Lens assembly and optical imaging system using same

• US 7,054,076 B2
• Filed: 03/11/2004
• Issued: 05/30/2006
• Est. Priority Date: 03/11/2004
• Status: Expired due to Fees

• Current Assignee: Pinotage LLC
• Original Assignee: Pinotage LLC
• Inventors: Thompson, Robert Lee, Tesar, John
• Primary Examiner(s): Harrington, Alicia M
• Application Number:
  US10/798,841
• Publication Number:
  US 20050200977A1
• Time in Patent Office: 810 Days
• Field of Search: 359/760, 359/759, 359/757, 359/752, 359/740, 359/754, 359/756, 359/776
• US Class Current: 359/726
• CPC Class Codes: G02B 13/004 having four lenses
• CPC Class Codes: G02B 13/006 at least one element being a compound optical element, e.g. cemented elements
• CPC Class Codes: G02B 13/22 Telecentric objectives or lens systems
• CPC Class Codes: G02B 27/0025 for optical correction, e.g. distorsion, aberration
• CPC Class Codes: G02B 9/34 having four components only
• CPC Class Codes: G02B 9/62 having six components only

Abstract

A lens assembly is constructed to accommodate certain, often competing, design characteristics. The lens assembly provides high optical performance in a compact and easy to manufacture system. The lens assembly allows a manufacturer to produce a system that is common among various aperture sizes so that manufacturability is enhanced. The lens assembly is also suitable for use in connection with additional components, such as filters and/or electronic detectors, such as CCD'"'"'s and/or CMOS'"'"'s. The lens assembly may be arranged to provide a relatively wide angle, such as approximately 40 degrees, with minimal distortion, for example, less than 1%. a ratio of the length of the lens assembly to the back focal length of approximately 1.39 to accommodate additional components, such as optical filters. The lens assembly may be configured as a four group, six element, lens assembly. The lens assembly may contain compensating aberrations to compensate the aberrations of plane parallel plates that may be used in connection with the lens assembly.

Claims

1. A lens assembly for imaging an object, the lens assembly comprising:

a plurality of lenses adapted to provide;

1) a field of view of approximately 40 degrees; and

2) a distortion of less than approximately 1%,

wherein the plurality of lenses is further adapted to provide a ratio of the length of the lens assembly to the back focal length of approximately 1.39.

2. The lens assembly of claim 1, further comprising:

at least one filter plate;

wherein the plurality of lenses is further adapted to produce at least one aberration to compensate an aberration produced by the at least one filter plate.

3. The lens assembly of claim 1, wherein the lens assembly further comprises:

an aperture stop; and

wherein the plurality of lenses is configured symmetrically about the aperture stop.

4. The lens assembly of claim 1, in combination with an imaging device.

5. The lens assembly of claim 4, wherein the imaging device is a security camera.

6. The lens assembly of claim 1, wherein the plurality of lenses comprises:

a first lens group having at least one first lens element, the at least one first lens element having a first surface proximal to the object and a second surface distal to the object; and

a second lens group having at least one second lens element, the at least one second lens element having a first surface proximal to the object and second surface distal to the object.

7. The lens assembly of claim 6, further comprising:

an aperture stop disposed between the first lens group and the second lens group.

8. The lens assembly of claim 7, wherein the aperture stop has a fixed size selectable from a range of aperture stop sizes.

9. The lens assembly of claim 7, wherein the aperture stop is physically contacted by at least one lens of the plurality of lenses.

10. The lens assembly of claim 6, wherein the first and second lens groups are arranged to define a focal length, and wherein a distance between the first surface of the at least one first lens element and the second surface of the at least one second lens element is less than approximately 95% of the focal length.

11. The lens assembly of claim 6, wherein the image of the object is produced on an image plane, the lens assembly further comprising:

at least one filter disposed between the at least one second lens element and the image plane.

12. The lens assembly of claim 11, wherein the at least one filter is a planar filter.

13. The lens assembly of claim 11, wherein the plurality of lenses is further adapted to produce at least one aberration to compensate an aberration produced by the filter.

14. The lens assembly of claim 6, further comprising:

a third lens group having at least one first lens element, the at least one first lens element having a first surface proximal to the object and second surface distal to the object; and

a fourth lens group having at least one second lens element, the at least one second lens element having a first surface proximal to the object and a second surface distal to the object.

