Abstract:
An optical recording medium having a read-only storage area and a writable storage area and a recording/reproducing apparatus and method therefor. The optical recording medium is a hybrid disc having both the read-only storage area, which is suitable for mass production of information having the same contents, and the writable storage area on which data can be recorded, updated or added at a user&#39;s option. The read-only storage area has a structure that is completely compatible with a digital versatile disc read only memory (DVD-ROM) specification, and the writable storage area is compatible with the recording/reproducing characteristics of a writable DVD specification so that an existing reproducing-only apparatus can read information from the read-only storage area, and data can be recorded in the writable storage area using an apparatus obtained by minimally changing an existing recording/reproducing apparatus while maintaining the physical recording characteristics of the existing recording/reproducing apparatus.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims the benefit of U.S. Provisional Application 60/214,734, filed Jun. 29, 2000, in the U.S. Patent &amp; Trademark Office, the disclosure of which is incorporated herein by reference. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a recording medium having a read-only storage area and a writable storage area and a recording/reproducing apparatus and method therefor, and more particularly, to a recording medium having a read-only storage area complying with a digital versatile disc (DVD) specification and a writable storage area physically compatible with a DVD-writable specification and a recording/reproducing apparatus therefor. 
   2. Description of the Related Art 
   Generally, read-only optical recording media that are manufactured by injection molding have characteristics in that information is configured in the form of embossments referred to as pits so that user information is recorded on a mold, and the information is transferred during injection. Accordingly, read-only optical recording media are advantageous in increasing production efficiency compared to the case where information is recorded on a floppy disc or a magnetic recording medium and distributed. 
   However, read-only optical recording media on which users cannot record data have a problem in that data cannot be modified or added in application examples such as an encyclopedia and popular music data for accompaniment which frequently require modification of data and addition of data. 
   Meanwhile, among digital versatile disc specifications, read-only discs are defined in a digital versatile disc read only memory (DVD-ROM) specification (DVD Specification for read-only memory Part 1 version 1.0). Discs on which a user can record data are defined in a digital versatile disc random access memory (DVD-RAM) specification (DVD Specification for rewritable memory Part 1), in a digital versatile disc recordable memory (DVD-R) specification (DVD Specification for recordable memory Part 1), and in a digital versatile disc rewritable memory (DVD-RW) specification (DVD Specification for re-recordable memory Part 1). 
   However, discs having both a read-only specification and a recordable specification are not defined so that requirements for modification of data and addition of data, which are characteristics of a recordable disc, and requirements for mass copying of the same data, which is a characteristic of a read-only disc, cannot be simultaneously satisfied. 
   When proposing a new optical disc satisfying the above requirements, compatibility with a recording/reproducing apparatus according to a conventional specification should be considered. In other words, it is important to make a new optical disc satisfying the above requirements to be compatible with a conventional recording/reproducing apparatus which is made and performs, without consideration of a medium having the characteristics of both a recordable disc and a read-only disc. 
   In this case, it is apparent that complete compatibility cannot be achieved because the characteristic of a particular area on a single disc changes. Accordingly, as for compatibility, the characteristics of a read-only medium are primarily considered such that data in a read-only storage area can be reproduced in a conventional apparatus for only reproducing, and simultaneously, a writable storage area is considered to be compatible with physical recording/reproducing characteristics defined in a conventional rewritable specification taking into account the fact that data can be additionally recorded or updated in the writable storage area while a user is using a disc. 
   In addition, it is preferable that an optical recording medium having a read-only storage area and a writable storage area has drive compatibility with a conventional DVD-ROM drive and a conventional DVD-RAM drive. 
   For a clear understanding of the present invention, a structure of an optical disc (optical recording medium) defined according to a digital versatile disc read only memory (DVD-ROM) specification will be described in detail.  FIG. 1  is a sectional view of a conventional dual layer optical disc  10  defined according to the DVD-ROM specification. The optical disc defined according to the DVD-ROM specification comprises first and second substrates  12 ,  14 . Information layers  16 ,  18  are formed on the first and second substrates  12 ,  14 , respectively, and the first and second substrates  12 ,  14  are united such that the information layers  16 ,  18  face each other. The information layer ( 16  in this instance) nearer to a substrate on which a read laser beam is incident is defined as a first recording layer, and the underlying information layer ( 18  in this instance) is defined as a second recording layer. 
