Patent ID: 7404646
Filing Date: 2008-07-29
Classification: G02B,G03B

Abstract:
1. A projection lens apparatus comprising: a plurality of lenses, for enlarging and projecting, onto a screen, an original image displayed on an image generation source; wherein the plurality of lenses are arranged, beginning with the lens nearest the screen, as (a) a first lens group, including a meniscus lens that has a positive refracting power and has a center convex portion directed toward a screen; (b) a second lens group, including a lens that has a positive refracting power and has a center convex lens surface directed toward the image generation source side; (c) a third lens group, including a power lens having a highest positive refracting power; (d) a fourth lens group, including one meniscus lens that has a positive refracting power and has a concave lens surface directed toward the screen; (e) a fifth lens group, including a lens that has a positive refracting power and has a center convex lens surface directed toward the image generation source; and (f) a sixth lens group, including a lens that has a concave lens surface directed toward the screen and has a negative refracting power; wherein the concave lens surface of the meniscus lens included in the fourth group lens has a curvature in the vicinity of an outer portion of the concave lens surface that is smaller than a curvature in a predetermined area of the concave lens surface defined between a light axis of the concave lens surface of the meniscus lens and the smaller curvature of the concave lens surface in the vicinity of the outer portion of the concave lens surface.