Claims
- 1. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, said front lens unit comprising a negative meniscus lens component convex toward the object side arranged that the surface on the object side thereof is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis, and said rear lens unit comprising a plurality of lens components including a positive cemented doublet, one of said lens components being arranged so that the surface of the object side thereof is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis, the air space between the surface on the extreme image side of said front lens and said stop being constant.
- 2. An objective lens system for an endoscope according to claim 1, fulfilling the following conditions:
- A.sub.F.A.sub.R <0
- 0.01<.vertline.A.sub.F /A.sub.R .vertline.<10
- where, reference symbol A.sub.F represents the sum of coefficients of astigmatism of said aspherical surfaces provided in said front lens unit, and reference symbol A.sub.R represents the sum of coefficients of astigmatism of said aspherical surfaces provided in said rear lens unit.
- 3. An objective lens system for an endoscope according to claim 2, wherein said front lens unit has negative refractive power, said rear lens unit has positive refractive power and said stop located between said front and rear lens units in the vicinity of the front focal point.
- 4. An object lens system for an endoscope according to claim 3 wherein said rear lens unit comprises a positive meniscus lens component convex toward the image side, a positive lens component, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the condition shown below: ##EQU5## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the aspherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 5. An objective lens system for an endoscope according to claim 4 further fulfilling the following conditions:
- .vertline.f.sub.1 .vertline.<2.5f
- D<1.8f
- where, reference symbol f.sub.1 represents the focal length of said front lens unit, and reference symbol D represents the distance from the rearmost surface of said front lens unit to the foremost surface of said rear lens unit.
- 6. An objective lens system for an endoscope according to claim 5 wherein the surface on the object side of said cemented doublet in said rear lens unit is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis.
- 7. An objective lens system for an endoscope according to claim 5 wherein the surface on the object side of said rearmost positive lens component in said rear lens unit is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis.
- 8. An objective lens system for an endoscope according to claim 7 having the following numerical data:
- ______________________________________r.sub.1 = 6.3984 (aspherical surface)d.sub.1 = 0.5595 n.sub.1 = 1.51633 .nu..sub.1 = 64.15r.sub.2 = 0.6778d.sub.2 = 0.9092r.sub.3 = .infin. (stop)d.sub.3 0.2098r.sub.4 = 5.5166d.sub.4 1.2588 n.sub.2 = 1.58913 .nu..sub.2 = 61.11r.sub.5 = -1.5634d.sub.5 = 0.1399r.sub.6 = 29.9814d.sub.6 = 1.2588 n.sub.3 = 1.58913 .nu..sub.3 = 61.11r.sub.7 = -4.3416d.sub.7 = 0.1399r.sub.8 = 2.8491d.sub.8 = 2.0980 n.sub.4 = 1.61800 .nu..sub.4 = 63.38r.sub.9 = -2.3590d.sub.9 = 0.4755 n.sub.5 = 1.84666 .nu..sub.5 = 23.90r.sub.10 = -148.8749d.sub.10 = 0.2114r.sub.11 = 1.7587 (aspherical surface)d.sub.11 = 1.1277 n.sub.6 1.51633 .nu..sub.6 64.15r.sub.12 = .infin.f = 1, 2.omega. = 119.986.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.35094 .times. 10.sup.-1F = -0.35734 .times. 10.sup.-2aspherical surface coefficient of 11th surfaceP = 1, E = -0.11938F = 0.11557 .times. 10.sup.-2A.sub.F = -0.01539, A.sub.R = 0.04461A.sub.F /A.sub.R = -0.34499f.sub.1 = -1.519, D.sub.1 = 1.119______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lens, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 9. An objective lens system for an endoscope according to claim 8 wherein said front lens unit comprises two negative lens components each having a concave surface on the image side, said rear lens unit comprises a positive lens component, a positive lens component, a positive cemented doublet, and a positive lens component having a convex surface on the object side, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said a spherical surfaces fulfills the conditions shown below: ##EQU6## where, reference symbol f.sub.F represents the focal length of said front lens group, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power eighth power and so on.
- 10. An objective lens system for an endoscope according to claim 9 wherein the surface on the object side of said rearmost positive lens component in said rear lens unit is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis.