   Such an optical disc  10  includes a lead-in area (not show) at an innermost part of the optical disc  10  and a lead-out area (not shown) at an outermost part of the optical disc  10 , or a middle area in which various control information (not shown) and information on the physical characteristics of the optical disc  10  is recorded, so that data in the inner part and the outer part can be steadily read. 
   Generally, a read-only optical disc is molded by injecting a polycarbonate resin material into a die, referred to as a stamper, on which information is formed in the form of embossed pits, such that the information can be transferred to the read-only disc. After forming the read-only optical disc by injection, a material such as aluminum having a characteristic of reflecting light is sputtered on an information surface to form a reflective layer. 
   A DVD-ROM (the optical disc  10 ) is formed by uniting two discs (the first and second substrates  12 ,  14 ), each of which is molded according to the above method to have a thickness of 0.6 mm, so as to have a total DVD-ROM thickness of 1.2 mm. One substrate may not have a recording layer, or each substrate may have two recording layers. In the case where each of first and second substrates  12 ,  14  has a single recording layer, when the optical disc is formed such that data can be read from only one side of the optical disc, the optical disc is referred to as a dual layer optical disc. When a disc is formed such that data can be read from layers on both sides of the optical disc  10 , the optical disc  10  is referred to as a double sided disc. 
   As described above, since information is recorded on a read-only optical disc while it is being formed by injecting a polycarbonate resin material into a stamper on which information is formed, the information can be formed on the read-only optical disc in a short time as compared to a magnetic recording medium or a writable recording medium. Accordingly, the read-only optical disc is suitable for mass producing the same data, such as a film or a computer game which needs to be copied in large quantity. 
     FIG. 2  is a diagram showing a structure of a conventional optical disc recording medium  20  having two data storage areas having different characteristics. Data which can be reproduced using a laser of 780 nm is recorded in a first recording area  26  on the optical disc  20 , and data which can be reproduced using a laser of 635–650 nm is recorded in a second recording area  27 . Referenced numeral  22  denotes a standard density information layer for a compact disc (CD), reference numeral  23  denotes a high-density information layer for a DVD, reference numeral  24  denotes a second substrate layer, reference numeral  25  denotes a first substrate layer, reference numeral  26  denotes the first recording area which is readable using the laser of 780 nm, and reference numeral  27  denotes the second recording area which is readable using the laser of 635–650 nm. The dual layer high-density optical disc  20  of  FIG. 2  is disclosed in U.S. Pat. No. 5,732,065, entitled “Optical Information Carrier Including Standard and High Density Layers,” and filed on Sep. 4, 1996. 
     FIG. 3  shows a structure of a complex recording layer  32  of a typical writable, optical recording medium  30 . Since user data is not recorded on a disc during manufacturing of a writable medium such as a digital versatile disc random access memory (DVD-RAM), substrates can be formed using the same stampers. Unlike a read-only medium in which a reflective layer is simply formed, a complex recording layer including a plurality of films (i.e., a dielectric layer  34 , a recording layer  36 , another dielectric layer  38  and a reflective layer  40  shown in  FIG. 3 ) needs to be formed on a substrate  42  to allow a user to record data on the optical recording medium  30 . A DVD-RAM or a digital versatile disc-rewritable (DVD-RW) has a complex recording layer having a multi-layered structure such that recording can be achieved using a change in a material of the recording layer  36 , that is, a change between an amorphous state and a crystalline state. 
   SUMMARY OF THE INVENTION 
   To solve the above and other problems, a first object of the present invention is to provide an optical recording medium that is compatible with a digital versatile disc (DVD) specification and also has a read-only storage area and a writable storage area. 
   A second object of the present invention is to provide an optical recording medium which has a read-only storage area and a writable storage area, and on which control information for the writable storage area is recorded in the read-only storage area so that the optical recording medium can be compatible with a DVD specification. 
   A third object of the present invention is to provide a recording/reproducing apparatus for an optical recording medium that is compatible with a DVD specification and also has a read-only storage area and a writable storage area. 
