Dynamic information storage or retrieval – Condition indicating – monitoring – or testing – Including radiation storage or retrieval
Reexamination Certificate
2000-04-24
2004-10-26
Edun, Muhammad (Department: 2655)
Dynamic information storage or retrieval
Condition indicating, monitoring, or testing
Including radiation storage or retrieval
C369S053350, C369S059100, C369S124010
Reexamination Certificate
active
06809999
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the benefit of Korean Application No. 99-14488, filed Apr. 22, 1999, in the Korean Patent Office, the disclosure of which is incorporated herein by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of signal reproduction in an optical disk, and more particularly, to a device and method for reducing crosstalk between neighboring tracks and intersymbol interference between adjacent marks by using multiple-divided detection signals from an optical detector.
2. Description of the Related Art
The recording and/or reproducing apparatus in an optical disk is a kind of low pass filter due to the optical transfer function (OTF) of an objective lens and the responsive characteristic of recording materials. If the recording density increases, the recording/reproducing apparatus approaches the upper limit value of the radio frequency band at which data is recorded, causing the respective waveforms to interfere with each other to generate an error when adjacent marks are reproduced. This phenomenon is called intersymbol interference (ISI). In addition, as the recording density increases, the track pitch reduces which worsens the degradation of a reproducing signal due to mutual interference between neighboring tracks. The degree of signal degradation by neighboring tracks is defined as crosstalk.
In the conventional art, a waveform equalizer is used for reducing ISI. The simplest cosine equalizer using two delay circuits is shown in FIG.
1
. Referring to
FIG. 1
, a single pulse input from an equalizer and the coefficient of attenuators
12
and
20
are denoted by x(t) and c, respectively, the delay time of delay circuits
16
and
18
is denoted by &tgr;, and the output of the equalizer is denoted by g(t). A reproducing signal for a mark recorded on an optical disk shows the characteristic of a low pass filter. The requirement for eliminating ISI is that the output at the reproducing position of another pulse should be “zero”. In other words, the requirement for ISI to equal 0 in a reproducing waveform g(t) is given below in equation (1):
g
(
nT
)
=
1
(
n
=
0
)
=
0
(
n
≠
0
)
(
1
)
Where n is an integer.
Expressed in the frequency domain, equation (1) becomes equation (2) as follows:
∑
k
=
∞
∞
G
(
j
ω
+
j2
π
T
k
)
=
G
0
(
2
)
where |&ohgr;|<&pgr;/T , k=0, ±1, ±2, . . . , G
0
is a constant, and the function G(j&ohgr;) is the Fourier transform of g(t). From equation (2), it becomes evident that ISI=0 if what divides and overlaps G(j&ohgr;) by the angular frequency width of 2&pgr;/T shows the characteristic of an ideal low pass filter.
In
FIG. 1
, if the attenuation coefficient c of the attenuators
12
and
20
and the delay time &tgr; of the delay circuits
16
and
18
are appropriately selected, it is possible to remove ISI by sharpening the waveform of an input signal. The equalizer output g(t) provided from an adder
24
is represented as follows in equation (3):
g
(
t
)=
x
(
t
−&tgr;)−
c{x
(
t
)+
x
(
t
−2&tgr;)} (3)
Graphically, equation (3) and the signals within the circuits in
FIG. 1
are shown in FIG.
2
A.
FIG. 2A
shows the reproducing positions of the output signal −cx(t) of an inverter
14
, the output signal of x(t−&tgr;) of the delay circuit
16
, and the output signal −cx(t−2&tgr;) of an inverter
22
.
FIG. 2B
shows the resulting waveform from the adder
24
, g(t), from which the ISI has been removed,.
However, a problem with the conventional waveform equalizer used to reduce ISI as shown in
FIG. 1
is that adjacent mark signals have a predetermined time delay, so that the reproducing signal of a currently recorded mark cannot be detected in real time.
SUMMARY OF THE INVENTION
As such, it is an object of the present invention to provide a device for reducing intersymbol interference (ISI) by using multiple-divided detection signals from an optical detector instead of a waveform equalizer.
It is another object to provide a device for reducing crosstalk and ISI using multiple-divided detection signals from an optical detector instead of a waveform equalizer.
It is still another object to provide a method of dividing detection signals from an optical detector to optically minimize ISI into multiple-divided signals and operating the same.
It is still further another object to provide a method of dividing detection signals from an optical detector to optically minimize crosstalk and ISI into multiple-divided signals and operating the same.
Accordingly, to achieve the above objects of the present invention, there is provided a device for reducing an ISI in the recording/reproducing apparatus of an optical disk, the device including a detector for detecting an optical signal reflected from an optical disk by dividing the optical signal into central and peripheral parts in the tangential direction of the optical disk to provide central tangential and peripheral tangential detection signals, and a correcting unit for both controlling the gain value of the peripheral tangential detection signal to produce a gain-controlled peripheral tangential detection signal, and operating the gain-controlled peripheral tangential detection signal and the cental detection signal to provide a signal in which the ISI is corrected.
Further, the present invention provides a device for reducing ISI and crosstalk in the recording/reproducing apparatus of an optical disk, including a detector for detecting an optical signal reflected from the optical disk by dividing the optical signal into the central and peripheral parts in the radial direction of the optical disk, to provide central radial and peripheral radial detection signals, and the central and peripheral parts in the radial direction that also lie in the peripheral parts in the tangential direction to provide central radial peripheral tangential and peripheral radial peripheral tangential detection signals, and a correcting unit for generating a first signal by controlling the peripheral radial detection signal using a first gain value to produce a first gain-controlled peripheral radial detector signal, and operating the first gain-controlled peripheral radial detection signal and the central radial detection signal to create the first signal, generating a gain controlled second signal by gain-controlling the peripheral radial peripheral tangential detection signal using the first gain value to provide a second gain-controlled peripheral radial peripheral tangential detection signal, operating the second gain-controlled peripheral radial peripheral tangential detection signal and the central radial peripheral tangential detection signal to provide a second signal, gain-controlling the second signal using a second gain value to provide a gain-controlled second signal, and operating the first and the gain-controlled second signals to provide a signal in which crosstalk and ISI are corrected.
There is provided a method for reducing ISI in the recording/reproducing apparatus of an optical disk includes the steps of dividing an optical signal reflected from the optical disk into central and peripheral parts in the tangential direction of an optical disk to provide central tangential and peripheral tangential detection signals, controlling the gain value of the peripheral tangential detection signals to provide a gain controlled peripheral tangential detection signal, and operating the gain-controlled peripheral tangential detection signals and the central tangential detection signal to provide a signal in which ISI is corrected. In this case, the gain value is adjusted to minimize ISI by adjacent marks.
Further, the present invention provides a method for reducing ISI in the recording/reproducing apparatus of an optical disk including the steps of dividing an optical signal reflected from the op
Ahn Young-man
Chung Chong-sam
Kim Tae-kyung
Seo Hea-jung
Edun Muhammad
Samsung Electronics Co,. Ltd.
Staas & Halsey , LLP
LandOfFree
Device and method for reducing crosstalk and intersymbol... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Device and method for reducing crosstalk and intersymbol..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Device and method for reducing crosstalk and intersymbol... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3262196