Information recording and reproducing apparatus

An information recording and reproducing apparatus includes a rewritable optical disc having a plurality of sectors on which data can be rewritten. The rewritable optical disc is divided into an additionally recordable region in which the data are additionally recorded and a rewritable disc control region in which an address of a latest recorded sector in the additionally recordable region is recorded. The optical disc is used as an additionally recordable optical disc in which recording is permitted only one time and reproduction can be performed plural times. The information recording and reproducing apparatus further includes a control circuit for recording data on unrecorded sectors in the additionally recordable region and for reading the data from recorded sectors. This control circuit can rewrite and reproduce data in the disc control region. The control circuit reads the disc control region prior to additional recording of data, thereby finding a first unrecorded sector from the address of the latest recorded sector recorded in the disc control region. Furthermore, the control circuit records data on unrecorded sectors following the first unrecorded sector, and upon termination of data recording, the address of the latest recorded sector in the disc control region is rewritten.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates generally to an information recording and 
reproducing apparatus for successively recording and reproducing 
information, and more particularly, an information recording and 
reproducing apparatus capable of emulating a rewritable optical disc as an 
optical disc of the type in which recording is permitted only one time and 
reading is permitted many times, but no rewriting is permitted. 
2. Description of the Prior Art 
It is generally known that an optical disc can have information recorded 
thereon in a high recording density which may be about 10 or more times 
that recordable on a magnetic disc. The high recording density primarily 
owes to the high converging characteristic of a laser beam and tracks 
narrowed in pitch. 
An optical disc called "WORM" (write-once read-many type) has a useful life 
longer than 10 years and is characterized in that recording is permitted 
only one time and reading is permitted many times, but no rewriting is 
permitted in principle. 
The recent technical progress of optical disc media makes it possible to 
put to practical use media in which rewriting of data is permitted as 
similar to magnetic media. Magneto-optical disc media, phase change type 
rewritable media, and the like are in practical use as such optical disc 
media. Nowadays, environmental characteristics required to store the 
optical disc media are remarkably improved, as compared with those for 
magnetic tapes. Furthermore, by the use of an ordinary rewritable optical 
disc and a drive therefor, emulation of a "WORM" operation is performed in 
which recording is permitted only one time and reading is permitted many 
times. 
In order to impart a "WORM" function to the optical disc and the drive 
therefor, "WORM" (information) indicating that the optical disc is a 
"WORM" disc is pre-recorded as bits on control tracks whereas the disc 
drive is made to perform a "WORM" recording operation based upon the 
"WORM" information recorded on the control tracks such that data recording 
is permitted on unrecorded sectors but prohibited on recorded sectors. 
Since the rewritable optical disc and a "WORM" emulated optical disc 
originate from the same recording medium, it is only necessary to add to 
the disc drive a function required for handling the "WORM" information and 
that required for emulating the "WORM" operation. Accordingly, the disc 
drive can be considerably simplified, as compared with the case where the 
same disc drive is used for recording on and reproducing from the ordinary 
rewritable optical discs and the "WORM" optical discs which are different 
from each other in optical characteristics and recording principles. 
In an information recording and reproducing apparatus employing the 
conventional "WORM" optical discs, data recording is performed on 
unrecorded sectors by modulating a laser beam emitted from an optical head 
at a strong recording power while the laser beam is being focused on a 
desired track. In data reproducing, a considerably weak laser beam is 
initially applied to the optical disc, and upon receipt of a light 
reflected therefrom, a reproducing signal is generated and then 
demodulated 
In the "WORM" optical disc, since the data recording is permitted a single 
time, it is necessary to record data on the unrecorded sectors 
successively from the beginning of a track. In the data reproducing, it is 
important to find out the end of recorded sectors from the viewpoint of 
high speed handling of file management information such as the so-called 
directory with the reasoning that the newest data exist on sectors to 
which latest recording has been performed. 
