Objective for an endoscope

Claim 2

An objective for an endoscope comprising, in the order from the object side, a first lens having a negative refractive power, a second lens unit having positive refractive power, a third lens unit having positive refractive power, an aperture stop arranged between the front end of said second lens unit and rear end of said third lens unit, and a fourth lens unit comprising a lens component having a concave surface on the object side, said objective for an endoscope being arranged to comprise at least three positive lens components including a cemented doublet and respectively located at positions between the front end of said second lens unit and rear end of said fourth lens unit.

Claim 3

An objective for an endoscope according to claim 1 fulfilling the condition (1) shown below: |h.sub.1 /f.sub.1 |>1.15|h.sub.4 /f.sub.4 | (1) where, reference symbol h 1 represents the mean value of heights of principal rays on respective surfaces of said first lens unit, reference symbol h 4 represents the mean value of heights of principal rays on respective surfaces of said fourth lens unit, reference symbol f 1 represents the focal length of said first lens unit, and reference symbol f 4 represents the focal length of said fourth lens unit.

Claim 4

An objective for an endoscope according to claim 2 further fulfilling the condition (2) shown below: f.sub.2 <9f (2) where, reference symbol f 2 represents the focal length of said second lens unit, and reference symbol f represents the focal length of the lens system as a whole.

Claim 5

An objective for an endoscope according to claim 3 further fulfilling the conditions (3), (4), (5) and (6) shown below: |f.sub.1 |<5f (3) |f.sub.23 |<4.5f (4) |f.sub.a /f.sub.b |<30 (5) R.sub.2 >0 (6) where, reference symbol f 23 represents the total focal length of said second and third lens units, reference symbols f a and f b respectively represent the largest value and smallest value out of the focal lengths of said at least three positive lens components including a cemented doublet which are respectively arranged at positions between the front end of said second lens unit and rear end of said fourth lens unit, and reference symbol R 2 represents the radius of curvature of the foremost surface of said second lens unit.

Claim 6

An objective for an endoscope according to claim 4 further fulfilling the conditions (7) and (8) shown below: -R.sub.2 '≦15f (7) R.sub.3 ≦30f (8) where, reference symbol R 2 ' represents the radius of curvature of the rearmost surface of said second lens unit, and reference symbol R 3 represents the radius of curvature of the foremost surface o said third lens unit.

Claim 7

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.018, 2ω = 100.926° IH = 0.9184 ______________________________________ r.sub.1 = 4.4097 d.sub.1 = 0.2877 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.7457 d.sub.2 = 1.0472 r.sub.3 = 2.0242 d.sub.3 = 0.3049 n.sub.2 = 1.74100 ν.sub.2 = 52.68 r.sub.4 = ∞ d.sub.4 = 0.3510 r.sub.5 = ∞ d.sub.5 = 0.3049 n.sub.3 = 1.74100 ν.sub.3 = 52.68 r.sub.6 = -2.0242 d.sub.6 = 0.0575 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.0575 r.sub.8 = 1.6116 d.sub.8 = 0.5696 n.sub.4 = 1.51633 ν.sub.4 = 64.15 r.sub.9 = -1.0213 d.sub.9 = 0.2301 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -2.1617 d.sub.10 = 0.0575 r.sub.11 = ∞ d.sub.11 = 0.2877 n.sub.6 = 1.53172 ν.sub.6 = 48.90 r.sub.12 = ∞ d.sub.12 = 0.3625 r.sub.13 = -0.8009 d.sub.13 = 0.2301 n.sub.7 = 1.72825 ν.sub.7 = 28.46 r.sub.14 = -1.3705 d.sub.14 = 0.3855 r.sub.15 = ∞ d.sub.15 = 0.5754 n.sub.8 = 1.51633 ν.sub.8 = 64.15 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.6308, 1.15|h.sub.4 /f.sub.4 | = 0.1670 f.sub.2 = 1.567, f.sub.1 = -1.055, f.sub.23 = 1.179 f.sub.a /f.sub.b = 2.732/2.526 = 1.082, R.sub.2 = 2.024 R.sub.2 ' = -2.024, R.sub.3 = 1.612 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 8

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.102, 2ω= 100.03° IH = 0.9142 ______________________________________ r.sub.1 = 3.6033 d.sub.1 = 0.2864 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.7446 d.sub.2 = 1.0439 r.sub.3 = 1.9155 d.sub.3 = 0.3136 n.sub.2 = 1.74100 ν.sub.2 = 52.68 r.sub.4 = 13.9967 d.sub.4 = 0.3855 r.sub.5 = -13.9967 d.sub.5 = 0.3136 n.sub.3 = 1.74100 ν.sub.3 = 52.68 r.sub.6 = -1.9155 d.sub.6 = 0.0573 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.0573 r.sub.8 = 1.3927 d.sub.8 = 0.6192 n.sub.4 = 1.51633 ν.sub.4 = 64.15 r.sub.9 = -0.9683 d.sub.9 = 0.2291 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -1.9872 d.sub.10 = 0.0573 r.sub.11 = ∞ d.sub.11 = 0.2864 n.sub.6 = 1.53172 ν.sub.6 = 48.90 r.sub.12 = ∞ d.sub.12 = 0.3023 r.sub.13 = -0.8271 d.sub.13 = 0.2291 n.sub.7 = 1.72825 ν.sub.7 = 28.46 r.sub.14 = -1.4614 d.sub.14 = 0.5727 r.sub.15 = ∞ d.sub.15 = 0.2864 n.sub.8 = 1.51633 ν.sub.8 = 64.15 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.6215, 1.15 |h.sub.4 /f.sub.4 | = 0.1684 f.sub.2 = 1.712, f.sub.1 = -1.115, f.sub.23 = 1.198 f.sub.a /f.sub.b = 2.962/2.196 = 1.349, R.sub.2 = 1.9155 R.sub.2 ' = -1.9155, R.sub.3 = 1.3927 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 9

