Abstract:
A ROM-RAM recording medium includes a ROM portion in which main information is recorded by a physical change on an optically transparent substrate and a RAM portion formed on the ROM portion as a recording layer that allows writing of main information at least once. The ROM portion is provided with a sub-code area for recording sub-information. A sub-code area for recording sub-information is provided in the RAM portion arranged at physically substantially the same position as the sub-code area of the ROM portion in a track direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a U.S. continuation application, filed under 35 USC 111(a) and claiming the benefit under 35 USC 120 and 365(c), of PCT application PCT/JP2002/008833, filed Aug. 30, 2002. The foregoing application is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention generally relates to optical recording media, and more particularly, to a ROM-RAM recording medium that includes: a ROM portion having an optically transparent substrate on which main information is recorded by physical change such as an irregularity formed as, for example, pits; and a RAM portion formed on the ROM portion as a recording layer that allows writing of main information at least once, wherein a sub-code region for recording sub-information is provided in the ROM portion, and to a storage device for such a ROM-RAM recording medium.  
         [0004]     2. Description of the Related Art  
         [0005]     Conventional media having both ROM (Read-Only Memory) part and RAM (Random Access Memory) part therein include, for example, a so-called partial ROM medium. In the ROM portion, information is recorded by physical change such as an irregularity formed as, for example, pits. In the RAM portion, a recording layer that allows writing or overwriting is formed. In the partial ROM medium, the ROM portion and the RAM portion are formed on separate regions of a single disk.  
         [0006]     In such a medium having both ROM portion and RAM portion on a single optical disk, synchronization flags for establishing synchronization between signals reproduced from the ROM portion and the RAM portion are embedded in data recorded in the ROM portion and the RAM portion of the optical disk. When reproducing data, the synchronization flags are recognized by a read channel and data reproduced from the ROM portion and the RAM portion are combined again to perform reproduction.  
         [0007]     However, as mentioned above, in a partial ROM medium, a ROM portion and a RAM portion are formed on separate regions of a single optical disk. Accordingly, in such a system that reproduces data recorded in the ROM portion and the RAM portion, and combines and uses the data, it is necessary to access the ROM portion and the RAM portion by an optical pickup and reproduce data from each of the regions. Thus, it is necessary for the optical pickup to constantly move between and access the ROM portion and the RAM portion. Hence, there is a significant time delay until data reproduced from the ROM portion and the RAM portion and to be synchronized are sent from the optical pickup to the read channel. Consequently, reliability of the reproduced data has been low.  
         [0008]     Additionally, in a rewritable medium, access history of regions to be accessed and user information such as kinds of registration information are written and recorded in control tracks. However, since it is impossible to secure a large capacity for the control tracks, the amount of information that can be written therein has been limited.  
         [0009]     On the other hand, in a so-called concurrent ROM-RAM medium, which includes a ROM portion having an optically transparent substrate on which information is recorded by physical change such as an irregularity, and a RAM portion formed on the ROM portion as a recording layer and allowing writing at least once, it is possible to concurrently handle data of the ROM portion and the RAM portion.  
         [0010]     As for concurrent ROM-RAM media, a concurrent ROM-RAM optical disk that allows simultaneous reproduction of the ROM portion and the RAM portion is described in, for example, an article titled “Feasibility Study of Concurrent ROM-RAM Optical Disk” in The Journal of the Institute of Television Engineers of Japan, Vol. 46, No. 10, pp. 1319-1324, published in 1992.  
         [0011]     However, in order to concurrently handle data of the ROM portion and that of the RAM portion, it is necessary to recognize relationships between the data recorded in the ROM portion and that in the RAM portion with a simple method.  
         [0012]     Additionally, in a concurrent ROM-RAM medium, general contents such as a movie and music are recorded in the ROM portion, and in many cases, the recorded contents are used by multiple users. Hence, in terms of data protection and copyright protection, methods are required for managing access history and the like, recording user information such as various kinds of registration information, and identifying users who desire to use the concurrent ROM-RAM medium. It is necessary that such methods can be performed as simply as possible.  
       SUMMARY OF THE INVENTION  
       [0013]     A general object of the present invention is to provide an improved and useful concurrent ROM-RAM medium and storage device therefor in which one or more of the above-mentioned problems are eliminated.  
         [0014]     Another and more specific object of the present invention is to provide a concurrent ROM-RAM medium that allows recording of, for example, user information and relationships between main information or data recorded in the ROM portion and that in the RAM portion with a simple method, and to provide a storage device that records information on and/or reproduces information from such a concurrent ROM-RAM medium.  
         [0015]     In order to achieve the above-mentioned objects, according to one aspect of the present invention, there is provided a ROM-RAM recording medium including a ROM portion in which main information is recorded by a physical change on an optically transparent substrate and a RAM portion formed as a recording layer on the ROM portion and allowing writing of main information at least once, the ROM portion being provided with a sub-code area for recording sub-information, 
        wherein a sub-code area for recording sub-information is provided in the RAM portion arranged at physically substantially the same position as that of a sub-code area of the ROM portion in a track direction.        
 
         [0017]     According to the above-mentioned aspect of the present invention, by providing a sub-code area in the RAM portion at a position close to or substantially the same as a sub-code area of the ROM portion, it is possible to add various kinds of management information to the data of the RAM portion.  