- 11. An objective lens system for an endoscope according to claim 10 having the following numerical data:
- ______________________________________r.sub.1 = 16.1623 (aspherical surface)d.sub.1 = 0.7273 n.sub.1 = 1.49109 .nu..sub.1 = 57.00r.sub.2 = 1.6598d.sub.2 = 1.2510r.sub.3 = 19.6061d.sub.3 = 1.1736 n.sub.2 = 1.78800 .nu.2 .sub. = 47.43r.sub.4 = 1.9317d.sub.4 = 1.0628r.sub.5 = .omega. (stop)d.sub.5 = 0.1119r.sub.6 = 14.1042d.sub.6 = 1.2096 n.sub.3 = 1.58913 .nu..sub.3 = 60.97r.sub.7 = -2.9033d.sub.7 = 0.6212r.sub.8 = -17.7424d.sub.8 = 1.1115 n.sub.4 = 1.58913 .nu..sub.4 = 60.97r.sub.9 = -3.1102d.sub.9 = 0.1372r.sub.10 = 6.4185d.sub.10 = 2.1674 n.sub.5 = 1.61800 .nu..sub.5 = 63.38r.sub.11 = -2.2840d.sub.11 = 0.2467 n.sub.6 = 1.84666 .nu..sub.6 = 23.90r.sub.12 = -8.1806d.sub.12 = 0.6832r.sub.13 = 2.5389 (aspherical surface)d.sub.13 = 2.5050 n.sub.7 = 1.49109 .nu..sub.7 = 57.00r.sub.14 = .infin.f = 1 , 2.omega. = 116.002.degree.aspherical surface coefficient of 1st surfaceP = 1 , E = 0.79514 .times. 10.sup.-2 , F = 0aspherical surface coefficient of 13th surfaceP = 1 , E = 0.79514 .times. 10.sup.-2 , F = 0A.sub.F = -0.01083 , A.sub.R = -0.03888A.sub.F /A.sub.R = -0.27855 , f.sub.F = -1.251______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively thicknesses of respective lenses and airspaces between respective lens, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 12. An objective lens system for an endoscope according to claim 10 having the following numerical data:
- ______________________________________r.sub.1 = 5.8227 (aspherical surface)d.sub.1 = 0.6155 n.sub.1 = 1.88300 .nu..sub.1 = 40.78r.sub.2 = 1.7026d.sub.2 - 1.0434r.sub.3 = 2.3876d.sub.3 = 0.4505 n.sub.2 = 1.78800 .nu..sub.2 = 47.43r.sub.4 = 0.9653d.sub.4 = 0.8366r.sub.5 = .infin. (stop)d.sub.5 = 0.122r.sub.6 = -7.1626d.sub.6 - 1.1660 n.sub.3 - 1.58913 .nu..sub.3 = 60.97r.sub.7 = -1.5456d.sub.7 = 0.6796r.sub.8 = -5.6290d.sub.8 = 1.1942 n.sub.4 = 1.58913 .nu..sub.4 = 60.97r.sub.9 = -2.7189d.sub.9 = 0.1287r.sub.10 = 3.58785d.sub.10 = 2.0335 n.sub.5 = 1.61800 .nu..sub.5 = 63.38r.sub.11 = -2.1429d.sub.11 = 0.3520 n.sub.6 = 1.84666 .nu..sub.6 = 23.90r.sub.12 = 20.9041d.sub.12 = 0.5519r.sub.13 = 2.1991 (aspherical surface)d.sub.13 = 2.2863 n.sub.7 = 1.49109 .nu..sub.7 = 57.00r.sub.14 = .infin.f = 1, 2.omega. = 112.91.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.96277 .times. 10.sup.-2, F = 0aspherical surface coefficient of 13th surfaceP = 1, E = -0.32235 .times. 10.sup.-1, F = 0A.sub.F = -0.01292 , A.sub.R = 0.03088A.sub.F /A.sub.R = -0.41389 , f.sub.F = -1.044______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, n.sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 13. An objective lens system for an endoscope according to claim 1, wherein a meniscus lens component concave toward the image side is arranged on the extreme object side of said front lens unit, a meniscus lens component concave toward the object side is arranged on the extreme image side of said rear lens unit, a positive lens component is arranged on the extreme image side of said front lens unit, a positive lens component is arranged on the extreme object said of said rear lens units, and a stop is arranged between said positive lenses arranged in front lens unit and rear lens unit.
- 14. An objective lens system for an endoscope according to claim 13 wherein said front lens unit comprises a negative lens component having a concave surface on the image side, and a positive cemented doublet, said rear lens group comprises a positive cemented doublet, and a meniscus lens component convex toward the image side, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, each of said aspherical surfaces fulfills the condition shown below: ##EQU7## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, and reference symbols B, E, F, G, respecively represent the aspherical coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 15. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear units, said front lens unit comprising a negative lens component concave toward the image side arranged so that the surface on the object side thereof is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis, and said rear lens unit comprising a plurality of lens components including a positive cemented doublet one of said lens components being arranged so that the surface on the image side thereof is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis, the air space between the surface on the extreme image side of said front lens unit and said stop being constant.
- 16. An objective lens system for an endoscope according to claim 15 fulfilling the following conditions:
- A.sub.F.A.sub.R <0
- 0.01<.vertline.A.sub.F/A.sbsb.R.sub..vertline.<10
- where, reference symbol A.sub.F represents the sum of coefficients of astigmatism of said aspherical surfaces provided in said front lens unit, and reference symbol A.sub.R represents the sum of coefficients of astigmatism of said aspherical surfaces provided in said rear lens unit.
- 17. An objective lens system for an endoscope according to claim 16, wherein said front lens unit has negative refractive power, said rear lens unit has positive refractive power and said stop located between said front and rear lens unit in the vicinity of the front focal point.
- 18. An objective lens system for an endoscope according to claim 17 wherein said negative lens component in said front lens unit is a negative meniscus lens convex toward the object side, said rear lens unit comprises a positive meniscus lens component convex toward the image side, a positive lens component, a positive cemented doublet, and a positive lens component, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designed as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the condition shown below. ##EQU8## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the aspherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 19. An objective lens system for an endoscope according to claim 18 fulfilling the following conditions:
- .vertline.f.sub.1 .vertline.<2.5f
- D<1.8f
- where, reference symbol f.sub.1 represents the focal length of said front lens unit, and reference symbol d represents the distance from the rearmost surface of said front lens unit to the foremost surface of said rear lens unit.
- 20. An objective lens system for an endoscope according to claim 19 wherein the surface on the image side of said cemented doublet in said rear lens unit is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis.
