Objective for an endoscope

Claim 2

An objective for an endoscope to be used in an endoscope employing relay lenses, said objective for an endoscope comprising, in the order from the object side, a negative lens unit, a positive lens unit, and a lens unit comprising a cemented meniscus lens arranged to be concave toward the object side.

Claim 3

An objective for an endoscope according to claim 1 wherein said meniscus lens is arranged as a single lens and said objective is arranged to fulfill the following condition: ##EQU4## where, reference symbol n a represents the refractive index of said meniscus lens, and reference symbols R a and R b respectively represent radii of curvature of the surface on the object side and surface on the image side of said cemented meniscus lens.

Claim 4

An objective for an endoscope according to claim 1 wherein said cemented meniscus lens is arranged as a cemented doublet and said objective lens arranged to fulfill the condition (1) shown below: ##EQU5## where, reference symbols n a and n b respectively represent refractive indices of the lens elements arranged on the object side and image side in said meniscus lens, and reference symbols R a and R b respectively represent radii of curvature of the surface on the object side and surface on the image side of said cemented meniscus lens.

Claim 5

An objective for an endoscope according to claim 3 further fulfilling the condition (2) shown below: ##EQU6##

Claim 6

An objective for an endoscope according to claim 4 wherein said positive lens unit comprises a cemented doublet arranged to be convex toward the object side and said objective is arranged to fulfill the conditions (3) and (4) shown below: ##EQU7## where, reference symbol R c represents the radius of curvature of the cemented surface of the cemented doublet in said positive lens unit, reference symbol f 1 represents the focal length of said negative lens unit, and reference symbol f represents the focal length of said objective as a whole.

Claim 7

An objective for an endoscope according to claim 5 wherein said negative lens unit comprises a plano-concave lens, and said positive lens unit comprises two positive cemented doublets.

Claim 8

An objective for an endoscope according to claim 6 wherein said objective has the following numerical data: ______________________________________ r.sub.0 = ∞ d.sub.0 = 0.3000 n.sub.0 = 1.51633 ν.sub.0 = 64.15 r'.sub.0 = ∞ d'.sub.0 = 0.2000 r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.6800 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 3.5000 n.sub.2 = 1.88300 ν.sub.2 = 40.76 r.sub.4 = ∞ d.sub.4 = 0.5400 n.sub.3 = 1.78800 ν.sub.3 = 47.43 r.sub.5 = -2.3820 d.sub.5 = 1.7600 r.sub.6 = 4.4630 d.sub.6 = 1.7900 n.sub.4 = 1.62041 ν.sub.4 = 60.27 r.sub.7 = -1.7990 d.sub.7 = 0.4000 n.sub.5 = 1.84666 ν.sub.5 = 23.88 r.sub.8 = -9.4030 d.sub.8 = 2.2600 r.sub.9 = -1.7880 d.sub.9 = 0.7500 n.sub.6 = 1.72342 ν.sub.6 = 38.03 r.sub.10 = ∞ d.sub.10 = 2.2000 n.sub.7 = 1.78800 ν.sub.7 = 47.43 r.sub.11 = -2.8170 ##STR57## ##STR58## ##STR59## ##STR60## ______________________________________ where, reference symbols r 1 and r 11 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 10 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 7 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 7 respectively represent Abbe's numbers of respective lenses.

Claim 9

An objective for an endoscope according to claim 5 wherein said negative lens unit comprises a plano-concave lens, and said positive lens unit comprises a single meniscus lens and a positive cemented doublet.

Claim 10

An objective for an endoscope according to claim 8 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.6133 d.sub.2 = 2.23 r.sub.3 = -68.5068 d.sub.3 = 1.8626 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -2.3154 d.sub.4 = 0.3406 r.sub.5 = 3.6741 d.sub.5 = 1.7700 n.sub.3 = 1.63854 ν.sub.3 = 55.38 r.sub.6 = -1.4541 d.sub.6 = 0.7000 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -13.0093 d.sub.7 = 1.4797 r.sub.8 = -1.7763 d.sub.8 = 1.7000 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.9 = ∞ d.sub.9 = 1.3900 n.sub.6 = 1.77250 ν.sub.6 = 49.66 r.sub.10 = -2.4237 ##STR61## ##STR62## ##STR63## ##STR64## ______________________________________ where, reference symbols r 1 throuth r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 11

An objective for an endoscope according to claim 5 wherein said negative lens unit comprises a plano-concave lens, and said positive lens unit comprises a positive lens, a single meniscus lens and a positive cemented doublet.

