| 摘要 |
<p>An optical pickup device comprising first and second light sources for emitting beams of light of wavelengths μ1, μ2, a focusing optical system, and an optical sensor for recording/reproducing information about optical information recording media of at least two types, wherein a first optical information recording medium has a necessary numeric aperture larger than that of a second optical information recording medium, the focusing optical system splits a beam of light into k (k⊃4) annular beams, the first and k-th beams of the first-wavelength beam are focused onto the information recording surface of the first optical information recording medium, at least two beams out of the second to (k-1)-th beams of the first-wavelength beam have the apparent best image plane position different of that of the first and (k-th beams, and the optical pickup device has an optical element so formed that the wave aberrations of the light in the first to k-th beams of the first-wavelength beam passing through the necessary numerical aperture of the first optical information recording medium are generally integral multiples of μ1 in the best image plane position of the first and k-th beams.</p> |
