Zoom lens
A zoom lens having less distortion and exhibiting good imaging performance is provided. A zoom lens includes a first lens unit provided at the extremity of an enlargement conjugate side and having a negative refractive power, and a final lens unit provided at the extremity of a reduction conjugate side and having a positive refractive power. The final lens unit includes a cemented lens at the extremity of the reduction conjugate side. The cemented lens has a positive refractive power. The zoom lens satisfies specific conditional expressions.
1. A zoom lens comprising:
a first lens unit provided nearest to an enlargement conjugate side and having a negative refractive power; and
a final lens unit provided at nearest to a reduction conjugate side and having a positive refractive power, the final lens unit including a cemented lens provided nearest to the reduction conjugate side, the cemented lens having a positive refractive power and including a positive lens element and a negative lens element,
wherein the zoom lens satisfies the following conditions:
ν N −ν P >0
n N −n P >0
2.0< fe/fw< 4.74
where n P and ν P denote a refractive index and an Abbe number, respectively, of the positive lens element; n N and ν N denote a refractive index and an Abbe number, respectively, of the negative lens element; fe denotes a focal length of the final lens unit; and fw denotes a focal length of the zoom lens at a wide-angle end.
2. The zoom lens according to claim 1 , wherein the positive lens element is provided on the enlargement conjugate side with respect to the negative lens element.
3. The zoom lens according to claim 1 , wherein the negative lens element is provided on the enlargement conjugate side with respect to the positive lens element.
4. The zoom lens according to claim 1 , wherein the cemented lens is stationary during zooming.
5. The zoom lens according to claim 1 ,
wherein the first lens unit and the final lens unit are stationary during zooming, and
wherein zooming is performed by moving at least one lens unit provided between the first lens unit and the final lens unit.
6. The zoom lens according to claim 1 , satisfying the following condition:
ν N −ν P >5.0
7. The zoom lens according to claim 1 , satisfying the following condition:
1
f
·
(
1
f
p
v
p
+
1
f
n
v
n
)
<
30
where f denotes a focal length of the cemented lens, f P denotes a focal length of the positive lens element, and f N denotes a focal length of the negative lens element.
8. An image projection apparatus comprising:
the zoom lens according to claim 1 ; and
an image display device provided on the reduction conjugate side with respect to the zoom lens,
wherein light from the image display device is projected on a surface of projection through the zoom lens.
9. A zoom lens comprising:
a first lens unit provided nearest to an enlargement conjugate side and having a negative refractive power; and
a final lens unit provided at nearest to a reduction conjugate side and having a positive refractive power, the final lens unit including a cemented lens provided nearest to the reduction conjugate side, the cemented lens having a positive refractive power and including a positive lens element and a negative lens element,
wherein the zoom lens satisfies the following conditions:
ν N −ν P >0
n N −n P >0
2.0< fe/fw< 6.5
where n p and V p denote a refractive index and an Abbe number, respectively, of the positive lens element; n N and v N denote a refractive index and an Abbe number, respectively, of the negative lens element; fe denotes a focal length of the final lens unit;
and fw denotes a focal length of the zoom lens at a wide-angle end,
wherein the zoom lens includes a total of 5 lens units including the first and final lens units.
10. The zoom lens according to claim 9 , wherein the positive lens element is provided on the enlargement conjugate side with respect to the negative lens element.
11. The zoom lens according to claim 9 , wherein the negative lens element is provided on the enlargement conjugate side with respect to the positive lens element.
12. The zoom lens according to claim 9 , wherein the cemented lens is stationary during zooming.
13. The zoom lens according to claim 9 , wherein the first lens unit and the final lens unit are stationary during zooming, and wherein zooming is performed by moving at least one lens unit provided between the first lens unit and the final lens unit.
14. The zoom lens according to claim 9 , satisfying the following condition:
ν N −ν P >5.0.
15. The zoom lens according to claim 9 , satisfying the following condition:
1
f
·
(
1
f
p
v
p
+
1
f
n
v
n
)
<
30
where f denotes a focal length of the cemented lens, f p denotes a focal length of the positive lens element, and f N denotes a focal length of the negative lens element.
16. An image projection apparatus comprising:
the zoom lens according to claim 9 ; and
an image display device provided on the reduction conjugate side with respect to the zoom lens,
wherein light from the image display device is projected on a surface of projection through the zoom lens.
17. A zoom lens comprising:
a first lens unit provided nearest to an enlargement conjugate side and having a negative refractive power; and
a final lens unit provided at nearest to a reduction conjugate side and having a positive refractive power, the final lens unit including a cemented lens provided nearest to the reduction conjugate side, the cemented lens having a positive refractive power and including a positive lens element and a negative lens element,
wherein the zoom lens satisfies the following conditions:
ν N −ν P >0
n N −n P >0
2.0< fe/fw< 6.5
where n p and V p denote a refractive index and an Abbe number, respectively, of the positive lens element; n N and v N denote a refractive index and an Abbe number, respectively, of the negative lens element; fe denotes a focal length of the final lens unit;
and fw denotes a focal length of the zoom lens at a wide-angle end, wherein the zoom lens includes a total of 6 lens units including the first and final lens units.
18. A zoom lens comprising:
a first lens unit provided nearest to an enlargement conjugate side and having a negative refractive power; and
a final lens unit provided at nearest to a reduction conjugate side and having a positive refractive power, the final lens unit including a cemented lens provided nearest to the reduction conjugate side, the cemented lens having a positive refractive power and including a positive lens element and a negative lens element,
wherein the zoom lens satisfies the following conditions:
ν N −ν P >0
n N - n P >0
2.0< fe/fw < 6.5
where n p and V p denote a refractive index and an Abbe number, respectively, of the positive lens element; n N and v N denote a refractive index and an Abbe number, respectively, of the negative lens element; fe denotes a focal length of the final lens unit;
and fw denotes a focal length of the zoom lens at a wide-angle end,
wherein the zoom lens includes more than 7 lens units including the first and final lens units.