Claim 12

An objective for an endoscope according to claim 10 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.6899 d.sub.2 = 0.3000 r.sub.3 = 13.6272 d.sub.3 = 4.928 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -2.2510 d.sub.4 = 0.1000 r.sub.5 = -164.3754 d.sub.5 = 1.0752 n.sub.3 = 1.51633 ν.sub.3 = 64.15 r.sub.6 = -30.3152 d.sub.6 = 0.1000 r.sub.7 = 3.3059 d.sub.7 = 1.7700 n.sub.4 = 1.63854 ν.sub.4 = 55.38 r.sub.8 = -1.3278 d.sub.8 = 0.7000 n.sub.5 = 1.84666 ν.sub.5 = 23.88 r.sub.9 = -10.2303 d.sub.9 = 1.5811 r.sub.10 = -1.9987 d.sub.10 = 0.7000 n.sub.6 = 1.72825 ν.sub.6 = 28.46 r.sub.11 = ∞ d.sub.11 = 1.3900 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.12 = -2.4285 ##STR65## ##STR66## ##STR67## ##STR68## ______________________________________ where, reference symbols r 1 through r 12 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 11 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 7 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 7 respectively represent Abbe's numbers of respective lenses.

Claim 13

An objective for an endoscope according to claim 10 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.6240 d.sub.2 = 2.0663 r.sub.3 = 80.4600 d.sub.3 = 1.5954 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -2.3135 d.sub.4 = 0.1205 r.sub.5 = -112.1086 d.sub.5 = 1.4733 n.sub.3 = 1.51633 ν.sub.3 = 64.15 r.sub.6 = -30.1167 d.sub.6 = 0.0929 r.sub.7 = 3.1354 d.sub.7 = 1.7700 n.sub.4 = 1.63854 ν.sub.4 = 55.38 r.sub.8 = -1.2528 d.sub.8 = 0.7000 n.sub.5 = 1.84666 ν.sub.5 = 23.88 r.sub.9 = -9.2528 d.sub.9 = 1.0722 r.sub.10 = -1.9547 d.sub.10 = 0.7000 n.sub.6 = 1.72825 ν.sub.6 = 28.46 r.sub.11 = ∞ d.sub.11 = 1.3900 n.sub.7 = 1.77250 ν.sub.7 = 49.66 r.sub.12 = -2.4215 ##STR69## ##STR70## ##STR71## ##STR72## ______________________________________ where, reference symbols r 1 through r 12 respeftively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 11 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 7 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 7 respectively represent Abbe's numbers of respective lenses.

Claim 14

An objective for an endoscope according to claim 5 wherein said negative lens unit comprises a plano-concave lens, and said said positive lens unit comprises a plano-convex lens and a positive cemented doublet.

Claim 15

An objective for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.6540 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 5.16 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -2.4390 d.sub.4 = 0.1000 r.sub.5 = 3.6000 d.sub.5 = 1.7700 n.sub.3 = 1.63854 ν.sub.3 = 55.38 r.sub.6 = -1.7490 d.sub.6 = -0.7000 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -9.0340 d.sub.7 = 1.2000 r.sub.8 = -1.8270 d.sub.8 = 0.7000 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.9 = ∞ d.sub.9 = 1.3900 n.sub.6 = 1.77250 ν.sub.6 = 49.66 r.sub.10 = -2.5920 ##STR73## ##STR74## ##STR75## ##STR76## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 16

An objective for an endoscope according to claim 13 wherein said objective has the follwoing numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.9070 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 6.8 n.sub.2 = 1.80610 ν.sub.2 = 40.95 r.sub.4 = -2.0700 d.sub.4 = 0.5000 r.sub.5 = 5.6020 d.sub.5 = 1.7400 n.sub.3 = 1.64000 ν.sub.3 = 60.09 r.sub.6 = -2.4830 d.sub.6 = 0.4300 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -27.4420 d.sub.7 = 2.9200 r.sub.8 = -2.1630 d.sub.8 = 1.0000 n.sub.5 = 1.62004 ν.sub.5 = 36.25 r.sub.9 = ∞ d.sub.9 = 0.9800 n.sub.6 = 1.78800 ν.sub.6 = 47.43 r.sub.10 = -3.1440 ##STR77## ##STR78## ##STR79## ##STR80## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 17

