Nittoh Kogaku K.k.

Infocus Corporation

Akira Yamagishi

Jeffrey Alan Gohman

An optical system that projects projection light from an image generating device, onto a screen is provided. The optical system comprises: a lens system on which the projection light from the image generating device is incident; and an aspherical mirror with negative power as a whole that is disposed on an optical path between the lens system and the screen, wherein a curvature of the aspherical mirror in the radial direction changes positive to negative on a way from a center to a periphery thereof.

Optical system and rear projector

A projection lens system that projects projection light from a light modulator onto a screen and which is telecentric on an input side is provided. The projection lens system comprises a first meniscus lens that is disposed closest to the screen, is convex on a screen side, and has negative refractive power; and a second meniscus lens that is disposed next closest to the screen, is convex on a screen side, and has negative refractive power. The first meniscus lens is made of plastic and at least one out of two curved surfaces thereof is aspherical, and a refractive power of the first meniscus lens is lower than a refractive power of the second meniscus lens. In the projection lens system, far superior aberration-correcting performance can be achieved and a drop in aberration-correcting performance due to thermal deformation can be prevented.

Projection lens system and projector

A projection zoom lens system of the present invention having telecentric incident side is suitable for a projector apparatus using LCD or DMD with prism. The projection zoom lens system of this invention comprises five lens groups having, from the screen side, negative, positive, positive, negative and positive power. In addition to this arrangement, since the lens located closest to the screen is a screen side convex negative meniscus lens, wide-angled and bright zoom lens system can be realized. Further, by designing the distribution of power of the first lens group located closest to the screen, the projection zoom lens provides further improved aberration correction. As the condition for realizing the aforementioned projection zoom lens system, it is preferable that a focal length f1 of the first lens group and a focal length at a wide-angle end fw satisfy the following condition:

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Suwa, Japan

Akira Yamagishi