Method of managing overwrite and method of recording management information on an optical disc write once

Description

This application claims the benefit of the Korean Application No. P2002-78889 filed on Dec., 11, 2002 and P2003-5212 filed on Jan., 27, 2003 and P2003-9893 filed on Feb., 17, 2003 and P2003-13199 filed on Mar., 3, 2003 which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of managing overwrite and a method of recording management information on an optical disc write once.

2. Discussion of the Related Art

Recently, it is expected that a new HD-DVD (High-Density Digital Versatile Disc) on which video data and audio data can be written and stored in high qualities and in large quantities, for example, a BD-RE (Blu-ray Rewritable Disc), will be developed and produced.

The BD-RE, as shown in FIG. 1, is divided into an LIA (Lead-In Area), a data area, and an LOA (Lead-Out Area). In the head and the tail of the data area, an ISA (Inner Spare Area) and an OSA (Outer Spare Area) are dividedly arranged.

The BD-RE records data in the unit of a cluster corresponding to a specified recording unit, and as shown in FIG. 1, it is detected if any defect area exists in the data area during recording the data. If the defect area is detected, a series of replacement-recording operations for performing a replacement recording of the data recorded in the defect area in the unit of a cluster in a spare area, for example, an ISA, is performed. Also, position information of the defect area and position information replacement-recorded in the spare area are recorded and stored in a defect list in the read-in area as management information.

Accordingly, even if the defect area exists in the data area of the BD-RE, the data recorded in the defect area is replacement-recorded in the spare area, and during the reproducing operation, the data replacement-recorded in the spare area, instead of the data of the defect area, is read out and reproduced with reference to the management information, so that any data recording/reproducing error can be prevented in advance.

Meanwhile, the standardization of a BD-WO (Blu-ray Disc Write Once) has recently been discussed among companies concerned, and since the BD-WO is recordable only once over the whole area of the disc, it is physically impossible to perform overwrite on the BD-WO unlike the BD-RE.

However, it may be necessary to perform the overwrite on a BD-WO in order to edit the recorded data, to modify a part of the recorded data, or to offer convenience to a user or a host, and thus an efficient scheme for this is urgently demanded.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method of managing overwrite and a method of recording management information on an optical disc write once that substantially obviate one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method of managing overwrite, a method of recording management information on an optical disc write once, and a recording/reproducing device which make it possible to overwrite logically on the optical disc write once.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method of managing overwrite on an optical disc write once includes replacement-recording data which is requested to be overwritten in a specified area of the disc where recording is completed in another data area physically separated from the specified area in the disc, and producing and recording management information for reproducing the physically replacement-recorded data.

In another aspect of the present invention, a method of recording management information on an optical disc write once includes replacement-recording data of an area of the disc, where an overwrite is requested or a defect is produced, in a specified area of the disc, and in recording management information on the overwrite, separately recording the management information in a case that one recording unit is replacement-recorded and the management information in a case that a plurality of recording units are replacement-recorded.

In still another aspect of the present invention, a method of recording management information on an optical disc write once includes replacement-recording data of an area of the disc, where an overwrite is requested or a defect is produced, in a specified area of the disc, and in recording management information on the overwrite, separately recording the management information in a case that the data is replacement-recorded by an overwrite request and the management information in a case that the data is replacement-recorded due to a defect area.

In still another aspect of the present invention, an apparatus for recording/reproducing an optical disc write once includes a controller for transferring a recording command for requesting recording on a specified area of the disc, and a recording/reproducing device for judging whether the specified area is an area where recording is completed or an area where no recording is performed, and replacement-recording data in another area of a data area and recording a fact that the replacement recording has been performed as management information on the disc if it is judged that the specified area is the area where the recording is completed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

FIG. 1 schematically illustrates the construction of a rewritable optical disc and a defect management method according to the related art;

FIG. 2 illustrates a method of managing overwrite on an optical disc write once according to an embodiment of the present invention;

FIG. 3 illustrates a method of managing overwrite on an optical disc write once according to another embodiment of the present invention;

FIGS. 4A, 4B and 5 illustrate methods of managing overwrite on an optical disc write once according to still other embodiments of the present invention;

