| 摘要 |
<P>PROBLEM TO BE SOLVED: To realize interchangeability of a BD or a HD DVD and a DVD and a CD by one objective lens in a condensing optical system concurrently having an objective lens using a diffraction grating. <P>SOLUTION: In the condensing optical system 1, a light for recording and/or reproducing a plurality of optical recording media of different kinds is converged on this optical recording medium, by using a diffraction element 2 and a lens 3, wherein the diffraction element 2 has at least first and second diffraction planes 11 and 12; the first diffraction plane 11 diffracts a light of wavelength 630-670 nm and aberration compensation is performed for an optical recording medium in which the thickness of a cover part 100A is approximately 0.6 mm; the second diffraction plane 12 diffracts light of wavelength 400-415 nm; and aberration compensation is performed for the optical recording medium 10A, in which the thickness of a cover part is approximately 0.1 mm or approximately 0.6 mm. <P>COPYRIGHT: (C)2006,JPO&NCIPI |
