Projection optical system and projection unit for oblique projection type projection display device, and oblique projection type projection display device

摘要

An optical position of a display device with respect to an optical axis of a projection optical system is displaced in a direction perpendicular to the optical axis in accordance with a change in the size of a projected image. For instance, a transparent flat plate is disposed in front of a projection lens, and the transparent flat plate is tilted in association with a rotation of a zoom adjustment ring. As the transparent flat plate is tilted, the apparent position of the display device relative to the projection lens is displaced in the direction perpendicular to the optical axis of the projection optical system. Thereby, the projected image on a screen is located at a proper position corresponding to a zoom state. Tilt control of the transparent flat plate is realized by a cam mechanism, for instance.