Patent Publication Number: US-7898921-B2

Title: Optical disc, optical disc recording apparatus, and optical disc recording method

Description:
This application is a divisional application of Ser. No. 10/519,535, filed Aug. 4, 2005 now U.S. Pat. No. 7,539,111 which is a National Stage of International Application No. PCT/JP2003/008262, filed Jun. 30, 2003. 
    
    
     TECHNICAL FIELD 
     The present invention relates to an optical disc having a drive information area for recording a plurality of recording/playback conditions and other drive information, and to a recording apparatus and a recording method for recording to this optical disc. 
     BACKGROUND TECHNOLOGY 
     As optical discs have increased in recording density and capacity, assuring optical disc reliability has become increasingly important. To assure this reliability, optical disc drives use a learning process to determine the recording and playback conditions of the disc. This learning process is taught, for example, in Japanese Unexamined Patent Appl. Pub. 2001-338422. 
     These recording and playback conditions depend greatly upon the characteristics of the optical disc and the characteristics of the optical disc drive. As a result, the learning process used to determine the recording/playback conditions must be executed every time the optical disc drive is started after an optical disc is loaded, and whenever there is a change in either optical disc or optical disc drive characteristics due to such factors as a change in temperature. 
     Even more recently, further advances in optical disc recording density and storage capacity have made it necessary to determine the recording/playback conditions even more precisely. However, determining the recording/playback conditions more precisely by means of this learning process means that the learning process takes more time. As a result, the optical disc drive spends more time waiting for recording or playback to start. 
     SUMMARY OF THE INVENTION 
     The present invention is directed to resolving the foregoing problems, and an object of this invention is to provide an optical disc whereby the time required for the learning process to determine the recording/playback conditions can be shortened. 
     To achieve this object, an optical disc according to the present invention has a data recording area for recording data and a drive information area for recording drive information. The drive information area stores a plurality of recording/playback conditions, and the plurality of recording/playback conditions are arranged chronologically according to when the conditions are recorded to the disc. 
     A further optical disc according to the present invention has a plurality of recording layers with each recording layer read by a read beam incident thereto from the same side of the disc. A drive information area for recording drive information is provided on at least one of the plurality of layers, and an unrecorded blank area is provided in the other recording layers at the same radial position as the drive information area. 
     A plurality of recording/playback conditions are thus recorded chronologically in the order in which the recording/playback conditions are recorded to an optical disc according to the present invention. The drive information is therefore assured of always containing the most recent recording/playback conditions. 
     Furthermore, the radial position where the drive information area is rendered in one recording layer is left unrecorded and blank in the other recording layers of a multilayer optical disc according to the present invention, thereby assuring that the drive information can be read stably. 
     Other objects and attainments together with a fuller understanding of the invention will become apparent and appreciated by referring to the following description and claims taken in conjunction with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the layout of an optical disc  101  according to a first embodiment of the present invention; 
         FIG. 2  shows the logic structure of areas in the optical disc shown in  FIG. 1 ; 
         FIG. 3  shows an example of an ECC block; 
         FIG. 4  shows the structure of the drive information area; 
         FIG. 5  shows the data layout in the drive information area; 
         FIG. 6  shows the data layout in the drive information area; 
         FIG. 7  shows the data layout in the drive information area; 
         FIG. 8  shows the data layout in the drive information area; 
         FIG. 9  shows the data layout in the drive information area; 
         FIG. 10  shows the data layout in the drive information area; 
         FIG. 11  is a block diagram of an optical disc drive; 
         FIG. 12  is a flow chart of the optical disc drive operation; 
         FIG. 13  shows the structure of an optical disc with two recording layers; 
         FIG. 14  shows the logic structure of areas in an optical disc according to a second embodiment of the present invention; 
         FIG. 15  shows the logic structure of areas in an optical disc according to a third embodiment of the present invention; 
         FIG. 16  shows the data layout in the drive information area; 
         FIG. 17  shows the data layout in the drive information area; and 
         FIG. 18  shows the data layout in the drive information area. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A data recording medium according to the present invention has a drive information area for recording drive-specific information such as recording and playback conditions. A data recording and playback apparatus acquires the recording/playback conditions through a learning process, and records the recording/playback conditions to the drive information area of the data recording medium. The recording/playback conditions recorded to the drive information area of the data recording medium are read and used to acquire new recording/playback conditions the next time the learning process is executed. 
     These recording/playback conditions are the operating conditions used by the optical disc drive when the optical disc drive records information to an optical disc or reproduces recorded information from the optical disc. 
