Patent Publication Number: US-7719935-B2

Title: Information storage medium having multiple information storage layers with optimal power control area, and recording apparatus to record data with respect to the information storage medium

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
   This application is a continuation of U.S. patent application Ser. No. 11/856,337 filed on Sep. 17, 2007, now U.S. Pat. No. 7,496,012, which is a continuation of U.S. patent application No. 10/875,794 filed on Jun. 25, 2004, now U.S. Pat. No. 7,286,454, which claims the benefit of Korean Patent Application No. 2003- 43573 filed on Jun. 30, 2003 in the Korean intellectual Property Office, the disclosures of which are incorporated herein by reference in their entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to recordable information storage media, and more particularly, to an information storage medium having a plurality of information storage layers, by which an area of the information storage layers can be efficiently used while minimizing an influence of an optimal power control (OPC) process executed in an OPC area, included in each of information storage layers, upon other information storage layers. 
   2. Description of the Related Art 
   General information storage media are widely used as information recording media of optical pickup apparatuses for recording/reproducing data in a non-contact way. Optical disks are used as the information storage medium and classified as compact disks (CDs) or digital versatile disks (DVDs) according to their information storage capacity. Examples of recordable, erasable, and reproducible optical disks are 650 MB CD-R, CD-RW, 4.7 GB DVD+RW, and the like. Furthermore, high definition-DVD (HD-DVD) having a recording capacity of 25 GB or greater are under development. 
   As described above, information storage media have been developed to have a greater recording capacity. The recording capacity of an information storage medium can be increased in two representative ways of: 1) reducing the wavelength of a recording beam emitted from a light source; and 2) increasing the numerical aperture of an objective lens. In addition, there is a way of forming a plurality of information storage layers. 
     FIGS. 1A and 1B  schematically illustrate a dual-layered information storage medium having first and second information storage layers L 0  and L 1 . The first and second information storage layers L 0  and L 1  include first and second optimal power control (OPC) areas  111  and  121 , respectively, for obtaining optimal writing power and first and second defect management area (DMAs)  115  and  125 , respectively. The first and second OPC areas  111  and  121  face each other (i.e., the OPC areas are at a common radius relative to an inner or outer boundary of the information storage medium). 
   Data is recorded in the first and second OPC areas  111  and  121  using various levels of writing power to find the optimum writing power. Hence, data may be recorded with a higher level of power than the optimum writing power. Table 1 shows variations in the jitter characteristics of each of the first and second information storage layers L 0  and L 1  when data is recorded in the OPC areas  111  and  121  with different levels of writing power. 
   
     
       
         
             
             
             
           
             
                 
               TABLE 1 
             
           
          
             
                 
                 
             
             
                 
                 
               Writing power about 20% 
             
             
                 
                 
               higher than normal writing 
             
             
                 
               Normal writing power 
               power 
             
          
         
         
             
             
             
             
             
             
             
          
             
               L0 
               Writing 
               Unwritten 
               Writing 
               Written 
               Writing 
               Written 
             
             
               L1 
               Unwritten 
               Writing 
               Written 
               Writing 
               Written 
               Writing 
             
             
                 
             
          
         
         
             
             
             
             
             
             
             
             
          
             
               Jitter 
               L0 
               5.9% 
                 
               6.0% 
               5.8% 
                 
               5.9% → 6.4% 
             
             
                 
               L1 
                 
               6.3% 
               6.2% 
               6.3% 
               6.2% → 6.3% 
             
             
               Writing 
               L0 
               6.4 
                 
               6.3 
               6.3 
               7.5 
               6.4 
             
             
               Power 
               L1 
                 
               6.0 
               6.0 
               6.2 
               6.0 
               7.2 
             
             
                 
             
          
         
       
     
   
