Magneto-optical recording and reproducing apparatus with magnetic field controller

Claim 2

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means. wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes an equalizer circuit applied with the output signal of said first power amplifier and a coil current controlling circuit applied with an output signal of said equalizer circuit for controlling a current to be supplied to said electromagnetic coil, thereby controlling the strength of said magnetic field.

Claim 3

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means. wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said compensating circuit, a second power amplifier applied with an output of said gain adjusting circuit, and a coil position driving device applied with an output signal of said second power amplifier for controlling a position of said electro-magnetic coil so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 4

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means. wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said compensating circuit, a second power amplifier applied with an output of said gain adjusting circuit, and a coil position driving device applied with an output signal of said second power amplifier for controlling a position of said electro-magnetic coil so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 5

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means, wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a low pass filter applied with an output signal of said gain adjusting circuit, a second power amplifier applied with an output of said low pass filter, and a coil position driving device applied with an output signal of said second power amplifier for controlling a position of said electromagnetic coil so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 6

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means, wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a low pass filter applied with an output signal of said gain adjusting circuit, a second power amplifier applied with an output of said low pass filter, and a coil position driving device applied with an output signal of said second power amplifier for controlling a position of said electromagnetic coil so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 7

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and; magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means, wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a magnet position driving device for controlling a position of said permanent magnet so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 8

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and; magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means, wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a magnet position driving device for controlling a position of said permanent magnet so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 9

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means, wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, and wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a magnet position driving device for controlling a position of said permanent magnet so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 10

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means, wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, and wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a magnet position driving device for controlling a position of said permanent magnet so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 11

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means. wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a second power amplifier applied with an output signal of said gain adjusting gain, and a magnet position driving device applied with an output signal of said second power amplifier for controlling a position of said permanent magnetic in accordance with the inputted signal so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 12

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means. wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a second power amplifier applied with an output signal of said gain adjusting gain, and a magnet position driving device applied with an output signal of said second power amplifier for controlling a position of said permanent magnetic in accordance with the inputted signal so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 13

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means, wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a low pass filter applied with an output signal of said gain adjusting circuit, a second power amplifier applied with an output of said low pass filter, and a magnet position driving device applied with an output signal of said second power amplifier for controlling a position of said permanent magnet in accordance with the inputted signal so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 14

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal; objective lens driving means for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of a distance between said magneto-optical disk and said magnetic field generating means, wherein said focus error detecting means includes light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk, and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means, wherein said objective lens driving means includes a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier, and wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a low pass filter applied with an output signal of said gain adjusting circuit, a second power amplifier applied with an output of said low pass filter, and a magnet position driving device applied with an output signal of said second power amplifier for controlling a position of said permanent magnet in accordance with the inputted signal so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 15

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means, wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes an equalizer circuit applied with the output signal of said first power amplifier and a coil current controlling circuit applied with an output signal of said equalizer for controlling a current to be supplied to said electromagnetic coil, thereby controlling the strength of said magnetic field.

Claim 16

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control said magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means, wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes an equalizer circuit applied with the output signal of said first power amplifier and a coil current controlling circuit applied with an output signal of said equalizer for controlling a current to be supplied to said electromagnetic coil, thereby controlling the strength of said magnetic field.

Claim 17

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a second power amplifier applied with an output of said gain adjusting circuit, and a coil position driving device applied with an output signal of said second power amplifier for controlling a position of said electro-magnetic coil so that the strength of said magnetic of said magnetic recording layer is kept constant.

Claim 18

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a second power amplifier applied with an output of said gain adjusting circuit, and a coil position driving device applied with an output signal of said second power amplifier for controlling a position of said electro-magnetic coil so that the strength of said magnetic of said magnetic recording layer is kept constant.

Claim 19

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magnetic-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a low pass filter applied with an output signal of said gain adjusting circuit, a second power amplifier applied with and output of said low pass filter, and a coil position driving device applied with an output of said second amplifier for controlling a position of said electromagnetic coil so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 20

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magnetic-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes an electromagnetic coil, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a low pass filter applied with an output signal of said gain adjusting circuit, a second power amplifier applied with and output of said low pass filter, and a coil position driving device applied with an output of said second amplifier for controlling a position of said electromagnetic coil so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 21

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a magnet position of said permanent magnet so that the strength of said magnetic field of said magnetic recording layer is kept constant.

Claim 22

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a magnet position of said permanent magnet so that the strength of said magnetic field of said magnetic recording layer is kept constant.

Claim 23

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a second power amplifier applied with an output signal of said gain adjusting circuit, and a magnet position driving device applied with an output signal of said second power amplifier for controlling a position of said permanent magnet in accordance with an inputted signal so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 24

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a second power amplifier applied with an output signal of said gain adjusting circuit, and a magnet position driving device applied with an output signal of said second power amplifier for controlling a position of said permanent magnet in accordance with an inputted signal so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 25

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a low pass filter applied with an output signal of said gain adjusting circuit, a second power amplifier for controlling a position of said permanent magnet in accordance with an inputted signal so that the strength of said magnetic field at said magnetic recording layer is kept constant.

Claim 26

A magneto-optical recording and reproducing apparatus comprising: a magneto-optical disk including a magnetic recording layer, an information signal being recorded as a change in the direction of magnetization of said magnetic recording layer; radiation means including an objective lens for converging a laser beam to irradiate said optical magnetic disk; focus error detecting means for detecting a change of a distance between said objective lens and said magneto-optical disk to produce a focus error signal and including light receiving means for receiving a reflected beam of the laser beam irradiated to said magneto-optical disk and an error detecting circuit for producing said focus error signal in accordance with an output signal of said light receiving means; objective lens driving means having a phase compensating amplifier applied with said focus error signal from said error detecting circuit, a first power amplifier applied with an output signal of said phase compensating amplifier, and an objective lens driving device for driving said objective lens in accordance with an output signal of said first power amplifier and for generating an objective lens driving signal in accordance with said focus error signal to drive said objective lens so that it follows an axial runout of said magneto-optical disk in a direction of thickness thereof; magnetic field generating means for applying a magnetic field to said magnetic recording layer; and magnetic field strength controlling means for receiving said objective lens driving signal generated from said objective lens driving means in accordance with said focus error signal to control signal magnetic field generating means in accordance with said objective lens driving signal so that the strength of said magnetic field applied to said magnetic recording layer is kept constant in said magnetic recording layer irrespective of a change of distance between said magneto-optical disk and said magnetic field generating means; wherein said magnetic field generating means includes a permanent magnet, and said magnetic field strength controlling means includes a gain adjusting circuit applied with the output signal of said phase compensating circuit, a low pass filter applied with an output signal of said gain adjusting circuit, a second power amplifier for controlling a position of said permanent magnet in accordance with an inputted signal so that the strength of said magnetic field at said magnetic recording layer is kept constant.