Dynamic information storage or retrieval – Binary pulse train information signal – Binary signal processing for controlling recording light...
Reexamination Certificate
2000-01-14
2003-04-08
To, Doris H. (Department: 2655)
Dynamic information storage or retrieval
Binary pulse train information signal
Binary signal processing for controlling recording light...
Reexamination Certificate
active
06545965
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a recording medium such as an optical disk for recording digital data as pits in high density, a recording apparatus for recording digital data on the recording medium, and a reproduction apparatus for reproducing the digital data recorded in the recording medium.
2. Description of the Related Art
A SCIPER (Single Carrier Independent Pit Edge Recording) system is known as a method for recording digital data in a recording medium such as an optical disk in high density.
In the SCIPER system, pits are arranged at a predetermined interval along the circumferential direction on the tracks of an optical disk, and the positions of the front edge and the rear edge of each pit are changed stepwise, respectively, in accordance with the digital data to be recorded. Namely, in the SCIPER system, the position of the pit itself is not changed but the positions of the front edge and the rear edge of the pit are changed, respectively, for recording digital data on the tracks. The front edge indicates the edge located at the front portion of the pit, and the front portion of the pit indicates the portion located in one of the circumferential directions of the optical disk. The rear edge indicates the edge located at the rear portion of the pit, and the rear portion of the pit indicates the portion located in the other circumferential direction of the optical disk.
FIG. 7
shows pits formed on an optical disk according to the SCIPER system. In
FIG. 7
, assume that the beam spot moves in the direction indicated by arrow a on the optical disk. The positions designated by reference numerals FE
1
to FE
3
in the pit PT constitute the front edge, and the positions indicated by reference numerals RE
1
to RE
3
constitute the rear edge. In
FIG. 7
, solid lines indicate the contour of the pits PT which are actually formed on the optical disk, and dotted lines indicate the other contour of the pits which are formed when the other recording symbols are assigned to these pits.
The pits PT shown in
FIG. 7
are arranged at a predetermined interval D
3
. The front edge of each pit PT represents a recording symbol having one of ternary levels of “−1”, “0” and “+1” by changing the position thereof in three steps. The rear edge of each pit PT also represents a recording symbol having one of ternary levels of “−1”, “0” and “+1” by changing the position thereof in three steps.
When the recording symbol is “−1”, for example, the front edge takes a position indicated by reference numeral FE
3
and thereby the length of the pit PT is shortened. When the recording symbol is “0”, on the other hand, the front edge takes a position indicated by reference numeral FE
2
, which is an intermediate position of the three positions. When the recording symbols is “+1”, the front edge takes a position indicated by reference numeral FE
1
and thereby the length of the pit PT is lengthened.
In similar fashion, when the recording symbol is “−1”, the rear edge takes a position indicated by reference numeral RE
1
and thereby the length of the pit PT is shortened. When the recording symbol is “0”, the rear edge takes a position indicated by reference numeral RE
2
, which is an intermediate position of the three positions. When the recording symbol is “+1”, the rear edge takes a position indicated by reference numeral RE
3
and thereby the length of the pit PT is lengthened.
When reproducing the digital data from an optical disk, the reproduction apparatus radiates a reproducing laser beam toward the optical disk thereby to form a beam spot SP on the pits PT as shown in FIG.
7
. At the same time, the reproduction apparatus moves the beam spot SP in the direction of arrow a in FIG.
7
. In this way, the reproduction apparatus detects an analog detection signal corresponding to the recording symbol recorded as a position of the front edge or the rear edge. As a result, the level of the analog detection signal is changed in three steps in accordance with the levels “−1”, “0” and “+1” of the recording symbol corresponding to the position of the front edge or the rear edge. The reproduction apparatus performs the filter operation for emphasizing the high frequency band of the analog detection signal, detects the levels of the three steps and reproduces the digital data.
Next, the level detection of the analog detection signal will be explained with reference to FIG.
8
.
FIG. 8
is a diagram showing waveforms of the analog detection signal. In
FIG. 8
, a multiplicity of signals that can be output as an analog detection signal are shown in overlapped form.
The reproduction apparatus sample-holds the analog detection signal at the timing indicated by T
1
, T
2
, T
3
and T
4
in FIG.
8
. The reproduction apparatus then compares the level obtained by sample-holding with preset threshold values, and determines which of “−1”, “0” and “+
1
” is indicated by the level.
The reproduction apparatus compares the level obtained by sample-holding with two threshold values “−0.5” and “+0.5”. If the level obtained by sample-holding is smaller than −0.5, the reproduction apparatus determines that the particular level represents “−1”. If the level obtained by sample-holding is not smaller than −0.5 but not larger than 0.5, the reproduction apparatus determines that the particular level represents “0”. If the level obtained by sample-holding is larger than +0.5, the reproduction apparatus determines that the level is “+1”.
The technique of the SCIPER system is described, for example, in Japanese Laid-open Publication No. Hei 6-76303.
On the other hand, a research is under way for the technique to make possible the recording and reproducing operation of higher density by combining the SCIPER system with the conventional RPR (Radial Direction Partial Response) system. The recording and reproducing operation by a combination of the SCIPER system and the RPR reproduction system is described, for example, in “Partial Response Recording in Radial Direction”, 1997 Optical Data Storage Conference Digest, pp. 42-43, (Apr. 1997).
Next, a pit arrangement of the optical disk and the reproduction of the digital data from the optical disk by the recording and reproduction technique of the combined SCIPER system and the RPR reproduction system will be explained with reference to
FIGS. 9A and 9B
.
FIG. 9A
is a plan view showing a pit arrangement of the optical disk according to the conventional recording and reproduction technique using the combined system of SCIPER and RPR, and
FIG. 9B
is a diagram showing waveforms of the analog detection signal. In
FIG. 9B
, a multiplicity of signals that can be output as an analog detection signal are all shown in overlapped form. However, only one of the multiplicity of waveforms shown in
FIG. 9B
is output as the analog detection signal. Further, the description below refers to the case in which the positions of the front and rear edges of each pit correspond to the recording symbols having one of ternary levels of “−1”, “0” and “+1”. Also, in order to indicate that the positions of the front and rear edges of each pit are changed in three steps in accordance with the recording symbol, all the three positions that each edge can take are indicated by solid lines in FIG.
9
A. The actual edge position of course is one of the three positions. This is also the case with
FIG. 10A
described later.
In the case where digital data are reproduced by the recording and reproduction technique combining the SCIPER system and the RPR reproduction system, the beam spot is arranged with the center thereof coincident with the center line CL
1
between adjacent two tracks T, and moved along this center line CL
1
. Thus, adjacent two tracks T are radiated at the same time by the laser beam.
Further, in the recording and reproduction technique combining the SCIPER system and the RPR reproduction system, the pit trains are in phase with
Morgan & Lewis & Bockius, LLP
Patel Gautam R.
To Doris H.
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