   According to Table 1, if data is recorded with normal writing power, the jitter characteristics of the first or second information storage layer L 0  or L 1  keep constant. On the other hand, if data is recorded with writing power about 20% higher than the normal writing power, the jitter characteristics of the OPC area of the first or second information storage layer L 0  or L 1  in which data has already been recorded are degraded. If data is recorded on one of the first and second information storage layers L 0  and L 1  with writing power more than 20% higher than the normal writing power, it can be expected that the jitter characteristics of the other information storage layer may be further degraded. 
   Hence, if the first and second OPC areas  111  and  121  of the first and second information storage layers L 0  and L 1  exist within an equal radius as shown in  FIGS. 1A and 1B , one of them may not be usable. 
   The recording status of one of the first and second OPC areas  111  and  121  may affect the recording characteristics of the other OPC area. For example, as shown in  FIG. 1B , if data has been recorded on a part  111   a  of the first OPC area  111  and no data has been recorded on the residual area  111   b  thereof, the recording property of a part of the second OPC area  121  which corresponds to the occupied part  111   a  of the first OPC area  111  is different from that of a part of the second OPC area  121  which corresponds to the unoccupied part  111   b  of the first OPC area  111 . In other words, since the transmittance of a laser with respect to the occupied part  111   a  of the first OPC area  111  is different from the transmittance of a laser with respect to the unoccupied part  111   b  thereof, the recording property of the second OPC area  121  may be irregular over the area. 
   As described above, if the first and second OPC areas are disposed within an equal radius, they may not properly function. 
   SUMMARY OF THE INVENTION 
   According to an aspect of the present invention, there is provided an information storage medium having a plurality of information storage layers, by which an area of the information storage layers can be efficiently used while minimizing an influence of optimal power control (OPC) executed in an OPC area included in each of information storage layers upon other information storage layers. 
   According to an aspect of the present invention, there is provided an information storage medium having a plurality of information storage layers, each of which includes an optimal power control area for obtaining an optimal recording condition, wherein the optimal power control areas in odd-numbered and even-numbered information storage layers are disposed within different radiuses of the information storage medium and the size of an actually usable area of an optimal power control area in each of the information storage layers varies depending on use circumstances of each of the information storage layers. 
   According to another aspect of the present invention, there is provided an information storage medium having a plurality of information storage layers, each of which includes an optimal power control area for obtaining an optimal recording condition, wherein the optimal power control areas in odd-numbered and even-numbered information storage layers are disposed within different radiuses of the information storage medium and one of the odd-numbered and even-numbered information storage layers includes a usable area for a predetermined purpose that faces the optimal power control area of the other information storage layer. 
   Additional aspects and/or advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and/or other aspects and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings of which: 
       FIGS. 1A and 1B  are views illustrating an influence of an optimal power control (OPC) area upon an area other than the OPC area in a conventional dual-layered information storage medium; 
       FIG. 2  illustrates a layout of a data area of a dual-layered information storage medium according to an embodiment of the present invention; 
       FIGS. 3A and 3B  illustrate a layout of a data area of a dual-layered information storage medium according to another embodiment of the present invention; 
       FIGS. 4A and 4B  illustrate a layout of a data area of a dual-layered information storage medium according to another embodiment of the present invention; 
       FIGS. 5A through 5D  illustrate a layout of a data area of a dual-layered information storage medium according to another embodiment of the present invention; 
       FIG. 6  illustrates a layout of a data area of a dual-layered information storage medium according to an embodiment of the present invention; 
       FIG. 7  illustrates a layout of a data area of a dual-layered information storage medium according to another embodiment of the present invention; 
       FIG. 8  is a block diagram of a recording and/or reproducing apparatus according to an embodiment of the present invention; and 
       FIG. 9  is a more detailed block diagram of the optical recording and/or reproducing apparatus of  FIG. 8 . 
   