- 21. An objective lens system for an endoscope according to claim 20 having the following numerical data:
- ______________________________________r.sub.1 = 6.1180 (aspherical surface)d.sub.1 = 0.5298 n.sub.1 = 1.51633 .nu..sub.1 = 64.15r.sub.2 0.6522d.sub.2 = 0.8609r.sub.3 = .infin. (stop)d.sub.3 = 0.1987r.sub.4 = -5.6100d.sub.4 = 1.1921 n.sub.2 = 1.58913 .nu..sub.2 = 61.11r.sub.5 = -1.4817d.sub.5 = 0.1325r.sub.6 = 197.8841d.sub.6 = 1.1921 n.sub.3 = 1.58913 .nu..sub.3 = 61.11r.sub.7 = -4.2546d.sub.7 = 0.1325r.sub.8 = 2.4509d.sub.8 = 1.9868 n.sub.4 1.61800 .nu..sub.4 = 63.88r.sub.9 = -2.4826d.sub.9 = 0.4503 n.sub.5 = 1.84666 .nu..sub.5 - 23.90r.sub.10 = -50.0313 (aspherical surface)d.sub.10 = 0.2181r.sub.11 = 2.5823d.sub.11 = 1.0680 n.sub.6 = 1.51633 .nu..sub.6 = 64.15r.sub.12 = .infin.f = 1, 2.omega. = 105.004.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.58449 .times. 10.sup.-1F = -0.2063f3 .times. 10.sup.-2aspherical surface coefficient of 10th surfaceP = 1, E = 0.49349 .times. 10 .sup.-1F = 0.11654 .times. 10.sup.-1A.sub.F = -0.01847, A.sub.R = 0.0294A.sub.F /A.sub.R = -.062823f.sub.1 = -1.462, D.sub.1 = 1.06______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, references symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 22. An objective lens system for an endoscope according to claim 20 having the following numerical data:
- ______________________________________r.sub.1 = 4.2490 (aspherical surface)d.sub.1 = 0.4310 n.sub.1 1.51633 .nu..sub.1 = 64.15r.sub.2 = 0.5336d.sub.2 = 0.7004r.sub.3 = .infin. (stop)d.sub.3 = 0.1616r.sub.4 = -5.1135d.sub.4 = 0.9698 n.sub.2 1.58913 .nu..sub.2 = 61.11r.sub.5 = -1.1946d.sub.5 = 0.1078r.sub.6 = 431.8244d.sub.6 -0.9698 n.sub.3 = 1.58913 .nu..sub.3 = 61.11r.sub.7 = -3.3672d.sub.7 = 0.1078r.sub.8 = 2.4551d.sub.8 = 1.6164 n.sub.4 = 1.61800 .nu..sub.4 = 63.38r.sub.9 = -1.6551d.sub.9 = 0.3664 n.sub.5 1.84666 .nu..sub.5 = 23.90r.sub.10 = 10.7060 (aspherical surface)d.sub.10 = 0.3668r.sub.11 = 1.7661d.sub.11 1.0237 n.sub.6 = 1.51633 .nu..sub.6 = 64.15r.sub.12 = .infin.f = 1, 2.omega.= 104.908.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.38819 .times. 10.sup.-1F = -0.23129 .times. 10.sup.-2aspherical surface coefficient of 10th surfaceP = 1, E = 0.42299 .times. 10.sup.-1F = -0.15892 .times. 10.sup.-1A.sub.F = -0.00364, A.sub.R = 0.00995A.sub.F /A.sub.R = -0.36583f.sub.1 = -1.231, D1 - 0.862______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thickness of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively Abbe's numbers of respective lenses.
- 23. An objective lens system for an endoscope according to claim 17 wherein said negative lens component in said front lens unit is a negative meniscus lens convex toward the object side, said rear lens unit comprises a positive lens component, and a cemented doublet, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designed as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the condition shown below: ##EQU9## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 24. An objective lens system for an endoscope according to claim 23 further fulfilling the following conditions:
- .vertline.f.sub.1 .vertline.>1.8f
- D>1.5f
- where, reference symbol f.sub.1 represents the focal length of said front lens unit, and reference symbol D represents the distance from the rearmost surface of said front lens unit to the foremost surface of said rear lens unit.
- 25. An objective lens system for an endoscope according to claim 24 wherein the surface on the image side of said cemented doublet in said rear lens is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis.
