| 摘要 |
PURPOSE:To eliminate a relative positional shift between two light spots in the direction orthogonal to a track and to secure the stable irradiation with a double laser beam head, by enlarging an oval light beam radiated from a semiconductor laser in the track direction and shaping the enlarged beam into an approximately circular from. CONSTITUTION:A light beam 2 radiated from a semiconductor laser 1 is turned into parallel beams through a condenser lens 3 and refracted as soon as it passes through an enlargement face 5 of a prism 4 by P polarization. Then the diameter of the refracted beam is increased in the track direction and shaped into an approximately circular form. Therefore the optical axis is totally reflected by a reflecting face 8 of a prism 7 and reaches a wavelength selection filter 9, an optical path changing triangular prism 10, a 1/4 wavelength plate 11 and an aperture lens 12. Thus a light spot 14 has a shift in the track direction on a disk 13 even though the optical axis of the beam 2 has a shift. So is with a light beam 27 which is radiated from a semiconductor laser 26 and shaped into an approximately circular form. Then no tracking error is produced. |
