Variable magnification endoscope

• US 4,704,007 A
• Filed: 03/30/1983
• Issued: 11/03/1987
• Est. Priority Date: 03/25/1980
• Status: Expired due to Term

• Current Assignee: Endoptics, Inc.
• Original Assignee: Jan Hoogland, John K. Landre
• Inventors: Hoogland, Jan, Landre, John K.
• Primary Examiner(s): Corbin, John K.
• Assistant Examiner(s): Edmondson, D.
• Application Number:
  US06/480,521
• Time in Patent Office: 1,679 Days
• Field of Search: 128/4, 128/6, 350/414, 350/507, 350/523, 350/525, 350/519, 351/221
• US Class Current: 359/380
• CPC Class Codes: G02B 23/2469 using optical fibres

Abstract

An endoscope whose magnification may be continuously varied from zero to a microscopic magnification of 40× or more while providing full correction for aberrations at widely different magnifications. The objective comprises a positive lens group in a microscope objective configuration, and a front group which typically includes a negative lens generally near the focal plane of the positive lens group. To achieve high magnification, the objective is moved away from the transfer optics, and placed in contact with the object to be viewed. In such a configuration, the positive lens group functions as a microscope objective while the negative lens group'"'"'s contribution to the aberrations is small. At low magnification, the negative lens group cooperates with the positive lens group to provide a wide angle lens. Pupil stabilization is achieved by placing the physical stop so that when the endoscope is used in the microscope mode, the physical stop between the positive and negative lens groups is ineffective or marginally effective. This permits the maximum numerical aperture consistent with the physical diameter of the positive lens group. However, the physical stop between the positive and negative lens groups comes into play when the object plane moves away from the negative lens group. The field lens located at the image plane receives the marginal chief ray at a nearly constant small angle over the entire range of magnification. This allows image transfer to be achieved with conventional means such as alternating field and relay lenses.

Claims

1. An endoscope comprising:

optical transfer means defining an image plane;

a negative lens at a distal end of said endoscope and having a front surface;

a positive lens between said negative lens and said image plane;

said positive lens and said negative lens being characterized by respective first and second sets of optical parameters, each of said sets of optical parameters including geometrical parameters, namely surface radii and surface locations along an optical axis, and optical material parameters, namely refractive index and dispersion values, said first and second sets of optical parameters defining respective powers P(pos) and P(neg) of said positive and negative lenses;

means for coupling said positive lens and said negative lens to one another to define an objective characterized by an overall power P(obj); and

slidable support means for permitting said objective to move with respect to said image plane along said optical axis over a range of positions including a first position of maximum magnification wherein an object proximate the front surface of said negative lens is imaged in said image plane, and a second position of relatively lower magnification wherein an object at a substantial distance from said front surface of said negative lens is imaged in said image plane;

said first and second sets of optical parameters being chosen such that said objective in said first position operates as a substantially fully corrected microscope objective and said objective in said second position operates as a wide angle lens having substantially fully corrected field aberrations;

the operation of said objective as a substantially fully corrected microscope objective being largely determined by said first set of optical parameters with said negative lens contributing little to the aberrations and overall power of said objective, the ratio P(pos)/P(obj) being between 0.8 and 1.4;

said second set of optical parameters being chosen to correct field aberrations of said objective when said objective operates as a wide angle lens.

2. The invention of claim 1 wherein the ratio P(neg)/P(obj) is between -1.2 and -0.4.

3. The invention of claim 1, and further comprising an aperture stop located at a position that is optically equivalent to a position between said positive and negative lenses such that the chief ray in a marginal bundle intersects said image plane in a direction approximately parallel to said optical axis for image formation in said second position of low magnification.

4. The invention of claim 3 wherein said position between said positive and negative lenses is displaced from the focal plane of said positive lens so that the marginal ray in said marginal bundle intersects said image plane in a direction substantially parallel to said optical axis.