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.016, 2ω = 120.0° IH = 1.0599 ______________________________________ r.sub.1 = 5.3227 d.sub.1 = 0.3327 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.7651 d.sub.2 = 0.4657 r.sub.3 = ∞ d.sub.3 = 0.3327 n.sub.2 = 1.53172 ν.sub.2 = 48.90 r.sub.4 = ∞ d.sub.4 = 0.5089 r.sub.5 = 2.3472 d.sub.5 = 0.3279 n.sub.3 = 1.74100 ν.sub.3 = 52.68 r.sub.6 = -8.0069 d.sub.6 = 0.2324 r.sub.7 = 8.0069 d.sub.7 = 0.3279 n.sub.4 = 1.74100 ν.sub.4 = 52.68 r.sub.8 = -2.3472 d.sub.8 = 0.0665 r.sub.9 = ∞ (aperture stop) d.sub.9 = 0.0665 r.sub.10 = 4.0786 d.sub.10 = 0.5611 n.sub.5 = 1.51633 ν.sub.5 = 64.15 r.sub.11 = -0.7418 d.sub.11 = 0.3327 n.sub.6 = 1.80518 ν.sub.6 = 25.43 r.sub.12 = -1.2948 d.sub.12 = 0.4657 r.sub.13 = -0.9542 d.sub.13 = 0.3327 n.sub.7 = 1.72825 ν.sub.7 = 28.46 r.sub.14 = -1.8356 d.sub.14 = 0.6653 r.sub.15 = ∞ d.sub.15 = 0.3327 n.sub.8 = 1.51633 ν.sub.8 = 64.15 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.7424, 1.15|h.sub.4 /f.sub.4 | = 0.1797 f.sub.2 = 1.389, f.sub.1 = -1.048, f.sub.23 = 1.231 f.sub.a /f.sub.b = 2.658/2.483 = 1.070, R.sub.2 = 2.3472 R.sub.2 ' = -2.3472, R.sub.3 = 4.0786 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 10

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.045, 2ω = 100.0° IH = 0.9126 ______________________________________ r.sub.1 = 3.3197 d.sub.1 = 0.2583 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.6814 d.sub.2 = 0.8784 r.sub.3 = 1.8634 d.sub.3 = 0.4254 n.sub.2 = 1.74100 ν.sub.2 = 52.68 r.sub.4 = 129.9784 d.sub.4 = 0.2067 r.sub.5 = -61.4126 d.sub.5 = 0.4274 n.sub.3 = 1.74100 ν.sub.3 = 52.68 r.sub.6 = -1.6314 d.sub.6 = 0.0572 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.0572 r.sub.8 = 3.9424 d.sub.8 = 0.6651 n.sub.4 = 1.51633 ν.sub.4 = 64.15 r.sub.9 = -0.5959 d.sub.9 = 0.2287 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -1.1684 d.sub.10 = 0.0517 r.sub.11 = ∞ d.sub.11 = 0.2859 n.sub.6 = 1.53172 ν.sub.6 = 48.90 r.sub.12 = ∞ d.sub.12 = 0.4031 r.sub.13 = -3.1629 d.sub.13 = 0.2287 n.sub.7 = 1.72825 ν.sub.7 = 28.46 r.sub.14 = 62.5974 d.sub.14 = 0.5718 r.sub.15 = ∞ d.sub.15 = 0.2859 n.sub.8 = 1.51633 ν.sub.8 = 64.15 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.6179, 1.15|h.sub.4 /f.sub.4 |= 0.1436 f.sub.2 = 1.402, f.sub.1 = -1.018, f.sub.23 = 1.248 f.sub.a /f.sub.b = 2.840/2.255 = 1.259, R.sub.2 = 1.8634 R.sub.2 ' = -1.6314, R.sub.3 = 3.9424 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's number of respective lenses.

Claim 11

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.021 2ω = 119.996° IH = 1.0627 ______________________________________ r.sub.1 = 4.0027 d.sub.1 = 0.3336 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.8672 d.sub.2 = 0.5337 r.sub.3 = ∞ d.sub.3 = 0.3336 n.sub.2 = 1.53172 ν.sub.2 = 48.90 r.sub.4 = ∞ d.sub.4 = 0.2763 r.sub.5 = 3.3266 d.sub.5 = 0.3885 n.sub.3 = 1.74100 ν.sub.3 = 52.68 r.sub.6 = -5.1676 d.sub.6 = 0.2001 r.sub.7 = -1.3143 d.sub.7 = 0.7465 n.sub.4 = 1.74100 ν.sub.4 = 52.68 r.sub.8 = -1.3763 d.sub.8 = 0.0667 r.sub.9 = ∞ (aperture stop) d.sub.9 = 0.0667 r.sub.10 = 1.1237 d.sub.10 = 0.9237 n.sub.5 = 1.51633 ν.sub.5 = 64.15 r.sub.11 = -0.8226 d.sub.11 = 0.2668 n.sub.6 = 1.80518 ν.sub.6 = 25.43 r.sub.12 = -1.4219 d.sub.12 = 0.4003 r.sub.13 = -0.8672 d.sub.13 = 0.3336 n.sub.7 = 1.72825 ν.sub.7 = 28.46 r.sub.14 = -1.8779 d.sub.14 = 0.6671 r.sub.15 = ∞ d.sub.15 = 0.3336 n.sub.8 = 1.51633 ν.sub.8 = 64.15 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.7648, 1.15|h.sub.4 /f.sub.4 | = 0.2305 f.sub.2 = 2.716, f.sub.1 = -1.320, f.sub.23 = 1.231 f.sub.a /f.sub.b = 9.543/1.675 = 5.697, R.sub.2 = 3.327 R.sub.2 ' = -1.3763, R.sub. 3 = 1.124 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 12

