Zoom lens and image pick-up apparatus using zoom lens
A zoom lens composed of plural groups and adapted for changing group spacing or spacings, and includes, in a first group GR 1 fixed during zooming operation, a reflection member M for bending or folding the optical axis substantially by 90 degrees and a negative group at the object side relative to the reflection member M. At the image side of the first group GR 1 , there are at least included a second group GR 2 movable during zooming operation and having negative refractive power, and a light quantity adjustment member ST 1 fixed during zooming operation. Angle of the reflection member M is changed at the time of sinking lens barrel so that the negative group of the first group GR 1 is accommodated into a space thus defined.
1. A zoom lens composed of plural groups and adapted to change group spacing or spacings to thereby perform magnification changing operation,
the zoom lens comprising:
a first group at least including a reflection member for bending or folding the optical axis and a negative subgroup at an object side relative to the reflection member, said first group being fixed during magnification changing operation;
a second group movably provided during magnification changing operation at an image side of the first group and having negative refractive power; and
a third group including a positive lens having non-spherical surfaces at both surface sides thereof, and a light quantity adjustment member at the image surface side, the light quantity adjustment member being fixed during magnification changing operation,
wherein the zoom lens is located within a lens barrel and said negative subgroup undergos a lens barrel sinking operation, and
wherein, when the negative subgroup is caused to undergo said lens barrel sinking operation, the reflection member is withdrawn by being rotated with a fulcrum which is not limited to one end side of the reflection member, and the negative subgroup of the first groups is accommodated into a space thus vacated by the withdrawn reflection member.
2. The zoom lens according to claim 1 ,
wherein the negative subgroup of the object side relative to the reflection member of the first group satisfies the following formula (1),
2.0 <|fa/fw|< 6.0 (1)
In the above formula,
fa: focal length of the negative subgroup of the object side relative to the reflection member of the first group, and
fw: focal length at broad angle end.
3. An image pick-up device comprising:
a zoom lens composed of plural groups and adapted to change group spacing or spacings to thereby perform magnification changing operation; and
an image pick-up device for converting an optical image which has been formed by the zoom lens into an electric signal,
the zoom lens at least including:
a first group at least including a reflection member for bending or folding the optical axis and a negative subgroup at an object side relative to the reflection member, said first group being fixed during magnification changing operation;
a second group movably provided during magnification changing operation at an image side of the first group and having negative refractive power; and
a third group including a positive lens having non-spherical surfaces at both surface sides thereof, and a light quantity adjustment member at the image surface side, the light quantity adjustment member being fixed during magnification changing operation,
wherein the zoom lens is located within a lens barrel and said negative subgroup undergos a lens barrel sinking operation, and
wherein, when the negative subgroup is caused to undergo said lens barrel sinking operation, the reflection member is withdrawn by being rotated with a fulcrum which is not limited to one end side of the reflection member so that the negative subgroup of the first group is accommodated into a space thus vacated by the withdrawn reflection member.
4. The image pick-up apparatus according to claim 3 ,
wherein the negative subgroup of the object side relative to the reflection member of the first group satisfies the following formula (2),
2.0 <|fa/fw|< 6.0 (2)
In the above formula,
fa: focal length of the negative subgroup of the object side relative to the reflection member of the first group, and
fw: focal length at broad angle end.