Behind aperture lens system

Claim 2

A compact, five-element, high-performance behind aperture lens comprising a positive meniscus first lens, a negative second lens, a positive third lens, a biconcave negative fourth lens, and a biconvex positive fifth lens, said lenses being arranged in the order from the object side, said behind aperture lens system satisfying the following conditions: (1) 1.15<f/f 1 ,2 -1.55 (2) 1.600<(ν 1 -ν 2 )/(ν 1 /n 1 -ν 2 /n 2 ) (3) 1.200<f/n 4 |f 7 ,8 |<1.450,f 7 ,8 <0 (4) 2.10<f/f 1 <3.00 (5) 0.90<f 5 /|f 4 |<1.50,f 4 <0 (6) 0.60<f 10 /f 7 |<0.80,f 7 <0 (7) 1.00<f 9 /|f 8 |<1.30,f 8 <0 where f: combined focal length of the overall lens system, f 1 ,2 : focal length of the first lens, ν i : Abbe number of the ith lens, n i : refractive index of the ith lens with respect to d-line, f 7 ,8 : focal length of the fourth lens, f 1 : focal length of the first lens on its surface on the object side, f 4 : focal length of the second lens on its surface on the image side, f 5 : focal length of the third lens on its surface on the object side, f 7 : focal length of the fourth lens on its surface on the object side, f 8 : focal length of the fourth lens on its surface on the image side, f 9 : focal length of the fifth lens on its surface on the object side, and f 10 : focal length of the fifth lens on its surface on the image side.

Claim 3

The lens system according to claim 1 satisfying the following conditions: (1) 1.24<f/f 1 ,2 <1.44 (2) 1.600<(ν 1 -ν 2 )/(ν 1 /n 1 -ν 2 /n 2 ) (3) 1.310<f/n 4 |f 7 ,8 |<1.390,f 7 ,8 <0 (4) 2.28<f/f 1 <2.90 (5) 1.10<f 5 /|f 4 |<1.35,f 4 <0 (6) 0.68<f 10 /|f 7 |<0.73,f 7 <0 (7) 1.08<f 9 /|f 8 |<1.20,f 8 <0.

Claim 4

The lens system according to claim 2 further satisfying the following chart: ______________________________________ f = 100 F number 1: 2.9 Angle of view 2ω = 62.0° ______________________________________ r.sub.1 29.611 d.sub.1 9.042 n.sub.1 1.73400 ν.sub.1 51.5 r.sub.2 57.934 d.sub.2 2.301 r.sub.3 167.541 d.sub.3 2.262 n.sub.2 1.66446 ν.sub.2 35.7 r.sub.4 24.584 d.sub.4 1.788 r.sub.5 33.675 d.sub.5 5.251 n.sub.3 1.77250 ν.sub.3 49.7 r.sub.6 129.514 d.sub.6 2.158 r.sub.7 -84.421 d.sub.7 2.121 n.sub.4 1.60562 ν.sub.4 43.7 r.sub.8 43.782 d.sub.8 1.044 r.sub.9 66.609 d.sub.9 9.646 n.sub.5 1.77250 ν.sub.4 49.7 .sup. r.sub.10 -74.517 ______________________________________ Overall length (from the image plane) 111.0 f/f 1 ,2 =1.38 (ν 1 -ν 2 )/(ν 1 /n 1 -ν 2 /n 2 )=1.915 f/n 4 |f 7 ,8 |=1.316f/f 1 =2.48 f 5 /|f 4 =1.18f 10 /|f 7 |=0.69 f 9 /|f 8 |=1.19.

