Magneto-optic player with improved C/N ratio

Details Magneto-optic player with improved C/N ratio Magneto-optic player with improved C/N ratio

1990-01-19

1992-06-23

Psitos, Aristotelis

Dynamic magnetic information storage or retrieval

Head

Read only detector using light for reading magnetically...

369110, 369 13, G11B 5127, G11B 1112, G11B 1304

Patent

active

051248689

ABSTRACT:
A magneto-optic player for reading an information signal stored in a magneto-optical record medium in the form of vertical magnetization including a semiconductor laser emitting a linearly polarized laser light beam, a beam splitter for transmitting the laser light beam, an objective lens for projecting the laser light beam transmitted through the beam splitter onto the record medium and for directing light reflected by the record medium, the light being subjected to Kerr rotation the rotational direction of which is dependent upon the direction of the vertical magnetization. A first quarter-wavelength plate arranged between the objective lens and the beam splitter for converting the linearly polarized light reflected by the record medium into an elliptically polarized light the rotational direction of which is determined by the direction of the vertical magnetization. A second quarter-wavelength plate arranged to receive the elliptically polarized light reflected by the beam splitter for converting it into elliptically polarized light the direction of the major axis of which is aligned with P-polarization or S-Polarization depending upon the rotational direction, a polarization beam splitter for splitting the elliptically polarized light into P-polarized and S-polarized components, two photodetectors for receiving the P-polarized and S-polarized components, respectively, and a differential amplifier for deriving a difference between outputs of the two photodetectors as a reproduced information signal.

REFERENCES:
patent: 4691308 (1987-09-01), Takagi et al.
patent: 4841510 (1989-06-01), Yoshizawa
patent: 4953124 (1990-08-01), Koyama
patent: 4955006 (1990-09-01), Fukushima et al.
P. Wolniansky, et al., "Magneto-optical Measurements of Hysteresi Loop and Anisotropy Energy Constants on Amorphous Tb.sub.x Fe.sub.1 -X alloys", J. Applied Physics, Jul. 1, 1986, pp. 346-351.
T. D. Milster, "Characteristics of Phase-Compensation Techniques in Magnetooptical Read-Back Systems", SPIE vol. 1166, Polarization Considerations for Optical Systems II, 1989, pp. 355-365.

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