Method of and apparatus for recording/erasing information by utilizing light induced thermo-magnetic effect

Claim 2

1-. A method of recording and erasing information on the basis of a light induced thermo-magnetic effect caused by applying a laser beam and a magnetic field to a recording member (1) having a recording film capable of recording and erasing information by changing the direction of magnetization of the recording film, comprising the steps of: focusing said laser beam on said recording film so that a light spot is formed on said recording film; and changing the direction of magnetic field applied to said recording film at least between a recording operation and an erasing operation so that a magnetic field having a desired direction is applied to said recording film before the intensity of said laser beam is changed to a first level capable of extinguish the magnetization of said recording film.

Claim 3

A method of recording and erasing information as claimed in Claim 1, wherein a reproducing operation corresponding to at least one rotational period of said recording medium (1) is performed between a recording operation and an erasing operation, and the intensity of said laser beam is kept at a second level insufficient to extinguish the magnetization of said recording film, in said reproducing operation.

Claim 4

A method of recording and erasing information as claimed in Claim 2, wherein the application of said magnetic field to said recording film is stopped in said reproducing operation, and is started before the intensity of said laser beam is changed from said second level to said first level.

Claim 5

A method of recording and erasing information as claimed in Claim 1, wherein said recording member (1) has the form of a disk, a plurality of tracks each corresponding to the circumference of said recording member are formed on said recording member, each of said tracks is divided into a plurality of sectors (21 to 28), each sector has a header portion (31 to 38) having stored a header signal which includes a sector number (51) for identifying the sector, and a data portion following said header portion for recording magnetization information, and the magnetic field having a direction corresponding to an operation which is to be performed for a target sector, is applied to said recording film when said light spot is placed on a sector which precedes said target sector by a predetermined number of sectors.

Claim 6

A method of recording and erasing information as claimed in Claim 4, wherein a reproducing operation corresponding to at least one rotational period of said recording medium is performed between a recording operation and an erasing operation, and the intensity of said laser beam is kept at a second level insufficient to extinguish the magnetization of said recording film, in said reproducing operation.

Claim 7

A method of recording and erasing information as claimed in Claim 5, wherein the direction of magnetic field applied to. said recording film is changed on the basis of the header signal from said sector which preceds. said target sector by a predetermined number of sectors, and the intensity of said laser beam is changed on the basis of the header signal from the target sector.

Claim 8

A method of recording and erasing information as claimed in Claim 6, wherein the application of said magnetic field to said recording film is stopped in said reproducing operation, and the application of a magnetic field having a direction corresponding to an operation which is to be performed for said target sector, to said recording film is started on the basis of the header signal from-the sector which preceds said target sector by a predetermined number of sectors.

Claim 9

A light-magnetic information processing apparatus comprising: a recording member having a recording film capable of recording and erasing information in accordance with the change of a magnetized direction, said recording member.having a plurality of tracks each of which has a plurality of sectors, each sector having a header portion recorded with header signals including a sector number for discriminating at least the corresponding sector, and a data portion located sequentially to said header portion; a disk-like member capable of recording magnetizing information at said data portion; a laser light source; optical means for focusing the laser light form said laser light source on said recording film of said recording member as a light spot; coil means for applying a magnetic field on said recording film; detecting means for detecting said header signal and a magnetizing information by the laser light reflected from said recording film; coil driving means for driving said coil means by switching the direction of the application of said magnetic field between the recording time and erasing time; first means connected to said detecting means for detecting the fact that said light spot is positioned at the sector located in a previous position by predetermined numbers with respect to a target sector by using the detected header signal; and second means connected to said first means for generating the signals for controlling said coil driving means such that there is applied the magnetic field having a predetermined direction according to the operation to be effected with respect to said target sector.

Claim 10

A light-magnetic information processing apparatus comprising: a recording member having a recording film capable of recording and erasing information in accordance with the change of a magnetized direction, said recording member.having a plurality of tracks each of which has a plurality of sectors, each sector having a header portion recorded with header signals including a sector number for discriminating at least the corresponding sector, and a data portion located sequentially to said header portion; a disk-like member capable of recording magnetizing information at said data portion; a laser light source; optical means for focusing the laser light form said laser light source on said recording film of said recording member as a light spot; coil means for applying a magnetic field on said recording film; detecting means for detecting said header signal and a magnetizing information by the laser light reflected from said recording film; coil driving means for driving said coil means by switching the direction of the application of said magnetic field between the recording time and erasing time; first means connected to said detecting means for detecting the fact that said light spot is positioned at the sector located in a previous position by predetermined numbers with respect to a target sector by using the detected header signal; and second means connected to said first means for generating the signals for controlling said coil driving means such that there is applied the magnetic field having a predetermined direction according to the operation to be effected with respect to said target sector.

Claim 11

A light-magnetic information processing apparatus as claimed in claim 8, wherein said first means comprising first memory means for memorizing the sector address included in the header signal detected by said detected means, second memorizing means for memorizing the sector address with respect to the target sector, and comparing means connected to said first and second memorizing means for comparing both of memorized contents of said first and second memorizing means after a predetermined operation is effected to the memorized contents of either of said first and second memorizing means.

Claim 12

A light-magnetic information processing apparatus as claimed in claim 8, wherein said second means is composed of a first and a second circuits either of which is set in an operable condition in accordance with the recording operation or the erasing operation to be effected to said target sector, for generating said control signal by the output of said first means.

Claim 13

A light-magnetic information processing apparatus as claimed in claim 8, wherein there is provided laser light modulating means for switching an intensity of said laser light between a first level in which the magnetization of said recording film is eliminated and a second level in which the magnetization of said recording film is not eliminated, whereby the reproducing operation for at least one cycle on said disk by the spot light in said second level between the operations of recording and erasing, is effected.