Retrofocus wide-angle lens

• US 6,747,815 B2
• Filed: 01/23/2003
• Issued: 06/08/2004
• Est. Priority Date: 01/29/2002
• Status: Active Grant

• Current Assignee: Fuji Photo Optical Co. Ltd (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Optical Co. Ltd (Fujifilm Holdings Corporation)
• Inventors: Takatsuki, Akiko
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): HASAN, MOHAMMED A
• Application Number:
  US10/348,754
• Publication Number:
  US 20030156335A1
• Time in Patent Office: 502 Days
• Field of Search: 359/749-753, 359/762, 359/770, 359/793, 359/820
• US Class Current: 359/749
• CPC Class Codes: G02B 13/04 Reversed telephoto objectives

Abstract

A retrofocus wide-angle lens includes a first lens group of negative refractive power, a diaphragm, and a second lens group of positive refractive power. The first lens group includes an object-side lens group, a middle lens group, and an image-side lens group. The object-side lens group includes a plurality of negative lens components and a positive meniscus lens component with its convex surface on the image side. The middle lens group satisfies a particular focal length condition and includes a negative lens component at the object side. The image-side lens group includes a negative lens element and a positive lens element. The first and second lens groups include lens elements of opposite refractive power that are made of anomalous dispersion glass so as to provide chromatic aberration correction and to compensate for variations in refractive index with temperature change that would otherwise cause the focal length to vary with temperature.

Claims

1. A retrofocus wide-angle lens formed of only two lens groups, in order from the object side, as follows:

a first lens group of negative refractive power;

a diaphragm; and

a second lens group of positive refractive power;

wherein

said first lens group includes, in order from the object side, an object-side lens group, a first light-receiving lens group, and a second light-receiving lens group;

said object-side lens group includes, in order from the object side, a plurality of negative lens components and a positive meniscus lens component with its convex surface on the image side;

said first light-receiving lens group includes an initial negative lens group that includes a negative lens component that is at the object side of said first light-receiving lens group; and

said second light-receiving lens group includes a negative lens element and a positive lens element.

2. The retrofocus wide-angle lens of claim 1, wherein said initial negative lens group moves toward the object side when the retrofocus wide-angle lens is focused from infinity toward a near point, and wherein the following condition is satisfied:

3. The retrofocus wide-angle lens of claim 1, wherein said- second lens group includes a positive lens element made of anomalous dispersion glass, and said first lens group includes a negative lens element made of a material that has a refractive index N that satisfies the following condition:

4. The retrofocus wide-angle lens of claim 1, wherein said second lens group includes, in order from the object side, an infinity-related lens group and a movable lens group constructed and arranged so that the composite focal length of the first lens group and the infinity-related lens group is nearly infinite, and the movable lens group may be slightly varied in position along the optical axis X in order to adjust the back focus of the retrofocus wide-angle lens so as to coincide precisely with the image plane.

5. The retrofocus wide-angle lens of claim 2, wherein said second lens group includes, in order from the object side, an infinity-related lens group and a movable lens group constructed and arranged so that the composite focal length of the first lens group and the infinity-related lens group is nearly infinite, and the movable lens group may be slightly varied in position along the optical axis X in order to adjust the back focus of the retrofocus wide-angle lens so as to coincide precisely with the image plane.

6. The retrofocus wide-angle lens of claim 3, wherein said second lens group includes, in order from the object side, an infinity-related lens group and a movable lens group constructed and arranged so that the composite focal length of the first lens group and the infinity-related lens group is nearly infinite, and the movable lens group may be slightly varied in position along the optical axis X in order to adjust the back focus of the retrofocus wide-angle lens so as to coincide precisely with the image plane.

7. The retrofocus wide-angle lens of claim 1, wherein the retrofocus wide-angle lens is mounted in a lens barrel.

8. The retrofocus wide-angle lens of claim 2, wherein the retrofocus wide-angle lens is mounted in a lens barrel.

9. The retrofocus wide-angle lens of claim 3, wherein the retrofocus wide-angle lens is mounted in a lens barrel.

10. The retrofocus wide-angle lens of claim 4, wherein the retrofocus wide-angle lens is mounted in a lens barrel.

11. The retrofocus wide-angle lens of claim 5, wherein the retrofocus wide-angle lens is mounted in a lens barrel.

12. The retrofocus wide-angle lens of claim 6, wherein the retrofocus wide-angle lens is mounted in a lens barrel.

13. The retrofocus wide-angle lens of claim 1, wherein said initial negative lens group consists of a negative lens component.

14. The retrofocus wide-angle lens of claim 2, wherein said initial negative lens group consists of a negative lens component.

15. The retrofocus wide-angle lens of claim 3, wherein said initial negative lens group consists of a negative lens component.

16. The retrofocus wide-angle lens of claim 4, wherein said initial negative lens group consists of a negative lens component.

17. The retrofocus wide-angle lens of claim 1, wherein said initial negative lens group consists of a negative lens element.

18. The retrofocus wide-angle lens of claim 2, wherein said initial negative lens group consists of a negative lens element.

19. The retrofocus wide-angle lens of claim 3, wherein said initial negative lens group consists of a negative lens element.

20. The retrofocus wide-angle lens of claim 4, wherein said initial negative lens group consists of a negative lens element.