Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2000-09-19
2003-12-23
Hindi, Nabil (Department: 2655)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S059250
Reexamination Certificate
active
06667939
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disc drive system capable of processing both an optical disc having a data protection function for preventing data from miss-erasure and alteration and an optical disc without such a data protection function.
2. Description of the Related Art
An example of a conventional optical disc drive system will be described with reference to
FIGS. 3 and 5
.
FIG. 3
is a block diagram showing an example of a conventional optical disc drive system. Light emitted from a laser
25
(about 660 nm in wavelength for DVD-RAM) constituting a portion of an optical head
2
passes through a collimator lens
24
to be collimated to parallel light beams
22
. A light beam
22
is focused upon an optical disk
11
via an objective lens
23
to form a spot
21
. The reflected light beam
22
is sent to a servo detector
26
and a signal detector
27
via a beam splitter
28
and a hologram device
29
. Signals detected with the detectors are added or subtracted to form servo signals such as a tracking error signal and a focus error signal which are input to a servo circuit. In accordance with the input tracking error signal and focus error signal, the servo circuit controls the positions of the objective lens
31
and optical head
2
to set the optical spot
21
to a target read/write area. An addition signal of signals output from the detector
27
is input to a signal reproduction block
41
. The input signal is subjected to filtering and equalizing by a signal processing circuit to be digitized thereafter. This digital signal is processed by an address detector and a demodulator. In accordance with the address signal detected by the address detector, a microprocessor calculates the position of the optical spot
21
on the optical disc
11
and controls an automatic positioning means to move the optical head
2
and optical spot
21
to the target read/write unit area (sector).
If a command from a host to the microprocessor is a write command, the microprocessor receives write data from the host and stores it in a memory, and controls the automatic positioning means to move the optical spot
21
to the target write area. After the microprocessor confirms from the address signal supplied from the signal reproduction block
41
that the optical spot is correctly positioned at the data write area, the microprocessor controls a laser driver and the like to write the data stored beforehand in the memory into the target write area.
As shown in
FIG. 6
, address data is written in each read/write unit area at the start field thereof. By detecting this address data as the address signal, it is possible to check the position of an optical spot immediately before the data is written.
FIG. 5
is a flow chart illustrating the operation of the optical disc drive system, by taking as an example an optical disc drive system for driving a rewritable type DVD-RAM stipulated by International Standards ISO/IEC-16824.
As a disc is loaded or a power of the optical disc drive system is turned on, the optical disc drive system first executes a process of identifying the type of the medium. This system generally has a read function not only for DVD-RAM media but also for read-only type media such as CD-ROM and DVD-ROM. Therefore, the optical disc drive system first executes the identification process to identify the type of the loaded medium. The identification process changes with each system. For example, one system identifies the medium type from a reflectivity and the analog characteristics of the reproduced signal such as a focus error signal, whereas another system identifies the medium type from the contents (data) read from a disc physical information area in a disk substrate.
If the medium type is identified as a rewritable type, i.e., DVD-RAM, the optical disc drive system reads data recorded in a defect management area to check whether the optical disc is already formatted. If unformatted, it stands by until a format command is supplied from the host or user.
If formatted, the optical disc drive system executes a read/write preparation process such as a calibration process and a logical consistency check process, and thereafter waits for a command from the host or user. Upon reception of any command, the optical disc drive system checks the type of the command. If it is a write command, a write process is executed, whereas if it is a read command, a format command or an eject command, then a corresponding process is executed. These processes are usually terminated normally. However, if the write operation were failed from unexpected reasons, an error process such as a retry process and a replacement process is executed.
Generally, in the case of DVD-RAM, after the write process, the written data is read to verify whether the data was correctly written, and if necessary the replacement process using other read/write unit areas is executed. In this manner, the reliability of written data is improved. Management information on reassignment of read/write unit areas is recorded in a specific area (defect management area) of the disc.
DVD-RAM is used with such a highly reliable optical disc drive system, and data written can be basically rewritten freely. There is, therefore, a possibility that important written data is erased or altered because of miss-operation by a user or a failure by the host.
As one protective method, a so-called “write-protect function” is known. However, this write-protect function” can be released by a user freely. It is therefore impossible to prevent data from being destroyed by a miss-operation of a user.
An example of a magneto optical disc used for solving the above problem will be described. A magneto optical disc is a rewritable type storage medium which can erase or rewrite user data in a user data area. There are needs for using a magneto optical disc as a write-once type storage medium which cannot erase or write user data.
According to CCW System (or MO-WORM System) stipulated in ISO-IEC 11560, media type identification data representative of an magneto optical disc type is recorded in a control data area outside of a user data area. Whether a magneto optical disk is a rewritable type or a write-once type is determined from this media type identification data.
As a write-once type magneto optical disk is loaded, the magneto optical disc drive system inhibits an erase operation and a rewrite operation of the user data area with user data already written. Namely, this system has a data protection function for preventing erase and overwrite of a magneto optical disc which is originally of a rewritable type. The same magneto optical disc drive system can access both the write-once magneto optical disk with the data protection function and the rewritable type magneto optical disc. Application field of the magneto optical disc can be broadened and the media cost can be reduced.
However, if a similar method is applied to the optical disc drive system stipulated only with the rewritable type specifications, such as DVD-RAM, there arise the following problems.
The specifications for rewritable type discs exist already and are prevailing in markets. Optical disc drive systems for driving such optical discs in conformity with those specifications also exist already. Under such environments, even if media type identification data is newly registered in a media type identification area similar to magneto optical discs, the already existing systems cannot be altered and cannot drive optical discs with the data protection function.
Not all optical disc drive systems use the media type identification data for identifying the medium type. Even if new code data still not defined is recorded as the media type identification data, a conventional optical disc drive system cannot recognize the meaning of the code data and the operation becomes undifined.
DVD-ROM is a read-only medium. It generally requires a cost of hundreds of thousands Yen and takes a time of one day or longer to write data in a singl
Hindi Nabil
Hitachi , Ltd.
Mattingly Stanger & Malur, P.C.
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