Dynamic information storage or retrieval – Specific detail of information handling portion of system – Radiation beam modification of or by storage medium
Reexamination Certificate
1999-08-20
2002-06-18
Edun, Muhammad (Department: 2653)
Dynamic information storage or retrieval
Specific detail of information handling portion of system
Radiation beam modification of or by storage medium
C369S059100, C369S047100
Reexamination Certificate
active
06407977
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for controlling equalization characteristics of signals reproduced from an optical disk medium.
2. Description of the Related Art
Methods for recording and/or reproducing information on or from an optical disk are in general classified into constant linear velocity (hereinafter, referred to as CLV) schemes and constant angular velocity (hereinafter, referred to as CAV) schemes. If an optical disk having data recorded by the CLV method is played by the same method, the gain of an equalizer for correcting distortions in signals reproduced by a pickup is fixed all the time because the linear velocity of data pits remains constant over all tracks. In contrast, provided that the disk is played by the CAV method, the linear velocity of data pits increases in the radial direction from inner peripheries to outer peripheries, which implies that the frequency characteristics of reproduced signals vary with tracks.
Shown in
FIG. 1A
is a conventional apparatus for reproducing, at a constant angular velocity, an optical disk
10
with data recorded by the CLV scheme. The apparatus includes a pickup
11
for retrieving information recorded on the optical disk
10
using a laser beam, a sled motor
12
a
for moving the pickup
11
in the radial direction, a spindle motor
12
b
for rotating the optical disk
10
, a drive unit
30
for driving the sled motor
12
a
and the spindle motor
12
b
, a radio frequency (RF) unit
20
for equalizing and shaping signals reproduced from the optical disk
10
by the pickup
11
, a servo unit
40
for controlling the drive unit
30
by utilizing focus and tracking error signals obtained from the pickup
11
and for detecting sync signals from the output of the RF unit
20
, a digital signal processing unit
50
for retrieving recorded digital data from the output of the RF unit
20
, and a microcomputer
60
for supervising the overall operation of the apparatus.
As shown in
FIG. 1B
, the RF unit
20
further includes an RF summing circuit
21
for summing RF signals created by sub-beams in the pickup
11
, an RF equalizer
22
for equalizing signals from the RF summing circuit
21
so that signals created by data pits of various lengths (
3
T-
11
T) have the same magnitude, a comparator
23
for generating binary pulse signals by comparing the equalized signals and a slice level, and an integrator
24
for generating the slice level by integrating the binary signals to obtain their average level.
In the above apparatus, given a user's request to play the optical disk
10
, the microcomputer
60
rotationally drives the optical disk
10
at a constant angular velocity, allowing the pickup
11
to retrieve RF signals from the optical disk
10
. Signals yielded by two sub-beams in the pickup
11
are added in the RF summing circuit
21
and applied to the equalizer
22
, wherein the signals are equalized. The equalizer coefficients which determine the equalizer characteristics are set by the microcomputor
60
.
When the optical disk
10
is first accessed, information on the disk is collected and stored in an internal memory (not shown) within microcomputer
60
. Referring to the information, the microcomputer
60
determines the radius r, (the distance between the currently accessed track and the center of the disk
10
), and examines which region the radius r belongs to from among several regions
1
-
2
,
2
-
3
,
3
-
4
, . . . as shown in FIG.
2
. Each region has an associated equalizer gain curve so that a set of equalizer coefficients can be chosen according to the region to which the radius r belongs. For example, if the detected radius r is 2.1, then the equalizer gain curve corresponding to the radius r is B, which indicates that the equalizer gain for
11
T signals retrieved from the disk is a.
The microcomputer
60
transmits the chosen set of equalizer coefficients to the RF unit
20
so that the RF equalizer
22
has gain characteristics as shown in the gain curve B. Setting the transmitted coefficients, the RF equalizer
22
equalizes input RF signals with the gain characteristics. The RF equalizer
22
thus controls the gains of frequency sub-bands of reproduced signals, the entire frequency band of the reproduced signal consisting of these sub-bands. The comparator
23
compares the equalized RF signals with a slice level and yields binary signals according to the comparison result. The integrator
24
integrates the binary signals to obtain the average or DC level of the binary signals, wherein the obtained average level is fed back to the comparator
23
as the slice level. The binary signals are processed by the digital signal processing unit
50
and original digital data are finally retrieved.
In the method for adjusting equalization characteristics according to the radius r, the equalizer gain for signals yielded by data pits of the same length on tracks of similar radii may vary depending upon which gain curve is employed. For example, if the radius r is 1.9, the equalizer gain curve A is chosen and the equalizer gain for
11
T signals is b (as shown in FIG.
2
). Compared to the previous example wherein the equalizer gain for the same signals is a, there is a fairly big difference in the equalizer gain despite the fact that the two radii are similar. The discontinuity in the equalizer gains remarkably increases around the boundary of two regions partitioned by the radius r.
In addition, the relation between the radius and appropriate equalizer gain characteristics varies with disk types and disk makers. Considering this fact, therefore, the RF equalizer intended for improving signal qualities might distort reproduced signals if the RF equalizer coefficients are adjusted inappropriately.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method and apparatus for adjusting equalization characteristics of signals reproduced from an optical disk that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
The present invention is also directed to a method and an apparatus for adjusting equalization characteristics of signals reproduced from an optical disk with varying linear velocities of tracks.
In accordance with the purpose of the invention, as embodied and broadly described, one aspect of the invention includes a method for adjusting equalization characteristics of signals reproduced from an optical disk medium, including detecting a linear velocity of a track on a rotating optical disk medium, and controlling equalization characteristics of signals reproduced from the track based on the detected linear velocity.
In another aspect, the invention includes an apparatus for adjusting equalization characteristics of signals reproduced from an optical disk medium, including a detector to detect a predetermined signal derived from a track of the optical disk medium and to output detection signals when the predetermined signal is detected, a device to generate an output signal representing a linear velocity of the track based on the detection signals, and a controller to control equalization characteristics for reproduced signals based on the output signal.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate several embodiments of the invention and together with the description serve to explain the principles of the invention.
REFERENCES:
patent: 5323373 (1994-06-01), Horimai
Birch & Stewart Kolasch & Birch, LLP
Edun Muhammad
LG Electronics Inc.
LandOfFree
Method for controlling equalizer characteristics of... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method for controlling equalizer characteristics of..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method for controlling equalizer characteristics of... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2977908