Magneto-optical pickup device having phase compensating circuitry
First Claim
1. A magneto-optical pickup device, comprising:
- a) a substrate;
b) a light emitting device;
c) a filter polarizing light emitted by said light emitting device to generate a first polarized component of light;
d) a differential photo-detecting unit which separates light into first and second polarized components of light;
e) an optical waveguide operatively configured and disposed on said substrate to guide said first polarized component of light from said filter onto a magneto-optical recording medium, and to guide light reflected back from said medium to said differential photo-detecting unit;
f) a differential amplifying circuit coupled to an output of said differential photo-detecting unit, said differential amplifying circuit providing an output signal which varies according to a magnetization direction of magnetization information recorded on the magneto-optical recording medium;
g) a feedback circuit coupled to said differential amplifying circuit, which feedback circuit is configured to generate a phase compensating signal that correlates to a phase difference between said first and second polarized components of light in said light reflected from said magneto-optical recording medium; and
h) phase compensating means for receiving said phase compensating signal and minimizing said phase difference.
1 Assignment
0 Petitions
Accused Products
Abstract
Even when manufacturing of a waveguide is fluctuated and an optical parameter is fluctuated or a wavelength of emitted light is fluctuated, a phase difference between two intrinsic modes can be compensated (positive integral multiple of π). Thus, it is possible to prevent a reproduced signal from being deteriorated by elliptically polarized light. A magneto-optical reproducing pickup includes an optical waveguide (4) for guiding light reflected on a magneto-optical recording medium to a differential photo-detecting unit (9) side and phase compensating circuitry for compensating a phase difference between light components of a TE mode an a TM mode included in reflected light. In this case, the phase compensating circuitry comprises the optical waveguide (4) composed of a substrate formed of an electrooptic crystal and a thin film having a light refractive index higher than that of the substrate formed on the substrate, phase control electrodes (21a and 22b) for applying an electric field to the optical waveguide (4) in the direction along the TM mode and a feedback circuit (11).
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Citations
23 Claims
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1. A magneto-optical pickup device, comprising:
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a) a substrate; b) a light emitting device; c) a filter polarizing light emitted by said light emitting device to generate a first polarized component of light; d) a differential photo-detecting unit which separates light into first and second polarized components of light; e) an optical waveguide operatively configured and disposed on said substrate to guide said first polarized component of light from said filter onto a magneto-optical recording medium, and to guide light reflected back from said medium to said differential photo-detecting unit; f) a differential amplifying circuit coupled to an output of said differential photo-detecting unit, said differential amplifying circuit providing an output signal which varies according to a magnetization direction of magnetization information recorded on the magneto-optical recording medium; g) a feedback circuit coupled to said differential amplifying circuit, which feedback circuit is configured to generate a phase compensating signal that correlates to a phase difference between said first and second polarized components of light in said light reflected from said magneto-optical recording medium; and h) phase compensating means for receiving said phase compensating signal and minimizing said phase difference. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19)
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20. A magneto-optical reproducing pickup comprising:
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light emitting means; an optical waveguide guiding a first mode light component of light emitted from said light emitting means to a recording medium and guiding light reflected from said recording medium to a photo-detector; and phase compensating means for compensating a phase difference between light components of said first mode and of a second mode said phase compensating means including a temperature control element formed on said optical waveguide.
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21. A magneto-optical pickup device comprising:
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a) a substrate; b) a light emitting device; c) a filter polarizing light emitted by said light emitting device to generate a first polarized component of light; d) a differential photo-detecting unit which separates light into first and second polarized component of light; e) an optical waveguide operatively configured and disposed on said substrate to guide said first polarized component of light from said filter onto a magneto-optical recording medium, and to guide light reflected back from said medium to said differential photo-detecting unit, wherein said waveguide comprising a first path that guides said polarized light from said filter to said magneto-optical recording medium and a returning path that branches out from said first path thereby to guide said light reflected from said magneto-optical recording medium to said differential photo-detecting unit; f) a differential amplifying circuit coupled to an output of said differential photo-detecting unit, said differential amplifying circuit providing an output signal which varies according to a magnetization direction of magnetization information recorded on the magneto-optical recording medium; g) a feedback circuit coupled to said differential amplifying circuit, which feedback circuit is configured to generate a phase compensating signal that correlates to a phase difference between said first and second polarized components of light in said light reflected from said magneto-optical recording medium; and h) phase compensating means for receiving said phase compensating signal and minimizing said phase difference, wherein said means for receiving said phase compensating signal and minimizing said phase difference comprises an electrode unit operatively positioned about said waveguide to effect a change in a refraction width in said waveguide when an electrical signal is applied thereto.
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22. A magneto-optical pickup device, comprising:
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a) a substrate; b) a light emitting device; c) a filter polarizing light emitted by said light emitting device to generate a first polarized component of light; d) a differential photo-detecting unit which separates light into first and second polarized components of light; e) an optical waveguide operatively configured and disposed on said substrate to guide said first polarized component of light from said filter onto a magneto-optical recording medium, and to guide light reflected back from said medium to said differential photo-detecting unit, wherein said waveguide comprising a first path that guides said polarized light from said filter to said magneto-optical recording medium and a returning path that branches out from said first path thereby to guide said light reflected from said magneto-optical recording medium to said differential photo-detecting unit; f) differential amplifying circuit coupled to an output of said differential photo-detecting unit, said differential amplifying circuit providing an output signal which varies according to a magnetization direction of magnetization information recorded on the magneto-optical recording medium; g) a feedback circuit coupled to said differential amplifying circuit, which feedback circuit is configured to generate a phase compensating signal that correlates to a phase difference between said first and second polarized components of light in said light reflected from said magneto-optical recording medium; and h) phase compensating means for receiving said phase compensating signal and minimizing said phase difference, wherein said phase compensating means comprises means for varying the wavelength of the light emitted by said light emitting device.
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23. A magneto-optical pickup device comprising:
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a) a substrate; b) a light emitting device; c) a filter polarizing light emitted by said light emitting device to generate a first polarized component of light; d) a differential photo-detecting unit which separates light into first and second polarized components of light; e) an optical waveguide operatively configured and disposed on said substrate to guide said first polarized component of light from said filter onto a magneto-optical recording medium, and to guide light reflected back from said medium to said differential photo-detecting unit, wherein said waveguide comprising a first path that guides said polarized light from said filter to said magneto-optical recording medium and a returning path that branches out from said first path thereby to guide said light reflected from said magneto-optical recording medium to said differential photo-detecting unit; f) a differential amplifying circuit coupled to an output of said differential photo-detecting unit, said differential amplifying circuit providing an output signal which varies according to a magnetization direction of magnetization information recorded on the magneto-optical recording medium; g) a feedback circuit coupled to said differential amplifying circuit, which feedback circuit is configured to generate a phase compensating signal that correlates to a phase difference between said first and second polarized components of light in said light reflected from said magneto-optical recording medium; and h) phase compensating means for receiving said phase compensating signal and minimizing said phase difference, wherein said phase compensating means comprises a temperature control element operatively disposed on said waveguide to control a temperature of said waveguide.
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Specification