Zoom lens

• US 5,179,472 A
• Filed: 06/25/1991
• Issued: 01/12/1993
• Est. Priority Date: 06/25/1990
• Status: Expired due to Term

• Current Assignee: Fuji Photo Optical Co. Ltd (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Optical Co. Ltd (Fujifilm Holdings Corporation)
• Inventors: Miyano, Hitoshi, Ohno, Kazunori
• Primary Examiner(s): Sugarman, Scott J.
• Application Number:
  US07/719,301
• Time in Patent Office: 567 Days
• Field of Search: 359/676, 359/683, 359/687, 359/708, 359/685
• US Class Current: 359/687
• CPC Class Codes: G02B 15/144113 arranged +-++

Abstract

A zoom lens comprises first to fourth lens groups in order from the subject end. Second to third lens groups move along optical axis of the zoom lens for zooming between a wide-angle end where the zoom lens has the shortest focal length and a telephoto end where the zoom lens has the longest focal length. During the zooming, first lens group remains stationary. As the second lens group moves towards the image end for zooming from the wide-angle end to the telephoto end, the third and fourth lens groups are moved so as to initially decrease a relative axial distance therebetween and subsequently increase the axial distance, thereby correcting changes in focus caused by the axial movement of the second lens group during zooming.

Claims

1. A zoom lens comprising in order from the object end a positive power of first lens means which remains stationary during zooming, a negative power of second lens means movable along an optical axis of the zoom lens between a wide-angle end where the zoom lens has a shortest focal length and a telephoto end where the zoom lens has a longest focal length for zooming, a positive power of third lens means and a positive power of fourth lens means both of which are movable along the optical axis during zooming, so that as said second negative lens means moves from said wide-angle end to said telephoto end for zooming, the third and fourth lens means are moved so as to initially decrease a relative axial distance between the third and fourth positive lens means and subsequently increase the axial distance while the second negative lens means moves, thereby correcting a change in focus caused by the second negative lens means during zooming.

2. A zoom lens as recited in claim 1, and further comprising a low-pass filter disposed stationary after said fourth positive lens means.

3. A zoom lens as recited in claim 1, wherein said third lens initially moves toward the image end and subsequently moves towards the object end.

4. A zoom lens as recited in claim 3, wherein said third lens means occupies the same axial position at said telephoto end as at said wide-angle end when said zoom lens is focused at infinity.

5. A zoom lens as recited in claim 4, wherein said fourth lens means moves in an axial direction opposite to an axial direction in which said third lens means moves.

6. A zoom lens as recited in claim 1, wherein said first lens means comprises in order from the object end a negative meniscus lens element convex to the object end, a positive bi-convex lens element and a positive meniscus lens element convex to the object end.

7. A zoom lens as recited in claim 6, wherein said negative meniscus lens element and said positive bi-convex lens element are cemented.

8. A zoom lens as recited in claim 6, wherein said second lens means comprises in order from the object end a negative meniscus lens element convex to the subject end, a negative bi-concave lens element and a positive lens element having a surface convex to the object end.

9. A zoom lens as recited in claim 8, wherein said negative bi concave lens element and said positive lens element are cemented.

10. A zoom lens as recited in claim 8, wherein said third lens means comprises a positive single lens element.

11. A zoom lens as recited in claim 10, wherein said positive single lens element has a surface convex to the object end.

12. A zoom lens as recited in claim 10, wherein said positive single lens element has an aspherical lens surface.

13. A zoom lens as recited in claim 10, wherein said fourth lens means comprises in order from the subject end a positive bi-convex lens element, a negative lens element having a surface concave to the image end and a positive bi-convex lens element.

14. A zoom lens as recited in claim 13, wherein said fourth lens means has at least one aspherical lens surface.

15. A zoom lens as recited in claim 14, wherein at least one of said positive bi-convex lens elements has an aspherical lens surface.

16. A zoom lens as recited in claim 2, further satisfying:

##EQU5## where f2 is the power of said second lens means; and

fw is the focal length of the zoom lens at said wide-angle end; and

ft is the focal length of the zoom lens at said telephoto end.

17. A zoom lens as recited in claim 16, further satisfying:

##EQU6## where f3 is the power of said third lens means;

fw is the focal length of the zoom lens at said wide-angle end; and

ZR is the zoom ratio of the zoom lens.