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.058 2ω = 140.0° IH = 1.2009 ______________________________________ r.sub.1 = 6.0196 d.sub.1 = 0.3762 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 1.1110 d.sub.2 = 1.5577 r.sub.3 = 2.6673 d.sub.3 = 1.1023 n.sub.2 = 1.71736 ν.sub.2 = 29.51 r.sub.4 = -6.2168 d.sub.4 = 0.0405 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.1308 r.sub.6 = 5.1700 d.sub.6 = 0.3762 n.sub.3 = 1.69680 ν.sub.3 = 55.52 r.sub.7 = -1745.3945 d.sub.7 = 0.0967 r.sub.8 = 9.8513 d.sub.8 = 0.7515 n.sub.4 = 1.69680 ν.sub.4 = 55.52 r.sub.9 = -0.7846 d.sub.9 = 0.3010 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -1.2594 d.sub.10 = 0.2851 r.sub.11 = -1.0047 d.sub.11 = 0.2591 n.sub.6 = 1.72825 ν.sub.6 = 28.46 r.sub.12 = -1.4804 d.sub.12 = 1.0030 r.sub.13 = ∞ d.sub.13 = 0.3762 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.7519, 1.15|h.sub.4 /f.sub.4 | = 0.1387 f.sub.2 = 2.744, f.sub.1 = -1.600, f.sub.23 = 1.520 f.sub.a /f.sub.b = 7.398/1.776 = 4.166, R.sub.2 = 2.6673 R.sub.2 ' = -6.2168, R.sub.3 = 5.1700 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 13

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 2.996, 2ω = 120.82° IH = 1.082 ______________________________________ r.sub.1 = 4.3525 d.sub.1 = 0.3390 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.7946 d.sub.2 = 0.8793 r.sub.3 = ∞ d.sub.3 = 0.3390 n.sub.2 = 1.53172 ν.sub.2 = 48.90 r.sub.4 = ∞ d.sub.4 = 0.1627 r.sub.5 = 2.5566 d.sub.5 = 0.4746 n.sub.3 = 1.72825 ν.sub.3 = 28.46 r.sub.6 = -2.5566 d.sub.6 = 0.1182 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.2585 r.sub.8 = 4.6183 d.sub.8 = 06183 n.sub.4 = 1.58913 ν.sub.4 = 60.97 r.sub.9 = -0.8237 d.sub.9 = 0.2712 n.sub.5 = 1.80518 ν.sub. 5 = 25.43 r.sub.10 = -1.6936 d.sub.10 = 0.1794 r.sub.11 = 2.4014 d.sub.11 = 0.4746 n.sub.6 = 1.65830 ν.sub.6 = 57.33 r.sub.12 = -32.2502 d.sub.12 = 0.2936 r.sub.13 = -1.2908 d.sub.13 = 0.2373 n.sub.7 = 1.80518 ν.sub.7 = 25.43 r.sub.14 = -7.7878 d.sub.14 = 0.3276 r.sub.15 = ∞ d.sub.15 = 0.6780 n.sub.8 = 1.54869 ν.sub.8 = 45.55 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.4766, 1.15 |h.sub.4 /f.sub.4 | = 0.3672 f.sub.2 = 1.827, f.sub.1 = -1.152, f.sub.23 = 1.291 f.sub.a /f.sub.b = 3.414/1.827 = 1.869, R.sub.2 = 2.557 R.sub.2 ' = -2.5566, R.sub.3 = 4.168 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 14

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, f.sub.No = 3.007 2ω = 140.03° IH = 1.1433 ______________________________________ r.sub.1 = 5.7307 d.sub.1 = 0.3582 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.9213 d.sub.2 = 1.5140 r.sub.3 = 3.4686 d.sub.3 = 0.4510 n.sub.2 = 1.72342 ν.sub.2 = 37.95 r.sub.4 = -2.7135 d.sub.4 = 0.4225 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.0335 r.sub.6 = -1.9941 d.sub.6 = 0.2149 n.sub.3 = 1.64769 ν.sub.3 = 33.80 r.sub.7 = 10.3571 d.sub.7 = 0.5806 n.sub.4 = 1.78590 ν.sub.4 = 44.18 r.sub.8 = -2.3442 d.sub.8 = 0.0116 r.sub.9 = 2.4393 d.sub.9 = 0.7777 n.sub.5 = 1.69680 ν.sub. 5 = 55.52 r.sub.10 = -4.4832 d.sub.10 = 0.4755 r.sub.11 = -1.1857 d.sub.11 = 0.3582 n.sub.6 = 1.72825 ν.sub.6 = 28.46 r.sub.12 = -1.8661 d.sub.12 = 0.9316 r.sub.13 = ∞ d.sub.13 = 0.3582 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.8187, 1.15|h.sub.4 /f.sub.4 | = 0.1215 f.sub.2 = 2.171, f.sub.1 = -1.288, f.sub.23 = 1.482 f.sub.a /f.sub.b = 13.805/2.171 = 6.359, R.sub.2 = 3.4686 R.sub.2 ' = -2.7135, R.sub.3 = -1.9941 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 15

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f =140 1, F.sub.No = 3.109, 2ω = 138.27° IH = 1.1424 ______________________________________ r.sub.1 = 5.7266 d.sub.1 = 0.3579 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.8615 d.sub.2 = 1.6801 r.sub.3 = 1.7123 d.sub.3 = 0.8102 n.sub.2 = 1.71300 ν.sub.2 = 53.84 r.sub.4 = -3.5156 d.sub.4 = 0.0039 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.0659 r.sub.6 = 2.4711 d.sub.6 = 0.6563 n.sub.3 = 1.51633 ν.sub.3 = 64.15 r.sub.7 = -0.7133 d.sub.7 = 0.2863 n.sub.4 = 1.80518 ν.sub.4 = 25.43 r.sub.8 = -1.2246 d.sub.8 = 0.0636 r.sub.9 = ∞ d.sub.9 = 0.1034 n.sub.5 = 1.53172 ν .sub.5 = 48.90 r.sub.10 = ∞ d.sub.10 = 0.1720 r.sub.11 = -0.9620 d.sub.11 = 0.2147 n.sub.6 = 1.72825 ν.sub.6 = 28.46 r.sub.12 = -2.5078 d.sub.12 = 0.0517 r.sub.13 = 7.1019 d.sub.13 = 0.5011 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = -19.3899 d.sub.14 = 0.7158 r.sub.15 = ∞ d.sub.15 = 0.3579 n.sub.8 = 1.51633 ν.sub.8 = 64.15 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.8129, 1.15|h.sub.4 /f.sub.4 | = 0.2031 f.sub.2 = 1.726, f.sub.1 = -1.189 f.sub.23 = 1.262 f.sub.a /f.sub.b = 10.132/1.726 = 5.870, R.sub.2 = 1.712 R.sub.2 ' = -3.5156, R.sub.3 = 2.471 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's number of respective lenses.

