Wide-angle imaging lens, imaging device and camera module

1. A wide-angle imaging lens comprising, in order from an object side:

a first lens group having a positive refractive power;

an aperture stop; and

a second lens group having a positive refractive power, wherein:

the first lens group comprises, in order from the object side,

a first lens that is a negative meniscus lens having a convex surface directed to the object side,

a negative second lens whose surface on an image side has a concave shape, and

a positive third lens whose surface on the image side has a convex shape directed to the image side, and

the second lens group comprises

a positive fourth lens whose surface on the image side has a convex shape directed to the image side,

a negative fifth lens having a biconcave shape, and

a positive sixth lens, and

the following Conditional Expressions (1) to (5) are satisfied:

−4.0< f 2/ f<− 2.0  (1)

3.5< f 3/ f< 6.0  (2)

−2.5< f 5/ f<− 1.5  (3)

3.0< fb/f< 5.0  (4)

−3.0< f 12/ f<− 1.2  (5)

where f denotes a focal length of the wide-angle imaging lens,

f 2 denotes a focal length of the second lens,

f 3 denotes a focal length of the third lens,

f 5 denotes a focal length of the fifth lens,

fb denotes a composite focal length of the second lens group, and

f 12 denotes a composite focal length of the first lens and the second lens.

2. The wide-angle imaging lens according to claim 1 , wherein:

Abbe numbers of materials of the first lens and the sixth lens are equal to or larger than 40,

Abbe numbers of material of the second lens and the fourth lens are equal to or larger than 50,

Abbe number of a material of the third lens is equal to or less than 40, and

Abbe number of a material of the fifth lens is equal to or less than 30.

3. The wide-angle imaging lens according to claim 2 , wherein the fifth lens and the sixth lens are cemented together.

4. The wide-angle imaging lens according to claim 3 , wherein:

an angle of view is 180° or more, and

the following Conditional Expression (6) is satisfied:

Y 80/ Y 40>2.1  (6)

where Y 80 denotes an image height at an angle of view which is equal to 80% of a maximum angle of view, and Y 40 denotes an image height at an angle of view which is equal to 40% of the maximum angle of view.

5. The wide-angle imaging lens according to claim 1 , wherein the fifth lens and the sixth lens are cemented together.

6. The wide-angle imaging lens according to claim 5 , wherein:

an angle of view is 180° or more, and

the following Conditional Expression (6) is satisfied:

Y 80/ Y 40>2.1  (6)

where Y 80 denotes an image height at an angle of view which is equal to 80% of a maximum angle of view, and Y 40 denotes an image height at an angle of view which is equal to 40% of the maximum angle of view.

7. The wide-angle imaging lens according to claim 1 , wherein:

an angle of view is 180° or more, and

the following Conditional Expression (6) is satisfied:

Y 80/ Y 40>2.1  (6)

where Y 80 denotes an image height at an angle of view which is equal to 80% of a maximum angle of view, and Y 40 denotes an image height at an angle of view which is equal to 40% of the maximum angle of view.

8. A camera module fitted into a camera main body, the camera module comprising:

the wide-angle imaging lens according to claim 1 ;

an imaging element that outputs an electric signal in response to an optical image formed by the wide-angle imaging lens; and

an external connection terminal that connects the imaging element to a circuit of a camera main body, wherein:

the wide-angle imaging lens, the imaging element, and the external connection terminal are integrated together.

9. An imaging device comprising:

the wide-angle imaging lens according to claim 1 ; and

an imaging element, wherein

the imaging element outputs an electric signal in response to an optical image formed by the wide-angle imaging lens.