| 摘要 |
PURPOSE:To improve pickup performance seeking a pit on an optical disk by inserting a nonlinear optical material between a prism and a photodiode of a reflecting light receiving system. CONSTITUTION:A linearly polarized light emitted from a semiconductor laser 11 becomes a collimated beam by a collimeter lens 12 and the light is converted from the linearly polarized light into the circularly polarized light by a half prism 14 and focused on the reflecting face of the optical disk 16 by the condenser lens 16. Then the reflected light reflected in the optical disk 16 is converted into a linearly polarized light by a half prism 14 and shaped by a light receiving lens 17 and a cylindrical lens 18 and made incident on a potassium niobate crystal 20 being a nonlinear optical material. Then the optical intensity proportional to the square of the light intensity of an incident fundamental wave is obtained from a 2nd harmonic wave radiated from the potassium niobate crystal 20. Thus, the pickup performance seeking a prescribed pit on the optical disk is increased in the order of one digit more than that of a conventional pickup. |