   In order to achieve at least the first and second objects, the present invention provides an optical recording medium comprising a substrate; a read-only storage area at an inner part of the substrate; and a writable storage area at an outer part of the substrate. 
   To achieve at least the third object of the present invention, there is provided an apparatus for recording/reproducing data onto/from an optical recording medium having a read-only storage area at an inner part of a substrate and a writable storage area at an outer part of the substrate, the apparatus comprising a system controller which generates identification information for indicating that the optical recording medium is a hybrid disc having the read-only storage area and the writable storage area; and a recording unit which records the data of the read-only storage area, which is updated for use by correction, modification and addition, in the writable storage area, and the generated identification information in the lead-in area of the read-only storage area. 
   Preferably, the recording/reproducing apparatus further comprises a reproducing unit which reproduces data from the optical recording medium by controlling a reference linear velocity for reproduction at the read-only storage area to be the same as a reference linear velocity at the innermost part of the writable storage area. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above and other objects and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings in which: 
       FIG. 1  is a sectional view of an optical recording medium compatible with a conventional digital versatile disc read only memory (DVD-ROM) specification; 
       FIG. 2  is a diagram showing a structure of a conventional optical recording having two kinds of data storage areas having different characteristics; 
       FIG. 3  is a diagram showing a structure of a conventional recording layer of a writable optical recording medium, which provides for a clear understanding of the present invention; 
       FIGS. 4 through 9  are examples of structures of embodiments of an optical recording medium having a read-only storage area and a writable storage area according to the present invention; 
       FIG. 10  is a diagram showing a control information format in a lead-in area on an optical recording medium according to the present invention; 
       FIG. 11  is a diagram showing a structure of hybrid disc identification information of the control information shown in  FIG. 10 ; 
       FIGS. 12A and 12B  are diagrams showing an information structure of a lead-in area on an optical recording medium having a writable specification and an information structure of a lead-in area on an optical recording medium having a read-only specification, respectively, for clear understanding of the present invention; and 
       FIG. 13  is a block diagram of a recording/reproducing apparatus using an optical recording medium according to embodiments of the present invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference will now made in detail to the present preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below in order to explain the present invention by referring to the figures. 
   When an optical recording medium (hereinafter, referred to as a hybrid disc) having both a read-only storage area and a writable storage area, which are defined in a DVD specification, is defined under the situation that conventionally, individual DVD specifications for a read-only medium and a writable medium exist, compatibility of the specification for the hybrid disc with the conventional specifications becomes a problem as described before. The term “writable” may indicate “recordable” for a DVD-R, “rewritable” for a DVD-RAM and “re-recordable” for a DVD-RW. 
   A recording medium having a ROM and a RAM area is mainly used for supplying the same content in bulk by taking advantage of easy duplication, which is the characteristic of a read-only medium. Accordingly, the read-only storage area needs to be primarily considered in solving a compatibility problem. 
   In addition, since a physical space on a disc is divided such that a specific space is assigned as a read-only storage area, and another specific space is assigned as a writable storage area, the physical characteristics of a space on a hybrid disc are different from those of a space on a disc having only one kind of storage area. Accordingly, it is apparent that the specification for the hybrid disc cannot be completely compatible with conventional specifications. 
   In this specification, as for the compatibility, it is preferable that the read-only storage area has a compatibility such that data in the read-only storage area can be reproduced in a conventional reproducing apparatus, and a writable storage area is compatible with the recording/reproducing characteristics of a conventional writable medium such that additional circuits necessary for implementing a recording/reproducing apparatus for recording, modifying or reproducing data on the writable storage area can be minimized. By doing this, user data stored in the read-only storage area can be reproduced in a conventional reproducing apparatus at least so that the hybrid disc can be used for the same usage as that of a conventional DVD-ROM. In addition, a recording/reproducing apparatus for the hybrid disc according to the present invention can modify data stored in the read-only storage area or add new data to the data stored in the read-only storage area, thereby securing compatibility of the hybrid disc with a conventional DVD reproducing apparatus. 
