| 摘要 |
A projection optical unit for obliquely projecting an image displayed on an image display element upon a projection surface, enlargedly, comprises: a lens group, being disposed neighboring to the image display element, and including a plural number of projection lenses therein; and a reflection mirror for reflecting lights emitting from the lens group, to be projected onto the projection surface, obliquely, wherein assuming that a light beam, emitting from a center of the display screen of the image display element, passing through a center of an entrance pupil of the lens group, and entering into a screen center on the projection surface, is a screen center light beam, then the screen center light beam is incident upon the projection surface, obliquely, with respect to a normal line thereon, the lens group comprises a front lens group including a plural number of refraction lenses, being disposed thereafter directing from the image display element to the projection surface and having rotationally symmetric surface configurations, and a rear lens group including a refraction lens having a negative power and having a rotationally symmetric surface configuration and a plural number of lenses having rotationally asymmetric free curved surface configurations, and within the rear lens group, the lens having the negative power is movable in an optical axis direction, and at least one pieces among the lenses having the free curved surface configurations is movable into directions, including the optical axis and direction perpendicular thereto, within a surface including the optical axis and the normal line on the screen.
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