15. The lens assembly of claim 14, wherein the first, second, third, and fourth lens groups define a double-Gauss-type lens assembly.

16. The lens assembly of claim 14, further comprising:

an aperture stop, wherein the aperture stop is disposed between the third lens group and the fourth lens group.

17. The lens assembly of claim 16, wherein the third lens group is disposed on a same side relative to the aperture stop as is the first lens group.

18. The lens assembly of claim 17, wherein the third lens group includes a third lens element and a fourth lens element.

19. The lens assembly of claim 18, wherein the third lens element is a positive lens element, and the fourth lens element is a negative lens element.

20. The lens assembly of claim 17, wherein the fourth lens group includes a fifth lens element and a sixth lens element.

21. The lens assembly of claim 20, wherein the fifth lens element is a positive lens element and the sixth lens element is a negative lens element.

22. The lens assembly of claim 21, wherein each of the step locations has a thickness chosen to ensure proper spacing of the plurality of lenses.

23. The lens assembly of claim 1, wherein the lens assembly is housed within a housing having step locations to receive the plurality of lenses.

24. The lens assembly of claim 23, wherein the housing further has an outer surface including flats for affixing a tool thereto.

25. A lens assembly for imaging an object, the lens assembly comprising:

a plurality of lenses adapted to provide;

1) a field of view of approximately 40 degrees; and

2) a distortion of less than approximately 1%

wherein the plurality of lenses is arranged to define a total length, the total length is between approximately 0.95 and approximately 1.02 of the focal length.

26. A lens assembly for imaging an object, the lens assembly comprising:

a plurality of lenses adapted to provide;

1) a field of view of approximately 40 degrees; and

2) a distortion of less than approximately 1%

wherein the plurality of lenses comprises;

a first lens group having at least one first lens element, the at least one first lens element having a first surface proximal to the object and a second surface distal to the object; and

a second lens group having at least one second lens element, the at least one second lens element having a first surface proximal to the object and second surface distal to the object

wherein the first and second lens groups are arranged to define a focal length, and wherein a distance between the first surface of the at least one first lens element and the second surface of the at least one second lens element is less than approximately 95% of the focal length, wherein the total length is between approximately 0.95 and approximately 1.02 of the focal length.

27. A lens assembly for imaging an object, the lens assembly comprising:

a first lens group having at least one first lens element, the at least one first lens element having a first surface proximal to the object and second surface distal to the object;

a second lens group having at least one second lens element, the at least one second lens element having a first surface proximal to the object and second surface distal to the object; and

an aperture stop disposed between the first lens group and the second lens group;

wherein the first and second lens groups are arranged to define a focal length, and wherein a distance between the first surface of the at least one first lens element and the second surface of the at least one second lens element is less than approximately 95% of the focal length, wherein the total length of the lens assembly is between approximately 0.95 and approximately 1.02 of the focal length.

28. The lens assembly of claim 27, further comprising:

a housing having an aperture stop location at a position fixed relative to the housing; and

wherein the aperture stop disposed between the first lens group and the second lens group has an aperture stop size selectable from a plurality of aperture stop sizes, and wherein the aperture stop is disposed at the fixed position of the aperture stop location, independent of the aperture stop size.

29. The lens assembly of claim 27, further comprising:

a third lens group having at least one first lens element, the at least one first lens element having a first surface proximal to the object and second surface distal to the object; and

a fourth lens group having at least one second lens element, the at least one second lens element having a first surface proximal to the object and second surface distal to the object.

30. The lens assembly of claim 29, wherein the aperture stop is disposed between the third lens group and the fourth lens group.

31. The lens assembly of claim 30, wherein the third lens group is disposed on a same side relative to the aperture stop as is the first lens group.

32. The lens assembly of claim 31, wherein the third lens group includes a third lens element and a fourth lens element.

33. The lens assembly of claim 32, wherein the third lens element is a positive lens element, and the fourth lens element is a negative lens element.

34. The lens assembly of claim 31, wherein the fourth lens group includes a fifth lens element and a sixth lens element.

35. The lens assembly of claim 34, wherein the fifth lens element is a positive lens element and the sixth lens element is a negative lens element.

36. The lens assembly of claim 29, wherein the first, second, third, and fourth lens groups define a double-Gauss-type lens.

37. The lens assembly of claim 27, further comprising at least one filter plate disposed between the second lens group and an image plane.

