ZOOM OPTICAL SYSTEM AND IMAGE TAKING APPARATUS USING THE SAME

• US 20060245078A1
• Filed: 04/27/2006
• Published: 11/02/2006
• Est. Priority Date: 04/28/2005
• Status: Active Grant

• Current Assignee: Olympus Corporation
• Original Assignee: Olympus Imaging Corporation (Olympus Corporation)
• Inventors: Kawamura, Kazuteru
• Granted Patent: US 7,212,351 B2
• Time in Patent Office: Days
• US Class Current: 359/689
• CPC Class Codes: G02B 15/143503 arranged -+-
• CPC Class Codes: G02B 15/144511 arranged -+-+

Abstract

An image taking optical system which comprises, in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power, wherein the second lens unit moves toward the object side so that a space between the first lens unit and the second lens unit decreases, and the third lens unit moves so that a space between the second lens unit and the third lens unit changes, in a case where zooming is performed from a wide-angle end to a telephoto end, the first lens unit includes at least one lens, among which there exists only one lens that has a negative refractive power, and the second lens unit includes at least one positive lens and at least one negative lens.

Claims

1. An image taking optical system comprising, in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a positive refractive power, and a third lens unit having a negative refractive power,

wherein the second lens unit moves toward the object side so that a space between the first lens unit and the second lens unit decreases, and the third lens unit moves so that a space between the second lens unit and the third lens unit changes, in a case where zooming is performed from a wide-angle end to a telephoto end,

the first lens unit includes at least one lens, among which there exists only one lens that has a negative refractive power, and the second lens unit includes at least one positive lens and at least one negative lens,

the image taking optical system satisfying the following conditions:

4.0≦

W_—

L/(tan ω

×

FL)≦

12.0;


1.7≦

|Δ

D12|/(tan ω

×

FL)≦

4.6; and


52.0≦

PAVd,

wherein W_L denotes the whole length of the image taking optical system in the wide-angle end, ω

denotes a maximum ray incidence angle onto the image taking optical system at a time when the image taking optical system is in an arbitrary state, FL denotes a focal length of the image taking optical system in the arbitrary state, Δ

D12 denotes a change amount of the space between the first lens unit and the second lens unit during the zooming from the wide-angle end to the telephoto end, and PAVd denotes the Abbe number of the positive lens of the second lens unit.

2. The system according to claim 1, further satisfying the following condition:

0.45≦

D23W/(tan ω

×

FL)≦

3.0,

wherein D23W denotes a length from a lens surface closest to the image side in the second lens unit to a lens surface closest to the object side in the third lens unit in the wide-angle end.

3. The system according to claim 1, further satisfying the following condition:

0.38≦

(f2/fw)×

(tan ω

×

FL/fw)≦

0.95,

wherein f2 denotes a focal length of the second lens unit, and fw denotes a focal length of the image taking optical system in the wide-angle end.

4. The system according to claim 1, further satisfying the following condition:

2.7≦

W_—

L/fw≦

10.0,

wherein fw denotes a focal length of the image taking optical system in the wide-angle end.

5. The system according to claim 1, further satisfying the following condition:

3.7≦

|Δ

D12/Δ

D23|,

wherein Δ

D23 denotes a change amount of a space between the second lens unit and the third lens unit during the zooming from the wide-angle end to the telephoto end.

6. The system according to claim 1, wherein the first lens unit includes two lenses of a negative lens and a positive lens in order from the object side, and satisfies the following condition:

0.6≦

G1Σ

d/(tan ω

×

FL)≦

1.3,

wherein G1Σ

d denotes a length from a lens surface closest to the object side to a lens surface closest to the image side in the first lens unit.

7. The system according to claim 1, wherein the second lens unit includes one negative lens and at least one positive lens, and at least one of the positive lenses satisfies the following condition:

75.0≦

PVd,

wherein PVd denotes the Abbe number of the positive lens of the second lens unit.

8. The system according to claim 7, further satisfying the following condition:

45.0≦

PVd−

NVd,

wherein NVd denotes the Abbe number of the negative lens of the second lens unit.

9. The system according to claim 1, wherein the third lens unit includes two lenses at most.

10. The system according to claim 1, wherein the first lens unit includes two lenses of a negative lens and a positive lens in order from the object side, the second lens unit includes three lenses of a positive lens, a negative lens, and a positive lens, or two lenses of a positive lens and a negative lens in order from the object side, and the third lens unit includes a negative lens.

11. The system according to claim 1, wherein the first lens unit moves during the zooming so that the whole length of the optical system is minimized between the wide-angle end and the telephoto end.