5. An objective for placement at a leading end of an endoscope comprising:

magnification means characterized by an optic axis; and

a front group including means defining a front surface;

said front group and said magnification means being characterized by respective first and second sets of optical parameters chosen such that the objective operates as a substantially fully corrected microscope objective for magnification of an object located at a position proximate said front surface, and the objective operates as a wide angle lens having substantially fully corrected field aberrations for imaging of an object located a substantial distance in front of said front surface, each of said sets of optical parameters including geometrical parameters, namely surface radii and surface locations along said optical axis, and optical material parameters, namely refractive index and dispersion values, said first and second sets of optical parameters defining first, second, and third powers of said magnification means, said front group, and the objective as a whole, respectively;

the operation of said objective as a substantially fully corrected microscope objective being largely determined by said first set of optical parameters with said front group contributing little to the aberrations and overall power of said objective, the ratio of said first power to said third power being between 0.8 and 1.4;

said second set of optical parameters being chosen to correct field aberrations of said objective when said objective operates as a wide angle lens.

6. The invention of claim 5 wherein said position proximate said front surface is a position contacting said front surface.

7. The invention of claim 5 wherein said magnification means comprises a positive lens group in a microscope objective configuration.

8. The invention of claim 5 wherein said front group comprises a negative lens.

9. The invention of claim 8 wherein the ratio of said second power to said third power is between -1.2 and -0.4.

10. The invention of claim 5 or 6 or 8 wherein said front group includes a stop means located such that the marginal chief ray is approximately parallel to the optic axis for an object at a substantial distance ahead of said front surface.

11. The invention of claim 5 or 6 wherein said front group comprises a negative lens and an aperture stop located physically between said magnification means and said negative lens.

12. An endoscope comprising:

14. The invention of claim 12 wherein said position proximate said front surface is a position contacting said front surface.

15. The invention of claim 12 wherein said magnification means comprises a positive lens group in a microscope objective configuration.

16. The invention of claim 12 wherein said front group comprises a negative lens.

17. The invention of claim 12 or 13 or 15 wherein said front group includes stop means located such that the marginal chief ray is approximately parallel to the optic axis for an object at a substantial distance ahead of said front surface.

18. The invention of claim 12 or 13 wherein said front group comprises a negative lens and an aperture stop located at a position between said magnification means and said negative lens.

19. The invention of claim 17 wherein said position between said magnification means and said negative lens is displaced from the focal plane of said magnification means so that the marginal ray in the marginal bundle is substantially parallel to said optical axis for an object at a substantial distance ahead of said front surface.

21. The invention of claim 19 wherein the ratio of said second power to said third power is between -1.2 and -0.4

22. The invention of claim 19 wherein said optical parameters provide generally fully corrected field aberrations at positions intermediate said first and second positions.

23. The invention of claim 19 wherein said front group comprises a negative lens and an aperture stop located physically between said magnification means and said negative lens.

24. The invention of claim 5 or 12 or 19 wherein said front group includes means defining a peripheral surface having portions with normal axis at an acute angle with respect to said optic axis to permit illumination of said object located at said position proximate said front surface.

25. The invention of claim 23 wherein said peripheral surface is frustoconical.

27. The invention of claim 25 wherein said positive lens is characterized by a focal plane located between said positive lens and the front surface of said negative lens, and further comprising an aperture stop located at a position that is optically equivalent to a position in the vicinity of said focal plane such that the marginal chief ray intersects said image plane in a direction approximately parallel to said optical axis for image formation in said second position of low magnification.

29. The invention of claim 27 wherein said position proximate said front surface is a position contacting said front surface.

30. The invention of claim 27 wherein said magnification means comprises a positive lens group in a microscope objective configuration.

31. The invention of claim 27 wherein said front group comprises a negative lens and the ratio of said second power to said third power is between -1.2 and -0.4.

32. The invention of claim 27 wherein said front group includes means defining a peripheral surface having portions with normal axes at an acute angle with respect to said optic axis to permit illumination of said object located at said position proximate said front surface.

33. The invention of claim 31 wherein said peripheral surface is frustoconical.

34. The invention of claim 31 wherein said front group comprises a negative lens and the ratio of said second power is between -1.2 and -0.4.