FIG. 6 schematically illustrates a method of recording management information on a rewritable optical disc according to the related art;

FIG. 7 illustrates a method of recording management information on an optical disc write once according to an embodiment of the present invention;

FIGS. 8A and 8B illustrate tables showing contents of management information on an optical disc write once of FIG. 7 according to the present invention;

FIG. 9 illustrates a method of recording management information on an optical disc write once according to another embodiment of the present invention;

FIG. 10 illustrates a method of recording management information on an optical disc write once according to still another embodiment of the present invention;

FIGS. 11A and 11B illustrate tables showing contents of management information on an optical disc write once of FIGS. 9 and 10 according to the present invention;

FIG. 12 illustrates a method of updating management information on an optical disc write once of FIGS. 9 and 10 according to the present invention; and

FIG. 13 illustrates a device for recording/reproducing an optical disc write once according to the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the method of managing overwrite on an optical disc write once according to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

The present invention makes it possible to perform overwrite even on an optical disc write once. The term “overwrite” means a repeated recording on a specified area in a rewritable optical disc. In other words, overwrite is just the inherent characteristic of the rewritable optical disc, and it is generally known that it is impossible to perform overwrite on the optical disc write once.

However, the present invention makes it possible to logically perform overwrite as the physical characteristic of the optical disc write once is maintained.

FIG. 2 illustrates a method of managing overwrite on an optical disc write once according to an embodiment of the present invention. For example, the BD-WO (Blu-ray Disc Write Once) includes an LIA (Lead-In Area), a data area, and an LOA (Lead-Out Area). In the head and the tail of the data area, an ISA (Inner Spare Area) and an OSA (Outer Spare Area) may be dividedly arranged.

Also, in the disc, a TDMA (Temporary Defect Management Area) is provided. A TDFL (Temporary Defect List) is recorded in the TDMA, and a defect entry or an overwrite entry is recorded in the TDFL as management information. Accordingly, in the case that the data of the corresponding area is replacement-recorded in another area in the data area due to the defect area or by an overwrite request, the management information is recorded as the TDFL in the TDMA.

In FIG. 2, if an already recorded area already exists in the data area, the ‘overwrite’ in the corresponding area is not physically permitted due to the characteristic of the optical disc write once. However, if a recording command of a user or a host requests performing of the recording on an A-B area (e.g., already recorded area) as shown in FIG. 2, the present invention makes a driver itself perform the replacement recording of data in another area in the data area. Accordingly, the user or the host can command the recording irrespective of whether the specified area of the disc is recorded or not, and thus the user can use the optical disc write once just like the rewritable optical disc. This is called a logical overwrite (LOW) in distinction from the physical overwrite.

Specifically, in carrying out the recording command on the A-B area as shown in FIG. 2, overwrite cannot be performed on the corresponding area since it is already recorded area. Instead, the recording command can be carried out in a manner that the data is replacement-recorded in a C-D area in front of an OSA (Outer Spare Area) in the data area, and the corresponding management area is recorded in the TDMA of the disc as the TDFL information. Thereafter, if a user or a host commands the reproducing of the data in the A-B area of the disc, the driver reproduces the data stored in the C-D area instead of the data in the A-B area with reference to the recorded management information.

FIGS. 3, 4A, 4B and 5 show the different areas where the replacement recording is performed by the overwrite request, and FIGS. 6 to 12 show methods of recording management information on overwrite or consecutive defect areas according to the embodiments of the present invention. It is noted that the same reference numbers will be used throughout the drawings to refer to the same or like parts.

FIG. 3 illustrates a method of managing overwrite on an optical disc write once according to another embodiment of the present invention. This embodiment is characterized in that the data of the area where overwrite is requested is replacement-recorded to follow the already recorded area. This embodiment is the same as the embodiment of FIG. 2 except for the replacement-recorded area.