   A first embodiment which considers the requirements for such compatibility is shown in  FIG. 4 . In this diagram, a portion of a hybrid disc  40  is shown, wherein a data area  42 , in which user data can be prerecorded according to a conventional DVD-ROM specification, has a start diameter of 48 mm indicating the beginning of the data area and a maximum diameter of 116 mm (in the case of a disc having a diameter of 120 mm) or 76 mm (in the case of a disc having a diameter of 80 mm). In other words, the start diameter is predetermined, but the end diameter of the data area is not fixed to a certain value. A range is given for the end diameter. 
   Accordingly, the start diameter of the data area is set to 48 mm, and the end diameter of the data area is set to be larger than 48 mm and smaller than 116 mm in the case of an optical disc having a diameter of 120 nm (or 76 mm in the case of an optical disc having a diameter of 80 mm), and a writable storage area is defined in the remaining area other than an information area for recording control information among the area in which read-only data is not recorded, thereby obtaining optimal compatibility with a conventional DVD-ROM. 
   When considering the fact that a recording area is divided into a plurality of zones using a zoned continuous linear velocity (ZCLV) method in a DVD-RAM, it is preferable to assign at least an area corresponding to the size of a single zone defined in a DVD-RAM specification for the writable storage area. 
   In the case of the conventional DVD-RAM, various control information, such as the rotation speed of a disc and defect management information, are closely related to the size and the location of a zone. In particular, the rotation speed of the DVD-RAM is not only connected with a zone but also closely related to the recording characteristics of such a phase-change recording medium. Accordingly, to be compatible with the physical recording characteristics of the conventional DVD-RAM, it is preferable to consider size and location in the assignment of zones when the read-only storage area and the writable storage area are defined on the hybrid disc of the present invention. 
   In addition, the conventional DVD-ROM specification defines a dual layer disc. Accordingly, it is preferable to dispose the read-only storage area  44  defined by the dual layer DVD-ROM specification in an inner part of the hybrid disc  40  and the writable storage area of a single layer structure  50  in an outer part of the hybrid disc  40  beyond the read-only storage area  44  on the hybrid disc, as shown in  FIG. 4 . 
   Since the conventional specification for the writable storage area  50  defines only the single layer structure, it is preferable to dispose the writable storage area  50  on a first recording layer  46 , LAYER  0 , on a first substrate  52 . This is because a heat transfer characteristic changes, and this may result in a change in a recording characteristic in a writable medium including a recording layer having a multi-layer structure when the order of a substrate on which the recording layer is formed and a plurality of layers included in the recording layer, changes in view of an incident laser beam. 
   The structure of the hybrid disc  40  shown in  FIG. 4  defines a dual layer read-only storage area  44 , thereby realizing a capacity of 4.7 Gbytes, which is the size of the most widely used DVD-ROM, by applying the dual layer read-only storage area  44 , while including the writable storage area  50 . 
     FIG. 5  illustrates a second embodiment of the optical recording medium according to the present invention wherein a hybrid disc  60  is shown. A first substrate  62  has a transparent area  66  without having any storage area at its inner part and the writable storage area  50  at the outer circumference thereof. Meanwhile, the second substrate  54  has the recording layer  48 , LAYER  1 , in a read-only storage area  64  at its inner part, which is spatially separated from the writable storage area  50  of the first substrate  62 . 
   The two optical recording media, i.e., the second substrate  54  having the read-only storage area  64 , and the first substrate  62  having the writable storage area  50 , are combined with each other, thereby forming an optical recording medium  60  having both the read-only storage area  64  and the writable storage area  50 . As for the present embodiment of the optical recording medium, a writable medium manufacturing process and a read only medium manufacturing process can be applied separately, and different stampers (not shown) can be used in manufacturing the second substrate  64  having the read-only storage area  64  and the first substrate  62  having the writable storage area  50 . For this reason, even if the content of data to be written onto the read-only storage area  64  is changed, there is no need to change the stamper for the writable medium (the first substrate  62 ). On the other hand, an advantage in view of the read only medium, is that it is unnecessary to form a recording layer. 
   Also, the hybrid disc  60  as shown in the second embodiment in  FIG. 5  enables a read only disc manufacturer to produce a recording medium having a writable storage area and a read-only storage area by simply combining a medium having a writable storage area, which is commercially available, with a medium having a read-only storage area produced by the manufacturer. 
