Zoom lens and image pickup apparatus using the same
View Patent ↗A zoom lens comprising in order from an object side, a first lens unit having a negative refractive power, a second lens unit having a negative refractive power, a lens unit having a positive refractive power, and a rearmost lens unit having a negative refractive power, and the rearmost lens unit is positioned nearest to an image in the plurality of lens units, and at the time of zooming, distances between the lens units in the plurality of lens units change. Moreover, an image pickup apparatus includes the zoom lens, and an image pickup element having an image pickup surface.
1. A zoom lens comprising in order from an object side:
a first lens unit having a negative refractive power;
a second lens unit having a negative refractive power;
a lens unit having a positive refractive power; and
a rearmost lens unit having a negative refractive power, wherein
the total number of lens units in the zoom lens is four, and
at the time of zooming, distances between the lens units change, and
at the time of focusing from an infinite object point to an object point at a short distance, only the second lens unit moves, and
the second lens unit comprises one negative lens, and
the total number of lenses in the second lens unit is one, and
the negative lens is a meniscus lens having a convex surface directed toward an image side, and
at the time of focusing from the infinite object point to an object point at a short distance, the negative lens moves toward the object side, and
the following conditional expressions are satisfied:
2.00<| S t |<8.00
−6.00<( r ff +r fb )/( r ff −r fb )<−1.00
where,
S t =(1−β 2t ×β 2t )×β ct ×β ct ,
β 2t denotes a lateral magnification of the second lens unit,
β ct denotes a combined lateral magnification of all the lens units positioned on the image side of the second lens unit,
both β 2t and β ct are a lateral magnification at the time of focusing on the infinite object point at a telephoto end,
r ff denotes a radius of curvature of an object-side lens surface of the negative lens, and
r fb denotes a radius of curvature of an image-side lens surface of the negative lens.
2. A zoom lens comprising in order from an object side:
a first lens unit having a negative refractive power;
a second lens unit having a negative refractive power;
a lens unit having a positive refractive power; and
a rearmost lens unit having a negative refractive power, wherein
the total number of lens units in the zoom lens is four, and
at the time of zooming, distances between the lens units change, and
at the time of focusing from an infinite object point to an object point at a short distance, only the second lens unit moves, and
the following conditional expressions are satisfied:
2.00<| S t |<8.00
0.30< D 1L /D 1a <4.00
where,
S t =(1−β 2t ×β 2t )×β ct ×β ct ,
β 2t denotes a lateral magnification of the second lens unit,
β ct denotes a combined lateral magnification of all the lens units positioned on the image side of the second lens unit,
both β 2t and β ct are a lateral magnification at the time of infinite object point focusing at a telephoto end,
D 1L denotes a sum total of a lens thickness on an optical axis of the first lens unit, and
D 1a denotes a sum total of an air space on the optical axis in the first lens unit.
3. The zoom lens according to claim 1 , comprising:
an aperture stop, wherein
the aperture stop is disposed between two lenses, and
one of the two lenses is positioned nearest to an image in the second lens unit, and the remaining of the two lenses is positioned nearest to an object in the rearmost lens unit, and
at the time of zooming from a wide angle end to a telephoto end, the aperture stop moves toward the object side.
4. The zoom lens according to claim 3 , wherein the following conditional expression is satisfied:
1.00< D aiw /(tan ω t ×f t )<5.00
where,
D aiw denotes a distance between the aperture stop and an image plane at the wide angle end,
ω t denotes a half angle of view at the telephoto end, and
f t denotes a focal length of the overall zoom lens system at the telephoto end.
5. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.70<β 1w <2.00
where,
β 1w denotes a lateral magnification of the rearmost lens unit at the time of infinite object point focusing at the wide angle end.
6. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.20<(β 1t /β 1w )/( f t /f w )<0.90
where,
β 1t denotes a lateral magnification of the rearmost lens unit at the telephoto end,
β 1w denotes a lateral magnification of the rearmost lens unit at the wide angle end, and both β 1t and β 1w are lateral magnification at the time of infinite object point focusing,
f t denotes a focal length of the overall zoom lens system at the telephoto end, and
f w denotes a focal length of the overall zoom lens system at the wide angle end.
7. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.94<(β 2t /β 2w )<1.09
where,
β 2t denotes the lateral magnification of the second lens unit at the telephoto end, and
β 2w denotes a lateral magnification of the second lens unit at the wide angle end, and both β 2t and β 2w are lateral magnification at the time of infinite object point focusing.
8. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.80<EXP w /(tan ω t ×f t )<3.00
where,
EXP w denotes a distance between the image plane and an exit pupil at the wide angle end,
ω t denotes a half angle of view at the telephoto end, and
f t denotes a focal length of the overall zoom lens system at the telephoto end.
9. The zoom lens according to claim 2 , wherein
the second lens unit includes one negative lens, and
the total number of lenses in the second lens unit is one.
10. The zoom lens according to claim 9 , wherein
the negative lens is a meniscus lens having a convex surface directed toward an image side, and
at the time of focusing from the infinite object point to the object point at the short distance, the negative lens moves toward the object side, and
the following conditional expression is satisfied:
−6.00<( r ff +r fb )/( r ff −r fb )<−1.00
where,
r ff denotes a radius of curvature of the object-side lens surface of the negative lens, and
r fb denotes a radius of curvature of the image-side lens surface of the negative lens.
11. A zoom lens comprising in order from an object side:
a first lens unit having a negative refractive power;
a second lens unit having a negative refractive power;
a lens unit having a positive refractive power; and
a rearmost lens unit having a negative refractive power, wherein
the total number of lens units in the zoom lens is four, and
at the time of zooming, distances between lens units change, and
the following conditional expressions are satisfied:
−5.50< f 2 /f w <−1.00
0.30< D 1L /D 1a <4.00
where,
f 2 denotes a focal length of the second lens unit,
f w denotes a focal length of the overall zoom lens system at a wide angle end,
D 1L denotes a sum total of a lens thickness on an optical axis of the first lens unit, and
D 1a denotes a sum total of an air space on the optical axis in the first lens unit.
12. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
−6.00< f 1 /f w <−1.00
where,
f 1 denotes a focal length of the first lens unit, and
f w denotes a focal length of the overall zoom lens system at the wide angle end.
13. A zoom lens comprising in order from an object side:
a first lens unit having a negative refractive power;
a second lens unit having a negative refractive power;
a lens unit having a positive refractive power; and
a rearmost lens unit having a negative refractive power, wherein
the total number of lens units in the zoom lens is four, and
at the time of zooming, distances between the lens units change, and
a lens nearest to an image in the rearmost lens unit, and the first lens unit, satisfy the following conditional expressions:
−3.00<( r 1f +r 1b )/( r 1f −r 1b )<−0.30
| r 1f |<|r 1b |
0.30< D 1L /D 1a <4.00
where,
r 1f denotes a radius of curvature of an object-side lens surface of a lens positioned nearest to the image in the rearmost lens unit,
r 1b denotes a radius of curvature of an image-side lens surface of a lens positioned nearest to the image in the rearmost lens unit,
D 1L denotes a sum total of a lens thickness on an optical axis of the first lens unit, and
D 1a denotes a sum total of an air space on the optical axis in the first lens unit.
14. The zoom lens according to claim 1 , wherein at the time of zooming from a wide angle end to a telephoto end, the rearmost lens unit moves toward the object side.
15. The zoom lens according to claim 1 , wherein the following conditional expression is satisfied:
0.30< D 1L /D 1a <4.00
where,
D 1L denotes a sum total of a lens thickness on an optical axis of the first lens unit, and
D 1a denotes a sum total of an air space on the optical axis in the first lens unit.
16. The zoom lens according to claim 1 , wherein
the first lens unit comprises at least one negative lens and one positive lens, and
the total number of positive lenses in the first lens unit is one.
17. A zoom lens comprising in order from an object side:
a first lens unit having a negative refractive power;
a second lens unit having a negative refractive power;
a lens unit having a positive refractive power; and
a rearmost lens unit having a negative refractive power, wherein
the zoom lens further includes an aperture stop, and
the total number of lens units in the zoom lens is four, and
the lens unit having a positive refractive power is a third lens unit, and
spaces between lenses in the third lens unit are kept unchanged during zooming, and
the rearmost lens unit is a fourth lens unit, and
the aperture stop is disposed in the third lens unit, and
the zoom lens includes at least one aspheric lens, and
at the time of zooming, distances between the lens units change, and
the following conditional expression is satisfied:
0.30< D 1L /D 1a <4.00
where,
D 1L denotes a sum total of a lens thickness on an optical axis of the first lens unit, and
D 1a denotes a sum total of an air space on the optical axis in the first lens unit.
18. An image pickup apparatus comprising:
a zoom lens according to claim 1 ; and
an image pickup element having an image pickup surface.