| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens for an optical pickup device and an optical pickup device each having a simple structure with which the recording or the reproduction of information is properly performed on a different optical information recording medium, and to provide a method for recording and reproducing information. <P>SOLUTION: The transmissivity of a luminous flux having a wavelength λ<SB>2</SB>for a CD(compact disk) is lower than the transmissivity of a wavelength λ<SB>1</SB>for a DVD(digital versatile disk) thus reflection light from the CD is hardly detected with an optical detector 106 which detects the reflected light from the CD, thus the possibility of an erroneous detection is suppressed even when the overflare part of the luminous flux used for recording or reproducing information on the CD is directed to the under direction due to the enhancement of the wavelength-dependency of a diffraction structure and accordingly the flare part approaches an optical axis. <P>COPYRIGHT: (C)2007,JPO&INPIT |
