Dynamic information storage or retrieval – Storage medium structure – Optical track structure
Reexamination Certificate
2000-05-12
2002-08-20
Psitos, Aristotelis M. (Department: 2653)
Dynamic information storage or retrieval
Storage medium structure
Optical track structure
C369S044410, C369S275400
Reexamination Certificate
active
06438096
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a recordable/reproducible optical disk, in which information pit arrays of sector addresses are disposed so as to wobble between a land track and a groove track; and an optical disk recording/reproduction apparatus for performing recording and/or reproduction for the optical disk.
BACKGROUND ART
Optical disks have excellent removability/portability and random access performance. Therefore, it has become more and more prevalent to employ optical disks as memories in various information equipment fields, e.g., personal computers. As a result, there has been an increasing demand for increasing the recording capacitance of optical disks.
In general, guide grooves for tracking control purposes are formed on rewritable optical disks, so that data is recorded and reproduced by utilizing the guide grooves as tracks. In addition, a track is divided into a plurality of sectors for sector-by-sector management of data. Therefore, in the production of such disks, address information for each sector is often formed in the form of pits while forming the guide grooves.
In currently prevalent rewritable optical disks, tracks for recording data are either the grooves formed during the disk formation (grooves) or the interspaces between grooves (lands). On the other hand, optical disks of a land-groove recording type for recording data on both the grooves and the lands have also been proposed.
FIG. 22
illustrates an exemplary optical disk of the land-groove recording type. As used herein, the portions which are located closer to the optical disk surface are referred to as “grooves”, whereas the portions which are located further away from the optical disk surface are referred to as “lands”, as shown in FIG.
22
. It should be noted that “lands” and “grooves” are mere names; therefore, the portions which are located closer to the optical disk surface may be referred to as “lands”, while the portions which are located further away from the optical disk surface may be referred to as “grooves”.
An optical disk of the land-groove recording type requires sector addresses for both the lands and the grooves. In order to facilitate the process of forming address pits on an optical disk, an intermediate address method has been studied in which address pits are formed between a land and a groove adjoining each other so that the same address is shared by the adjoining tracks (Japanese Laid-Open Publication No. 6-176404).
Hereinafter, the intermediate address, a tracking control method for reading information from an optical disk, and a method for reading signals from an intermediate address will be described with reference to the figures.
FIG. 23
is a schematic diagram showing an optical disk having a sector structure. In
FIG. 23
, reference numeral
200
denotes a disk; reference numeral
201
denotes a track; reference numeral
202
denotes a sector; reference numeral
203
denotes a sector address region; and reference numeral
204
denotes a data region.
FIG. 24
is a magnified view of a sector address region schematically showing a conventional intermediate address. In
FIG. 24
, reference numeral
206
denotes address pits; reference numeral
207
denotes recording marks;
208
denotes a groove track; reference numeral
209
denotes a land track; and reference numeral
210
denotes a light spot.
In the optical disk shown in
FIG. 24
, the groove
208
and the land
209
are employed as tracks. Data signals can be recorded by forming the recording marks
207
on the groove
208
and the land
209
. The groove track
208
and the land track
209
have the same track pitch Tp. The center of each address pit
206
is shifted by Tp/2 from the center of the groove track
208
along the radius direction. In other words, each address pit
206
is centered around the boundary between the groove
208
and the land
209
. Although the lengths or intervals of the address pits
206
are modulated by an address signal,
FIG. 24
only schematically illustrates the shapes of the address pits
206
.
FIG. 25
is a block diagram showing the conventional tracking control and the signal processing for reading signals on an optical disk.
The structure shown in
FIG. 25
will be described below, In
FIG. 25
, reference numeral
200
denotes a disk; reference numeral
201
denotes a track; reference numeral
210
denotes a light spot; and reference numeral
211
denotes a disk motor for rotating the disk
200
. An optical head
212
optically reproduces a signal on the disk
200
. The optical head
212
includes a semiconductor laser
213
, a collimation lens
214
, an object lens
215
, a half mirror
216
, photosensitive sections
217
a
and
217
b
, and an actuator
218
. A tracking error signal detection section
220
detects a tracking error signal indicating the amount of dislocation between the light spot
210
and the track
201
along the radius direction. The tracking error signal detection section
220
includes a differential circuit
221
and a LPF (low pass filter)
222
. A phase compensation section
223
generates a drive signal from a tracking error signal for driving the optical head. A head driving section
224
drives the actuator
218
in the optical head
212
in accordance with the drive signal.
An address reproduction section
234
includes an addition circuit
225
, a waveform equalization section
226
, a data slice section
227
, a PLL (phase locked loop)
228
, an AM detection section
229
, a demodulator
230
, a switcher
231
, and an error detection section
232
. The addition circuit
225
adds signals from the photosensitive sections
217
a
and
217
b
. The waveform equalization section
226
prevents the inter-sign interference of a reproduced signal. The data slice section
227
digitizes the reproduced signal at a predetermined slice level. The PLL (Phase Locked Loop)
228
generates a clock which is in synchronization with the digitized signal. The AM detection section
229
detects AMs (address marks). The demodulator
230
demodulates the reproduced signal. The switcher
231
separates the demodulated signal into data and an address. The error detection section
232
performs an error determination in the address signal. An error correction section
233
corrects errors in the data signal.
Hereinafter, an operation for tracking control will be described. Laser light radiated from the semiconductor laser
213
is collimated by the collimate lens
214
and converged on the disk
200
via the object lens
215
. The laser light reflected from the disk
200
returns to the photosensitive sections
217
a
and
217
b
via the half mirror
216
, whereby the distribution of light amount is detected as an electric signal, which is determined by the relative positions of the light spot
210
and the track
201
on the disk. In the case of using the two-divided photosensitive sections
217
a
and
217
b
, a tracking error signal is detected by detecting a difference between the photosensitive sections
217
a
and
217
b
by means of the differential circuit
221
and extracting a low frequency component of the differential signal by means of the LPF
222
. In order to ensure that the light spot
210
follows the track
201
, a drive signal is generated in the phase compensation section
223
such that the tracking error signal becomes 0 (i.e., the photosensitive sections
217
a
and
217
b
have the same distribution of light amount), and the actuator
218
is moved by the head driving section
224
in accordance with the drive signal, thereby controlling the position of the object lens
215
.
On the other hand, when the light spot
210
follows the track
201
, the amount of reflected light is reduced at the recording marks
207
and at the address pits
206
on the track owing to interference of light, thereby lowering the outputs of the photosensitive sections
217
a
and
217
b
, whereas the amount of reflected light increases where pits do not exist, thereby increasing the outputs of the photosensitive sections
217
a
and
217
b
. The tot
Aoki Yoshito
Furumiya Shigeru
Gushima Toyoji
Ishida Takashi
Kamioka Yuichi
Matsushita Electric - Industrial Co., Ltd.
Psitos Aristotelis M.
Renner Otto Boisselle & Sklar
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