Claim 16

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.085, 2ω = 139.536° IH = 1.2073 ______________________________________ r.sub.1 = 3.1833 d.sub.1 = 0.3782 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.8334 d.sub.2 = 1.7146 r.sub.3 = 2.4300 d.sub.3 = 0.7182 n.sub.2 = 1.71300 ν.sub.2 = 53.84 r.sub.4 = -2.2325 d.sub.4 = 0.0250 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.0546 r.sub.6 = 7.1362 d.sub.6 = 0.5463 n.sub.3 = 1.51633 ν.sub.3 = 64.15 r.sub.7 = -0.7591 d.sub.7 = 0.2185 n.sub.4 = 1.80518 ν.sub.4 = 25.43 r.sub.8 = -1.2930 d.sub.8 = 0.0672 r.sub.9 = ∞ d.sub.9 = 0.1092 n.sub.5 = 1.53172 ν.sub.5 = 48.90 r.sub.10 = ∞ d.sub.10 = 0.3020 r.sub.11 = -0.8880 d.sub.11 = 0.2731 n.sub.6 = 1.72825 ν.sub.6 = 28.46 r.sub.12 = -1.1927 d.sub.12 = 0.0546 r.sub.13 = 10.5247 d.sub.13 = 0.5295 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = 117.0536 d.sub.14 = 0.7564 r.sub.15 = ∞ d.sub.15 = 0.3782 n.sub.8 = 1.51633 ν.sub.8 = 64.15 r.sub.16 = ∞ ______________________________________ |h.sub.1 /h.sub.4 | = 0.8008, 1.15|h.sub.4 /f.sub.4 | = 0.0561 f.sub.2 = 1.744, f.sub.1 = -1.383, f.sub.23 = 1.335 f.sub.a /f.sub.b = 22.360/1.744 = 12.821, R.sub.2 = 2.430 R.sub.2 ' = -2.2325, R.sub.3 = 7.136 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 17

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.044, 2ω = 140.082° IH = 1.0969 ______________________________________ r.sub.1 = 5.4983 d.sub.1 = 0.3436 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.8851 d.sub.2 = 1.3387 r.sub.3 = 3.1007 d.sub.3 = 0.4124 n.sub.2 = 1.72342 ν.sub.2 = 37.95 r.sub.4 = -6.9867 d.sub.4 = 0.2456 r.sub.5 = 6.4144 d.sub.5 = 0.2062 n.sub.3 = 1.6980 ν.sub.3 = 55.52 r.sub.6 = 2.4882 d.sub.6 = 0.2368 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.0860 r.sub.8 = 3.4511 d.sub.8 = 0.8753 n.sub.4 = 1.65830 ν.sub.4 = 57.33 r.sub.9 = -2.8298 d.sub.9 = 0.0932 r.sub.10 = 2.2130 d.sub.10 = 0.7745 n.sub.5 = 1.6980 ν.sub.5 = 55.52 r.sub.11 = -6.8452 d.sub.11 = 0.4152 r.sub.12 = -1.5863 d.sub.12 = 0.3436 n.sub.6 = 1.72825 ν.sub.6 = 28.46 r.sub.13 = -5.3578 d.sub.13 = 0.8408 r.sub.14 = ∞ d.sub.14 = 0.3436 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.15 = ______________________________________ |h.sub.1 /f.sub.1 | = 0.8288, 1.15|h.sub.4 /f.sub.4 | = 0.2126 f.sub.2 = 5.060, f.sub.1 = -1.238, f.sub.23 = 1.513 f.sub.a /f.sub.b = 3.020/2.487 = 1.214. R.sub.2 = 3.1007 R.sub.2 ' = 2.4882, R.sub.3 = 3.4511 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 18

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.027, 2ω= 132.72 IH = 1.1757 ______________________________________ r.sub.1 = 5.1635 d.sub.1 = 0.3690 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.9388 d.sub.2 = 0.6126 r.sub.3 = 3.8306 d.sub.3 = 0.2583 n.sub.2 = 1.77250 ν.sub.2 = 49.66 r.sub.4 = 2.2149 d.sub.4 = 0.9078 r.sub.5 = 2.8179 d.sub.5 = 0.5166 n.sub.3 = 1.72825 ν.sub.3 = 28.46 r.sub.6 = -2.8179 d.sub.6 = 0.0590 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.3247 r.sub.8 = 4.9768 d.sub.8 = 0.8119 n.sub.4 = 1.58913 ν.sub.4 = 60.97 r.sub.9 = -0.8827 d.sub.9 = 0.2952 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -2.0002 d.sub.10 = 0.0738 r.sub.11 = ∞ d.sub.11 = 0.3690 n.sub.6 = 1.53172 ν.sub.6 = 48.90 r.sub.12 = ∞ d.sub.12 = 0.0738 r.sub.13 = 3.0482 d.sub.13 = 0.6274 n.sub.7 = 1.65160 ν.sub.7 = 58.52 r.sub.14 = -5.5591 d.sub.14 = 0.3026 r.sub.15 = -1.5381 d.sub.15 = 0.2214 n.sub.8 = 1.84666 ν.sub.8 = 23.78 r.sub.16 = -11.0629 d.sub.16 = 0.3247 r.sub.17 = ∞ d.sub.17 = 0.7381 n.sub.9 = 1.54869 ν.sub.9 = 45.55 r.sub.18 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.7425, 1.15|h.sub.4 /f.sub.4 | = 0.3957 f.sub.2 = 2.012, f.sub.1 = -1.031, f.sub.23 = 1.588 f.sub.a /f.sub.b = 3.650/2.012 = 1.814, R.sub.2 = 2.8179 R.sub.2 ' = -2.8179, R.sub.3 = 4.9768 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 19

