| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide an objective lens which can be shared in optical information recording apparatuses that switchably use laser beams with a plurality of wavelengths, and which secures the amount of transmitted light using an anti-reflection film with a small number of layers. <P>SOLUTION: The objective lens focuses laser beams with a plurality of wavelengths on respective corresponding optical information recording media in an information recording and reproducing apparatus that records and/or reproduces information. When the smallest wavelength is represented by λA and the largest wavelength is represented by λB among the plurality of wavelengths, a first anti-reflection film has a minimum value of a reflection rate with respect to light vertically incident on an optical axis, within a wavelength range between λA and λA+20% and within a wavelength range between λB and λB+20%, and a second anti-reflection film has a minimum value of a reflection rate with respect to the light vertically incident on the optical axis, within a wavelength range between λA and λA+20% and within a wavelength range of λB±20%. <P>COPYRIGHT: (C)2009,JPO&INPIT |
