Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2001-07-20
2004-11-23
Tran, Thang V. (Department: 2653)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S044260, C369S053200
Reexamination Certificate
active
06822936
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to technique for reproducing or recording data from/to an optical disc.
For a medium for recording information, a magnetic tape and a disc can be given.
For the magnetic tape, a magnetic tape on which analog signals are serially recorded for a long time such as one used in VTR is well-known.
In the meantime, for the disc, an optical disc on which digital information is recorded can be given, it is used for an external storage of a computer and an apparatus for recording or reproducing an aural signal or a picture signal to/from an optical disc has been manufactured. As information can be recorded or reproduced to/from an optical disc at random, compared with a magnetic tape on which information is serially recorded, the optical disc has a merit that access to information is promptly enabled.
The above-mentioned optical disc has various types such as a compact disc (CD) and a digital video disc (a digital versatile disc) (DVD), for CD, a compact disc read only memory (CD-ROM), a compact disc-recordable (CD-R) and CD-rewritable (CD-RW) are known and for DVD, there are single-layer DVD-read only memory (DVD-ROM), dual-layer DVD-ROM, DVD-recordable (DVD-R), DVD-random access memory version 1.0 (DVD-RAM1) DVD-RAM2, DVD−RW and DVD+ReWritable (DVD+RW) (a rewritable DVD standard settled by Sony Corporation, Philips Electronics, Hewlett Packard, Mitsubishi Chemical Industries, Ltd., Ricoh Co., Ltd. and Yamaha Motor Co., Ltd. and called Phase-Change ReWritable).
As some of these plural types of optical discs are different in a method of recording and reproducing information, each optical disc is required to be switched. Therefore, the type of an optical disc to/from which information is to be recorded or reproduced is required to be discriminated.
For reference examples of discriminating an optical disc, Japanese unexamined publication No. H11-306650, No. H10-334574, No. H9-44982 and No. H8-249801 can be given.
SUMMARY OF THE INVENTION
However, in the above-mentioned reference examples, technique for discriminating a disc the reflected light quantity, the distance to a recording face and the recording track pitch of which are small is not referred and for a discriminating method, realizing means is not disclosed.
For example, DVD-RAM which is DVD-RAM1 or DVD-RAM2 and DVDRW which is DVD−RW or DVD+RW are substantially equal in reflected light quantity and distance to a recording face.
For recording track pitch, each track pitch of DVD-RAM and DVDRW is also smaller than each track pitch of CD and DVD.
Therefore, for a method of discriminating DVD-RAM and DVDRW, a new discriminating method is required to be discussed in addition to a method based upon reflected light quantity, distance to a recording face and recording track pitch.
Japanese published unexamined patent publication No. H11-306650 discloses a method of synthetically discriminating a disc after beams are once necessarily emitted from both laser beam sources for CD and for DVD and reflected signals based upon reflected light by both laser beam sources for CD and for DVD, a focus error signal and a tracking error signal are all acquired, however, the process is complex.
The object of the invention is to solve the above-mentioned problems and to provide disc discriminating method and apparatus by which an optical disc can be easily discriminated.
To achieve the object of the invention, a disc discriminating method according to the invention includes a step for discriminating the type of an optical disc installed in an optical disc unit based upon the reflectance, a step for discriminating the type of the optical disc based upon the time of a reflected signal from the surface of the optical disc and the time of the reflected signal from the recording face and a step for discriminating the type of the optical disc based upon a tracking error signal acquired from the optical disc.
Further, in addition to the above-mentioned steps, a step for determining the number of recording layers of an optical disc based upon a focus error signal acquired from the recording face of the optical disc and/or a step for discriminating the type of the optical disc depending upon the amplitude values of the reflected lights of laser beams from different lasers may be also together or selectively added.
First, in the step for discriminating the type of the optical disc based upon a tracking error signal acquired from the optical disc, the amplitude of a push-pull tracking error signal is acquired in a state in which focus servo is executed, is compared with a predetermined value and the type of the optical disc is discriminated.
That is, some optical discs are different in the sensitivity of a push-pull tracking error signal and as the difference in the sensitivity makes difference in the amplitude value of the tracking error signal, an optical disc can be discriminated based upon the difference.
For example, it is known that when DVD-RAM which is DVD-RAM1 or DVD-RAM2 and DVDRW which is DVD−RW or DVD+RW are compared, DVD-RAM is larger than DVDRW in the amplitude value of the tracking error signal.
Therefore, in case the amplitude of a tracking error signal is larger than a predetermined value, an optical disc is judged as DVD-RAM and in case the amplitude is smaller than the predetermined value, the optical disc can be judged as DVDRW.
Next, in the step for discriminating the type of an optical disc based upon the reflectance of the optical disc, the type of the optical disc is discriminated by determining whether the amplitude of a focus error signal acquired from the optical disc is larger than a predetermined value or not.
Generally, it is known that when optical discs are sorted in the order of higher reflectance, they are sorted in the order of CD, single-layer DVD (however, as difference in reflectance between CD and single-layer DVD is small, it may be also described that they are equal in reflectance), CD-R, dual-layer DVD, CD-RW, DVDRW (DVD−RW or DVD+RW) and DVD-RAM (however, as difference in reflectance among CD-RW, DVD-RAM and DVDRW is small, it may be also described that they are equal in reflectance).
Therefore, the type of an optical disc can be discriminated by presetting the amplitude values for comparison of focus error signals from these optical discs and comparing the preset amplitude value and the amplitude of a focus error signal from each optical disc.
For example, in the step for discriminating the reflectance of an optical disc, CD and single-layer DVD can be discriminated as an optical disc the reflectance of which is large, and CD-RW, DVDRW and DVD-RAM can be discriminated as an optical disc the reflectance of which is small.
In the step for discriminating the type of an optical disc, as there is difference between time until a reflected signal from the surface of the optical disc is acquired and time until a reflected signal from the recording face of the optical disc is acquired, the type of the optical disc is discriminated based upon the difference between the times.
For example, for CD and DVD, it is generally known that CD is larger in the difference between the times.
Therefore, for CD and DVD, in case the difference between the times is longer than predetermined time, the optical disc can be judged as CD and in case the difference is shorter, the optical disc can be judged as DVD.
In the step for determining the number of recording layers of an optical disc based upon a focus error signal acquired from the recording face of the optical disc, the number of focus error signals acquired when an optical pickup provided to the optical disc unit is brought close to the installed optical disc or is separated from it is counted.
For example, DVD the number of focus error signals acquired from the recording face of which is one can be determined as single-layer DVD and DVD the number of focus error signals acquired from the recording faces of which is two can be determined as dual-layer DVD.
In the step for discriminating
Fukuda Hirotoshi
Ikeda Takeshi
Ono Kazuhiko
Hitachi , Ltd.
Townsend and Townsend / and Crew LLP
Tran Thang V.
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