Dynamic information storage or retrieval – Binary pulse train information signal – Binary signal gain processing
Utility Patent
1998-07-20
2001-01-02
Edun, Muhammad (Department: 2753)
Dynamic information storage or retrieval
Binary pulse train information signal
Binary signal gain processing
C369S047360
Utility Patent
active
06169717
ABSTRACT:
BACKGROUND OF THE INVENTION
In general, there are several forms of optical disk systems in use today, including: a DVD system, such as a digital video (or versatile) disk system, a DVD-ROM system, a DVD-RAM system, and a compact disk (CD) system, such as a compact disk player (CDP) system or a CD-ROM system.
In a conventional optical disk reading apparatus, picture quality is adversely affected when the optical disk is scratched or when there is a manufacturing defect in the optical disk. Although digital signal processor (DSP) circuits employing error correction attempt to cure such defects, their applications are somewhat limited.
Data is commonly stored on an optical disk in holes, or pits and is modulated according to standard formats, for example the widely-used eight-to-fifteen modulation (EFM). In a defective, or non-standard, optical disk, in particular, a coarsely-copied optical disk, the depth of a pit does not meet standards. Accordingly, the level of an optical signal reflected from the optical disk is considerably lowered. Furthermore, the level becomes even lower as the speed of the optical disk increases. Accordingly, an error exists in the full period T′ of the EFM signal. In the CDP, since the full period of a normal disk is 693 ns, but the full period of a coarse disk is 550 ns-650 ns, in the case of 3T (where T denotes the period of the reference clock signal), T′ deviates from a sampling error margin range. Therefore, when a data slice is performed in an EFM comparator, it is difficult to estimate a correct amount of asymmetry offset.
In a conventional optical disk reading apparatus, the EFM full period error is corrected using an error correction code, a radio frequency (RF) equalizer or an RF automatic gain controller. However, the conventional forms of correction suffer from several shortcomings which limit the effectiveness of error correction.
SUMMARY OF THE INVENTION
To solve the above problem, it is an object of the present invention to provide an optical disk reading apparatus and method having a function of compensating for full period error in an EFM signal.
Accordingly, the inventive apparatus provides an optical disk reading apparatus adapted for a full period error compensation, comprising an RF amplifying means for converting an optical signal reflected from an optical disk into an electrical signal, a signal converting means for converting the analog electrical signal into a digital signal and outputting the converted digital signal as a modulated signal, for example an EFM signal, a full period compensating means for compensating for the errors of the full periods of the EFM signal and outputting the error compensated EFM signal as a compensated EFM signal, and an error correcting means for correcting the errors of the compensated EFM signal using an error correction code.
The inventive method provides a method of operating an optical disk reading apparatus having a full period compensating function, comprising the steps of (a) converting an optical signal reflected from an optical disk into an electrical signal, (b) obtaining a modulated signal, for example an EFM signal, by converting the analog electrical signal into a digital signal, (c) obtaining a compensated EFM signal by compensating for errors of the full periods of the EFM signal, and (d) correcting the errors of the compensated EFM signal using an error correcting code.
REFERENCES:
patent: 5532991 (1996-07-01), Sasaki
patent: 5761171 (1998-06-01), Tobita
Jang Young-wook
Kim Je-kook
Shin Jeong-Cheol
Edun Muhammad
Samsung Electronics Co,. Ltd.
Samuels , Gauthier & Stevens, LLP
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