Title: Recording medium and a recording system for the recording medium
Abstract: A recording/reproducing medium having grooves, a land formed between the grooves, and land prepits formed on the land in which each of said land prepits has a most optimum design condition where a ratio (LLP Level/offset) between a voltage amplitude (LLP Level) of a land prepit detection signal and an offset level (offset) of an RF signal becomes more than about or where an amplitude change of an RF signal through the land prepit becomes minimum. The recording/reproducing medium can be one of a DVD-R and a DVD-RW.
Patent Number: 6,952,393 Issued on 10/04/2005 to Muramatsu, et al.
| Inventors:
|
Muramatsu; Eiji (Saitama-ken, JP);
Kato; Masahiro (Saitama-ken, JP);
Sato; Makoto (Saitama-ken, JP)
|
| Assignee:
|
Pioneer Corporation (Tokyo, JP)
|
| Appl. No.:
|
274199 |
| Filed:
|
October 21, 2002 |
Foreign Application Priority Data
| Oct 23, 1998[JP] | 10-301965 |
| Current U.S. Class: |
369/275.4; 369/277 |
| Intern'l Class: |
G11B 007/24 |
| Field of Search: |
369/2754,275.3,275.1,442.7,442.5,444.1,442.8,442.9,443.4,443.5,288,277,442.6,471,532.3
428/641,644,645
|
References Cited [Referenced By]
U.S. Patent Documents
Other References
US 6,567,356, 5/2003, Kuroda et al. (withdrawn)
Patent Abstracts of Japan. vol. 1997, No. 05, May 30, 1997 for JP 9 017029 published
Jan. 17, 1997.
|
Primary Examiner: Neyzari; Ali
Attorney, Agent or Firm: Arent Fox PLLC
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATION
This application is a Divisional of application Ser. No. 09/758,393, filed Jan.
12, 2001, now U.S. Pat. No. 6,493,313, which in turn is a Continuation of application
Ser. No. 09/419,908, filed Oct. 18, 1999, now U.S. Pat. No. 6,181,672, the entire
specification, claims, and drawings of which are incorporated herewith by reference.
Claims
1. A recording/reproducing medium having grooves, a land formed between the grooves,
and land prepits formed on the land, wherein
each of said land prepits has a most optimum design condition where an amplitude
change of an RF signal through the land prepit becomes minimum.
2. The recording/reproducing medium according to claim 1, wherein the recording/reproducing
medium is one of a DVD-R and a DVD-RW.
3. A recording medium comprising:
an information recording track; and
preformed information which is formed on a portion deviated from the information
recording track in a radial direction,
wherein the preformed information has a most optimum design condition where an
amplitude change of an RF signal through the preformed information is minimalized.
4. The medium according to claim 1, wherein the most optimum design condition
is determined in terms of a length of the preformed information in a circumferential
direction, and a width and a depth of the information recording track.
5. The medium according to claim 3, wherein the most optimum design condition
is determined in terms of a length of the preformed information in a circumferential
direction, and a width and a depth of the information recording track.
6. A system for recording information on a recording medium including grooves,
a land formed between the grooves, and land prepits formed on the land, wherein
each land prepit has an optimum design condition where an amplitude change of an
RF signal through said land prepit is minimized.
7. A system for recording information on a recording medium including an information
recording track, and preformed information which is formed on a portion deviated
from the information recording track in a radial direction, wherein the preformed
information has an optimum design condition where an amplitude change of an RF
signal through the preformed information is minimized.
8. The system according to claim 6, comprising:
an objective which forms a light spot on the groove, the light spot having a
diameter larger than a width of the groove;
a photodetector which receives light reflected from the recording medium, and
generates a photodetection signal; and
an operation circuit which generates a land prepit detection signal and the RF
signal based on the photodetection signal.
9. The system according to claim 7, comprising:
an objective which forms a light spot on the information recording track, the
light spot having a diameter larger than a width of the information recording track;
a photodetector which receives light reflected from the recording medium, and
generates a photodetection signal; and
an operation circuit which generates a preformed information detection signal
and the RF signal based on the photodetection signal.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a recording medium and a recording and reproducing
system for the recording medium.
Heretofore, there is known the DVD (digital versatile disc),the DVD-R
(DVD WRITE ONCE) and the DVD-RW (DVD-Re-Writable) as the rewritable disc.
As shown in the Japanese Patent Laid-Open Publication No. 9-17029, the DVD-R
or
DVD-RW (hereinafter called DVD) has a spiral or co-axial groove for recording information,
a land between the grooves and a plurality of land prepits formed between the grooves.
The land prepit is provided with various sets of information such as the address.
In such a disc, it is possible to read the information recorded on the groove
and the information recorded on the land prepit at the same time.
