based on the obtained tracking error signal and the focus error signal, and places the position of an optical spot  21  in a target recording/reproduction area. An additional signal of the signal detector  27  is input to a signal reproduction block  5 . The input signal is subjected to processes of filtering, frequency equalization, and then digitization by the signal processing circuit  52 . The digitized digital signal is processed by an address detection circuit  54  and a demodulation circuit  56 . A microprocessor  6  calculates the position of the optical spot  21  on the optical disk based on the address signal detected by the address detection circuit  54 , and places the optical head  2  and the optical spot  21  in a target recording unit area (sector) by controlling the automatic position controller  4 . 
   When an instruction from a higher-level device to the microprocessor (controller)  6  is a recording, the microprocessor  6  receives the recorded data from the higher-level device and stores the data in a memory  7 , while placing the optical spot  21  in a target recording area on the optical disk  11  by controlling the automatic position controller  4 . The microprocessor  6  confirms that the optical spot  21  is normally placed in the target recording area by the address signal from the signal reproduction block  5 , and then records the data within the memory  7  to the target memory area on the optical disk  11  by controlling a laser driver  8  and other related equipment. 
     FIG. 4  schematically shows the recording area of the optical disk  11 . A user data area  110  is defined between an innermost circumference  111  and an outermost circumference  112 . 
   A control data area  113  is provided in a lead-in area further inside from the user area on the inner circumference side. In the control data area  113  there are recorded such parameters as the recording linear velocity, recording power and recording pulse width for the innermost circumference  111  and outermost circumference  112  of the user data area  110 . Further, in the control data area  113  there are also recorded the disk type, disk size, recording density, address information of the recording area and the like, in addition to the above described information on the linear velocity. 
   The optical disk  11  is inserted into the optical disk recording apparatus  1 . Then, under the control of the microprocessor  6 , the apparatus  1  reads the medium control information (control data) previously stored in the control data area  113  on the optical disk  11 . The optical disk recording apparatus  1  extracts from the control data the recording parameters, such as, the recording linear velocity, recording power and recording pulse width of the optical disk  11 , and creates a recording parameter table in the memory  7 . The apparatus  1  controls the rotation speed of the optical disk  11  based on the extracted recording linear velocity to perform test writing on the innermost circumference  111  and outermost circumference  112  of the optical disk  11 . 
   Further, under the control of the microprocessor  6 , the optical disk recording apparatus  1  reproduces the area where the test writing has been performed, checks the quality of the recording signal based on the reproduction signal from the signal reproduction block  5 , calculates the optimum linear velocity and recording power, and then corrects the recording parameter table created in the memory  7 .  FIG. 5  shows an example of the recording parameter table where the recording parameters associated with the corrected linear velocity are described. RBP represents the relative byte position. The linear velocity is defined in RBP=0, where, for example, the linear velocities at the innermost circumference  111  and the outermost circumference  112  of an optical disk  11 , shown in  FIG. 4 , are described. The recording power is defined in RBP=1, where, for example, the recording powers at the innermost circumference  111  and the outermost circumference  112  are described. The pulse edge position (front edge) is defined in RBP=2, where, for example, the pulse edge position information of the front edges at the innermost circumference  111  and the outermost circumference  112  are described. The pulse edge position (rear edge) is defined in RBP=3, where, for example, the pulse edge position information of the rear edges at the innermost circumference  111  and the outermost circumference  112  is described. 
     FIG. 7  shows a diagram of a write strategy, one of the recording parameters of the DVD-RAM which is a type of the rewritable optical disk. The write strategy is shown for a recording of 11T mark, where T is a recording clock period. As shown in  FIG. 7 , the write strategy of the DVD-RAM includes a first pulse that is defined by TSFP, TEFP and TFP, a repeating pulse (also referred to as a multi-pulse) that is defined by TMP, and a last pulse that is defined by TSLP, TELP and TLP. Incidentally, there are two laser power levels, one having 2 values and the other having 3 values, and in this example there is shown the laser power level having 2 values, PW 1  and PW 2 . 
   Next, the recording control method in the embodiment will be described with reference to  FIGS. 1 and 2 . In  FIG. 1 , the horizontal axis represents the disk radius position, the left vertical axis represents the recording linear velocity, and the right vertical axis represents the disk rotation speed. Reference numeral  101  in  FIG. 1  denotes the relation between the disk radius position and the recording linear velocity (hereinafter referred to as the profile) when performing recording in the CAV mode from the innermost circumference  111  of the optical disk  11  toward the outermost circumference  112  thereof. In this example, the linear velocity at the innermost circumference  111  of the optical disk  11  is represented by Ax, and the linear velocity at the outermost circumference  112  thereof is represented by Bx. Reference numeral  102  denotes the relation between the disk radius position and the disk rotation speed. The rotation speed from the innermost circumference toward  111  the outermost circumference  112  of the optical disk  11  is kept constant. 