         [0018]     In an embodiment of the present invention, information for associating the main information of the ROM portion with main information of the RAM portion may be recorded in the sub-code area of the RAM portion.  
         [0019]     With the above-mentioned embodiment, since the association information is recorded in the sub-code area of the RAM portion, it is unnecessary to re-access the lead-in area during data reproduction. Hence, it is possible to perform seamless reproduction having high reliability.  
         [0020]     In an embodiment of the present invention, the main information of the RAM portion associated with the main information of the ROM portion may be recorded at a position seamlessly reproduced when reading the main information of the RAM portion.  
         [0021]     With the above-mentioned embodiment, it is possible to record the data of the RAM portion associated with the data of the ROM portion in the same recording track as the data of the ROM portion. Thus, access by a lens actuator does not occur. Hence, it is possible to perform seamless reproduction having higher reliability.  
         [0022]     In an embodiment of the present invention, user registration information may be recorded in the sub-code area provided in a lead-in area of the RAM portion, and access management information based on the user registration information may be recorded in the sub-code area provided in a data recording area of the RAM portion.  
         [0023]     With the above-mentioned embodiment, since the access management information is recorded in the sub-code area of the data part of the RAM portion, it is unnecessary to re-access the lead-in area during data reproduction. Hence, it is possible to perform seamless reproduction having high reliability while protecting data.  
         [0024]     In an embodiment of the present invention, the access management information based on the user registration information recorded in the sub-code area provided in the data recording area of the RAM portion may include the type of concurrent reproduction permission of the main information of the ROM portion and the main information of the RAM portion.  
         [0025]     With the above-mentioned embodiment, since the access management information related to the type of permission for concurrent reproduction is recorded in a sub-code area of the data part of the RAM portion, it is possible to perform reproduction in a different mode for each user in a seamless manner without accessing the lead-in area for each reproduction data.  
         [0026]     In an embodiment of the present invention, data access count information may be recorded in the sub-code area provided in the lead-in area of the RAM portion, and the data access count information may include history information of concurrent reproduction of ROM data and RAM data.  
         [0027]     With the above-mentioned embodiment, since the history information of concurrent reproduction of the data of the ROM portion and the data of the RAM portion is recorded in a sub-code area in the lead-in area, it is possible to quickly gather information.  
         [0028]     Additionally, according to another aspect of the present invention, there is provided a storage device that records information on or reproduces information from a ROM-RAM recording medium, 
        the ROM-RAM recording medium including a ROM portion in which main information is recorded by a physical change and a RAM portion formed as a recording layer on the ROM portion and allowing writing of main information at least once,     wherein a sub-code area for recording sub-information is provided in the RAM portion at substantially the same position as a sub-code area of the ROM portion in a track direction.        
 
         [0031]     According to the above-mentioned aspect of the present invention, it is possible to record information on or reproduce information from the above-mentioned ROM-RAM medium.  
         [0032]     Additionally, according to another aspect of the present invention, there is provided a storage device that records information on or reproduces information from a ROM-RAM recording medium including a ROM portion in which main information is recorded by a physical change and a RAM portion formed as a recording layer on the ROM portion and allowing writing of main information at least once, 
        the storage device including a user identification part including:     a lock generation part that generates a lock based on ROM information and RAM information;     a key generation part that generates a key based on the lock; and     a detector that detects a match between the key generated based on the lock and a key input to the storage device.        
 
         [0037]     The ROM information unique to each medium is used when allowing usage of the medium. The ROM information is known as a medium ID. For example, a lock and a key for identifying an owner are generated from the medium ID information, and the owner obtains the key when purchasing the medium. Thereby, the owner can access the medium. Since a ROM-RAM medium generally contains contents in the ROM portion thereof, it is assumable that multiple users exist. According to the above-mentioned aspect of the present invention, a lock and a key for user identification are generated based on information obtained by combining, for example, the medium ID information, which is the ROM information, and the RAM information, which is created by the owner. A user may obtain the key information from the owner by some means. Generally, the owner manages multiple media. Accordingly, it is burdensome to create locks and keys without overlapping and to manage them. With the use of information of a medium ID, which is ROM information unique to each medium, as a part of information forming the basis for generating a lock and a key, even if the owner assigns the same RAM information with respect to the same user, different locks and keys are generated for each medium. Hence, it is possible to protect data more securely.  
         [0038]     In a storage device according to an embodiment of the present invention, the ROM information and the RAM information may be recorded at physically substantially the same position in a track direction.  
         [0039]     In an embodiment of the present invention, the ROM information used for generating a lock and a key for identifying a user is not limited to a medium ID, and ROM information provided in another area may be used. For example, RAM information created by the owner may be recorded in a sub-code area for recording the ROM information and a sub-code area of the RAM portion physically substantially the same as or close to the sub-code area for recording ROM information, and a lock and a key for user identification may be generated based on the ROM information and the RAM information read by ROM-RAM concurrent reproduction. As mentioned above, information forming the basis for generating a lock and a key may be recorded in any area on a medium. Hence, confidentiality of the recording position of a lock and a key is increased, and unnecessary accesses for user identification are further decreased.  