FIG. 1 depicts an arrangement of data in a conventional "WORM" optical disc 
33. The optical disc 33 stores data 34 of recorded files and a directory 
35 for controlling address information of sectors on which the data 34 
have been recorded, and includes an unrecorded region 36. The data 34 and 
the directory 35 are successively additionally recorded on the unrecorded 
region 36 from the outermost and innermost portions towards a medial 
portion of the optical disc 33 in the direction shown by arrows X and Y, 
respectively. 
How to record data will be discussed hereinafter taking the case where data 
(b) are additionally recorded on the optical disc 33. 
(1) A disc drive checks the presence or absence of envelopes of recording 
signals from the beginning of the directory 35 in order to detect a first 
sector S2 having no envelope. As a result, the latest directory DIRa is 
found out from a sector S1 immediately ahead of the sector S2. 
(2) From the directory DIRa, a last sector S3 can be known on which the end 
of the data 34 has been recorded. The data (b) are then recorded from a 
sector S4 to a sector S5. 
(3) The disc drive adds address information of the recorded data (b) (from 
the sector S4 to the sector S5) to the information of the directory DIRa 
and records a new directory DIRb from the sector S2. 
A "WORM" optical disc can be emulated in the above-described manner. 
However, since data must be recorded on the unrecorded sectors, it is 
always necessary to find out the position of the unrecorded sectors at the 
time of disc replacement. Furthermore, when the track density is made 
higher to raise the recording capacity, the use of the detection of the 
envelopes of the recording signals makes it difficult to correctly find 
out the latest recorded sector. This is primarily due to a crosstalk 
between tracks. A crosstalk signal occasionally leaks out of a recorded 
sector to an adjoining unrecorded sector and an envelope thereof is 
subsequently undesirably detected. 
SUMMARY OF THE INVENTION 
The present invention has been developed to overcome the above-described 
disadvantages. 
It is accordingly an object of the present invention to provide an improved 
information recording and reproducing apparatus capable of correctly 
finding out the position of the end of recorded sectors or the first 
unrecorded sector at a high speed. 
In accomplishing this and other objects, an information recording and 
reproducing apparatus according to the present invention includes a 
rewritable optical disc having a plurality of sectors on which data can be 
rewritten. The rewritable optical disc is divided into an additionally 
recordable region in which the data are additionally recorded and a 
rewritable disc control region in which an address of a latest recorded 
sector in the additionally recordable region is recorded. The optical disc 
is used as an additionally recordable optical disc in which recording is 
permitted only one time and reproduction can be performed plural times, 
like a "WORM" disc. 
The information recording and reproducing apparatus further includes an 
additionally recording and reproducing means for recording data on 
unrecorded sectors in the additionally recordable region and for reading 
the data from recorded sectors and a rewriting and reproducing means for 
rewriting and reproducing data in the disc control region. 
The rewriting and reproducing means reads the disc control region prior to 
additional recording of data, thereby finding a first unrecorded sector 
from the address of the latest recorded sector recorded in the disc 
control region. The additionally recording and reproducing means records 
data on unrecorded sectors following the first unrecorded sector, and upon 
termination of data recording, the rewriting and reproducing means 
rewrites the address of the latest recorded sector in the disc control 
region. 
In this way, a "WORM" recording operation is emulated by the use of a 
rewritable optical disc. As a result, a latest recorded sector or a first 
unrecorded sector can be detected at a high speed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring now to the drawings, there is shown in FIG. 2 a block diagram of 
an information recording and reproducing apparatus embodying the present 
invention. 
