Patent Publication Number: US-7583573-B2

Title: Information storage medium having multiple storage layers with optimal power control (OPC) areas and buffer areas

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is a continuation of application Ser. No. 11/780,054 filed on Jul. 19, 2007, now U.S. Pat. No. 7,489,606, which is a continuation of application Ser. No. 10/866,087 filed on Jun. 14, 2004, now U.S. Pat. No. 7,274,638, the disclosures of which are incorporated by reference herein. This application also claims the benefit of Korean Patent Application No. 2003-62855 filed on Sept. 8, 2003, in the Korean Intellectual Property Office, and the benefit of U.S. Provisional Application Nos. 60/477,793 filed on Jun. 12, 2003, and 60/483,233 filed on Jun. 30, 2003, in the U.S. Patent and Trademark Office, the disclosures of which are incorporated by reference herein. 

   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 designed to control optimum writing power in optimal power control (OPC) areas even when eccentricity occurs among a plurality of information storage layers and a method and apparatus for recording/reproducing data on/from the information storage media. 
   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 are 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, HD-DVDs 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 by: 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 another method of forming a plurality of information storage layers. 
     FIG. 1  schematically shows 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  10 L 0  and  10 L 1 , respectively, for obtaining an optimal writing power and first and second defect management area (DMAs)  13 L 0  and  13 L 1 , respectively. The first and second OPC areas  10 L 0  and  10 L 1  are disposed to face each other. 
   Data is recorded in the first and second OPC areas  10 L 0  and  10 L 1  using various levels of writing power to find the optimum writing power. Hence, data may be recorded at a power level higher 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 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%-&gt;6.4% 
             
             
                 
               L1 
                 
               6.3% 
               6.2% 
               6.3% 
               6.2%-&gt;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  remain 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 a 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  10 L 0  and  10 L 1  of the first and second information storage layers L 0  and L 1  exist within an equal radius as shown in  FIG. 1 , one of them may not be usable. 
   The recording status of one of the first and second OPC areas  10 L 0  and  10 L 1  may affect the recording characteristics of the other OPC area. For example, as shown in  FIG. 2A , if data has been recorded on a part  10 L 0 _A of the first OPC area  10 L 0  and no data has been recorded on the residual area  10 L 0 _B thereof, the recording property of a part of the second OPC area  10 L 1  which corresponds to the occupied part  10 L 0 _A of the first OPC area  10 L 0  is different from that of a part of the second OPC area  10 L 1  which corresponds to the unoccupied part  10 L 0 _B of the first OPC area  10 L 0 . In other words, since the transmittance of the laser with respect to the occupied part  10 L 0 _A of the first OPC area  10 L 0  is different from the transmittance of a laser with respect to the unoccupied part  10 L 0 _B thereof, the recording property of the second OPC area  10 L 1  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. 
   During the manufacture of an information storage medium, eccentricity may occur. For example, an information storage medium having a single information storage layer may have eccentricity of about 70-80 μm (p-p) (where p denotes a peak). To manufacture an information storage medium having first and second information storage layers L 0  and L 1 , the first and second storage layers L 0  and L 1  are separately manufactured and then attached to each other. When eccentricity occurs during the manufacture of each of the first and second information storage layers L 0  and L 1 , they may be attached to each other such that areas of the first information storage layer L 0  are not aligned with those of the second information storage layer L 1  as shown in  FIG. 2B . 
   When the first and second OPC areas  10 L 0  and  10 L 1  are not in line, overlapped areas generated due to the out-of-line arrangement may affect each other. For example, if data is recorded on the first OPC area OPC_L 0  using higher power than the normal writing power, the first OPC area OPC_L 0  adversely affects a defect management area (DMA_L 1 ) of the second information storage layer L 1  because the DMA_L 1  contacts a part C of the first OPC area  10 L 0 . Also, a part D of the second OPC area OPC_L 1  may adversely affect a part of the first information storage layer that contacts the part D, and thus the part may not be used. 
   SUMMARY OF THE INVENTION 
   An aspect of the present invention provides an information storage medium including an area in which optimum power control (OPC) is performed, thereby preventing an area other than the OPC area from being affected by possible eccentricity. 
