Dynamic information storage or retrieval – Information location or remote operator actuated control – Selective addressing of storage medium
Reexamination Certificate
2000-05-09
2002-08-06
Dinh, Tan (Department: 2653)
Dynamic information storage or retrieval
Information location or remote operator actuated control
Selective addressing of storage medium
C369S030120
Reexamination Certificate
active
06430119
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an optical disk apparatus for optically recording a signal on an information carrier using a light source such as, for example, laser and reproducing the recorded signal; and specifically to an optical disk apparatus including a focus controller for controlling a light beam directed onto the information carrier to constantly be in a prescribed convergence state.
2. Description of the Related Art
In this specification, the term “reproduction quality signal” is defined as a signal representing the quality of a reproduction signal. The reproduction quality signal includes a jitter and a reproduction signal amplitude. The term reproduction signal amplitudes is defined as an amplitude of the reproduction signal. The term “reproduction signal amplitude measurement signal” is defined as a signal representing the reproduction signal amplitude and is measured by a reproduction signal amplitude measuring section.
The characteristics expressed by the terms “flat bottomed curve” and “flat topped curve” are also expressed as “flat”.
The term “optimum target position” is defined as a target position of a jitter characteristic at which the jitter is substantially minimum and a target position of a reproduction signal amplitude characteristic where the reproduction signal amplitude is substantially maximum.
One type of conventional optical disk apparatus, as described in, for example, Japanese Laid-Open Publication No. 2-135024, approximates a reproduction signal amplitude of a reproduction signal, changing relative to the target position of a focus control system, to a function for adjusting the target position so as to substantially maximize the reproduction signal amplitude.
FIG. 18A
is a block diagram illustrating a structure of a conventional optical disk apparatus
1800
.
The optical disk apparatus
1800
includes an optical system
131
for directing light to form a beam spot (or beam)
111
on a disk
101
, a disk motor
102
for rotating the disk
101
at a prescribed rotation rate, a light detector
109
, preamplifiers
120
A through
120
D, a matrix calculator
121
, a focus controller
132
, a reproduction signal processing section
130
, a DSP
1801
, and a moving device
133
. The optical system
131
includes a light source
103
, a coupling lens
104
, a polarization beam splitter
105
, a polarization hologram device
106
, a converging lens
107
, and a collecting lens
108
. The focus controller
132
includes a focus balance circuit
122
and a low pass filter (LPF)
123
. The DSP
1801
includes a reproduction signal amplitude measuring section
1802
, a target position searching section
1803
, and a filter calculating circuit
134
. The moving device
133
includes a focus actuator
127
and a focus driving circuit
126
. The light detector
109
includes four light detecting sections
109
A through
109
D.
A light beam
110
emitted by the light source
104
is collimated by the coupling lens
104
, and the collimated light is then reflected by the polarization beam splitter
105
, passes through the polarization hologram device
106
, and is converged by the converging lens
107
to form the beam spot
111
on an information track of the disk
101
. The beam spot
111
reflected by the disk
101
passes through the converging lens
107
, the polarization hologram device
106
, and the polarization beam splitter
105
, and is input to the light detector
109
through the collecting lens
108
.
Outputs A through D from the four light detecting sections
109
A through
109
D are respectively input to preamplifiers
120
A through
120
D and processed with current-voltage conversion, and then are input to the matrix calculator
121
. The matrix calculator
121
outputs a reproduction signal RF by adding all the outputs A through D ((A+D)+(B+C)), outputs a convergence state signal FS by (A+D)−(B+C), and outputs a phase difference tracking error signal (not shown) by comparing the phases of the signals (A+D) and (B+C). The reproduction processing circuit
130
detects an envelope of the reproduction signal RF and generates a reproduction signal amplitude measurement signal RFENV.
The focus control will be described. The focus balance circuit
122
subtracts a target position signal FBAL from the convergence state signal FS or adjusts a gain balance and thus inputs a focusing error signal FE to the filter calculation circuit
134
in the DSP
1801
through the LPF
123
. The low pass filter
123
generates a focusing error signal FE by an astigmatic method based on the differential signal DS. The filter calculating circuit
134
executes filter calculations such as A/D conversion, addition, multiplication, and shift processing to the focusing error signal FE, and outputs a focus driving signal FOD. The focus driving circuit
126
current-amplifies the focus driving signal FOD. The focus actuator
127
drives the converging lens
107
so as to move the beam spot
111
in a direction perpendicular to the surface of the disk
101
based on the current-amplified focus driving signal FOD. Thus, the light beam on the disk
101
is controlled to be in a prescribed convergence state.
Measurement of the reproduction signal amplitude will be described. The reproduction signal processing section
130
generates a reproduction signal amplitude measurement signal RFENV based on the reproduction signal RF. The reproduction signal amplitude measuring section
1802
measures the level of the reproduction signal amplitude measurement signal RFENV by receiving the reproduction signal amplitude measurement signal RFENV by a built-in A/D converter (not shown) and performing digital sampling.
A method for adjusting the target position by the DSP
1801
shown in
FIG. 18A
will be described in detail with reference to
FIGS. 18A and 18B
.
FIG. 18B
shows a third-order function curve
1901
which approximates the relationship between the reproduction signal amplitude and the target positions, the relationship being obtained when the target position for focus control is moved step by step at a prescribed interval. Axis X represents the target position, and axle Y represents the reproduction signal amplitude. The reproduction signal amplitude measuring section
1802
moves through points A, B, C, D and E, which are provided at a prescribed interval, and measures the level of the reproduction signal amplitude measurement signal RFENV at each of the target positions. In order to enhance the precision of approximation, the reproduction signal amplitude measuring section
1802
measures the level of the reproduction signal amplitude measurement signal RFENV at the target positions interposing maximum point M on the reproduction signal amplitude characteristic.
Next, the relationship between the target position x and the reproduction signal amplitude y is approximated by function y=f(x). The reproduction signal amplitude characteristic is asymmetrical with respect to maximum point M as shown in FIG.
18
B. In order to guarantee a sufficient approximation precision to the asymmetrical characteristic, approximation needs to be done with a third- or higher order function. By contrast, an excessively high order function complicates the calculation for approximation. Accordingly, the third-order function
f
(
x
)=
ax
3
+bx
2
+cx+d
(1)
is optimum for approximating the reproduction signal amplitude characteristic.
There are various methods of approximation. For example, a least square method is usable. From equation (1),
ax
3
+bx
2
+cx+d−y
=0 (2)
is obtained. When target position xj and reproduction signal amplitude yj are actually substituted into equation (2), the value of 0 is not obtained by the influence of noise, a measuring error, or the like, and the following value is obtained.
a
(
xj
)
3
+b
(
xj
)
2
+cxj+d−yj=vj
(2)′
When the values of a, b, c and d
Nishioka Akihiko
Okada Yuu
Okamoto Koujiro
Shihara Tetsuya
Watanabe Katsuya
Matsushita Electric - Industrial Co., Ltd.
Renner Otto Boisselle & Sklar
LandOfFree
Optical disk drive apparatus capable of searching an optimum... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Optical disk drive apparatus capable of searching an optimum..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Optical disk drive apparatus capable of searching an optimum... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2920812