However, there is a problem that signals reproduced from the information
recorded on land prepits affect the RF signal reproduced from the information recorded
on the groove as offset.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a recording medium wherein information
recorded on the groove and the land prepit can be accurately read out and a system
capable of recording and reproducing with accuracy.
According to the present invention, there is provided a recording medium
having a circular substrate, grooves formed on the substrate, a land formed between
the grooves, a plurality of land prepits formed between the grooves, wherein the
groove and the land prepit are formed so as to satisfy a following formula,
where Gw is the width of the groove, Lp is the length of the land prepit in
a radial direction of the substrate, Gd is the depth of the groove, λ is
the wave length of light used in a system for recording information on the recording
medium, and NA is the numerical aperture of an objective in the system.
The present invention further provides a recording medium having a circular substrate,
grooves formed on the substrate, a land formed between the grooves, a plurality
of land prepits formed between the grooves, wherein the groove and the land prepit
are formed so as to satisfy following formulae;
##EQU1##
##EQU2##
where Gw is the width of the groove, Lp is the length of the land prepit in
a radial direction of the substrate, Gd is the depth of the groove, λ is
the wave length of light used in a system for recording information on the recording
medium, and NA is the numerical aperture of an objective in the system.
The present invention still further provides a system of recording a medium having
a circular substrate, grooves formed on the substrate, a land formed between the
grooves, a plurality of land prepits formed between the grooves, wherein a wavelength
of light for recording information on the medium and a numerical aperture of an
objective of the system are provided so as to satisfy following formulae,
##EQU3##
##EQU4##
where Gw is the width of the groove, Lp is the length of the land prepit in
a radial direction of the substrate, Gd is the depth of the groove.
BRIEF DESCRIPTION OF DRAWINGS
FIG. 1
a is a perspective view of an optical DVD for explaining the present invention;
FIG. 1
b is a sectional view of the disc of FIG. 1
a;
FIG. 2
a is an enlarged plan view showing a part of the disc;
FIG. 2
b is a block diagram of a reproducing system;
FIGS. 3
a through 3
c are graphs showing waveforms of a
land prepit detection signal and an RF signal;
FIGS. 4
a through 4
c are graphs showing waveforms of a
land prepit detection signal and an RF signal detected from recorded mediums; and
FIGS. 5 through 13 are graphs for determining optimum conditions for the land
prepit are the groove of the medium.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring to FIGS. 1
a and
1b, the DVD has a transparent
plastic substrate
4 made of polycarbonate. On the substrate
4, there
is formed grooves
1 arranged in the circumferential direction DC, lands
2 between the grooves
1, and land prepits
3 on the land
2
formed at predetermined intervals.
Information such as video data or audio data is recorded in the groove,
and information such as address is recorded in the prepit.
On the underside of the substrate
4, there is formed a recording layer
5 of organic coloring matter or inorganic metal, a reflection layer
6
and a protecting layer
7. The laser light is applied to the groove passing
through an objective
8.
In accordance with the present invention, the width Gw of the groove
1,
the length Lp of the land prepit in the circumferential direction, and the depth
Gd of the groove are determined to particular values as described hereinafter.
Referring to FIG. 1 showing a part of the DVD and FIG. 2
b showing
a reproducing system for the DVD, a light spot SP has a diameter larger than the
width Gw of the groove
1 and disposed so that the center of the spot coincides
with the center line of the groove
1. Thus, information recorded on the
land prepit
3 can also be read as shown in FIG. 2
a.
The reproducing system has a photodetector
9 comprising four elements
9A,
9B,
9C and
9D for receiving the light reflected
from the disc, and adding and subtracting circuits
10 and
11 and
an adder
12. The spot of the reflected light is positioned such that the
center of the spot coincides with the center of the photodetector
9.
Here, the areas A and D in FIG. 2
a read the information on the groove
1, and areas B and C read information on the groove
1 and land prepit
3. The photodetector
9 produces signals A, B, C and D corresponding
to the areas A-D.
The adding and subtracting circuit
10 produces a land prepit signal SLp=(A+D)-(B+C),
the adding and subtracting circuit 11 produces a tracking error signal STE=(A+D)-(B+C),
and the adder 12 produces an RF signal SRF =A+B+C+D.
FIGS. 3
a,
3b,
3c show results of reproduction
experiments of the DVD-RW, where amplitude change of the land prepit signal SLp
and the RF signal SRF under the condition that the wavelength X of the spot SP
and the numerical aperture NA are constant.
In the experiment of FIG. 3
a, the prepit length Lp is 0.3 μm and
the groove width Gw is 0.25 μm, in FIG. 3
b the prepit length Lp is
0.3 μm, the groove width Gw is 0.3 μm, and in FIG. 3
c Lp=0.3
μm, Gw=0.4 μm.
From the graphs, it will be understood that the voltage amplitudes of the signals
SLp and SRF at the irradiation time t change with the prepit length Lp and the
groove width Gw.