An objecitve for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.6800 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 4.97 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -2.3820 d.sub.4 = 0.3100 r.sub.5 = 4.6400 d.sub.5 = 1.8400 n.sub.3 = 1.63854 ν.sub.3 = 55.38 r.sub.6 = -1.7990 d.sub.6 = 0.6000 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -8.0150 d.sub.7 = 1.8300 r.sub.8 = -1.7750 d.sub.8 = 0.5000 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.9 = ∞ d.sub.9 = 2.2000 n.sub.6 = 1.77250 ν.sub.6 = 49.66 r.sub.10 = -2.7600 ##STR81## ##STR82## ##STR83## ##STR84## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 18

An objective for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.5900 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 3.35 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -1.9990 d.sub.4 = 0.3000 r.sub.5 = 7.0690 d.sub.5 = 1.9435 n.sub.3 = 1.64000 ν.sub.3 = 60.09 r.sub.6 = -1.4710 d.sub.6 = 0.5000 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -3.1560 d.sub.7 = 1.8785 r.sub.8 = -1.4710 d.sub.8 = 0.5000 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.9 = ∞ d.sub.9 = 1.9902 n.sub.6 = 1.77250 ν.sub.6 = 49.66 r.sub.10 = -2.6380 ##STR85## ##STR86## ##STR87## ##STR88## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 19

An objective for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.80610 ν.sub.1 = 40.95 r.sub.2 = 0.7330 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 4.93 n.sub.2 = 1.80610 ν.sub.2 = 40.95 r.sub.4 = -2.2750 d.sub.4 = 0.1000 r.sub.5 = 3.5180 d.sub.5 = 1.5900 n.sub.3 = 1.64000 ν.sub.3 = 60.09 r.sub.6 = -1.8770 d.sub.6 = 0.3500 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -9.8460 d.sub.7 = 0.9800 r.sub.8 = -1.6480 d.sub.8 = 0.5300 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.9 = ∞ d.sub.9 = 1.4100 n.sub.6 = 1.69680 ν.sub.6 = 55.52 r.sub.10 = -2.2060 ##STR89## ##STR90## ##STR91## ##STR92## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 20

An objective for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.75700 ν.sub.1 = 47.87 r.sub.2 = 0.9130 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 6.09 n.sub.2 = 1.80610 ν.sub.2 = 40.95 r.sub.4 = -2.7070 d.sub.4 = 0.5000 r.sub.5 = 4.2870 d.sub.5 = 1.4300 n.sub.3 = 1.51633 ν.sub.3 = 64.15 r.sub.6 = -2.3730 d.sub.6 = 0.4000 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -7.3700 d.sub.7 = 0.9200 r.sub.8 = -2.0470 d.sub.8 = 0.8600 n.sub.5 = 1.69895 ν.sub.5 = 30.12 r.sub.9 = ∞ d.sub.9 = 1.1000 n.sub.6 = 1.75700 ν.sub.6 = 47.87 r.sub.10 = -2.8310 ##STR93## ##STR94## ##STR95## ##STR96## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 21

An objective for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.6323 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 3.7153 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -2.2149 d.sub.4 = 0.6295 r.sub.5 = 6.3945 d.sub.5 = 2.0000 n.sub.3 = 1.64000 ν.sub.3 = 60.09 r.sub.6 = -1.7561 d.sub.6 = 0.5000 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -3.6986 d.sub.7 = 2.0353 r.sub.8 = -1.5615 d.sub.8 = 0.5000 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.9 = ∞ d.sub.9 = 2.0000 n.sub.6 = 1.77250 ν.sub.6 = 49.66 r.sub.10 = -2.9074 ##STR97## ##STR98## ##STR99## ##STR100## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 22