   DETAILED DESCRIPTION OF THE EMBODIMENTS 
   Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures. 
   Referring to  FIG. 2 , an information storage medium according to an embodiment of the present invention includes at least two information storage layers L 0  and L 1 . Each of the information storage layers L 0 , L 1  includes an optimal power control (OPC) area  211 ,  223  for obtaining optimal power and a reserved area  213 ,  221 . The OPC areas  211 ,  223  of the information storage layers L 0 , L 1  are disposed within different radii such as not to face each other. Although not shown, each of the information storage layers may include a map area adjacent to the OPC area  211 ,  223 . 
   The information storage medium shown in  FIG. 2  includes first and second information storage layers L 0  and L 1 . The first information storage layer L 0  includes a first OPC area  211 , a first reserved area  213 , and a first disk information (DI) area  215 . The second information storage layer L 1  includes a second reserved area  221 , a second OPC area  223 , and a second DI area  225 . The first and second DI areas  215  and  225  store data that is updated upon every data recording, such as, an address of a used part of an OPC area, information about a status of an information storage layer, and the like. Examples of the information about a status of an information storage layer include a recording mode, and an address recorded last according to a recording mode. 
   The first and second OPC areas  211  and  223  in the information storage layers L 0  and L 1  are disposed within different radii of the information storage medium such that the first and second OPC areas  211  and  223  do not face each other. More specifically, the second reserved area  221  is disposed in an area of the second information storage layer L 1  opposite to the first OPC area  211  of the first information storage layer L 0 , and the first reserved area  213  is disposed in an area of the first information storage layer L 0  opposite to the second OPC area  223  of the second information storage layer L 1 . 
   The first and second DI areas  215  and  225  of the first and second information storage layers L 0  and L 1 , respectively, are disposed within an identical radius of the information storage medium. Defect management areas (DMAs) may be used instead of or in addition to the DI areas  215  and  225 . 
     FIGS. 3A and 3B  illustrate an information storage medium according to another embodiment of the present invention, in which the first information storage layer L 0  includes a first OPC area  311 , a first reserved area  313 , and a first disk management area (DMA)  315 , and the second information storage layer L 1  includes a second reserved area  321 , a second OPC area  323 , and a second DMA  325 . 
   Referring to  FIGS. 3A and 3B , directions of data recording in each OPC area  311 ,  323  and a reserved area  313 ,  321  of each information storage layer L 0 , L 1 , (i.e., directions of the use of the OPC area  311 ,  323  and the reserved area  313 ,  321 ) are identical. In other words, while data is recorded in an OPC area  311 ,  323  and a reserved area  313 ,  321  of each information storage layer L 0 , L 1  in an identical direction, data is recorded in facing areas of different information storage layers L 0 , L 1  in opposite directions. That is, the facing areas of different information storage layers L 0 , L 1  are used in opposite directions so that they are not used together upon data recording. 
   In  FIG. 3A , regardless of a track spiral direction of the information storage medium, data is recorded in the first OPC area  311  and the first reserved area  313  of the first information storage layer L 0  in an identical direction from an inner boundary to an outer boundary of the information storage medium. In other words, the first OPC area  311  and the first reserved area  313  are used in the identical direction from the inner boundary to the outer boundary of the information storage medium. Data is recorded in the second reserved area  321  and the second OPC area  323  of the second information storage layer L 1  in an identical direction from the outer boundary to the inner boundary of the information storage medium. In other words, the second reserved area  321  and the second OPC area  323  are used in the identical direction from the outer boundary to the inner boundary of the information storage medium. Thus, the facing OPC and reserved areas of the first and second storage layers L 0  and L 1  are used in opposite directions. 
   In  FIG. 3B , regardless of the track spiral direction of the information storage medium, data is recorded in the first OPC area  311  and the first reserved area  313  of the first information storage layer L 0  in the identical direction from the outer boundary to the inner boundary of the information storage medium. In other words, the first OPC area  311  and the first reserved area  313  are used in the identical direction from the outer boundary to the inner boundary of the information storage medium. Data is recorded in the second reserved area  321  and the second OPC area  323  of the second information storage layer L 1  in the identical direction from the inner boundary to the outer boundary of the information storage medium. In other words, the second reserved area  321  and the second OPC area  323  are used in the identical direction from the inner boundary to the outer boundary of the information storage medium, but opposite the direction of use of the first OPC area  311  and the first reserved area  313 . 
