Imaging lens
A compact high-resolution imaging lens which meets the demands for low-profileness, a low F-value and a wide field of view and corrects aberrations properly. It includes, in order from the object side: a first positive lens having a convex object-side surface; a second negative lens having a convex object-side surface; a third lens; a fourth positive lens; and a fifth negative double-sided aspheric lens having a concave image-side surface. When Fno denotes F-number, ih maximum image height, TTL total track length, f45 the composite focal length of the fourth and fifth lenses, r5 and r6 the curvature radii of the third lens object-side and image-side surfaces, r7 and r8 the curvature radii of the fourth lens object-side and image-side surfaces, and r9 and r10 the curvature radii of the fifth lens object-side and image-side surfaces, respectively, it satisfies the following conditions: Fno≦2.4; TTL/2ih<0.9; f45<0; 0<r5/r6<4.0; 0.5<(r7+r8)/(r7−r8)<3.0; and 0.4<(r9+r10)/(r9−r10)<4.0.
1. An imaging lens which forms an image of an object on a solid-state image sensor, comprising, in order from an object side to an image side of the imaging lens:
a first lens with positive refractive power having a convex surface facing the object side;
a second lens with negative refractive power having a convex surface facing the object side;
a third lens with positive or negative refractive power;
a fourth lens with positive refractive power; and
a fifth lens with negative refractive power that is a double-sided aspheric lens having a concave surface facing the image side,
wherein conditional expressions (1a), (2), (3), (4), (5a), and (6) below are satisfied:
Fno≦ 2.3 (1a)
TTL/ 2 ih< 0.9 (2)
f 45<0 (3)
0< r 5/ r 6<4.0 (4)
0.5<( r 7+ r 8)/( r 7− r 8)<2.0 (5a)
0.4<( r 9+ r 10)/( r 9− r 10)<4.0 (6)
where
Fno: F-number
ih: maximum image height
TTL: total track length
f45: composite focal length of the fourth lens and the fifth lens
r5: curvature radius of an object-side surface of the third lens
r6: curvature radius of an image-side surface of the third lens
r7: curvature radius of an object-side surface of the fourth lens
r8: curvature radius of an image-side surface of the fourth lens
r9: curvature radius of an object-side surface of the fifth lens
r10: curvature radius of an image-side surface of the fifth lens.
2. The imaging lens according to claim 1 , wherein a conditional expression (7) below is satisfied:
3.0<| f 3/ f 1 (7)
where
f: overall focal length of the imaging lens
f3: focal length of the third lens.
3. The imaging lens according to claim 1 , wherein a conditional expression (8) below is satisfied:
0.4< f 4/ f< 1.5 (8)
where
f: overall focal length of the imaging lens
f4: focal length of the fourth lens.
4. The imaging lens according to claim 1 , wherein a conditional expression (9) below is satisfied:
−1.2< f 5/ f<− 0.2 (9)
where
f: overall focal length of the imaging lens
f5: focal length of the fifth lens.
5. The imaging lens according to claim 1 , wherein a conditional expression (10) below is satisfied:
0.08< T 3/ TTL< 0.16 (10)
where
T3: distance on an optical axis between the image-side surface of the third lens and the object-side surface of the fourth lens.
6. The imaging lens according to claim 1 , wherein a conditional expression (11) below is satisfied:
0.5< f 1/ f< 2.0 (11)
where
f: overall focal length of the imaging lens
f1: focal length of the first lens.
7. The imaging lens according to claim 1 , wherein a conditional expression (12) below is satisfied:
1.5< r 3/ r 4<50 (12)
where
r3: curvature radius of an object-side surface of the second lens
r4: curvature radius of an image-side surface of the second lens.
8. The imaging lens according to claim 1 , wherein the fourth lens has a convex surface on facing the image side.
9. The imaging lens according to claim 1 , wherein the fifth lens has a pole point separated from an optical axis on its image-side surface.
10. The imaging lens according to claim 1 , wherein a conditional expression (13) below is satisfied:
20< vd 1− vd 2<40 (13)
where
vd1: Abbe number of the first lens at d-ray
vd2: Abbe number of the second lens at d-ray.