   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. 
   According to an aspect of the present invention, an information storage medium includes at least one information storage layer including an OPC area for obtaining an optical recording condition. OPC areas in adjacent information storage layers are disposed within different radiuses of the information storage medium. 
   According to an aspect of the present invention, when the OPC areas in the adjacent information storage layers are apart from each other a small distance in a radial direction of the information storage medium, the distance corresponds to at least a tolerance required upon manufacture of the information storage medium. 
   According to an aspect of the present invention, buffer areas each having a size corresponding to at least the tolerance is disposed on both sides of each of the OPC areas. 
   According to an aspect of the present invention, a length of the buffer area in the radial direction of the information storage medium is in the range of 5 to 100 μm. 
   According to an aspect of the present invention, an area for storing reproduction-only data is disposed in an information storage layer such as to face an OPC area of an adjacent information storage layer. 
   According to another aspect of the present invention, an information storage medium includes a plurality of information storage layers each including an OPC area for obtaining an optical recording condition. An OPC area in an odd-numbered information storage layer and an OPC area in an adjacent even-numbered information storage layer are disposed within different radiuses of the information storage medium such as not to face each other even when each of the information storage layers has a manufacturing error. 
   According to another aspect of the present invention, the information storage medium includes a defect management area and a user data area. A buffer area is included between the defect management area and the user data area. 
   According to another aspect of the present invention, an area for storing reproduction-only data may be disposed in an information storage layer such as to face an OPC area of an adjacent information storage layer. 
   According to another aspect of the present invention, an information storage medium includes a plurality of information storage layers, each including an OPC area for obtaining an optical recording condition and an area for storing reproduction-only data. An OPC area in an information storage layer is disposed to face a reproduction-only area of an adjacent information storage layer. 
   According to another aspect of the present invention, the reproduction-only area may be larger than the OPC area. 
   According to another aspect of the present invention, the buffer areas may be disposed at both sides of the OPC area, and each of the buffer areas may have a size obtained in consideration of at least one of the following factors: an error in the determination of a start position of each area; a size of a beam for recording and reproduction; and eccentricity. 
   According to another aspect of the present invention, the buffer areas are disposed at both sides of the optimal power control area, and the buffer area located in front of the optimal power control area may have a size corresponding to a pair of disk-related information and disk control data recorded once. 
   According to another aspect, a method of minimizing 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 an information storage medium, by disposing the first optimal power control area such that no overlap occurs with the second optimal power control area is provided. 

   
     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: 
       FIG. 1  illustrates a layout of a data area of a conventional dual-layered information storage medium; 
       FIGS. 2A and 2B  are views illustrating the influence of an OPC area upon an area other than the OPC area in the conventional dual-layered information storage medium of  FIG. 1 ; 
       FIG. 3A  illustrates a layout of a data area of a dual-layered information storage medium according to an embodiment of the present invention; 
       FIG. 3B  illustrates a layout of a data area of a single-layered information storage medium according to an embodiment of the present invention; 
       FIGS. 4A and 4B  illustrate different eccentric states of the dual-layered information storage medium of  FIG. 3A ; 
       FIG. 5A  illustrates a layout of a data area of a four-layered information storage medium according to an embodiment of the present invention; 
       FIG. 5B  illustrates an eccentric state of the four-layered information storage medium of  FIG. 5A ; 
       FIG. 6A  illustrates a variation of the dual-layered information storage medium of  FIG. 3A ; 
       FIGS. 6B and 6C  illustrate different eccentric states of the dual-layered information storage medium of  FIG. 6A ; 
       FIG. 7A  illustrates another variation of the dual-layered information storage medium of  FIG. 3A ; 
       FIG. 7B  illustrates a variation of the single-layered information storage medium of  FIG. 3B ; 
       FIG. 8  illustrates a layout of a data area of a dual-layered information storage medium according to another embodiment of the present invention; 
       FIG. 9  illustrates a variation of the dual-layered information storage medium of  FIG. 8 ; 
       FIG. 10  is a block diagram of an apparatus for recording/reproducing information to/from an information storage medium according to an embodiment of the present invention; and 
       FIG. 11  is a block diagram of a disk drive in which the apparatus of  FIG. 10  is implemented. 
