Zoom lens having weak front lens group

• US 5,315,440 A
• Filed: 11/04/1991
• Issued: 05/24/1994
• Est. Priority Date: 11/04/1991
• Status: Expired due to Fees

• Current Assignee: Eastman Kodak Company
• Original Assignee: Eastman Kodak Company
• Inventors: Kreitzer, Melvyn H., Betensky, Ellis I.
• Primary Examiner(s): Arnold, Bruce Y.
• Assistant Examiner(s): NGUYEN, THONG Q
• Application Number:
  US07/792,504
• Time in Patent Office: 932 Days
• Field of Search: 359/676, 359/677, 359/708, 359/717, 359/718, 359/728, 359/793-795, 359/684, 359/685, 359/689-693, 359/716, 359/738-740
• US Class Current: 359/692
• CPC Class Codes: G02B 15/16 with interdependent non-linearly related movements between one lens or lens group, and another lens or lens group G02B15/22 takes precedence

Abstract

A zoom lens having two groups of lens components including from the object side a positive group and a negative group. The positive group includes two lens units, a weak unit, and a positive unit, while the negative group has at least one negative lens component and provides most of the magnification change during zooming.

Claims

1. A zoom lens comprising two groups of lens components including, from the object side, a first positive group and a second negative group and which zoom lens achieves zooming between a wide angle position and a narrow angle position by changing a distance between the first and the second groups,

said first group including two lens units, a first, weak unit having no strong lens component, said weak first unit positioned on the object side of said first group and a second positive unit following said first unit,

said second group having negative power and providing most of the magnification change during zooming,

wherein none of said lens components are made of a gradient index material,

said zoom lens satisfying the following condition ##EQU2## where K₁ is the power of the first unit and K_w is the power of the zoom lens at its wide angle position, and

wherein said weak unit is a single negative lens component.

2. A zoom lens according to claim 1 wherein the first unit has at least one aspheric surface.

3. A zoom lens according to claim 2 wherein an aperture stop is positioned toward the object side from the second unit.

4. A zoom lens according to claim 1 wherein the ratio of |K₁ |/K_w is equal to 0.1 or less.

5. A zoom lens according to claim 4 wherein an aperture stop is positioned toward the object side from the second unit.

6. A zoom lens according to claim 1 wherein an aperture stop is positioned toward the object side from the second unit.

7. A zoom lens according to claim 1 wherein the second group consists of a doublet.

8. A zoom lens according to claim 1 wherein said second unit includes at least one negative lens element providing substantially all of the color correction of the first group.

9. A zoom lens according to claim 1 wherein the space between said first unit and said second unit varies during zooming.

10. A zoom lens according to claim 1 wherein the space between said first unit and said second unit does not vary during zooming.

11. A zoom lens according to claim 1 wherein said first optical unit is a single element having at least one aspheric surface.

12. A zoom lens according to claim 11 wherein the ratio |K₁ |/K_w is equal to 0.1 or less.

13. A zoom lens constructed substantially according to the following parameters

14. A zoom lens constructed substantially according to the following parameters

15. A zoom lens constructed substantially according to the following parameters

16. A zoom lens constructed substantially according to the following parameters

17. A zoom lens constructed substantially according to the following parameters

18. A zoom lens constructed substantially according to the following parameters

19. A zoom lens constructed substantially according to the following parameters

20. A zoom lens constructed substantially according to the following parameters

21. A zoom lens comprising two groups of lens components including, from the object side, a first positive group and a second negative group and which zoom lens achieves zooming between a wide angle position and a narrow angle position by changing the distance between the first and the second groups,

said first group including two lens units and an aperture stop, a first, weak unit having no strong lens component, said first unit being of negative power and having at least one aspheric surface, said first unit positioned on the object side of said first group and a second positive unit following said first unit, said aperture stop is positioned toward the object from said second unit,

said second group having negative power and providing most of the magnification change during zooming, and

said zoom lens satisfying the following condition ##EQU3## where K₁ is the power of the first unit and K_w is the power of the zoom lens at its wide angle position.