- 26. An objective lens system for an endoscope according to claim 25 having the following numerical data:
- ______________________________________r.sub.1 = 6.8768 (aspherical surface)d.sub.1 = 0.7795 n.sub.1 = 1.88300 .nu..sub.1 = 40.78r.sub.2 = 1.9045d.sub.2 = 4.2438r.sub.3 = .infin. (stop)d.sub.3 = 0.6058r.sub.4 = -18.35668d.sub.4 = 0.8762 n.sub.2 = 1.69680 .nu..sub.2 = 55.52r.sub.5 = -3.5516d.sub.5 = 0.3341r.sub.6 = 2.4922d.sub.6 = 1.5367 n.sub.3 = 1.64000 .nu..sub.3 = 60.09r.sub.7 = -1.7814d.sub.7 0.4454 n.sub.4 = 1.84666 .nu..sub.4 = 23.88r.sub.8 = -3.4576 (aspherical surface)f 1, 2.omega. = 95.0.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.63687 .times. 10.sup.-2F = -0.12992 .times. 10.sup.-3aspherical surface coefficient of 8th surfaceP = 1, E = 0.22882 .times. 10.sup.-1F = -0.38644v .times. 10.sup.-2A.sub.F = -.00116, A.sub.R = 0.01893A.sub.F /A.sub.R = -0.06128f.sub.1 = -3.22, D.sub.1 = 4.85______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 27. An objective lens system for an endoscope according to claim 25 having the following numerical data:
- ______________________________________r.sub.1 = 9.3756 (aspherical surface)d.sub.1 = 0.8621 n.sub.1 = 1.88300 .nu..sub.1 = 40.78r.sub.2 = 2.0517d.sub.2 = 4.8958r.sub.3 = .infin. (stop)d.sub.3 = 0.8554r.sub.4 = 15.9800d.sub.4 0.9690 n.sub.2 = 1.69680 .nu..sub.2 = 55.52r.sub.5 = -5.9752d.sub.5 = 0.3695r.sub.6 = 3.4698d.sub.6 = 1.6374 n.sub.3 = 1.64000 .nu..sub.3 = 60.09r.sub.7 = -1.7857d.sub.7 = 0.4926 n.sub.4 = 1.84666 .nu..sub.4 = 23.88r.sub.8 = -2.9875 (aspherical surface)f = 1, 2.omega. = 94.424.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.41954 .times. 10.sup.-2F = 0.52825 .times. 10.sup.-4aspherical surface coefficient of 8th surfaceP = 1, E = 0.18885 .times. 10.sup.-1F = -0.24735 .times.10.sup.-2A.sub.F = -0.00001, A.sub.r = 0.00003A.sub.F /A.sub.R = -0.33333f.sub.1 = -3.148, D.sub.1 = 5.751______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, references symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 28. An objective lens system for an endoscope according to claim 17 wherein said front lens unit comprises two negative lens components each having a concave surface on the image side, said rear lens unit comprises a positive lens component, a positive lens component, a positive cemented doublet, and a positive lens component having a convex surface on the object side, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the conditions shown below: ##EQU10## where, reference symbol f.sub.F represents the focal length of said front lens group, reference symbol f represents the focal length of the lens system as a whole, reference C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, said reference symbols B, E, F, G, . . . respectively represent the aspherical surface coefficients of the second power, fourth power, sixth power eighth power and so on.
- 29. An objective lens system for an endoscope according to claim 16, wherein a meniscus lens component concave toward the image side is arranged on the extreme object side of said front lens unit, a meniscus lens component concave toward the object side is arranged on the extreme image side of said rear lens unit, a positive lens component is arranged on the extreme image side of said front lens unit, a positive lens component is arranged on the extreme object side of said rear lens unit, and stop is arranged between said positive lenses arranged in the front lens unit and rear lens unit.
- 30. An objective lens system for an endoscope according to claim 29 wherein said front lens unit comprises a negative lens component having a concave surface on the image side, and a positive cemented doublet, said rear lens group comprises a positive cemented doublet, and a meniscus lens component convex toward the image side, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said spherical surfaces fulfills the condition shown below: ##EQU11## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on 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 aspherical the aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 31. An objective lens system for an endoscope according to claim 30 wherein the surface on the image side of said meniscus lens component in said rear lens unit is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis.
- 32. An objective lens system for an endoscope according to claim 31 further fulfilling the following condition:
- f.sub.4 <5f
- where, reference symbol f.sub.4 represents the focal length of said meniscus lens component constituting said rear lens unit.
- 33. An objective lens system for an endoscope according to claim 31 further fulfilling the following condition:
- f.sub.4 <-3f
- where, reference symbol f.sub.4 represents the focal length of said meniscus lens component constituting said rear lens unit.
- 34. An objective lens system for an endoscope according to claim 32 having the following numerical data:
- ______________________________________r.sub.1 = .infin. (aspherical surface)d.sub.1 = 0.2681 n.sub.1 = 1.51633 .nu..sub.1 = 64.15r.sub.2 = 1.0400d.sub.2 = 1.4189r.sub.3 = 2.1359d.sub.3 = 0.5362 n.sub.2 = 1.59270 .nu..sub.2 = 35.29r.sub.4 = -1.5405d.sub.4 = 0.2145 n.sub.3 = 1.83400 .nu..sub.3 = 37.16r.sub.5 = -3.9303d.sub.5 = 0.0536r.sub.6 = .infin. (stop)d.sub.6 = 0.0536r.sub.7 = 3.1352d.sub.7 = 0.5898 n.sub.4 = 1.62041 .nu..sub.4 = 60.27r.sub.8 = -0.6278d.sub.8 = 0.2145 n.sub.5 = 1.80518 .nu..sub.5 = 25.43r.sub.9 = -1.2322d.sub.9 = 0.8609r.sub.10 = -2.2697d.sub.10 = 0.2681 n.sub.6 = 1.84666 .nu..sub.6 = 23.88r.sub.11 = -1.9100 (aspherical surface)f = 1, 2.omega.= 100.0.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.39752 .times. 10.sup.-2aspherical surface coefficient of 11th surfaceP = 1, E = 0.25509A.sub.F = -.00044, A.sub.R = 0.01371A.sub.f /A.sub.R = -0.03209, E.sub.F = 0-.003975E.sub.B = 0.25509, E.sub.B /E.sub.F = 64.17f.sub.4 = 10.608______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbol n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 35. An objective lens system for an endoscope according to claim 32 having the following numerical data:
- ______________________________________r.sub.1 = .infin. (aspherical surface)d.sub.1 = 0.2772 n.sub.1 = 1.51633 .nu..sub.1 = 64.15r.sub.2 = 0.8565d.sub.2 = 1.5573r.sub.3 = 2.4166d.sub.3 = 0.5543 n.sub.2 = 1.59270 .nu..sub.2 = 35.29r.sub.4 = -2.1023d.sub.4 = 0.2217 n.sub.3 = 1.83400 .nu..sub.3 = 37.16r.sub.s = -3.7245d.sub.s = 0.0554r.sub.6 = .infin. (stop)d.sub.6 = 0.0554r.sub.7 = 3.1854d.sub.7 = 0.6098 n.sub.4 = 1.62041 .nu..sub.4 = 60.27r.sub.8 = -0.6391d.sub.8 = 0.2217 n.sub.s = 1.80518 .nu..sub.s = 25.43r.sub.9 = -1.2642d.sub.9 = 0.8900r.sub.10 = -1.7084d.sub.10 = 0.2772 n.sub.6 = 1.84666 .nu..sub.6 = 23.88r.sub.11 = -2.1791 (aspherical surface)f = 1, 2.omega. = 50.006.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.25013 .times. 10.sup.-1aspherical surface coefficient of 11th surfaceP = 1, E = 0.11723, F = 0.11906A.sub.F - -0.00283, A.sub.R = 0.00718A.sub.F /A.sub.F = -0.39415, E.sub.F = 0.02501E.sub.B = 0.1172, E.sub.B /E.sub.R = 4.686f.sub.4 = -12.795______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbol d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 36. An objective lens system for an endoscope according to claim 32 having the following numerical data:
- ______________________________________r.sub.1 = .infin. (aspherical surface)d.sub.1 = 0.2743 n.sub.1 = 1.51633 .nu..sub.1 = 64.15r.sub.2 = 0.8373d.sub.2 = 1.5683r.sub.3 = 4.2174d.sub.3 = 0.5485 n.sub.2 = 1.59270 .nu..sub.2 = 35.29r.sub.4 = -10.5058d.sub.4 = 0.2194 n.sub.3 = 1.83400 .nu..sub.3 = 37.16r.sub.s = -3.4706d.sub.s = 0.0549r.sub.6 = .infin. (stop)d.sub.6 = 0.0549r.sub.7 = 2.6304d.sub.7 = 0.6034 n.sub.4 = 1.62041 .nu..sub.4 = 60.27r.sub.8 = -0.7752d.sub.8 = 0.2194 n.sub.5 = 1.80518 .nu..sub.5 = 25.43r.sub.9 = -1.4995d.sub.9 = 0.8795r.sub.10 = -2.2103d.sub.10 = 0.2743 n.sub.6 = 1.84666 .nu..sub.6 = 23.88r.sub.11 = -4.1560 (aspherical surface)f = 1, 2.delta. = 99.978.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.15461 .times. 10.sup.-1F = 0.13610 .times. 10.sup.-2aspherical surface coefficient of 11th surfaceP = 1, E = 0.14239, F = 0.19039A.sub.F = -0.00158, A.sub.R = 0.00701A.sub.F /A.sub.F = -0.22539, E.sub.F = 0.01546E.sub.B = 0.1424, E.sub.B /E.sub.F = 9.211f.sub.4 = -5.961______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of the respective lenses.
- 37. An objective lens system for an endoscope according to claim 32, wherein said front lens unit has negative refractive power, said rear lens unit has positive refractive power and said stop located between said front and rear lens units in the vicinity of the front focal point.
- 38. An objective lens system for an endoscope according to claim 37 wherein said front lens unit comprises a negative meniscus lens component convex toward the object side, said rear lens unit comprises a positive meniscus lens component convex toward the image side, a positive lens component, a positive cemented doublet, and a positive lens component, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the condition shown below: ##EQU12## where, reference, symbol f represents the focal length of the lens system as a whole, reference symbol f, represents the focal length of said front lens unit, reference symbol D represents the distance form the rearmost surface of said front lens unit to the foremost surface of said rear lens unit, reference symbol C represents the inverse number of the radius of curvature of the aspherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 39. An objective lens system for an endoscope according to claim 37 wherein said front lens unit comprises a negative meniscus lens component convex toward the object side, said rear lens unit comprises a positive lens component, and a cemented doublet, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the condition shown below: ##EQU13## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol f, represents the focal length of said front lens unit, reference symbol D represents the distance from the rearmost surface of said front lens unit to the foremost surface of said rear lens unit, reference symbol O represents the inverse number of the radius of curvature of the aspherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 40. An objective lens system for an endoscope according to claim 37 wherein said front lens unit comprises two negative lens components each having a concave surface on the image side, said rear lens unit comprises a positive lens component, a positive lens component, a positive cemented doublet, and a positive lens component having a convex surface on the object side, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the conditions shown below: ##EQU14## where, reference symbol f.sub.F represents the focal length of said front lens group, reference symbol f represents the focal length of the lens system as a whole, reference symbol c represents the inverse number of the radius of curvature of the aspherical surface which is in contact with said aspherical surface on the optical axis, reference symbol P represents a parameter repesenting the shape of said aspherical surface, and reference symbols B, E, F, G, . . . respectively represent the aspherical surface coefficients of the second power, fourth power, sixth power eighth power and so on.
- 41. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, said front lens unit comprising a negative lens component concave toward the image side arranged so that the surface on the image side thereof is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis, and said rear lens unit comprising a plurality of lens component including a positive cemented doublet one of said lens components being arranged so that the surface on the image side thereof is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis, the air space between the surface on the extreme image side of said front lens unit and said stop being constant.
