Imaging lens and imaging apparatus
View Patent ↗An imaging lens provided with a negative first lens group and a positive second lens group arranged in order from the object side. The first lens group is composed of a first group first lens which is a negative single lens, and the second lens group is composed of a positive second group first lens, a positive second group second lens, and a negative second group third lens arranged in order from the object side. The second group first lens is a biconvex lens, the second group second lens is a biconvex lens, the second group third lens is a meniscus lens, an aperture stop is disposed between the second group first and second lenses, and the second group second and third lenses form a cemented lens. The imaging lens satisfies conditional expressions (1): −0.89≦f1/f<0 and (4): 0.3<dt1/f<0.8.
1. An imaging lens consisting of a first lens group having a negative refractive power and a second lens group having a positive refractive power, disposed in order from the object side, wherein:
the first lens group is composed of a first group first lens which is a single lens having a negative refractive power;
the second lens group consists of a second group first lens having a positive refractive power, a second group second lens having a positive refractive power, and a second group third lens having a negative refractive power, disposed in order from the object side;
the second group first lens is a biconvex lens;
the second group second lens is a biconvex lens;
the second group third lens is a meniscus lens;
an aperture stop is disposed between the second group first lens and the second group second lens, and the second group second lens and the second group third lens are cemented together to form a cemented lens; and
the imaging lens satisfies conditional expressions (1a) and (4) given below:
−0.85≦ f 1 /f< 0.3 (1a); and
0.3 <dt 1/ f< 0.8 (4),
where:
f 1 : the focal length of the first group first lens;
f: the focal length of the entire lens system; and
dt 1 : the thickness of the first group first lens on the optical axis.
2. The imaging lens of claim 1 , wherein the imaging lens satisfies a conditional expression (1b) given below:
−0.72≦ f 1/ f<− 0.5 (1b).
3. The imaging lens of claim 1 , wherein the imaging lens satisfies a conditional expression (4a) given below:
0.31 <dt 1 /f< 0.6 (4a).
4. The imaging lens of claim 3 , wherein the imaging lens satisfies a conditional expression (4b) given below:
0.32 <dt 1 /f< 0.5 (4b).
5. The imaging lens of claim 1 , wherein the imaging lens satisfies a conditional expression ( 5 ) given below:
0 <fg 2 /f< 1.3 (5),
where,
fg 2 : the combined focal length of the entire second lens group.
6. The imaging lens of claim 5 , wherein the imaging lens satisfies a conditional expression (5a) given below:
0.3 <fg 2 /f< 1.28 (5a).
7. The imaging lens of claim 5 , wherein the imaging lens satisfies a conditional expression (5b) given below:
0.5 <fg 2 /f< 1.25 (5b).
8. The imaging lens of claim 1 , wherein the imaging lens satisfies a conditional expression (6) given below:
35 <νd 2<70 (6),
where,
νd: the Abbe number of the second group first lens with reference to the d-line.
9. The imaging lens of claim 8 , wherein the imaging lens satisfies a conditional expression (6a) given below:
38 <νd 2<68 (6a).
10. The imaging lens of claim 8 , wherein the imaging lens satisfies a conditional expression (6b) given below:
40 <νd 2<66 (6b).
11. The imaging lens of claim 1 , wherein the imaging lens satisfies a conditional expression (7) given below:
13.5 <dsi< 22 (7),
where,
dsi: the distance between the aperture stop and the image plane on the optical axis(the back focus portion is expressed in terms of air equivalent distance).
12. The imaging lens of claim 11 , wherein the imaging lens satisfies a conditional expression (7a) given below:
13.8 <dsi< 20 (7a).
13. The imaging lens of claim 11 , wherein the imaging lens satisfies a conditional expression (7b) given below:
14 <dsi< 18 (7b).
14. An imaging apparatus, comprising the imaging lens of claim 1 .
15. The imaging lens of claim 3 , wherein the imaging lens satisfies a conditional expression (4a) given below:
0.31 <dt 1 /f< 0.6 (4a).
16. The imaging lens of claim 15 , wherein the imaging lens satisfies a conditional expression (4b) given below:
0.32 <dt 1 /f< 0.5 (4b).
17. The imaging lens of claim 2 , wherein the imaging lens satisfies a conditional expression (5) given below:
0 <fg 2 /f< 1.3 (5),
where,
fg 2 : the combined focal length of the entire second lens group.
18. The imaging lens of claim 17 , wherein the imaging lens satisfies a conditional expression (5a) given below:
0.3 <fg 2 /f< 1.28 (5a).
19. The imaging lens of claim 17 , wherein the imaging lens satisfies a conditional expression (5b) given below:
0.5 <fg 2 /f< 1.25 (5b).
20. The imaging lens of claim 1 , wherein the first group first lens is a biconcave lens.