     FIG. 6  illustrates a third embodiment of the optical recording medium according to the present invention, wherein a hybrid disc  70  is shown. The hybrid disc  70  has a single read-only storage area  74  at its inner part and a writable storage area  50  at its outer part. Thus, the hybrid disc  70  having the read-only storage area  74  and the writable storage area  50 , which have different features, can be implemented with a single substrate, which is a first substrate  52 . 
   To avoid the read-only storage area  74  from being exposed during the formation of a recording layer  76  in a writable storage area  60 , the read-only storage area  74  is covered with a mask (not shown) during formation of the recording layer  76  in the writable storage area  50 ,  2  and the mask is removed before formation of an outermost reflective layer (not shown) of the hybrid disc  70 , so that the hybrid disc  70  can be constructed. A second substrate  84  has a dummy recording layer  58  in both the read-only storage area  74  and the writable storage area  50 , so that no data is recorded on the entire dummy recording layer  58  The hybrid disc having both a read-only storage area and a writable storage area  50  can be produced through such successive processes using a single stamper. 
     FIG. 7  illustrates a fourth embodiment of the optical recording medium according to the present invention, showing a hybrid disc  90 , in which a dual layered read-only storage area  92  is formed at the inner part of each of the first and second substrates  102  and  104  by a two photo polymerization (2P) technique, and a writable storage area  100  adopting a DVD-RAM format and having the recording/reproducing characteristics defined by a DVD-RAM format, is formed at the outer part of each of the first and second substrates  102  and  104 . For this case, writing or reading data onto or from the first and second recording layers  106  and  108 , LAYER  0  and LAYER  1 , formed at the first substrate  102  is performed through an incident side of entrance on the hybrid disc  90  of a laser beam of the first substrate  102 . Also, writing or reading data onto or from the first and second recording layers  106  and  108 , LAYER  0  and LAYER  1 , formed at the second substrate  104  is performed through an incident side of entrance on the hybrid disc  90  of a laser beam of the second substrate  104 . In the hybrid disc  90  having such a structure, formation of the recording layer at a portion of the storage area may be omitted. For example, the first substrate  102  may have a single layered read-only storage area or the second substrate may have no writable storage area. 
     FIG. 8  illustrates a fifth embodiment of the optical recording medium according to the present invention, wherein a hybrid disc  110  is shown. The structure of the hybrid disc  110  is the same as that shown in  FIG. 4 , except that the writable storage area  120  is formed with a dual layered structure (the writable storage area  120  of the first and second recording layers  46  and  48 ), and is arranged at the outer part of each of the first and second substrates  52  and  114 . As shown in  FIG. 8 , writing and reading operations are performed through the incident side of the first substrate  52 . For this case, recording/reproducing characteristics in the dual layered structure are different from those of the writable storage area having a single layered structure, so that the structure of a recording/reproducing apparatus for the optical recording medium may be complicated. Meanwhile, such a dual layered structure is advantageous due to an increased data writing capacity in the writable area. 
     FIG. 9  illustrates a sixth embodiment of the optical recording medium according to the present invention showing a hybrid disc  130 , in which a read-only storage area  134  is formed over a first substrate  142 , and a writable storage area  150  is formed over a second substrate  144 . The read-only storage area is formed of a first recording layer  146 , LAYER  0 , and the writable storage area is formed of a second recording layer  148 . This configuration may lower the compatibility in reading operations with other recording media. In addition, the recording characteristics are changed and thus the compatibility in writing operations with other recording media may be lowered. Advantages of the hybrid disc  130  shown in  FIG. 10  are that a writable medium and a read only medium can be separately manufactured, as described previously, and data writing capacity increases. 
   In the case where the writable storage area  150  is formed at the second substrate  144  and the read-only storage area  134  is formed at the first substrate  142 , the hybrid disc  130  can be constructed to enable reading or writing of data from or to two recording layers through the incident side of the first substrate  142 , rather than one side of the hybrid disc  130  for one layer and the other side of the hybrid disc  130  for the other layer. 
