JP2001228397A5 - - Google Patents

Claims (9)

In order from the object side, a first lens group having a positive refractive power, a second lens group having a negative refractive power, a third lens group having a positive refractive power, a fourth lens group having a negative refractive power, and a fifth lens having a positive refractive power Composed of groups,
At the time of zooming from the wide angle end to the telephoto end, the respective lens groups from the first lens group to the fifth lens group move, and the first lens group and the second lens group, and the third lens group and the fourth lens group. The first lens group and the third lens group move to the object side in the process of zooming so that the distance between the groups becomes large, and at least the third lens group, the fourth lens group, or the fifth lens group is nonlinear. A zoom lens that compensates for variations in image plane position due to zooming by moving and satisfies the following conditional expression.
2.0 <f ₁ / f _W <8.0 (1)
0.4 <| f ₂ / f _W | <1.0 (2)
0.3 <f ₃ / f _T345 <1.2 (3)
0.6 <| f ₄ | / f _T345 <5.0 (4)
0.5 <f ₅ / f _T345 <4.0 (5)
Where f ₁ is the focal length of the first lens group, f ₂ is the focal length of the second lens group, f ₃ is the focal length of the third lens group, f ₄ is the focal length of the fourth lens group, and f ₅ is the first focal length. The focal length of the five lens groups, f _W is the focal length of the entire system at the wide angle end, and f _T345 is the focal length from the third lens group to the fifth lens group at the telephoto end.   2. The zoom lens according to claim 1, wherein the focal length at the wide angle end is shorter than the effective diagonal length of the imaging plane of the optical system or the image sensor. 3. The zoom lens according to claim 1, wherein the principal ray emitted from the optical system is determined based on the following conditional expression.
10 <| Expd _W · Y | / L _W (6)
Where Expd _W is the distance on the optical axis from the imaging plane position to the exit pupil, Y is the actual maximum image height on the imaging plane, and L _W is the most object side surface of the first lens group at the wide angle end. This is the distance on the optical axis from the top of the image to the image plane. 4. The zoom lens according to claim 1, wherein the following relationship is satisfied when zooming from the wide-angle end to the telephoto end.
1.6 <Δ _1T / f _W <5.0 (7)
1.0 <Δ _3T / f _W <4.0 (8)
However, Δ _1T is the movement amount at the time of zooming to the telephoto end of the first lens group at the wide angle end reference, and Δ _3T is the movement amount at the time of zooming to the telephoto end of the third lens group at the wide angle end reference. is there. _{5. The} zoom lens according to claim 1, wherein the paraxial lateral magnification of the second lens group satisfies the following relationship: 2.5 <β _2T / β _2W <7. (9)
Here, β _2W is the imaging magnification at the wide-angle end of the second lens group, and β _2T is the imaging magnification at the telephoto end of the second lens group.   The zoom according to any one of claims 1 to 5, wherein image movement caused by movement of the entire system is corrected by moving the second lens group in a direction substantially perpendicular to the optical axis. lens.   The zoom according to any one of claims 1 to 5, wherein image movement caused by movement of the entire system is corrected by moving the third lens group in a direction substantially perpendicular to the optical axis. lens.   The zoom according to any one of claims 1 to 5, wherein image movement caused by movement of the entire system is corrected by moving the fourth lens group in a direction substantially perpendicular to the optical axis. lens.   The zoom according to any one of claims 1 to 5, wherein image movement caused by movement of the entire system is corrected by moving the fifth lens group in a direction substantially perpendicular to the optical axis. lens.