     The recording/playback conditions also include at least one of the following: pulse conditions relating to the laser pulse emitted to the optical disc, servo conditions controlling servo operation during recording and playback, and playback signal processing conditions for processing the playback signal. 
     The pulse conditions include, for example, the power of the laser pulse emitted to the optical disc during recording, or the laser pulse conditions for forming marks (the smallest unit of information) on the optical disc. When marks are formed on the optical disc by emitting a plurality of pulses to the optical disc from the leading edge to the trailing edge of the mark, the pulse conditions include at least the output timing and length of the first pulse, and the pulse power of the laser beam in this first pulse, which corresponds to the leading end of the mark, or the output timing and length of the last pulse, and the power of the laser beam in the last pulse, which corresponds to the trailing end of the mark. 
     The recording/playback conditions could alternatively be the settings of various circuits contained in the data recording and playback apparatus, or codes denoting those settings. 
     Thus, reusing the recording/playback conditions recorded in the drive information area of the data recording medium simplifies the learning process. As a result, less time is needed to complete the learning process, and the data recording and playback apparatus thus spends less time waiting before recording or playback can begin. 
     Preferred embodiments of the present invention are described in detail next below with reference to the accompanying figures. 
     Embodiment 1 
       FIG. 1  shows the arrangement of a data recording medium  101  according to a first embodiment of the present invention. 
     This data recording medium  101  is an optical disc having a plurality of concentric tracks  102 . Alternatively, a single spiral track  102  or a plurality of spiral tracks  102  could be formed to the optical disc  101 . 
     The track area of the optical disc  101  includes a lead-in area  103 , data recording area  104 , and lead-out area  105 . 
     Parameters required to access the optical disc  101  are recorded in the lead-in area  103 . The lead-in area  103  is formed at the inside circumference portion of the optical disc  101 . 
     The lead-out area  105  could also be used to record parameters required to access the optical disc  101 . The lead-out area  105  is located at the outside circumference portion of the optical disc  101 . 
     Data is recorded and reproduced in the data recording area  104 . 
       FIG. 2  shows the logic structure of the lead-in area  103 , data recording area  104 , and lead-out area  105  on the optical disc  101  shown in  FIG. 1 . 
     The lead-in area  201  includes a prerecorded area  204  and a recordable data recording area  205  for recording data. The prerecorded area  204  stores optical disc  101  identification data, for example, recorded in a wobble track, embossed pits, or wobbled embossed pits. 
     The prerecorded area  204  includes a protected zone  208  as a buffer, and a control data zone  209 . The control data zone  209  stores at least one of the following as optical disc  101  identification information: disc type, disc capacity, disc structure, channel bit, data zone address information, data rate, maximum playback power, recording power information, recording pulse position information, and disc-specific information. 
     The data recording area  205  includes a protected zone  210 , a reserved zone  211  enabling future development, a test zone  212  used for testing the optical disc  101 , a buffer zone  213 , a drive information zone  214  used for storing information such as the optical disc  101  characteristics, and a buffer zone  215 . If the track pitch differs in the prerecorded area  204  and data recording area  205 , the protected zone  210  can be used as a track pitch transition area. 
     The data recording area  202  includes a data recording area  206  for recording user data, for example. The data recording area  206  includes a user data recording zone  216 . 
     The lead-out area  203  includes a recordable data recording area  207  for recording data. The data recording area  207  includes a buffer zone  217 , a reserved zone  218  enabling future development, a buffer zone  219 , and a protected zone  220  where data is not recorded. 
     The drive information zone  214  is segmented into 2048 ECC blocks (clusters), for example. The ECC blocks are used for calculating an error correction code. The error correction code is calculated for each ECC block. Each ECC block is segmented into 32 sectors, for example. 
       FIG. 3  shows an example of the ECC block structure. To achieve a high error correction capability and low redundancy in a high capacity optical disc, each ECC block is divided into 32 sectors. For simplicity, however, one ECC block is divided into only 4 sectors in the example shown in  FIG. 3 . 
     As shown in  FIG. 3 , each ECC block includes 172 bytes×48 rows of Main Data, Parity of Inner Code PI acquired by calculating the error correction code for each row of Main Data, and Parity of Outer Code PO acquired by calculating the error correction code for each vertical column of Main Data. 
     Error correction codes including inner code parity and outer code parity are generally called product codes. A product code affords strong error correction of both random errors and burst errors (errors that are concentrated locally), such as where there is both random error and a burst error across two rows due to a scratch. Most such burst errors are 2-byte outer code errors and can be corrected. In a column where there are many random errors, however, correction using the outer code is not possible and errors remain, but these remaining errors can usually be corrected using the inner code. Even if inner code correction leaves some errors, these errors can be further reduced by applying outer code correction again. Redundant parity is suppressed and good error correction is assured by using this type of product code in DVD media. More specifically, user data capacity can be increased according to the decrease in redundant parity data. 
