Endoscope for oblique viewing

{
  "publication_number": "US2010076268A1",
  "country": "US",
  "kind": "A1",
  "title": "Endoscope for oblique viewing",
  "abstract": "An endoscope for oblique viewing including an image pickup device, a front lens group having a positive refractive power, a prism disposed on the CCD side of the front lens group, and a rear lens group disposed on the CCD side of the prism and having a positive refractive power.",
  "claims": [
    "1. An endoscope for oblique viewing comprising: an image pickup device; a front lens group having a positive refractive power; a visual field direction converting element disposed on the image pickup device side of the front lens group; and a rear lens group disposed on the image pickup device side of the visual field direction converting element and having a positive refractive power. 2. The endoscope for oblique viewing according to claim 1; further comprising a first lens unit frame in which a first lens unit having the front lens group is disposed, and a second lens unit frame in which a second lens unit having the rear lens group is disposed, wherein the first lens unit can be made eccentric relative to the second lens unit. 3. The endoscope for oblique viewing according to claim 2, wherein optical adjustment of at least one of the first lens unit and the second lens unit can be performed by performing an operation for rotating the one of the lens units relative to the other lens unit, an operation for shifting the one of the lens units relative to the other lens unit, an operation for tilting the one of the lens units relative to the other lens unit, or a combination of some of the operations. 4. The endoscope for oblique viewing according to claim 2, further comprising a third lens unit frame in which a third lens unit having the image pickup device is disposed, wherein at least one of the first lens unit, the second lens unit and the third lens unit can be made eccentric relative to the other lens units. 5. The endoscope for oblique viewing according to claim 4, wherein optical adjustment of at least one of the first lens unit, the second lens unit and the third lens unit can be performed by performing an operation for rotating the one of the lens units relative to the other lens units, an operation for shifting the one of the lens units relative to the other lens units, an operation for tilting the one of the lens units relative to the other lens units, or a combination of some of the operations. 6. The endoscope for oblique viewing according to claim 1, wherein if the lens distance between the front lens group and the rear lens group in an objective optical system having the visual field direction converting element is d; the focal length of the entire system is f; the maximum image height is IH, 1.1<d/f<2.1 and 1.4<d/IH<3.0 are satisfied. 7. The endoscope for oblique viewing according to claim 1, wherein if the lens distance from the first lens surface in the objective optical system having the visual field direction converting element to the object-side surface of the visual field direction converting element is D 1; the lens distance from the image-side surface of the visual field direction converting element to the image plane is D 2; and the focal length of the entire objective optical system is f, 1.4<D 1 /f<3.1 and 2.0<D 2 /f<3.9 are satisfied. 8. The endoscope for oblique viewing according to claim 1, wherein if the lens distance from the first lens surface in the objective optical system having the visual field direction converting element to the object-side surface of the visual field direction converting element is D 1; and the lens distance from the image-side surface of the visual field direction converting element to the image plane is D 2, 0.4<D 1 /D 2 <1.0 is satisfied. 9. The endoscope for oblique viewing according to claim 1, wherein if the focal length of the front lens group is G 1 f; the focal length of the rear lens group is G 2 f; and the focal length of the entire objective optical system is f, 1.5<G 1 f /f<6.0 and 3.0<G 2 f /f<6.0 are satisfied. 10. The endoscope for oblique viewing according to claim 1, wherein if the focal length of the front lens group is G 1 f; the focal length of the rear lens group is G 2 f; and the focal length of the entire objective optical system is f, 0.3<G 1 f /G 2 f <2.0 is satisfied. 11. The endoscope for oblique viewing according to claim 1, wherein the front lens group has a negative lens group including at least a negative lens and a positive lens group including at least a positive lens. 12. The endoscope for oblique viewing according to claim 11, wherein if the focal length of the negative lens group in the front lens group is f 1; the focal length of the positive lens group in the front lens group is f 2; and the focal length of the entire objective optical system is f, 0.5<|f 1 |/f<1.1 and 1.3<f 2 /f<2.8 are satisfied. 13. The endoscope for oblique viewing according to claim 1, wherein the visual field direction converting element comprises a prism. 14. The endoscope for oblique viewing according to claim 13, further comprising a brightness stop disposed in the front lens group. 15. The endoscope for oblique viewing according to claim 14, wherein the front lens group and the brightness stop are integrally configured in the first lens unit. 16. The endoscope for oblique viewing according to claim 1, further comprising an illumination optical system disposed on the proximal end portion side of the endoscope for oblique viewing relative to the objective optical system. 17. The endoscope for oblique viewing according to claim 16, wherein if an oblique-viewing angle is θ 1 and an illumination angle is θ 2, 0°≦θ 1 ≦20° and 0°≦θ 2 ≦25° are satisfied. 18. The endoscope for oblique viewing according to claim 16, wherein if the distance between a center of the objective optical system and a center of the illumination optical system (optical axis) is L, 3 mm≦L≦5 mm is satisfied. 19. An endoscope for oblique viewing comprising: an image pickup device; a first lens unit frame in which a first lens unit having a front lens group having a positive refractive power is disposed; a second lens unit frame in which a second lens unit having a prism disposed on the image pickup device side of the front lens group and provided as a visual field direction converting element and a rear lens group disposed on the image pickup device side of the prism and having a positive refractive power is disposed; third lens unit frame in which a third lens unit having the image pickup device is disposed; and an illumination optical system disposed on the proximal end portion side of the endoscope for oblique viewing relative to the objective optical system, wherein if the lens distance between the front lens group and the rear lens group is d; the focal length of the entire system is f; the maximum image height is IH; the lens distance from the first lens surface in the objective optical system to the object-side surface of the visual field direction changing element is D 1; the lens distance from the image-side surface of the visual field direction changing element to the image plane is D 2; the focal length of the front lens group is G 1 f; the focal length of the rear lens group is G 2 f; and the focal length of the entire objective optical system is f, 1.2<d/f<2.0; 1.5<d/IH<2.7; 1.6<D 1 /f<2.8; 2.3<D 2 /f<3.6; 0.4<D 1 /D 2 <1.0; 1.5<G 1 f /f<6.0; 3.0<G 2 f /f<6.0; and 0.3<G 1 f /G 2 f <2.0 are satisfied."
  ],
  "cpc": [
    "G02B 23/243",
    "A61B 1/00177",
    "A61B 1/00179",
    "A61B 1/00183",
    "A61B 1/05",
    "G02B 23/2476",
    "G02B 7/023"
  ],
  "assignees": [
    "OLYMPUS MEDICAL SYSTEMS CORP"
  ],
  "filing_date": "2009-09-21",
  "publication_date": "2010-03-25",
  "priority_date": "2008-09-19",
  "application_number": "US-56324809-A",
  "family_id": "41165392",
  "citations": [
    "US4037938A",
    "US4877314A",
    "US5569162A",
    "US7160249B2",
    "US7280283B1"
  ]
}