| 摘要 |
PURPOSE:To reduce the size and weight of an optical head by providing an optical splitting member which splits light from the information storage medium and guides it to a photodetector, and providing this member with a plane and an aspherical curved surface slanting to each other so that part of light from the information storage medium is transmitted or reflected by the plane and the remainder is transmitted or reflected by the aspherical curved surface. CONSTITUTION:Divergent laser light L from a semiconductor laser 1 as a light source is collimated by a collimator lens 2 into parallel luminous flux, which is guided to a polarization beam splitter 3. The beam splitter 3 has a polarization beam splitting surface 6 sandwiched between two prisms 4 and 5 and the laser light L has its ellipse corrected by passing through the laser light incidence surface 4a of the prism 4 and is then guided to an objective 8 through a quarter- wavelength plate 7 and converged on the information storage medium 9. The optical splitting member 3 has the plane 10 and aspherical curved surface 11 slanting to each other and part of light from the storage medium 9 is transmitted or reflected by the plane 10 while the remaining light is transmitted or reflected by the aspherical curved surface 11.
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