Method and apparatus for preventing copying of an optical disk

A method and apparatus for preventing copying of an optical disk. A software program and the basic data necessary for executing the program, as well as an erasing program are nonrewritably recorded in advance on a predetermined region of the disk. The erasing program attempts to erase the non-rewritable portion, which has no effect on the original disk, but will erase that portion of a disk which is copied. Thus, if the software program and the basic data for executing the program are copied without authorization, the copy disk is prevented from being used.

TECHNICAL FIELD 
This invention relates to an optical disk capable of optically recording 
and reproducing data, and an optical disk device adapted to record and 
reproduce data using the optical disk as the recording medium. 
BACKGROUND ART 
Programs for performing desired data processing, including basic programs, 
such as, above all, operating systems (OS), various programming languages, 
simplified program languages or word processeors, or the basic data 
indispensable for these programs, such as dictionary data, pattern data 
for Chinese characters or parameter data for pattern recognition, although 
not in need of being rewritten in a manner distinct from a variety of 
general data that are to be processed, occasionally require some form of 
write inhibit processing, in order to prevent inadvertent rewriting of the 
contents by mistaken operation. To this end, in a magnetic disk, such as a 
so-called floppy disk, the basic program or the basic data are protected 
by specifying the possible presence of write inhibition for each file by a 
software technique. However, the write protection implemented by the 
software technique may be cancelled rather easily by the software such 
that writing on a file specified for write inhibition may occasionally 
occur during, for example, program runaway or upon the occurrence of 
software errors. Therefore, for more reliable protection, a disk having 
the program and the basic data recorded thereon is provided as a so-called 
program disk separately from the data disk and a write inhibit measure 
such as a mechanical or hardware technique employing a so-called protect 
seal or protect notch is frequently applied to the program disk in its 
entirety. 
It is noted that, as disclosed, for example, in the Japanese Pat. 
Publication KOKAI No. 100249/1983, there has been proposed an optical 
information recording carrier which is provided with signal tracks 
composed of pits dedicated to reproduction for facilitating adjustment of 
the recording/reproducing optical system. 
Recently, a recording medium having an extremely high recording density, 
such as an opto-magnetic disk, has made its debut. With an optical disk 
having ultra-high recording density, it is not an effective utilization of 
the disk's recording capacity to prepare a disk dedicated to a program 
file to inhibit writing thereon. The basic program such as the 
aforementioned OS is formed by tens to hundreds of kilobytes, whereas the 
basic data is usually formed of hundreds of kilobytes, so that, even when 
several basic programs and data are recorded in combination, a recording 
capacity on the order of several megabytes suffices. However, an optical 
disk usually has a recording capacity amounting to several hundreds of 
megabytes, which is larger by approximately a hundred times than that 
required for the basic data or program. Therefore, when an optical disk is 
non-rewritably set as a so-called program disk, recording uses only a 
small portion of the recording capacity, while the remaining major portion 
is not used for recording, which is not economical. Therefore, one must 
resort to designating the write inhibit for each file for protection 
against mistaken writing by a software technique, which has a drawback in 
that it has an insufficient protection capability against software errors, 
as mentioned above. 
On the other hand, various other copy inhibit measures are used to prevent 
duplication without authorization. However, the risk remain extremely high 
that the program disk will be duplicated and illicitly used by other than 
the authorized users with the aid of a copy program. 
The present invention has been made with the above in mind and is intended 
to provide an optical disk wherein an erasure program for the record 
regions of the disk is nonrewritably recorded on a writable optical disk, 
along with the software program or basic data, to realize powerful write 
protection for the software program or the basic data, while inhibiting 
the duplication of the disk without authorization. 
DISCLOSURE OF THE INVENTION 
To accomplish the above object, the present invention provides an optical 
disk allowing data recording and reproduction, an erasure program for 
executing an erasure of record regions of the disk which is previously 
recorded non-rewritably at a prescribed region on the disk, and a software 
program adapted for handling data recorded on the disk or the basic data 
required for executing the program. According to the present invention, an 
erasure program for executing the erasure of the non-rewritable recording 
regions of the optical disk is previously non-rewritably recorded on the 
same non-rewritable region on the disk, along with a file the rewriting of 
which is not required or desired to be inhibited, such as the software 
program or the basic data, so that a powerful and reliable write 
protection as compared with simple protection by software may be 
implemented. When the record contents of the optical disk are duplicated 
and the copy disk is used, the software program and the basic data are 
erased by the erasure program so that an illicit or unauthorized use of 
the copy disk is prohibited.