         [0040]     Other objects, features and advantages of the present invention will become more apparent from the following detailed description when read in conjunction with the following drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0041]      FIG. 1  is a schematic diagram showing a concurrent ROM-RAM medium according to the present invention;  
         [0042]      FIG. 2  is a schematic diagram showing recording marks of the concurrent ROM-RAM medium according to the present invention;  
         [0043]      FIG. 3  is a cross-sectional view of the concurrent ROM-RAM medium according to the present invention;  
         [0044]      FIG. 4  is a block diagram showing a ROM-RAM medium and an exemplary structure of a recording/reproducing apparatus therefor;  
         [0045]      FIG. 5  is a table showing a LD feedback signal, a ROM reproduction signal, and a RAM reproduction signal for each operational mode;  
         [0046]      FIG. 6  is a schematic diagram showing the structure of a sub-code of a data part of a compact disk;  
         [0047]      FIG. 7A  is a schematic diagram showing an exemplary structure of a sub-code of a ROM portion;  
         [0048]      FIG. 7B  is a schematic diagram showing an exemplary structure of a sub-code of a RAM portion;  
         [0049]      FIG. 8A  is a schematic diagram showing an exemplary structure of the sub-code of the ROM portion;  
         [0050]      FIG. 8B  is a schematic diagram showing an exemplary structure of the sub-code of the RAM portion;  
         [0051]      FIG. 9  is a schematic diagram showing the format of a signal recorded in the ROM portion;  
         [0052]      FIG. 10  is a schematic diagram showing the format of a signal recorded in the RAM portion;  
         [0053]      FIG. 11A  is a schematic diagram showing a simple example of the reproduction state of a ROM-RAM medium;  
         [0054]      FIG. 11B  is a schematic diagram showing a simple example of the reproduction state of a ROM-RAM medium;  
         [0055]      FIG. 12A  is a flowchart for explaining the case where replacement information is recorded in a lead-in area;  
         [0056]      FIG. 12B  is a flowchart for explaining the case where the replacement information is recorded in the sub-code area of the data part of the RAM portion;  
         [0057]      FIG. 13  is a schematic diagram showing the format of a signal recorded in the ROM portion;  
         [0058]      FIG. 14  is a schematic diagram showing the format of a signal recorded in the RAM portion;  
         [0059]      FIG. 15  is a schematic diagram showing a reproduction process with respect to a user A;  
         [0060]      FIG. 16  is a schematic diagram showing a reproduction process with respect to a user B;  
         [0061]      FIG. 17  is a schematic diagram showing a reproduction process with respect to a user C;  
         [0062]      FIG. 18  is a schematic diagram showing an owner identification part;  
         [0063]      FIG. 19  is a schematic diagram showing a user identification part;  
         [0064]      FIG. 20  is a schematic diagram showing the user identification part; and  
         [0065]      FIG. 21  is a schematic diagram showing signal processing performed by a main controller  415  shown in  FIG. 4  in order to identify a user according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0066]     A description is given below of embodiments for implementing the present invention with reference to the drawings.  
         [0067]      FIG. 1  shows a concurrent ROM-RAM medium  100  according to the present invention.  FIG. 2  shows recording marks on the concurrent ROM-RAM medium  100  according to the present invention.  FIG. 3  is a cross-sectional view of the concurrent ROM-RAM medium  100  according to the present invention.  
         [0068]     The concurrent ROM-RAM medium  100  according to the present invention, which medium is shown in  FIG. 1 , is a ROM-RAM optical disk. The concurrent ROM-RAM medium  100  includes tracks formed thereon in a spiral manner, and includes a lead-in area  101 , a data recording area  102 , and a lead-out area  103  from the inner tracks to the outer tracks. In the ROM-RAM optical disk shown in  FIG. 1 , as in a compact disk (CD), the lead-in is formed in the area within approximately 50 mm radium from the center. Phase pits are formed over substantially the entire surfaces of the lead-in area  101 , the data recording area  102 , and the lead-out area  103 , and a recording layer is formed on the phase pits.  
         [0069]      FIG. 2  shows the recording marks recorded on the concurrent ROM-RAM optical disk  100  according to the present invention. The ROM-RAM optical disk  100  includes both marks formed by the above-mentioned pits such as marks  201  and  202 , and marks recorded in the recording layer such as marks  203 ,  204 ,  205  and  206 . A line segment AB indicates a line along a cross section that is perpendicular to the tracks.  
         [0070]     The data areas to be recorded may be somewhat shifted in a track direction between the ROM portion and the RAM portion.  
         [0071]      FIG. 3  is a cross-sectional view of the ROM-RAM optical disk  100  according to the present invention. The ROM-RAM optical disk  100  according to the present invention includes a substrate  301 , a dielectric layer  302 , a magneto-optical recording layer (perpendicular magnetic layer)  303 , a dielectric layer  304 , a reflection layer  305 , and an overcoat layer  306 . The signs A and B in  FIG. 3  correspond to the end A and the end B of the line segment shown in  FIG. 2 , respectively.  FIG. 3  is the cross-sectional view along the line segment AB shown in  FIG. 2 . Pits  201  and  202  in  FIG. 3  correspond to the marks  201  and  202  in  FIG. 2 , respectively. In addition, arrows  203  through  206  in  FIG. 3  indicate the magnetizing directions in the magneto-optical recording layer  303  of the recording marks  203  through  206  in  FIG. 2 , respectively. In this embodiment, the magnetizing directions are perpendicular to the magneto-optical recording layer  303 .  
