Magnetooptical disk unit capable of recording or reproducing...

Details Magnetooptical disk unit capable of recording or reproducing... Magnetooptical disk unit capable of recording or reproducing...

2000-09-21

2001-09-25

Neyzari, Ali (Department: 2651)

Dynamic information storage or retrieval

Storage or retrieval by simultaneous application of diverse...

C369S275300

Reexamination Certificate

active

06295253

ABSTRACT:

TITLE OF THE INVENTION
Magnetooptical Disk Unit Capable of Recording or Reproducing Signals having Different Domain Lengths under the Same Conditions, Signal Recording Method and Signal Reproducing Method
BACKGROUND OF THE INVENTION
1.Field of the Invention
The present invention relates to a magnetooptical disk unit recording and reproducing signals in and from a magnetooptical recording medium, a signal recording method and a signal reproducing method.
2. Description of the Prior Art
A magnetooptical recording medium is watched with interest as a reloadable recording medium having a large storage capacity and high reliability, and now being put into practice as a computer memory or the like. Further, a magnetooptical recording medium having a storage capacity of 6.0 Gbytes is standardized under AS-MO (advanced storaged magnetooptical disk) standards, to be put into practice.
In addition, a magnetooptical recording medium having a recording capacity of 14 Gbytes is proposed according to an extensional magnetic domain reproducing system for extensionally transferring magnetic domains from a recording layer to a reproducing layer.
Referring to
FIGS. 14A
to
14
C, a signal “01011001110” is recorded in a magnetooptical recording medium according to such an extensional magnetic domain reproducing system by applying an external magnetic field to the magnetooptical recording medium thereby forming domains
500
by “0”, a domain
501
by “1”, a domain
502
by “11”, a domain
503
by “00” and a domain
504
by “111” respectively.
The signal is reproduced by irradiating the magnetooptical recording medium with a laser beam and applying an alternating magnetic field
505
of ±300 Oe thereby extensionally transferring each magnetic domain of a recording layer formed as a domain to a reproducing layer. In this case, the alternating magnetic field
505
is applied to central portions of respective domains having different domain lengths, such as the domain
501
having the minimum domain length and the domain
502
having a domain length 2T, for example.
In the conventional reproducing method, however, a leakage magnetic field
506
from the domain
501
having the minimum domain length and a leakage magnetic field
507
from the domain
502
having the domain length 2T are different from each other and hence the domains
501
and
502
are irradiated with the laser beam at different intensity levels. In order to reproduce the signal, therefore, the intensity of the laser beam must be varied with the domain lengths.
The intensity of the leakage magnetic field
506
from the domain
501
having the minimum domain length is increased from both ends toward the central portion of the domain
501
, while the intensity of the leakage magnetic field
507
from the domain
502
having the domain length 2T is increased on both ends of the domain
502
and reduced on the central portion. Thus, the domain
501
is readily extensionally transferred from the recording layer to the reproducing layer when the alternating magnetic field
505
is applied to the central portion of the domain
501
. However, it is difficult to extensionally transfer the domain
502
from the recording layer to the reproducing layer due to the small intensity of the leakage magnetic field
507
on the central portion. In order to extensionally transfer the domain
502
to the reproducing layer, therefore, the intensity of the laser beam applied to the domain
502
must be increased for increasing the intensity of the leakage magnetic field
507
on the central portion of the domain
502
. Consequently, the intensity of the applied laser beam must be increased in proportion to the domain length. Some domain may not be extensionally transferred to the reproducing layer even if the intensity of the applied laser beam is increased, depending on the domain length.
SUMMARY OF THE INVENTION
Accordingly, an object of the present invention is to provide a magnetooptical disk unit recording a signal in a magnetooptical recording medium to be capable of correctly reproducing the signal by extensionally transferring domains having different domain lengths from a recording layer to a reproducing layer under the same reproducing conditions and reproducing the recorded signal, a signal recording method and a signal reproducing method.
According to a first aspect of the present invention, a magnetooptical disk unit for recording a recorded signal having a signal of n bits consisting of 1s and a signal of m bits consisting of 0s arranged in a prescribed system in a magnetooptical recording medium includes a signal conversion circuit converting each of first to n−1-th Is forming the signal of n bits to (1,0) having a unit bit length when n is at least 2 and converting each of first to m−1-th 0s forming the signal of m bits to (0,1) having a unit bit length when m is at least 2.
The magnetooptical disk unit according to the first aspect records the signal in the magnetooptical recording medium while converting the first to n−1-th “1”s excluding the last one of the continuous “1”s to (1,0) formed by “1” and “0” shorter than the unit bit length when at least two “1”s forming the recorded signal continue and converting the first to m−1-th “0”s excluding the last one of the continuous “0”s to (0,1) formed by “0” and “1” shorter than the unit bit length when at least two “0”s forming the recorded signal continue. In other words, the signal of n bits consisting of 1s is recorded as 2×(n−1)+1=2n−1 (n≧2) domains having alternately arranged “1”s and “0”s, and the signal of m bits consisting of “0”s is recorded as 2m−1 (m≧2) domains having alternately arranged “0”s and “1”s. A signal of “1” or “0” corresponding to the minimum domain length is recorded as general.
According to the first aspect of the present invention, therefore, extensional transfer is caused from ends of domains to a reproducing layer when applying an alternating magnetic field including an in-plane component of the magnetooptical recording medium around the boundaries between the domains for reproducing a signal from the magnetooptical recording medium so that a reproduced signal having peaks corresponding to the length of the domains formed on the magnetooptical recording medium such as a reproduced signal having two peaks for domains of 2T, for example, is detected. Thus, the signal can be reproduced under constant reproducing conditions regardless of the domain length.
According to a second aspect of the present invention, a magnetooptical disk unit recording a recorded signal having a signal of n bits consisting of 1s and a signal of m bits consisting of 0s arranged in a prescribed system in a magnetooptical recording medium includes a magnetic head, a signal conversion circuit and a drive signal generation circuit. The magnetic head applies a magnetic field to the magnetooptical recording medium. The signal conversion circuit converts each of first to n−1-th 1s forming the signal of n bits to (1,0) having a unit bit length when n is at least 2, and converts each of first to m−1-th 0s forming the signal of m bits to (0,1) having a unit bit length when is at least 2. The drive signal generation circuit generates a drive signal for driving the magnetic head in response to an output signal from the signal conversion circuit.
In the magnetooptical disk unit according to the second aspect, the signal conversion circuit converts the first to n−1-th “1”s excluding the last one of the continuous “1”s to (1,0) formed by “1” and “0” shorter than the unit bit length when at least two “1”s forming the recorded signal continue, and converts the first to m−1-th “0”s excluding the last one of the continuous “0”s to (0,1) formed by “0” and “1” shorter than the unit bit length when at least two “0”s forming the recorded signal continue. The magnetic field applied from the magnetic head to the magnetooptical recording medium is modulated on the basis of the recorded signal converted by the signal conv

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