   

   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  FIGS. 3A and 3B , an information storage medium according to an embodiment of the present invention includes at least one information storage layer, each of which includes an optimal power control (OPC) area for obtaining optimal power. The OPC areas are disposed within different radii such that the OPC areas do not to face each other. 
   Each of the information storage layers further includes a defect management area (DMA) and a data area in which user data is recorded. 
     FIG. 3A  illustrates a dual-layered information storage medium which includes first and second information storage layers L 0  and L 1 . The first information storage layer L 0  includes a first OPC area  20 _L 0 , a first DMA  23 _L 0 , and a first data area  35 _L 0 , and the second information storage layer L 1  includes a second OPC area  20 _L 1 , a second DMA  23 _L 1 , and a second data area  35 _L 1 . 
   The first and second OPC areas  20 _L 0  and  20 _L 1  are located within different radiuses of the information storage medium. First buffer areas  19 _L 0  and  21 _L 0  are disposed in front of and behind the first OPC area  20 _L 0 , respectively. Second buffer areas  19 _L 1  and  21 _L 1  are disposed in front of and behind the second OPC area  20 _L 1 , respectively. 
   Preferably, but not always required, the first and second buffer areas  19 _L 0 ,  21 _L 0 ,  19 _L 1 , and  21 _L 1  have lengths sufficient to cover a tolerance necessary for manufacturing an information storage medium. The tolerance is obtained in consideration of at least one of three factors: an error in the determination of the start position of each area; the size of a beam for recording and reproduction; and eccentricity. The error in the determination of the start position of each area is generated during mastering of the information storage medium and has a size of about 100 μm. In an information storage medium having no buffer areas between areas, when data is recorded on or reproduced from a track, an adjacent track is affected by a beam spot because the radius of the beam spot is typically greater than a track pitch. Thus, a buffer area is placed between areas. The size of the buffer area may be determined in consideration of the size of a recording and reproducing beam so as to prevent an influence of the recording and reproducing beam. 
   If the information storage medium used is manufactured with an error, the first and second buffer areas  19 _L 0 ,  21 _L 0 ,  19 _L 1 , and  21 _L 1  prevent the first and second OPC areas  20 _L 0  and  20 _L 1  from affecting other areas. 
   The first and second OPC areas  20 _L 0  and  20 _L 1  are disposed within different radii so that the first and second OPC areas  20 _L 0  and  20 _L 1  do not to face each other. In other words, the first OPC area  20 _L 0  faces a reserved area  30 _L 1 , and the second OPC area  20 _L 1  faces a reserved area  30 _L 0 . 
   The first and second OPC areas  20 _L 0  and  20 _L 1  are manufactured to be spaced apart from each other by a distance corresponding to no less than an allowable eccentricity amount in the radial direction of the information storage medium. In other words, a difference between locations of the first and second OPC areas  20 _L 0  and  20 _L 1  in the radial direction is no less than the allowable eccentricity amount. The difference between the locations of the first and second OPC areas  20 _L 0  and  20 _L 1  denotes a distance between a rear end of the first OPC area  20 _L 0  and a front end of the second OPC area  20 _L 1 . 
   Referring to  FIG. 3A , the first and second buffer areas  19 _L 1  and  21 _L 0  preferably are separated by a distance corresponding to no less than an allowable eccentricity amount. 
   The dual-layered information storage medium of  FIG. 3A  further includes at least one pair of a pair of buffer areas  31 _L 0  and  31 _L 1  and a pair of buffer areas  32 _L 0  and  32 _L 1  and reserved areas  30 _L 0  and  30 _L 1 . The reserved areas  30 _L 0  and  30 _L 1  may not be included. The buffer areas are disposed between the reserved area  30 _L 0  (or 30_L 1 ) and the OPC area  20 _L 0  (or  20 _L 1 ) and between the DAM  23 _L 0  (or  23 _L 1 ) and the data area  35 _L 0  (or  35 _L 1 ). 