FIGS. 4
a,
4b and
4c show results of experiments
of the DVD-RW in which information is recorded in the groove. The conditions are
the same as those of FIGS. 3
a-
3c.
From the graphs, it will be understood that the voltage amplitudes of the signals
SLp and SRF at the irradiation time change with the prepit length Lp and the groove
width Gw.
In accordance with the present invention, the groove width Gw, the prepit length
Lp and the groove depth Gp are determined to optimum values as follows.
The groove width Gw, prepit length Lp, groove depth Gd, numerical aperture NA
and wavelength λ are determined so that the ratio Gw/(λ/NA) of the
groove width Gw to spot diameter λ/NA is set to satisfy both of following
formulae (1) and (2). The ratio λ/NA of the wavelength λ to the numerical
aperture NA indicates a diameter d of spot SP.
##EQU5##
An optimum design of the DVD can be obtained by satisfying the above conditions.
Namely, it is possible to detect the RF signal SRE and prepit signal SLp with high
accuracy, even if the spot irradiates the groove and prepit.
The formulae (1) and (2) are verified with reference to FIGS. 5 through 13.
FIGS. 5-8 show results of experiments wherein detection accuracy of the land
prepit signal SRF changes with the groove width Gw, prepit length Lp, groove depth
Gd, wavelength λ and numerical aperture NA.
In the graph, the abscissa is the ratio Gw/(λ/NA) of diameter λ/NA
to the groove width Gw, and the ordinate is the ratio LPP level/offset of the voltage
amplitude of the land prepit signal SLp (LPP level) to the offset level (offset)
of the RF signal SRF. In addition, the groove depth Gd and the prepit length Lp
are changed.
The offset level (offset) is a parameter obtained by standardizing the alternating
current component of the RF signal SRF of FIGS. 3
a-
3c with
the direct current component of the signal SRF, and the voltage amplitude (LPP
level) is a parameter obtained by standardizing the land prepit signal SLp with
the direct current component of the RF signal SRF.
If the alternating current of the RF signal SRF is expressed by SRF (AC), the
offset level (offset) is expressed by the following formula (3), voltage amplitude
(LPP level) is expressed by the formula (4), and the ratio (LPP level/offset) is
expressed by the formula (5).
In FIGS. 5-8, the groove depth Gd is changed between 20 μm-35 μm
by
5 μm. In FIG. 5, Lp/(λ/NA)=0.128, Lp/(λ/NA)=0.2515 in FIG. 6,
0.3815 in FIG. 7, 0.505 in FIG.
8.
It is confirmed that the optimum design in the condition when the value of LPP
level/offset indicating the detecting accuracy of the land prepit detection signal
SLp and RF signal SRF is about 10, namely LPP level/offset≐10.
FIGS. 9-12 show the relationship between Lp/(λ/NA) and Gw/(λ/NA)
with the parameter of the groove depth Gd.
The line Gwo in FIGS. 9-12 is a line obtained by plotting points where the value
of LPP level/offset in FIGS. 5-8 becomes maximum, and the line G+ and line G- are
lines obtained by plotting points where LPP level/offset becomes about 10. Further,
the line G+ is the case where LPP level/offset becomes 10 in the right side of
FIGS. 5-8, the line G- is the case where LPP level/offset becomes 10 in the left
side of FIGS. 5-8.
Therefore, it is understood that the ranges Gw+ and Gw- between the lines
G+ and G- is the optimum design conditions. The line Gwo does not largely change,
it can be expressed by the following formula (6).
The formula (6) shows the most optimum condition. The lines G+ and G- is approximately
equal to lines formed by parallely moving the line Gwo.
FIG. 13 shows the relationship between the groove depth Gd and Gw+/(λ/NA)
and the relationship between the groove depth Gd and Gw-/(λ/NA) in which
the parallel moving quantities are set to the ranges Gw+ and Gw-. The range between
the lines Gw+ and Gw- is the optimum design condition. The lines Gw+ and Gw- in
FIG. 13 are expressed by following formulae (7) and (8)
Gw/(λ/
NA)=-4.48
Gd+0.2112 (7)
The above described formulae (1) and (2) are obtained by obtaining the range
between the lines Gw+ and Gw-.
In accordance with the present invention, the groove width, groove depth and
the
prepit length are set to values based on optimum conditions for preventing the
land prepit from affecting the detected RF signal. And, in accordance with the
present invention, the wavelength of laser light and the numeral aperture are set
to values based optimum conditions, also. Therefore, it is possible to detect information
recorded on the groove and the land prepit with accuracy.
While the invention has been described in conjunction with preferred specific
embodiment thereof, it will be understood that this description is intended to
illustrate and not limit the scope of the invention, which is defined by the following claims.
*