     As shown in  FIG. 3 , the Parity of Outer Code PO for the ECC block is evenly distributed one row per sector. As a result, one sector thus comprises 182 bytes×13 rows of data. 
     When the optical disc drive is instructed to record or play an optical disc  101  loaded in the optical disc drive by sector unit, the optical disc drive reads the ECC block containing the specified sector from the optical disc  101 , applies error correction, and records only the data corresponding to the specified sector to the optical disc  101 . 
     When the optical disc drive is instructed to record an optical disc  101  loaded in the optical disc drive by sector unit, the optical disc drive reads the ECC block containing the specified sector from the optical disc  101 , applies error correction, replaces the data from the specified sector with the data to be recorded, recalculates the ECC and adds the new ECC to the data to be recorded, and then records the ECC block containing the specified sector to the optical disc  101 . 
     A “cluster” as used below means an ECC block as described above. 
       FIG. 4  shows the structure of the drive information zone  214  shown in  FIG. 2 . 
     The drive information zone  214  contains a plurality of clusters  401   a , such as 2048 clusters  401   a . These clusters  401   a  are numbered sequentially from cluster # 1  at the inside circumference side to cluster # 2 , . . . cluster # 2048  at the outside circumference side of the drive information zone  214 . 
     Each cluster includes a plurality of sectors  401   b , such as 32 sectors  401   b . These sectors  401   b  are also arranged sequentially from sectors # 1  at the inside circumference side to sectors # 2 , . . . sectors # 32  at the outside circumference side. The capacity of each sector is sufficient to record one drive-specific information record. 
     The drive-specific information recorded to each of these sectors defines the operating conditions of the optical disc drive required to record or play data on a loaded optical disc  101 . The drive-specific information includes a manufacturer identifier  402 , auxiliary information  403 , a drive identifier  404 , and a data storage area  405 . The manufacturer identifier  402  identifies the manufacturer of the optical disc drive. The drive identifier  404  is a serial number, for example, used by the manufacturer to identify that optical disc drive. The data storage area  405  records information such as the recording/playback conditions, such as the required laser power level. Because the recording/playback conditions are stored to the data storage area  405 , the drive-specific information is also referred to herein as the recording/playback conditions. It will be obvious that the information stored to the data storage area  405  could be information other than the recording/playback conditions. 
     Each time a disc is loaded to a different optical disc drive, drive-specific information is generated and recorded to the disc. When a disc is reloaded in an optical disc drive to which it was previously loaded, the drive-specific information for that optical disc drive is read and used as the drive information for using the disc. 
     Whether a disc was previously loaded in a particular optical disc drive is determined by reading the drive identifier  404 . Furthermore, even if the optical disc drive determines that the disc was previously used in that drive, if the recording/playback conditions stored on the disc differ from the current conditions, the drive-specific information can be generated again. As a result, drive-specific information for the same optical disc drive could be recorded more than once to the same optical disc. 
     The first drive-specific information generated for a particular disc is denoted D( 1 ), the second record of drive-specific information is denoted D( 2 ), and the n-th drive-specific information record is denoted D(n). 
     The steps for recording a new drive-specific information record to disc are described next below with reference to  FIG. 5 ,  FIG. 6 ,  FIG. 7 , and  FIG. 8 . 
     As shown in  FIG. 5 , when a new disc is loaded to optical disc drive A, drive-specific information is generated for the first time, and drive-specific information D( 1 ) is written to sector # 1  of cluster # 1 . 
     When the same disc is then loaded in a second optical disc drive B, a second drive-specific information entry D( 2 ) is generated and written to sector # 1  of cluster # 2  as shown in  FIG. 6 . The first drive-specific information D( 1 ) recorded in cluster # 1  is also copied to sector # 2  of cluster # 2 . The previously used cluster # 1  is left unused. 
     When the same disc is then loaded in a third optical disc drive C, drive-specific information D( 3 ) for the third drive is generated, and record D( 3 ) is recorded to sector # 1 , cluster # 3 . The previous entries D( 2 ) and D( 1 ) previously recorded to cluster # 2  are also copied in the same sequence to sector # 2  and sector # 3  of cluster # 3 . The previously used clusters # 1  and # 2  are abandoned. 