         [0072]     Next, a description is given of an embodiment of a recording/reproducing apparatus for the concurrent ROM-RAM optical disk  100  according to the present invention.  
         [0073]      FIG. 4  shows an embodiment of a ROM-RAM medium  417  and a recording/reproducing apparatus  400  therefor. The recording/reproducing apparatus  400  in  FIG. 4  includes a laser diode LD  401 , a collimator lens  410 , a deflection beam splitter  411 , a condenser lens  412 , an APC photodetector  413 , an amplifier  414 , a main controller  415 , an objective lens  416 , a motor  418 , a second deflection beam splitter  419 , a condenser lens  420 , a divided-by-four photodetector  422 , a focus error signal (FES) generation circuit  423 , a tracking error signal (TES) generation circuit  424 , a 2-beam Wollaston prism  426 , a condenser lens  427 , a divided-by-two photodetector  428 , a summing amplifier  429 , a differential amplifier  430 , a laser diode (LD) driver  431 , amplifiers  432  and  433 , a motor driver  434 , a focus and track actuator  435 , a focus and track actuator driver  436 , a magnetic head driver  437 , a magnetic head  438 , an interface  439 , and an input/output (I/O) circuit  440 . The input/output circuit  440  is connected to an input/output device  441 .  
         [0074]     When recording information on a recording layer of the ROM-RAM medium  417 , information to be recorded is input to the main controller  415  from the input/output device  441  via the input/output circuit  440  and the interface  439 . The main controller  415  transmits a recording signal to the laser diode driver  431  and the magnetic head driver  437 . The laser diode driver  431  controls the laser diode  401  such that writing laser light is emitted therefrom. The laser light is collimated into parallel light by the collimator lens  410 . The parallel light is converged and directed onto the ROM-RAM medium  417  by the objective lens  416  in the actuator  435 . On the other hand, the magnetic head driver  437  controls the magnetic head  438  in accordance with the recording signal, thereby recording information on the recording layer of the ROM-RAM medium  417 .  
         [0075]     A ROM signal and a RAM signal are reproduced from the ROM-RAM medium  417  in the following manner.  
         [0076]     Reading laser light emitted from the laser diode  401  is collimated into parallel light by the collimator lens  410 . The parallel light is converged and directed onto the ROM-RAM medium  417  by the objective lens  416  in the actuator  435 . Reflected light from the ROM-RAM medium  417  is directed to the condenser lens  412  and the second deflection beam splitter  419  by means of the deflection beam splitter  411 . The second deflection beam splitter  419  divides and transmits the entering light to the condenser lens  420  and the 2-beam Wollaston prism  426 .  
         [0077]     The light directed to the condenser lens  420  enters the divided-by-four photodetector  422 . Based on the output of the divided-by-four photodetector  422 , the focus error signal generation circuit  423  and the track error signal generation circuit  424  generate and transmit, to the main controller  415 , a focus error signal and a tracking error signal, respectively. A servo controller (servo cont) in the main controller  415  transmits a focus and track control signal to the focus and track actuator driver  436 . The actuator  435  is driven by the focus and track actuator driver  436 , thereby performing position control of the actuator  435 .  
         [0078]     On the other hand, the light entering the 2-beam Wollaston prism  426  passes through the condenser lens  427  and enters the divided-by-two photodetector  428 . The outputs of the divided-by-two photodetector  428  pass through the amplifiers  432  and  433 . Then, a ROM 1  signal, which is a phase pit signal, is generated by the summing amplifier  429 , and a RAM signal, which is a MO signal, is generated by the differential amplifier  430 . The ROM 1  signal and the RAM signal are transmitted to the main controller  415 .  
         [0079]     Control by the laser diode driver  431  is performed in the following manner. The reflection light from the ROM-RAM medium  417 , which is reflected by the deflection beam splitter  411 , is converged by the condenser lens  412  and enters the APC photodetector  413 .  
         [0080]     An output signal of the APC photodetector  413  is amplified by the amplifier  414 . An output signal of the amplifier  414  is a ROM 2  signal, and an output signal of the summing amplifier  429  is the ROM 1  signal.  
         [0081]     In addition, a control signal LD CONT for controlling the laser diode  401  is output from the main controller  415  to the laser diode driver  431 . The control signal LD CONT, which is for controlling the laser diode  401  and is output from the main controller  415 , is a basic power instruction for reading or writing.  
         [0082]     Here, control of the laser diode by the ROM 2  signal, which is obtained by amplifying the signal output from the APC photodetector  413 , and the ROM 1  signal, which is the output signal from the summing amplifier  429 , is referred to as LD feedback.  
         [0083]      FIG. 5  shows a LD feedback signal, a ROM reproduction signal and a RAM reproduction signal for each operational mode. In a mode in which the ROM and the RAM are concurrently reproduced, the ROM 1  signal is used as the LD feedback signal, the ROM signal is detected from the ROM 2  signal, and the RAM signal is constantly detected from the RAM signal, which is the output of the differential amplifier  430 . In a mode in which only the ROM is reproduced, the ROM 2  signal is used as the LD feedback signal, and the ROM signal is detected from the ROM 1  signal. In a mode in which only the RAM is reproduced, the ROM 1  signal is used as the LD feedback signal, and the RAM signal is constantly detected from the RAM signal, which is the output of the differential amplifier  430 . In a mode in which the ROM is reproduced while concurrently writing to the RAM, the ROM 2  signal is used as the LD feedback signal, and the ROM signal is detected from the ROM 1  signal.  