38. The lens assembly of claim 27, further comprising at least one electronic detector disposed at an image plane.

39. The lens assembly of claim 27, in combination with an imaging device.

40. The lens assembly of claim 39, wherein the imaging device is a security camera.

41. A lens assembly for imaging an object, the lens assembly comprising:

a first lens group having at least one first lens element, the at least one first lens element having a first surface proximal to the object and second surface distal to the object;

a second lens group having at least one second lens element, the at least one second lens element having a first surface proximal to the object and second surface distal to the object; and

an aperture stop disposed between the first lens group and the second lens group;

wherein the first and second lens groups are arranged to define a focal length, and wherein a distance between the first surface of the at least one first lens element and the second surface of the at least one second lens element is less than approximately 95% of the focal length, wherein the lens assembly further comprises;

a housing having an aperture stop location at a position fixed relative to the housing; and

wherein the aperture stop disposed between the first lens group and the second lens group has an aperture stop size selectable from a plurality of aperture stop sizes, and wherein the aperture stop is disposed at the fixed position of the aperture stop location, independent of the aperture stop size.

42. A lens system comprising a plurality of lens elements and an aperture stop, each lens element having a lens surface defined by a radius of curvature (r), a thickness (T), and an index of refraction (n), the plurality of lens elements being spaced from each other by a distance (h), the lens system satisfying at least one of the following conditions:

1000<

r₄/r₂ or r₄=r₂=approximately infinity;

−

0.56<

r₃/r₉<

−

0.81;

0.9<

r₈/r₉<

1.1 or r₈=r₉;

0.9<

r₁₀/r₁₁<

1.1 or r₁₀=r₁₁;

0.7<

(h₁+h₂)/(h₃+h₄)<

1.1;

0.95<

h₁+h₂+h₃+h₄++T₁+T₂+T₃+T₄+T₅+T₆<

f/1.02;

1.71<

n_L1,n_L2,n_L5,n_L6<

1.79; and

1.67<

n_L3,n_L4<

1.81;

where;

r₂ represents a radius of curvature of an image side surface of a first lens element;

r₃ represents a radius of curvature of an object side surface of a second lens element;

r₄ represents a radius of curvature of an image side surface of the second lens element;

r₈ represents a radius of curvature of an object side surface of a fifth lens element;

r₉ represents a radius of curvature of an image side surface of the fifth lens element;

r₁₀ represents a radius of curvature of an object side surface of a sixth lens element;

r₁₁ represents a radius of curvature of an image side surface of the sixth lens element;

h₁ represents a gap distance between the image side surface of the first lens element to the object side surface of the second lens element;

h₂ represents a gap distance between the image side surface of a third lens element to the aperture stop;

h₃ represents a gap distance between the aperture stop to an object side surface of a fourth lens element;

h₄ represents a gap distance between the image side surface of the fifth lens element to the object side surface of the sixth lens element;

T₁ represents a thickness of the first lens element;

T₂ represents a thickness of the second lens element;

T₃ represents a thickness of the third lens element;

T₄ represents a thickness of the fourth lens element;

T₅ represents a thickness of the fifth lens element;

T₆ represents a thickness of the sixth lens element;

n_L1 represents an index of refraction of the first lens element;

n_L2 represents an index of refraction of the second lens element;

n_L3 represents an index of refraction of the third lens element;

n_L4 represents an index of refraction of the fourth lens element;

n_L5 represents an index of refraction of the fifth lens element; and

n_L6 represents an index of refraction of the sixth lens element,

wherein the lens system further comprises a focal length of approximately 10 mm.

43. The lens system according to claim 42, the lens system satisfying a plurality of the conditions.

44. A lens system comprising a plurality of lens elements and an aperture stop, each lens element having a lens surface defined by a radius of curvature (r), a thickness (T), and an index of refraction (n), the plurality of lens elements being spaced from each other by a distance (h), the lens system satisfying at least one of the following conditions:

1000<

r₄/r₂ or r₄=r₂=approximately infinity;

−

0.56<

r₃/r₉<

−

0.81;

0.9<

r₈/r₉<

1.1 or r₈=r₉;

0.9<

r₁₀/r₁₁<

1.1 or r₁₀=r₁₁;

0.7<

(h₁+h₂)/(h₃+h₄)<

1.1;

