Imaging lens, optical apparatus and method for forming image using this imaging lens

• US 7,940,478 B2
• Filed: 04/09/2009
• Issued: 05/10/2011
• Est. Priority Date: 04/11/2008
• Status: Active Grant

• Current Assignee: Nikon Corporation
• Original Assignee: Nikon Corporation
• Inventors: Take, Toshinori
• Primary Examiner(s): Spector; David N
• Application Number:
  US12/421,323
• Publication Number:
  US 20090257125A1
• Time in Patent Office: 761 Days
• Field of Search: 359/794, 359/793, 359/753
• US Class Current: 359/794
• 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 27/646 compensating for small deviations, e.g. due to vibration or shake movement of one or more optical elements for control of motion blur in cameras, projectors or printers G03B2205/0007; image stabilisation in cameras peculiar to the presence or use of an electronic image sensor H04N23/68

Abstract

An imaging lens includes a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power, which are disposed in order from an object. The first lens group has a first lens component having a negative refractive power and a second lens component having a positive refractive power, which are disposed in order from the object, and conditions expressed by the expressions 0.12<f/f1<0.47 and 0.016<D12/f<0.079 are satisfied, when f1 is a focal length of the first lens group, f is a focal length of the imaging lens, and D12 is an air distance between the first lens component and the second lens component of the first lens group.

Claims

1. An imaging lens, comprising a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power, which are disposed in order from an object,

the first lens group including a first lens component having a negative refractive power and a second lens component having a positive refractive power, which are disposed in order from the object, and

conditions expressed by the following expressions being satisfied:

0.12<

f/f1<

0.47

0.016<

D12/f<

0.079

where f1 is a focal length of the first lens group, f is a focal length of an imaging lens, and D12 is an air distance between the first lens component and the second lens component of the first lens group.

2. The imaging lens according to claim 1, wherein the first lens group comprises the first lens component made of a negative meniscus lens having a convex surface facing the object, and the second lens component made of a positive meniscus lens having a convex surface facing the object, which are disposed in order from the object.

3. The imaging lens according to claim 1, wherein a condition expressed by the following expression is satisfied:

nd1>

1.65

where nd1 is a refractive index of the first lens component of the first lens group on the d-line.

4. The imaging lens according to claim 1, wherein a condition expressed by the following expression is satisfied:

3.8<

(r2F+r1R)/(r2F−

r1R)<

11.8

where r1R is a radius of curvature of an image side lens surface of the first lens component, and r2F is a radius of curvature of an object side lens surface of the second lens component.

5. The imaging lens according to claim 1, wherein the second lens group comprises a biconvex positive lens, and the biconvex positive lens includes at least one aspherical surface.

6. An optical apparatus, comprising an imaging lens that forms an image of an object on a predetermined image surface, wherein the imaging lens is the imaging lens according to claim 1.

7. The imaging lens according to claim 1, wherein a condition expressed by the following expression is satisfied:

3.0<

TL/Ymax<

4.0

where TL is a total length of the imaging lens, and Ymax is a maximum image height.

8. The imaging lens according to claim 1, wherein a condition expressed by of the following expression is satisfied:

1.7<

TL/Σ

d<

2.2

where TL is a total length of the imaging lens, and Σ

d is a length on the optical axis, from a lens surface closest to the object in the first lens group to a lens surface closest to the image in the second lens group.

9. The imaging lens according to claim 1, wherein the second lens group comprises a cemented lens of a negative lens component having a concave surface facing the object and a positive lens component having a convex surface facing the image, and a biconvex positive lens component, which are disposed in order from the object.

10. The imaging lens according to claim 1, wherein a condition expressed by the following expression is satisfied:

0.13<

f2/f1<

0.47

where f1 is a focal length of the object side lens group, and f2 is a focal length of the image side lens group.

11. The imaging lens according to claim 1, wherein the focus on a close object is adjusted by moving the image side lens group toward the object.

12. The imaging lens according to claim 1, wherein the first lens component of the first lens group includes at least one aspherical surface.

13. The imaging lens according to claim 1, wherein the second lens group includes at least one aspherical surface.

14. The imaging lens according to claim 1, wherein all or a part of the image side lens group is able to be shifted in a direction substantially perpendicular to the optical axis as a shift lens group.

15. The imaging lens according to claim 14, wherein a condition expressed by the following expression is satisfied:

0.80<

f/fS<

1.10

where f is a focal length of the imaging lens, and fS is a focal length of the shift lens group.

16. The imaging lens according to claim 1, wherein

the second lens group includes a cemented lens of a negative lens component and a first positive lens component, and a second positive lens component, which are disposed in order from the object, and

conditions expressed by the following expressions are satisfied:

nd5<

1.67

vd5>

50.0

where nd5 is a refractive index of the second positive lens component of the second lens group on the d-line, and vd5 is an Abbe number of the second positive lens component of the second lens group on the d-line.