         [0084]     Next, a description is given of a mode in which the ROM and the RAM are concurrently reproduced.  
         [0085]     In the mode in which the ROM and the RAM are concurrently reproduced, a MO signal recorded in the recording layer, which is formed on the phase pits, is read. Hence, the RAM signal, which is the output of the differential amplifier  430  shown in  FIG. 4 , is superimposed with noise components under the influence of the phase pits formed under the recording layer. For this reason, the ROM 1  signal, which is the output of the summing amplifier  429 , is fed back to the laser diode driver  431 , thereby controlling the luminescence intensity of the laser diode  401  to be modulated in such a manner that the influence of the phase pits is cancelled. Ideally, after such a process is performed on the ROM 1  signal, the amplitude thereof becomes 1/control loop gain of the LD feedback loop. That is, the ROM 1  signal becomes a substantially flat signal.  
         [0086]     On this occasion, the APC photodetector  413  is detecting the modulation degree of the luminescence intensity of the laser diode  401 . Accordingly, the output signal of the APC photodetector  413 , that is, the amplified ROM 2  signal, is a reproduction signal of the phase pits. In the aforementioned manner, it is possible to concurrently detect the ROM signal from the ROM 2  signal, while detecting the RAM signal.  
         [0087]      FIG. 6  shows the structure of a sub-code  600  of a data part of a compact disk. The sub-code  600  includes a synchronization signal  601 , a control signal  602 , an address  603 , a data part  604 , and a CRC part  606 . The data part  604  is formed by P, Q, R, S, T, U, V and W channels.  
         [0088]     A sub-code area, having the same structure as the sub-code  600  of the data part of the compact disk shown in  FIG. 6 , is also provided in each of the ROM portion and the RAM portion of the ROM-RAM medium.  FIG. 7A  shows an exemplary structure of a sub-code of the ROM portion.  FIG. 7B  shows an exemplary structure of a sub-code of the RAM portion.  FIG. 8A  shows an exemplary structure of a sub-code of the ROM portion.  FIG. 8B  shows an exemplary structure of a sub-code of the RAM portion. In  FIGS. 7A, 7B ,  8 A and  8 B, those parts that are the same as those corresponding parts in  FIG. 6  are designated by the same reference numerals. According to the specification of a compact disk, since the methods for using the P and Q channels of the sub-code are already determined, the other information is recorded in the R through W channels. For example, a lock for identifying a user may be recorded in the data part of the sub-code of the ROM portion. On the other hand, a key, an owner ID, a password and the like for identifying a user may be recorded in the data part of the sub-code of the RAM portion.  
         [0089]     A lock may be further recorded in the data part of the sub-code of the RAM portion.  
         [0090]     In the present invention, in the ROM-RAM medium, information indicating association with the data of the ROM portion is recorded in any of the R through W channels of the sub-code  600  of the data part of the RAM portion.  
         [0091]     Next, referring to  FIGS. 9, 10 ,  11 A and  11 B, a description is given of an embodiment of ROM-RAM data association according to the present invention. This embodiment may be applied to, for example, the case where an electronic publication is modified afterward.  
         [0092]      FIG. 9  shows the format of a signal recorded in the ROM portion. The data recorded in the ROM portion are formed by blocks  710 ,  720 ,  730 ,  740  and  750 , for example. The blocks  710 ,  720 ,  730 ,  740  and  750  are formed by synchronization patterns (sync patterns)  711  through  751 , sub-code parts  712  through  752 , and user data parts  713  through  753 , respectively. The data part  604  of the sub-code  600  shown in  FIG. 6  corresponds to each of the sub-code parts  712  through  752 . DATA ROM 1  is recorded in the user data part  713 , DATA ROM 2  is recorded in the user data part  723 , DATA ROM 3  is recorded in the user data part  733 , and DATA ROMX is recorded in the user data part  753 . At the time of manufacturing of a ROM-RAM medium, only the ROM portion is formed on the ROM-RAM medium, and the RAM portion remains unformed.  
         [0093]      FIG. 10  shows the format of a signal recorded in the RAM portion after the medium is manufactured. Data recorded in the RAM portion are formed by blocks  810 ,  820 ,  830 ,  840  and  850 , for example. The blocks  810  through  850  are formed by synchronization patterns (sync patterns)  811  through  851 , sub-code parts  812  through  852 , and user data parts  813  through  853 , respectively. The data part  604  of the sub-code  600  shown in  FIG. 6  corresponds to each of the sub-code parts  812  through  852 . The blocks  810  through  850  of the RAM portion are recorded at positions corresponding to the blocks  710  through  750  of the ROM portion, respectively. In  FIG. 10 , DATA RAM 2  is recorded in the user data part  823 , and the sub-code part  822  records therein information (indicated by EX in  FIG. 10 ) representing reproduction by replacing the DATA ROM 2  with the DATA RAM 2 .  
