Projection-type video display device
AssigneeHitachi Maxell, Ltd.
InventorMasahiko YATSU
Life of this patent
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Abstract
Provided is a projection-type video display device implementing further reduction of a projection distance and further miniaturization of a projection optical system. The projection-type video display device includes a lens group which includes a plurality of lenses, a free-form-surface lens, and a free-form-surface mirror which projects light from the free-form-surface lens on a screen, wherein the lens group includes a third lens which has a bi-convex shape, a fourth lens which has a bi-concave shape, a fifth lens which has a bi-convex shape, the third to fifth lenses constitute a triplet lens, and wherein the free-form-surface lens has a meniscus lens shape of which a convex surface is oriented toward the magnification side.
Claims5
A projection-type video display device comprising:
- a lens group which is disposed in a light propagation direction with respect to a video display element and includes a plurality of lenses;
- a first free-form-surface lens which is disposed in the light propagation direction with respect to the lens group;
- a second free-form-surface lens which is disposed in the light propagation direction with respect to the first free-form-surface lens;
- and
- a free-form-surface mirror which reflects light emitted from the second free-form-surface lens to project the light on a screen in an inclined manner,
- wherein the lens group includes, in order from a side close to the video display element, a first lens which has positive refractive power and a bi-convex shape of which a small radius of curvature is oriented toward the side close to the video display element, a second lens which has an aspherical shape, a third lens which has positive refractive power and a bi-convex shape, a fourth lens which has negative refractive power and a bi-concave shape, a fifth lens which has positive refractive power and a bi-convex shape, a sixth lens which has positive refractive power and a bi-convex shape of which a small radius of curvature is oriented toward a magnification side, a seventh lens which has negative refractive power and an aspherical meniscus shape of which a convex surface is oriented toward a reduction side, an eighth lens which has negative refractive power and a bi-concave shape, a ninth lens which has positive refractive power and a bi-convex shape of which a small radius of curvature is oriented toward the magnification side, and a tenth lens which has negative refractive power and an aspherical meniscus shape of which a convex surface is oriented toward the magnification side,
- wherein the third, fourth, and fifth lenses constitute a cemented triplet lens, and
- wherein the first and second free-form-surface lenses have a meniscus lens shape of which a convex surface is oriented toward the magnification side.
Dependencies are inferred from the claim text.