     FIGS. 4A and 4B  illustrate an information storage medium according to another embodiment of the present invention, in which the first information storage layer L 0  includes a first OPC area  411 , a first reserved area  413 , and a first DMA  415 , and the second information storage layer L 1  includes a second reserved area  421 , a second OPC area  423 , and a second DMA  425 . 
   Referring to  FIGS. 4A and 4B , directions of data recording in an OPC area  411 ,  423  and a reserved area  413 ,  421  of each information storage layer L 0 , L 1  (i.e., directions of the use of the OPC area  411 ,  423  and the reserved area  413 ,  421 ) are opposite. In other words, while data is recorded in an OPC area  411 ,  423  and a reserved area  413 ,  421  of each information storage layer L 0 , L 1  in opposite directions, data is recorded in facing areas of different information storage layers in opposite directions. That is, the facing areas of different information storage layers are used in opposite directions so that they are not used together upon data recording. 
   In  FIG. 4A , regardless of the track spiral direction of the information storage medium of  FIG. 2 , directions of data recording in a first OPC area  411  and a first reserved area  413  of a first information storage layer L 0  are opposite. That is, directions of the use of the first OPC area  411  and the first reserved area  413  are from an inner boundary to an outer boundary of the information storage medium and from the outer boundary to the inner boundary, respectively. Directions of data recording in a second reserved area  421  and a second OPC area  423  of a second information storage layer L 1 , that is, directions of the use of the second reserved area  421  and the second OPC area  423 , are from the outer boundary to the inner boundary of the information storage medium and from the inner boundary to the outer boundary, respectively. 
   In  FIG. 4B , regardless of the track spiral direction of the information storage medium, directions of data recording in the first OPC area  411  and the first reserved area  413  of the first information storage layer L 0 , (i.e., directions of the use of the first OPC area  411  and the first reserved area  413 ) are from the outer boundary to the inner boundary of the information storage medium and from the inner boundary to the outer boundary, respectively. Directions of data recording in the second reserved area  421  and the second OPC area  423  of the second information storage layer L 1 , (i.e., directions of the use of the second reserved area  421  and the second OPC area  423 ) are from the inner boundary to the outer boundary of the information storage medium and from the outer boundary to the inner boundary, respectively. 
   In  FIGS. 3A and 3B  or  FIGS. 4A and 4B , it is understood that the order of the OPC area and the reserved area arranged in each of the first and second information storage layers L 0  and L 1  may be inverted according to different aspects. 
   In the information storage media of  FIGS. 3A and 3B  and  FIGS. 4A and 4B , addresses of used parts of the first OPC areas  311  and  411  and the second OPC areas  323  and  423  are recorded in the first reserved areas  313  and  413  and the second reserved areas  321  and  421 , respectively. Hence, the size of an actually usable area of an OPC area of an information storage layer varies by a used area of a reserved area of an adjacent information storage layer depending on the environments of the use of each information storage layer, for example, depending on a type of data recorded in each information storage layer or a frequency of the use of each information storage layer. 
     FIGS. 5A through 5D  illustrate an information storage medium according to another embodiment of the present invention, which includes map areas  512 ,  522  for storing addresses of used parts of the OPC areas  511 ,  523  in information storage layers L 0  and L 1  are disposed adjacent to the OPC areas  511 ,  523 . In contrast with  FIGS. 3A and 3B  and  FIGS. 4A and 4B , a reserved area allocated in each of the information storage layers L 0  and L 1  is used for a purpose other than the storage of the addresses of used parts of the OPC areas  511 ,  523 . When such a map area is disposed adjacent to an OPC area  511 ,  523  in each information storage layer as described above, a usable part of the OPC area  511 ,  523  can be rapidly identified before the OPC is performed in each information storage layer L 0 , L 1 . Thus, a time required to perform the OPC can be shortened. 
   The addresses of the OPC areas  511 ,  523  may be recorded in the map area in various forms, for example, in the form of a bitmap. The map area  512 ,  522  may be replaced by a disk information (DI) area which can store not only OPC information but also information updated upon every data recording, for example, an address finally recorded in a user area or the like. 
   In  FIGS. 5A through 5D , the first information storage layer L 0  includes a first OPC area  511 , a first map area  512 , a first reserved area  513 , and a first DMA  515 , and the second information storage layer L 1  includes a second reserved area  521 , a second map area  522 , a second OPC area  523 , and a second DMA  525 . The first and second map areas  512  and  522  are disposed within an identical radius of the information storage medium, and the first and second DMAs  515  and  525  are similarly situated on a different radius of the information storage medium. 