         [0094]      FIGS. 11A and 11B  show reproduction states of a ROM-RAM medium including a ROM portion having the data shown in  FIG. 9  and a RAM portion having the data shown in  FIG. 10 .  
         [0095]      FIG. 11A  shows, for example, the case of reproducing an electronic publication with no modification. In this case, since data are not stored in the RAM portion, the data recorded in the user data parts  713  through  753  in the blocks  710  through  750 , respectively, are sequentially reproduced as shown in  FIG. 11A . Thus, in the case of  FIG. 11A , the DATA ROM 1  ( 901 ), the DATA ROM 2  ( 902 ), the DATA ROM 3  ( 903 ), and the DATA ROMX ( 904 ) are sequentially reproduced.  
         [0096]     On the other hand,  FIG. 11B  shows the case where the original electronic publication is modified, and the data DATA RAM 2 , corresponding to the modification, is recorded in the data part  823  of the RAM portion. In this case, similar to the above-mentioned case shown in  FIG. 11A , the DATA ROM 1  ( 1001 ) is reproduced from the user data part  713  in the block  710  of the ROM portion. However, next, the DATA RAM 2  ( 1002 ) is reproduced from the user data part  823  of the RAM portion based on the information (indicated by EX in  FIG. 10 ) that is recorded in the sub-code  822  of the RAM portion and represents replacement of the DATA ROM 2  with the DATA RAM 2 . Subsequently, as in the case shown in  FIG. 11A , the DATA ROM 3  ( 1003 ) and the DATA ROMX ( 1004 ) are sequentially reproduced.  
         [0097]     In this case, as mentioned above, it is preferable that the DATA RAM 2  be recorded in the user data part  823  of the RAM portion so that the DATA RAM 2  is recorded at physically the same position as the user data part  723  of the ROM portion, where the DATA ROM 2  is recorded.  
         [0098]     In fields of application such as video electronic publishing, there exists a plurality of such portions in data reproduced in a seamless manner, that is, without track jump.  
         [0099]      FIG. 12A  shows an access method in the case where the replacement information is recorded in the lead-in area  101  shown in  FIG. 1 . When reproduction is directed in step  1101 , the recording/reproducing apparatus  400  shown in  FIG. 4  accesses in step S 1102  the lead-in area  101  of the RAM portion shown in  FIG. 1 . In step  1102 , reproduction data information and association information, which are recorded in the lead-in area  101  of the RAM portion, are read, and data blocks of the RAM portion to be reproduced are determined based on the information. In step  1103 , the data blocks are accessed to reproduce data. After a predetermined amount of data are reproduced, the lead-in area  101  of the RAM portion shown in  FIG. 1  is accessed again in step S 1104 . The above-mentioned operation of step  1102  is repeated. Finally, in step  1105 , the reproduction of data ends.  
         [0100]     In the aforementioned manner, when the replacement information is recorded in the lead-in area  101  shown in  FIG. 1 , the data part  102  and the lead-in area  101 , which are shown in  FIG. 1 , are frequently and repeatedly accessed. Thus, it becomes possible to perform seamless reproduction.  
         [0101]      FIG. 12B  shows an access method in the case where the replacement information is recorded in the sub-code area of the data part of the RAM portion according to the present invention.  
         [0102]     Referring to  FIG. 12 , when reproduction is directed in step  1201 , the recording/reproducing apparatus  400  shown in  FIG. 4  accesses in step  1202  the lead-in area  101  of the RAM portion shown in  FIG. 1 . In step  1202 , reproduction data information recorded in the lead-in area  101  of the ROM portion is read, and data blocks of the ROM portion to be reproduced are determined based on the information. In step  1203 , the data blocks of the ROM portion are accessed to reproduce data of the ROM part. The reproduction is continued while reproducing the data of the ROM portion and reproducing the replacement information recorded in the sub-code part of the RAM portion. The data recorded in the RAM portion are reproduced in accordance with the replacement information. When reproduction of data corresponding to a replacement part of the RAM portion ends, the data of the ROM portion is reproduced again. Finally, in step  1204 , the reproduction of data ends.  
         [0103]     As mentioned above, in the present invention, since the replacement information is recorded in the sub-code area of the data part of the RAM portion, unlike  FIG. 12A , the lead-in area  101  is not unnecessarily accessed during reproduction of data.  
         [0104]     Next, a description is given of another embodiment of the present invention. In this embodiment, access management information with respect to users is recorded in the sub-code part, and different reproduction can be performed for each user based on the access management information. User registration information is recorded in a sub-code area provided in the lead-in area of the RAM portion. In this embodiment, three users A, B and C are registered, for example. It is also possible to record, in the sub-code area provided in the lead-in part of the RAM part, the number of times the ROM portion and the RAM portion are accessed by a user, and history information such as the number of times the ROM portion and the RAM portion are concurrently reproduced. User management is simplified by recording such information in the sub-code area provided in the lead-in area of the RAM portion.  
         [0105]     In  FIGS. 13 and 14 , those parts that are the same as those corresponding parts in  FIGS. 9 and 10  are designated by the same reference numerals. In this embodiment, access management is performed for each of the three registered users A, B and C in accordance with the access management information based on the user registration information.  