18. A zoom lens as recited in claim 13, further defined substantially as follows:

space="preserve" listing-type="tabular">______________________________________ Lens Surface Axial Distance Lens Surface Radius (mm) Between Surfaces (mm) Ne ______________________________________ r1 44.263 L1 1.10 1.81264 r2 20.273 L2 5.47 1.59143 r3 -70.547 0.20 r4 15.444 L3 3.36 1.59143 r5 44.457 M/0.50-T/12.50 r6 71.425 L4 0.72 1.83929 r7 6.965 2.48 r8 -8.291 L5 0.72 1.77620 r9 6.279 L6 2.18 1.81264 r10 -59.579 W/13.50-T/1.50 r11 (Asperical) L7 2.50 1.59143 r12 -83.488 W/7.50-T/7.50 r13 (Asperical) L8 3.0 1.59143 r14 -22.741 0.50 r15 59.214 L9 0.72 1.81264 r16 8.386 0.48 r17 10.911 L10 2.90 1.59143 r18 -43.016 W/7.80-T/7.80 r19 Infinite L11 6.40 1.51825 r20 Infinite ______________________________________

where

L1-L11 are the lens elements in order from the subject end, r1-r20 are lens surfaces in order from the object end with positive radii struck from the right and negative radii struck from the left, and Ne identifies the index of refraction measured by an e-line spectrum.

19. A zoom lens as recited in claim 18, wherein said aspherical surface is defined as follows:

space="preserve" listing-type="tabular">______________________________________ X = ##STR1## ASPHERICAL COEFFICIENT Lens Surface;

r11 Lens Surface;

r13 ______________________________________ C 6.817097 ×

10.sup.-2 9.048955 ×

10.sup.-2 K 9.387801 ×

10.sup.-1 -1.02458 A1 0.0 0.0 A2 -6.941958 ×

10.sup.-5 -6.088017 ×

10.sup.-6 A3 -1.590088 ×

10.sup.-6 -1.647785 ×

10.sup.-8 A4 7.273377 ×

10.sup.-9 3.198951 ×

10.sup.-12 ______________________________________

where

X is the axial distance;

Y is the height from the axis;

A1-A4 are aspherical coefficients;

C is the reciprocal of a radius of paraxial surface; and

K is an eccentricity.

20. A zoom lens as recited in claim 13, further defined substantially as follows:

space="preserve" listing-type="tabular">______________________________________ Lens Surface Axial Distance Lens Surface Radius (mm) Between Surfaces (mm) Ne ______________________________________ r1 41.616 L1 1.10 1.81264 r2 19.942 L2 5.52 1.59143 r3 -73.124 0.20 r4 15.998 L3 3.26 1.59143 r5 47.910 W/0.50-T/12.50 r6 71.416 L4 0.72 1.83929 r7 7.072 2.38 r8 -8.842 L5 0.72 1.77620 r9 5.910 L6 2.22 1.81264 r10 -134.696 W/13.50-T/1.50 r11 (Asperical) L7 2.50 1.59143 r12 Infinite W/7.50-T/7.50 r13 9.862 L8 3.0 1.67341 r14 -20.847 0.50 r15 -19.857 L9 0.72 1.81264 r16 10.744 0.48 r17 (Asperical) L10 2.90 1.59143 r18 -17.061 W/7.80-T/7.80 r19 Infinite L11 6.40 1.51825 r20 Infinite ______________________________________

where

L1-L11 are the lens elements in order from the subject end, r1-r20 are lens surfaces in order from the object end with positive radii struck from the right and negative radii struck from the left, and Ne identifies the index of refraction measured by an e-line spectrum.

21. A zoom lens as recited in claim 20, wherein said aspherical surface is defined as follows:

space="preserve" listing-type="tabular">______________________________________ X = ##STR2## ASPHERICAL COEFFICIENT 11th Lens Surface 17th Lens Surface ______________________________________ C 7.904201 ×

10.sup.-2 8.061396 ×

10.sup.-2 K 1.065024 7.464477 ×

10.sup.-1 A1 0.0 0.0 A2 -8.679398 ×

10.sup.-5 -3.876448 ×

10.sup.-4 A3 -1.563098 ×

10.sup.-7 -1.517197 ×

10.sup.-7 A4 7.274023 ×

10.sup.-9 -2.053923 ×

10.sup.-8 ______________________________________

where

X is the axial distance;

Y is the height from the axis;

A1-A4 are aspherical coefficients;

C is the reciprocal of a radius of paraxial surface; and

K is an eccentricity.