35. The invention of claim 27 or 28 or 30 wherein said front group includes stop means located such that the marginal chief ray is approximately parallel to the optic axis for an object at a substantial distance ahead of said front surface.

36. The invention of claim 27 or 28 wherein said front group comprises a negative lens and an aperture stop located physically between said magnification means and said negative lens.

37. The invention of claim 31 or 32 wherein said front group comprises a negative lens and an aperture stop located physically between said magnification means and said negative lens.

39. The invention of claim 37 wherein said position proximate said front surface is a position contacting said front surface.

40. The invention of claim 37 wherein said magnification means comprises a positive lens group in a microscope objective configuration.

41. The invention of claim 37 wherein said front group includes means defining a peripheral surface having portions with normal axes at an acute angle with respect to said optic axes to permit illumination of said object located at said position proximate said front surface.

42. The invention of claim 40 wherein said peripheral surface is frustoconical.

43. The invention of claim 31 or 32 or 38 wherein said front group includes stop means located such that the marginal chief ray is approximately parallel to the optic axis for an object at a substantial distance ahead of said front surface.

45. The invention of claim 43 wherein said optical parameters provide generally fully corrected field aberrations at positions intermediate said first and second positions.

46. The invention of claim 43 wherein said front group comprises a negative lens and the ratio of said second power to said third power is between -1.2 and -0.4.

47. The invention of claim 43 wherein said front group comprises a negative lens and an aperture stop located physically between said magnification means and said negative lens.

49. The invention of claim 47 wherein said peripheral surface is frustoconical.

13. optical transfer means defining an image plane;

magnification means characterized by an optic axis;

a front group including means defining a front surface;

means for coupling said magnification means and said front group to one another to define an objective; and

slidable support means for permitting said objective to move with respect to said image plane along said optical axis over a range of positions including a first position of maximum magnification wherein an object located at a position proximate said front surface is imaged in said image plane, and a second position of relatively lower magnification wherein an object at a substantial distance from said front surface is imaged in said image plane;

said magnification means and said front group being characterized by respective first and second sets of optical parameters chosen such that said objective operates as a substantially fully corrected microscope objective for said first position and as a wide angle lens that has substantially fully corrected field aberrations for said second position, each of said sets of optical parameters including geometrical parameters, namely surface radii and surface locations along said optical axis, and optical material parameters, namely refractive index and dispersion values, said first and second sets of optical parameters defining first, second, and third powers of said magnification means, said front group, and the objective as a whole, respectively;

the operation of said objective as a substantially fully corrected microscope objective being largely determined by said first set of optical parameters with said front group contributing little to the aberrations and overall power of said objective, the ratio of said first power to said third power being between 0.8 and 1.4;

said second set of optical parameters being chosen to correct field aberrations of said objective when said objective operates as a wide angle lens.

20. In an endoscope having optical transfer means defining an image plane, an objective movable relative to said image plane along an optic axis, the objective being movable between first and second widely spaced positions to permit normal microscopy at large magnification and normal endoscopy at relatively small magnification, an improved objective comprising:

a positive lens group in a microscope objective configuration; and

a front group including a front element and an aperture stop located between said front element and said positive lens group;

said aperture stop being located so as to be largely ineffective when said objective is in said first position of large magnification and so as to maintain the marginal chief ray approximately parallel to the optic axis for an object at a substantial distance ahead of said front surface;

said positive lens group and said front group being characterized by respective first and second sets of optical parameters chosen such that said objective operates as a substantially fully corrected microscope objective for said first position and as a wide angle lens that has substantially fully corrected field aberrations for said second position, each of said sets of optical parameters including geometrical parameters, namely surface radii and surface locations along said optical axis, and optical material parameters, namely refractive index and dispersion values, said first and second sets of optical parameters defining first, second, and third powers of said positive lens group, said front group, and the objective as a whole, respectively;

the operation of said objective as a substantially fully corrected microscope objective being largely determined by said first set of optical parameters with said front group contributing little to the aberrations and overall power of said objective, the ratio of said first power to said third power being between 0.8 and 1.4;

said second set of optical parameters being chosen to correct field aberrations of said objective when said objective operates as a wide angle lens.

