| 摘要 |
<P>PROBLEM TO BE SOLVED: To prevent reduction of diffraction efficiency of a diffraction grating part when a reflection preventing film is deposited on the diffraction grating part formed stepwise on an optical substrate of a multistage diffraction optical element. <P>SOLUTION: The multistage diffraction optical element 10B is characterized in that when the reflection preventing film 13 is deposited on the diffraction grating part 11d formed stepwise on the optical substrate 11 of the multistage diffraction optical element 10B, before the reflection preventing film 13 is deposited on the optical substrate 11, a step width wb1 of a step part recessed in a recessed shape as compared with the right and left step parts adjacent thereto is formed more widely than step widths of the right and left step parts by the width corresponding to the film thickness of the reflection preventing film 13 to be deposited on the respective wall surfaces of the right and left step parts adjacent to the step part and a step width wb8 of a step part projecting in a projecting shape as compared with the right and left step parts adjacent thereto is formed more narrowly than step widths of the right and left step parts by the width corresponding to the film thickness of the reflection preventing film 13 to be deposited on respective wall surfaces of the right and left step parts. <P>COPYRIGHT: (C)2008,JPO&INPIT |