An objective for an endoscope accroding to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.78800 ν.sub.1 = 47.43 r.sub.2 = 0.6720 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 4.957 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -2.4390 d.sub.4 = 0.1000 r.sub.5 = 4.3110 d.sub.5 = 1.4100 n.sub.3 = 1.64000 ν.sub.3 = 60.09 r.sub.6 = -1.8420 d.sub.6 = 1.0300 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -7.0940 d.sub.7 = 1.7400 r.sub.8 = -1.8770 d.sub.8 = 0.5900 n.sub.5 = 1.72825 ν.sub.5 = 28.46 r.sub.9 = -6.9230 d.sub.9 = 1.0300 n.sub.6 = 1.77250 ν.sub.6 = 49.66 r.sub.10 = -2.4390 ##STR101## ##STR102## ##STR103## ##STR104## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 23

An objective for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.75700 ν.sub.1 = 47.87 r.sub.2 = 0.9050 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 5.6400 n.sub.2 = 1.75700 ν.sub.2 = 47.87 r.sub.4 = -2.6190 d.sub.4 = 0.3000 r.sub.5 = 4.2950 d.sub.5 = 2.0500 n.sub.3 = 1.51633 ν.sub.3 = 64.15 r.sub.6 = -2.1660 d.sub.6 = 0.4000 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = -7.9380 d.sub.7 = 2.1800 r.sub.8 = -1.9880 d.sub.8 = 0.4100 n.sub.5 = 1.67270 ν.sub.5 = 32.10 r.sub.9 = 5.8970 d.sub.9 = 1.1000 n.sub.6 = 1.80610 ν.sub.6 = 40.95 r.sub.10 = -2.7420 ##STR105## ##STR106## ##STR107## ##STR108## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 24

An objective for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.0 = ∞ d.sub.0 = 0.3000 n.sub.0 = 1.51633 ν.sub.0 = 64.15 r'.sub.0 = ∞ d'.sub.0 = 0.2000 r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.80610 ν.sub.1 = 40.95 r.sub.2 = 0.7605 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 7.6000 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -3.3709 d.sub.4 = 0.1000 r.sub.5 = 3.2819 d.sub.5 = 1.3089 n.sub.3 = 1.60311 ν.sub.3 = 60.70 r.sub.6 = -3.2819 d.sub.6 = 1.8392 n.sub.4 = 1.78472 ν.sub.4 = 25.71 r.sub.7 = ∞ d.sub.7 = 1.5075 r.sub.8 = -2.0629 d.sub.8 = 1.3313 n.sub.5 = 1.78472 ν.sub.5 = 25.71 r.sub.9 = ∞ d.sub.9 = 1.2847 n.sub.6 = 1.78800 ν.sub.6 = 47.43 r.sub.10 = -3.3628 ##STR109## ##STR110## ##STR111## ##STR112## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.

Claim 25

An objective for an endoscope according to claim 13 wherein said objective has the following numerical data: ______________________________________ r.sub.0 = ∞ d.sub.0 = 0.3000 n.sub.0 = 1.51633 ν.sub.0 = 64.15 r'.sub.0 = ∞ d'.sub.0 = 0.2000 r.sub.1 = ∞ d.sub.1 = 0.2000 n.sub.1 = 1.80610 ν.sub.1 = 40.95 r.sub.2 = 0.7250 d.sub.2 = 0.3000 r.sub.3 = ∞ d.sub.3 = 7.6000 n.sub.2 = 1.78800 ν.sub.2 = 47.43 r.sub.4 = -3.2030 d.sub.4 = 0.1000 r.sub.5 = 2.7600 d.sub.5 = 1.7800 n.sub.3 = 1.62041 ν.sub.3 = 60.27 r.sub.6 = -3.1440 d.sub.6 = 0.7000 n.sub.4 = 1.84666 ν.sub.4 = 23.88 r.sub.7 = 14.1130 d.sub.7 = 1.3100 r.sub. 8 = -1.8150 d.sub.8 = 1.5400 n.sub.5 = 1.76182 ν.sub.5 = 26.55 r.sub.9 = ∞ d.sub.9 = 1.3900 n.sub.6 = 1.78800 ν.sub.6 = 47.43 r.sub.10 = -3.2700 ##STR113## ##STR114## ##STR115## ##STR116## ______________________________________ where, reference symbols r 1 through r 10 respectively represent radii of curvature of respective lens surfaces, reference symbols d 1 through d 9 respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n 1 through n 6 respectively represent refractive indices of respective lenses, and reference symbols ν 1 through ν 6 respectively represent Abbe's numbers of respective lenses.