Oblique projection optical system and projection type display apparatus using the same
AssigneeHitachi Maxell, Ltd.
InventorsKoji Hirata, Masahiko Yatsu, Naoyuki Ogura
Life of this patent
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Abstract
A projection type display apparatus including an oblique projection optical system having a plurality of lenses is disclosed. A lens nearest to a projection screen has a vertical effective image area through which a light flux passes. The lens is arranged at a position not including an optical axis shared by the largest number of lenses among the plurality of lenses. A flat mirror for returning the optical path is arranged between the particular lens and the projection screen at a predetermined angle to the optical axis. An enlarged image obtained by the light flux returned by the flat mirror is formed toward a display screen.
Claims15
A projection type display apparatus comprising:
- a group of lenses consisting of a plurality of lenses for enlarging an image displayed on a display screen of a display device and projecting an enlarged image on a projection screen,
- wherein the group of lenses comprises a first lens arranged at a position optically nearest to the projection screen,
- wherein the first lens has an effective image area through which a light flux of the image is passed and has such a shape that a portion which does not include the effective image area is truncated, and
- wherein, a height (shift amount) of a position of the displayed enlarged image with respect to an optical axis shared by the plurality of lenses in the vertical direction of the projection screen is increased;
- and
- a mirror for reflecting an optical path arranged between the first lens and the projection screen,
- wherein an upper end of a vertical effective image area of the first lens is located above a lower end of a vertical effective image area of the mirror,
- wherein the mirror has a predetermined angle of elevation with respect to the optical axis, and
- wherein the mirror is provided with a mirror moving mechanism adaptable to move the mirror along the optical axis.
Dependencies are inferred from the claim text.