Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-01-28
2001-11-06
Hudspeth, David (Department: 2651)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S047350, C369S059210, C369S047260
Reexamination Certificate
active
06314074
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording information reproducing apparatus for reproducing recording information from a recording medium.
2. Description of Related Art
FIG. 1
is a diagram showing the structure of a conventional recording information reproducing apparatus.
In
FIG. 1
, a pickup
1
reads recording information from a recording disc
3
which is rotated by a spindle motor
2
and supplies a read signal obtained by the reading to an A/D converter
5
. The A/D converter
5
sequentially samples the read signal at a timing of a clock signal supplied from a PLL circuit
10
and supplies a read sampling value sequence obtained by the reading to each of the PLL circuit
10
and a decoding circuit
30
.
A phase error detecting circuit
11
in the PLL circuit
10
detects a phase error which develops in the read signal based on the read sampling value sequence sequentially supplied from the A/D converter
5
and supplies a phase error signal corresponding to the amount of the phase error to an LPF (low pass filter)
12
. The LPF
12
supplies an average phase error signal obtained by averaging the phase error signals to a frequency variable oscillator
13
. The frequency variable osillator
13
generates a clock signal having a frequency according to the average phase error signal and supplies it to the A/D converter
5
. The decoding circuit
30
is constituted, for example, by a Vlterbi decoder, and is operative to detect the read sampling value sequence as successive time series and to decode maximum likelihood binary reproduction data based on the detected time series.
In the recording information reproducing apparatus as mentioned above, the clock signal whose phase is synchronized with that of the read signal read from the recording disc
3
is generated by the PLL circuit
10
and the read signal is sampled by the clock signal, thereby obtaining the read sampling value sequence.
If, however, a linear recording density of the information recorded on the recording disc
3
is high, the read signal will be influenced by a rotation variation of the spindle motor
2
, an eccentricity of the recording disc
3
itself, or the like and a time base fluctuation will occur in the read signal. In such a case, if the PLL circuit
10
becomes unable to follow the time base fluctuation, a phase deviation develops in the read sampling value sequence generated from the A/D converter
5
. Therefore, residual errors may remain in the read sampling value sequence due to the influence of the phase deviation and a problem arises such that the decoding circuit
30
at a later stage cannot perform a very reliable decoding operation.
OBJECT AND SUMMARY OF THE INVENTION
The invention has been made to solve the problem described above, and it is an object of the invention to provide a recording information reproducing apparatus which can reduce a residual phase error in a read signal caused by an influence of a time base fluctuation.
According to the invention, there is provided a recording information reproducing apparatus for reproducing information data corresponding to recording information recorded on a recording medium based on a read signal read out from the recording medium, comprising: a PLL circuit for generating an oscillation signal whose phase is synchronized with that of a read sampling value sequence obtained by sampling the read signal at a timing according to a clock signal and using the oscillation signal as a clock signal; phase correcting means for obtaining a sampling value sequence derived at a time point when the phase in the read sampling value sequence is deviated by an amount corresponding to a phase error which occurs in the read sampling value sequence and supplying the sampling value sequence as a corrected read sampling value sequence; and decoding means for executing a decoding process to the corrected read sampling value sequence, thereby obtaining the information data.
REFERENCES:
patent: 5142377 (1992-08-01), Moriyama et al.
patent: 5412638 (1995-05-01), Koulopoulos et al.
patent: 5901128 (1999-05-01), Hayashi et al.
patent: 5963518 (1999-10-01), Kobayashi et al.
Chu Kim-Kwok
Hudspeth David
Perman & Green LLP
Pioneer Electronic Corporation
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