FIG. 4A shows a method of managing overwrite on an optical disc write once according to still another embodiment of the present invention. This embodiment is characterized in that the data of the area (e.g., A-B area) where overwrite is requested is replacement-recorded in the C-D area in the spare area. Thus, in the spare area, both a replacement cluster due to the defect area and a replacement cluster due to the overwrite request are recorded. As will be explained later, this means that the replacement recording due to the overwrite request can be treated in the same manner as the replacement recording due to the defect area. Also, as shown in FIG. 4B, the OSA can be divided into an area for defect and an area for overwrite.

FIG. 5 shows a method of managing overwrite on an optical disc write once according to still another embodiment of the present invention. In FIG. 5, the data to be recorded in the area (e.g., A-B area) where overwrite is requested is replacement-recorded in the C-D area in a separate overwrite area (OWA). That is, the spare area ISA or OSA is the replacement-recorded area when the defect area is produced, and the OWA is the replacement-recorded area when overwrite is requested. Accordingly, the replacement recording due to the defect area and the replacement recording by the overwrite request are clearly discriminated from each other.

FIGS. 6 to 12 show methods of recording management information according to the related art and according to the present invention. Referring to FIG. 6, a method of recording management information on the BD-RE disc according to the related art is illustrated in comparison to the method of recording management information on the BD-WO according to the present invention.

The defect information is recorded in the LIA of the disc, and is composed of a defect list header and a defect entry. The defect list header includes an identifier (ID) information for information the defect list and information which indicates the number of defect entries. One defect entry is composed of 8 bytes, and includes four fields of ‘status1’, ‘defective cluster first PSN (Physical sector number)’, ‘status2’ and ‘replacement cluster first PSN’. In the BD-RE, the ‘status1’ information indicates information on the type of defect entry. For example, if it is ‘0000b’, it is a RAD (Re-Allocation Defective) type defect entry where the replacement recording is normally completed, and if it is ‘0001b’, it is an NRD (Non-Reallocation Defective) type defect entry where a replacement area for the replacement recording is not designated. Also, the ‘defective cluster first PSN’ field is for recording positional information of the cluster where the defect is produced, and it is general that this field is indicated as the first PSN of the corresponding cluster. Also, the ‘status2’ field is a field which is not used in the BD-RE. To be explained later, according to the present invention, the management information is recorded actively using the ‘status2’ field. The ‘replacement cluster first PSN’ field is for recording positional information of the replacement-recorded area in the spare area due to the defect area. In the case of the RAD type defect entry, the information on the corresponding replacement-recorded position is normally recorded, but in the case of the NRD type defect entry, the replacement recording is not performed and thus this field is set to a ‘zero’ value.

FIGS. 7 to 12 illustrate methods of recording management information on an optical disc write once according to embodiments of the present invention. In the present invention, the recording of the management information is briefly divided into two types. First is to record the management information as the overwrite entry which is discriminated from the defect entry as shown in FIGS. 8A, 8B and 9, and second is to record the management information as the same type as the defect entry as shown in FIGS. 10 to 12. In the former, the two kinds of entries are discriminated from each other even through a sorting, but in the latter, the two kinds of entries are mixed through the sorting.

Hereinafter, the method of recording management information according to the present invention will be explained in detail.

FIG. 7 illustrates a method of recording management information on an optical disc write once when the replacement recording is performed by the overwrite request according to an embodiment of the present invention. FIGS. 8A and 8B illustrate the recording of positional information of the area where overwrite is requested, positional information of the replacement-recorded area, and size information of the overwrite as the management information.

In the present invention, for example, for the compatibility with the BD-RE, the management information is recorded as the entry having a size of 8 bytes in the area where the defect entry is recorded. Accordingly, the management information is recorded by applying four fields, which are the same as those of the defect entry. However, the management information due to overwrite is called the overwrite entry in distinction from the defect entry, and an ID information is used in the entry for discrimination.