     When the same disc is then loaded in a fourth optical disc drive D, drive-specific information D( 4 ) for the fourth drive is generated, and entry D( 4 ) is recorded to sector # 1 , cluster # 4 . The previous entries D( 3 ), D( 2 ) and D( 1 ) previously recorded to cluster # 3  are also copied in the same sequence to sectors # 2 , # 3 , and # 4  of cluster # 4 . The previously used clusters # 1 , # 2 , and # 3  are abandoned. 
     As shown in  FIG. 9 , when the same disc is loaded in a k-th (where k is a positive integer) optical disc drive K, the k-th drive-specific information D(k) is generated and written to sector # 1  of the k-th cluster #k. If k≦32, all previous entries D(k−1) . . . D( 2 ), D( 1 ) written to the last-recorded cluster #(k−1) are also copied in the same sequence to sectors # 2 , # 3 , . . . #k of k-th cluster #k. If k&gt;32 (the situation shown in  FIG. 9 ), the drive-specific information entries to the last-recorded entry, that is, D(n+30), D(n+29), . . . D(n+1), D(n) (where n=k−31) recorded to the last-recorded cluster #(k−1) are copied in the same sequence to the remaining sectors # 2 , # 3 , . . . #k of cluster #k. Entry D(n−1) is not recorded because the sectors are filled when entry D(n) is recorded. The previously used clusters # 1 , # 2 , . . . #(k−1) are abandoned. 
     Note that the k-th drive is not necessary the k-th different drive, and could be a drive to which the disc was previously loaded, such as optical disc drive A when optical disc drive A was not used for a specified period of time (such as six months), or the optical disc drive A settings were changed, or an environmental temperature sensor disposed in the optical disc drive A senses a temperature different from the temperature the last time the disc was loaded, for example. 
     As shown in  FIG. 10 , when the same disc is loaded in a (k+1)-th optical disc drive K+1, the (k+1)-th drive-specific information D(k+1) is generated and written to sector # 1  of the (k+1)-th cluster #(k+1). The drive-specific information entries to the last-recorded entry, that is, D(n+31), D(n+30), D(n+29), . . . D(n+1) recorded to the last-recorded k-th cluster #(k) are copied in the same sequence to the remaining sectors # 2 , # 3 , . . . #k of cluster #(k+1). Entry D(n) is not recorded because the sectors are filled. The previously used clusters # 1 , # 2 , . . . #(k) are abandoned. 
     Up to 32 records of drive-specific information, that is, recording/playback conditions, can thus be recorded in one cluster. The drive-specific information is recorded chronologically from the newest to oldest based on when the entry was written to the optical disc  101 . The 32 drive-specific information entries are thus recorded with the entry most recently recorded to the optical disc  101  in the first sector of the cluster and the oldest of the 32 entries recorded in the last sector of cluster #k. 
     In addition, drive-specific information, that is, recording/playback conditions determined by a new learning process are recorded to the beginning of cluster #k. As a result, drive information area  502  is always assured of containing up to 32 recording/playback conditions entries including the results of the most recent learning process. 
     The drive information zone  214  contains N ECC blocks (clusters). Each of the N ECC blocks (clusters) contains a plurality of sectors. Each of the plural drive-specific information entries contained in each cluster  401   a  is recorded to a single corresponding sector. N is any positive integer value or 1 or more, and in this example is 2048. 
       FIG. 11  is a block diagram of an optical disc drive. Shown in  FIG. 11  are an optical disc  101 , a disc detection device  4  for detecting if a disc has been loaded, a controller  6 , memory  8 ; and a disc drive  10  for reading and writing the  101 . The memory  8  stores information specific to the optical disc drive, including the manufacturer identifier  402  identifying the manufacturer of the optical disc drive, auxiliary information  403 , and a drive identifier  404  such as a serial number used by the manufacturer to identify that optical disc drive. 
     Operation of this optical disc drive is shown in  FIG. 12  and described below. 
     The disc detection device  4  detects if an optical disc has been loaded (step S 1 ). 
     The drive information area of the lead-in area on the loaded disc is then accessed (step S 2 ). 
     Starting from the first cluster, each cluster is inspected to determine if the cluster has been recorded or not in order to detect the first unrecorded cluster (step  33 ). 
     The last-recorded cluster, which is the recorded cluster immediately preceding the first unrecorded cluster, is then decoded (step S 4 ). 
     The sector number m is reset to 1 in order to read the sectors of the decoded last-recorded cluster starting from the first sector (step S 5 ). 
     Sector m (where m=1 at this time) is then read (step S 6 ). 
