| 摘要 |
PROBLEM TO BE SOLVED: To provide a Fresnel optical element that can avoid a situation in which the light rays which not pass through a refractive surface but are reflected thereby exit as unwanted light, to the visual filed direction of an observer. SOLUTION: The projection display device is arranged, such that an angleτ' of a non-incident surface 12c in a refractive surface 12a of a Fresnel prism 12 to a reflective surface 12b, is different from a forward-end angleτof the prism, the non-incident surface 12c being the surface to which light rays from a projector 1 are not directly radiated, by being intercepted by other Fresnel prisms 12. According to the arrangement, a situation where the light rays which do not pass through the refractive surface 12a but are reflected thereby exit, as unwanted light to the visual field direction of the observer, can be avoided. COPYRIGHT: (C)2011,JPO&INPIT
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