   In the dual-layered information storage medium of  FIG. 3A , buffers are disposed on both sides of each of the first and second OPC areas  20 _L 0  and  20 _L 1  of the corresponding first and second information storage layers L 0  and L 1 . Preferably, this principle is equally applied to a single-layered information storage medium of  FIG. 3B . 
   Referring to  FIG. 3B , the single-layered information storage medium includes an OPC area  20  and buffer areas  19  and  21  disposed on both sides of the OPC area  20 . The single-layered information storage medium further includes a reserved area  30 , a DMA  23 , and a data area  35 . As illustrated in  FIG. 3B , a buffer area  31  is interposed between the reserved area  30  and the DMA  23 , and a buffer area  32  is interposed between the DMA  23  and the data area  35 . 
   To prevent an influence of eccentricity upon the information storage medium shown in  FIG. 3A , each of the first and second buffer areas  19 _L 0 ,  21 _L 0 ,  19 _L 1 , and  21 _L 1  has a size corresponding to the allowable eccentricity amount. Accordingly, even when the first and second information storage layers L 0  and L 1  are made eccentric by the maximum amount in the range of the allowable eccentricity amount, the OPC areas  20 _L 0  and  20 _L 1  of the first and second information storage layers, respectively, are arranged such that the OPC areas  20 _L 0  and  20 _L 1  do not face each other. 
   In an information storage medium with a 120 mm diameter, the allowable eccentricity amount is in the range of about 70-80 μm. In an information storage medium with a 60 mm diameter, the allowable eccentricity amount is in the range of about 20-30 μm. The allowable eccentricity amount varies depending on the size of an information storage medium. Hence, the first and second buffer areas  19 _L 0 ,  21 _L 0 ,  19 _L 1 , and  21 _L 1  have sizes in the range of 5 to 100 μm so as to cover the allowable eccentricity amounts of all possible kinds of information storage media. 
     FIGS. 4A and 4B  illustrate the first and second information storage layers L 0  and L 1 , which are made eccentric by the maximum amount within the range of the allowable eccentricity amount.  FIG. 4A  illustrates the first and second information storage layers L 0  and L 1  made eccentric toward the inner and outer boundaries, respectively, of the information storage medium of  FIG. 3A .  FIG. 4B  illustrates the first and second information storage layers L 0  and L 1  made eccentric toward the outer and inner boundaries, respectively, of the information storage medium of  FIG. 3A . 
   Referring to  FIG. 4A , when the information storage medium of  FIG. 3A  is in a maximal eccentric state, the first OPC area  20 _L 0  faces the buffer area  31 _L 1  (see circle A) or the reserved area  30 _L 1  instead of the second OPC area  20 _L 1 . Similarly, the second OPC area  20 _L 1  faces the buffer area  31 _L 0  (see circle B) or the reserved area  30 _L 0  instead of the first OPC area  20 _L 0 . 
   Referring to  FIG. 4B , when the information storage medium of  FIG. 3A  is in a maximal eccentric state, the first OPC area  20 _L 0  faces the buffer area  19 _L 1  (see circle A′), and the second OPC area  20 _L 1  faces the buffer area  21 _L 0  (see circle B′). 
   As described above, even when the information storage medium of  FIG. 3A  is in a maximal eccentric state, the first and second OPC areas  20 _L 0  and  20 _L 1  do not face each other and accordingly do not affect each other during a test for optimal power control. Of course, when the information storage medium as shown in  FIG. 3A  is not made eccentric, the first and second OPC areas  20 _L 0  and  20 _L 1  do not affect each other because they are originally disposed not to face each other. 
   The above-described layout of the dual-layered information storage medium of  FIG. 3A  can be equally applied to an information storage medium having more than two information storage layers. In other words, in an information storage medium having at least four information storage layers, odd-numbered information storage layers each have the layout of the first information storage layer L 0  of  FIG. 3A , and even-numbered information storage layers each have the layout of the second information storage layer L 1  of  FIG. 3A . 