     The drive identifier  404  stored in memory  8  in the optical disc drive is then detected (the detected drive identifier is called the “detected identifier”), the drive identifier recorded in sector m (the “registered identifier”) is read, and whether the detected identifier and registered identifier are the same is determined. If the identifiers are the same, controls skips to step S 13 . If the identifiers are not the same, control goes to step S 8 . 
     In step S 13 , the drive control information recorded in the data storage area  405  of the target sector (sector m of the last-recorded cluster if step S 13  is entered from step S 7 ) is read and used to configure the disc drive  10 . The disc drive  10  can then proceed with reading/writing the disc based on the read drive control information without first test writing or test reading. As a result, the time between loading the disc and starting to read or write the disc can be shortened. 
     In step S 8 , sector number m is incremented one. 
     Whether sector number m is greater than the maximum sector number m max  is then determined (step S 9 ). In this example, maximum sector number m max  is 32. If sector number m is less than or equal to m max , the procedure loops back to step S 6  and steps S 7  and S 8  repeat. If sector number m is greater than M max , control goes to step S 10 . 
     In step S 10 , the disc drive  10  tests writing and reading the optical disc  101  in the test zone  212  to determine the optimum power level for the loaded disc, and thus compiles drive-specific information for the optical disc drive. This drive-specific information is the first drive-specific information acquired from that optical disc drive for that disc, and is thus referred to herein as new drive-specific information. 
     The new drive-specific information is then written to the first sector (sector # 1 ) of the first unrecorded cluster (step S 11 ). 
     The information from all sectors other than the last sector (that is, sector # 1  to sector # 31 ) in the last-recorded cluster is then copied to the sectors other than the first sector (that is, sector # 2  to sector # 32 ) in the first unrecorded cluster (step S 12 ). 
     In step S 13 , the drive control information recorded in the data storage area  405  of the target sector (the first sector of the first unrecorded cluster if step S 13  is entered from step S 12 ) is used to configure the disc drive  10 . The disc drive  10  can then proceed with reading/writing the disc. 
     Note that when new drive-specific information is produced the disc drive  10  could be configured based on that information before the information is recorded to a sector as described above. 
     As will be known from the above, when a single disc is loaded into the same optical disc drive, the optical disc drive accesses the drive information zone  214 , checks the drive-specific information clusters sequentially from the first cluster to find the first unrecorded cluster, and then starts reading from the first sector in the last-recorded cluster, that is, the cluster before the first unrecorded cluster. As a result, the drive-specific information is read sequentially from the newest to the oldest information. That is, the drive-specific information is arranged so that the last-recorded information is read first. 
     As will also be known from the above, one cluster is used for one recording of drive-specific information. Cluster # 1  is used for the first recording, cluster # 2  is used for the second recording, and so forth, proceeding sequentially from the inside circumference side of the disc. Therefore, when drive-specific information has been recorded k times, cluster # 1  to cluster #k are recorded, and the newest information is stored in cluster #k. 
     Updating the drive information area  401  thus assures that the most recently recorded cluster #(k+1) in the drive information area  401  always contains the 32 newest recording/playback conditions  401   b , and by reading this cluster first, the learning time can be shortened if the recording/playback conditions that can be used are found. 
     By thus structuring the drive information area  401  so that the so that data is updated by appending to unrecorded areas of the disc, the method of the present invention is not limited to use with rewritable optical disc media, and can also be used with write-once optical disc media. 
     Embodiment 2 
       FIG. 13  shows the structure of a single-side, two-layer optical disc according to a second embodiment of the present invention. 
     As shown in  FIG. 13  this optical disc has a first substrate  601 , first recording layer  602 , a space layer  603  of an adhesive resin, for example, a second recording layer  604 , and a second substrate  605 . 
     The laser beam is emitted from the second substrate  605  side of the disc shown in  FIG. 13  to read and write data to the first recording Layer  602  and second recording layer  604 . 
     A single or multiple spiral tracks could be formed on the first recording layer  602  and second recording layer  604 . 
       FIG. 14  shows the logic structure of a two-layer optical disc according to this embodiment of the invention. 
     The prerecorded area  701   a  of the first recording layer stores, for example, identification data for the two-layer optical disc recorded in a wobble track, embossed pits, or wobbled embossed pits. 
     The prerecorded area  701   a  includes a protected zone  703   a  as a buffer, and a control data zone  704   a . The control data zone  704   a  stores at least one of the following as optical disc identification information: disc type, disc capacity, disc structure, channel bit, data zone address information, data rate, maximum playback power, recording power information, recording pulse position information, and disc-specific information. 
     The information recorded in the control data zone  704   a  on the first recording layer could be information relating only to the first recording layer, or information relating to the first recording layer and information relating to the second recording layer. 