11. The imaging lens according to claim 10 , wherein a conditional expression (14) below is satisfied:
50< vd 3<70 (14)
where
vd3: Abbe number of the third lens at d-ray.
12. The imaging lens according to claim 1 , wherein a conditional expression (15) below is satisfied:
0.70< ih/f< 1.0 (15)
where
f: overall focal length of the imaging lens
ih: maximum image height.
13. An imaging lens which forms an image of an object on a solid-state image sensor, comprising, in order from an object side to an image side of the imaging lens:
a first lens with positive refractive power having convex surfaces facing the object side and the image side;
a second lens with negative refractive power having a convex surface facing the object side;
a third lens with positive or negative refractive power having a meniscus shape, a convex object-side surface, and a concave image-side surface;
a fourth lens with positive refractive power; and
a fifth lens with negative refractive power that is a double-sided aspheric lens having a concave surface facing the image side,
wherein the imaging lens with a telephoto ratio (TTL/f) of less than 1.2, and
conditional expressions (1a), (2), (5a), (6), and (8′) below are satisfied:
Fno≦ 2.3 (1a)
TTL/ 2 ih< 0.85 (2a)
0.5<( r 7+ r 8)/( r 7− r 8)<2.0 (5a)
0.4<( r 9+ r 10)/( r 9− r 10)<3.0 (6a)
0.4< f 4/ f< 1.2 (8a)
where
Fno: F-number
ih: maximum image height
TTL: total track length
r7: curvature radius of an object-side surface of the fourth lens
r8: curvature radius of an image-side surface of the fourth lens
r9: curvature radius of an object-side surface of the fifth lens
r10: curvature radius of an image-side surface of the fifth lens
f: overall focal length of the imaging lens
f4: focal length of the fourth lens.
14. The imaging lens according to claim 13 , wherein a conditional expression (7) below is satisfied:
3.0<| f 3/ f 1 (7)
where
f3: focal length of the third lens.
15. The imaging lens according to claim 13 , wherein a conditional expression (10) below is satisfied:
0.08< T 3/ TTL< 0.16 (10)
where
T3: distance on an optical axis between the image-side surface of the third lens and the object-side surface of the fourth lens.
16. The imaging lens according to claim 13 , wherein a conditional expression (15) below is satisfied:
0.70< ih/f< 1.0 (15).
17. An imaging lens which forms an image of an object on a solid-state image sensor, comprising, in order from an object side to an image side of the imaging lens:
a first lens with positive refractive power having a convex surface facing the object side;
a second lens with negative refractive power having a convex surface facing the object side;
a third lens with positive or negative refractive power having a meniscus shape, a concave object-side surface, and a convex image-side surface;
a fourth lens with positive refractive power having a biconvex shape; and
a fifth lens with negative refractive power that is a double-sided aspheric lens having a concave surface facing the image side,
wherein conditional expressions (1), (4), and (12b) below are satisfied:
Fno≦ 2.4 (1)
0< r 5/ r 6<4.0 (4)
2.79< r 3/ r 4<25 (12b)
where
Fno: F-number
f45: composite focal length of the fourth lens and the fifth lens
r3: curvature radius of an object-side surface of the second lens
r4: curvature radius of an image-side surface of the second lens
r5: curvature radius of the object-side surface of the third lens
r6: curvature radius of the image-side surface of the third lens.
18. The imaging lens according to claim 17 , wherein a conditional expression (10) below is satisfied:
0.08< T 3/ TTL< 0.16 (10)
where
T3: distance on an optical axis between the image-side surface of the third lens and an object-side surface of the fourth lens
TTL: total track length.
19. The imaging lens according to claim 17 , wherein a conditional expression (15) below is satisfied:
0.70< ih/f< 1.0 (15)
where
f: overall focal length of the imaging lens
ih: maximum image height.
20. The imaging lens according to claim 17 , wherein a conditional expression (2) below is satisfied:
TTL/ 2 ih< 0.9 (2)
where
ih: maximum image height
TTL: total track length.