| 摘要 |
<p>A first wavelength is used to reproduce data from a first optical disk; and a second wavelength is used to record/reproduce data on/from a second optical disk. Disposed on one side of an objective lens is a phase shifter having annular step the center of which is aligned with the optical axis. The phased shifter has a function of causing a phase difference between the first and second wavelengths. Such an objective lens is used to favorably reproduce data from either of a CD and DVD.</p> |