     The prerecorded area  701   b  on the second recording layer is located at the same radial position as the prerecorded area  701   a  of the first recording layer. 
     This prerecorded area  701   b  also includes a protected zone  703   b  as a buffer, and a control data zone  704   b . The control data zone  704   b  stores at least one of the following as optical disc identification information: disc type, disc capacity, disc structure, channel bit, data zone address information, data rate, maximum playback power, recording power information, recording pulse position information, and disc-specific information. 
     The information recorded in the control data zone  704   b  on the second recording layer could be information relating only to the first recording layer, or information relating to the first recording layer and information relating to the second recording layer. The control data zones  704   a  and  704   b  could store the same information. 
     The data recording area  702   a  on the first recording layer includes a protected zone  705   a  in which data is not recorded, a reserved zone  706   a  enabling future development, a test zone  707   a  used for testing the optical disc, a buffer zone  708   a , a drive information zone  709   a  used for storing information such as optical disc characteristics, a buffer zone  710   a , a user data recording zone  711   a  for recording user data, a buffer zone  712   a , a reserved zone  713   a  enabling future development, a buffer zone  714   a , and a protected zone  715   a  in which data is not recorded. 
     If the track pitch differs in the prerecorded area  701   a  and data recording area  702   a , the protected zone  705   a  can be used as a track pitch transition area. 
     The data recording area  702   b  on the second recording layer likewise includes a protected zone  705   b  in which data is not recorded and which can be used as a track pitch transition area when the track pitch differs in the prerecorded area  701   b  and data recording area  702   b . The protected zone  705   b  on the second recording layer is located at the same radial position as the protected zone  705   a  on the first recording layer. 
     The data recording area  702   b  on the second recording layer also includes a test zone  707   b  used for testing the optical disc. This test zone  707   b  is located at the same radial position as, or at a radial position on the inside circumference side of, the reserved zone  706   a  on the first recording layer. 
     The data recording area  702   b  also includes a reserved zone  706   b  for future developments. This reserved zone  706   b  is located at the same radial position as, or at a radial position on the inside circumference side of, the test zone  707   a  on the first recording layer. 
     The data recording area  702   b  on the second recording layer also includes a buffer zone  708   b , which is located at the same radial position as the buffer zone  708   a  on the first recording layer. 
     The data recording area  702   b  on the second recording layer also includes a reserved zone  709   b  to which data is not recorded. This reserved zone  709   b  is located at the same radial position as the drive information zone  709   a  of the first recording layer. 
     The data recording area  702   b  on the second recording layer also includes a buffer zone  710   b , a user data recording zone  711   b  for recording user data, another buffer zone  712   b , another reserved zone  713   b  enabling future developments, a buffer zone  714   b , and a protected zone  715   b  to which data is not recorded. Each of these zones is located at the same radial position as the corresponding buffer zone  710   a , user data recording zone  711   a , buffer zone  712   a , reserved zone  713   a  enabling future developments, buffer zone  714   a , and protected zone  715   a  to which data is not recorded in the first recording layer. 
     When the disc is spun for reading and writing along the tracks on the first and second recording layers, the read/write direction of the tracks on the first recording layer is from inside to outside circumference as indicated by arrow  716   a  in  FIG. 14 , and the read/write direction of the tracks on the second recording layer is from outside to inside circumference as indicated by arrow  716   b.    
     Because the control data zones are located at the same radial position in the first and second recording layers with the disc arrangement according to this embodiment of the invention, the control data can be read from either recording layer, and the identification information can thus be acquired more quickly. 
     Furthermore, because a reserved zone  709   b  where data is not recorded is located on the second recording layer at the same radial position as the drive information zone  709   a  on the first recording layer, the drive information zone  709   a  can be read or written through a second recording layer that is always in the same state (that is, blank in this embodiment). As a result, the drive information can be read and written consistently and stably. 
     Yet further, because a reserved zone where data is not recorded is disposed at the same radial position as at least part of the test zone with the disc format according to the present invention, disc testing can be conducted under consistently stable conditions through another layer that is always in the same state (that is, blank in this embodiment). 
     It will be obvious to one with ordinary skill in the related art that the structure of drive information zone  709   a  in this embodiment of the invention could be structured as shown in any of  FIG. 4 ,  FIG. 16 ,  FIG. 17 , and  FIG. 18 . 
     Embodiment 3 
       FIG. 13  shows the structure of a single-side, two-layer optical disc according to a third embodiment of the present invention. 
       FIG. 15  shows the logic structure of a two-layer optical disc according to this embodiment of the invention. 