   Now, assuming that the rotation speed  102  of the optical disk  11  is changed in the PCAV system where the rotation speed becomes as shown by reference numeral  104 , due to such factors as the degradation of recording quality and the instability of servo, during the actual recording process performed under the recording conditions described in the recording parameter table shown in  FIG. 5 . In other words, this is the case where recording in the CAV mode is changed to recording in the CLV mode due to the detection of the degradation of recording quality or the instability of servo. Along with the change to the PCAV system, the recording linear velocity relative to the radius position of the optical disk  11  is changed from that represented by  101  to that represented by a broken line  103  shown in  FIG. 1 . The recording linear velocity at the change point (broken point)  105  at this time is represented by Cx. Incidentally, the degradation of recording quality can be detected by monitoring the reduction of the reproduction signal amplitude and the asymmetry of the waveform in a signal processing circuit  52 . The instability of servo can be detected by monitoring the tracking error signal and the focus error signal in the servo circuit  3 . 
     FIG. 2  shows the relation between the disk radius position and the recording parameter. Recording parameter P at the innermost circumference  111  and recording parameter Q at the outermost circumference  112  are the values corrected by the test writing described above. Recording parameter R at the broken point  105  is calculated by a linear interpolation based on the recording parameters P and Q. In the case where the recording system of the optical disk  11  is changed from the CAV mode to the CLV mode in the PCAV system as shown in  FIG. 1 , it is necessary to restructure the recording parameter table as shown in  FIG. 5 . In accordance with an embodiment, the recording parameter is quickly restructured to perform recording in the PCAV system from the current recording parameter information, rather than performing again and learning, such as, the test writing upon the restructuring of the recording parameter table. 
   The following is the processing sequence of the microprocessor  6  for reconstructing the recording parameter table. 
   (1) Interrupt the recording process. 
   (2) Calculate the linear velocity Cx at the broken point  105  where the recording linear velocity shown in  FIG. 1  becomes constant. The radius position of the broken point  105  has been calculated based on the address information from the address detection circuit  54 , so that the linear velocity Cx can be calculated by a linear interpolation based on the linear velocity Ax at the innermost circumference  111  and the linear velocity Bx at the outermost circumference  112  of the optical disk  11 . 
   (3) Calculate the recording parameter R in the linear velocity Cx by a linear interpolation  201  based on the recording parameters P and Q shown in  FIG. 2 , replacing all the recording parameters for the outer circumference side  202  from a radius position  203  where the linear velocity becomes Cx, with the recording parameter R. The reconstructed recording parameter table is shown in  FIG. 6 . 
   (4) Resume the recording with the recording parameter R as the recording condition. 
   The above described recording parameter R is the parameter at the point of time when the recording quality begins to degrade or the servo becomes unstable. Because the disk rotation speed becomes reduced from this point of time, the recording quality and the stability of servo can be assured. Incidentally, it may also be possible to calculate the recording parameter corresponding to the linear velocity slightly lower than the linear velocity Cx at the broken point  105  by the linear interpolation  201  to set it as a recording parameter for the restructuring. 
   According to the embodiment of the invention as described above, in an optical disk recording apparatus for creating a recording parameter table by performing recording parameter learning, such as, test writing at two or more radius positions, when a change in the velocity profile occurs during recording, it is possible to restructure the recording parameter table in response to the change in the velocity profile without relearning the recording parameters, so that the record interruption time can be reduced. 
   It should be noted that in the above described embodiment, the linear interpolation is employed for the derivation of the recording parameter at the disk radius position; however the invention is not limited to this method and any other suitable methods may be used. In addition, the embodiment has been described for the case where the relation between the recording parameter learning speeds Ax, Bx and the broken point speed Cx is given by Ax&lt;Cx&lt;Bx. However, with the relation given by Ax&lt;Bx&lt;Cx or Cx&lt;Ax&lt;Bx, it is also possible to calculate the recording parameter by the method such as an extrapolation based on the linear interpolation. 
   In addition, to simply the description in the above embodiment, the description has been given taking the example of applying the CAV system. However, it is also possible to apply a ZCAV (Zoned CAV) system that divides the disk into several zones in the radius direction with the disk rotation speed kept constant, where the bit rates within the zones are the same respectively and the linear velocity is the maximum at the outermost circumference. Similarly, in the event of a change in the PCAV system at the broken point, it is possible to apply a ZCLV (Zoned CLV) system where the rotation speeds are constant within each of the zones but are different among the zones.