Imaging optical system

Claim 2

An imaging optical system having a first objective lens movable along the optical axis thereof for focus adjustment and for forming the image of an object at infinity, and a second objective lens for forming said image again at a predetermined position at a predetermined magnification, said second objective lens comprising, in succession from the object side, a positive single lens, a negative single lens and a positive single lens disposed with an air space therebetween, and satisfying the following conditions: 0.05 f<Σd<0.14 f 0.1 f <|r.sub.M |<0.35 f 0.1 f <D<0.11 f where f is the focal length of said second objective lens, Σd is the assembly length of said second objective lens, r M is the radius of curvature of that surface of the lenses constituting said second objective lens which has the greatest positive power, and D is the total of the air spaces between the two positive single lenses and middle negative single lens of said second objective lens.

Claim 3

An imaging optical system according to claim 1, wherein said second objective lens has a numerical aperture of 0.05 or less and a half angle of view of 10° or less.

Claim 4

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 10.5 ENP = 0˜-0.2 f ______________________________________ r1 = 28.7 d1 = 1.5 n1 = 1.744 V1 = 45.0 r2 = 136.2 d2 = 3.83 r3 = -40.29 d3 = 1.0 n2 = 1.6727 V2 = 32.17 r4 = 40.29 d4 = 3.83 r5 = -136.2 d5 = 1.5 n3 = 1.744 V3 = 45.0 r6 = -28.7 Σd = 11.66 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 5

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 10.5 ENP = 0˜-0.3 f ______________________________________ r1 = 29.66 d1 = 1.5 n1 = 1.6223 V1 = 53.05 r2 = 110.45 d2 = 3.9 r3 = -28.39 d3 = 1.0 n2 = 1.57501 V2 = 41.42 r4 = 45.07 d4 = 3.02 r5 = -1023.8 d5 = 1.5 n3 = 1.62041 V3 = 60.14 r6 = -238.56 Σd = 10.92 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 6

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 10.5 ENP = 0˜-0.25 f ______________________________________ r1 = 28.3 d1 = 1.5 n1 = 1.62299 V1 = 58.22 r2 = 119.3 d2 = 2.87 r3 = -17.19 d3 = 1.0 n2 = 1.61266 V2 = 44.41 r4 = 72.28 d4 = 1.18 r5 = -94.2 d5 = 1.5 n3 = 1.62299 V3 = 58.22 r6 = -15.29 Σd = 8.05 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 7

An imaging optical system according to claim 1, further numerical data are as follows: ______________________________________ f = 100 y = 10.5 ENP = 0˜-0.3 f ______________________________________ r1 = 14.05 d1 = 1.5 n1 = 1.51823 V1 = 58.9 r2 = 27.45 d2 = 1.99 r3 = -56.18 d3 = 1.0 n2 = 1.61266 V2 = 44.41 r4 = 18.7 d4 = 1.6 r5 = 46.6 d5 = 1.5 n3 = 1.6228 V3 = 57.03 r6 = -31.9 Σd = 7.59 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 8

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 10.5 ENP = 0˜-0.3 f ______________________________________ r1 = 20.06 d1 = 1.5 n1 = 1.6223 V1 = 53.05 r2 = 40.63 d2 = 4.0 r3 = -32.32 d3 = 1.0 n2 = 1.61266 V2 = 44.41 r4 = 25.09 d4 = 1.51 r5 = 44.46 d5 = 1.5 n3 = 1.51835 V3 = 60.23 r6 = -22.28 Σd = 9.51 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 9

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 10.5 ENP = 0˜-0.2 f ______________________________________ r1 = 34.42 d1 = 1.5 n1 = 1.6228 V1 = 57.03 r2 = -55.11 d2 = 1.97 r3 = -17.53 d3 = 1.0 n2 = 1.61266 V2 = 44.41 r4 = 64.18 d4 = 1.95 r5 = -32.39 d5 = 1.5 n3 = 1.51835 V3 = 60.23 r6 = -13.62 Σd = 7.92 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 10

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 17.5 ENP = 0˜-0.2 f ______________________________________ r1 = 12.02 d1 = 1.5 n1 = 1.51823 V1 = 58.9 r2 = 30.63 d2 = 1.0 r3 = -107.00 d3 = 1.0 n2 = 1.61266 V2 = 44.4 r4 = 14.72 d4 = 2.0 r5 = 58.50 d5 = 1.5 n3 = 1.61728 V3 = 54.0 r6 = -35.68 Σd = 7.0 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 11

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 17.5 ENP = 0˜-0.3 f ______________________________________ r1 = 13.10 d1 = 1.5 n1 = 1.62299 V1 = 58.22 r2 = 50.33 d2 = 0.77 r3 = 391.1 d3 = 1.0 n2 = 1.61266 V2 = 44.41 r4 = 13.22 d4 = 4.0 r5 = 122.10 d5 = 1.5 n3 = 1.62299 V3 = 58.22 r6 = -57.28 Σd = 8.77 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 12

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 17.5 ENP = 0˜-0.3 f ______________________________________ r1 = 15.55 d1 = 1.5 n1 = 1.51823 V1 = 58.9 r2 = ∞ d2 = 1.55 r3 = -63.3 d3 = 1.0 n2 = 1.61266 V2 = 44.4 r4 = 17.85 d4 = 4.5 r5 = ∞ d5 = 1.5 n3 = 1.6228 V3 = 57.03 r6 = -35.44 Σd = 10.05 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 13

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 17.5 ENP = 0˜-0.3 f ______________________________________ r1 = 16.39 d1 = 2.90 n1 = 1.61272 V1 = 58.54 r2 = -980.0 d2 = 1.4 r3 = -69.5 d3 = 0.7 n2 = 1.54814 V2 = 45.87 r4 = 15.28 d4 = 5.54 r5 = ∞ d5 = 1.8 n3 = 1.5168 V3 = 64.1 r6 = -44.64 Σd = 12.34 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 14

An image optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 16 ENP = -0.15 f˜0.15 f ______________________________________ r1 = 12.495 d1 = 1.5 n1 = 1.72342 V1 = 37.88 r2 = 18.957 d2 = 2.85 r3 = -285.7 d3 = 1.0 n2 = 1.6727 V2 = 32.17 r4 = 14.443 d4 = 4.0 r5 = 36.800 d5 = 1.5 n3 = 1.74443 V3 = 49.52 r6 = -60.786 Σd = 10.85 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.

Claim 15

An imaging optical system according to claim 1, wherein numerical data are as follows: ______________________________________ f = 100 y = 11 ENP = -0.2 f˜-0.6 f ______________________________________ r1 = 17.79 d1 = 1.4 n1 = 1.72342 V1 = 37.88 r2 = 22.66 d2 = 1.2 r3 = 93.24 d3 = 0.9 n2 = 1.6727 V2 = 32.17 r4 = 21.20 d4 = 1.5 r5 = 39.60 d5 = 2.0 n3 = 1.74810 V3 = 52.28 r6 = -141.53 Σd = 7.0 ______________________________________ where f represents the focal length, y represents the image height, ENP represents the entrance pupil position from the vertex of the first lens surface (the direction of travel of light is positive), r represents the radius of curvature of each lens surface, d represents the spacing between adjacent lens surfaces, and n and V represent the refractive index and Abbe number, respectively, for d-line.