Image pickup optical system and image pickup apparatus

Abstract

An image pickup optical system according to the present invention includes: a first lens group having a positive power; a second lens group having a negative power; a third lens group having a positive power; and a fourth lens group having a positive power which consists of a front group with a negative power and a rear group with a positive power. The first lens group moves to the object side and a distance between each neighboring lens groups changes, for varying power of the image pickup optical system. One group of the front group and the rear group in the fourth lens group consists of one lens which moves substantially perpendicular to an optical axis for a shake compensation. The image pickup optical system fulfills the predetermined conditional formula according to a focal length of the first lens group.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements numbered alike in several Figures, in which:

FIG. 1( a) illustrates a perspective view of an exterior of each embodiment of a digital camera and FIG. 1(b) illustrates a rear side view of an embodiment of the digital camera;

FIG. 2 illustrates a block diagram of each embodiment of the digital camera configuration;

FIG. 3 illustrates the structure of an image pickup optical system in the first embodiment;

FIG. 4 illustrates the structure of an image pickup optical system in the second embodiment;

FIG. 5 illustrates the structure of an image pickup optical system in the third embodiment;

FIG. 6 illustrates the structure of an image pickup optical system in the fourth embodiment;

FIGS. 7( a)-7(c) illustrate diagrams showing aberrations of the image pickup optical system of the first embodiment at wide-angle end, middle focal length, and telephoto end, respectively:

FIGS. 8( a)-8(c) illustrate diagrams showing aberrations of the image pickup optical system of the second embodiment at wide-angle end, middle focal length, and telephoto end, respectively;

FIGS. 9( a)-9(c) illustrate diagrams showing aberrations of the image pickup optical system of the third embodiment at wide-angle end, middle focal length, and telephoto end, respectively;

FIGS. 10( a)-10(c) illustrate diagrams showing aberrations of the image pickup optical system of the fourth embodiment at wide-angle end, middle focal length, and telephoto end, respectively;

FIGS. 11( a) and 11(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system for conducting the shake compensation by using the front group of the fourth lens group of the first embodiment at wide-angle end, respectively;

FIGS. 12( a) and 12(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system for conducting the shake compensation by using the front group of the fourth lens group of the first embodiment at telephoto end, respectively;

FIGS. 13( a) and 13(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system for conducting the shake compensation by using the rear group of the fourth lens group of the first embodiment at wide-angle end, respectively;

FIGS. 14( a) and 14(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system for conducting the shake compensation by using the rear group of the fourth lens group of the first embodiment at telephoto end, respectively;

FIGS. 15( a) and 15(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system of the second embodiment at wide-angle end, respectively;

FIGS. 16( a) and 16(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system of the second embodiment at telephoto end, respectively;

FIGS. 17( a) and 17(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system of the third embodiment at wide-angle end, respectively;

FIGS. 18( a) and 18(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system of the third embodiment at telephoto end, respectively;

FIGS. 19( a) and 19(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system of the fourth embodiment at wide-angle end, respectively; and

FIGS. 20( a) and 20(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system of the fourth embodiment at telephoto end, respectively.

Claims

1. An image pickup optical system for forming a light flux from an object into an optical image on an image pickup element, the image pickup optical system comprising, in order from an object side thereof: a first lens group having a positive power;a second lens group having a negative power;a third lens group having a positive power; anda fourth lens group having a positive power which consists of, in order from the object side, a front group with a negative power and a rear group with a positive power,wherein the first lens group moves to the object side and a distance between each neighboring lens groups changes, for varying power of the image pickup optical system from a wide-angle end to a telephoto end,one group between the front group and the rear group in the fourth lens group consists of one lens which moves substantially perpendicular to an optical axis for a shake compensation, andthe image pickup optical system fulfills a following conditional formula: 5<fl/fw<20,where fl is a focal length of the first lens group, andfw is a focal length of the image pickup optical system at a wide-angle end.

2. The image pickup optical system of claim 1, wherein the fourth lens group fulfills a following conditional formula: −3<f4n/f4p<−1,where f4n is a focal length of the front group, andf4p is a focal length of the rear group.

3. The image pickup optical system of claim 1, wherein the image pickup optical system fulfills a following conditional formula: 0.01<f3/f4<1,where f3 is a focal length of the third lens group, andf4 is a focal length of the fourth lens group.

4. The image pickup optical system of claim 1, wherein the other group which is not used for the shake compensation in the fourth lens group consists of one lens.

5. The image pickup optical system of claim 1, wherein the third lens group comprises a plurality of lenses including a lens closest to the image which has an aspheric surface.

6. The image pickup optical system of claim 1, wherein the first lens group consists of a negative lens and a positive lens, in order from the object side.

7. The image pickup optical system of claim 1, wherein the image pickup optical system fulfills following conditional formulas: −3<f4n/f4p<−1, and0.01<f3/f4<1,where f4n is a focal length of the front group in the fourth lens group,f4p is a focal length of the rear group in the fourth lens group,f3 is a focal length of the third lens group, andf4 is a focal length of the fourth lens group.

8. The image pickup optical system of claim 1, wherein the fourth lens group fulfills a following conditional formula: −3<f4n/f4p<−1,where f4n is a focal length of the front group, andf4p is a focal length of the rear group, andwherein the other group which is not used for the shake compensation in the fourth lens group consists of one lens.

9. The image pickup optical system of claim 1, further comprising: a fifth lens group arranged at an image pickup element side of the fourth lens group.

10. The image pickup optical system of claim 1, the image pickup optical system fulfills a following conditional formula: 6<fl/fw<15.

11. The image pickup optical system of claim 1, wherein the fourth lens group fulfills a following conditional formula: −2.5<f4n/f4p<−1.1,where f4n is a focal length of the front group, andf4p is a focal length of the rear group.

12. The image pickup optical system of claim 1, wherein the image pickup optical system fulfills a following conditional formula: 0.1<f3/f4<0.6,where f3 is a focal length of the third lens group, andf4 is a focal length of the fourth lens group.

13. An image pickup apparatus comprising: the image pickup optical system of claim 1; andan image pickup element for receiving a light flux guided by the image pickup optical system.

14. The image pickup apparatus of claim 13, wherein the fourth lens group in the image pickup optical system fulfills a following conditional formula: −3<f4n/f4p<−1,where f4n is a focal length of the front group, andf4p is a focal length of the rear group.

15. The image pickup apparatus of claim 13, wherein the image pickup optical system fulfills a following conditional formula: 0.01<f3/f4<1,where f3 is a focal length of the third lens group, andf4 is a focal length of the fourth lens group.

16. The image pickup apparatus of claim 13, wherein the other group which is not used for the shake compensation in the fourth lens group in the image pickup optical system consists of one lens.

17. The image pickup apparatus of claim 13, wherein the image pickup optical system further comprises a fifth lens group arranged at an image pickup element side of the fourth lens group.

18. The image pickup apparatus of claim 13, wherein the image pickup optical system fulfills a following conditional formula: 6<fl/fw<15.

19. The image pickup apparatus of claim 13, wherein the fourth lens group in the image pickup optical system fulfills a following conditional formula: −2.5<f4n/f4p<−1.1,where f4n is a focal length of the front group, andf4p is a focal length of the rear group.

20. The image pickup apparatus of claim 13, wherein the image pickup optical system fulfills a following conditional formula: 0.1<f3/f4<0.6,where f3 is a focal length of the third lens group, andf4 is a focal length of the fourth lens group.