| 摘要 |
This invention is directed to an optical pickup apparatus, condensing optical system, and optical element which can at least reproduce and/or record information from/on a first optical information recording medium having a protective substrate thickness t 1 by using a light beam of a first wavelength lambda 1 emitted from a first light source, and reproduce and/or record information from/on a second optical information recording medium having a protective substrate thickness t 2 (t 2 >=t 1 ) by using a light beam of a second wavelength lambda 2 (lambda 2>lambda1 ) emitted from a second light source. The optical pickup apparatus of the invention includes a first phase modulator which gives a diffraction effect to only the light beam of the wavelength lambda 1 on at least one optical surface, of a plurality of optical surfaces of a plurality of optical elements arranged on a common optical path through which the light beam of the first wavelength lambda 1 and the light beam of the second wavelength lambda 2 pass, and a second phase modulator which gives a diffraction effect to only the light beam of the wavelength lambda 2 on at least one of the remaining optical surfaces. Each of the first phase modulator and second phase modulator has staircase-like discontinuous parts, each formed from a predetermined number of stepped portions, formed concentrically around an optical axis at the pitch defined by an optical path difference function.
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