| 摘要 |
An optical element (10) includes a spherical aberration correction hologram (14) and a color aberration correction hologram (15). For a first laser light requiring the greatest valid diameter, no affect is given to the wave front in either of the aberration correction holograms. However, for a second laser light requiring the second greatest valid diameter, the valid diameter is narrowed down by the spherical aberration correction hologram (14). For a third laser light requiring the smallest valid diameter, the valid diameter is narrowed down to a predetermined amount by the diffusion light coming and the spherical aberration correction hologram (14) and further the valid diameter is narrowed down by the selective diffraction of the light flux incident in the annular area B of the color aberration correction hologram (15) and its diffusion.
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