Image-forming lens system

Claim 2

An image-forming lens system for forming an image by a microscopic objective of infinite distance design, comprising: a lens group consisting of a first lens component together with a second lens component and having a positive refractive power, and a third lens component having a negative refractive power, said lens system having a positive power as a whole and satisfying the following conditions: (1) 0.8<f 12 /|f 3 |<1.4 (2) 1<100d 4 /f<10 (3) 10<r 6 /(n 3 -1)<30 (4) r 6 <|r 4 | (5) 0.4<f 1 /|f 3 |<2.0 wherein the reference symbol f represents the focal length of the entire system, the reference symbol f 1 represents the focal length of said first lens component, the reference symbol f 12 represents the focal length of the lens group, the reference symbol f 3 represents the focal length of the third lens component, the reference symbol r 4 represents the radius of curvature of the surface on the image side of the second lens component, the reference symbol r 6 represents the radius of curvature of the surface on the image side of the third lens component, the reference symbol d 4 represents the airspace between the second and third lens components, and the reference symbol n 3 represents the refractive index of the lens nearest the image side of the third lens component.

Claim 3

An image-forming lens system according to claim 1 wherein said first lens component is a positive lens, said second lens component is a negative lens and said third lens component is a single lens.

Claim 4

An image-forming lens system according to claim 2 having the following numerical data: ______________________________________ f = 100 r.sub.1 = 16.398 d.sub.1 = 2.22 n.sub.1 = 1.488 ν.sub.1 = 70.2 r.sub.2 = -68.186 d.sub.2 = 1.11 r.sub.3 = -31.942 d.sub.3 = 1.11 n.sub.2 = 1.740 ν.sub.2 = 28.3 r.sub.4 = -67.900 d.sub.4 = 8.33 r.sub.5 = 24.407 d.sub.5 = 1.00 n.sub.3 = 1.488 ν.sub.3 = 70.2 r.sub.6 = 10.912 ______________________________________ Object Position ∞, Pupil Position -51.7, Image Position 66.1 wherein the reference symbols r 1 through r 6 represent the radii of curvature on the surfaces of the respective lenses, the reference symbols d 1 through d 5 represent the thicknesses of the respective lenses and airspaces therebetween, the reference symbols n 1 through n 3 represent the refractive indices of the respective lenses, and the reference symbols ν 1 through ν 3 represent the Abbe's numbers of the respective lenses.

Claim 5

An image-forming lens system according to claim 1 wherein said first lens component is a positive lens, said second lens component consists of a positive lens element and a negative lens element cemented to said positive lens element, and said third lens component is a single lens.

Claim 6

An image-forming lens system according to claim 4 having the followng numerical data: ______________________________________ f = 100 r.sub.1 = -1010.977 d.sub.1 = 1.39 n.sub.1 = 1.639 ν.sub.1 = 55.4 r.sub.2 = -29.922 d.sub.2 = 0.28 r.sub.3 = 9.319 d.sub.3 = 2.50 n.sub.2 = 1.639 ν.sub.2 = 55.4 r.sub.3 ' = -15.701 d.sub.3 ' = 0.89 n.sub.2 ' = 1.596 ν.sub.2 ' = 39.2 r.sub.4 = 19.347 d.sub.4 = 1.33 r.sub.5 = -56.805 d.sub.5 = 1.55 n.sub.3 = 1.589 ν.sub.3 = 53.2 r.sub.6 = 7.979 ______________________________________ Object Position ∞, Pupil Position -50.8, Image Position 66.2 wherein the reference symbols r 1 through r 6 represent the radii of curvature on the surfaces of the respective lenses, the reference symbols d 1 through d 5 represent the thicknesses of the respective lenses and airspaces therebetween, the reference symbols n 1 through n 3 represent the refractive indices of the respective lenses, and the reference symbols ν 1 through ν 3 represent the Abbe's numbers of the respective lenses.

Claim 7

An image-forming lens system according to claim 1 wherein said first lens component is a positive lens, said second lens component consists of a first positive lens element and a first negative lens element cemented to said first positive lens element, and said third lens component consists of a second positive lens element and a second negative lens element cemented to said second positive lens element.

Claim 8

An image-forming lens system according to claim 6 having the following numerical data: ______________________________________ f = 100 r.sub.1 = 23.702 d.sub.1 = 2.08 n.sub.1 = 1.603 ν.sub.1 = 60.7 r.sub.2 = -125.711 d.sub.2 = 0.35 r.sub.3 = 16.565 d.sub.3 = 3.47 n.sub.2 = 1.603 ν.sub.2 = 60.7 r.sub.3 ' = -16.665 d.sub.3 ' = 0.69 n.sub.2 ' = 1.626 ν.sub.2 ' = 35.7 r.sub.4 = 20.226 d.sub.4 = 1.39 r.sub.5 ' = -212.052 d.sub.5 ' = 2.78 n.sub.3 ' = 1.596 ν.sub.3 ' = 39.2 r.sub.5 = -12.972 d.sub.5 = 1.25 n.sub.3 = 1.548 ν.sub.3 = 62.8 r.sub.6 = 11.706 ______________________________________ Object Position ∞, Pupil Position -40.3, Image Position 63.7 wherein the reference symbols r 1 through r 6 represent the radii of curvature on the surfaces of the respective lenses, the reference symbols d 1 through d 5 represent the thicknesses of the respective lenses and airspaces therebetween, the reference symbols n 1 through n 3 represent the refractive indices of the respective lenses, and the reference symbols ν 1 through ν 3 represent the Abbe's numbers of the respective lenses.

Claim 9

An image-forming lens system according to claim 1 wherein said first lens component is a positive lens, said second lens component consists of a first positive lens element and a first negative lens element cemented to said first positive lens element, and said third lens component consists of a second positive lens element and a second negative lens element separated from said second positive lens element.