     FIG. 5A  illustrates a four-layered information storage medium having first, second, third, and fourth information storage layers L 0 , L 1 , L 2 , and L 3 , respectively. The first, second, third, and fourth information storage layers L 0 , L 1 , L 2 , and L 3  include OPC areas  20 _L 0 ,  20 _L 1 ,  20 _L 2 , and  20 _L 3 , respectively, DMAs  23 _L 0 ,  23 _L 1 ,  23 _L 2 , and  23 _L 3 , respectively, and data areas  35 _L 0 ,  35 _L 1 ,  35 _L 2 , and  35 _L 3 , respectively. 
   If an information storage medium has a plurality of information storage layers, it has an odd-numbered information storage layer(s) and an even-numbered information storage layer(s). OPC areas  20 _L 1  and  20 _L 3  included in the odd-numbered information storage layer are referred to as first OPC areas, and OPC areas  20 _L 0  and  20 _L 2  included in the even-numbered information storage layer are referred to as second OPC areas. The first and second OPC areas in the odd-numbered and even-numbered information storage layers, respectively, are disposed within different radiuses of the information storage medium. A pair of buffer areas  19 _L 0  and  21 _L 0 , a pair of buffer areas  19 _L 1  and  21 _L 1 , a pair of buffer areas  19 _L 2  and  21 _L 2 , and a pair of buffer areas  19 _L 3  and  21 _L 3  for preventing an influence of the OPC due to eccentricity are disposed on both sides of each of the OPC areas  20 _L 0 ,  20 _L 1 ,  20 _L 2 , and  20 _L 3 , respectively. 
   Reserved areas  30 _L 0 ,  30 _L 1 ,  30 _L 2 , and  30 _L 3  are further included, and buffer areas  31 _L 0 ,  31 _L 1 ,  31 _L 2 , and  31 _L 3  may be further disposed adjacent to the reserved areas  30 _L 0 ,  30 _L 1 ,  30 _L 2 , and  30 _L 3 . 
     FIG. 5B  illustrates an eccentric state of the four-layered information storage medium of  FIG. 5A . Even when an information storage medium having at least three information storage layers is made eccentric, OPC areas in adjacent information storage layers do not face each other as illustrated in circles E and F of  FIG. 5B . Hence, an influence of the OPC executed in an OPC area upon another OPC area can be prevented. 
   Referring to  FIG. 6A , a variation of the dual-layered information storage medium of  FIG. 3A  includes at least one information storage layer which includes an OPC area for obtaining optimal power, a DMA, and a data area in which user data is recorded. A buffer area is disposed adjacent to the OPC area toward an inner or outer boundary of the information storage medium. 
   The dual-layered information storage medium of  FIG. 6A  includes first and second information storage layers L 0  and L 1 . The first and second OPC areas  20 _L 0  and  20 _L 1  of the first and second information storage layers L 0  and L 1  are disposed within different radiuses of the information storage medium such that the first and second OPC areas  20 _L 0  and  20 _L 1  do not to face each other. The first and second OPC areas  20 _L 0  and  20 _L 1  are disposed to be spaced apart from each other in the radial direction of the information storage medium by a distance corresponding to at least a maximum eccentricity amount. 
   The first buffer area  21 _L 0  is disposed on a side of the first OPC area  20 _L 0  that faces the outer boundary of the information storage medium, and the second buffer area  19 _L 1  is disposed on a side of the second OPC area  20 _L 1  that faces the inner boundary of the information storage medium. When the information storage medium has no eccentricity, the first and second buffer areas  21 _L 0  and  19 _L 1  face each other. The first and second buffer areas  21 _L 0  and  19 _L 1  have a length corresponding to at least the maximum eccentricity amount. The reserved areas  30 _L 0  and  30 _L 1  are disposed adjacent to the first and second buffer areas  21 _L 0  and  19 _L 1 . 
   In the information storage medium of  FIG. 6A , no buffer areas are included between the DMA  23 _L 0  and the data area  35 _L 0  and between the DMA  23 _L 1  and the data area  35 _L 1 . Thus, the information storage medium of  FIG. 6A  provides more area for storing user data than the information storage medium of  FIG. 3A . 
