| 摘要 |
<p>Provided is an optical element with improved diffraction efficiency, and an optical head device using the same. This optical element has a diffraction structure which, in one period, has multiple steps formed on an optical surface in concentric circles around an optical axis. In one period of the diffraction structure are provided stepped surfaces formed such that the surfaces do not face the optical axis, and a side wall surface formed such that the surface faces the optical axis. The stepped surfaces are inclined relative to the optical axis and a plane perpendicular to the optical axis. A connecting part connecting the side wall surface and the stepped surface adjacent to the outside of said side wall surface is formed into a substantially curved surface having a radius of curvature R [mum], and fulfills the condition 0.2 @ R @ 0.0135×(sqrt(f)-1) (wherein f is the focus distance [mm] of the optical element).</p> |
