| 摘要 |
PROBLEM TO BE SOLVED: To obtain a projection type optical device which is easily manufactured by drastically shortening the optical depth of a projection optical unit and shortening height at the lower part of a screen in a projection type color video display device or a back projection type color video display device. SOLUTION: A projection lens including a plurality of lenses for enlarging a video from a video display element (1) is constituted of a front group (2) and a rear group (3). The rear group (3) includes at least one free curved surface lens having a rotationally asymmetric shaped surface. Furthermore, the device includes at least one free curved surface mirror (4) having a rotationally asymmetric reflection surface. Thus, the set is made compact while correcting trapezoidal distortion and aberration. COPYRIGHT: (C)2007,JPO&INPIT
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