     FIGS. 6B and 6C  illustrate different maximum eccentric states of the dual-layered information storage medium of  FIG. 6A . When the first and second information storage layers L 0  and L 1  are made eccentric toward the inner and outer boundaries, respectively, of the information storage medium of  FIG. 6A  as shown in  FIG. 6B , the second OPC area  20 _L 1  faces the DMA  23 _L 0  in the first information storage layer L 0 . 
   When the first and second information storage layers L 0  and L 1  are made eccentric toward the outer and inner boundaries, respectively, of the information storage medium of  FIG. 6A  as shown in  FIG. 6C , the first OPC area  20 _L 0  faces the buffer area  19 _L 1  of the second information storage layer L 1 , and the second OPC area  20 _L 1  faces the buffer area  21 _L 0  in the first information storage layer L 0 . In other words, in this case, the first and second OPC areas  20 _L 0  and  20 _L 1  never face each other even when the information storage medium of  FIG. 6A  is made eccentric. Thus, the first and second OPC areas  20 _L 0  and  20 _L 1  do not affect each other. Also, a recording capacity of the information storage medium of  FIG. 6A  can be increased by reducing the buffer area as much as possible. 
     FIG. 7A  illustrates another embodiment of the dual-layered information storage medium of  FIG. 3A . Referring to  FIG. 7A , the first and second information storage layers L 0  and L 1  include first and second OPC areas  40 _L 0  and  40 _L 1 , respectively, DMAs  42 _L 0  and  42 _L 1 , respectively, and data areas  44 _L 0  and  44 _L 1 , respectively. A buffer area  39 _L 0  and a first reserved area  41 _L 0  are disposed at both sides of the first OPC area  40 _L 0 , and a buffer area  41 _L 1  and a second reserved area  39 _L 1  are disposed at both sides of the second OPC area  40 _L 1 . The information storage medium of  FIG. 7A  is the same as that of  FIG. 3A  in that the first and second OPC areas  40 _L 0  and  40 _L 1  are disposed within different radiuses. In contrast with  FIG. 3A , the first and second reserved areas  41 _L 0  and  39 _L 1  of  FIG. 7A  have different sizes than the reserved areas  30 _L and  30 _L 1  of  FIG. 3A . In  FIG. 3A , the buffer area  21 _L 0 , the reserved area  30 _L 0 , and the buffer area  31 _L 0  are sequentially disposed on a side of the first OPC area  20 _L 0  that faces the outer boundary. Similarly, in  FIG. 7A , the first reserved area  41 _L 0 , which has a length corresponding to the reserved area  30 _L 0  and the buffer areas  21 _L 0  and  31 _L 0 , is disposed on a side of the first OPC area  40 _L 0  that faces the outer boundary. 
   Also, in  FIG. 3A , the buffer area  31 _L 1 , the reserved area  30 _L 1 , and the buffer area  21 _L 1  are sequentially disposed on a side of the second OPC area  20 _L 1  that faces the inner boundary. Similarly, in  FIG. 7A , the second reserved area  39 _L 1 , which has a length corresponding to the reserved area  30 _L 1  and the buffer areas  21 _L 1  and  31 _L 1 , is disposed on a side of the second OPC area  40 _L 1  that faces the inner boundary. 
   As described above, the information storage media according to the various embodiments are manufactured so that OPC areas in adjacent information storage layers are located within different radiuses and that each of the OPC areas face a reserved area or a buffer area, thereby preventing a recording property from being degraded due to OPC. Preferably, the reserved area or the buffer area that faces each of the OPC areas is longer than each of the OPC areas. 
     FIG. 7B  illustrates another embodiment of the single-layered information storage medium of  FIG. 3B . To have a consistency with the dual-layered information storage medium of  FIG. 7A , the single-layered information storage medium of  FIG. 7B  includes an OPC area  40 , a buffer area  39  disposed at one side of the OPC area  40 , and a reserved area  41  disposed at the other side of the OPC area  40 . A DMA  42 , a buffer area  43 , and a data area  44  are disposed adjacent to the reserved area  41 . In this embodiment, the reserved area  41  is larger than the buffer area  39 . 