As shown in FIG. 2, the information recording and reproducing apparatus 
according to the present invention comprises an optical disc 1 for 
recording information thereon, a spindle motor 2 for rotating the optical 
disc 1, and an optical head 3 for focusing and tracking a laser beam on a 
track of the optical disc 1 to record signals. In reproducing, a laser 
beam is again applied to the optical disc 1 and the information recorded 
thereon is read by a reflected light therefrom. A laser provided in the 
optical head 3 is modulated by a laser driving circuit 4. Servo-error 
signals and reproducing signals from the optical head 3 are detected by a 
head amplifier circuit 5. A track search mechanism 7 makes the optical 
head 3 access to a desired track of the optical disc 1 and comprises, for 
example, a linear motor, and a light beam from the optical head 3 is 
focused for tracking on the track by a servo-circuit 6. A data modulator 8 
effects a digital-modulation with respect to inputted data whereas a data 
demodulator 9 effects a demodulation with respect to reproducing signals 
from the head amplifier circuit 5. An error correction circuit 10 is 
provided for encoding error correction codes and for performing an error 
correction. A RAM 11a and a RAM 11b store data recorded and data read out, 
respectively. A system interface circuit 12 electrically connects a host 
system and an optical disc drive with each other and comprises, for 
example, an SCSI (Small Computer System Interface). The entire disc drive 
system is controlled by a CPU 13. 
Reference numerals 14 and 15 denote a register for setting a target address 
required to record and reproduce data and an address comparator for 
performing a coincidence comparison between an address signal 101 and the 
target address set by the register 14, respectively. A reproducing signal 
100 from the optical disc 1 is reproduced as the address signal 101 by the 
data demodulator 9. Reference numerals 16 and 17 denote a register for 
storing a read command from the CPU 13 and a gate signal generating 
circuit for generating a write gate signal 102 and a read gate signal 103, 
respectively. The write gate signal 102 initiates a data recording at the 
timing the address comparator 15 outputs a coincidence signal indicative 
of the coincidence between the address signal 101 and the target address 
whereas the read gate signal 103 initiates a data readout. An AND gate 18 
is provided for taking a logic AND between a disc signal 104 indicating 
whether a "WORM" region is designated and an unrecorded sector signal 105 
indicating an unrecorded sector of a track to which the optical head 3 
accesses. The AND gate 18 outputs an additional recording signal 106 when 
additional recording is permitted on this sector. An AND gate 19 is 
provided for taking a logic AND between a data modulation signal 108 and a 
rewriting signal 107 indicating that the track to which the optical head 3 
accesses is a disc control region. The AND gate 19 outputs a data renewal 
signal for permitting data renewal on the disc control region. An AND gate 
20 takes a logic AND between the additional recording signal 106 and the 
data modulation signal 108 to record data on an unrecorded sector. The 
signal outputted from the AND gate 19 and that outputted from the AND gate 
20 are both inputted into and ORed in an OR gate 21 to be applied to the 
laser driving circuit 4. A control track reproducing circuit 22 is 
provided for reading a control track of the optical disc 1. A data 
coincidence comparator 23 performs a read verification by comparing the 
recording data stored in the RAM 11a and the reproducing data read out 
from the recording sectors and stored in the RAM 11b with each other to 
confirm the coincidence therebetween. 
FIG. 3 depicts an arrangement of tracks in the optical disc 1. 
The optical disc 1 includes a reproduction control track 24 and a disc 
control track 25 as a rewritable region. The reproduction control track 24 
is a region to be exclusively used for reproduction, on which disc 
information indicating whether the disc has been designated as a "WORM" 
disc and physical format information are recorded in the form of pits as 
its format in a factory. Address information of the end of recorded 
sectors in an additionally recordable region is recorded on the disc 
control track 25. The optical disc 1 further includes a directory 26 in 
which file control information is recorded, a defective sector substitute 
region 27 for substituting for defective sectors, a data region 28 on 
which data have been recorded, and an unrecorded region 29 having no data. 
The directory 26, the defective sector substitute region 27, the data 
region 28, and the unrecorded region 29 constitute an additionally 
recordable region 30. 
Let it be assumed that data (a) have already been recorded on the data 
region 28 and data (b) are recorded now. File control of the optical disc 
1 is performed by the use of a directory DIRa under the conditions in 
which the data (a) have been recorded and a directory DIRb after the data 
(b) have been recorded. The optical disc 1 shown in FIG. 3 includes 
defective sectors B1 and B2, for which are substituted sectors RA1 and 
RA2, respectively. 