0.95<

h₁+h₂+h₃+h₄++T₁+T₂+T₃+T₄+T₅+T₆<

f/1.02;

1.71<

n_L1,n_L2,n_L5, n_L6<

1.79; and

1.67<

n_L3,n_L4<

1.81;

where;

r₂ represents a radius of curvature of an image side surface of a first lens element;

r₃ represents a radius of curvature of an object side surface of a second lens element;

r₄ represents a radius of curvature of an image side surface of the second lens element;

r₈ represents a radius of curvature of an object side surface of a fifth lens element;

r₉ represents a radius of curvature of an image side surface of the fifth lens element;

r₁₀ represents a radius of curvature of an object side surface of a sixth lens element;

r₁₁ represents a radius of curvature of an image side surface of the sixth lens element;

h₁ represents a gap distance between the image side surface of the first lens element to the object side surface of the second lens element;

h₂ represents a gap distance between the image side surface of a third lens element to the aperture stop;

h₃ represents a gap distance between the aperture stop to an object side surface of a fourth lens element;

h₄ represents a gap distance between the image side surface of the fifth lens element to the object side surface of the sixth lens element;

T₁ represents a thickness of the first lens element;

T₂ represents a thickness of the second lens element;

T₃ represents a thickness of the third lens element;

T₄ represents a thickness of the fourth lens element;

T₅ represents a thickness of the fifth lens element;

T₆ represents a thickness of the sixth lens element;

n_L1 represents an index of refraction of the first lens element;

n_L2 represents an index of refraction of the second lens element;

n_L3 represents an index of refraction of the third lens element;

n_L4 represents an index of refraction of the fourth lens element;

n_L5 represents an index of refraction of the fifth lens element; and

n_L6 represents an index of refraction of the sixth lens element, in combination with an aperture stop having a size selected from a plurality of aperture stop sizes.

45. The combination according to claim 44, wherein the plurality of aperture stop sizes comprises f11, f8, f5.6, f4, f2.8.

46. A lens system comprising a plurality of lens elements and an aperture stop, each lens element having a lens surface defined by a radius of curvature (r), a thickness (T), and an index of refraction (n), the plurality of lens elements being spaced from each other by a distance (h), the lens system satisfying each of the following conditions:

1000<

r₄/r₂ or r₄=r₂=approximately infinity;

−

0.56<

r₈/r₉<

−

0.81;

0.9<

r₈/r₉<

1.1 orr₈=r₉;

0.9<

r₁₀/r₁₁<

1.1 or r₁₀=r₁₁;

0.7<

(h1+h₂)/(h₃+h₄)<

1.1;

0.95<

h₁+h₂+h₃+h₄++T₁+T₂+T₃+T₄+T₅+T₆<

f/1.02;

1.71<

n_L1,n_L2,n_L5, n_L6<

1.79; and

1.67<

n_L3,n_L4<

1.81;

where;

r₂ represents a radius of curvature of an image side surface of a first lens element;

r₃ represents a radius of curvature of an object side surface of a second lens element;

r₄ represents a radius of curvature of an image side surface of the second lens element;

r₈ represents a radius of curvature of an object side surface of a fifth lens element;

r₉ represents a radius of curvature of an image side surface of the fifth lens element;

r₁₀ represents a radius of curvature of an object side surface of a sixth lens element;

r₁₁ represents a radius of curvature of an image side surface of the sixth lens element;

h₁ represents a gap distance between the image side surface of the first lens element to the object side surface of the second lens element;

h₂ represents a gap distance between the image side surface of a third lens element to the aperture stop;

h₃ represents a gap distance between the aperture stop to an object side surface of a fourth lens element;

h₄ represents a gap distance between the image side surface of the fifth lens element to the object side surface of the sixth lens element;

T₁ represents a thickness of the first lens element;

T₂ represents a thickness of the second lens element;

T₃ represents a thickness of the third lens element;

T₄ represents a thickness of the fourth lens element;

T₅ represents a thickness of the fifth lens element;

T₆ represents a thickness of the sixth lens element;

n_L1 represents an index of refraction of the first lens element;

n_L2 represents an index of refraction of the second lens element;

n_L3 represents an index of refraction of the third lens element;

n_L4 represents an index of refraction of the fourth lens element;

n_L5 represents an index of refraction of the fifth lens element; and

n_L6 represents an index of refraction of the sixth lens element.