Ultra wide-angle imaging lens device and imaging apparatus
View Patent ↗An ultra wide-angle imaging lens device 1 includes, in order from an object side: a negative first lens L 1 having a meniscus shape with a convex surface directed to the object side; a negative second lens L 2 having a concave surface directed to an image side and having at least one aspheric surface; a positive third lens L 3 having a convex surface directed to the object side and having at least one aspheric surface; a stop; and a positive fourth lens L 4 having a convex surface directed to the image side and having at least one aspheric surface. The following conditional expression (1) is satisfied: −3.2< L/f 34 <3.2 (1) where L denotes a distance on an optical axis from an object side surface of the first lens to an image formation surface, and f 34 denotes a composite focal length of the third and fourth lenses L 3 and L 4.
1. An ultra wide-angle imaging lens device comprising, in order from an object side:
a negative first lens having a meniscus shape with a convex surface directed to the object side;
a negative second lens having a concave surface directed to an image side and having at least one aspheric surface;
a positive third lens having a convex surface directed to the object side and having at least one aspheric surface;
a stop; and
a positive fourth lens having a convex surface directed to the image side and having at least one aspheric surface, wherein
the following conditional expression (1) is satisfied:
−3.2 <L/f 34 <3.2 (1)
where L denotes a distance on an optical axis from an object side surface of the first lens to an image formation surface, and
f 34 denotes a composite focal length of the third and fourth lenses.
2. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expression (2) is satisfied:
0.18 <d 2 /L< 0.30 (2)
where d 2 denotes an on-axis space between the first lens and the second lens.
3. The ultra wide-angle imaging lens device according to claim 2 , wherein the following conditional expression (3) is satisfied:
d 4 /L< 0.10 (3)
where d 4 denotes an on-axis space between the second lens and the third lens.
4. The ultra wide-angle imaging lens device according to claim 3 , wherein the following conditional expression (5) is satisfied:
0.17 <d 5 /L< 0.30 (5)
where d 5 denotes a thickness of the third lens on the optical axis.
5. The ultra wide-angle imaging lens device according to claim 4 , wherein the following conditional expression (6) is satisfied:
−0.22 <f 2 /L<− 0.08 (6)
where f 2 denotes a focal length of the second lens.
6. The ultra wide-angle imaging lens device according to claim 5 , wherein the following conditional expression (7) is satisfied:
0.10 <f 3 /L< 0.25 (7)
where f 3 denotes a focal length of the third lens.
7. The ultra wide-angle imaging lens device according to claim 6 , wherein the following conditional expression (8) is satisfied.
0.10 <f 4 /L< 0.20 (8)
where f 4 denotes a focal length of the fourth lens.
8. The ultra wide-angle imaging lens device according to claim 7 , wherein the following conditional expression (13) is satisfied:
da/L< 0.02 (13),
where da denotes an on-axis space between the stop and the fourth lens.
9. The ultra wide-angle imaging lens device according to claim 8 , wherein an angle of view of the ultra wide-angle imaging lens device is greater than 180 degrees.
10. An imaging apparatus comprising:
the ultra wide-angle imaging lens device according to claim 9 ; and
an imaging device that converts an optical image formed by the ultra wide-angle imaging lens device into an electric signal.
11. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expression (3) is satisfied:
d 4 /L< 0.10 (3)
where d 4 denotes an on-axis space between the second lens and the third lens.
12. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expression (4) is satisfied:
N 1 >1.7 (4)
where N 1 denotes a refractive index of the first lens at the e-line.
13. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expression (5) is satisfied:
0.17 <d 5 /L< 0.30 (5)
where d 5 denotes a thickness of the third lens on the optical axis.
14. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expression (6) is satisfied:
−0.22 <f 2 /L<− 0.08 (6)
where f 2 denotes a focal length of the second lens.
15. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expression (7) is satisfied:
0.10 <f 3 /L< 0.25 (7)
where f 3 denotes a focal length of the third lens.
16. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expression (8) is satisfied:
0.10 <f 4 /L< 0.20 (8)
where f 4 denotes a focal length of the fourth lens.
17. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expressions (9) to (12) are satisfied:
ν 1 ≧40 (9)
ν 2 ≧50 (10)
ν 3 ≦40 (11)
ν 4 ≧50 (12)
where
ν 1 denotes an Abbe number of the first lens at the d-line,
ν 2 denotes an Abbe number of the second lens at the d-line,
ν 3 denotes an Abbe number of the third lens at the d-line, and
ν 4 denotes an Abbe number of the fourth lens at the d-line.
18. The ultra wide-angle imaging lens device according to claim 1 , wherein the following conditional expression (13) is satisfied:
da/L< 0.02 (13),
where da denotes an on-axis space between the stop and the fourth lens.
19. The ultra wide-angle imaging lens device according to claim 1 , wherein an angle of view of the ultra wide-angle imaging lens device is greater than 180 degrees.
20. An imaging apparatus comprising:
the ultra wide-angle imaging lens device according to claim 1 ; and
an imaging device that converts an optical image formed by the ultra wide-angle imaging lens device into an electric signal.