An objective for an endoscope according to claim 5 having the following numerical data: ______________________________________ f = 1, F.sub.No = 3.012 2ω = 140.0° IH = 1.197 ______________________________________ r.sub.1 = 5.9912 d.sub.1 = 0.3750 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.9537 d.sub.2 = 0.5250 r.sub.3 = 3.7795 d.sub.3 = 0.2250 n.sub.2 = 1.88300 ν.sub.2 = 40.78 r.sub.4 = 2.2136 d.sub.4 = 1.1585 r.sub.5 = 2.5094 d.sub.5 = 0.4591 n.sub.3 = 1.72825 ν.sub.3 = 28.46 r.sub.6 = -3.7450 d.sub.6 = 0.1125 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.3134 r.sub.8 = 4.7584 d.sub.8 = 0.7459 n.sub.4 = 1.58913 ν.sub.4 = 60.97 r.sub.9 = -0.8785 d.sub.9 = 0.3000 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -2.0123 d.sub.10 = 0.4069 r.sub.11 = 5.0897 d.sub.11 = 0.5250 n.sub.6 = 1.65830 ν.sub.6 = 57.33 r.sub.12 = -4.6412 d.sub.12 = 0.3298 r.sub.13 = -1.4135 d.sub.13 = 0.2250 n.sub.7 = 1.80518 ν.sub.7 = 25.43 r.sub.14 = -3.4758 d.sub.14 = 0.0088 r.sub.15 = ∞ d.sub.15 = 0.0750 n.sub.8 = 1.51633 ν.sub.8 = 64.15 r.sub.16 = ∞ d.sub.16 = 0.7500 r.sub.17 = ∞ d.sub.17 = 0.3750 n.sub.9 = 1.51633 ν.sub.9 = 64.15 r.sub.18 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.8141, 1.15|h.sub.4 /f.sub.4 | = 0.2636 f.sub.2 = 2.129, f.sub.1 = -1.002, f.sub.23 = 1.636 f.sub.a /f.sub.b = 3.768/2.129 = 1.770, R.sub.2 = 2.5094 R.sub.2 ' = -3.7450, R.sub.3 = 4.7584 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses.

Claim 20

An objective for an endoscope according to claim 1 wherein at least one aspherical surface is provided in at least one of a front subsystem located in front of said aperture stop and a rear subsystem located in rear of said aperture stop.

Claim 21

An objective for an endoscope according to claim 19 wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU7## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference sumbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 3.001, 2ω = 120.832° IH = 1.2267 ______________________________________ r.sub.1 = 5.9125 (aspherical surface) d.sub.1 = 0.3843 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.8298 d.sub.2 = 0.9897 r.sub.3 = ∞ d.sub.3 = 0.3843 n.sub.2 = 1.53172 ν.sub.2 = 48.90 r.sub.4 = ∞ d.sub.4 = 0.1845 r.sub.5 = 2.9048 d.sub.5 = 0.5380 n.sub.3 = 1.72825 ν.sub.3 = 28.46 r.sub.6 = -2.9283 d.sub.6 = 0.1313 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.2910 r.sub.8 = 5.4055 d.sub.8 = 0.7010 n.sub.4 = 1.58913 ν.sub.4 = 60.97 r.sub.9 = -0.9380 d.sub.9 = 0.3075 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -1.8953 d.sub.10 = 0.2034 r.sub.11 = 2.6198 d.sub.11 = 0.5380 n.sub.6 = 1.65830 ν.sub.6 = 57.33 r.sub.12 = -11.3821 d.sub.12 = 0.3328 r.sub.13 = -1.2309 (aspherical surface) d.sub.13 = 0.2690 n.sub.7 = 1.80518 ν.sub.7 = 25.43 r.sub.14 = -3.6160 d.sub.14 = 0.3714 r.sub.15 = ∞ d.sub.15 = 0.7686 n.sub.8 = 1.54869 ν.sub.8 = 45.55 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.8266, 1.15|h.sub.4 /f.sub.4 | = 0.3411 f.sub.2 = 2.083, f.sub.1 = -1.133, f.sub.23 = 1.452 f.sub.a /f.sub.b = 3.285/2.083 = 1.577, R.sub.2 = 2.9048 R.sub.2 ' = -2.9283, R.sub.3 = 5.4055 coefficients of aspherical surfaces (1st lens surface) P = 1, E = 0.22631 × 10.sup.-1 (13th lens surface) P = 1, ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.

Claim 22

An objective for an endoscope according to claim 19 wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU8## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 3.004, 2ω = 120.07° IH = 2.4366 ______________________________________ r.sub.1 = 6.3333 (aspherical surface) d.sub.1 = 0.3818 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.8893 (aspherical surface) d.sub.2 = 1.8084 r.sub.3 = 1.8590 d.sub.3 = 0.9825 n.sub.2 = 1.71300 ν.sub.2 = 53.84 r.sub.4 = -3.8279 d.sub.4 = 0.0042 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.0767 r.sub.6 = 2.7250 d.sub.6 = 0.7392 n.sub.3 = 1.51633 ν.sub.3 = 64.15 r.sub.7 = -0.7605 d.sub.7 = 0.3054 n.sub.4 = 1.80518 ν.sub.4 = 25.43 r.sub.8 = -1.3061 d.sub.8 = 0.3156 r.sub.9 = -1.0055 d.sub.9 = 0.2290 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.10 = -2.2630 d.sub.10 = 0.0552 r.sub.11 = 7.1359 d.sub.11 = 0.5346 n.sub.6 = 1.51633 ν.sub.6 = 64.15 r.sub.12 = -8.5566 (aspherical surface) d.sub.12 = 0.7636 r.sub.13 = ∞ d.sub.13 = 0.3818 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.9051, 1.15|h.sub.4 /f.sub.4 | = 0.1536 f.sub.2 = 1.891, f.sub.1 = -1.212, f.sub.23 = 1.404 f.sub.a /f.sub.b = 7.6241/1.891 = 4.032, R.sub.2 = 1.8590 R.sub.2 ' = -3.8279, R.sub.3 = 2.7250 coefficients of aspherical surfaces (1st lens surface) P = 0, E = 0.15726 × 10.sup.-1 (2nd lens surface) P= 1, (12th lens surface) P= 1 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.