         [0106]     Referring to  FIG. 14 , the access management information with respect to the users A, B and C is recorded in the sub-code parts  812 ,  822  and  832  of the RAM portion, respectively. Here, “A” “B” and “-” recorded in the sub-code part  812  of the RA portion are information representing the types of concurrent reproduction permission: the users “A” and “B” can reproduce the DATA RAM 1  recorded in the data part  813 , but the user “C” cannot reproduce the same. “A”, “-” and “-” recorded in the sub-code part  822  of the RAM portion represent that the user A can reproduce the DATA RAM 2  recorded in the data part  823 , but the users B and C cannot reproduce the same. Further, “-”, “-” and “-” recorded in the sub-code parts  842  and  852  of the RAM portion represent that the users A, B and C cannot reproduce the data recorded in the data parts  843  and  853 .  
         [0107]      FIGS. 15, 16  and  17  show reproduction processes for the users A, B and C, respectively. As shown in  FIG. 15 , it is possible for the user A to concurrently reproduce the ROM portion and the RAM portion in the parts of the DATA ROM 1  ( 1501 ) and the DATA RAM 1  ( 1511 ), the DATA ROM 2  ( 1502 ) and the DATA RAM 2  ( 1512 ), and the DATA ROM 3  ( 1503 ) and the DATA RAM 3  ( 1513 ). As shown in  FIG. 16 , it is possible for the user B to concurrently reproduce the ROM portion and the RAM portion in the part of the DATA ROM 1  ( 1501 ) and the DATA RAM 1  ( 1511 ). On the other hand, as shown in  FIG. 17 , the user C can reproduce only the ROM portion from the DATA ROM 1  ( 1501 ) to the DATA ROMX ( 1505 ), and reproduction of the RAM portion is prohibited for the user C. In the aforementioned manner, by recording the access management information for users in the sub-code parts of the data part of the RAM portion, it is possible to seamlessly perform reproduction in a different mode for each of the users without accessing the lead-in area for each reproduction data unit.  
         [0108]      FIGS. 18, 19  and  20  show an owner of a ROM-RAM medium and user identification means. The user identification means are performed by the recording/reproducing apparatus for a ROM-RAM medium, which apparatus is described above with reference to  FIG. 4 .  
         [0109]      FIG. 18  shows an embodiment for generating a key for identifying the owner of a ROM-RAM medium to which a medium ID is added. The medium ID is ROM data unique to a ROM-RAM medium.  
         [0110]     In step S 1801 , means for generating a key for identifying the owner of a ROM-RAM medium read, from the ROM-RAM medium, a medium ID, which is ROM data unique to the ROM-RAM medium. In step S 1802 , by assuming the read medium ID as a lock, the key is generated. In step S 1803 , when the medium is purchased by a user, the key can be obtained. Thereafter, when the recording/reproducing apparatus requests an input of owner information upon reproduction of the ROM-RAM medium, the owner can continue reproduction by inputting the key.  
         [0111]     Next, a description is given of a method for generating a key for user identification according to the present invention. The method for generating a key for identifying a user of a ROM-RAM medium is performed by the main controller  415  of the recording/reproducing apparatus for a ROM-RAM medium shown in  FIG. 4 .  
         [0112]     Referring to  FIG. 19 , a description is given of a method for generating a key  1 A for a ROM-RAM medium A. In the method for generating a key for identifying a user of a ROM-RAM medium, a medium ID, which is ROM data unique to the ROM-RAM medium A, is read from the ROM-RAM medium A in step  1901 . In step  1902 , based on the read medium ID, the owner inputs RAM information  1 , which is to be recorded in the sub-code part of the RAM portion. The RAM information  1  is information for identifying the user  1 . Referring to  FIG. 4 , the RAM information  1  is input by the owner of the ROM-RAM medium A via the input/output device  441 , and is transmitted to the main controller  415  via the input/output circuit  440  and the interface  439 . In step  1903 , based on the read medium ID and the RAM information  1  input by the owner of the ROM-RAM medium A, a new lock  1 A, which is different from the medium ID, is generated. In step  1904 , the key  1 A for identifying the user  1  is generated based on the lock  1 A, which is generated based on the read medium ID and the RAM information  1 . In step  1904 , the owner is notified of the key  1 A for identifying the user  1  via the input/output circuit  440 . The key  1 A for the user  1  thus generated is notified to the user  1  from the owner. Thereby, the user  1  can obtain the key  1 A. Thereafter, when the recording/reproducing apparatus requests an input of user confirmation information upon reproduction of the ROM-RAM medium A, the user  1  can continue reproducing of the ROM-RAM medium A by inputting the key  1 A.  