- 42. An objective lens system for an endoscope according to claim 41 fulfilling the following conditions:
- A.sub.F.A.sub.R <0
- 0.01<.vertline.A.sub.F /A.sub.R .vertline.<10
- where, reference symbol A.sub.F represents the sum of coefficients of astigmatism of said aspherical surfaces provided in said front lens unit, and reference symbol A.sub.R represents the sum of coefficients of astigmatism of said aspherical surfaces provided in said rear lens unit. 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 aspherical surface coefficients of the second power, fourth power, sixth power eighth power and so on.
- 43. An objective lens system for an endoscope according to claim 42, wherein a meniscus lens component concave toward the image side is arranged on the extreme object side of said front lens unit, a meniscus lens component concave toward the object side is arranged on the extreme image side of said rear lens unit, a positive lens component is arranged on the extreme image side of said front lens unit, a positive lens component is arranged on the extreme image side of said front lens unit, a positive lens component is arranged on the extreme object side of said rear lens unit, and a stop is arranged between said positive lenses arranged in front lens unit and rear lens unit.
- 44. An objective lens system for an endoscope according to claim 43 wherein said front lens unit comprises a negative lens component having a concave surface on the image side, and a positive cemented doublet, said rear lens group comprises a positive cemented doublet, and a meniscus lens component convex toward the image side, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the condition shown below: ##EQU15## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol c represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 45. An objective lens system for an endoscope according to claim 44 wherein the surface on the image side of said meniscus lens component in said rear lens unit is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis.
- 46. An objective lens system for an endoscope according to claim 45 further fulfilling the following condition:
- f.sub.4 <-3f
- where, reference symbol f.sub.4 represents the focal length of said meniscus lens component constituting said rear lens unit.
- 47. An objective lens system for an endoscope according to claim 44 having the following numerical data:
- ______________________________________r.sub.1 = -10.5764d.sub.1 = 0.2644 n.sub.1 = 1.51633 .nu..sub.1 = 64.15r.sub.2 = 0.8576 (aspherical surface)d.sub.2 = 1.4849r.sub.3 = 4.0495d.sub.3 = 0.5887 n.sub.2 = 1.5927 .nu..sub.2 = 35.29r.sub.4 = -3.11d.sub.4 = 0.015r.sub.4 = .infin. (stop)d.sub.s = 0.0017r.sub.6 = 2.5394d.sub.6 = 0.5817 n.sub.3 = 1.62041 .nu..sub.3 = 60.27r.sub.7 = -0.783d.sub.7 = 0.2115 n.sub.4 = 1.80518 .nu..sub.4 = 25.43r.sub.8 = -1.4395d.sub.8 = 0.7633r.sub.9 = -2.2144d.sub.9 = 0.2712 n.sub.5 = 1.84666 .nu..sub.5 = 23.88r.sub.10 = -3.4775 (aspherical surface)f = 1, 2.omega. = 105.97.degree.aspherical surface coefficient and 2nd surfaceP = 1, E = -0.6762 .times. 10.sup.-1F = -0.98299 .times. 10.sup.-1aspherical surface coefficient of 10th surfaceP = 1, E = 0.28784F = -0.63525 .times. 10.sup.-1A.sub.F = -0.00404, A.sub.F = 0.01655A.sub.F /A.sub.F = -0.2441, E.sub.F = -0.06762E.sub.B = 0.28784, .vertline.E.sub.B /E.sub.F .vertline. = 4.257f.sub.4 = -7.987______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thickness of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 48. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, said front lens unit comprising a negative meniscus lens component convex toward the object side arranged that the surface of the image side thereof is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis, and said rear lens unit comprising plurality of lens components including a positive cemented doublet one of said lens components being arranged so that the surface on the object side thereof is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis, the air space between the surface on the extreme image side of said front lens unit and said stop being constant.
- 49. An objective lens system for an endoscope according to claim 48 fulfilling the following conditions:
- A.sub.F .multidot.A.sub.R <0
- 0.01<.vertline.A.sub.F /A.sub.R .vertline.<10
- where, reference symbol A.sub.F represents the sum of coefficients of astigmatism of said aspherical surfaces provided in said front lens unit, and reference symbol A.sub.R represents the sum of coefficients of astigmatism of said aspherical surfaces provided in said rear lens unit.
- 50. An objective lens system for an endoscope according to claim 49, wherein said front lens unit has negative refractive power, said rear lens unit has positive refractive power and said stop located between said front and rear lens units in the vicinity of the front focal point.
- 51. An objective lens system for an endoscope according to claim 50 wherein said rear lens unit comprises a positive meniscus lens component convex toward the image side, a positive lens component, a positive cemented doublet, and a positive lens component, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the condition shown below: ##EQU16## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol f.sub.1 represents the focal length of said front lens unit, reference symbol D represents the distance from the rearmost surface of said front lens unit to the foremost surface of said rear lens unit reference symbol C represents the inverse number of the radius of curvature of the aspherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 52. An objective lens system for an endoscope according to claim 50 wherein said rear lens unit comprises a positive lens component, and a cemented doublet, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the conditions shown below: ##EQU17## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol O represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 53. An objective lens system for an endoscope according to claim 52 further fulfilling the following conditions:
- .vertline.f.sub.1 .vertline.>1.8f
- D>1.5f
- where, reference symbol f.sub.1 represents the focal length of said front lens unit, and reference symbol D represents the distance from the rearmost surface of said front lens unit to the foremost surface of said rear lens unit.