Claim 23

An objective for an endoscope according to claim 19 fulfilling the conditions (15) and (17) shown below: A.sub.F ·A.sub.R <0 (15) 0.01<|A.sub.F /A.sub.R |<20 (17) where, ##EQU9## where reference symbol AF i represents the value obtained when the coefficient of astigmatism A to be caused by the deviation of the aspherical surface, which is formed on ith surface out of respective lens surfaces in said front subsystem, from the spherical surface is divided by F number, and reference symbol A Fj represents the value obtained when the coefficient of astigmatism A to be caused by the deviation of the aspherical surface, which is formed on jth surface out of respective lens surfaces in said rear subsystem, from the spherical surface is divided by F number.

Claim 24

An objective for an endoscope according to claim 22 wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU10## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 2.998, 2ω = 120.796° IH = 1.2469 ______________________________________ r.sub.1 = 5.9663 (aspherical surface) d.sub.1 = 0.3906 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.8272 d.sub.2 = 1.0070 r.sub.3 = ∞ d.sub.3 = 0.3906 n.sub.2 = 1.53172 ν.sub.2 = 48.90 r.sub.4 = ∞ d.sub.4 = 0.1875 r.sub.5 = 3.0194 d.sub.5 = 0.5469 n.sub.3 = 1.72825 ν.sub.3 = 28.46 r.sub.6 = -2.9267 d.sub.6 = 0.1334 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.2955 r.sub.8 = 5.6257 d.sub.8 = 0.7125 n.sub.4 = 1.58913 ν.sub.4 = 60.97 r.sub.9 = -0.9698 d.sub.9 = 0.3125 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -1.9298 d.sub.10 = 0.2068 r.sub.11 = 2.5655 d.sub.11 = 0.5469 n.sub.6 = 1.65830 ν.sub.6 = 57.33 r.sub.12 = -12.9642 d.sub.12 = 0.3383 r.sub.13 = -1.2924 (aspherical surface) d.sub.13 = 0.2734 n.sub.7 = 1.80518 ν.sub.7 = 25.43 r.sub.14 = -4.2008 d.sub.14 = 0.3775 r.sub.15 = ∞ d.sub.15 = 0.7813 n.sub.8 = 1.54869 ν.sub.8 = 45.55 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.8444, 1.15|h.sub.4 /f.sub.4 | = 0.3481 f.sub.2 = 2.123, f.sub.1 = -1.128, f.sub.23 = 1.469 f.sub.a /f.sub.b = 3.358/2.123 = 1.582, R.sub.2 = 3.0194 R.sub.2 ' = -2.9267, R.sub.3 = 5.6257 coefficients of aspherical surfaces (1st lens surface) P = 1, E = 0.24015 × 10.sup.-1 (13th lens surface) P = 1, E = -0.12297 × 10.sup.-1 ##STR5## ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.

Claim 25

An objective for an endoscope according to claim 23 wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU11## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 3.030, 2ω = 99.99° IH = 1.1466 ______________________________________ r.sub.1 = 6.0105 d.sub.1 = 0.3592 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.8194 (aspherical surface) d.sub.2 = 0.7184 r.sub.3 = 9.2577 d.sub.3 = 0.3592 n.sub.2 = 1.53172 ν.sub.2 = 48.90 r.sub.4 = -30.2947 d.sub.4 = 0.3879 r.sub.5 = 2.6624 d.sub.5 = 0.5029 n.sub.3 = 1.72825 ν.sub.3 = 28.46 r.sub.6 = -3.7679 d.sub.6 = 0.1252 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.2740 r.sub.8 = 4.8937 d.sub.8 = 0.6552 n.sub.4 = 1.58913 ν.sub.4 = 60.97 r.sub.9 = -0.8923 d.sub.9 = 0.2874 n.sub.5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -1.5847 d.sub.10 = 0.1901 r.sub.11 = 2.5445 d.sub.11 = 0.5029 n.sub.6 = 1.65830 ν.sub.6 = 57.33 r.sub.12 = -34.1731 d.sub.12 = 0.3000 r.sub.13 = -1.3263 d.sub.13 = 0.2514 n.sub.7 = 1.80518 ν.sub.7 = 25.43 r.sub.14 = -7.5450 (aspherical surface) d.sub.14 = 0.3471 r.sub.15 = ∞ d.sub.15 = 0.7184 n.sub.8 = 1.54869 ν.sub.8 = 45.55 r.sub.16 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.4335, 1.15|h.sub.4 /f.sub.4 | = 0.3286 f.sub.2 = 1.989, f.sub.1 = -1.110, f.sub.23 = 1.406 f.sub.a /f.sub.b = 13.378/2.215 = 6.048, R.sub.2 = 9.2577 R.sub.2 ' = -3.7679, R.sub.3 = 4.894 coefficients of aspherical surfaces (2nd lens surface) P = 0, E = 0.51666 × 10.sup.-1 F = 0.13710 (14th lens surface) P = 0, E = 0.17323 ##STR6## ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.