FIG. 4 depicts an example of the reproduction control track 24 on which are 
recorded disc information 31 indicating whether the optical disc 1 made of 
a rewritable medium is a "WORM" disc or a rewritable disc and physical 
parameters including the speed of the optical disc 1, the type of 
modulation, and the like. 
If a "WORM" disc is designated as the disc information, the optical disc 1 
emulates a "WORM" medium, though it is a rewritable disc. 
FIG. 5 depicts one example of the disc control track 25, which is divided 
into n sectors from a sector S1 to a sector Sn in units of one sector. 
Disc control information 32 is recorded in each of these sectors S1-Sn. 
Upon recording the data (a), an address A1 of the latest recorded sector in 
the directory 26, an address A3 of the latest recorded sector in the data 
region 28, and an address RA1 of the latest recorded sector in the 
defective sector substitute region 27 are recorded as the disc control 
information 32. Each address consists of a track address and a sector 
address. 
The disc control information 32 is not always required to include all of 
the above addresses A1, A3 and RA1 but is required to include at least the 
address A1 of the latest recorded sector in the directory 26. If at least 
this address A1 is recorded, the address A3 of the latest recorded sector 
in the data region 28 and the address RA1 of the latest recorded sector in 
the defective sector substitute region 27 can be known from the directory. 
Since the disc control track 25 functions as a rewritable region, it is 
rewritten whenever new information is additionally recorded on the data 
region 28 and the directory 26. 
The provision of the rewritable disc control region enables the high speed 
detection of unrecorded sectors because the last address of recorded 
sectors is always recorded therein. According to this method, the latest 
recorded sector can directly be known as compared with the conventional 
method in which, whenever a "WORM" disc is replaced by another, an 
unrecorded sector immediately after recorded sectors is searched for by 
successively reproducing sectors from the beginning of the disc. 
Accordingly, the method according to the present invention can provide a 
high speed processing. In particular, the more data are recorded on the 
optical disc, the greater effect can be obtained. This method of detecting 
unrecorded sectors is a method most suitable for a large capacity optical 
disc. 
The operation of the information recording and reproducing apparatus having 
the above-described construction will be discussed hereinafter with 
reference to a flowchart shown in FIG. 6. 
Let it be assumed that the data (a) have been recorded on the optical disc 
1 and the directory DIRa corresponding thereto has been produced, as shown 
in FIG. 3, and that the data (b) are additionally recorded on the optical 
disc 1. 
Check of Replacement of Optical Discs (Step S1) 
(1) When an optical disc 1 is replaced by another, the CPU 13 rotates the 
motor 2 and outputs a command to the servo-circuit 6 so that a laser beam 
from the optical head 3 may be focused for tracking on a track of the 
optical disc 1. 
(2) In contrast, when no replacement is performed, the procedure proceeds 
to step S5. 
Readout of Reproduction Control Track (Step S2) 
(3) The CPU 13 commands the track search mechanism 7 to seek the 
reproduction control track 24. When the track search mechanism 7 has 
accessed to the reproduction control track 24, the disc information is 
read out from the control track reproducing circuit 22. 
Readout of Disc Control Track (Step S3) 
(4) The CPU 13 commands the track search mechanism 7 to search the disc 
control track 25. 
(5) When the track search mechanism 7 has accessed to the target track 25, 
the CPU 13 reads the disc control information recorded on the disc control 
track 25. 
More specifically, the CPU 13 sets the address of a read sector and a read 
command to the registers 14 and 16, respectively. Upon rotation of the 
optical disc 1, when the target sector is detected by the address 
coincidence circuit 15, the gate signal generating circuit 17 outputs a 
read gate signal 103, which is in turn inputted into the data demodulator 
9 to initiate a data demodulation. Upon correction of errors in the error 
correction circuit 10, data are stored in the RAM 11b. The CPU 13 reads 
address information of the latest recorded sectors from the RAM 11b and 
knows the addresses A1, A3 and RA1 of the latest recorded sectors in the 
directory DIRa, the data region 28, and the defective sector substitute 
region 27, respectively. 