26. An endoscope having distal and proximal ends, comprising:

optical transfer means for transferring at fixed magnification an image formed at an image plane to said proximal end, said image plane being fixed relative to said optical transfer means;

a negative lens at said distal end, said negative lens having a front surface;

a positive lens between said negative lens and said image plane;

said positive lens and said negative lens being characterized by respective first and second sets of optical parameters, each of said sets of optical parameters including geometrical parameters, namely surface radii and surface locations along an optical axis, and optical material parameters, namely refractive index and dispersion values, said first and second sets of optical parameters defining respective powers P(pos) and P(neg) of said positive and negative lenses;

means for rigidly coupling said positive lens and said negative lens to one another while preventing relative movement therebetween to define an objective characterized by an overall power P(obj); and

slidable support means for permitting said objective to move with respect to said image plane over a range along said optical axis, said range including a first position of maximum magnification wherein an object proximate the front surface of said negative lens is imaged in said image plane, and a second position of relatively lower magnification wherein an object at a substantial distance from said front surface of said negative lens is imaged in said image plane;

said first and second sets of optical parameters being chosen such that said objective in said first position operates as a substantially fully corrected microscope objective and said objective in said second position operates as a wide angle lens having substantially fully corrected field aberrations;

the operation of said objective as a substantially fully corrected microscope objective being largely determined by said first set of optical parameters with said negative lens contributing little to the aberrations and overall power of said objective, the ratio P(pos)/P(obj) being between 0.8 and 1.4;

said second set of optical parameters being chosen to correct field aberrations of said objective when said objective operates as a wide angle lens.

28. An objective for placement at a leading end of an endoscope comprising:

magnification means characterized by an optic axis; and

a front group including means defining a front surface;

means for rigidly coupling said magnification means and said front group while preventing relative movement therebetween;

said front group and said magnification means being characterized by respective first and second sets of optical parameters chosen to define a front focus of said objective which is located proximate said front surface such that said objective operates as a substantially fully corrected microscope objective for magnification of an object located at a position proximate said front surface, and said objective operates as a wide angle lens having substantially fully corrected field aberrations for imaging of an object located a substantial distance in front of said front surface, each of said sets of optical parameters including geometrical parameters, namely surface radii and surface locations along said optical axis, and optical material parameters, namely refractive index and dispersion values, said first and second sets of optical parameters defining first, second, and third powers of said magnification means, said front group, and the objective as a whole;

the operation of said objective as a substantially fully corrected microscope objective being largely determined by said first set of optical parameters with said front group contributing little to the aberrations and overall power of said objective, the ratio of said first power to said third power being between 0.8 and 1.4;

said second set of optical parameters being chosen to correct field aberrations of said objective when said objective operates as a wide angle lens.

38. An endoscope having distal and proximal ends, comprising:

optical transfer means for transferring at fixed magnification an image formed at an image plane to said proximal end, said image plane being fixed relative to said optical transfer means;

magnification means characterized by an optic axis;

a front group including means defining a front surface;

means for rigidly coupling said magnification means and said front group to one another while preventing relative movement therebetween to define an objective; and

slidable support means for permitting said objective to move with respect to said image plane over a range along said optical axis, said range including a first position of maximum magnification wherein an object located at a position proximate said front surface is imaged in said image plane, and a second position of relatively lower magnification wherein an object at a substantial distance from said front surface is imaged in said image plane;

said magnification means and said front group being characterized by respective first and second sets of optical parameters chosen such that said objective operates as a substantially fully corrected microscope objective for said first position and as a wide angle lens that has substantially fully corrected field aberrations for said second position, each of said sets of optical parameters including geometrical parameters, namely surface radii and surface locations along said optical axis, and optical material parameters, namely refractive index and dispersion values, said first and second sets of optical parameters defining first, second, and third powers of said magnification means, said front group, and the objective as a whole;

the operation of said objective as a substantially fully corrected microscope objective being largely determined by said first set of optical parameters with said front group contributing little to the aberrations and overall power of said objective, the ratio of said first power to said third power being between 0.8 and 1.4;

said second set of optical parameters being chosen to correct field aberrations of said objective when said objective operates as a wide angle lens.