12. The system according to claim 1, further satisfying the following condition in the wide-angle end:

7.0%≦

|DTW_—

×

1.0|,

wherein DTW_—

×

1.0 denotes a value indicated in % of distortion in a position corresponding to a maximum image height in the wide-angle end at a time when the system is focused on an infinite object, and the value is represented by the following in a case where it is assumed that Y′

0 is a paraxial image height and Y′

is an actual image height;

distortion=[(Y′

−

Y′

0)/Y′

0]×

100(%).

13. The system according to claim 12, further satisfying the following condition in the wide-angle end:

3.5%≦

|DTW_—

×

0.7|≦

15.0%;


7.0%≦

|DTW_—

1.0|≦

25.0%; and


|Δ

DTW|≦

15.0%,

wherein DTW_—

×

0.7 denotes a value indicated in % of the distortion in a position corresponding to a height 0.7 time the maximum image height in the wide-angle end at a time when the system is focused on an infinite object, and Δ

DTW denotes a difference between the values indicated in % of the distortion in positions corresponding to heights 0.7 time and 1.0 time the maximum image height in the wide-angle end at a time when the optical system is focused on the infinite object.

14. The system according to claim 1, wherein the third lens unit is moved in an optical-axis direction to thereby perform focusing.

15. The system according to claim 1, further satisfying the following condition:

0.53≦

tan ω

×

FL/fw,

wherein fw is a focal length of the image taking optical system in the wide-angle end.

16. The system according to claim 1, which comprises only the first lens unit, the second lens unit, and the third lens unit as lens units.

17. The system according to claim 1, wherein a fourth lens unit having a positive power and fixed during the zooming is disposed on the image side of the third lens unit.

18. The system according to claim 17, wherein the fourth lens unit includes one positive lens.

19. An image taking apparatus comprising:

the image taking optical system according to claim 1;

and an image sensor disposed on the image side of the image taking optical system.

20. The system according to claim 19, wherein a low pass filter is disposed between the image taking optical system and the image sensor.

21. An image taking apparatus comprising:

a zoom lens system including a movable lens unit on whose image side a positive lens and an image sensor unit are arranged in order from an object side,

wherein the positive lens and the image sensor unit are brought into a sealed structure via a member constituting the image taking apparatus, and a lens unit having a negative refractive power is disposed on the object side of the positive lens with an air space between the lens unit and the positive lens.

22. The apparatus according to claim 21, wherein the positive lens has a low pass filter function or an infrared cutting function.

23. The apparatus according to claim 21, wherein the lens unit having the negative refractive power satisfies the following condition:

0.6≦

DL/IH≦

1.5,

wherein DL denotes a length between an object-side surface of the positive lens and an image forming surface of the zoom lens system, and IH denotes a maximum image height.

24. The apparatus according to claim 21, wherein the lens unit having the negative power is included in the movable lens unit.

25. The apparatus according to claim 21, wherein the positive lens satisfies the following condition:

−

3.7≦

(R1+R2)/(R1−

R2)≦

−

0.3,

wherein R1 denotes a radius of curvature of the object-side surface of the positive lens, and R2 denotes a radius of curvature of the image-side surface of the positive lens.

26. The apparatus according to claim 21, wherein the movable lens unit includes, in order from the object side, a first lens unit having a negative power, a second lens unit having a positive power, and a third lens unit having a negative power, and

the positive lens is disposed on the image side of the third lens unit with an air space between the positive lens and the third lens unit.

27. The apparatus according to claim 21, wherein the positive lens is made of plastic,

the apparatus further comprising:

a field stop,

the field stop, the positive lens, and the image sensor unit being integrally attached to the member constituting the apparatus.

28. The apparatus according to claim 21, wherein the positive lens is made of plastic, and

the apparatus further comprising:

a field stop,

a planar contact portion capable of being brought into contact with the field stop is formed in a lens peripheral portion of the positive lens made of plastic.

29. The apparatus according to claim 21, wherein the positive lens is made of plastic, and

at least a part of the positive lens comes into contact with at least a part of the image sensor unit.

30. The apparatus according to claim 21, wherein the positive lens is made of plastic,

a contact surface is formed outside a region of an effective diameter of the positive lens made of plastic, and the positive lens comes into contact with the image sensor unit via the contact surface.

31. The apparatus according to claim 21, wherein the image-side surface of the positive lens is coated with a wavelength band restricting coating.

32. The apparatus according to claim 21, wherein the positive lens is a plano-convex positive lens which directs its convex surface on the object side.