| 摘要 |
A projection optical system includes a first optical element that orients an axis [1 1 1] as a crystal orientation in a cubic system crystal parallel to an optical axis, and a second optical element that orients an axis [1 0 0] as the crystal orientation in the cubic system crystal so that a minimum angle may be 30° or larger between the optical axis and an off-axis edge beam that passes through the second optical element, and a minimum angle may be 10° or smaller between the optical axis and an off-axis principal ray that passes through the second optical element.
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