Imagery lens system

Claim 2

An imagery lens system consisting of first to fourth lens elements which are arranged in this order from the object side, the first and fourth lens elements respectively being double-convex lenses, the second and third lens elements respectively being double-concave lenses, wherein the following formulae are satisfied, 0.35<f1/f<0.51--(1) 0.34<f4/f<0.45--(2) 0.11<d7/f<0.16--(3) 0.29<d/f<0.41--(4) wherein f represents the synthetic focal length of the overall lens system, f1 represents the focal length of the first lens element, f4 represents the focal length of the fourth lens element, d represents the axial surface separation between the object side face of the first lens element and the image side face of the fourth lens element and d7 represents the central thicknesses of the fourth lens element.

Claim 3

An imagery lens system as defined in claim 1 in which a stop is disposed between the third and fourth lens elements.

Claim 4

An imagery lens system as defined in claim 2 wherein the following formulae are further satisfied, 0.29<r1/f<0.45--(5) 0.31<r6</f<0.49--(6) 1.75<n4--(7) 0.48<r6/r7<0.66--(8)

Claim 5

017<d4/f<0.023--(9) 0.017<d6/f<0.025--(10) wherein r1 represents the radius of curvature of the object side face of the first lens element L1, r6 represents the radius of curvature of the image side face of the third lens element L3, r7 represents the radius of curvature of the object side face of the fourth lens element L4, n4 represents the refractive index of the fourth lens element L4, d4 represents the axial surface separation between the image side face of the second lens element L2 and the object side face of the third lens element L3, and d6 represents the axial surface separation between the image side face of the third lens element L3 and the object side face of the fourth lens element L4.

Claim 6

017<d4/f<0.023--(9) 0.017<d6/f<0.025--(10) wherein r1 represents the radius of curvature of the object side face of the first lens element L1, r6 represents the radius of curvature of the image side face of the third lens element L3, r7 represents the radius of curvature of the object side face of the fourth lens element L4, n4 represents the refractive index of the fourth lens element L4, d4 represents the axial surface separation between the image side face of the second lens element L2 and the object side face of the third lens element L3, and d6 represents the axial surface separation between the image side face of the third lens element L3 and the object side face of the fourth lens element L4.

Claim 7

An imagery lens system as defined in claim 3 wherein the following conditions are satisfied, ______________________________________ r1 = 3.8905 d1 = 0.9051 n1 = 1.72250 ν.sub.1 = 49.6 r2 = -41.1837 d2 = 0.3494 r3 = -8.3806 d3 = 0.2548 n2 = 1.64769 ν.sub.2 = 33.9 r4 = 5.1568 d4 = 0.1917 r5 = -8.4793 d5 = 0.2596 n3 = 1.61293 ν.sub.3 = 36.9 r6 = 4.2569 d6 = 0.2257 r7 = 7.2747 d7 = 1.2546 n4 = 1.77250 ν.sub.4 = 49.6 r8 = -4.8949 ______________________________________ f1/f = 0.46422 f4/f = 0.39660 r1/f = 0.38905 r6/f = 0.42569 d7/f = 0.12546 r6/r7 = 0.58517 d/f = 0.34407 d4/f = 0.01917 d6/f = 0.02257 ______________________________________ where the radii of curvature of the refracting surfaces, the axial surface separations, the refractive indexes for the sodium d-line and the Abbe's numbers of the lenses L 1 to L 4 are designated in order from the object side at r1 to r8, d1 to d7, n1 to n4 and ν 1 to ν 4 .

Claim 8

An imagery lens system as defined in claim 3 wherein the following conditions are satisfied, ______________________________________ r1 = 3.9528 d1 = 0.8129 n1 = 1.77250 ν.sub.1 = 49.6 r2 = -30.6199 d2 = 0.3689 r3 = -7.8259 d3 = 0.2621 n2 = 1.61293 ν.sub.2 = 36.9 r4 = 5.6192 d4 = 0.1941 r5 = -8.6329 d5 = 0.2402 n3 = 1.64769 ν.sub.3 = 33.9 r6 = 4.4089 d6 = 0.2184 r7 = 7.6242 d7 = 1.4415 n4 = 1.77250 ν.sub.4 = 49.6 r8 = -4.8499 ______________________________________ f1/f = 0.45788 f4/f = 0.40407 r1/f = 0.39528 r6/f = 0.44089 d7/f = 0.14415 r6/r7 = 0.57828 d/f = 0.35381 d4/f = 0.01941 d6/f = 0.02184 ______________________________________ where the radii of curvature of the refracting surfaces, the axial surface separations, the refractive indexes for the sodium d-line and the Abbe's numbers of the lenses L 1 to L 4 are designated in order from the object side at r1 to r8, d1 to d7, n1 to n4 and ν 1 to ν 4 .

Claim 9

An imagery lens system as defined in claim 3 wherein the following conditions are satisfied, ______________________________________ r1 = 3.9526 d1 = 0.8025 n1 = 1.77250 ν.sub.1 = 49.6 r2 = -31.6014 d2 = 0.3761 r3 = -7.7807 d3 = 0.2669 n2 = 1.61293 ν.sub.2 = 36.9 r4 = 5.1241 d4 = 0.1893 r5 = -8.6922 d5 = 0.2427 n3 = 1.64769 ν.sub.3 = 33.9 r6 = 4.4087 d6 = 0.2184 r7 = 7.5426 d7 = 1.4365 n4 = 1.77250 ν.sub.4 = 49.6 r8 = -4.8380 ______________________________________ f1/f = 0.45930 f4/f = 0.40187 r1/f = 0.39526 r6/f = 0.44087 d7/f = 0.14365 r6/r7 = 0.58451 d/f = 0.35324 d4/f = 0.01893 d6/f = 0.02184 ______________________________________ where the radii of curvature of the refracting surfaces, the axial surface separations, the refractive indexes for the sodium d-line and the Abbe's numbers of the lenses L 1 to L 4 are designated in order from the object side at r1 to r8, d1 to d7, n1 to n4 and ν 1 to ν 4 .

