Optics: measuring and testing – By polarized light examination – With polariscopes
Patent
1980-06-30
1983-10-18
Punter, William H.
Optics: measuring and testing
By polarized light examination
With polariscopes
356367, 356369, 360114, 365122, G01N 2121, G01J 404
Patent
active
044102771
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to an apparatus for detecting magneto-optical anisotropy of a magnetic medium. The magneto-optical anisotropy dealt with in this invention represents the property such as double refraction and circular dichroism, that changes the linearly polarized light into the elliptically polarized light or causes a change in the ellipticity of the elliptically polarized light. The term "elliptically polarized light" used in this specification includes the circularly polarized light as a special case where the ellipticity takes a specific value.
BACKGROUND ART
In an apparatus used conventionally, as a magneto-optical anistropy detector of a magnetic medium, for reading out information recorded in accordance with the magnetized state of the magnetic medium, when the linearly polarized light passes through the magnetic medium or is reflected on the surface of the magnetic medium, the incident linearly polarized light is slightly converted into the elliptically polarized light and the principal axis of the ellipse slightly rotates from the polarizing direction of the incident linearly polarized light. Conventionally, the rotational angle of the principal axis of polarization is measured using a polarizing element and a polarization analyzer, but this method involves the drawbacks in that the apparatus is complicated and a signal-to-noise ratio is low.
DISCLOSURE OF INVENTION
The present invention provides an apparatus for detecting magneto-optical anisotropy which employs the elliptically polarized light in order to eliminate the abovementioned problems with the conventional magneto-optical anisotropy detector and which has a wider range of application and higher performance by measuring the change of the ellipticity of the elliptically polarized light.
BRIEF DESCRIPTION OF DRAWINGS
FIGS. 1 and 2 are block diagrams useful for explaining the fundamental construction of the present invention;
FIG. 3 is a block diagram showing the construction of an embodiment of the apparatus for detecting the magneto-optical anisotropy of the present invention;
FIG. 4 is a schematic view of the polarized state of light useful for explaining the operation of the embodiment shown in FIG. 3;
FIG. 5 is a block diagram showing the construction when the present invention is applied to a magnetic disc;
FIG. 6 is a block diagram showing the construction of another embodiment of the apparatus for detecting the magneto-optical anisotropy of the present invention;
FIG. 7 is a block diagram showing the construction of still another embodiment of the apparatus for detecting the magneto-optical anisotropy of the present invention;
FIG. 8 is a block diagram showing the construction when the present invention is applied to an optical disc;
FIGS. 9 and 10(a)-(c) are schematic views useful for explaining the operation of the apparatus shown in FIG. 8;
FIG. 11 is a block diagram showing the construction of still another embodiment of the apparatus for detecting the magneto-optical anisotropy of the present invention;
FIGS. 12(a) and 12(b) schematic views showing the principal portions forming the embodiment shown in FIG. 11;
FIGS. 13(a) and 13(b) are schematic views useful for explaining the operation of the embodiment shown in FIG. 11;
FIG. 14 is a block diagram showing the construction of still another embodiment of the apparatus for detecting the magneto-optical anisotropy of the present invention;
FIG. 15 is a schematic view showing the axis of polarization for explaining the operation of the embodiment shown in FIG. 14; and
FIG. 16 is a schematic view showing another construction of the principal portions of the embodiment shown in FIG. 14.
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, the present invention will be explained in detail with reference to embodiments thereof.
FIGS. 1 and 2 illustrate the fundamental construction of the present invention. More specifically, FIG. 1 shows the apparatus of a transmission type in which the ray of light passes through a medium and FIG. 2 shows the appar
REFERENCES:
patent: 3445833 (1969-05-01), Lins
patent: 3775570 (1973-11-01), Lewicki et al.
patent: 4105338 (1978-08-01), Kuroha
Aben et al., "Photoelectric Magnetopolarimeter for Studying Inhomogeneous Optically Anisotropic Media", Sov. J. Opt. Technology 9-1977, pp. 534-536.
Matsuura et al., "Measurement of Flow-Birefringence Using a Circularly Polarized Laser Beam", Optics & Laser Tech. 10-1978, pp. 237-240.
Treves, D. "Magneto-Optic Detection of High Density Recordings", Jr. App. Physics 3-1967, pp. 1192-1196.
Lentz et al., "Magneto-Optical Readout" Electronics 9-1-61, pp. 36-39.
Ojima Masahiro
Yamamoto Manabu
Hitachi , Ltd.
Punter William H.
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