| 摘要 |
PURPOSE:To use a red laser indispensable to reproduce high packing density record as a light source in an optical head in which a cylindrical lens, etc., is omitted and the size is reduced. CONSTITUTION:A laser light (S-polarized) from a red semiconductor laser is reflected by a parallel flat plate (polarization beam splitter) 2 in the state of non-parallel beam light, circularly polarized through a collimator lens 3.1/4 wavelength plate 4, and emitted to a disk recording surface 6 through an objective lens 5. The reflected light is passed through the plate 2 (the splitter) in the state of non-parallel beam light (P-polarized), and guided to a photodetector 7. Transmission characteristics of a dielectric film formed on an incident surface of the plate 2 are shifted to the side of a short wavelength o 15-20nm as compared with a case designed for parallel beam incident light, thereby compensating an incident angle dependency. |