   Generally, the information storage media illustrated in  FIGS. 5A and 5B  are formed by further allocating the first and second map areas  512  and  522  in the information storage media of  FIGS. 3A and 3B . The information storage media illustrated in  FIGS. 5C and 5D  are formed by further allocating the first and second map areas  512  and  522  in the information storage media of  FIGS. 4A and 4B . As described above, the reserved areas  513 ,  521  illustrated in  FIGS. 5A through 5D  are not used to store data updated upon every data recording, such as, the addresses of used parts of the OPC areas  511  and  523 . 
     FIG. 6  illustrates an information storage medium according to another embodiment of the present invention. Considering the fact that characteristics of data recording in inner and outer boundaries of an information storage medium may be different, OPC areas  611 ,  631 ,  617 ,  637  are disposed in at least one of a lead-in area  610  and a lead-out area  630  which are disposed on opposite sides of a data area  620 , respectively. In the first and second information storage layers L 0  and L 1 , first and second OPC areas  611  and  617  of the lead-in area  610  and first and second OPC areas  631  and  637  of the lead-out area  630  may be disposed on both sides of third and fourth data areas  621  and  623  the data area  620  using one of the arrangements illustrated in  FIGS. 2 through 5 . 
     FIG. 7  illustrates an information storage medium according to another embodiment of the present invention. Considering the fact that degrees of influence of the OPCs executed in the first and second information storage layers L 0  and L 1  upon jitter characteristics of the first and second information storage layers L 0  and L 1 , respectively, are different, a reserved area  713  is allocated in one of the first and second information storage layers L 0  and L 1 , and a usable area  721  is allocated in the other information storage layer. 
   Referring to Table 1, the OPC in the second information storage layer L 1  affects jitter characteristics more than the OPC in the first information storage layer L 0 . Of course, if the thickness of a space layer interposed between the first and second information storage layers L 0  and L 1  is changed or a structure of each information storage layer is changed, a phenomenon opposite to the above influencing phenomenon may occur. That is, the OPC in the first information storage layer L 0  affects jitter characteristics more than the OPC in the second information storage layer L 1 . In the information storage medium of  FIG. 7 , the OPC in the second information storage layer L 1  affects jitter characteristics more than the OPC in the first information storage layer L 0 . 
   In the information storage medium of  FIG. 7 , the first information storage layer L 0  includes a first OPC area  711 , a first reserved area  713 , and a first DI area  715 , and the second information storage layer L 1  includes a usable area  721 , a second OPC area  723 , and a second DI area  725 . The usable area  721  of the second information storage layer L 1  faces the first OPC area  711  of the first information storage layer L 0 , which affects jitter characteristics less than the second OPC area  723  of the second information storage layer L 1 , and can be used to store data used for a special purpose, such as a purpose set by a user or a manufacturer. The first and second DI areas  715  and  725  are disposed within an identical radius of the information storage medium and store OPC information or information updated upon every data recording, such as, an address finally recorded in a user area or the like. The DI areas  715  and  725  may be replaced by map areas that are disposed within an identical radius of the information storage medium and that store information about the first and second OPC areas  711  and  723 . 
   Areas arranged as illustrated in  FIG. 7  can be disposed in both a lead-in area and a lead-out area or in one of a lead-in area and a lead-out area. 
     FIG. 8  is a block diagram of an optical recording and/or reproducing apparatus according to an embodiment of the present invention in which the information storage media of  FIGS. 2-7  are implemented. Referring to  FIG. 8 , the recording and/or reproducing apparatus includes a writing/reading unit  1000  and a control unit  1002 . The writing/reading unit  1000  reads from and writes to the information storage medium  130  according to commands from the control unit  1002 . Here, the information storage medium  130  includes several embodiments shown in  FIGS. 2 through 7  and the control unit  1002  controls data writing/reading operations of the writing/reading unit  1000  so as to minimize interference between a first optimal power control area in a first information storage layer and a second optimal power control area in a second information storage layer of the information storage medium  130 . 
   Referring to  FIG. 8 , according to the control of the control unit  1002 , the writing/reading unit  1000  records data on a disc  130 , which is an information storage medium according to embodiments of the present invention, and reads out data in order to reproduce recorded data. The control unit  1002  controls the writing/reading unit  1000  so that the writing/reading unit  1000  records data in predetermined recording unit blocks, or processes data read by the writing/reading unit  1000  and obtains valid data. Reproducing refers to obtaining valid data by performing error correction for the read data, and is performed in predetermined units. The units for performing reproduction are referred to as reproducing unit blocks. A reproducing unit block corresponds to at least one recording unit block. 