Claim 10

An imagery lens system as defined in claim 3 wherein the following conditions are satisfied, ______________________________________ r1 = 4.0378 d1 = 0.8570 n1 = 1.77250 ν.sub.1 = 49.6 r2 = -21.2397 d2 = 0.2913 r3 = -7.9181 d3 = 0.3666 n2 = 1.60342 ν.sub.2 = 38.0 r4 = 5.3206 d4 = 0.1942 r5 = -7.2449 d5 = 0.2476 n3 = 1.64769 ν.sub.3 = 33.9 r6 = 4.4106 d6 = 0.2185 r7 = 7.7948 d7 = 1.3425 n4 = 1.77250 ν.sub.4 = 49.6 r8 = -4.7650 ______________________________________ f1/f = 0.44579 f4/f = 0.40152 r1/f = 0.40378 r6/f = 0.44106 d7/f = 0.13425 r6/r7 = 0.56584 d/f = 0.35177 d4/f = 0.01942 d6/f = 0.02185 ______________________________________ where the radii of curvature of the refracting surfaces, the axial surface separations, the refractive indexes for the sodium d-line and the Abbe's numbers of the lenses L 1 to L 4 are designated in order from the object side at r1 to r8, d1 to d7, n1 to n4 and ν 1 to ν 4 .

Claim 11

An imagery lens system as defined in claim 3 wherein the following conditions are satisfied, ______________________________________ r1 = 4.0915 d1 = 1.1296 n1 = 1.77250 ν.sub.1 = 9.6 r2 = -18.9252 d2 = 0.2429 r3 = -8.0252 d3 = 0.2551 n2 = 1.60342 ν.sub.2 = 38.0 r4 = 5.4765 d4 = 0.1992 r5 = -7.0022 d5 = 0.2429 n3 = 1.64769 ν.sub.3 = 33.9 r6 = 4.3252 d6 = 0.2186 r7 = 7.6230 d7 = 1.4017 n4 = 1.77250 ν.sub.4 = 49.6 r8 = -4.8432 ______________________________________ f1/f = 0.44502 f4/f = 0.40313 r1/f = 0.40915 r6/f = 0.43252 d7/f = 0.14017 r6/r7 = 0.56379 d/f = 0.36900 d4/f = 0.01992 d6/f = 0.02186 ______________________________________ where the radii of curvature of the refracting surfaces, the axial surface separations, the refractive indexes for the sodium d-line and the Abbe's numbers of the lenses L 1 to L 4 are designated in order from the object side at r1 to r8, d1 to d7, n1 to n4 and ν 1 to ν 4 .

Claim 12

An imagery lens system as defined in claim 3 wherein the following conditions are satisfied, ______________________________________ r1 = 3.7865 d1 = 0.7808 n1 = 1.77250 ν.sub.1 = 49.6 r2 = -21.2008 d2 = 0.2432 r3 = -8.9223 d3 = 0.2627 n2 = 1.51454 ν.sub.2 = 54.6 r4 = 4.8780 d4 = 0.2119 r5 = -6.8486 d5 = 0.2457 n3 = 1.74077 ν.sub.3 = 27.7 r6 = 4.3115 d6 = 0.2189 r7 = 8.0115 d7 = 1.4084 n4 = 1.78500 ν.sub.4 = 43.7 r8 = -4.7646 ______________________________________ f1/f = 0.42162 f4/f = 0.39999 r1/f = 0.37865 r6/f = 0.43115 d7/f = 0.14084 r6/r7 = 0.53816 d/f = 0.33716 d4/f = 0.02119 d6/f = 0.02189 ______________________________________ where the radii of curvature of the refracting surfaces, the axial surface separations, the refractive indexes for the sodium d-line and the Abbe's numbers of the lenses L 1 to L 4 are designated in order from the object side at r1 to r8, d1 to d7, n1 to n4 and ν 1 to ν 4 .

Claim 13

An imagery lens system as defined in claim 3 wherein the following conditions are satisfied, ______________________________________ r1 = 3.2494 d1 = 0.8312 n1 = 1.76883 ν.sub.1 = 50.8 r2 = -39.4459 d2 = 0.1622 r3 = -14.3268 d3 = 0.2425 n2 = 1.58700 ν.sub.2 = 50.7 r4 = 4.1540 d4 = 0.1939 r5 = -8.7490 d5 = 0.2424 n3 = 1.74013 ν.sub.3 = 29.2 r6 = 3.4990 d6 = 0.1939 r7 = 5.8202 d7 = 1.4550 n4 = 1.79999 ν.sub.4 = 43.7 r8 = -5.6145 ______________________________________ f1/f = 0.39406 f4/f = 0.37864 r1/f = 0.32494 r6/f = 0.34990 d7/f = 0.14550 r6/r7 = 0.60118 d/f = 0.33211 d4/f = 0.01939 d6/f = 0.01939 ______________________________________ where the radii of curvature of the refracting surfaces, the axial surface separations, the refractive indexes for the sodium d-line and the Abbe's numbers of the lenses L 1 to L 4 are designated in order from the object side at r1 to r8, d1 to d7, n1 to n4 and ν 1 to ν 4 .