Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
2000-04-06
2003-11-11
Dorvil, Richemond (Department: 2697)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S030130, C369S044280, C369S044340, C369S044410
Reexamination Certificate
active
06646961
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an optical recording medium driving apparatus adopting a land/groove recording system which makes high-density recording possible by changing height of adjacent tracks.
DESCRIPTION OF RELATED ART
In recent years, as the performance of computers becomes higher, the demand of large-capacity memory becomes higher. Therefore, optical disks and magneto-optical disks have been produced. However, higher capacity is demanded for the future multimedia eras.
For example, DVD-ROM (Digital Video Disc-ROM) has been put to practical use, and thus a rewritable recording medium whose capacity corresponds to that of such a DVD-ROM is required. One of the techniques to achieve storage capacity corresponding to that of the DVD-ROM is an optical disk using a land/groove recording system.
A rewritable optical disk conventionally adopted a land recording system or groove recording system. However, such recording systems are now being shifted to the land/groove recording system which can achieve higher-density recording.
In the land recording system whose storage capacity is up to 640 MB, a track count at the time of seek was carried out by a cross tracking signal which is generated when crossing a track. However, in the land/groove recording system, since the cross tracking signal is 0, this signal cannot be used.
Therefore, in the land/groove recording system, it is considered that the track count is carried out by a tracking error signal (TES). Moreover, in the land/groove recording system, since an ID prepit of a recording pattern becomes shallow, it is necessary to enlarge a pit so that sufficient signal strength can be obtained. However, when the pit is enlarged, the tracking error signal in the ID section becomes weak, and thus track miscount occurs.
FIG. 1
is a block diagram showing a constitutional example of a conventional optical recording medium driving apparatus for recording and/or reproducing data using an optical disk adopting the land/groove recording system. This optical recording medium driving apparatus is schematically shown mainly a tracking error signal detecting part. After a light outputted from a laser
111
is shaped to a parallel circular beam by using a beam shaping device, the light passes through a beam splitter
112
and its optical path is bent by a rising mirror
113
. Thereafter, the light is condensed by an objective lens
114
so as to be emitted onto a surface of a disk
110
.
The light diffracted by a groove on the surface of the disk
110
passes through the objective lens
114
again. Then the light is reflected by the beam splitter
112
so that its optical path is bent, and the light enters a two-piece detector
115
.
FIG. 2
is a drawing showing the diffracted light which enters the two-piece detector, and it shows a state of the two-piece detector in
FIG. 1
viewed from an upper surface (detecting surface). As for the two-piece detector
115
, its two-piece detecting portions are provided in the right-and-left direction of FIG.
1
. Two lights (first-order diffracted lights D
1
), which are diffracted by both edges of the groove, are diffracted in the right-and-left direction at a predetermined angle so that portions of the first-order diffracted lights D
1
enter the detecting portions on the right and left sides. Moreover, a zero-order diffracted light D
0
enters the central portion of the two-piece detector
115
with it going over both of the detecting portions. Distribution of the light intensity occurs in an area where the zero-order and first-order diffracted lights D
0
and D
1
are overlapped (cross hatching section in
FIG. 2
) due to an interference effect caused by track shifting. The respective detecting portions detect the light intensity utilizing this distribution. The two-piece detector
115
converts the lights, which are inputted after divided into two, into current signals, and inputs them into current/voltage converting circuits
116
and
117
.
The current/voltage converting circuits
116
and
117
respectively convert the inputted current signals into voltage signals so as to output them.
The voltage signals outputted respectively from the current/voltage converting circuits
116
and
117
are amplified by amplifiers
118
and
119
, and a difference signal is generated in a differential amplifier
122
. The difference signal is outputted as a tracking error signal. The objective lens
114
is automatically tracked based on the tracking error signal and the seek is again carried out.
FIG. 3
is a drawing showing an example of the ID section of the optical disk adopting the land/groove recording system suggested by the applicant of the present invention, and
FIG. 3
shows a plan view (see Japanese Patent Application Laid-Open No. 10-79125 (1998)). Here, the hatching section is a portion which is formed into a concave shape.
On this optical disk, information can be recorded in tracks formed by land portions
102
and groove portions
101
provided between the land portions
102
. Rows of prepits
104
and
103
, which correspond to pre-format information of the adjacent land portion
102
and groove portion
101
, are formed with them being shifted in the circumferential direction.
Count grooves
106
for counting tracks are formed on both sides of the rows of the prepits
104
for the land portions
102
, and through grooves
105
, which go through the rows of the prepits
103
for the groove portions
101
, are formed.
FIG. 4
is a waveform chart showing TES (tracking error signal) obtained by the conventional optical recording medium driving apparatus. In the case where a tracking error signal
201
at the time of seek is created from such an optical disk by the optical recording medium driving apparatus shown in
FIG. 1
, as shown in
FIG. 3
, the strength of a TES
202
of the ID section (a dotted line shows a strength of the tracking error signal
201
obtained not in the ID section but in the recording domain) is weakened due to the prepit
104
compared with the tracking error signal in the recording domain, and it crosses the zero line. Therefore, there arises a problem that track miscounts occurs.
The present invention has been achieved in order to solve the above problem, and it is an object of the present invention to provide an optical recording medium driving apparatus which can obtain a tracking error signal necessary for an accurate track count.
SUMMARY OF THE INVENTION
An optical recording medium driving apparatus according to the present invention for recording and/or reproducing data in/from an optical recording medium, where information can be recorded in plural tracks, based on a light emitted to the tracks of the optical recording medium, is constituted so as to have a detector for detecting a position of the emitted light, a peak-hold circuit for holding a peak of a position detected signal outputted from the detector so as to output the position detected signal, a bottom-hold circuit for outputting a bottom of the position detected signal so as to output the position detected signal, and a switching circuit for switching signals based on the output signals from the peak-hold circuit and bottom-hold circuit so as to output either signal. The optical recording medium driving apparatus is constituted so that the signal outputted from the switching circuit is used as a tracking error signal.
In this optical recording medium driving apparatus, the peak-hold circuit holds a peak of the signal outputted from the position detector so as to output the signal, and the bottom-hold circuit holds a bottom of the signal outputted from the position detector so as to output the signal. The switching circuit switches signals based on the output signals from the peak-hold circuit and bottom-hold circuit so as to output either signal, and the signal is used as a tracking error signal. As a result, a tracking error signal necessary for the accurate track count can be obtained.
Another optical recording medium driving apparatus according the present invention is constit
Iida Koichi
Kuroda Sumio
Dorvil Richemond
Fujitsu Limited
Greer Burns & Crain Ltd.
Ortiz-Criado Jorge L.
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