     The prerecorded area  801   a  of the first recording layer stores, for example, identification data for the two-layer optical disc recorded in a wobble track, embossed pits, or wobbled embossed pits. 
     The prerecorded area  801   a  includes a protected zone  803   a  as a buffer, and a control data zone  804   a . The control data zone  804   a  stores at least one of the following as optical disc identification information: disc type, disc capacity, disc structure, channel bit, data zone address information, data rate, maximum playback power, recording power information, recording pulse position information, and disc-specific information. 
     The information recorded in the control data zone  804   a  on the first recording layer could be information relating only to the first recording layer, or information relating to the first recording layer and information relating to the second recording layer. 
     The prerecorded area  801   b  on the second recording layer is located at the same radial position as the prerecorded area  801   a  of the first recording layer. 
     This prerecorded area  801   b  also includes a protected zone  803   b  as a buffer, and a control data zone  804   b . The control data zone  804   b  stores at least one of the following as optical disc identification information: disc type, disc capacity, disc structure, channel bit, data zone address information, data rate, maximum playback power, recording power information, recording pulse position information, and disc-specific information. 
     The information recorded in the control data zone  804   b  on the second recording layer could be information relating only to the first recording layer, or information relating to the first recording layer and information relating to the second recording layer. The control data zones  804   a  and  804   b  could store the same information. 
     The data recording area  802   a  on the first recording layer includes a protected zone  805   a  in which data is not recorded, a buffer zone  806   a , a drive information zone  807   a  used for storing information such as optical disc characteristics, a buffer zone  808   a , a test zone  809   a  used for testing the optical disc, a reserved zone  810   a  for future developments, a user data recording zone  811   a  for recording user data, a buffer zone  812   a , a reserved zone  813   a  enabling future development, a buffer zone  814   a , and a protected zone  815   a  in which data is not recorded. 
     If the track pitch differs in the prerecorded area  801   a  and data recording area  802   a , the protected zone  805   a  can be used as a track pitch transition area. 
     The data recording area  802   b  on the second recording layer likewise includes a protected zone  805   b  in which data is not recorded and which can be used as a track pitch transition area when the track pitch differs in the prerecorded area  801   b  and data recording area  802   b . The protected zone  805   b  on the second recording layer is located at the same radial position as the protected zone  805   a  on the first recording layer. 
     The data recording area  802   b  on the second recording layer likewise includes a reserved zone  807   b  in which data is not recorded. This reserved zone  807   b  is located at the same radial position as the drive information zone  807   a  on the first recording layer. 
     The data recording area  802   b  of the second recording layer also includes a reserved zone  810   b  allowing for future developments. This reserved zone  810   b  is located at the same radial position as, or at a radial position on the inside circumference side of, the test zone  809   a  on the first recording layer. 
     The data recording area  802   b  on the second recording layer also includes a user data recording zone  811   b  for recording user data, another buffer zone  812   b , another reserved zone  813   b  enabling future developments, a buffer zone  814   b , and a protected zone  815   b  to which data is not recorded. Each of these zones is located at the same radial position as the corresponding user data recording zone  811   a , buffer zone  812   a , reserved zone  813   a  enabling future developments, buffer zone  814   a , and protected zone  815   a  to which data is not recorded in the first recording layer. 
     When the disc is spun for reading and writing along the tracks on the first and second recording layers, the read/write direction of the tracks on the first recording layer is from inside to outside circumference as indicated by arrow  816   a  in  FIG. 15 , and the read/write direction of the tracks on the second recording layer is from outside to inside circumference as indicated by arrow  816   b.    
     Because the control data zones are located at the same radial position in the first and second recording layers with the disc arrangement according to this embodiment of the invention, the control data can be read from either recording layer, and the identification information can thus be acquired more quickly. 
     Furthermore, because a reserved zone  807   b  where data is not recorded is located on the second recording layer at the same radial position as the drive information zone  807   a  on the first recording layer, the drive information zone  807   a  can be read or written through a second recording layer that is always in the same state (that is, blank in this embodiment). As a result, the drive information can be read and written consistently and stably. 
     Yet further, because a reserved zone where data is not recorded is disposed at the same radial position as at least part of the test zone with the disc format according to the present invention, disc testing can be conducted under consistently stable conditions through another layer that is always in the same state (that is, blank in this embodiment). 
     It will be obvious to one with ordinary skill in the related art that the structure of drive information zone  807   a  in this embodiment of the invention could be structured as shown in any of  FIG. 4 ,  FIG. 16 ,  FIG. 17 , and  FIG. 18 . 
