| 摘要 |
PROBLEM TO BE SOLVED: To reduce the number of parts and to miniaturize a product by facilitating the assembling of freely eccentric curved surface prism. SOLUTION: An external ridge line L3 formed on both sides of a first optical surface 6a facing with a video display device 4 of the freely eccentric curved surface prism 6 is formed almost linearly, and vertexes P1 and P2 formed at both ends of an external ridge line L are inserted and positioned or held between a front side vertex holding member 12a formed on a front case 3b of a housing 3 and a rear side vertex holding member 15a formed on a rear case 3a. Since the freely eccentric curved surface prism 6 is fixed to the housing 3 by utilizing the external ridge line L3 of the freely eccentric curved surface prism 6 and the vertexes P1 and P2, a positioning part does not have to be provided any more, a shape can be simplified, and various assembling can also be performed.
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