Magneto-optical disk drive utilizing leakage magnetic field from permanent magnets as external magnetic field

• US 6,178,142 B1
• Filed: 04/28/1998
• Issued: 01/23/2001
• Est. Priority Date: 04/28/1997
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Fujita, Masayuki
• Primary Examiner(s): DINH, TAN X
• Application Number:
  US09/066,856
• Time in Patent Office: 1,001 Days
• Field of Search: 369/13, 369/14, 369/110, 369/116, 369/114, 300/59
• US Class Current: 369/13.15
• CPC Class Codes: G11B 11/10534 for recording by magnetising, demagnetising or transfer of magnetisation, by radiation, e.g. for thermomagnetic recording
• CPC Class Codes: G11B 11/10552 Arrangements of transducers relative to each other, e.g. coupled heads, optical and magnetic head on the same base for relative movement of transducers G11B11/10573
• CPC Class Codes: G11B 11/10576 with provision for moving the transducers for maintaining alignment or spacing relative to the carrier

Abstract

An optical disk drive for writing, erasing and reading data on a recording surface of an optical disk medium, includes an objective lens which irradiates the recording surface with rays, a magnetic circuit which generates an electromagnetic force for positioning the objective lens freely at a desired location, and a lens actuator including a support device for supporting the objective lens. The magnetic circuit includes two permanent magnets which are disposed so as to oppose poles having the same polarity to each other with the objective lens interposed therebetween. The magnetic circuit forms, in a direction perpendicular to a surface of the objective lens, a leakage magnetic field having an intensity which covers a range of external bias magnetic field intensities required for recording and erasing data on the recording surface of the optical disk medium.

Claims

1. An optical disk drive for writing, erasing and reading data on a recording surface of an optical disk medium, comprising:

an objective lens which irradiates said recording surface with rays;

a magnetic circuit which generates an electromagnetic force for positioning said objective lens freely at a desired location; and

a lens actuator including support means for supporting said objective lens,

wherein said magnetic circuit includes two permanent magnets which are disposed so as to oppose poles having the same polarity to each other with said objective lens interposed therebetween, and

wherein said magnetic circuit forms, in a direction perpendicular to a surface of said objective lens, a leakage magnetic field having an intensity which covers a range of external bias magnetic field intensities required for recording and erasing data on said recording surface of said optical disk medium.

2. An optical disk drive according to claim 1,

wherein said optical disk drive further comprises means for forming, on the recording surface of said optical disk medium, a bias magnetic field which has a direction reverse to that of the magnetic field leaking from said magnetic circuit and has an intensity covering said range of the external bias magnetic field intensities required for writing and erasing data on said recording surface of said optical disk medium.

3. An optical disk drive according to claim 1,

wherein said range of the external bias magnetic field intensities is 100 to 500 oersteds.

4. An optical disk drive according to claim 2, wherein said means for forming a bias magnetic field comprises a coil which is disposed in opposition to said lens actuator with said optical medium interposed therebetween.

5. An optical disk drive according to claim 2, wherein said bias magnetic field forming means comprises a permanent magnet.

6. An optical disk drive according to claim 5, wherein said permanent magnet is disposed in opposition to said lens actuator with said optical disk medium interposed therebetween, movable along or in parallel with said optical disk medium and is selectively set aside from a direction perpendicular to said objective lens.

7. An optical disk drive according to claim 1,

wherein said support means comprises wires.

8. An optical disk drive according to claim 1,

wherein said support means comprises a leaf spring.

9. An optical disk drive according to claim 2, wherein said range of the external bias magnetic field intensities is 100 to 500 oersteds.

10. An optical disk drive according to claim 2, wherein said support means comprises wires.

11. An optical disk drive according to claim 2, wherein said support means comprises a leaf spring.

12. An optical disk drive comprising:

a lens which irradiates a recording surface of a medium with rays;

a circuit which generates a force for positioning said lens freely at a desired location; and

a lens actuator including a support device for supporting said lens,

wherein said circuit includes two permanent magnets which are disposed so as to oppose poles having the same polarity to each other with said lens interposed therebetween, and

wherein said circuit forms, in a direction perpendicular to a surface of said lens, a leakage magnetic field having an intensity which covers a range of external bias magnetic field intensities required for recording and erasing data on said recording surface of said medium.

13. The optical disk drive according to claim 12, further comprising a device for forming a bias magnetic field which is disposed in opposition to said lens actuator with said optical disk medium interposed therebetween.

14. The optical disk drive according to claim 12, wherein said lens comprises an objective lens.

15. An optical disk drive comprising:

a lens which irradiates a recording surface of a medium with rays;

a circuit which generates a force for positioning said lens freely at a desired location; and

a lens actuator including a support device for supporting said lens,

wherein said circuit includes first and second magnets which are disposed so as to oppose poles having the same polarity to each other with said lens interposed therebetween, and

wherein said circuit forms a leakage magnetic field having an intensity which covers a range of external bias magnetic field intensities required for recording and erasing data on said recording surface of said medium.