Claim 26

An objective for an endoscope according to claim 23, wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU12## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 3.008, 2ω = 129.582° IH = 1.2449 ______________________________________ r.sub.1 = 7.0922 (aspherical surface) d.sub.1 = 0.3901 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.9320 (aspherical surface) d.sub.2 = 1.8376 r.sub.3 = 1.9116 d.sub.3 = 0.9886 n.sub.2 = 1.71300 ν.sub.2 = 53.84 r.sub.4 = -3.8101 d.sub.4 = 0.0043 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.0800 r.sub.6 = 2.9288 d.sub.6 = 0.7605 n.sub.3 = 1.51633 ν.sub.3 = 64.15 r.sub.7 = -0.7899 d.sub.7 = 0.3121 n.sub.4 = 1.80518 ν.sub.4 = 25.43 r.sub.8 = -1.3346 d.sub.8 = 0.3051 r.sub.9 = -1.0142 d.sub.9 = 0.2340 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.10 = -2.2485 d.sub.10 = 0.0564 r.sub.11 = 6.3079 d.sub.11 = 0.5462 n.sub.6 = 1.51633 ν.sub.6 = 64.15 r.sub.12 = -6.2050 (aspherical surface) d.sub.12 = 0.7803 r.sub.13 = ∞ d.sub.13 = 0.3901 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.8950, 1.15|h.sub.4 /f.sub.4 | = 0.1226 f.sub.2 = 1.924, f.sub.1 = -1.252, f.sub.23 = 1.435 f.sub.a /f.sub.b = 6.150/1.924 = 3.196, R.sub.2 = 1.9116 R.sub.2 ' = -3.8101, R.sub.3 = 2.9288 coefficients of aspherical surfaces (1st lens surface) P = 0, E = 0.12860 × 10.sup.-1 (2nd lens surface) P = 1, (12th lens surface) P = 1, E = 0.29866 × 10.sup.-1 ##STR7## ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.

Claim 27

An objective for an endoscope according to claim 23 wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU13## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 2.996, 2ω = 110.0° IH = 1.2040 ______________________________________ r.sub.1 = 3.9397 (aspherical surface) d.sub.1 = 0.3772 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 0.7949 d.sub.2 = 0.6186 r.sub.3 = 6.9234 d.sub.3 = 0.2640 n.sub.2 = 1.77250 ν.sub.2 = 49.66 r.sub.4 = 4.1093 d.sub.4 = 0.9559 r.sub.5 = 2.7606 d.sub.5 = 0.5281 n.sub.3 = 1.72825 ν.sub.3 = 28.46 r.sub.6 = -2.2016 d.sub.6 = 0.0754 r.sub.7 = ∞ (aperture stop) d.sub.7 = 0.3167 r.sub.8 = 17.2715 d.sub.8 = 0.8298 n.sub.4 = 1.58913 ν.sub.4 = 60.97 r.sub.9 = -0.8495 d.sub.9 = 0.3018 n.sub. 5 = 1.80518 ν.sub.5 = 25.43 r.sub.10 = -2.4692 d.sub.10 = 0.0754 r.sub.11 = ∞ d.sub.11 = 0.3772 n.sub.6 = 1.53172 ν.sub.6 = 48.90 r.sub.12 = ∞ d.sub.12 = 0.0754 r.sub.13 = 2.1704 d.sub.13 = 0.6412 n.sub.7 = 1.65160 ν.sub.7 = 58.52 r.sub.14 = -23.8501 d.sub.14 = 0.3103 r.sub.15 = -1.5651 d.sub.15 = 0.2263 n.sub.8 = 1.84666 ν.sub.8 = 23.78 r.sub.16 = -5.0483 (aspherical surface) d.sub.16 = 0.3163 r.sub.17 = ∞ d.sub.17 = 0.7544 n.sub.9 = 1.54869 ν.sub.9 = 45.55 r.sub.18 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.7355, 1.15|h.sub.4 /f.sub.4 | = 0.3202 f.sub.2 = 1.761, f.sub.1 = -1.033, f.sub.23 = 1.642 f.sub.a /f.sub.b = 8.594/1.761 = 4.880, R.sub.2 = 2.7606 R.sub.2 ' = -2.2016, R.sub.3 = 17.2715 coefficients of aspherical surfaces (1st lens surface) P = 1, E = 0.25038 × 10.sup.-1 F = 0.45776 × 10.sup.-2 (16th lens surface) P = 1, E = 0.23705 × 10.sup.-1 ##STR8## ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.

Claim 28

An objective for an endoscope according to claim 19 fulfilling the condition (22) shown below: 0≦Q.sub.h <4 (22) where, the value of Q h is obtained by the formula Q h =|Q S /Q M | wherein the value of Q S is obtained by the formula Q S =Q F +Q R wherein reference symbol Q F represents the sum of Q i in said front subsystem, and reference symbol Q R represents the sum of Q i in said rear subsystem, the value of Q i being calculated by the formula Q.sub.i =(N.sub.i -N.sub.i+1){Eh.sub.i.sup.2 +Fh.sub.i.sup.4 +Gh.sub.i.sup.6 +. . . } wherein reference symbol N i represents the refractive index of the medium existing on the object side of ith surface, and reference symbol N i+1 represents the refractive index of the medium existing on the image side of ith surface, reference symbol Q M representing either Q F or Q R which has the larger absolute value out of them.

Claim 29

An objective for an endoscope according to claim 27 wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU14## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 3.035, 2ω= 140.02° IH = 1.6295 ______________________________________ r.sub.1 = 5.8908 d.sub.1 = 0.5105 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 1.5830 (aspherical surface) d.sub.2 = 2.1049 r.sub.3 = 7.1003 d.sub.3 = 0.7497 n.sub.2 = 1.72342 ν.sub.2 = 37.95 r.sub.4 = -6.1767 d.sub.4 = 0.0056 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.1188 r.sub.6 = 12.6805 d.sub.6 = 0.9930 n.sub.3 = 1.65830 ν.sub.3 = 57.33 r.sub.7 = -1.2573 d.sub.7 = 0.4084 n.sub.4 = 1.80518 ν.sub.4 = 25.43 r.sub.8 = -2.0394 d.sub.8 = 0.2964 r.sub.9 = -1.4831 d.sub.9 = 0.3063 n.sub.5 = 1.84666 ν.sub.5 = 23.78 r.sub.10 = -1.6611 d.sub.10 = 0.1532 r.sub.11 = 8.1827 d.sub.11 = 0.7147 n.sub.6 = 1.51633 ν.sub.6 = 64.15 r.sub.12 = -1.8839 (aspherical surface) d.sub.12 = 1.0291 r.sub.13 = ∞ d.sub.13 = 0.5105 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = ∞ ______________________________________ |h.sub.1 /f.sub.1 |= 0.6747, 1.15|h.sub.4 /f.sub.4 |= 0.3865 f.sub.2 = 4.677, f.sub.1 = -2.596, f.sub.23 = 2.168 f.sub.a /f.sub.b = 4.677/3.039 = 1.539, R.sub.2 = 7.01003 R.sub.2 '= -6.1767, R.sub.3 = 12.6805 coefficients of aspherical surfaces (2nd lens surface) P = 1, E = 0.59267 × 10.sup.-1 F = -0.29531 × 10.sup.-1 (12th lens surface) P = 1, E = 0.10652 Qh = 1.1459 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.

