| 摘要 |
A reflection mirror includes a main reflection portion including a region close to a main optical axis of the reflection mirror, and circumferential wall portions surrounding the main reflection portion. An inner surface of the circumferential wall portions of the reflection mirror is formed into an inclined surface with respect to the main optical axis of the reflection mirror, and such an inclined surface is made to be smoothly continuous to an inner surface of the main reflection portion to thereby form a fundamental surface of a reflection surface. Then, a group of paraboloids of revolution consisting of many paraboloids of revolution whose focal distances are different from one another is prepared. Then, intersecting lines between the fundamental subrace of the reflection surface and the group of paraboloids of revolution are obtained. Further, many reflection steps are formed on the main reflection portion and the circumferential wall portion. The reflection steps are defined by portions of the respective paraboloids of revolution constituting the group of paraboloids of revolution and are disposed between adjacent ones of the intersecting lines. |
