Optical disk device using a recording medium structurally arrang

Details Optical disk device using a recording medium structurally arrang Optical disk device using a recording medium structurally arrang

1998-02-04

2000-09-26

Dinh, Tan

Dynamic information storage or retrieval

Storage or retrieval by simultaneous application of diverse...

Magnetic field and light beam

369116, 369 54, G11B 1100

Patent

active

061250848

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an information recording/reproducing apparatus for recording or reproducing information on or from an optical recording medium, and more particularly to a method and an apparatus for realizing high density recording/reproducing by applying a magnetic field modulation magnetooptical recording method to an optical disk.


BACKGROUND ART

A magnetic field modulation magnetooptical recording/reproducing method has been known conventionally as a technique of making an optical disk highly dense.
As one example of conventional techniques, a consecutive light pulse irradiation and magnetic field modulation method described in JP-A-1-292603 and applied to an optical disk drive will be described. With this disk drive, clock signals are obtained from a preformatted clock pit train on an optical disk of a sample-servo format.
As shown in FIG. 8, while high output light pulses 802 synchronizing with clock signals 801 are irradiated, modulation magnetic fields 808 corresponding to data 803 are applied synchronously with the light pulses 802 to form magnetic domains 804. During the reproduction, the data 803 is detected by using the same clock signals 801. The characteristic feature of this method resides in that the edge distance 807 of the magnetic domain 805 recorded with too large a power is the same as the edge distance 807 of the magnetic domain 804 recorded with too small a power, irrespective of their different recording powers. It is therefore possible to record/reproduce always at a constant edge distance 807 and is suitable for high bit density recording/reproducing.
A second conventional example as a means for solving a recording medium sensitivity fluctuation problem associated with light modulation edge recording will be described with reference to JP-A-4-61028. According to the second conventional example, a recording medium is provided with a trial writing area at a predetermined position and a trial writing pattern is actually recorded in this trial writing area. By evaluating a signal reproduced from this trial area, optimization of a recording power level is performed.
FIG. 7 shows an example of the structure necessary for evaluating a reproduction signal for the optimization of recording conditions according to the second conventional example.
As shown in FIG. 7 at (a), a combination of two shortest/longest recording mark/gap repetition patterns determined from a recording modulation method is used as a trial writing pattern. If a (1,7) modulation method is used as a coding method, the lengths of shortest/longest recording mark/gap are 2 Tw and 8 Tw respectively (Tw is a channel bit length, i.e., a shortest change length of a recording mark, i.e., a detection window width). If the bit length of the recording code train is 0.53 microns, the longest mark/gap length is 3.0 microns. If the laser wavelength is 780 nm and the lens NA is 0.55, the amplitude of a signal reproduced from the repetition pattern (hereinafter called "coarsest pattern") of the longest recording mark/gap (each 8 Tw long) is generally determined only by the width of the recording mark, and the positions of leading and trailing edges of a signal correspond to the edge positions. On the other hand, the amplitude of a signal reproduced from the repetition pattern (hereinafter called "densest pattern") of the shortest recording mark/gap (each 2 Tw long) is smaller than the coarsest pattern because the recording mark/gap length is generally equal to a half the diameter of the reproduction light spot. The center level of the reproduction signal amplitude shifts toward the recording mark because of optical interference of the preceding and succeeding recording marks. This shift amount is influenced by both the length and width of the recording mark. The longer and wider the recording mark, the larger the shift amount. From the above consideration, the recording control has been performed so that the width of the recording mark becomes generally constant irrespective of the recording mark len

REFERENCES:
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patent: 5485433 (1996-01-01), Satomura et al.
patent: 5590111 (1996-12-01), Kirino et al.
patent: 5642343 (1997-06-01), Toda et al.
patent: 5732061 (1998-03-01), Kirino et al.
patent: 5737301 (1998-04-01), Miyamoto et al.

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