Claims Analysis
Total Claims: 8
Claim 1
Independent Claim
71 words
A lens system for a projection type television, comprising, successively from a screen side, a concave first lens, a convex second lens cemented to the first lens, a third lens at least one side of which is aspherical, a bi-convex fourth lens, a concave fifth lens cemented to the fourth lens, a sixth lens at least one side of which is aspherical, and a concave seventh lens having an aspherical surface.
Claim 2
Dependent Claim
71 words
A lens system for a projection type television, comprising, successively from a screen side, a concave first lens, a convex second lens cemented to the first lens, a third lens at least one side of which is aspherical, a bi-convex fourth lens, a concave fifth lens cemented to the fourth lens, a sixth lens at least one side of which is aspherical, and a concave seventh lens having an aspherical surface.
Claim 3
Dependent Claim
44 words
A lens system for a projection type television according to claim 1, wherein Abbe's numbers at d line of the first, second, fourth and fifth lenses are v 1, v2, v4 and v5, respectively, and said Abbe's numbers satisfy the relationship of v1>v2, v4>v5.
Claim 4
Dependent Claim
32 words
A lens system for a projection type television according to claim 2, wherein v5<37.0, the refractive index at 545 nm of the fifth lens is N 5 , and N 5 ≧1.62.
Claim 5
Dependent Claim
70 words
A lens system for a projection type television according to claim 1, wherein the radius of curvature of the cemented surface between the first and the second lens is R 2 , the radius of curvature of the cemented surface between the fourth and the fifth lens is R 7 and the focal length of the entire system is f, wherein the following conditions are satisfied: 1.5<R.sub.2 /f<2.5 0.5<R.sub.7 /f<1.0.
Claim 6
Dependent Claim
49 words
A lens system for a projection type television according to claim 1, wherein the spacing between the third and the fourth lens is T 34 and the spacing between the sixth and the seventh lens is T 67 , and the following conditions are satisfied: 0.2<T.sub.34 /f<0.3 0.2<T.sub.67 /f<0.4.
Claim 7
Dependent Claim
124 words
A lens system for a projection type television according to claim 1, wherein an asphericity degree A 3 of the third lens and A 6 of the sixth lens satisfy the following conditions: -0.06<A.sub.3 /f<-0.01 -0.07<A.sub.6 /f<-0.04 where a surface shape Z(r) at a distance r from an optical axis is defined as follows: ##EQU4## and using R D in the above equation, S(r) is defined as follows: ##EQU5## and with Z(r), S(r) and aperture radius on the lens screenside surface being Z 1 (r), S 1 (r) and r 1 , respectively, and those on the electron gun-side surface being Z 2 (r), S 2 (r) and r 2 , respectively, the asphericity degree A is defined as: A={Z.sub.1 (r.sub.1)-S.sub.1 (r.sub.1)}-{Z.sub.2 (r.sub.2)-S.sub.2 (r.sub.2)}.
Claim 8
Dependent Claim
42 words
A lens system for a projection type television according to claim 6, wherein an asphericity amount B 6 at the electron gun-side surface of the sixth lens satisfies the following condition: -1/6<B.sub.6 <-1.0 the asphericity amount B being defined as follows ##EQU6##