   On the other hand, when the writable storage area  150  is formed at the first substrate  142 , the second recording layer  148  must be formed of a semi-transmissive layer, and data from the read-only storage area  134  formed at the second substrate  144  must be reproduced with a higher read power so as to compensate for reduced read laser power due to the first recording layer  146  of the first substrate  142 . For this case, it is very likely that data of the first recording layer  146  will be erased or changed by interference. The configuration shown in  FIG. 9  contributes to minimizing such a problem with an increased writable storage area. 
     FIG. 10  illustrates the control information for correct playback from the optical recording medium according to the first through fifth embodiments of the present invention by a recording/reproducing apparatus. 
   As for a hybrid disc medium having a read-only storage area and a writable storage area, as previously mentioned, the read-only storage area is constructed to have compatibility with a conventional DVD-ROM reproducing apparatus. For this case, there is no problem in using a conventional DVD reproducing apparatus. However, a disc identifier for use in distinguishing a hybrid disc from a conventional DVD-ROM is required to enable an apparatus for recording/reproducing data onto/from the writable storage area to identify the hybrid disc. The need for such identification information may be satisfied by adding particular information to the lead-in area. 
   To implement the compatibility with a DVD reproducing apparatus which is able to recognize only a conventional DVD-ROM, it is preferable that data writing is performed with reserved bytes, without using the physical format information of the control data zone. This is because modifying the physical format information, for example, the BP 0 , of the existing control data zone including book type information indicating the type of specification book, and part version information of the specification book, to be suitable for a new medium, may result in losing compatibility. 
   In particular, DVD-ROMs do not utilize the 17 th  through 32 nd  bytes of the physical format information, and thus hybrid disc identification information indicating a hybrid disc having a read-only storage area and a writable storage area can be written using some reserved bytes for other writing formats. As shown in  FIG. 11 , such hybrid disc identification information includes information on the presence or absence of the writable storage area, which is an indicator of the hybrid disc, and on part version for the hybrid disc. 
   Comparing the lead-in information of a DVD-ROM with the lead-in information of a is DVD-RAM that is a writable medium, the lead-in information of the writable medium contains all fields of the lead-in information of the DVD-ROM. On the other hand, the lead-in information of the DVD-ROM uses only 16 bytes and the remaining bytes are reserved. 
   As for the writable medium, a plurality of information areas are allocated to the lead-in information for adding information on, for example, the recording characteristics of the medium. Also, the recording density belonging to the lead-in information of the DVD-RAM is constructed to be different from that of a DVD-ROM disc. 
   As shown in  FIG. 10 , when reproduction is carried out from the lead-in area of the read-only storage area, the data area of the read-only storage area, the lead-out area of the read-only storage area, and the lead-in area of the writable storage area consecutively, the data transmission rate and the rotation speed of a spindle motor are varied, thereby slowing down a data recording/reproducing speed. To solve this problem, it is preferable for the hybrid disc to store the physical format information of the control data zone for the writable storage area in the lead-in area of the read-only storage area. 
   For this case, the reserved bytes among 2048 bytes allocated for the physical format information of the read-only storage area, i.e., the bytes after the 1024 th  byte, are used to store the physical format information for the writable storage area, and thus the storage of corresponding information in the lead-in area of a writable medium can be omitted. As a result, a delay in writing and reading operations due to the difference in transmission rate and rotation speed of a spindle motor can be avoided. 
     FIG. 10  shows that the control data zone of the lead-in area of the read-only storage area includes physical format information, disc manufacturer information and reserved bytes. The physical format information comprises bytes BP 0  to BP 2047 . BP 0  includes the book type (DVD-ROM disc, DVD-RAM disc) and part version. In the present invention, the book type will be “DVD-ROM” so as to be readable by a conventional DVD-ROM player. BP 0  to BP 16  includes physical format information for a DVD-ROM, or in this instance, the read-only storage area. BP 17  to BP 18  includes the hybrid disc identification information as shown in  FIG. 11 . BP 19  to BP 1023  are reserved bytes. BP 1024  to BP 2047  are physical format information for a DVD-RAM, or in this instance, the writable storage area. 
