| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a diffraction optical element for maintaining high diffraction efficiency even when a distribution of diffraction index occurs in a grid of the diffraction optical element. <P>SOLUTION: The diffraction optical element is the diffraction optical element used for an optical system by having a first diffraction grid composed of a first material of a first diffraction index and a first dispersion, and a second diffraction grid composed of a second material of a second diffraction index which is higher than the first diffraction index and a second dispersion which is lower than the first dispersion adhered or come into close proximity. In this case, at least one of the first diffraction grid or the second diffraction grid has distribution of diffraction index and is provided with a diffraction surface including a grid surface which is arranged at a prescribed pitch, having a prescribed inclination and a grid wall surface of a prescribed height. The grid surface has a shape making the height of the grid wall surface lower by reducing the inclination of the grid surface with the greater diffraction index distribution among the first diffraction grid and the second diffraction grid for the shape to which a phase difference is added based on a phase difference function for correcting an aberration of the optical system to the shape of a base surface forming at least one of the first diffraction grid or the second diffraction grid. <P>COPYRIGHT: (C)2012,JPO&INPIT |