     Embodiment 4 
       FIG. 16  shows the structure of the drive information zone  214  shown in  FIG. 2  according to a fourth embodiment of the present invention.  FIG. 17  and  FIG. 18  show variations of the same. 
     As shown in  FIG. 16 , each cluster is segmented into a plurality of sectors (32 sectors in this example) as described in the first embodiment. This fourth embodiment differs from the first embodiment in that in addition to the drive-specific information, disc-specific information S(i) is recorded to one sector. 
     This disc-specific information S(i) includes, for example, the last address at which user data is recorded, and the last address that was used in the test zone. Drive-specific information D( 1 ) is recorded to sector # 1  in cluster # 1 , and disc-specific information S( 1 ) is recorded to sector # 2  in cluster # 1 . This disc-specific information S( 1 ) contains the last address information following the end of the recorded user data, and the last address information identifying the last address used in the test zone. 
     When the same disc is loaded in a second optical disc drive, the drive-specific information D( 2 ), D( 1 ) is recorded to sector # 1  and sector # 2 , respectively, in cluster # 2 , and disc-specific information S( 2 ) is recorded to sector # 3 , cluster # 2 . This disc-specific information S( 2 ) records the updated last address information following the address to which the user data was appended, and the updated last address information identifying the last address used in the test zone. 
     One sector in each cluster is thus used to record disc-specific information. The sector to which the disc-specific information is recorded could be the last used sector in each cluster (as shown in  FIG. 16 ), the first sector in each cluster (as shown in  FIG. 17 ), or some other desirable sector. 
     The disc-specific information could be updated each time new drive-specific information is added, or each time a specific amount of data is written to the user data recording area.  FIG. 18  shows a case in which the disc-specific information is updated each time a specific amount of data is written to the user data recording area. 
     Referring to  FIG. 18 , when the disc is loaded in a second optical disc drive, drive-specific information D( 2 ) and D( 1 ) is recorded to sector # 2  and sector # 3  of cluster # 2 , and the disc-specific information S( 2 ) is written to sector # 1  of cluster # 2 . This disc-specific information S( 2 ) records the updated last address information following the address to which the user data was appended, and the updated last address information identifying the last address used in the test zone. 
     If a specified volume F of user data is then recorded to the disc using the same optical disc drive, the same drive-specific information D( 2 ), D( 1 ) is copied from cluster # 2  to sector # 2  and sector # 3  of cluster # 3 , and the updated disc-specific information S( 3 ) is recorded to sector # 1  of cluster # 3 . 
     This specified volume F is
 
 F= 2 S/G  
 
where G is the number of clusters (G=2048, for example), and S is the capacity of the user data recording area. In this case, the disc-specific information S(i) will be updated G/2 times even if the entire user data recording area is written by the same optical disc drive. Half of the total number of clusters will be left unused in the drive information area, and can be used to record additional access information.
 
     The specified volume F could, of course, be otherwise defined, including:
 
 F=S/G,  
 
 F= 3 S/G,  
 
 F= 4 S/G , or
 
 F= 5 S/G.  
 
     Referring to  FIG. 17 , when the number of drive-specific information records D(n) increases to 31, D( 1 ) to D( 31 ) are written from sector # 32  to sector # 2  in the chronological order in which the data was generated, and the most recent data D( 31 ) is written to sector # 2 . The disc-specific information S(i) is recorded in sector # 1 . 
     By thus structuring the drive information area  901  so that the so that data is updated by appending to unrecorded areas of the disc, the method of the present invention is not limited to use with rewritable optical disc media, and can also be used with write-once optical disc media. 
     Furthermore, because both drive-specific information and disc-specific information are recorded in one cluster (ECC block), both the drive-specific information and disc-specific information can be updated by updating only one cluster. The drive-specific information can therefore be used efficiently with particularly noticeable benefit in write-once optical discs that can only be recorded once. 
     A plurality of recording/playback condition records are recorded to an optical disc according to the present invention chronologically in the order in which the entries are recorded to the disc. As a result, the most recently acquired recording/playback conditions are always contained in the drive information. 
     Furthermore, in a multilayer disc according to the present invention the area of one layer overlapping the drive information area in another layer is left unrecorded, thereby assuring that the drive information can always be read under stable conditions. 
     The present invention is based on the previously filed Japanese Patent Applications 2002-192192 and 2002-310094, the content of which is hereby incorporated by reference. 
     Although the present invention has been described in connection with the preferred embodiments thereof with reference to the accompanying drawings, it is to be noted that various changes and modifications will be apparent to those skilled in the art. Such changes and modifications are to be understood as included within the scope of the present invention as defined by the appended claims, unless they depart therefrom.