22. A zoom lens comprising in order from the subject end a positive power of first lens means movable along an optical axis of the zoom lens for focusing but remaining stationary during zooming, a negative power of second lens means, a positive power of third lens means, a positive power of fourth lens means, a low-pass filter disposed stationary after said fourth lens means and aperture means disposed closely to said third lens means between said second and fourth leans means, said second to fourth lens means being moved relatively to one another along said optical axis for zooming between a wide-angle end where the zoom lens has a shortest focal length and a telephoto end where the zoom lens has a longest focal length so as to decreasingly change an axial distance between said second and third lens means during a zooming from said wide angle end to said telephoto end, and said aperture means being moved along said optical axis in the same axial direction and distance as the third positive lens means during zooming.

23. A zoom lens as recited in claim 22, wherein said aperture means is disposed after said third lens means.

24. A zoom lens as recited in claim 23, wherein said aperture means is disposed before said third lens means.

25. A zoom lens as recited in claim 23, wherein said first lens means comprises, in order from the subject end, a negative meniscus lens element convex to the subject end, a positive bi-convex lens element and a positive meniscus lens element convex to the subject end.

26. A zoom lens as recited in claim 25, wherein said negative meniscus lens element and said positive bi-convex lens element are cemented.

27. A zoom lens as recited in claim 25, wherein said second negative lens means comprises, in order from the subject end, a negative meniscus lens element convex to the object end, a negative bi-concave lens element and a positive lens element having a surface convex to the object end.

28. A zoom lens as recited in claim 27, wherein said negative bi-concave lens element and said positive lens element are cemented.

29. A zoom lens as recited in claim 27, wherein said third positive lens means consists of a positive single lens element.

30. A zoom lens as recited in claim 29, wherein said positive single lens element has a surface convex to the object end.

31. A zoom lens as recited in claim 29, wherein said positive single lens element has an aspherical lens surface.

32. A zoom lens as recited in claim 29, wherein said fourth positive lens means comprises, in order from the subject end, a positive meniscus lens element, a negative lens element having a surface concave to the image end and a positive bi-convex lens element.

33. A zoom lens as recited in claim 32, wherein said fourth positive lens means has at least one aspherical lens surface.

34. A zoom lens as recited in claim 32, wherein said positive meniscus lens element has an aspherical lens surface.

35. A zoom lens as recited in claim 34, further satisfying:

space="preserve" listing-type="equation">2.5<

f3/ fw<

4.5

where

f3 is the power of said third lens means; and

fw is the shortest focal length of the zoom lens.

36. A zoom lens as recited in claim 35, further defined substantially as follows:

space="preserve" listing-type="tabular">______________________________________ Lens Surface Sur- Radius Axial Distance Lens face (mm) Between Surfaces (mm) Nd Vd ______________________________________ r1 29.053 L1 1.20 1.84666 23.9 r2 19.787 L2 5.00 1.48749 70.4 r3 -108.170 0.07 r4 18.355 L3 3.60 1.48749 70.4 r5 51.330 W/0.48-M/9.19-T/16.59 r6 54.638 L4 0.72 1.71300 53.9 r7 7.779 1.90 r8 -12.623 L5 0.72 1.75896 50.4 r9 5.489 L6 1.80 1.80518 25.5 r10 23.536 W/10.96-M/5.93-T/1.20 r11 Aspherical L7 2.04 1.51823 59.0 r12 -66.166 W/11.69-M/5.58-T/6.25 r13 Aspherical L8 3.60 1.48749 70.4 r14 43.943 0.06 r15 10.366 L9 0.66 1.84666 23.9 r16 5.269 0.94 r17 10.629 L10 2.40 1.77250 49.6 r18 -155.680 W/1.00-M/1.00-T/1.00 r19 Infinite L11 6.40 1.51633 64.1 r20 Infinite ______________________________________

where

L1-L11 are lens elements in order from the subject end, r1- r20 are lens surfaces in order from the object end with positive radii struck from the right and negative radii struck from the left, and Nd and Vd, respectively, identify the index of refraction measured by a d-line spectrum and Abbe Number.

