| 摘要 |
PURPOSE:To reduce interarray movement and to perform high-speed data access, by arraying pit groups in a radius direction, and allowing a reader to reciprocate in the radius direction to read respective pit groups. CONSTITUTION:Light from a semiconductor laser 40 is passed through a polarization prism 42, quarter-wavelength plate 45, and lens 46 and polarized by the quarter-wavelength plate 45 to illuminate pits (not shown in a figure) of an optical disk. Reflected light from each pit is polarized again through the lens 46 and quarter-wavelength plate 45, and reflected by reflecting surfaces 44 and 43 of the polarization prism 42 to reach a photodetecting element 41. In this state, a piezoelectric element 48 is applied with a signal with a proper period (e.g. Sin3theta) to oscillate, and its oscillation is transmitted to a tuning-fork oscillator 47 to allow the laser 40, photodetecting element 41, polarization prism 42, quarter-wavelength plate 45, lens 46, etc., to reciprocate in the radius direction. Therefore, laser light passed through the lens 46 also reciprocates in the radius direction to scan pit groups one after another, thus reading data. |
