| 摘要 |
PURPOSE:To enlarge and reduce a section of a parallel luminous flux, in a state that it is parallel, by only one parts, by forming the first and the second rotary elliptical surfaces so that one focus of the first rotary elliptical body and one focus of the second rotary elliptical body coincide with each other. CONSTITUTION:When a parallel luminous flux D is made incident on the first rotary elliptical surface in parallel to an optical axis, its luminous flux is condensed to one focus F1 of the first rotary elliptical body, by a quality of the first rotary elliptical body. The focus F1 of the first rotary elliptical body is simultaneously one focus F2 of the second rotary elliptical body, therefore, by a quality of the second rotary elliptical body, its luminous flux becomes a parallel luminous flux D' being parallel to the optical axis, when it is radiated from the second rotary elliptical surface. On the contrary, when the parallel luminous flux D' is made incident from the second rotary elliptical surface in parallel to the optical axis, it becomes the parallel luminous flux whose section has been enlarged.
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