| 摘要 |
PURPOSE:To miniaturize and simplify a device by providing a wavelength converting element with a smaller diameter than an infrared beam for converting the infrared beam into an ultraviolet beam in a light path between an infrared laser source and an objective lens. CONSTITUTION:A beam of light emitted from an infrared and visible LD array 5 is reflected by a polarized beam splitter (PBS) 7 via a collimator lens 6 and condensed on an optical disk 2 with a photochromic film via a lambda/4 plate 8 and the objective lens. Its reflected light retrogrades to transmit the PBS 7, and its infrared radiation is reflected by a lambda/4 plate 11 and a dichroic mirror DM 12, while its visible radiation is transmitted to be bisect by a biprism 13, so as to be incident upon bisect light detectors 14a and 14b. By this differential output, a focus error signal is obtained. On the other hand, a beam of light from an infrared LD 21 is converted by the wavelength converting element 24 into the ultraviolet beam via a lens 22 and a shaping prism 23. The ultraviolet beam and peripheral infrared beam are reflected by the DM 12 via the lambda/4 plate 11, retrograding to the incident upon the disk 2 via the PBS 7, the lambda/4 plate 8 and the lens 9, so that a bit of information is recorded. |
