Optical disk device, control method of optical system,...

Details Optical disk device, control method of optical system,... Optical disk device, control method of optical system,...

2000-10-27

2004-03-09

Korzuch, William (Department: 2653)

Dynamic information storage or retrieval

With servo positioning of transducer assembly over track...

Optical servo system

C369S044320, C369S053190

Reexamination Certificate

active

06704254

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates, for example, to an optical disk device used for recording a signal in an optical disk or for reproducing a signal of an optical disk, a control method of an optical system, a medium, and an information aggregate.
2. Description of the Related Art
The configuration and action of a conventional optical disk device will be described on the basis of FIG.
1
(A) to FIG.
1
(C) and
FIGS. 2
,
7
. FIG.
1
(A), FIG.
1
(B), and FIG.
1
(C) are a cross-sectional configuration figure of a conventional optical head, a typical figure of optical detecting means
9
, and a partial enlarged view showing grooves and pits formed on an optical disk signal surface and the position of an optical spot, respectively. Herein, the position of a pit
14
c
in FIG.
1
(C) is on the inner peripheral side of an optical disk
8
from the positions of pits
14
a,
14
b.
In FIG.
1
(A), light
2
emitted from a radiating light source
1
such as a semiconductor laser penetrates a beam splitter
3
, and is converted into parallel light
5
by a collimate lens
4
. This light
5
is reflected on a reflecting mirror
6
and is condensed on a signal surface
8
S formed on the rear surface of an optical disk
8
by an objective lens
7
. In the objective lens
7
, the focusing and tracking, and the tilt in the radial direction are controlled by an actuator. The light reflected on the signal surface
8
S is condensed by the objective lens
7
and reflected on the reflecting mirror
6
, and passing through the collimate lens
4
, it is reflected on the beam splitter
3
, and becomes light
10
to be condensed on optical detecting means
9
.
The optical detecting means
9
is divided by a dividing line
9
L corresponding to the rotational direction (direction Y at right angles to the paper surface of FIG.
1
(A)) of the optical disk
8
, and as shown in FIG.
1
(B), this dividing line
9
L approximately equally divides an optical spot
10
S on the optical detecting means into two, and each difference signal
10
S is detected by a subtracter
10
, and a summation signal
11
S is detected by an adder
11
.
As shown in FIG.
1
(C), on the signal surface
8
S of the optical disk, uneven groves
13
G and inter-groove spaces
13
L, pit lines
14
a
and pit lines
14
b
with a fixed length are formed in cycles at a pitch p in the radial direction
12
of the optical disk
8
. On the groove
13
G and inter-groove space
13
L, signal marks
15
having a reflection factor different from that out of the own area are formed, and the difference of those reflection factors is read as a reproduction signal by an optical spot
16
scanning along the groove and inter-groove space. The positions of the pit lines
14
a,
14
b
are in synchronization with each other in the adjacent tracks, and they are also in cycles at a pitch q in the rotational direction of the optical disk. Furthermore, the center of the pit line
14
a
deviates from the center of the groove
13
G by s along the radial direction, and the pit line
14
b
deviates by s in the opposite direction thereof. Accordingly, when the optical spot
16
that has been tracking-position-controlled on the groove
13
G and the inter-groove space
13
L scans on the pit lines
14
a,
14
b,
each goes on a position deviating from the center of the pit by s.
On the other hand, on the inner peripheral side of the optical disk, pit lines
14
c
are formed in cycles at a pitch P′ in the radial direction
12
. It is possible that the positions of the pit lines
14
c
are not in synchronization with each other in the adjacent ones, and it is also possible that there is no periodicity in the rotational direction of the optical disk and the length is random. Naturally, when the tracking-position-controlled optical spot
16
scans on the pit line
14
c,
it goes on the center position of the pit.
FIG. 2
shows a signal waveform of a summation signal
11
S at the time when the optical spot
16
scans near the pit lines
14
a
and
14
b.
Herein, in
FIG. 2
, the time-axis is shown in the horizontal axis, and it expresses the fact that the signal waveform of the pit line
14
b
is detected after the signal waveform of the pit line
14
a
has been detected. When the optical spot
16
is positioned at places
101
a,
101
b
just beside the pits (refer to FIG.
1
(c)), the scattering effect by the pit is large and the detected light quantity is lowered, but when it is positioned at places
102
a,
102
b
just beside the inter-pit spaces (spaces between a pit and a next pit) (refer to FIG.
1
(C)), the detected light quantity is restored. Accordingly, by scanning beside the pit line
14
a,
the reproduction signal vibrates between an envelope
17
a
(corresponding to the reproduction signal at the position
101
a
) and an envelope
18
a
(corresponding to the reproduction signal at the position
102
a
) (letting the output differences from a level
19
of a detected light quantity of zero to the respective envelopes be A
1
, A
2
). Similarly, by the scanning of the optical spot
16
beside the pit line
14
b,
the reproduction signal also vibrates between an envelope
17
b
(corresponding to the reproduction signal at the position
101
b
) and an envelope
18
b
(corresponding to the reproduction signal at the position
102
b
) (letting the output differences from a level
19
of a detected light quantity of zero to the respective envelopes be B
1
, B
2
).
FIG. 7
shows a flow of the control signal process in the movable tilting means of a conventional optical disk device. In
FIG. 7
, a summation signal
11
S created in the adder
11
is a signal at the time when the optical spot
16
scans near the pit lines
14
a
and
14
b,
and it shows a signal waveform shown in FIG.
2
. These signals whose detecting times are different are introduced into an arithmetic circuit
20
, and the delaying process is applied, and a signal B defined by the relation of B=(A
2
−A
1
)−(B
2
−B
1
) is created, and a signal
23
in which the high frequencies are cut by a low-pass filter
22
is made.
On the other hand, a signal A of the difference created in the subtracter
10
is a signal at the time when the optical spot
16
scans on the groove
13
G or the inter-groove space
13
L. A difference signal
24
of this signal A and the signal
23
is introduced into a driving circuit
25
, and a tracking drive signal
26
is created. By this drive signal
26
, the objective lens
7
is moved in the radial direction of the optical disk
8
, and according to the control formula B=0, the tracking center control of the optical spot
16
is performed.
Furthermore, under the condition where this tracking control is applied, the signal A becomes a signal
28
in which the high frequencies are cut by a low-pass filter
27
and is introduced into a driving circuit
29
, and a lens tilt drive signal
30
is created. By this drive signal
30
, the objective lens
7
is tilted in the radial direction of the optical disk
8
(state of the objective lens
7
′ in FIG.
1
(A)), and according to the control formula A=0, the lens tilt control is performed.
By such a control, it has been intended to reduce the off-track quantity of the optical spot
16
and to cancel the aberration (especially, third order coma aberration) of the optical spot
16
created by the tilt of the optical disk
8
(state of the optical disk
8
′ in FIG.
1
(A)).
However, actually, there has been such a problem that the off-track quantity cannot be made zero by a conventional method like this, and that the third order coma aberration also cannot be cancelled. Furthermore, it has been impossible to well understand the reason.
When the off-track quantity deviates from zero, there is such a problem that the optical spot
16
eliminates part of the adjacent signal mark
15
at the time of recording and that the cross-talk increases at the time of reproduction to degrade the jitter or the like. Furthermore, when the third order

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