44. In an endoscope having distal and proximal ends, optical transfer means for transferring at fixed magnification an image formed at an image plane fixed relative to said optical transfer means to said proximal end, and an objective movable relative to said image plane along an optic axis, said objective being movable over a range including first and second widely spaced positions to permit normal microscopy at large magnification and normal endoscopy at relatively small magnification, the improvement wherein said objective comprises:

a positive lens group in a microscope objective configuration; and

a front group including a front element and an aperture stop located between said front element and said positive lens group;

means for rigidly coupling said positive lens group and said front group while preventing relative movement therebetween;

said aperture stop being located so as to be largely ineffective when said objective is in said first position of large magnification and so as to maintain the marginal chief ray approximately parallel to the optic axis for an object at a substantial distance ahead of said front surface;

said positive lens group and said front group being characterized by respective first and second sets of optical parameters chosen such that said objective operates as a substantially fully corrected microscope objective for said first position and as a wide angle lens that has substantially fully corrected field aberrations for said second position, each of said sets of optical parameters including geometrical parameters, namely surface radii and surface locations along said optical axis, and optical material parameters, namely refractive index and dispersion values, said first and second sets of optical parameters defining first, second, and third powers of said positive lens group, said front group, and the objective as a whole;

the operation of said objective as a substantially fully corrected microscope objective being largely determined by said first set of optical parameters with said front group contributing little to the aberrations and overall power of said objective, the ratio of said first power to said third power being between 0.8 and 1.4;

said second set of optical parameters being chosen to correct field aberrations of said objective when said objective operates as a wide angle lens.

50. An endoscope objective having substantially fully corrected field aberrations for microscopic and wide angle viewing comprising a negative front lens element, an aperture stop, and a positive lens group made of optical materials and having normalized geometrical parameters as follows:

space="preserve" listing-type="tabular">__________________________________________________________________________ Refractive Dispersion Radius Thickness Medium Index Factor __________________________________________________________________________r.sub.1 = infinite LaF 21 n.sub.12 = 1.792266 df.sub.12 = 0.064 t.sub.12 = 0.250000 r.sub.2 = 1.798864 air t.sub.23 = 0.300000 d.sub.3 = stop diameter = 0.600000 air t.sub.34 = 0.759514 r.sub.4 = -13.198478 LaSF 31 n.sub.45 = 1.885793 df.sub.45 = 0.156 t.sub.45 = 1.000000 r.sub.5 = -1.798864 air t.sub.56 = 0.100000 r.sub.6 = 8.851848 SF 57 n.sub.67 = 1.855035 df.sub.67 = 1.033 t.sub.67 = 0.600000 r.sub.7 = 1.798864 PSK 3 n.sub.78 = 1.554398 df.sub.78 = 0.069 t.sub.78 = 1.000000 r.sub.8 = -3.077912 Effective focal length = 2.0665 Back focal length = 85.5176 Magnification = -39.969367 Numerical aperture = 0.5 __________________________________________________________________________

where the single subscripts denote the characteristic surfaces of the elements and the double subscripts denote the regions between two such surfaces.

51. An endoscope objective having substantially fully corrected field aberrations for microscopic and wide angle viewing comprising a negative front lens element, an aperture stop, and a positive lens group made of optical materials and having normalized geometrical parameters as follows:

space="preserve" listing-type="tabular">__________________________________________________________________________ Refractive Dispersion Radius Thickness Medium Index Factor __________________________________________________________________________r.sub.1 = infinite LaF 21 n.sub.12 = 1.792266 df.sub.12 = 0.064 t.sub.12 = 0.250000 r.sub.2 = 2.106310 air t.sub.23 = 0.300000 d.sub.3 = stop diameter = 0.600000 air t.sub.34 = 0.757206 r.sub.4 = -12.991887 LaSF 31 n.sub.45 = 1.885793 df.sub.45 = 0.156 t.sub.45 = 1.000000 r.sub.5 = -1.799147 air t.sub.56 = 0.100000 r.sub.6 = 8.753429 SF 57 n.sub.67 = 1.855035 df.sub.67 = 1.033 t.sub.67 = 0.600000 r.sub.7 = 1.801988 PSK 3 n.sub.78 = 1.554398 df.sub.78 = 0.069 t.sub.78 = 1.000000 r.sub.8 = -3.080649 Effective focal length = 2.0537 Back focal length = 84.0989 Magnification = -39.660418 Numerical aperture = 0.5 __________________________________________________________________________

where the single subscripts denote the characteristic surfaces of the elements and the double subscripts denote the regions between two such surfaces.

