Zoom lens and image pickup apparatus having the same
A zoom lens includes, in order from an object side to an image side, a first lens unit having positive refractive power, a second lens unit having negative refractive power, and a rear lens group having a plurality of lens units at least one of which has positive refractive power. The distance between the first lens unit and the second lens unit is greater at a telephoto end than at a wide angle end. The first lens unit includes a positive lens and a negative lens. The rear lens group includes a lens unit R comprising a positive lens and a negative lens. The lens unit R has the highest zoom ratio among the lens units included in the rear lens group. The materials of the positive and negative lenses included in the first lens unit and in the lens unit R are selected appropriately based on predetermined mathematical conditions.
1. A zoom lens comprising, in order from an object side to an image side:
a first lens unit having positive refractive power;
a second lens unit having negative refractive power; and
a rear lens group having a plurality of lens units at least one of which has positive refractive power,
wherein the distance between the first lens unit and the second lens unit is greater at a telephoto end as compared to at a wide angle end,
wherein the first lens unit includes a positive lens and a negative lens,
wherein the rear lens group includes a lens unit R comprising a positive lens and a negative lens, the lens unit R having the highest zoom ratio among the lens units included in the rear lens group,
and wherein the conditional expressions
5.0<ν d 1 n< 27.0
5.0<ν dRn< 27.0
θ gF 1 n< 2.381×10 −4 ·νd 1 n 2 −1.448×10 −2 ·νd 1 n+ 0.8223
θ gFRn< 2.381×10 −4 ·νdRn 2 −1.448×10 −2 ·νdRn+ 0.8223
−0.00150<(θ gF 1 n−θgF 1 p )/(ν d 1 n−νd 1 p )
−0.00150<(θ gFRn−θgFRp )/(ν dRn−νdRp )
are satisfied, where
of the positive lenses included in the first lens unit,
νd1p represents the Abbe number of the material of the positive lens of which the Abbe number of the lens material is the greatest, and
θgF1p represents the partial dispersion ratio thereof,
of the negative lenses included in the first lens unit,
νd1n represents the Abbe number of the material of the negative lens of which the Abbe number of the lens material is the smallest, and
θgF1n represents the partial dispersion ratio thereof,
of the positive lenses included in the lens unit R,
νdRp represents the Abbe number of the material of the positive lens of which the Abbe number of the lens material is the greatest, and
θgFRp represents the partial dispersion ratio thereof, and
of the negative lenses included in the lens unit R,
νdRn represents the Abbe number of the material of the negative lens of which the Abbe number of the lens material is the smallest, and
θgFRn represents the partial dispersion ratio thereof.
2. The zoom lens according to claim 1 ,
wherein the conditional expression
0.10< f 1 /ft< 0.70
is satisfied, where f 1 represents the focal length of the first lens unit, and ft represents the focal length of the zoom lens at the telephoto end.
3. The zoom lens according to claim 1 ,
wherein the conditional expression
−0.200< f 2 /ft<− 0.010
is satisfied, where f 2 represents the focal length of the second lens unit, and ft represents the focal length of the zoom lens at the telephoto end.
4. The zoom lens according to claim 1 ,
wherein the conditional expression
0.020< fR/ft< 0.300
is satisfied, where fR represents the focal length of the lens unit R, and ft represents the focal length of the zoom lens at the telephoto end.
5. The zoom lens according to claim 1 ,
wherein the conditional expression
−4.00< f 1 n/f 1<−1.00
is satisfied, where f1n represents the focal length of the negative lens of which the lens material has the smallest Abbe number of the negative lenses included in the first lens unit, and f1 represents the focal length of the first lens unit.
6. The zoom lens according to claim 1 ,
wherein the conditional expression
−3.00< fRn/fR<− 1.00
is satisfied, where fRn represents the focal length of the negative lens of which the lens material has the smallest Abbe number of the negative lenses included in the lens unit R, and fR represents the focal length of the lens unit R.
7. The zoom lens according to claim 1 ,
wherein the conditional expression
−10.00< M 1 /fw<− 1.00
is satisfied, where fw represents the focal length of the zoom lens at the wide angle end, and M1 represents the amount of movement on the optical axis of the first lens unit, when zooming from the wide angle end to the telephoto end.
8. The zoom lens according to claim 1 ,
wherein the conditional expression
−4.00< M 2 /fw< 3.00
is satisfied, where fw represents the focal length of the zoom lens at the wide angle end, and M 2 represents the amount of movement on the optical axis of the second lens unit, when zooming from the wide angle end to the telephoto end.
9. The zoom lens according to claim 1 ,
wherein the conditional expression
−8.00< MR/fw<− 1.00
is satisfied, where fw represents the focal length of the zoom lens at the wide angle end, and MR represents the amount of movement on the optical axis of the lens unit R, when zooming from the wide angle end to the telephoto end.
10. The zoom lens according to claim 1 ,
wherein the rear unit consists of a third lens unit having positive refractive power, and a fourth lens unit having positive refractive power.
11. The zoom lens according to claim 1 ,
wherein the rear unit consists of a third lens unit having positive refractive power, a fourth lens unit having negative refractive power, and a fifth lens unit having positive refractive power.
12. The zoom lens according to claim 1 ,
wherein the rear unit consists of a third lens unit having negative refractive power, a fourth lens unit having positive refractive power, a fifth lens unit having negative refractive power, and a sixth lens unit having positive refractive power.
13. An image pickup apparatus comprising:
a zoom lens; and
an image sensor configured to receive an image formed by the zoom lens,
wherein the zoom lens comprises, in order from an object side to an image side:
a first lens unit having positive refractive power,
a second lens unit having negative refractive power, and
a rear lens group having a plurality of lens units at least one of which has positive refractive power,
wherein the distance between the first lens unit and the second lens unit is greater at a telephoto end as compared to at a wide angle end,
wherein the first lens unit includes a positive lens and a negative lens,
wherein the rear lens group includes a lens unit R comprising a positive lens and a negative lens, the lens unit R having the highest zoom ratio among the lens units included in the rear lens group,
and wherein the conditional expressions
5.0<ν d 1 n< 27.0
5.0<ν dRn< 27.0
θ gF 1 n< 2.381×10 −4 ·νd 1 n 2 −1.448×10 −2 ·νd 1 n+ 0.8223
θ gFRn< 2.381×10 −4 ·νdRn 2 −1.448×10 −2 ·νdRn+ 0.8223
−0.00150<(θ gF 1 n−θgF 1 p )/(ν d 1 n−νd 1 p )
−0.00150<(θ gFRn−θgFRp )/(ν dRn−νdRp )
are satisfied, where
of the positive lenses included in the first lens unit,
νd1p represents the Abbe number of the material of the positive lens of which the Abbe number of the lens material is the greatest, and
θgF1p represents the partial dispersion ratio thereof,
of the negative lenses included in the first lens unit,
νd1n represents the Abbe number of the material of the negative lens of which the Abbe number of the lens material is the smallest, and
θgF1n represents the partial dispersion ratio thereof,
of the positive lenses included in the lens unit R,
νdRp represents the Abbe number of the material of the positive lens of which the Abbe number of the lens material is the greatest, and
θgFRp represents the partial dispersion ratio thereof, and
of the negative lenses included in the lens unit R,
νdRn represents the Abbe number of the material of the negative lens of which the Abbe number of the lens material is the smallest, and
θgFRn represents the partial dispersion ratio thereof.