Claim 5

The lens system according to claim 2 further satisfying the following chart: ______________________________________ f = 100 F number 1: 2.9 Angle of view 2ω = 64.1° ______________________________________ r.sub.1 31.207 d.sub.1 8.587 n.sub.1 1.80400 ν.sub.1 46.6 r.sub.2 53.090 d.sub.2 2.458 r.sub.3 234.799 d.sub.3 2.369 n.sub.2 1.68893 ν.sub.2 31.1 r.sub.4 26.946 d.sub.4 1.184 r.sub.5 34.127 d.sub.5 5.774 n.sub.3 1.78590 ν.sub.3 44.2 r.sub.6 161.476 d.sub.6 1.954 r.sub.7 -85.964 d.sub.7 2.221 n.sub.4 1.64769 ν.sub.4 33.8 r.sub.8 42.936 d.sub.7 0.888 r.sub.9 64.481 d.sub.9 8.587 n.sub.5 1.83400 ν.sub.5 37.2 .sup. r.sub.10 -78.055 ______________________________________ Overall length (from the image plane) 110.8 f/f 1 ,2 =1.25 (ν.sub. -ν 2 )/(ν 1 /n 1 -ν 2 /n 2 )=2.090 f/n 4 |f 7 ,8 |=1.382f/f 1 =2.58 f 5 /|f 4 |=1.11f 10 /|f 7 |=0.71 f 9 /|f 8 |=1.17.

Claim 6

The lens system according to claim 2 further satisfying the following chart: ______________________________________ f = 100 F number 1: 2.9 Angle of view 2ω = 63.6° ______________________________________ r.sub.1 30.626 d.sub.1 8.707 n.sub.1 1.88300 ν.sub.1 40.8 r.sub.2 52.561 d.sub.2 2.023 r.sub.3 145.047 d.sub.3 2.345 n.sub.2 1.78472 ν.sub.2 25.7 r.sub.4 26.384 d.sub.4 1.349 r.sub.5 36.182 d.sub.5 5.013 n.sub.3 1.80400 ν.sub.3 46.6 r.sub.6 145.047 d.sub.6 2.052 r.sub.7 -75.987 d.sub.7 2.257 n.sub.4 1.58913 ν.sub.4 61.0 r.sub.8 41.770 d.sub.8 0.792 r.sub.9 58.398 d.sub.9 9.147 n.sub.5 1.75700 ν.sub.5 47.9 .sup. r.sub.10 -69.948 ______________________________________ Overall length (from the image plane) 109.8 f/f 1 ,2 =1.43 (ν 1 -ν 2 )/(ν 1 /n 1 -ν 2 /n 2 )=2.078 f/n 4 |f 7 ,8 |=1.385f/f 1 =2.88 f 5 /|f 4 |=1.34f 10 /|f 7 |=0.72 f 9 |f 8 |=1.09.

Claim 7

The lens system according to claim 2 further satisfying the following chart: ______________________________________ f = 100 F number 1: 2.9 Angle of View 2ω = 63.1° ______________________________________ r.sub.1 30.344 d.sub.1 9.095 n.sub.1 1.69680 ν.sub.1 55.5 r.sub.2 60.601 d.sub.2 2.372 r.sub.3 160.358 d.sub.3 2.300 n.sub.2 1.74950 ν.sub.2 35.3 r.sub.4 25.995 d.sub.4 1.415 r.sub.5 32.313 d.sub.5 5.542 n.sub.3 1.79952 ν.sub.3 42.2 r.sub.6 133.034 d.sub.6 2.366 r.sub.7 -73.826 d.sub.7 2.156 n.sub.4 1.61293 ν.sub.4 37.0 r.sub.8 43.996 d.sub.8 1.117 r.sub.9 71.326 d.sub.9 9.448 n.sub.5 1.84100 ν.sub.5 43.2 .sup. r.sub.10 -72.183 ______________________________________ Overall length (from the image plane) 112.9

Claim 8

f/f 1 ,2 =1.29 (ν 1 -ν 2 )/(ν 1 n 1 -ν 2 /n 2 )=1.612 f/n 4 |f 7 ,8 |=1.388f/f 1 =2.30 f 5 /|f 4 |=1.2f 10 /|f 7 |=0.71. f 9 /|f 8 |=1.18.

Claim 9

f/f 1 ,2 =1.29 (ν 1 -ν 2 )/(ν 1 n 1 -ν 2 /n 2 )=1.612 f/n 4 |f 7 ,8 |=1.388f/f 1 =2.30 f 5 /|f 4 |=1.2f 10 /|f 7 |=0.71. f 9 /|f 8 |=1.18.