     FIG. 8  illustrates a layout of a data area of a dual-layered information storage medium according to another embodiment of the present invention. The dual-layered information storage medium of  FIG. 8  includes first and second information storage layers L 0  and L 1 . A second OPC area  47 _L 1  for controlling optimal recording power is included in the second information storage layer L 1 , and a first reproduction-only area  50 _L 0  for storing reproduction-only data is disposed at a location of the first information storage layer L 0  that faces the second OPC area  47 _L 1 . The first reproduction-only area  50 _L 0  is larger than the second OPC area  47 _L 1 . Examples of the reproduction-only data include a disc-related information and disk control data. 
   The first information storage layer L 0  further includes a first protection area  51 _L 0  and a first OPC area  47 _L 0 , between buffer areas  45 _L 0  and  48 _L 0 . The second information storage layer L 1  further includes buffer areas  45 _L 1  and  48 _L 1 , a second protection area  51 _L 1 , and a second reproduction-only area  50 _L 1 . The buffer areas  45 _L 1  and  48 _L 1  are disposed at both sides of the second OPC area  47 _L 1 . 
   The first and second protection areas  51 _L 0  and  51 _L 1  are used to obtain the time during which a disk drive accesses each area of a disk. In other words, a protection area is allocated to transit an area to another area in the radial direction of a disk. 
   Each of the first and second buffer areas  45 _L 0 ,  45 _L 1 ,  48 _L 0 , and  48 _L 1  has a length sufficient to cover a tolerance necessary for manufacturing an information storage medium. The tolerance is obtained in consideration of at least one of three factors: an error in the determination of the start position of each area; the size of a beam for recording and reproduction; and eccentricity. The error in the determination of the start position of each area is generated during mastering and has a size of about 100 μm. In an information storage medium having no buffer areas between areas, when data is recorded on or reproduced from a track, an adjacent track is affected by a beam spot because the radius of the beam spot is typically greater than a track pitch. Thus, a buffer area is placed between areas in embodiments of the present invention. The size of the buffer area may be determined in consideration of the size of a recording and reproducing beam so as to prevent an influence of the recording and reproducing beam. 
   To prevent an influence of the OPC from an adjacent information storage layer, the first OPC area  47 _L 0  in the first information storage layer L 0  is located to face the second reproduction-only area  50 _L 1 , and the second OPC area  47 _L 1  in the second information storage layer L 1  is located to face the first reproduction-only area  50 _L 0 . 
   Disk-related information and disk control data, which are examples of reproduction-only data, may be recorded many times in the first and second reproduction-only areas  50 _L 0  and  50 _L 1  in order to increase the reliability of information. In this case, to face an area corresponding to at least one pair of disk-related information and disk control data, each of the buffer areas  45 _L 0  and  45 _L 1  is longer than a pair of disk-related information and disk control data for one recording. 
   Because the recording of a reproduction-only area is rarely affected by the OPC process, the area is located directly over or below an OPC area in the information storage medium of  FIG. 8 . Thus, while the reproduction-only area is used to prevent an influence of OPC in an OPC area upon another OPC area, the reproduction only area is also used as a data area. Also, because the first and second OPC areas  47 _L 0  and  47 _L 1  as arranged never face each other even when eccentricity occurs in the information storage medium of  FIG. 8 , performing an OPC process in an OPC area does not affect another OPC area which is on a different layer. 
     FIG. 9  illustrates a variation of the dual-layered information storage medium of  FIG. 8 . in the dual-layered information storage medium of  FIG. 9 , a first information storage layer L 0  includes the first reproduction-only area  50 _L 0  of  FIG. 8 , in which disk-related information for reproduction-only and disk control data for reproduction-only are recorded, and a first protection area  51 _L 0 . A second information storage layer L 1  includes an OPC area  47 _L 1  that faces the first reproduction-only area  50 _L 0 . First and second buffer area  45 _L 1  and  49 _L 1  are disposed at both sides of the OPC area  47 _L 1 . The information storage medium of  FIG. 9  is different from that of  FIG. 8  in that the second buffer area  49 _L 1  is sized to approximate the size of the second buffer  48 _L 1  of  FIG. 8  and the second protection area  51 _L 1  of  FIG. 8 . As described above, the buffer area may have various sizes depending on its purpose, use, or the like. 