     FIG. 9  is a more detailed block diagram of the optical recording and/or reproducing apparatus of  FIG. 8 . Referring to  FIG. 9 , the information storage medium  130  is loaded in the writing/reading unit  1000 . The recording and/or reproducing apparatus further includes an optical pickup  1100  that reads from and writes to the information storage medium  130 . The control unit  1002  includes a PC I/F  1101 , a DSP  1102 , an RF AMP  1103 , a servo  1104 , and a system controller  1105 , all of which constitute the control unit  1002  of  FIG. 8 . 
   In the data recording operation, the PC I/F  1101  receives a recording command with data to be recorded from a host. The DSP  1102  adds additional data such as a parity for error correction of the data received from the PC I/F  1101  and performs error correction and checking (ECC) encoding to generate an ECC block, which is an error correction block, and modulates the ECC block according to a predetermined method. The RF AMP  1103  converts the data output from the DSP  1102  into an RF signal. The pickup  1100  records the RF signal output from the RF AMP  1103  on the disc  130 . The servo  1104  receives a command required for servo control from the system controller  1105  and servo-controls the pickup  1100 . 
   In the data reproducing operation, the PC I/F  1101  receives a reproduction command from a host (not shown). The system controller  1105  performs the initialization required for reproduction. The pickup  1100  emits a laser beam onto the disc  130 , obtains an optical signal by receiving a reflected beam from the disc  130 , and outputs the optical signal. The RF AMP  1103  converts the optical signal output from the pickup  1100  into an RF signal and provides modulated data obtained from the RF signal to the DSP  1102  while providing a servo signal for control of the pickup  1100  obtained from the RF signal to the servo  1104 . The DSP  1102  demodulates the modulated data, performs error correction and outputs the resulting data. 
   Meanwhile, the servo  1104  performs servo control of the pickup  1100 , by using the servo signal received from the RF AMP  1103  and a command required for servo control received from the system controller  1105 . The PC I/F  1101  transfers the data received from the DSP  1102  to the host. 
   The aforementioned OPC area arrangement embodiments are applicable to all information storage media regardless of whether a track of each information storage layer is spiraled from an inner boundary to an outer boundary or from the outer boundary to the inner boundary. The aforementioned OPC area arrangements are also applicable to all information storage media having a plurality of information storage layers regardless of whether an information storage layer to be reproduced first is either an information storage layer farthest from or closest to an optical pickup. For example, the aspects of the present invention described above are applicable to CD-R, CD-RW, DVD+RW, HD-DVD, Bluray, and Advanced Optical Disc (AOD) type information storage media. Although the OPC area arrangements have been described with regard to a dual-layered information storage medium having two information storage layers, they may be applied to information storage media having at least three information storage layers which are stacked one on another. 
   As described above, in an aspect of an information storage medium having a plurality of information storage layers, an OPC area of one information storage layer may be located to not directly face the OPC area of another information storage layer. Information about an OPC area (that is, OPC information) in one information storage layer is recorded in a reserved area of an adjacent information storage layer that faces the OPC area, and the directions of data recording in an OPC area of one information storage layer and a reserved area of another information storage layer that faces the OPC area are set to be opposite. That is, directions of the use of the OPC area and the reserved area are set to be opposite. Therefore, an influence of the OPC executed in an OPC area of one information storage layer upon another information storage layer is minimized, and the size of an actually usable area of the OPC area of each information storage layer varies depending on the use circumstances of the OPC area. 
   Alternatively, the OPC area of one information storage layer may be located to not directly face the OPC area of another information storage layer each other, and a map area for storing OPC information is included between the OPC area and a reserved area of each information storage layer according to an aspect of the invention. Therefore, when the OPC area of one information storage layer performs the OPC, this OPC does not affect another information storage layer. Also, an area of each information storage layer can be efficiently used, and a time required to perform the OPC can be shortened. 
   Alternatively, the OPC area of one information storage layer may be located with respect to an OPC area of another information storage layer such that the OPC areas do not face each other, and, considering the fact that degrees of influence of the OPC areas of two adjacent information storage layers upon jitter characteristics are different, a reserved area is allocated in only one of the two information storage layers, and a usable area is allocated in the other information storage layer according to an aspect of the invention. Therefore, when the OPC area of one information storage layer performs the OPC, this OPC does not affect another information storage layer, and an area of each information storage layer can be efficiently used. 
   Although a few embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.