Optical unit and imaging apparatus
An optical unit and an imaging apparatus including the optical unit. The optical unit includes a first lens group, a second lens group, and a third lens group, which are arranged in order from an object side to an image plane side. Further, the first lens group includes a first lens element, a first transparent body, and a second lens element, which are arranged in order from the object side to the image plane side.
1. An optical unit comprising, arranged in order from an object side to an image plane side:
a first lens group,
a second lens group; and
a third lens group,
wherein,
the first lens group includes, arranged in order from the object side to the image plane side, (a) a first lens element, (b) a first transparent body, and (c) a second lens element, and
a focal length fg 1 of the first lens group, a focal length fg 2 of the second lens group, and a focal length fg 3 of the third lens group satisfy the following conditional expressions:
0.5≦ fg 1/ f≦ 1.5,
0.5≦ fg 2/ f≦ 50, and
−5≦ fg 3/ f≦− 0.3,
where f is a total focal length.
2. The optical unit according to claim 1 , wherein a bending factor qL 2 of the second lens group satisfies the following conditional expressions:
−10≦ qL 2≦−0.4, and
qL 2=( RL 2 S 2+ RL 2 S 1)/( RL 2 S 2− RL 2 S 1),
where
RL 2 S 1 is a radius of curvature of an input side surface S 1 of the second lens group, and
RL 2 S 2 is a radius of curvature of an outgoing side surface S 2 of the second lens group.
3. The optical unit according to claim 1 , wherein a paraxial quantity of the third lens group satisfies the following conditional expression and the surface shape includes a concave shape:
−3≦ RL 3 S 1/ f≦− 0.2,
where
RL 3 S 1 is a radius of curvature of an incidence side surface S 1 of the third lens group, and
f is a focal length of the lens system.
4. The optical unit according to claim 1 , wherein at least the third lens group is formed by being molded individually or in a wafer form and being subsequently diced to be assembled.
5. The optical unit according to 1 , wherein each of the second and third lens groups includes only a single lens element.
6. The optical unit according to claim 1 , wherein an angle of view satisfies the following conditional expression:
20≦ω≦40
where ω is a half angle of view.
7. The optical unit according to 1 , wherein an Abbe number νE1 of the first lens element and an Abbe number νE2 of the second lens element satisfy the following conditional expressions:
45≦ νE 1≦90, and
20≦ νE 2≦60,
where
νE1 is the Abbe number of the first lens element, and
νE2 is the Abbe number of the second lens element.
8. The optical unit according to claim 1 , wherein an F-number of the lens system satisfies the following conditional expression:
1.0≦ Fno≦ 3.0.
9. The optical unit according to claim 1 , wherein an optical length TT of the lens system satisfies the following conditional expression:
0.8≦ TT/f≦ 1.5
where f is the total focal length.
10. The optical unit according to claim 1 , wherein a back focus BF of the lens system satisfies the following conditional expression:
0.01 ≦BF≦ 0.6.
11. An optical unit comprising, arranged in order from an object side to an image plane side:
a first lens group;
a second lens group; and
a third lens group,
wherein
the first lens group includes, arranged in order from the object side to the image plane side, (a) a first lens element, (b) a first transparent body, and (c) a second lens element, the first lens element and the second lens element forming a doublet lens.
12. The optical unit according to claim 11 , wherein the first lens element has a biconvex shape and the second lens element has a plano-concave shape, the first and second lens elements forming the doublet lens.
13. The optical unit according to claim 12 , wherein an Abbe number of the first lens element is larger than an Abbe number of the second lens element.
14. An imaging apparatus comprising:
an imaging element; and
an optical unit for forming an image of a subject in the imaging element,
wherein,
(1) the optical unit includes, arranged in order from an object side to an image plane side, (a) a first lens group, (b) a second lens group, and (c) a third lens group, and
(2) the first lens group includes, arranged in order from an object side to an image plane side, (a) a first lens element, (b) a first transparent body, and a (c) second lens element, and
(3) a focal length fg 1 of the first lens group, a focal length fg 2 of the second lens group, and a focal length fg 3 of the third lens group satisfy the following conditional expressions:
0.5≦ fg 1/ f≦ 1.5,
0.5≦ fg 2/ f≦ 50, and
−5≦ fg 3/ f≦− 0.3,
where f is a total focal length.
15. An imaging apparatus comprising:
an imaging element; and
an optical unit for forming an image of a subject in the imaging element,
wherein,
(1) the optical unit includes, arranged in order from an object side to an image plane side, (a) a first lens group, (b) a second lens group, and (c) a third lens group, and
(2) the first lens group includes, arranged in order from an object side to an image plane side, (a) a first lens element, (b) a first transparent body, and a (c) second lens element, the first lens element and the second lens element forming a doublet lens.