BEST MODE OF PRACTICING THE INVENTION 
By referring to FIGS. 1 to 3, certain embodiments of the optical disk and 
the optical disk device of the present invention will be explained. 
Referring to FIG. 1, the optical disk 1 is capable of opto-magnetically 
recording and/or reproducing signals. Concentrically or spirally extending 
tracks are divided into prescribed lengths or prescribed angles for 
defining a plurality of sectors. An ID portion 2 in which ID codes 
including track or sector addresses are recorded, is prerecorded and 
formed (pre-formatted) as by so-called embossing at the leading position 
of each of these sectors. In a region of the innermost track of the 
optical disk 1, a so-called lead-in portion or a disk ID 3 is recorded. 
Adjacent to the disk ID towards the outer periphery is a socalled TOC 
(table of contents) portion 4 in which index information concerning the 
disk record contents is recorded. The region between an outer peripheral 
position a of the TOC portion 4 and a position b separated from the 
position a towards the outer periphery a predetermined distance is a 
non-rewritable read-only memory or ROM 5. The remaining region, the 
outermost peripheral position c of the disk, is a rewritable RAM 6 adapted 
for realizing the functions proper to the opto-magnetic recording type 
disk 1. 
The ROM 5 is so designed that signals cannot be written physically therein 
by an optical pickup head of the user's disk device. For example, the 
signal recording system adopted in the ROM 5 is such that, similarly to 
the preformated ID 2 in each sector, signals are recorded as physical 
changes in shape by forming pits or holes on the recording surface by a 
so-called embossing operation. However, while the address data etc. of the 
sector IDs 2 is the data used in the optical disk device, such as a disk 
controller, the contents recorded in the ROM 5 are programs or data 
exchanged with e.g. a host computer outside the disk device and an erasure 
program for executing the erasure operation of the recording regions. 
Thus, in the ROM 5, there is previously recorded and formed by the disk 
suppliers an erasure program adapted for designating and erasing the 
recording regions in the ROM 5, in addition to a basic software program, 
such as the aforementioned OS, programming languages, simplified program 
languages or word processor softwares, and data such as dictionary data or 
patterns of Chinese characters, that are indispensable to these programs. 
It is noted that information indicating whether the optical disk is of the 
type having the aforementioned ROM 5 is written in the disk ID 3, such 
that, when the disk system is put into position for use by the user or 
initialized by a resetting operation, the optical pickup head first reads 
the disk ID 3 to determine if the optical disk is provided with the ROM 5. 
In the TOC portion 4, the inner peripheral foundary position a and the 
outer peripheral boundary position b are recorded. 
The diagrammatic construction and operation of the essential portion of the 
system which is adapted for recording and/or reproducing the optical disk 
on which the boundary positional information of the region of the ROM 5 is 
recorded, will be explained by referring to FIGS. 2 and 3. 
On starting the use of the optical disk 1, the optical pickup head 10 scans 
the disk ID 3 of the disk 1 as described hereinabove to reproduce the 
record contents by a signal reading circuit 11. Depending on the 
reproduced disk ID information, the disk controller 12 determines whether 
the optical disk 1 now in use is or is not of the type having the ROM 5 
(steps S.sub.1 and S.sub.2 in FIG. 3). When the result is NO (that is, 
when the disk is not provided with the ROM) the customary disk control 
operation is performed. Conversely, when the result is YES, the TOC 
portion 4 of the optical disk 1 is read to determine the inner and outer 
peripheral boundary positions of the ROM 5 to store the boundary position 
information in a memory (steps S.sub.3 and S.sub.4 in FIG. 3). The 
contents of the ROM 5 are then read and the disk controller 12 executes 
automatically the erasure operation of the ROM by the erasure program 
afforded as the record contents of the ROM 5, after which the host 
computer 20 executes the main program, such as word processing, stored as 
the record contents of the ROM 5 (steps S.sub.5, S.sub.6 and S.sub.7). 
It is noted that the optical disk device is designed so as to exchange data 
or control signals with exterior devices, such as the host computer 20, 
through the disk controller 12, while the signals from the optical pickup 
head 10 are transmitted to the disk controller 12 through a signal readout 
circuit 11. Responsive to control commands from the host computer 20, the 
disk controller 12 controls a laser driver 13 and a head shift control 
circuit 14 to perform control operations in the read, write and erase 
modes by the optical pickup head 10. The head shift control circuit 14 
also operates to drive the head shift motor 15 into rotation to control 
the shifting of the optical pickup head 10 radially on the disk by way of 
a head supporting plate 16. 
In the present embodiment, when an erasure operation is automatically 
executed on the non-rewritable ROM 5 of the optical disk 1, the record 
contents of the ROM 5 cannot be rewritten or erased, while any adverse 
effects by the mistaken operation, such as destruction of the program or 
basic data can be completely prevented so that the powerful write 
protection of the data in the ROM 5 is realized. Since the ROM 5 and the 
RAM 6 exist together in one disk, 1 a program disk and a data disk may be 
combined into one disk to provide an optical disk convenient in practical 
application. When the record contents of the optical disk 1 are copied to 
another rewritable optical disk such as an opto-magnetic disk to produce a 
duplicated disk, the erasure program is executed at the step S.sub.6 for 
automatically erasing the contents of the copied ROM portions so that use 
of a disk copied without authorization is prohibited.