Imaging lens and imaging device
View Patent ↗An imaging lens includes, in order from an object side, a first lens G 1 , a second lens G 2 , a third lens G 3 , an aperture stop St and a fourth lens G 4 . The first lens is a negative lens having a meniscus shape with a convex surface directed to the object side. The second lens is a negative lens. The third lens is a positive lens having a convex surface directed to the object side. The fourth lens is a biconvex lens. The following conditional expression is satisfied: 1.5< f 4/ fa <2.7 (1) where fa denotes a focal length of the whole lens system, and f 4 denotes a focal length of the fourth lens.
1. An imaging lens comprising, in order from an object side:
a first lens that is a negative lens having a meniscus shape with a convex surface directed to the object side;
a second lens that is a negative lens;
a third lens that is a positive lens having a convex surface directed to the object side;
an aperture stop; and
a fourth lens that is a biconvex lens, wherein
the following conditional expression is satisfied:
2.111 <f 4 /fa≦ 2.7 (1)
where fa denotes a focal length of the whole lens system, and
f 4 denotes a focal length of the fourth lens; and wherein the following conditional expression is satisfied:
−3.0<( r 3+ r 4)/( r 3− r 4)<0.2 (3A)
where r 3 denotes a curvature radius of an object-side surface of the second lens, and
r 4 denotes a curvature radius of an image-side surface of the second lens.
2. The imaging lens according to claim 1 , wherein the following conditional expression is satisfied:
−10.0 <f 1 /fa<− 2.5 (2)
where fa denotes a focal length of the whole lens system,
f 1 denotes a focal length of the first lens.
3. The imaging lens according to claim 2 , wherein the following conditional expression is satisfied:
−10.0< f 1 /fa≦− 6.105. (2)
4. The imaging lens according to claim 1 , wherein an object-side surface of the second lens includes an aspheric surface that has a concave shape toward the object side in a vicinity of an optical axis and has a convex shape toward the object side in a peripheral portion.
5. The image lens according to claim 1 , wherein the aperture stop is positioned to satisfy the following conditional expression:
d 6/( d 7+ d 8)<0.5 (4)
where d 6 denotes a distance, on an optical axis, between the third lens and the aperture stop,
d 7 denotes a distance, on the optical axis, between the aperture stop and the fourth lens, and
d 8 denotes a center thickness of the fourth lens.
6. The imaging lens according to claim 1 , wherein an Abbe number vd 3 of the third lens at a d-line satisfies the following conditional expression:
vd 3<30 (5)
7. The imaging lens according to claim 1 , wherein an Abbe number vd 1 of the first lens at a d-line satisfies the following conditional expression:
vd 1>34 (6)
8. The imaging lens according to claim 1 , wherein the first lens is made of a glass material.
9. The imaging lens according to claim 1 , wherein a surface treatment for giving a water-repellent property is applied to an object-side surface of the first lens.
10. The imaging lens according to claim 1 , wherein at least one lens of the second lens, the third lens, and the fourth lens is made of a resin material.
11. The imaging lens according to claim 10 , wherein a surface treatment for giving a property of reflecting or absorbing UV light is applied to at least one of the lens surfaces that are closer to the object side than the object-side surface of the most-object-side resin lens.
12. An imaging device comprising:
the imaging lens according to claim 1 ; and
an imaging element that outputs imaging signals corresponding to an optical image formed by the imaging lens.
13. The imaging lens according to claim 1 , wherein the thickness of the first lens is equal to or larger than 1.178 mm.
14. An imaging lens comprising, in order from an object side:
a first lens that is a negative lens having a meniscus shape with a convex surface directed to the object side;
a second lens that is a negative lens;
a third lens that is a positive lens having a convex surface directed to the object side;
an aperture stop; and
a fourth lens that is a biconvex lens, wherein
the following conditional expression is satisfied:
1.5< f 4 /fa< 2.7, (1)
where fa denotes a focal length of the whole lens system, and
f 4 denotes a focal length of the fourth lens, wherein the following conditional expression is satisfied:
−3.0<( r 3+ r 4)/( r 3− r 4)<0.2 (3A)
where r 3 denotes a curvature radius of an object-side surface of the second lens, and
r 4 denotes a curvature radius of an image-side surface of the second lens, and
wherein an Abbe number vd 1 of the first lens at a d-line satisfies the following conditional expression:
34< vd 1≦53.2. (6)
15. The imaging lens according to claim 14 , wherein an object-side surface of the second lens includes an aspheric surface that has a concave shape toward the object side in a vicinity of an optical axis and has a convex shape toward the object side in a peripheral portion.
16. The imaging lens according to claim 14 , wherein the aperture stop is positioned to satisfy the following conditional expression:
d 6/( d 7+ d 8)<0.5 (4)
where d 6 denotes a distance, on an optical axis, between the third lens and the aperture stop,
d 7 denotes a distance, on the optical axis, between the aperture stop and the fourth lens, and
d 8 denotes a center thickness of the fourth lens.
17. An imaging device comprising:
the imaging lens according to claim 14 ; and
an imaging element that outputs imaging signals corresponding to an optical image formed by the imaging lens.
18. An imaging device comprising:
the imaging lens according to claim 14 ; and
an imaging element that outputs imaging signals corresponding to an optical image formed by the imaging lens.
19. The imaging lens according to claim 14 , wherein the thickness of the first lens is equal to or larger than 1.178 mm.