Optical memory with readout beam anneal

Claim 2

In an optical memory of the Curie point writing type wherein information is stored on a magnetic film having a plurality of temperature dependent crystallographic phases, a method of recording and reading out information while minimizing readout signal variation due to phase transformation, the method comprising: heating selected regions of the magnetic film to a temperature above the Curie temperature of a desired crystallographic phase so that upon cooling below the Curie temperature the region has a magnetizAtion direction determined by a net magnetic field present at the location of the selected region; and magneto-optically detecting the magnetization direction of a region by directing a light beam on the region, the light beam having an intensity sufficient to temporarily heat the region to a temperature at which at least a portion of the crystallographic phases other than the desired crystallographic phase in the region is removed, but insufficient to heat the region to a temperature above the Curie temperature of the desired crystallographic phase.

Claim 3

The method of claim 1 wherein the magnetic film is manganese bismuth.

Claim 4

The method of claim 2 wherein the light beam has an intensity sufficient to temporarily heat a region to a temperature above about 180*C but less than about 360*C.

Claim 5

An optical memory of the Curie point writing type wherein formation is stored on a magnetic film having a plurality of temperature dependent crystallographic phases and being characterized by greatly reduced readout signal variation due to crystallographic phase changes, the optical memory comprising: motor means for providing motion of the magnetic film in a first direction; first light source means for producing a write light beam having an intensity sufficient to heat a region of the magnetic medium to a temperature above the Curie temperature of a desired crystallographic phase; second light source means for producing a read light beam angularly separated from the write light beam in the first direction and having an intensity sufficient to temporarily heat a region of the magnetic film to a temperature at which at least a portion of the crystallographic phases other than the desired crystallographic phase in the region is removed, but insufficient to heat the region to a temperature above the Curie temperature of the desired crystallographic phase, the write and read light beams having a common pivot plane located between the first and second light source means and the magnetic medium; light beam positioning means positioned at the common pivot plane for positioning the write and read light beams in a second direction essentially orthogonal to the first direction; focusing means for focusing the write and read light beams to a write and a read focused light spot respectively on the magnetic film, the read focused light spot being spatially separated in the first direction from the write focused light spot; modulator means for selectively transmitting the write light beam with an intensity sufficient to heat a region of the magnetic film to a temperature above the Curie temperature, and then attenuating the write light beam to an intensity insufficient to heat the region to a temperature above the Curie temperature, such that the region cools to a temperature below the Curie temperature and has a magnetization direction determined by a net magnetic field present at the location of the region; and detector means for receiving the read light beam from the region and for producing a magneto-optic signal indicative of the magnetization direction of the region.

Claim 6

An optical memory of the Curie point writing type wherein formation is stored on a magnetic film having a plurality of temperature dependent crystallographic phases and being characterized by greatly reduced readout signal variation due to crystallographic phase changes, the optical memory comprising: motor means for providing motion of the magnetic film in a first direction; first light source means for producing a write light beam having an intensity sufficient to heat a region of the magnetic medium to a temperature above the Curie temperature of a desired crystallographic phase; second light source means for producing a read light beam angularly separated from the write light beam in the first direction and having an intensity sufficient to temporarily heat a region of the magnetic film to a temperature at which at least a portion of the crystallographic phases other than the desired crystallographic phase in the region is removed, but insufficient to heat the region to a temperature above the Curie temperature of the desired crystallographic phase, the write and read light beams having a common pivot plane located between the first and second light source means and the magnetic medium; light beam positioning means positioned at the common pivot plane for positioning the write and read light beams in a second direction essentially orthogonal to the first direction; focusing means for focusing the write and read light beams to a write and a read focused light spot respectively on the magnetic film, the read focused light spot being spatially separated in the first direction from the write focused light spot; modulator means for selectively transmitting the write light beam with an intensity sufficient to heat a region of the magnetic film to a temperature above the Curie temperature, and then attenuating the write light beam to an intensity insufficient to heat the region to a temperature above the Curie temperature, such that the region cools to a temperature below the Curie temperature and has a magnetization direction determined by a net magnetic field present at the location of the region; and detector means for receiving the read light beam from the region and for producing a magneto-optic signal indicative of the magnetization direction of the region.

Claim 7

The optical memory of claim 4 wherein the magnetic film is manganese bismuth.

Claim 8

The optical memory of claim 5 wherein the read light beam has an intensity sufficient to temporarily heat a region to a temperature above about 180*C but less than about 360* C.

Claim 9

The optical memory of claim 4 wherein the second light source means comprises: beam splitter means positioned in the path of the write light beam to split off a portion of the write light beam, thereby forming the read light beam; and mirror means for directing the read light beam toward the magnetic film.