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US0O5448538A
[ii] Patent Number: 5,448,538 [45] Date of Patent: Sep. 5,1995
[54] ELECTROMAGNET COILS HAVING A
DIFFERENT INDUCTANCE DURING
MAGNETO-OPTICAL RECORDING AND
REPRODUCING
[75] Inventors: Katsuhisa Aratani, Chiba; Tetsuhiro Sakamoto, Tokyo, both of Japan
[73] Assignee: Sony Corporation, Tokyo, Japan
[21] Appl. No.: 267,675
[22] Filed: Jun. 29,1994
[30] Foreign Application Priority Data
Jul. 7, 1993 [JP] Japan 5-168124
[51] Int. CI.* G11B 13/04
[52] U.S. CI 369/13; 360/114
[58] Field of Search 369/13, 14; 360/114,
360/59, 46
[56] References Cited
U.S. PATENT DOCUMENTS
5,157,641 10/1992 Lehureau 369/13
5,229,902 7/1993 Zucker et al 369/13
5,313,444 5/1994 Ishii et al 369/13
5,329,408 7/1994 Fuji 360/114
5,351,155 9/1994 Ishii 360/46
FOREIGN PATENT DOCUMENTS
5101459 4/1993 Japan 369/13
Primary Examiner—Georgia Y. Epps
Assistant Examiner—Tan Dinh
In a magneto-optical recording/reproducing apparatus in which a signal is recorded by the magnetic field modulation system and which has a device for applying an external magnetic field at the time of reproduction, the apparatus has an external magnetic field generating electromagnet commonly used for recording and reproducing, the inductance of a coil in the electromagnet at the time of reproduction is larger than the inductance of the coil at the time of recording. In another magnetooptical recording/reproducing apparatus in which a signal is recorded by the magnetic field modulation system and which has a device for applying an external magnetic field at the time of reproduction, the apparatus has an external magnetic field generating electromagnet having an electromagnet coil wound around a magnetic core and commonly used for recording and reproducing, and another external magnetic field generating device capable of being magnetically coupled with the magnetic core of the electromagnet and decoupled therefrom. At the time of recording, a signal is recorded by the magnetic field modulation by energizing the electromagnet while the other external magnetic field generating device is magnetically decoupled from the electromagnet, while at the time of reproduction, the other external magnetic field generating device is magnetically coupled with the electromagnet.
4 Claims, 8 Drawing Sheets
