| 摘要 |
<p>In an objective lens for use in an optical pickup device, when NA1 and N2 (NA2 < NA1) represent a needed numerical aperture of the objective lens on an image side, a first spot and a second spot represent a spot formed by the light flux having passed through the central region, a mth order diffracted ray and a nth diffracted ray represent a diffracted ray having the maximum diffraction efficiency among diffracted rays, the central region nearly corresponds to a region through which the light flux in the inside of the numerical aperture NA2 passes, the light amount of the nth order diffracted ray which reaches the inside of the second spot is less than that of the mth order diffracted ray which reaches the inside of the first spot, and the mth order diffracted ray and the nth order diffracted ray satisfy the relationship of m = n.</p> |
