G - Physics – 11 – B
Patent
G - Physics
11
B
352/32.1, 352/33
G11B 7/00 (2006.01) G11B 11/10 (2006.01) G11B 11/105 (2006.01)
Patent
CA 2037428
A reproducing optical device for a magneto-optical recording medium related to the present invention having light sources that emit linearly polarized lights towards a magneto-optical recording medium, polarization directions of the linearly polarized lights being mutually orthogonal. A quarter wavelength plate disposed between the recording medium and the light sources converts each of the linearly polarized lights into right and left circularly polarized lights respectively. Corresponding to recorded information, the recording medium has magnetized sections that are magnetized in a perpendicularly upward and downward direction with respect to a medium surface. Moreover, the recording medium displays the property of circular dichroism. When the right circularly polarized light and the left circularly polarized light are reflected off the recording medium, a first and a second photodetector generate a first and a second reproduced signal respectively, based on variation in reflected light intensity of each of the circularly polarized lights. This variation corresponds to the upward and the downward magnetization directions of the magnetized sections and is due to the circular dichroism effect. There is a phase difference of half a cycle between the first and the second reproduced signal and the signals vary inversely with respect to each other. Consequently, disk noise is cancelled by differentially amplifying the first and the second reproduced signal, and an SN ratio of a reproduced signal thereby can be improved.
Murakami Yoshiteru
Nakajima Junsaku
Ohta Kenji
Takahashi Akira
G. Ronald Bell & Associates
Murakami Yoshiteru
Nakajima Junsaku
Ohta Kenji
Sharp Kabushiki Kaisha
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