The overwrite entry of FIG. 7 will be explained in detail. First, the type information, which is not used in the existing BD-RE, is used in the ‘status1’ field. For example, if it is confirmed that ‘1100b’ is used and the entry confirms the use of ‘1100b’, the system recognizes it as the ‘overwrite entry’. That is, the ‘status1’ field value, which is not used in the BD-RE, is used to discriminate the overwrite entry from the defect entry. In the ‘defective cluster first PSN’ field, start address information (e.g., A address) of the area, where overwrite is requested, is recorded. In the ‘replacement cluster first PSN’ field, start address information (e.g., C address) of the replacement-recorded area in the data area is recorded. It is possible to express such address information as the first PSN of the start cluster of the corresponding area. In the ‘status2’ field, the size information, with which overwrite is requested, is recorded. However, the ‘status2’ field is composed of 4 bits, and if the size of the area where the overwrite is requested exceeds 16 clusters, it cannot sufficiently express the size of the area. Thus, if clusters the number of which is less than 16 clusters is to be overwritten, the size information size_1 is recorded in the ‘status2’ field (case 1), but if the size exceeds 16 clusters, the size information size₁₃ 1 is recorded in the ‘defective cluster first PSN’ field and in the ‘replacement cluster first PSN’ field, respectively, or it is recorded in either of the fields, and ‘0000b’ is recorded in the ‘status2’ field (case 2).

Accordingly, if the ‘status1’ field is ‘1100b’, the system recognizes the overwrite entry, and if the ‘status2’ field is ‘0000b’, the system recognizes that the size exceeds 16 clusters and the size information is indicated by the consecutive entries. If the ‘status2’ field has a value different from ‘0000b’, the system recognizes that the clusters as large as the value obtained by converting the corresponding digital value into a decimal number corresponds to the size information with which the overwrite is requested. By recognizing the start address and the size information, the end address of the corresponding area can be naturally confirmed.

FIG. 7 illustrates only the case that the replacement-recorded area is in front of the OSA. However, as shown in FIGS. 3, 4A, 4B and 5, the replacement-recorded area may follow the recording area (FIG. 3), may be in the spare area (FIG. 4), or may be in a separate OWA (FIG. 5).

FIG. 8A schematically illustrates the structure of the TDFL. In the TDFL, the defect entries and the overwrite entries are separately recorded. This is the result of sorting the entries based on the ‘status1’ information. Also, the TDFL-header of the TDFL additionally has information on the number of defect entries and the overwrite entries, and thus the information of th entries recorded in the corresponding TDFL can be obtained.

FIG. 8B illustrate a table of entry types discussed in FIG. 7. In the table, the defect entry and the overwrite entry are discriminated by the ‘status1’ field. Also, the overwrite entry is divided into a case of having one entry and a case of having two entries in accordance with the ‘status2’ field value. If ‘status2=0000b’, it corresponds to two entries, and the size information can be obtained through the following entry. If ‘status2=others except for 0000b’, the corresponding value directly means the size information.

FIGS. 9 and 10 illustrate methods of recording management information on an optical disc write once according to other embodiments of the present invention. FIGS. 9 and 10 show the case that if the overwrite is requested, the management information on the replacement recording is processed as the same type as the existing defect entry. That is, the management information is recorded under the assumption that the replacement recording by the overwrite request is the same as the replacement recording due to the defect area. In this case, it is more preferable to discriminate whether the number of replacement-recorded recording units is singular or plural (in the case of the BD-WO, cluster) than to discriminate whether the replacement recording is due to the overwrite or the defect area.

That is, according to this embodiment, the plural clusters are replacement-recorded in another area by a certain cause, and the management information for managing this is expressed in distinction from the management information in the case that one recording unit is replacement-recorded. Accordingly, the reason why the plural clusters are replacement-recorded may be the overwriting according to the present invention, or the plural defect areas produced in the consecutive recording units. In the present invention, the replacement recording of the consecutive plural clusters is called a ‘block linear replacement’ or simply a ‘block replacement’. On the contrary, the replacement recording of one cluster is called a ‘1 cluster linear replacement’ or simply a ‘1 cluster replacement’.

According to the methods illustrated in FIGS. 9 and 10, if the overwrite of a specified area (e.g., A-B area) of the disc is requested by the user or consecutive defects are produced in all the corresponding areas, the corresponding data is replacement-recorded in the C-D area of the spare area, and its management information is recorded. Even if the replacement recording is performed in another data area except for the spare area in the case of the overwrite as shown in FIGS. 2, 3, 4A, 4B and 5, the management information recording method according to the invention can be applied as it is.

