| 摘要 |
<P>PROBLEM TO BE SOLVED: To optimize wave front aberration with respect to three kinds of optical disks of different standard. <P>SOLUTION: The optical element has a first electrode layer 21 in which an electrode 21a and an electrode 21b are alternately arranged in a ring shape and a second electrode layer 25 in which an electrode 25a and an electrode 25b are alternately arranged in a ring shape. An ITO27 of low electric resistance and a gap 28 of high electric resistance are provided between the electrodes 21a and 21b or between the electrodes 25a and 25b. An electrode interval in the first electrode layer 21 is set to a pitch so that the wave front aberration can be optimized with respect to a light source of a long wavelength, while an electrode interval in the second electrode layer 25 is set to a pitch so that the wave front aberration can be optimized with respect to a light source of a medium wavelength. When a light flux of long wavelength or medium wavelength is incident on the optical element 10, potentials of the electrodes 21a, 21b, 25a, and 25b are changed and a prescribed diffraction element is formed to optimize the wave front aberration; when the light flux of short wavelength is incident on the optical element 10, potentials of the electrodes 21a, 21b, 25a, and 25b are uniformed to equalize electric field intensity of a liquid crystal layer and the optical element 10 is transmitted. <P>COPYRIGHT: (C)2007,JPO&INPIT |
