Dynamic information storage or retrieval – Binary pulse train information signal – Having specific code or form generation or regeneration...
Reexamination Certificate
1998-11-03
2001-05-15
Huber, Paul W. (Department: 2651)
Dynamic information storage or retrieval
Binary pulse train information signal
Having specific code or form generation or regeneration...
C369S124020
Reexamination Certificate
active
06233214
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to information data recording and/or reproducing methods for recording information data on a recording medium and reproducing such information data.
2. Description of Related Art
A partial response scheme is widely known as a scheme for recording and reproducing information data on and from a recording medium such as an optical disc, a magnetic disc, or the like.
FIG. 1
illustrates a recording/reproducing system which employs a PR(
1
,
1
) scheme, one of partial response schemes.
First in a recording system, a precoder
10
performs a predetermined logical operation on information data a(k) supplied from an information source, not shown, to convert the information data a(k) into recording data b(k) for recording which is supplied to a recording head
20
.
The precoder
10
, which consists of, for example, a subtractor
11
, a mod
2
processor
12
, and a delay element
13
, converts the information data a(k) into the recording data b(k) by the following logical operation:
b(k)={a(k)−b(k-
1
)}mod
2
(1)
where
a(k): information data at time k;
b(k): recording data at time k; and
b(k-
1
) : recording data at the previous time (k-
1
).
“mod” in the above equation is an operator representing a residual operation.
For example,
A mod B (2)
represents a residue produced by dividing “A” by “B,” and the residue is output as its operation result. In this operation, it is assumed that the operation result has the same polarity as that of “B.” In other words, the recording data b(k) is a residue produced by dividing {a(k)−b(k-
1
)} by two.
The recording head
20
irradiates recording laser light corresponding to the recording data b(k) onto a recording surface of a recording disc
30
which is driven to rotate at a predetermined velocity.
Assume herein that a so-called pit position recording is performed, where data is recorded as the presence or absence of a pit at each recording point.
For example, the recording head
20
irradiates recording laser light to the position of a recording point when the recording data b(k) is at logical level “1,” and does not irradiate the recording laser light at the position of this recording point when the recording data b(k) is at logical level “0.” In this case, pits Pt are formed only at the positions of recording points which were irradiated with the recording laser light, as illustrated in FIG.
2
.
A reproducing head
40
in a reproducing system irradiates reproducing laser light onto a recording surface while tracing a recording track, and photo-electrically converts the reflected light from the recording surface to produce a read signal corresponding to a sequence of pits which are formed on the recording track.
It should be noted that in the PR(
1
,
1
) scheme, two adjacent recording points simultaneously exist on the same track within a range of a reading beam spot SP formed on a recording surface by the irradiation of reproducing laser light, as illustrated in FIG.
2
. Thus, a read signal is produced at a level corresponding to the total sum of reflected light from each of these two recording points, i.e., the sum of recording data at each of the two recording points.
Here, when two binary recording data “0” and “1” are simultaneously read, a ternary read signal “0,” “1,” “2” is produced.
A level determining circuit
50
determines which of these three values a reading signal corresponds to, and supplies determination data c(k) in accordance with the determination result to a mod
2
processor
60
.
For example, when the levels of a read signal corresponding to the three values “0,” “1,” “2” are distributed about 0V (Volt), 1V, 2V, respectively, the level determining circuit
50
compares the read signal with two threshold values at 0.5V and 1.5V, samples the comparison result, and determines the levels of the ternary data.
The resulting determination data c(k) is expressed by:
c(k)=b(k)+b(k-
1
) (3)
The mod
2
processor
60
produces reproduced information data d(k) by performing the following residual operation on the determination data c(k):
d(k)=c(k)mod
2
(4)
As described above, this recording/reproducing system enables the reproduction of information data corresponding to each recording point even though the interval between respective adjacent recording points on the same track is narrower than the diameter of the reading beam spot SP. In other words, it is possible to increase the linear density by narrowing the interval between recording points.
This recording/reproducing system, however, cannot increase the recording density in the radial direction of a disc, i.e., cannot reduce the track pitch, so that the entire recording capacity of a disc cannot be increased so much.
In addition, since the foregoing PR(
1
,
1
) scheme produces a read signal at ternary levels, the level determining circuit
50
cannot correctly determine the level of the read signal if the read signal has a low S/N ratio.
OBJECTS AND SUMMARY OF THE INVENTION
The present invention has been made to solve the problem mentioned above, and its object is to provide information data recording and/or reproducing methods which are capable of correctly reproducing information data from a recording disc on which information data is recorded at a high density both through implementation of an increased linear density and a narrower track pitch.
An information data recording method according to a first feature of the present invention is provided for recording an M-value information data at recording points interspersed on recording tracks of a recording disc, wherein (m×n) recording points exist on n adjacent recording tracks (n is a natural number equal to or larger than two) including a target recording point and exist on m adjacent disc radial lines (m is a natural number equal to or larger than two) including the target recording point, and the method comprises the steps of subtracting each of recording data recorded at each of (m×n−1) recording points other than the target recording point from the information data, within the (m×n) recording points, to produce a subtraction result, performing a residual operation on the subtraction result with the value of M to derive a residue value, and recording the residue value as recording data to be recorded at the target recording point.
An information data recording method according to a second feature of the present invention is provided for recording binary information data at recording points interspersed on recording tracks of a recording disc, and comprises the steps of calculating a recording data b(j, k) to be recorded at a target recording point existing on a recording track j and existing on a disc radial line k from information data a(j, k) corresponding to the target recording point, recording data b(j, k-
1
) recorded at a recording point existing on a disc radial line (k-
1
) adjacent to the disc radial line k on the recording track j, recording data b(j-
1
, k) recorded at a recording point existing on the disc radial line k on a recording track (j-
1
) adjacent to the recording track j, and recording data b(j-
1
, k-
1
) recorded at a recording point existing on the disc radial line (k-
1
) on the recording track (j-
1
), with the following logical equation:
b(j, k)={a(j, k)−b(j, k-
1
)−b(j-
1
,k)−b(j-
1
, k-
1
)}mod
2
(5)
where mod represents a residual operation, and recording the recording data b(j, k) at the target recording point.
An information data reproducing method according to a first feature of the present invention is provided for reproducing recorded information data from a recording disc on which M-value information data is recorded at each of a plurality of recording points interspersed on recording tracks, and comprises the steps of simultaneously reading recorded information from (m×n) recording points existing on n adjacent recording tr
Huber Paul W.
Pioneer Electronic Corporation
Sughrue Mion Zinn Macpeak & Seas, PLLC
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