37. A zoom lens as recited in claim 36, wherein said aspherical surface is defined as follows:

space="preserve" listing-type="tabular">______________________________________ X = ##STR3## ASPHERICAL COEFFICIENT Lens Surface;

r11 Lens Surface;

r13 ______________________________________ C 0.064346 0.166794 K 0.994157 0.339525 A1 0.0 0.0 A2 -9.8228 ×

10.sup.-5 1.08899 ×

10.sup.-4 A3 -5.3973 ×

10.sup.-7 4.53960 ×

10.sup.-6 A4 -7.1375 ×

10.sup.-10 -1.08032 ×

10.sup.-8 ______________________________________

where

X is the axial distance;

Y is the height from the axis;

A1-A4 are aspherical coefficients;

C is the reciprocal of a radius of paraxial surface; and

K is an eccentricity.

38. A zoom lens as recited in claim 35, further defined substantially as follows:

space="preserve" listing-type="tabular">______________________________________ Lens Surface Axial Distance Sur- Radius Between Lens face (mm) Surfaces (mm) Nd Vd ______________________________________ r1 28.015 L1 1.20 1.84666 23.9 r2 19.500 L2 5.00 1.48749 70.4 r3 -142.610 0.07 r4 19.504 L3 3.40 1.51633 64.1 r5 51.902 W/0.60-T/17.50 r6 39.908 L4 0.72 1.83400 37.2 r7 7.818 1.99 r8 -11.201 L5 0.72 1.77250 49.6 r9 6.739 L6 2.40 1.84666 23.9 r10 44.427 W/12.12-T/1.20 r11 (Aspherical) L7 2.50 1.43425 95.0 r12 -37.291 W/10.26-T/5.03 r13 8.229 L8 2.30 1.77250 49.6 r14 21.915 0.54 r15 294.360 L9 0.66 1.80518 25.5 r16 8.901 0.18 r17 (Aspherical) L10 3.00 1.49230 57.6 r18 -10.981 W/1.00-T/1.00 r19 Infinite L11 6.40 1.51633 64.1 r20 Infinite ______________________________________

where

L1-L11 are lens elements in order from the subject end, r1-r20 are lens surfaces in order from the object end with positive radii struck from the right and negative radii struck from the left, and Nd and Vd, respectively, identify the index of refraction measured by a d-line spectrum and Abbe Number.

39. A zoom lens as recited in claim 38, wherein said aspherical surface is defined as follows:

space="preserve" listing-type="tabular">______________________________________ X = ##STR4## ASPHERICAL COEFFICIENT Lens Surface;

r11 Lens Surface;

r17 ______________________________________ C 0.0972304 0.0987066 K 1.270048 -0.301388 A1 0.0 0.0 A2 -1.90721 ×

10.sup.-4 -5.47835 ×

10.sup.-4 A3 -1.78797 ×

10.sup.-6 -6.60585 ×

10.sup.-7 A4 6.64139 ×

10.sup.-9 -1.97355 ×

10.sup.-8 ______________________________________

where

X is the axial distance;

Y is the height from the axis;

A1-A4 are aspherical coefficients;

C is the reciprocal of a radius of paraxial surface; and

K is an eccentricity.

40. A zoom lens comprising in order from the subject end a positive power of first lens means, a negative power of second lens means, a positive power of third lens means, a positive power of fourth lens means, and aperture means disposed closely to said third lens means between said second and fourth lens means, said fourth lens means being moved along the optical axis of said zoom lens for focusing, said second to fourth lens means being moved relatively to one another, while the first lens means remains stationary, during zooming in such a way that third to fourth lens means being moved relatively to one another along said optical axis for zooming between a wide-angle end where the zoom lens has a shortest focal length and a telephoto end where the zoom lens has a longest focal length so as to decreasingly change an axial distance between said second and third lens means during a zooming from said wide-angle end to said telephoto end, and said aperture means being moved along said optical axis in the same axial direction and distance as the third positive lens means during zooming.