Dynamic information storage or retrieval – With servo positioning of transducer assembly over track... – Optical servo system
Reexamination Certificate
1997-12-17
2001-01-09
Hindi, Nabil (Department: 2753)
Dynamic information storage or retrieval
With servo positioning of transducer assembly over track...
Optical servo system
C369S013010, C369S112040
Reexamination Certificate
active
06172950
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to tilt correction of a magnet-optical readable medium, and more particularly, to tilt correction method for carrying out tilt correction by detecting crosstalk, magnet-optical reproducing apparatus to be used for practicing the tilt correction method, magnet-optical recording and reproducing apparatus, and magnet-optical readable medium.
As an external memory device for a computer, a magnet-optical disk has great potential. The magnet-optical disk can drastically increase recording capacity in comparison with the flexible disk or hard disk, by forming the recording bits of submicron unit on a medium by application of an external magnetic field and irradiation of a laser beam. For example, the 3.5 inch magnet-optical disk which is at present in practical use has a track of 1.1 &mgr;m pitch provided in a radial direction and recording marks of 0.64 &mgr;m in the minimum in the circumferential direction, with a recording capacity of approximately 640 MB on one side of the disk.
In order to record further enormous the data amount on such magnet-optical disks and make it possible to record motion images, it is necessary to increase further the recording capacity, i.e., recording density. Thus, it is necessary to shorten the recording mark length and shorten the distance between marks. For that purpose, the wavelength of the laser beam to be irradiated may be shortened, but there has been a problem of lowering the reading signal level. To cope with this problem, there has been proposed a magnetically induced super resolution (MSR) technique to read recording marks smaller in size than the spot diameter by utilizing the temperature distribution in the spot region of the laser beam.
Various MSR media proposed have had problematic points such that a large initializing magnet is required, or though the initializing magnet is not required, the crosstalk is high, or the reading signal level is low, and the like. In this connection, the present applicant proposed in Japanese Patent Application Laid-Open No. 7-244877(1995) an MSR medium with which a transcription region can be formed in a spot by application of low magnetic field, by providing an intermediate layer having specified magnetization characteristics between the reading layer and the recording layer. This MSR medium has resolved the defects of other MSR medium in that it does not necessitate a initialization magnet, it is effective for crosstalk, and can give high reading signal level.
By the way, in recording or reproducing information on a magnet-optical disk, the light beam is irradiated on the magnet-optical disk loaded with an apparatus and the magnetic field is applied. At this time, when the inclination of the magnet-optical disk relative to the light beam (hereinafter to be called tilt) is deviated from a perpendicular line under the loaded state, the recording signal may not be accurately recorded or accurate reading signal may not be obtained. For example, in case of reading the MSR medium proposed by the present applicant as described above, in case a tilt is formed, the temperature distribution in the laser beam spots shows change from the normal state to cause a change in the configuration of the transcription region in the spot. As a result, there has been a problem that the reading signal cannot be obtained in sufficient amplitude.
Furthermore, in the recording of the MSR medium as mentioned above, in case of the formation of tilt, the laser beam power is required to be elevated so as to focus the laser beam, thereby narrowing the recording power margin and providing no practical result.
BRIEF SUMMARY OF THE INVENTION
The present invention has been made to solve the problematic points mentioned above. An object of the present invention is to provide a tilt correction method and apparatus for carrying out tilt correction of a magnet-optical readable medium loaded with an apparatus by detecting crosstalk from the predetermined region of the magnet-optical readable medium. Another object of the present invention is to provide a magnet-optical readable medium having record of the program code means for correcting tilt, and a magnet-optical readable medium having the region for detecting the above crosstalk.
The tilt correction method of the magnet-optical readable medium of the present invention is characterized by having a step of detecting the loading of the magnet-optical readable medium on the reproducing apparatus, a step of applying a magnetic field to the magnet-optical readable medium while irradiating said light beam to read out the predetermined region of said magnet-optical readable medium, a step of detecting the crosstalk of said predetermined region, a step of obtaining the tilt value of said magnet-optical readable medium based on said crosstalk, and a step of correcting the tilt of said magnet-optical readable medium according to the obtained tilt value.
Accordingly, since the tilt value when the magnet-optical readable medium is loaded is detected and the tilt is corrected when correction is necessary, and the actions of recording, reproducing, etc. are exerted to the magnet-optical readable medium after correction, accurate recording and reproducing can be performed. The tilt value of the loaded magnet-optical readable medium can be obtained for example by reading the region for detecting the crosstalk provided on the magnet-optical readable medium and detecting the crosstalk from the reading signal.
With tilt correction method according to the present invention, the magnet-optical readable medium permits reading from the transcription region smaller than the spot diameter of said light beam, and said magnetic field has a polarity in which the transcription region becomes broader in the track width direction of said magnet-optical readable medium in reading said predetermined region.
This is a method for applying a tilt correction to the MSR medium according to the proposal of the applicant of the present application. This MSR medium shows remarkably different crosstalk values depending on the polarity of the reproducing magnetic field, as shown in the later described FIG.
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. This is due to the difference of the configuration of the transcription region. When the transcription region has such configuration as to become broader in the track width direction, the crosstalk value becomes larger. Accordingly, when reproducing for correcting the tilt of the medium, by applying a magnetic field of the polarity in which the crosstalk value becomes larger, the tilt value can be accurately obtained.
The magnet-optical reproducing apparatus according to the present invention comprises a loading part to which the magnet-optical readable medium is loaded, a detecting part for detecting the loading of said magnet-optical readable medium to said loading part, an optical head for receiving the reflected light of a light beam irradiated on the magnet-optical readable medium and converting it to an electric signal, a tilt correction operating circuit for generating a crosstalk detecting signal from the electric signal of said optical head in response to the detection of said detecting part, a crosstalk detecting circuit for detecting the crosstalk from said crosstalk detecting signal, a tilt value calculating circuit for obtaining the tilt value of the magnet-optical readable medium based on the detected crosstalk, and a tilt correction part for correcting the tilt of the magnet-optical readable medium based on said tilt value.
Accordingly, the tilt value when the magnet-optical readable medium is loaded on the loading part is calculated by the tilt value calculating circuit, and when correction is necessary, the tilt is corrected by said tilt correcting part. Since the operations of recording, reproducing, etc. are given to the magnet-optical readable medium after correction of the tilt, correct recording and reproducing can be performed. The tilt value of the amounted magnet-optical readable medium is obtained by reproducing, for example, the region for de
Fujitsu Limited
Greer Burns & Crain Ltd.
Hindi Nabil
LandOfFree
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