Imaging lens and imaging apparatus
View Patent ↗An imaging lens includes in order from an object side: a first lens including a positive lens having a convex surface directed to the object side; a stop; a second lens including a positive lens having a convex surface directed to an image side; a third lens including a negative meniscus lens with a concave surface directed to the object side; and a fourth lens including, near an optical axis, a positive meniscus shape with a convex surface directed to the object side. An air space between the second lens and the third lens is smaller in a periphery than near the optical axis. And f 1 >f 2 >|f 3 | and 1.0<f/f 2 <1.5 are satisfied where f 1 , f 2 and f 3 are focal lengths of the first lens, the second lens, and the third lens, respectively and f is an focal length of the whole lens system.
1. An imaging lens comprising in order from an object side:
a first lens that includes a positive lens having a convex surface directed to the object side;
a stop;
a second lens that includes a positive lens having a convex surface directed to an image side;
a third lens that includes a negative meniscus lens with a concave surface directed to the object side; and
a fourth lens that includes, near an optical axis, a positive meniscus shape with a convex surface directed to the object side,
wherein an air space between the second lens and the third lens is smaller in a periphery than near the optical axis, and
the following conditional expressions are satisfied:
f 1 >f 2 >|f 3| (1)
1.0 <f/f 2<1.5 (2)
where f 1 is a focal length of the first lens, f 2 is a focal length of the second lens, f 3 is a focal length of the third lens, and f is an focal length of the whole lens system.
2. The imaging lens according to claim 1 ,
wherein the following condition expression is further satisfied:
0.7 <Y max/ f <0.9 (5)
where Ymax is a maximum image height.
3. An imaging apparatus comprising:
the imaging lens according to claim 1 ; and
an imaging device that outputs an imaging signal corresponding to an optical image formed by the imaging lens.
4. The imaging lens according to claim 1 , wherein the first lens is a positive meniscus lens.
5. The imaging lens according to claim 1 , wherein the second lens is a positive meniscus lens.
6. The imaging lens according to claim 1 , wherein both surfaces of the fourth lens are aspheric.
7. The imaging lens according to claim 1 , wherein each of the first lens, the second lens, and the third lens includes at least an aspheric surface.
8. The imaging lens according to claim 1 , wherein the image side surface of the fourth lens is an aspheric surface that is concave directed to the image side near the optical axis and convex directed to the image side in the periphery.
9. The imaging lens according to claim 1 , wherein the object side surface of the fourth lens is an aspheric surface that is convex directed to the object side near the optical axis and concave directed to the object side in the periphery.
10. The imaging lens according to claim 1 , wherein the following conditional expression is further satisfied:
vd3<30 (3A)
where vd3 is an Abbe number of the third lens at the d-line.
11. The imaging lens according to claim 1 , wherein the following conditional expression is further satisfied:
0.3 <Bf/TL <0.5 (4A)
where Bf is an air equivalent back focal length and TL is an whole length which shows a distance from a most object side surface to an image surface in the optical axis.
12. The imaging lens according to claim 1 ,
wherein the following conditional expression is further satisfied:
vd3<35 (3)
where vd3 is an Abbe number of the third lens at the d-line.
13. The imaging lens according to claim 12 ,
wherein the following conditional expression is further satisfied:
0.2 <Bf/TL <0.5 (4)
where Bf is an air equivalent back focal length and TL is an whole length which shows a distance from a most object side surface to an image surface in the optical axis.
14. The imaging lens according to claim 12 ,
wherein the following condition expression is further satisfied:
0.7 <Y max/ f <0.9 (5)
where Ymax is a maximum image height.
15. An imaging apparatus comprising:
the imaging lens according to claim 12 ; and
an imaging device that outputs an imaging signal corresponding to an optical image formed by the imaging lens.
16. The imaging lens according to claim 1 ,
wherein the following conditional expression is further satisfied:
0.2 <Bf/TL <0.5 (4)
where Bf is an air equivalent back focal length and TL is an whole length which shows a distance from a most object side surface to an image surface in the optical axis.
17. The imaging lens according to claim 16 ,
wherein the following condition expression is further satisfied:
0.7 <Y max/ f <0.9 (5)
where Ymax is a maximum image height.
18. An imaging apparatus comprising:
the imaging lens according to claim 16 ; and
an imaging device that outputs an imaging signal corresponding to an optical image formed by the imaging lens.