In FIGS. 9 and 10, the defect entry is divided into two kinds. First is the entry (1 cluster replacement) in the case that one recording unit is replacement-recorded, and second is the entry (block replacement) in the case that the plural recording units are replacement-recorded. That is, the management information recording method of FIGS. 9 and 10 records the management information by discriminating whether the replacement recording unit is ‘1 cluster’ or ‘block’, and it is assumed that the overwrite request or the defect area is produced in the unit of ‘1 cluster’ or ‘block’.

Also, referring to FIGS. 9 and 10, the defect entry is divided according to whether the size information is used as the management information. FIG. 9 illustrates the case that the size information is used, and FIG. 10 illustrates the case that the size information is not used.

First, in FIG. 9, in the case of the ‘1 cluster replacement’, the management information is recorded in the same manner as in FIG. 7. In the case of the ‘block replacement’, the ‘status1’ field has ‘0000b’ in the same manner as the case of the ‘1 cluster replacement’. The sorting is applied whenever the defect entry is recorded in the TDFL. The first basis of the sorting is the ‘status1’ field, and the next is the ‘defective cluster first PSN’ field. Accordingly, if the replacement recording is normally performed, the ‘1 cluster replacement’ and the ‘block replacement’ have the same ‘status1=0000b’, and thus in the same ‘status1’, the sorting is performed by the ‘defective cluster first PSN’ field. This is why the ‘status1’ field has ‘0000b’ both in the case of the ‘block replacement’ and in the case of the ‘1 cluster replacement’. This feature will be explained in detail with reference to FIG. 12.

Accordingly, the discrimination between the case of the ‘1 cluster replacement’ and the case of the ‘block replacement’ is performed using the ‘status2’ field. That is, in the case of the ‘1 cluster replacement’, ‘status2=0000b, but in the case of the ‘block replacement’, ‘status2=0001b or 1001b’. Here, in the case of the ‘block replacement’, it has two consecutive entries. If ‘status2=0001b’, the entry will be the first leading entry, and if ‘status=1001b’, the entry will be the second following entry. The first entry, which is ‘status2=0002b’, has the original start address of the original area to be replaced and a replacement start address of the replacement-recorded area. The second entry, which is ‘status2=0001b or 1001b’, has the size information size_1 of the area to be replaced.

FIG. 9 shows the recording of ‘status2=0001b or 1001b’ in the case of the block replacement according to an embodiment of the present invention, and it is natural that any other information which is discriminated from ‘status=0000b’ can be used. For example, in the case of the block replacement, the same result can be obtained even if it is set that ‘status2=0011b or 1011b’.

FIG. 10 illustrates the case that the second entry of FIG. 9 has the original end address of the original area and the replacement end address of the replacement-recorded area instead of the size information used in the second entry of FIG. 9. Other parts are the same as those in FIG. 9.

FIG. 11A schematically illustrates the entry being recorded in the TDFL as the management information in recording the management information on the optical disc write once according to the present invention. All the entries are managed as the same defect entries (in fact, both the replacement recording due to the overwrite and the replacement recording due to the defect area have the same ‘status1=0000b’, and this is called the defect entry). In the TDFL header, information, which indicates the number of defect entries for each kind, is placed. Here, the entry in the case of the ‘block replacement’ may be called a BRAD (Block RAD) or a CDA (Consecutive Defective Area). This is to indicate that in the case of the ‘block replacement’, the block RAD is the same as that in the case of the ‘1 cluster replacement’, which is normally replacement-recorded, but the replacement recording is performed in the unit of a block, not in the unit of a cluster.

FIG. 11B illustrates a table showing the entry-type relation as described with reference to FIGS. 9 and 10. As shown in the table, in the case of the ‘1 cluster replacement’, the entry has ‘status2=0000b’, and in the case of the ‘block replacement’, the entry has ‘status 2=0000b or 1001b’. Also, in the case that the replacement recording is normally completed, the entry has ‘status1=0001b’ (NRD or BNRD). By extension in this manner, the table will be able to be applied to any type entry.

