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US4803579A Expired / Lapsed US ⏱️ 0.0 years remaining

Magneto-optical information reproducing apparatus in which divided reproducing lights are differentially detected by a photodetector having no amplifying action through an analyzer whose transmission axis azimuth is optimized

Assignee: Canon Inc
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Filing: 1987-10-13
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Granted: 1989-02-07
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Expires: 2007-10-13
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Abstract

Abstract In a magneto-optical information reproducing apparatus comprising means for applying a light beam polarized in a predetermined direction onto a recording medium on which information is magnetically recorded, means for dividing the reflected or transmitted light beam from the recording medium modulated into a polarized state in conformity with the information by the magneto-optical effect, a plurality of analyzer means having their optic axes inclined in opposite directions with respect to the predetermined direction and analyzing the divided light beams, a plurality of photodetectors having no amplifying action and photoelectrically detecting the light beams transmitted through the plurality of analyzer means, and a signal processing circuit for amplifying the detection signals of the plurality of photodetectors, differentiating them and reproducing the information, the angle θ A formed between the optic axes of the plurality of analyzer means and the predetermined direction satisfies the following conditions: ##EQU1## where I 0 is the quantity of light of the incident light beam on the recording medium, R is the amplitude reflectance of the recording medium, ε is the light utilization efficiency of the optical system from the recording medium to the photodetectors except the analyzer means, κ is the photoelectric conversion efficiency of the photodetectors, e is the amount of charge, T is the thermal noise of the amplifying means in a magneto-optical signal observation frequency, ΔB is the band width of the detection signals, t A is the amplitude transmittance of the analyzer means, and η A is the extinction ratio of the analyzer means.

Inventors

  • 👤 Osamu Koyama

Bibliographic Details

Application Number —
Jurisdiction US
Data Source google_patents
Last Synchronized 2026-11-02 23:40
CPC Classifications
G; G11; G11B; G11B11/00; G11B11/10; G11B11/105; G11B11/10532; G11B11/10541; G11B11/10543

Claims Analysis

Total Claims: 6
Claim 1
Independent Claim 252 words
A magneto-optical information reproducing apparatus comprising means for applying a light beam polarized in a predetermined direction onto a recording medium on which information is magnetically recorded, means for dividing the reflected or transmitted light beam from said recording medium modulated into a polarized state in conformity with said information by the magneto-optical effect, a plurality of analyzer means having their optic axes inclined in opposite directions with respect to said predetermined direction and analyzing said divided light beams, a plurality of photodetectors having no amplifying action and photoelectrically detecting the light beams transmitted through said plurality of analyzer means, and a signal processing means for amplifying the detection signals of said plurality of photodetectors, differentiating them and reproducing said information, the angle θ A formed between the optic axes of said plurality of analyzer means and said predetermined direction satisfying the following conditions: ##EQU28## where I 0 is the quantity of light of the incident light beam on said recording medium, R is the amplitude reflectance of said recording medium, ε is the light utilization efficiency of the optical system from the recording medium to the photodetectors except said analyzer means, κ is the photoelectric conversion efficiency of said photodetectors, e is the amount of charge, T is the thermal noise of said amplifying means in a magneto-optical signal observation frequency, ΔB is the band width of the detection signals, t A is the amplitude transmittance of said analyzer means, and η A is the extinction ratio of said analyzer means.
Claim 2
Dependent Claim 252 words
A magneto-optical information reproducing apparatus comprising means for applying a light beam polarized in a predetermined direction onto a recording medium on which information is magnetically recorded, means for dividing the reflected or transmitted light beam from said recording medium modulated into a polarized state in conformity with said information by the magneto-optical effect, a plurality of analyzer means having their optic axes inclined in opposite directions with respect to said predetermined direction and analyzing said divided light beams, a plurality of photodetectors having no amplifying action and photoelectrically detecting the light beams transmitted through said plurality of analyzer means, and a signal processing means for amplifying the detection signals of said plurality of photodetectors, differentiating them and reproducing said information, the angle θ A formed between the optic axes of said plurality of analyzer means and said predetermined direction satisfying the following conditions: ##EQU28## where I 0 is the quantity of light of the incident light beam on said recording medium, R is the amplitude reflectance of said recording medium, ε is the light utilization efficiency of the optical system from the recording medium to the photodetectors except said analyzer means, κ is the photoelectric conversion efficiency of said photodetectors, e is the amount of charge, T is the thermal noise of said amplifying means in a magneto-optical signal observation frequency, ΔB is the band width of the detection signals, t A is the amplitude transmittance of said analyzer means, and η A is the extinction ratio of said analyzer means.
Claim 3
Dependent Claim 84 words
A magneto-optical information reproducing apparatus according to claim 1, further comprising a polarizing beam splitter for reflecting the light beam from said medium and directing it to said dividing means and wherein the amplitude reflectance r p of said polarizing beam splitter for the polarized component in said predetermined direction and the amplitude reflectance r s of said polarizing beam splitter for the polarized component in a direction perpendicular to said predetermined direction satisfy the following conditions, respectively: 0.1≦|r.sub.p |.sup.2 ≦0.5 |r.sub.s |.sup.2 ˜1.
Claim 4
Dependent Claim 85 words
A magneto-optical information reproducing apparatus according to claim 1, further comprising a polarizing beam splitter for transmitting therethrough the light beam from said medium and directing it to said dividing means and wherein the amplitude transmittance t s of said polarizing beam splitter for the polarized component in said predetermined direction and the amplitude transmittance t p of said polarizing beam splitter for the polarized component in a direction perpendicular to said predetermined direction satisfy the following conditions, respectively: 0.1<|t.sub.s |.sup.2 <0.5 |t.sub.p |.sup.2 ˜1.
Claim 5
Dependent Claim 38 words
A magneto-optical information reproducing apparatus according to claim 1, wherein said means for applying a light beam comprises a light source and an optical system for condensing the light beam emitted from said light source on said medium.
Claim 6
Dependent Claim 15 words
A magneto-optical information reproducing apparatus according to claim 1, wherein said photodetectors are PIN photodiodes.

References Cited (Backward Citations)

US4561032A Cited
US4558440A Cited
US4569035A Cited

USPTO Annuity & Maintenance Windows

Annuity Stage Window Opens Payment Deadline Surcharge Period Until Estimated Fee Status
3.5 Years (Year 4) 1992-02-07 1992-08-08 1993-02-07 $2000.00 Window Closed / Lapsed
7.5 Years (Year 8) 1996-02-07 1996-08-08 1997-02-07 $3760.00 Window Closed / Lapsed
11.5 Years (Year 12) 2000-02-07 2000-08-08 2001-02-07 $7700.00 Window Closed / Lapsed

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