   Even if the information storage media of  FIGS. 8 and 9  are made eccentric, or an error is generated in a location of each of the information storage media of  FIGS. 8 and 9  where each area starts, the OPC area  47 _L 1  always faces the first reproduction-only area  50 _L 0 . Hence, the reproduction-only area  50 _L 0  prevents the OPC in an OPC area of a layer from affecting an area of an adjacent layer and is used as a data area. 
     FIG. 10  is a block diagram of a recording and/or reproducing apparatus in which the information storage media of  FIGS. 3-9  are implemented. Referring to  FIG. 10 , the recording and/or reproducing apparatus includes a writer/reader unit  100  and a controller  120 . The reader/writer unit  100  reads from and writes to the information storage medium  130  according to commands from the controller  120 . 
     FIG. 11  is a more detailed block diagram of the recording and/or reproducing apparatus of  FIG. 10 . Referring to  FIG. 11 , the information storage medium  130  is loaded in the reader/writer unit  100 . The reader/writer unit  100  includes an optical pickup  110  which reads from and writes to the information storage medium  130 . The recording and/or reproducing apparatus further includes a PC I/F  121 , a DSP  122 , an RF AMP  123 , a servo  124 , and a system controller  125 , all of which constitute the controller  120 . 
   Upon a recording operation being initiated, the PC I/F  121  receives a recording command together with data to be recorded, from a host (not shown). The system controller  125  performs the initialization necessary for recording, such as determining an OPC. More specifically, the system controller  125  reads out information necessary for initialization, such as, disk-related information stored in a lead-in area of an information storage medium  130 , and prepares for recording based on the read-out information. The DSP  122  performs ECC encoding on the to-be-recorded data received from the PC I/F  121  by adding data such as parity to the received data, and then modulates the ECC-encoded data in a specified manner. The RF AMP  123  converts the data received from the DSP  122  into an RF signal. The pickup  110  records the RF signal received from the RF AMP  123  to the information storage medium  130 . The servo  124  receives a command necessary for servo control from the system controller  125  and servo-controls the pickup  110 . If the information storage medium  130  stores no reproducing speed information, the system controller  125  commands the pickup  110  to write the reproducing speed information to a specified area of the information storage medium  130  when recording starts, while recording is being executed, or after recording has been completed. 
   Upon a reproduction operation being initiated, the PC I/F  121  receives a reproduction command from the host (not shown). The system controller  125  performs the initialization necessary for reproduction. When the initialization is completed, the system controller  125  reads out reproducing speed information recorded on the information storage medium  130  and performs reproduction at a reproducing speed corresponding to the read-out reproducing speed information. The pickup  110  projects a laser beam onto the information storage medium  130 , receives a laser beam reflected by the information storage medium  130 , and outputs an optical signal. The RF AMP  123  converts the optical signal received from the pickup  110  into an RF signal, supplies modulated data obtained from the RF signal to the DSP  122 , and supplies a servo control signal obtained from the RF signal to the servo  124 . The DSP  122  demodulates the modulated data and outputs data obtained through ECC error correction. The servo  124  receives the servo control signal from the RF AMP  123  and a command necessary for servo control from the system controller  125  and servo-controls the pickup  110 . The PC I/F  121  sends data received from the DSP  122  to the host (not shown). 
   A method of recording data to an information storage medium having multiple layers according to an embodiment of the present invention comprising recording data in the optimal power control area and obtaining an optical recording condition. The optimal power control areas are disposed in adjacent ones of the information storage layers within different radiuses of the information storage medium such that interference among the optimal power control areas is prevented. 
   As described above, even when an information storage medium according to the present invention is made eccentric or has a manufacturing error, a recording property of the information storage medium is prevented from being degraded due to an influence of an OPC area in an information storage layer upon an OPC area in an adjacent information storage layer. 
   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.