17. The imaging lens according to claim 16, wherein a condition expressed by the following expression is satisfied:

−

0.30<

(r5R+r5F)/(r5R−

r5F)<

0.40

where r5F is a radius of curvature of an object side lens surface of the second positive lens component of the second lens group, and r5 R is a radius of curvature of an image side lens surface of the second positive lens component of the second lens group.

18. The imaging lens according to claim 16, wherein a condition expressed by the following expression is satisfied:

0.60<

f/f5<

0.90

where f is a focal length of the imaging lens, and f5 is a focal length of the second positive lens component of the second lens group.

19. A method for manufacturing an imaging lens, comprising the steps of:

assembling a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power in a lens barrel in order from an object;

configuring the first lens group by disposing a first lens component having a negative refractive power and a second lens component having a positive refractive power in order from the object when the step of assembling is performed,

conditions expressed by the following expressions being satisfied;

0.12<

f/f1<

0.47

0.016<

D12/f<

0.079

where f1 is a focal length of the first lens group, f is a focal length of an imaging lens, and D12 is an air distance between the first lens component and the second lens component of the first lens group.

20. The method for manufacturing the imaging lens according to claim 19, wherein the first lens group comprises the first lens component made of a negative meniscus lens having a convex surface facing the object, and the second lens component made of a positive meniscus lens having a convex surface facing the object, which are disposed in order from the object.

21. The method for manufacturing the imaging lens according to claim 19, wherein a condition expressed by the following expression is satisfied:

nd1>

1.65

where nd1 is a refractive index of the first lens component of the first lens group on the d-line.

22. The method for manufacturing the imaging lens according to claim 19, wherein a condition expressed by the following expression is satisfied:

3.8<

(r2F+r1R)/(r2F−

r1R)<

11.8

where r1R is a radius of curvature of an image side lens surface of the first lens component, and r2F is a radius of curvature of an object side lens surface of the second lens component.

23. The method for manufacturing the imaging lens according to claim 19, wherein the second lens group comprises a biconvex positive lens, wherein the biconvex positive lens includes at least one aspherical surface.

24. The method for manufacturing an imaging lens according to claim 19, wherein a condition expressed by the following expression is satisfied:

3.0<

TL/Ymax<

4.0

where TL is a total length of the imaging lens, and Ymax is a maximum image height.

25. The method for manufacturing the imaging lens according to claim 19, wherein a condition expressed by the following expression is satisfied:

1.7<

TL/Σ

d<

2.2

where TL is a total length of the imaging lens, and Σ

d is a length on the optical axis, from a lens surface closest to the object in the first lens group to a lens surface closest to the image in the second lens group.

26. The method for manufacturing the imaging lens according to claim 19, wherein the second lens group comprises a cemented lens of a negative lens component having a concave surface facing the object and a positive lens component having a convex surface facing the image, and a biconvex positive lens component, which are disposed in order from the object.

27. The method for manufacturing the imaging lens according to claim 19, wherein a condition expressed by the following expression is satisfied:

0.13<

f2/f1<

0.47

where f1 is a focal length of the object side lens group, and f2 is a focal length of the image side lens group.

28. The method for manufacturing the imaging lens according to claim 19, wherein the focus on a close object is adjusted by moving the image side lens group toward the object.

29. The method for manufacturing the imaging lens according to claim 19, wherein the first lens component of the first lens group includes at least one aspherical surface.

30. The manufacturing method for the imaging lens according to claim 19, wherein the second lens group includes at least one aspherical surface.

31. The method for manufacturing an imaging lens according to claim 19, wherein all or a part of the image side lens group is assembled as a shift lens group to be shifted in a direction substantially perpendicular to the optical axis.

32. The method for manufacturing the imaging lens according to claim 19, wherein a condition expressed by the following expression is satisfied:

0.80<

f/fS<

1.10

where f is a focal length of the imaging lens, and fS is a focal length of the shift lens group.

33. The method for manufacturing an imaging lens according to claim 19, wherein

the second lens group is configured by disposing a cemented lens of a negative lens component and a first positive lens component, and a second positive lens component in order from the object when the step of assembling is performed, and

conditions expressed by the following expressions are satisfied:

nd5<

1.67

vd5>

50.0

where nd5 is a refractive index of the second positive lens component of the second lens group on the d-line, and vd5 is an Abbe number of the second positive lens of the second lens group on to the d-line.

34. The method for manufacturing the imaging lens according to claim 33, wherein a condition expressed by the following expression is satisfied:

−

0.30<

(r5R+r5F)/(r5R−

r5F)<

0.40

where r5F is a radius of curvature of an object side lens surface of the second positive lens component of the second lens group, and r5R is a radius of curvature of an image side lens surface of the second positive lens component of the second lens group.

35. The method for manufacturing the imaging lens according to claim 33, wherein a condition expressed by the following expression is satisfied:

0.60<

f/f5<

0.90

where f is a focal length of the imaging lens, and f5 is a focal length of the second positive lens component of the second lens group.