- 54. An objective lens system for an endoscope according to claim 53 wherein the surface on the object side of said positive cemented doublet constituting said rear lens unit is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis.
- 55. An objective lens system for an endoscope according to claim 54 having the following numerical data:
- ______________________________________r.sub.1 = 4.1406d.sub.1 = 0.8005 n.sub.1 = 1.88300 .nu..sub.1 = 40.76r.sub.2 = 1.1345 (aspherical surface)d.sub.2 = 4.1302r.sub.3 = .infin. (stop)d.sub.3 = 0.3680r.sub.4 = 6.9159d.sub.4 = 0.8469 n.sub.2 = 1.69680 .nu..sub.2 = 55.52r.sub.5 = -4.1736d.sub.5 = 1.7075r.sub.6 = 2.8187 (aspherical surface)d.sub.6 = 1.9723 n.sub.3 = 1.64000 .nu..sub.3 = 60.09r.sub.7 = -1.4348d.sub.7 = 0.5801 n.sub.4 = 1.84666 .nu..sub.4 = 23.88r.sub.8 = -4.0238f = 1, 2.omega. = 66.482.degree.aspherical surface coefficient of 2nd surfaceP = 1, E = -0.92345 .times. 10.sup.-1F = 0.33387 .times. 10.sup.-1aspherical surface coefficient of 6th surfaceP = 1, E = -0.79246 .times. 10.sup.-2F = 0.36822 .times. 10.sup.-2A.sub.F = -0.01433, A.sub.R = 0.00246A.sub.F /A.sub.R = -5.8252f.sub.1 = -2.002, D.sub.1 = 4.498______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 56. An objective lens system for an endoscope according to claim 50 wherein said front lens unit comprises two negative lens components each having a concave surface on the image side, said rear lens unit comprises a positive lens component, a positive lens component, a positive cemented doublet, and a positive lens component having a convex surface on the object side, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the conditions shown below: ##EQU18## where, reference symbol f.sub.F represents the focal length of said front lens group, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 57. An objective lens system for an endoscope according to claim 56 wherein the surface on the object side of said rearmost lens component in said rear lens unit is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis.
- 58. An objective lens system for an endoscope according to claim 57 having the following numerical data:
- ______________________________________r.sub.1 = 13.333d.sub.1 = 0.7333 n.sub.1 = 1.49109 .nu..sub.1 = 57.00r.sub.2 = 3.6471 (aspherical surface)d.sub.2 = 1.0730r.sub.3 = 2240.3652d.sub.3 = 2.1988 n.sub.2 = 1.78800 .nu..sub.2 = 47.43r.sub.4 = 1.2225d.sub.4 = 1.0494r.sub.5 = .infin. (stop)d.sub.5 = 0.1241r.sub.6 = -77.6317d.sub.6 = 1.2380 n.sub.3 = 1.58913 .nu..sub.3 = 60.97r.sub.7 = -1.9899d.sub.7 = 0.7377r.sub.8 = -6.0607d.sub.8 = 1.3244 n.sub.4 = 1.58913 .nu..sub.4 = 60.97r.sub.9 = -2.7972d.sub.9 = 0.1333r.sub.10 = 4.3283d.sub.10 = 2.1067 n.sub.5 = 1.61800 .nu. .sub.5 = 63.38r.sub.11 = -2.2200d.sub.11 = 0.4667 n.sub.6 = 1.84666 .nu..sub.6 = 23.90r.sub.12 = -16.4147d.sub.12 = 0.9325r.sub.13 = 2.0725 (aspherical surface)d.sub.13 = 1.9851 n.sub.7 = 1.49109 .nu..sub.7 = 57.00r.sub.14 = .infin.f = 1, 2.omega. = 115.9.degree.aspherical surface coefficient of 2nd surfaceP = 1, E = -0.11242 .times. 10.sup.-1, F = 0aspherical surface coefficient of 13th surfaceP = 1, E = -0.54135 .times. 10.sup.-1, F = 0A.sub.F = -0.01753, A.sub.R = 0.05767A.sub.F /A.sub.R = -0.30397, f.sub.F = -1.151______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of respective lenses.
- 59. An objective lens system for an endoscope according to claim 50 wherein a meniscus lens component concave toward the image side is arranged on the extreme object side of said front lens unit, a meniscus lens component concave toward the object side is arranged on the extreme image side of said rear unit, a positive lens component is arranged on the extreme image side of said front lens unit, a positive lens component is arranged on the extreme object side of said rear lens unit, and a stop is arranged between said positive lenses arranged in front lens unit and rear lens unit.
- 60. An objective lens system for an endoscope according to claim 59 wherein said front lens unit comprises a negative lens component having a concave surface on the image side, and a positive cemented doublet, said rear lens group comprises a positive cemented doublet, and a meniscus lens component convex toward the image side, each of said aspherical surfaces is expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and optical axis is designatedas the y axis and, moveover, each of said aspherical surfaces fulfills the condition shown below: ##EQU19## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on 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 aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 61. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, said front lens unit comprising a plane-parallel transparent plate on the object side of which a portion is provided at a distance from the optical axis which is aspherical in shape, the curvature of which is made gradually stronger as the distance increases from the optical axis, and said rear lens unit comprising two positive lens components arranged so that the lens surfaces facing each other are convex and the surface on the object side of the positive lens component on the image side thereof is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis.
