Optical disk, optical disk device, and optical disk...

Details Optical disk, optical disk device, and optical disk... Optical disk, optical disk device, and optical disk...

1999-02-04

2001-12-25

Hindi, Nabil (Department: 2753)

Dynamic information storage or retrieval

Binary pulse train information signal

Binary signal processing for controlling recording light...

C369S047180

Reexamination Certificate

active

06333905

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk, an optical disk device, and an optical disk recording method. The present invention is applied to, for example, a compact disk. By correcting the timing of a modulation signal according to a change pattern of a modulation signal, a jitter at the time of reproduction is reduced and recorded data can be surely reproduced.
2. Description of the Related Art
In a conventional compact disk, data to be recorded are subjected to data processing and thereafter subjected to an EFM (Eight-to-Fourteen Modulation) modulation. For a predetermined fundamental period T, a pit sequence having a period in the range of 3T to 11T is thereby formed. Thereby, audio data or the like, for example, are recorded.
Corresponding to this, a compact disk player irradiates a laser beam on the compact disk and receives a returned light therefrom. The compact disk player thus obtains a reproduced signal having a signal level changed according to the light quantity of the returned light, converts this reproduced signal to a binary value by using a predetermined slice level, and thus generates a binary signal. Furthermore, the compact disk player drives a PLL circuit in response to this binary signal to generate a reproduction clock and latches binary signals successively by using the reproduction clock. Thereby, the compact disk player generates reproduced data having a period in the range of 3T to 11T and corresponding to the pit sequence formed on the compact disk.
The compact disk player conducts data processing corresponding to the data processing conducted at the time of recording, on the reproduced data thus generated. In this way, the compact disk player reproduces audio data or the like recorded on the compact disk.
By the way, in the conventional compact disk player, a jitter is contained in the reproduced signal. It may be considered that this jitter occurs by various causes such as a noise of a laser beam used for readout, a thermal noise of an electric system, a disk noise or the like. The jitter reduces the phase margin of the reproduced signal. In an extreme case, the jitter makes it difficult to reproduce data correctly.
However, this jitter is essentially due to an inter-symbol interference caused by preceding and succeeding pits (Shigeo Kubota, “Aplanatic condition required to reproduce jitter-free signals in an optical digital disk system”, App. Optics 1987, Vol. 26, No. 18, pp. 3961-3970). The jitter changes according to the land and pit located before and behind the laser beam radiation position.
SUMMARY OF THE INVENTION
In view of the points heretofore described, the present invention has been made. The present invention attempts to propose an optical disk, an optical disk device, and an optical disk recording method capable of reducing a jitter caused at the time of reproduction and reproducing surely the recorded data.
In order to solve the above described problems, in an optical device and an optical disk recording method according to the present invention, the timing of a modulation signal is corrected according to a change pattern of the modulation signal.
Furthermore, in an optical disk, the position of an edge is changed from its fundamental position according to the pit length and the land length located before and behind the edge.
Furthermore, in an optical disk device and an optical disk recording method, the timing at which a laser beam is raised up to a light quantity for writing is corrected in an interlinked relation to light quantity switching of the writing operation.
Furthermore, in an optical disk, a high reflectance area and a low reflectance area are formed dependent on a difference in pit width. In order to correct a change of a returned light caused by this difference in pit width, pits to which the same data is assigned are formed so as to be different in pit length.
By correcting a timing of the modulation signal, a change caused in signal level at the time of reproduction can be corrected. If this timing correction is executed on the basis of the change pattern of the modulation signal, a reproduced signal can be corrected so as to correct an inter-symbol interference changing according to this change pattern. As a result, the jitter of the reproduced signal can be reduced.
So as to correspond to this in an optical disk, the position of an edge is changed from a fundamental position according to the pit length and the land length located before and behind the edge to thereby form the pit. Whereby, the pit shape is changed so as to correspond to the change pattern of the modulation signal. As a result, a jitter caused by inter-symbol interference can be avoided.
Furthermore, if the timing at which the laser beam is raised up to the light quantity for writing is corrected in an interlinked relation to light quantity switching of the writing operation, asymmetry changed by light quantity switching can be corrected.
So as to correspond to this, in an optical disk, a high reflectance area and a low reflectance areas are formed dependent on a difference in pit width. Thereby, characters or the like can be recorded on the information recording surface so as to be observable with eyes. If at this time pits to which the same data is assigned are formed so as to be different in pit length so as to correct a change of a returned light caused by this difference in pit width, asymmetry differing in the high reflectance area and the low reflectance area can be corrected.


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