52. An endoscope objective having substantially fully corrected field aberrations for microscopic and wide angle viewing comprising a negative front lens element, an aperture stop, and a postive lens group made of optical materials and having normalized geometrical parameters as follows:

space="preserve" listing-type="tabular">__________________________________________________________________________ Refractive Dispersion Radius Thickness Medium Index Factor __________________________________________________________________________r.sub.1 = infinite LaF 21 n.sub.12 = 1.792266 df.sub.12 = 0.064 t.sub.12 = 0.400000 r.sub.2 = 1.644080 air t.sub.23 = 0.250000 d.sub.3 = stop diameter = 0.600000 air t.sub.34 = 0.264474 r.sub.4 = 36.942089 SF 6 n.sub.45 = 1.812647 df.sub.45 = 0.991 t.sub.45 = 0.600000 r.sub.5 = 2.937294 LaF N2 n.sub.56 = 1.747949 df.sub.56 = 0.181 t.sub.56 = 1.000000 r.sub.6 = -1.636253 air t.sub.67 = 0.561421 r.sub.7 = 7.888618 SF 6 n.sub.78 = 1.812647 df.sub.78 = 0.991 t.sub.78 = 0.400000 r.sub.8 = 1.983490 BaF 3 n.sub.89 = 1.585648 df.sub.89 = 0.580 t.sub. 89 = 0.900000 r.sub.9 = -3.665581 Effective focal length = 2.0973 Back focal length = 87.8771 Magnification = -40.634309 Numerical aperture = 0.5 __________________________________________________________________________

where the single subscripts denote the characteristic surfaces of the elements and the double subscripts denote the regions between corresponding surfaces.

53. An endoscope objective having substantially fully corrected field aberrations for microscopic and wide angle viewing comprising a negative front lens element, an aperture stop, and a positive lens group made of optical materials and having normalized geometrical parameters as follows:

space="preserve" listing-type="tabular">__________________________________________________________________________ Refractive Dispersion Radius Thickness Medium Index Factor __________________________________________________________________________r.sub.1 = infinite LaF 21 n.sub.12 = 1.792266 df.sub.12 = 0.064 t.sub.12 = 0.400000 r.sub.2 = 2.930140 air t.sub.23 = 0.250000 d.sub.3 = stop diameter = 0.600000 air t.sub.34 = 0.346655 r.sub.4 = 51.294217 SF 6 n.sub.45 = 1.812647 df.sub.45 = 0.991 t.sub.45 = 0.400000 r.sub.5 = 2.348542 LaF N2 n.sub.56 = 1.747949 df.sub.56 = 0.181 t.sub.56 = 1.000000 r.sub.6 = -1.637301 air t.sub.67 = 0.802218 r.sub.7 = 7.775985 SF 6 n.sub.78 = 1.812647 df.sub.78 = 0.991 t.sub.78 = 0.400000 r.sub.8 = 2.013554 BaF 3 n.sub.89 = 1.585648 df.sub.89 = 0.580 t.sub. 89 = 0.900000 r.sub.9 = -3.673853 Effective focal length = 2.1023 Back focal length = 86.0183 Magnification = -40.11219 Numerical aperture = 0.5 __________________________________________________________________________

where the single subscripts denote the characteristic surfaces of the elements and the double subscripts denote the regions between two such surfaces.

48. The invention of claim 53 wherein said front group includes means defining a peripheral surface having portions with normal axis at an acute angle with respect to said optic axis to permit illumination of said object located at said position proximate said front surface.