Claim 30

An objective for an endoscope according to claim 27 wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU15## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 3.032, 1ω= 140.0° IH = 1.4229 ______________________________________ r.sub.1 = 5.6068 d.sub.1 = 0.4458 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 1.2801 (aspherical surface) d.sub.2 = 2.0273 r.sub.3 = 3.6331 d.sub.3 = 0.7592 n.sub.2 = 1.72342 ν.sub.2 = 37.95 r.sub.4 = -5.0124 d.sub.4 = 0.0049 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.1026 r.sub.6 = 7.4259 d.sub.6 = 0.8539 n.sub.3 = 1.65830 ν.sub.3 = 57.33 r.sub.7 = -1.1844 d.sub.7 = 0.3566 n.sub.4 = 1.80518 ν.sub.4 = 25.43 r.sub.8 = -1.7581 d.sub.8 = 0.3181 r.sub.9 = -1.2303 d.sub.9 = 0.2675 n.sub.5 = 1.84666 ν.sub.5 = 23.78 r.sub.10 = -1.6302 d.sub.10 = 0.1337 r.sub.11 = 50.6667 d.sub.11 = 0.6241 n.sub.6 = 1.51633 ν.sub.6 = 64.15 r.sub.12 = -2.1201 (aspherical surface) d.sub.12 = 0.8985 r.sub.13 = ∞ d.sub.13 = 0.4458 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.7323, 1.15|h.sub.4 /f.sub.4 | = 0.1542 f.sub.2 = 3.023, f.sub.1 = -1.974, f.sub.23 = 1.662 f.sub.a /f.sub.b = 3.957/2.439 = 1.622, R.sub.2 = 3.6331 R.sub.2 ' = -5.0124, R.sub.3 = 7.4259 coefficients of aspherical surfaces (2nd lens surface) P = 1, E = 0.61335 × 10.sup.-1 F = -0.39851 × 10.sup.-1 (12th lens surface) P = 1, E = 0.10463 Q.sub.h = 1.3035 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.

Claim 31

An objective for an endoscope according to claim 27 wherein each of said aspherical surfaces has a shape expressed by the formula shown below when the optical axis is designated as the x axis and a straight line, which is perpendicular to the optical axis and which passes the intersecting point between said aspherical surface and optical axis, is designated as the y axis: ##EQU16## where, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface at a position near the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the coefficients of aspherical surface of the second order, fourth order, sixth order, eighth order and so on, and wherein said objective for an endoscope has the following numerical data: ______________________________________ f = 1, F.sub.No = 3.033, 2ω= 140.01° IH = 1.4387 ______________________________________ r.sub.1 = 4.1525 d.sub.1 = 0.4507 n.sub.1 = 1.88300 ν.sub.1 = 40.78 r.sub.2 = 1.2907 (aspherical surface) d.sub.2 = 1.9824 r.sub.3 = 6.0185 d.sub.3 = 0.6489 n.sub.2 = 1.72342 ν.sub.2 = 37.95 r.sub.4 = -5.3701 d.sub.4 = 0.0050 r.sub.5 = ∞ (aperture stop) d.sub.5 = 0.0988 r.sub.6 = 9.8733 d.sub.6 = 0.7706 n.sub.3 = 1.65830 ν.sub.3 = 57.33 r.sub.7 = 2.1176 d.sub.7 = 0.3606 n.sub.4 = 1.80518 ν.sub.4 = 25.43 r.sub.8 = -1.7128 d.sub.8 = 0.3216 r.sub.9 = -1.6356 d.sub.9 = 0.2704 n.sub.5 = 1.84666 ν.sub.5 = 23.78 r.sub.10 = -1.6634 (aspherical surface) d.sub.10 = 0.1352 r.sub.11 = -3.0982 d.sub.11 = 0.6310 n.sub.6 = 1.51633 ν.sub.6 = 64.15 r.sub.12 = -1.5977 (aspherical surface) d.sub.12 = 0.9086 r.sub.13 = ∞ d.sub.13 = 0.4507 n.sub.7 = 1.51633 ν.sub.7 = 64.15 r.sub.14 = ∞ ______________________________________ |h.sub.1 /f.sub.1 | = 0.6803, 1.15|h.sub.4 /f.sub.4 | = 0.1969 f.sub.2 = 4.019, f.sub.1 = -2.290, f.sub.23 = 1.664 f.sub.a /f.sub.b = 33.391/2.198 = 15.192, R.sub.2 = 6.0185 R.sub.2 ' = -5.3701, R.sub.3 = 9.8733 coefficients of aspherical surfaces (2nd lens surface) P = 1, E = 0.64518 × 10.sup.-1 F = -0.38100 × 10.sup.-1 (10th lens surface) P = 1, E = 0.10921 (12th lens surface) P = 1, E = 0.82721 × 10.sup.-2 Qh = 1.3030 ______________________________________ where, reference symbols r 1 , r 2 , . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 , d 2 , . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 , n 2 , . . . respectively represent refractive indices of respective lenses, and reference symbols ν 1 , ν 2 , . . . respectively represent Abbe's numbers of respective lenses, of the coefficients of aspherical surface, those which are not shown in the numerical data are zero.