- 62. An objective lens system for an endoscope according to claim 61 wherein said front lens unit comprises a plane-parallel transparent plate on the object side of which is provided with a portion at a distance from the optical axis which is aspherical, said rear lens unit comprising a positive lens cemented on to the image side of said plane-parallel transparent plate, and a positive lens component having an aspherical surface on the object side, each of said aspherical surfaces being expressed by the formula shown below when the optical axis is designated as the x axis and a straight line perpendicular to the optical axis and passing the intersecting point between said aspherical surface and the optical axis is designated as the y axis and, moreover, each of said aspherical surfaces fulfills the condition shown below: ##EQU20## where, reference symbol f represents the focal length of the lens system as a whole, reference symbol C represents the inverse number of the radius of curvature of the spherical surface which is in contact with said aspherical surface on the optical axis, reference symbol P represents a parameter representing the shape of said aspherical surface, the reference symbols B, E, F, G, . . . respectively represent the aspherical surface coefficients of the second power, fourth power, sixth power, eighth power and so on.
- 63. An objective lens system for an endoscope according to claim 62 having the following numerical data:
- ______________________________________r.sub.1 = .infin. (aspherical surface)d.sub.1 = 0.5725 n.sub.1 = 1.51633 .nu..sub.1 = 64.15r.sub.2 = .infin. (stop)d.sub.2 = 1.3991 n.sub.2 = 1.80610 .nu..sub.2 = 40.95r.sub.3 = -1.2000d.sub.3 = 0.5436r.sub.4 = 1.5780 (aspherical surface)d.sub.4 = 1.2126 n.sub.3 = 1.80610 .nu..sub.3 = 40.95r.sub.5 = .infin.f = 1, 2.omega. = 81.502.degree.aspherical surface coefficient of 1st surfaceP = 1, E = 0.12374, F = 0aspherical surface coefficient of 4th surfaceP = 1, E = -0.87329 .times. 10.sup.-1F = -0.18044 .times. 10.sup.-1A.sub.F = -0.00267, A.sub.R = 0.01139A.sub.F /A.sub.R = -0.23442______________________________________
- where, reference symbols r.sub.1, r.sub.2, . . . respectively represent radii of curvature of respective lens surfaces, reference symbols d.sub.1, d.sub.2, . . . respectively represent thicknesses of respective lenses and airspaces between respective lenses, reference symbols n.sub.1, n.sub.2, . . . respectively represent refractive indices of respective lenses, and reference symbols .nu..sub.1, .nu..sub.2, . . . respectively represent Abbe's numbers of the respective lenses.
- 64. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, and front lens unit comprising a negative lens component concave toward the image side and at least one lens surface of said front lens unit being formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis, and said rear lens unit comprising a plurality of lens components including a positive cemented doublet, one of said lens components being arranged so that the surface on the object side thereof is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis, the air space between the surface on the extreme image side of said front lens unit and said stop being constant.
- 65. An objective lens system for an endoscope according to claim 64, wherein said negative lens component of said front lens unit is arranged that the surface on the object side thereof is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis.
- 66. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, said front lens unit comprising a negative lens component concave toward the image side and at least one lens surface of said front lens unit being formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis, and said rear lens unit comprising a plurality of lens components including a positive cemented doublet, one of said lens components being arranged so that the surface on the image side thereof is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis, the air space between the surface on the extreme image side of said front lens unit and said stop being constant.
- 67. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, said front lens unit comprising a negative lens component concave toward the image side and at least one lens surface of said front lens unit being formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis, and said rear lens unit comprising a plurality of lens components including a positive cemented doublet, one of said lens components being arranged so that the surface on the image side thereof is formed as an aspherical surface having portions whose curvature is made gradually stronger as they are farther from the optical axis, the air space between the surface on the extreme image side of said front lens unit and said stop being constant.
- 68. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, said front lens unit comprising a negative lens components concave toward the image side and at least one lens surface of said front lens unit being formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis, and said rear lens unit comprising plurality of lens components including a positive cemented doublet, one of said lens components being arranged so that the surface on the object side thereof is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis, the air space between the surface on the extreme image side of said front lens unit and said stop being constant.
- 69. An objective lens system for an endoscope according to claim 68, wherein said negative lens component of said front lens unit is arranged that the surface of the image side thereof is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis.
- 70. An objective lens system for an endoscope comprising a front lens unit, a rear lens unit, and a stop located between said front and rear lens units, said front lens unit comprising an optical element having an aspherical surface, the curvature of which is made gradually stronger as the distance increases from the optical axis, and said rear lens unit comprising two positive lens components arranged so that the lens surfaces facing each other are convex and at least one lens surface of said two positive lens components is formed as an aspherical surface having portions whose curvature is made gradually weaker as they are farther from the optical axis.
Priority Claims (1)
Number |
Date |
Country |
Kind |
60-2064 |
Jan 1985 |
JPX |
|
Parent Case Info
This is a continuation of application Ser. No. 816,869, filed Jan. 7, 1986, which was abandoned upon the filing hereof.
US Referenced Citations (4)
Foreign Referenced Citations (4)
Number |
Date |
Country |
2748516 |
Jul 1978 |
DEX |
3214544 |
Nov 1982 |
DEX |
49-121547 |
Nov 1974 |
JPX |
57-173810 |
Oct 1982 |
JPX |
Continuations (1)
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Number |
Date |
Country |
Parent |
816869 |
Jan 1986 |
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