| 摘要 |
PURPOSE:To remove a noise component and to increase a reproduced output by rotating the polarized surface of reflected or transmitted light from an optical magnetic recording medium so as to branch into two parts and controlling the polarized surface in the direction where the low frequency component of a differential output obtained by photoelectrically transferring a detection output comes to zero. CONSTITUTION:An optical magnetic disk 2 with a magnetic film 2 is rotated by a motor 3, and light out of a linear polarization semiconductor laser 4 is irradiated on the magnetic film 2. The reflected light from the magnetic film 2 is led to a beam splitter 10 and a four-division photodetector 13, and makes incident on a polarization prism 16 through a 1/4 wavelength plate 14 and a convex lens 15 so as to branch into two parts. The branched light makes incident on photodetectors 17a and 17b, is converted into an electrical signal and inputted to a differential circuit 22. Its output is led to a terminal 23 as a reproduced signal output and to an LPF 24, and its low frequency component is detected. Then the rotating angle of the wavelength plate 14 is controlled in the direction where the low frequency component comes to zero. Thus the noise output included in the reproduced signal is removed in such a way, whereby the reproduced output can be increased. |
