Autofocusing optical system of camera module
An autofocusing optical system of a camera module which can be installed in a subminiature camera module. In the optical system, a first lens group has an overall positive refractive power. A second lens group has an overall negative refractive power. The second lens group includes a liquid lens having a meniscus formed between non-miscible first and second liquids, the first liquid having conductivity and polarity, the meniscus having a curvature radius changing in response to a voltage applied to serve as a refractive surface, thereby autofocusing the optical system, a first cover lens for sealing the liquid lens at an object side and a second cover lens for sealing the liquid lens at an image side. A third lens group has an overall positive refractive power. Also, a fourth lens group has an overall negative refractive power.
1. An autofocusing optical system of a camera module comprising:
a first lens group having an overall positive refractive power;
a second lens group having an overall negative refractive power, the second lens group including a liquid lens having a meniscus formed between non-miscible first and second liquids, the first liquid having conductivity and polarity, the meniscus having a curvature radius changing in response to a voltage applied to serve as a refractive surface, thereby autofocusing the optical system, a first cover lens for sealing the liquid lens at an object side and a second cover lens for sealing the liquid lens at an image side;
a third lens group having an overall positive refractive power; and
a fourth lens group having an overall negative refractive power.
2. The optical system according to claim 1 , wherein the first cover lens has a curvature radius at the object side and the liquid lens has a curvature radius at the meniscus, respectively, according to following relations 1 and 2 :
R 4× Rf 6<0 relation 1, and
R 4× Rn 6>0 relation 2,
where R 4 is a curvature radius of the first cover lens at the object side, Rf 6 is a curvature radius of the meniscus at a long distance focus, and Rn 6 is a curvature radius of the meniscus at a short distance focus.
3. The optical system according to claim 2 , wherein the second lens group has a refractive power according to following relation 3:
|F′2|/ F 21<1.2 relation 3,
where F′2 is a total focal length of the second lens group at a short distance focus, and F 2 is a total focal length of the second lens group at a long distance focus.
4. The optical system according to claim 1 , wherein the first lens group has a refractive power according to following relation 4:
0.4 <F 1/ F< 0.7 relation 4,
where F 1 is a total focal length of the first lens group, and F is a focal length of an entire optical system at a long distance focus.
5. The optical system according to claim 1 , wherein the third and fourth lens groups have a refractive power according to following relation 5:
−1.2 <F 3/ F 4<−0.7 relation 5,
where F 3 is a total focal length of the third lens group and F 4 is a total focal length of the fourth lens group.
6. The optical system according to claim 1 , wherein the second and third lens groups have a refractive power according to following relation 6:
−1.0< F 2/ F 3<−0.8 relation 6,
where F 2 is a total focal length of the second lens group at a long distance focus, and F 3 is a total focal length of the third lens group.
7. The optical system according to claim 1 , comprising an aperture stop disposed in front of the liquid lens to remove unnecessary light.
8. The optical system according to claim 1 , wherein at least one of refractive surfaces of the first and second cover lenses is spherical or aspherical.
9. The optical system according to claim 2 , wherein the first lens group has a refractive power according to following relation 4:
0.4< F 1/ F< 0.7 relation 4,
where F 1 is a total focal length of the first lens group, and F is a focal length of an entire optical system at a long distance focus.
10. The optical system according to claim 2 , wherein the third and fourth lens groups have a refractive power according to following relation 5:
−1.2 <F 3/ F 4<−0.7 relation 5,
where F 3 is a total focal length of the third lens group and F 4 is a total focal length of the fourth lens group.
11. The optical system according to claim 2 , wherein the second and third lens groups have a refractive power according to following relation 6:
−1.0< F 2/ F 3<−0.8 relation 6,
where F 2 is a total focal length of the second lens group at a long distance focus, and F 3 is a total focal length of the third lens group.
12. The optical system according to claim 3 , wherein the first lens group has a refractive power according to following relation 4:
0.4 <F 1/ F< 0.7 relation 4,
where F 1 is a total focal length of the first lens group, and F is a focal length of an entire optical system at a long distance focus.
13. The optical system according to claim 3 , wherein the third and fourth lens groups have a refractive power according to following relation 5:
−1.2 <F 3/ F 4<−0.7 relation 5,
where F 3 is a total focal length of the third lens group and F 4 is a total focal length of the fourth lens group.
14. The optical system according to claim 3 , wherein the second and third lens groups have a refractive power according to following relation 6:
−1.0 <F 2/ F 3<−0.8 relation 6,
where F 2 is a total focal length of the second lens group at a long distance focus, and F 3 is a total focal length of the third lens group.