(6) Based on these addresses A1, A3 and RA1, the CPU 13 calculates the 
addresses A2, A5 and RA2 of unrecorded sectors on which subsequent 
recording is performed. In the case where the address ascending is 
performed in the direction shown by an arrow Z, the addresses A2, A5 and 
RA2 are obtained as follows: 
EQU A2=A1-1, 
EQU A5=A3+1, and 
EQU RA2=RA1+1. 
Readout of Directory (Step S4) 
(7) The CPU 13 searches for the address A1 of the latest recorded sector in 
the directory region obtained at the above (6) and reads the directory 
DIRa in the same manner as (6) to transfer it to a host system or host 
CPU. 
(8) The CPU 13 knows the position of recorded data from the contents of the 
directory DIRa. In other words, the CPU 13 recognizes that the data (b) 
are the latest data and the address of the latest recorded sector is A3. 
Check of Designation of "WORM" Disc (Step S5) 
(9) Step S5 determines whether the optical disc 1 has been designated as a 
"WORM" disc. If the optical disc 1 has not been designated as a "WORM" 
disc, a data recording processing for an ordinary rewritable disc is 
performed with respect thereto. 
(10) In contrast, if the optical disc 1 has been designated as a "WORM" 
disc, a recording operation for the "WORM" disc is performed which will be 
discussed hereinafter. 
Recording of Data on Unrecorded Sectors (Step S6) 
(11) The CPU 13 requests the host system or host CPU to transfer data 
thereto. The data transferred are stored in the RAM 11a via the interface 
circuit 12. The CPU 13 outputs the unrecorded sector signal 105 and the 
additionally recording signal 104 to the AND gate circuit 18 to permit 
recording only on unrecorded sectors of the optical disc 1. 
(12) The CPU 13 sets to the register 14 the unrecorded sector A5 
immediately after the address A3 of the latest recorded sector. The CPU 12 
also sets a write command to the register 16. Upon rotation of the optical 
disc 1, when the target sector is detected by the address coincidence 
circuit 15, a write gate signal 102 is inputted into the data modulator 8 
from the gate generating circuit 17. The error correction circuit 10 adds 
error correction codes to the data, which are in turn modulated by the 
data modulator 8. The modulation signal 108 produced in this way is then 
inputted into the laser driving circuit 4 via the AND gate 20 and the OR 
gate 21 to modulate the intensity of a laser of the optical head 3 so that 
the data may be recorded on the optical disc 1. 
Furthermore, the CPU 13 alters a value of address and sets it to the 
register 14 again. The CPU 13 also records the given data as far as the 
sector A4 while searching tracks as occasion demands. 
Read Verification and Defective Sector Substitution (Step S7) 
(13) During the recording operation at step S6, the CPU 13 performs a read 
verification with respect to the recorded sectors in units of one or 
several sectors. As described previously in (5), the data are reproduced 
from the recorded sectors and stored in the RAM 11b. At this time, the 
error correction circuit 10 performs no error correction. 
The CPU 13 causes the data coincidence comparator 23 to compare the 
recording data stored in the RAM 11a and the reproducing data stored in 
the RAM 11b with each other and counts the number of errors of the data. 
If the number of errors exceeds a reference value, the sector B2 is 
regarded as a defective sector and the sector RA2 in the defective sector 
substitute region 27 is substituted therefor. In a substitute recording, 
the data in the RAM 11a are recorded on the sector RA2 in the same manner 
as step S6. (The read verification may be performed in such a manner that 
upon correction of errors by the error correction circuit 10, the quality 
of the recorded sectors is checked by detecting the number of errors.) 