   As shown in  FIG. 12A , a DVD-RAM, which has a writable format, has the same information structure of an embossed data zone having pits in the lead-in area as that of a DVD-ROM shown in  FIG. 12B . In other words, a reference code, a buffer zone, an initial zone and the like are the same in terms of size and data value between the two information structures. The only difference between the two information structures lies in that a portion of information of the control data zone is different. This minor difference means that the two lead-in areas can be integrated with the identical information. 
   If the information of the two lead-in areas is integrated into the lead-in information for the read-only storage region, it is sufficient for the lead-in area of the writable storage area to only include a connection zone for connecting the read-only storage area and the writable storage area, defect management zones DMA  1  and DMA  2 , and a drive test zone. 
   The rewritable lead-in area is located in the writable storage area, and the connection zone is a mirror zone formed of a reflective layer without including any information, which is effective in minimizing the unnecessary space between the read-only storage area and the writable storage area. 
     FIG. 13  is a block diagram of an apparatus for recording/reproducing information onto/from the optical recording medium according to the embodiments of the present invention. 
   For a writing operation, an AV CODEC and/or host interface  210  compresses an A/V signal from the outside according to a predetermined compression scheme, and outputs information on the size of the compressed A/V data. A digital signal processor (DSP)  220  receives the compressed A/V data from the AV CODEC and/or host interface  210 , adds additional information to the received compressed A/V data for error correction coding (ECC), and modulates the data according to a predetermined modulation scheme. A radio frequency amplifier (RF AMP)  230  converts the data modulated by the DSP  220  into an RF signal. A pickup unit  240  writes the RF signal from the RF AMP  230  onto the writable storage area of a disc (any of the hybrid discs  40 ,  60 ,  70 ,  90 ,  110  and  130  disclosed herein) mounted on a turn table. A servo unit  250  receives information required for servo control from a system controller  260 , and stably servo controls the disc. 
   The system controller  260  generates identification information for indicating a hybrid disc having a read-only storage area and a writable storage area, and controls the apparatus to write the identification information onto the lead-in area of the read-only storage area through the DSP  220  and the RF AMP  230 . 
   On the other hand, for a reading operation, the pickup unit  240  picks up the data, which is in the form of an optical signal, from a hybrid disc having a read-only storage area and a writable storage area, and outputs an electrical signal. The RF AMP  230  extracts a servo signal for use in servo controlling and the modulated data. The DSP  220  demodulates the modulated data from the RF AMP  230  based on the modulation scheme used for the previous modulation, corrects errors through ECC, and removes the data added for the ECC. The servo unit  250  receives information required for servo controlling from the RF AMP  130  and the system controller  260 , and performs servo controlling. The AV CODEC and/or host interface  210  decompresses the compressed A/V data from the DSP  220  to output the original A/V signal. The system controller  260  controls the entire system for reading and writing information data from and to the hybrid disc seated on the turn table by user interfacing. 
   A problem of hybrid discs having a read-only storage area in a DVD-ROM format and a writable storage area in a DVD-RAM format is that a reference linear velocity is different for each area. Especially, a change in reference linear velocity for the writable storage area varies the recording characteristics, and thus data cannot be recorded on the area. On the other hand, as can be seen from an existing multiple speed reproducing system for DVD-ROMs, data can be reproduced from the read-only storage area at variable reproduction speeds, without causing any serious problem. 
   In the apparatus for alternately and repeatedly reproducing or recording data from or onto the read-only storage area and the writable storage area, respectively, it is preferable that the servo unit  250  reproduces the data from the read-only storage area at the same reference velocity as the reference linear velocity for recording and reproducing the data at the innermost part of the writable storage area. 
   As previously described, the present invention provides an optical recording medium having composite recording/reproducing characteristics, in which both a read-only storage area in the existing DVD-ROM format, and a writable storage area having the recording/reproducing characteristics defined by a DVD-RAM format are present on an optical recording medium such as a hybrid disc. In the hybrid disc according to the embodiments of the present invention, data correction, modification and addition of data stored in the read-only storage area is possible, using the writable storage area. In addition, the hybrid disc can be efficiently manufactured by various methods according to the present invention. 
   Although a few preferred embodiments of the present invention have been shown and described, it would be appreciated by those skilled in the art that changes may be made in this embodiment without departing from the principles and spirit of the invention, the scope of which is defined in the claims and their equivalents.