Zoom optical system and imaging apparatus using the same
A zoom optical system includes at least two optical-element groups and a variable optical-property optical element. The two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change. The optical element has a focusing function and is disposed on the image side of the optical-element groups. According to this configuration of the zoom optical system, it is possible to attain a zoom optical system and an imaging apparatus using the zoom optical system that have as small a number of movable lenses as possible, are very small in size, and work with an extremely low power consumption and low operation noise.
1. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the zoom optical sytem comprises an optical-element group that is disposed on a imagemost side, the variable optical-property optical element being arranged in the optical-element group that is disposed on the imagemost side.
2. A zoom optical system according to claim 1 , wherein the variable optical-property optical element has a rotationally asymmetric curved surface that has a function for compensating for decentered aberrations.
3. A zoom optical system according to claim 1 , wherein the following condition is satisfied:
70°≦Φ≦110°
where Φ is an angle of turning of an optical axis caused by the variable optical-property optical element.
4. A zoom optical system according to claim 1 , wherein the variable optical-property optical element is driven by one of an electrostatic force, an electromagnetic force, a piezoelectric effect, and fluid.
5. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the following conditions are satisfied:
0.5 <EX W /f W <50.0
0.5 <EX T /f T <50.0
where EX W is a physical distance from an exit pupil position of an optical system as viewed from the variable optical-property optical element to the variable optical-property optical element at a wide-angle end, EX T is a physical distance from an exit pupil position of the optical system as viewed from the variable optical-property optical element to the variable optical-property optical element at a telephoto end, f W is a focal length of the entire optical system at the wide-angle end, and f T is a focal length of the entire optical system at the telephoto end.
6. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the following condition is satisfied:
0.3<ξ w <0.9
where ξ w is a magnification of a group of optical elements arranged between the variable optical-property optical element and an image surface.
7. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the following condition is satisfied:
−5.0<( f a /f b )× f W <−0.5
where f a is a focal length, at a wide-angle end, of a group of optical elements arranged on an object side of an aperture stop, f b is a focal length, at the wide-angle end, of a group of optical elements arranged on an image side of the aperture stop, and f W is a focal length of the entire system at the wide-angle end.
8. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the following condition is satisfied:
D< 20.0 mm
where D is an effective diameter of the variable optical-property optical element.
9. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups,
wherein the zoom optical sytem comprises, in order from an object side:
a first optical-element group having a negative optical power;
a second optical-element group having a positive optical power,
a third optical-element group having a positive optical power; and
a fourth optical-element group having a positive optical power, and
wherein the two optical-element groups movable in the magnification change are the second optical-element group and the third optical-element group.
10. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups,
wherein the zoom optical sytem comprises, in order from an object side:
a first optical-element group having a negative optical power;
a second optical-element group having a positive optical power; and
a third optical-element group having a positive optical power, and
wherein at least the second optical-element group has the magnification varying function.
11. A zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups,
wherein the zoom optical system comprises, in order from an object side:
a first optical-element group having a negative optical power;
a second optical-element group having a positive optical power;
a third optical-element group having a positive optical power; and
a fourth optical-element group having a positive optical power, and
wherein at least the second optical-element group has the magnification varying function.
12. An imaging apparatus comprising a zoom optical system,
the zoom optical system comprising:
at least two optical-element groups; and
a variable optical-property optical element,
wherein the two optical-element groups are movable in a magnification change and have a magnification varying function or a compensating function for compensating for a shift of an image surface caused by the magnification change,
wherein the variable optical-property optical element has a focusing function and is disposed on an image side of the optical-element groups, and
wherein the zoom optical system comprises an optical-element group that is disposed on a imagemost side, the variable optical-property optical element being arranged in the optical-element group that is disposed on the imagemost side.