Photographic lens having ghost image prevented from appearing

Claim 2

A zoom lens comprising: from front to rear, a first lens unit having a positive refractive power; a second lens unit for variation of the image magnification having a negative refractive power; a third lens unit for compensating for the shift of an image plane resulting from the variation of the image magnification; a fourth lens unit; a fifth lens unit having a positive refractive power and hving an image forming function, wherein the following condition is satisfied: 1.05<f.sub.4 /L<1.3 where L is the absolute value of a distance from a point of convergence of an on-axial light beam which has passed said first lens unit through said third lens unit to a front principal point of said fourth lens unit, and f 4 is a focal length of said fourth lens unit.

Claim 3

A zoom lens according to claim 1, further comprising an aperture stop positioned in between said fourth lens unit and said fifth lens unit.

Claim 4

A zoom lens according to claim 1, wherein said fifth lens unit includes, from front to rear, a first bi-convex lens, a second lens having a negative refractive power and having a concave surface facing the object side, a third bi-convex lens having a refracting surface of stronger curvature facing the object side, a fourth lens having a negative refractive power and having a concave surface facing the image plane side, a fifth bi-convex lens having a refracting surface of stronger curvature facing the image plane side, and a sixth bi-convex lens having a refracting surface of stronger curvature facing the object side.

Claim 5

A zoom lens according to claim 3, wherein said first lens unit includes a first meniscus lens having a negative refractive power and having a convex surface facing the object side, a second bi-convex lens, and a third meniscus lens having a positive refractive power and having a convex surface facing the object side, said second lens unit includes a first lens having a negative refractive power, a second bi-concave lens, and a third lens having a positive refractive power, said second lens and said third lens being cemented together, and the following conditions are satisfied: 1.57<N1,2+N1,3/2 0.96<|f2/fw|<1.09,f2<0 1.18<R2,2/fw<1.35 0.77<|R2,2/R2,3|<0.87 where Ni, j is the refractive index of a medium of the j-th lens in the i-th lens unit, Ri, j is the radius of curvature of the j-th lens surface in the i-th lens unit, and fw is the shortest focal length of the entire lens system.

Claim 6

A zoom lens according to claim 3, satisfying the following conditions: 27.8<|R5,4/fw|<38.5 -0.041<fw/R5,7<0.034 1.73<N5,2+N5,4/2 where Ni, j is the refractive index of a medium of the j-th lens in the i-th lens unit, Ri, j is the radius of curvature of the j-th lens in the i-th lens unit, and fw is the shortest focal length of the entire lens system.

Claim 7

A zoom lens according to claim 5, satisfying the following condition: -1.97<R5,1/R5,3<-1.28 2.22<R5,5/fw<2.69 1.35<R5,8/fw<1.55 3.36<R5,9/R5,11<4.62 0.15<D5,2/fw<0.24 1.28<D5,6/fw<1.53 0.11<D5,8/fw<0.15 where Di, j is the j-th lens thickness or air separation in the i-th lens unit.

Claim 8

A zoom lens unit according to claim 2, further comprising filter means disposed adjacent to said aperture stop.