| 摘要 |
A luminous flux, from one conjugate surface (A), having an opening angle of at least 10° sequentially passes through a first optical system ( 30 ) having a luminous flux convergent action in the vicinity of its reference axis and a second optical system ( 31 ) having a luminous flux divergent action in the vicinity of its reference axis, and converges on another conjugate surface (B). A specific condition is given to the converging distance of each converging point at a luminous flux section including a principal ray according to the passing position of the luminous flux through the first optical system ( 30 ) to thereby implement an oblique-incident optical system having a half angle of at least 60° and a comparatively simple structure irrespective of a type of an optical element used.
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