FIG. 12 illustrates a method of updating the TDFL in the management information recording method as shown in FIGS. 9, 10, 11A and 11B, and especially shows the management information recording method in the case that the sorting is applied.

First, under the assumption that the TDFL was recorded as TDFL#K by 5 ‘1-cluster-replacements’, 6 consecutive clusters including defective areas which correspond to the defect entries 3, 4 and 5 have been replacement-recorded as the ‘block replacement’. At this time, a new entry will be recorded at the update time of the TDFK#K+1, and since the defect entries 3, 4 and 5 recorded in the previous TDFL#K includes in the ‘block replacement’ area in the TDFL#K+1, they require no further management and thus are omitted in the TDFL#K+1. That is, since the defect entries 3, 4 and 5 can be expressed as a new BRAD type entry, they are not recorded as the management information in the TDFL#K+1. Accordingly, the number of final entries of the TDFL#K+1 will be three, and the three entries are first aligned based on the ‘status1’ information by sorting, and then aligned in the order of positions of their original areas before the replacement. By applying this to the case of FIG. 12, all the entry types RAD or BRAD have the same ‘status1=0000b’ in TDFL#K+1, and thus the entries are aligned in the order of PSNs (Physical Sector Numbers) of the replaced original areas, which is the second basis of sorting. By doing so, the number of defect entries produced due to the ‘block replacement’ can be reduced, and this makes it possible to efficiently use the management area of the optical disc write once.

FIG. 13 illustrates an apparatus for recording/reproducing an optical disc write once according to the present invention.

The recording/reproducing apparatus includes a recording/reproducing device for performing the recording/reproducing on the optical disc, and a host or controller for controlling the device. The controller for providing a recording/reproducing command to the recording/reproducing device, and the recording/reproducing device performs the recording/reproducing on a specified area of the disc according to the command of the controller. The recording/reproducing device 10 comprises an interface 12 for performing a communication with the outside, an optical pickup 11 for recording or reproducing data on the disc, a data processor 13 for receiving the reproduced signal from the optical pickup to restore to a desired signal value, or modulating the signal to be recorded to a signal which can be recorded on the disc to transfer the modulated signal, a servo unit 14 for controlling the optical pickup 11 in order to accurately read the signal from the optical disc or to accurately write the signal on the disc, a memory 15 for temporarily storing various information including the management information and data, and a microcomputer 16 for controlling constituent elements of the recording/reproducing device.

During the recording operation, all the management information of the disc is read out and stored in the memory 15 of the recording/reproducing device, and the management information is used for the recording/reproducing operation on the optical disc. The controller 20, if it is required to record data in a specified area of the disc, transfers the positional information to the recording/reproducing device along with the data to be recorded. The microcomputer 16 in the recording/reproducing device 10 receives the recording command, and judges whether the area of the optical disc in which the controller 20 desires to record data is an already recorded area or a non-recorded area from the management information stored in the memory 15. If it is judged that the area is the non-recorded area, the microcomputer 16 performs the recording in accordance with the recording command of the controller 20, and if it is judged that the area is the already recorded area, the microcomputer 16 replacement-records the data in another area of the data area. Accordingly, the microcomputer 16 transfers the positional information of the replacement-recorded area and the data to the server unit 14 and the data processor 13, so that the replacement recording can be performed at the desired position in the disc through the optical pickup 11.

During the reproducing operation, all the management information of the disc is read out and stored in the memory 15 of the recording/reproducing device, and the management information is used for the recording/reproducing operation on the optical disc. The controller 20, if it is required to reproduce data recorded in a specified area of the disc, transfers the positional information to the recording/reproducing device. The microcomputer 16 in the recording/reproducing device 10 receives the reproducing command, and judges whether the data has been replacement-recorded in another area of the data area. This can be confirmed using the defect entry or the overwrite entry recorded in the TDFL as described above. Accordingly, if the area desired to be reproduced is not the replaced area, the controller reproduces the corresponding area, and transmits the reproduced information to the controller 20. If the data has been replacement-recorded in another area, the microcomputer reproduces the corresponding replacement-recorded area, and transmits the reproduced information to the controller 20.

It will be apparent to those skilled in the art than various modifications and variations can be made in the present invention. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.