Optical system and camera module comprising same

1 . An optical system consisting of:

first and second lens groups sequentially arranged along an optical axis from an object side to a sensor direction, and including at least one lens, respectively,

wherein the first lens group is fixed in the optical system and the second lens group is provided to be movable along the optical axis,

wherein a focal length sign of the first lens group and a focal length sign of the second lens group are opposite to each other,

wherein the optical system satisfies Equation: −1.5<f_2/f_1<0

(f_1 is the focal length of the first lens group, and f_2 is the focal length of the second lens group),

wherein a size of an effective diameter of the lenses included in the first and second lens groups is smaller than a diagonal length of the image sensor,

wherein the first lens group includes a first lens, a second lens, and a third lens sequentially disposed along the optical axis from the object side to the sensor direction,

wherein an object side surface of the first lens has a convex shape,

wherein a center thickness of the first lens is L1_CT,

wherein a center thickness of the second lens is L2_CT, and

wherein the optical system satisfies the following Equation: 1<L1_CT/L2_CT<10.

2 . The optical system of claim 1 , wherein the first lens has a positive (+) refractive power, and

wherein a sensor-side surface of the first lens has a convex shape.

3 . The optical system of claim 1 , wherein the first and second lens groups satisfy Equation 1:

1

<

L_G1

/

L_G2

<

4

[

Equation

⁢

1

]

(In Equation 1, L_G1 means a distance in the optical axis direction from an apex of an object-side surface of a lens closest to the object among lenses included in the first lens group to an apex of the sensor-side surface of the lens closest to the image sensor, and L_G2 means a distance in the optical axis direction from an apex of an object-side surface of a lens closest to the object among lenses included in the second lens group to an apex of a sensor-side surface of a lens closest to the image sensor).

4 . The optical system of claim 1 , wherein the second lens group satisfies the following Equation 2:

4

<

TTL

/

L_G2

<

7

[

Equation

⁢

2

]

(In Equation 2, L_G2 means a distance in the optical axis direction from an apex of an object-side surface of a lens closest to the object among lenses included in the second lens group to an apex of the sensor-side surface of the lens closest to the image sensor, and, TTL (total track length) means a distance in the optical axis direction from the apex of the object-side surface of the lens closest to the object among the plurality of lenses included in the first and second lens groups to an image sensing plane of the image sensor), and

wherein the TTL is constant.

5 . The optical system of claim 1 , wherein the first lens group includes at least one lens having a non-circular shape.

6 . A camera module comprising an optical system and a driving member, the camera module comprising:

an optical system according to claim 1 , and

wherein the driving member controls a position of the second lens group.

7 . The optical system of claim 1 ,

wherein the second lens group includes fourth and fifth lenses sequentially arranged along the optical axis from the object side to the sensor direction, and

wherein the lens surface having the largest effective diameter among lens surfaces of all of the lenses of the first and second lens groups is included in the first lens group, and the lens surface having the smallest effective diameter among lens surfaces of all of the lenses of the first and second lens groups is included in the second lens group.

8 . The optical system of claim 7 , wherein the fifth lens has a negative refractive power, and

wherein a sensor-side surface of the fifth lens has a convex shape.

9 . The optical system of claim 7 , wherein an object-side surface of the fourth lens has a concave shape.

10 . A optical system consisting of:

a first lens group having a first lens, a second lens, and a third lens sequentially disposed along an optical axis from an object side toward an image sensor; and

a second lens group having fourth and fifth lenses sequentially disposed along the optical axis in a direction from the first lens group to the image sensor,

wherein the first lens group is fixed in the optical system and the second lens group is provided to be movable along the optical axis,

wherein a focal length sign of the first lens group and a focal length sign of the second lens group are opposite to each other,

wherein an object side surface of the first lens has a convex shape,

wherein a center thickness of the first lens is L1_CT,

wherein a center thickness of the second lens is L2_CT, and

wherein the optical system satisfies the following Equation: 1<L1_CT/L2_CT<10.

11 . The optical system of claim 10 ,

wherein a center distance between the first lens and the second lens is T12, and

wherein the optical system satisfies the following Equation: 1<T12/L1_CT<2.5.

12 . The optical system of claim 10 ,

wherein the first lens has a positive (+) refractive power,

wherein a focal length of the first lens group is f_1,

wherein a focal length of the second lens group is f_2, and

wherein the optical system satisfies the following Equation: −1.5<f_2/f_1<0.

13 . The optical system of claim 10 ,

wherein a sensor-side surface of the first lens has a convex shape,

wherein an object-side surface of the second lens has a concave shape.

14 . The optical system of claim 10 ,

wherein the fifth lens has negative (−) refractive power, and

wherein a sensor-side surface of the fifth lens has a convex shape.

15 . The optical system of claim 10 ,

wherein an object-side surface of the fourth lens has a concave shape, and

wherein a sensor-side surface of the fourth lens has a smallest effective diameter among lens surfaces of all of the lenses of the first and second lens groups.

16 . The optical system of claim 10 ,

wherein both an object-side surface and a sensor-side surface of the third lens have a convex shape.

17 . The optical system of claim 10 ,

wherein the first lens has a non-circular shape,

wherein the optical system includes a prism disposed on the object-side surface of the first lens.

18 . The optical system of claim 10 ,

wherein a center thickness of the third lens is L3_CT, and

wherein the optical system satisfies the following Equation: 0.1<L2_CT/L3_CT<1.

19 . The optical system of claim 10 ,

wherein a center thickness of the fourth lens is L4_CT,

wherein a center thickness of the fifth lens is L5_CT, and

wherein the optical system satisfies the following Equation: 0.1<L4_CT/L5_CT<1.

20 . The optical system of claim 10 ,

wherein a center thickness of the fifth lens is L5_CT,

wherein a center distance between the fourth lens and the fourth lens is T45, and

wherein the optical system satisfies the following Equation: 2<L5_CT/T45<4.