Image pickup optical system and image pickup apparatus

Abstract

An image pickup optical system according to the present invention is provided for forming a light flux from an object into an optical image on an image pickup element. The image pickup optical system 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; a fourth lens group having a negative power; and a fifth lens group. A distance between each neighboring lens groups changes with the fourth lens group statically positioned, for varying power of the image pickup optical system. The fourth lens group moves in a direction substantially perpendicular to an optical axis for shake compensation. The image pickup optical system fulfills the predetermined conditional formulas according to focal lengths of the first and fourth lens groups.

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 an 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;

FIGS. 6( a)-6(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. 7( a)-7(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. 8( a)-8(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. 9( a) and 9(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system of the first embodiment at wide-angle end, respectively;

FIGS. 10( a) and 10(b) illustrate diagrams showing meridional transverse aberration of before and after conducting the decentering of the image pickup optical system of the first embodiment at 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 of the second 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 of the second 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 of the third embodiment at wide-angle end, respectively; and

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 of the third 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;a fourth lens group having a negative power; anda fifth lens group,wherein a distance between each neighboring lens groups among the first to fifth lens groups changes with the fourth lens group positioned at a fixed distance to an image surface of the image pickup optical system, for varying power of the image pickup optical system from a wide-angle end to a telephoto end,the fourth lens group moves in a direction substantially perpendicular to an optical axis for a shake compensation, andthe image pickup optical system fulfills following conditional formulas: 6<f1/fw<20, and−0.7<f4/ft<−0.2,where f1 is a focal length of the first lens group,fw is a focal length of the image pickup optical system at the wide-angle end,f4 is a focal length of the fourth lens group, andft is a focal length of the image pickup optical system at the telephoto end.

2. The image pickup optical system of claim 1, wherein the fourth lens group consists of one lens including at least one aspherical surface, and the fourth lens group fulfills a following conditional formula: −1×10−2<(N′−N)×(X(H)−X0(H))/f4<0,where N is a refractive index of a material at an object side of the aspherical surface for d line,N′ is a refractive index of a material at an image side of the aspherical surface for d line,H is a height at which an axial marginal ray passes through on the aspherical surface at the telephoto end,X(H) is a displacement of the aspherical surface along the optical axis at the height H,X0(H) is a displacement of a reference spherical surface of the aspherical surface along the optical axis at the height H, the reference surface representing a spherical surface having a same paraxial curvature-radius to the aspherical surface, andthe displacement in a direction to the image surface is represented by a positive value.

3. The image pickup optical system of claim 1, wherein the image pickup optical system fulfills a following conditional formula: −0.9<f3/f4<−0.1,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 third lens group comprises a plurality of lenses including a lens closest to the image which includes an aspherical surface.

5. The image pickup optical system of claim 1, wherein the fifth lens group has a positive power and consists of one lens including at least an aspherical surface.

6. 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.