| 摘要 |
<p>An object optical system having interchangeability among three types of disks, a high-density optical disk using a blue-violet laser beam source, a DVD, and a CD, and ensuring light quantity without compromise in spherical aberration, an optical pickup device, and optical information recording/reproducing device. The object optical system comprises a first diffraction structure for giving diffraction actions to light fluxes at wavelengths lambda1-lambda3 so that respective L-order (L; odd number), M-order, N-order (M,N; integers) diffraction lights provide maximum diffraction efficiencies, and a first light path difference affording structure for giving substantially a phase difference to one or two light fluxes out of light fluxes at wavelengths lambda1-lambda3.</p> |