         [0113]     Next, referring to  FIG. 20 , a description is given of a method for generating a key  1 B for a ROM-RAM medium B with respect to the same user  1 . In the method for generating a key for identifying a user of a ROM-RAM medium, in step  2001 , a medium ID, which is ROM data unique to the ROM-RAM medium B, is read from the ROM-RAM medium B. In step  2002 , based on the read medium ID, the owner inputs RAM information  1 , which is to be recorded in the sub-code part of the RAM portion. The RAM information  1  is information for identifying the user  1 , and is the same as the RAM information  1  described with reference to  FIG. 19 . Referring to  FIG. 4 , the RAM information  1  is input by the owner of the ROM-RAM medium A via the input/output device  441 , and is transmitted to the main controller  415  via the input/output circuit  440  and the interface  439 . In step  2003 , based on the read medium ID and the RAM information  1  that is input by the owner of the ROM-RAM medium B, a new lock  1 B, which is different from the medium ID, is generated. The lock  1 B is different from the lock  1 A generated in step  1903  of  FIG. 19 . That is, even if the owner of the ROM-RAM medium B inputs the RAM information  1  with respect to the same user  1 , since the medium ID is different when the target ROM-RAM medium is different, another lock  1 B is generated. This simplifies management of users by the owner. In step  2004 , a key  1 B for identifying the user  1  is generated based on the lock  1 B, which is generated based on the read medium ID and the RAM information. In step  2004 , the owner of the ROM-RAM medium B is notified of the key  1 B for identifying the user  1  via the input/output circuit  440 . The key  1 B for the user  1  thus generated is notified to the user  1  from the owner. Thereby, the user  1  can obtain the key  1 B. Thereafter, when the recording/reproducing apparatus requests an input of user confirmation information upon reproduction of the ROM-RAM medium B, the user  1  can continue reproduction by inputting the key  1 B.  
         [0114]     As mentioned above, even if RAM information that is input by an owner in order to generate a lock and a key for a user is constantly the same such as the RAM information  1 , a different key is generated for each ROM-RAM medium, such as the key  1 A and the key  1 B. Accordingly, since the same key is not generated for different ROM-RAM media even if the user is the same, it is possible to readily protect data for each medium.  
         [0115]     In the above-mentioned embodiment, the description is given of the case where the medium ID is used as the ROM information. However, it is unnecessary to limit the ROM information, which is used for generating a lock and a key for identifying a user, to the medium ID, and ROM information provided in another area may be used. For example, RAM information created by an owner may be recorded in a sub-code area for recording ROM information and a sub-code area of the RAM portion, which sub-code area is physically the same or close to the sub-code area for recording the ROM information, and a key and a lock for user identification may be generated based on the ROM information and the RAM information that are read by ROM-RAM concurrent reproduction. As mentioned above, information forming the basis for generating a lock and a key may be recorded in any area on a medium. Accordingly, confidentiality with respect to the recording position of a lock and a key is increased, and unnecessary accesses for user identification are further decreased.  
         [0116]     Next, a description is given of a method for identifying a user according to the present invention. The method for identifying a user of a ROM-RAM medium is performed by the main controller  415  of the recording/reproducing apparatus for a ROM-RAM medium shown in  FIG. 4 .  FIG. 21  is a schematic block diagram of signal processing performed by the main controller  415  in order to identify a user according to the present invention. The ROM signal  1 , which is output to the main controller  415  from the summing amplifier  429  shown in  FIG. 4 , is input to an input part  2120 . The ROM signal  2 , which is output to the main controller  415  from the amplifier  414  shown in  FIG. 4 , is input to an input part  2121 . The RAM signal, which is output to the main controller  415  from the differential amplifier  430  shown in  FIG. 4 , is input to an input part  2122 . An input part  2123  receives an input signal from the interface  439  shown in  FIG. 4 . On the other hand, an output part  2124  outputs a signal to the interface  439  shown in  FIG. 4 .  
         [0117]     A switch  2101  is controlled to select either the ROM 1  or the ROM 2  in the main controller  415  in accordance with the embodiment described above with reference to  FIG. 5 . The selected signal, i.e., one of the ROM 1  and the ROM 2 , is transmitted to a synchronization signal detector (sync detector)  2102 , and a synchronization signal is detected. Based on the detected synchronization signal, main information and the data part of a sub-code are transmitted to and demodulated by a demodulator  2103 . The demodulated signal is input to a decoder  2107  and a key generation part  2108 .  
         [0118]     On the other hand, the RAM signal is transmitted to the synchronization signal detector  2104 , and a synchronization signal is detected. Based on the detected synchronization signal, a main signal and the data part of a sub-code are transmitted to and demodulated by a demodulator  2105 . The demodulated signal is input to the decoder  2107  and the key generation part  2108  via a delay part  2106  so as to adjust synchronization with the main information and the sub-code of the ROM portion.  
         [0119]     The decoder  2107  includes a function of recognizing the association information associating the data of the ROM portion with that of the RAM portion and the access management information of users, which information is mentioned above, and re-mixing the data. The above-mentioned function of the present invention is realized by the decoder  2107 , and data are output to the output part  2124  via a switch  2110  and transmitted to the interface  439 . The switch  2110  is controlled in the main controller  415  as to whether to select the output of the decoder  2107  or the output of a comparison part  2109 .  
         [0120]     As for owner identification and user identification, it is required to input keys that are generated in accordance with the above-mentioned method for generating a key for owner identification and method for generating a key for user identification. When an owner or a user desires to continue reproduction of a ROM-RAM medium, the owner or the user inputs the key for the ROM-RAM medium.  
         [0121]     The comparison part  2109  compares the key recorded in a sub-code of the ROM portion and the RAM portion with the key input by the owner or the user. The comparison result, that is, a match or a mismatch, is output to the output part  2124  via the switch  2110 , and is transmitted to the interface  439  shown in  FIG. 4 .  
         [0122]     The present invention is not limited to the specifically disclosed embodiments, and variations and modifications may be made without departing from the scope of the present invention.