Recording of Directory (Step S8) 
(14) Upon termination of the data recording, the CPU 13 adds to the file 
control information DIRa the address information of the sectors on which 
the data (b) have been recorded. This address information is recorded from 
the sector A2 to the sector A6 as a new directory DIRb. As occasion 
demands, the read verification and the defective sector substitution are 
performed in the same manner as step S7. 
Rewriting of Disc Control Information (Step S9) 
(15) The CPU 13 renews the contents 32 of the disc control track 25 i.e., 
the address information of the latest recorded sectors in the directory 
region 26, the data region 28 and the defective sector substitute region 
27, as shown in FIG. 5. More specifically, the addresses (A1), (A3) and 
(RA1) are rewritten to (A6), (A4) and (RA2), respectively. 
After the CPU 13 has searched the disc control track 25, it makes the 
rewriting signal 107 valid and sets the sector address S1 of the disc 
control track 25 to the register 14. The CPU 13 also sets a write command 
to the register 16. Upon rotation of the optical disc 1, when the target 
sector is detected by the address coincidence circuit 15, the write gate 
signal 102 is inputted from the gate generating circuit 17 into the data 
modulator 8. The disc control information to which the error correction 
codes have been added by the error correction circuit 10 is modulated by 
the data modulator 8. The modulated signal is inputted into the laser 
driving circuit 4 via the AND gate 19 and the OR gate 21 and is recorded 
by the optical head 3. Furthermore, the CPU 13 alters the address value to 
be set to the register 14 from S1 to S2 and then to S3 so that the 
recording may be performed plural times. In this way, the rewritable disc 
control track 25 is rewritten. 
It is to be noted here that in the above-described embodiment, although the 
file management including the directory management is performed by the CPU 
13, the directory may be controlled by a host CPU. The processing in this 
case is the same as that of the above-described embodiment except that the 
readout and recording of the directory and the data transfer are conducted 
via the interface circuit 12. 
It is also to be noted that in the above-described embodiment, although the 
designation of the "WORM type" is recorded on the control track 24, a 
cartridge accommodating the optical disc may be provided with an 
identification hole or holes for identifying the mode of use of the 
optical disc. 
As shown in FIG. 7, for example, the type of an optical disc can be 
designated by detecting the state of two identification holes 41a and 41b 
formed in a lower wall of a cartridge 40 using any suitable detector means 
42 opposed to the identification holes 41a and 41b. 
Table 1 indicates that the type of an optical disc can be designated by the 
two identification holes 41a and 41b. 
TABLE 1 
______________________________________ 
Type of Disc Hole 41a Hole 41b 
______________________________________ 
Rewritable Type open open 
Designation of "WORM" 
close open 
Type in Rewritable Disc 
"WORM" Type open close 
Reproduction Type close close 
______________________________________ 
In Table 1, when both the identification holes 41a and 41b are opened, a 
disc accommodated in the cartridge 40 is regarded as a rewritable disc. 
From Table 1, it is possible to identify the type of any other discs. 
As is clear from the above, according to the present invention, since the 
latest recorded sectors in an optical disc or the first unrecorded sectors 
immediately after the recorded sectors can rapidly be detected, a write 
processing for a file can be performed at a high speed. In particular, the 
present invention exhibits a greater effect with the increase of data 
recorded on the optical disc and provides a method of detecting unrecorded 
sectors which is suitable for a large capacity optical disc. 
In addition, the present invention is free from the problem of a crosstalk 
between adjoining tracks, which occasionally occurs when unrecorded 
sectors immediately after recorded sectors are detected using envelopes of 
respective recording signals. Accordingly, the present invention can 
readily narrow tracks in an optical disc. 
Although the present invention has been fully described by way of examples 
with reference to the accompanying drawings, it is to be noted here that 
various changes and modifications will be apparent to those skilled in the 
art. Therefore, unless such changes and modifications otherwise depart 
from the spirit and scope of the present invention, they should be 
construed as being included therein.