PURPOSE: To improve the S/N of a reproduced signal and to stabilize servo control, by introducing the light radiated from a light source to a magnetic medium after converting the light into the linearly polarized light by means of an optical element, then, splitting the light reflected from the magnetic medium into two parts by an optical splitting element, and detecting a focussing error and a tracking error by the transmitted light.
CONSTITUTION: A 1/2 wavelength plate 13 is installed between a collimating lens 2 and polarizer 3 and, at the same time, a polarization beam splitter 14 which acts as an analyzer is used instead of the 2nd half-mirror. The light coming out from a semiconductor laser 1 passes through the plate 13, by which their plane of polarization is rotated to an optional angle, then the light is changed into linearly polarized light having a better degree of polarization owing to passing through the polarizer 3. The linearly polarized lights are introduced to a magnetic medium 6 after passing through the 1st half-mirror 4. The light reflected from the magnetic medium 6 is changed to the light whose polarization is modulated by ±θ owing to magnetic Kerr effect depending upon the direction of magnetization of the medium 6. It is reflected by the 1st half- mirror 4, and reflected light is introduced to the polarization beam splitter 14 which is an analyzer. The splitter 14 passes all the P-polarized light, but totally reflects the S-polarized light.
YANAGIDA TSUNEO
YAMAMIYA KUNIO
SAKAMOTO MASAHARU
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