Subminiature optical system and portable device including the same
There are provided a subminiature optical system having a miniature size and capable of obtaining a narrow view angle using only five sheets of lenses, and a portable device having the same. The subminiature optical system includes a first lens convex toward the object side and having positive refractive power. a second lens concave toward an image side and having negative refractive power, a third lens convex toward the object side and having positive refractive power, a fourth lens concave toward the image plane and having negative refractive power, and a fifth lens convex toward the image plane and having negative or positive refractive power, sequentially from an object side.
1. An optical system, comprising:
a first optical system; and
a second optical system having a view angle narrower than that of the first optical system,
the second optical system comprising:
a first lens;
a second lens;
a third lens;
a fourth lens having a biconcave shape;
a fifth lens; and
an image sensor,
wherein the first lens to image sensor are sequentially disposed from an object side,
wherein when a distance from an object-side surface of the first lens to an imaging surface of the image sensor is TTL and an overall focal length of the second optical system is f, 0.7<TTL/f<1.0 is satisfied,
wherein an object-side surface of the fifth lens is concave, and
wherein an object-side surface of the third lens is convex.
2. The optical system of claim 1 , wherein the second optical system has the view angle of 20 degrees through 35 degrees.
3. The optical system of claim 1 , wherein the first optical system has the view angle of 60 degrees through 80 degrees.
4. The optical system of claim 1 , wherein when a radius of curvature of the object-side surface of the first lens is rdy s1, 0.16<rdy s1/f<2 is satisfied.
5. The optical system of claim 1 , wherein the first to fifth lenses are formed of plastic.
6. The optical system of claim 1 , wherein the fifth lens has an inflection point formed on at least one of an object-side surface and an image-side surface of the fifth lens.
7. The optical system of claim 1 , wherein the object-side surface of the first lens is convex.
8. The optical system of claim 1 , wherein the image-side surface of the first lens is concave.
9. The optical system of claim 1 , wherein the first lens has positive refractive power.
10. The optical system of claim 1 , wherein an object-side surface of the second lens is concave.
11. The optical system of claim 1 , wherein an image-side surface of the second lens is concave.
12. The optical system of claim 1 , wherein the second lens has negative refractive power.
13. The optical system of claim 1 , wherein the third lens has positive refractive power.
14. The optical system of claim 1 , wherein surfaces of the first lens, the second lens, the third lens, the fourth lens, and the fifth lens are formed as aspherical surfaces.
15. The optical system of claim 1 , wherein an image-side surface of the third lens is concave.
16. The optical system of claim 1 , wherein the fourth lens has negative refractive power.
17. The optical system of claim 1 , wherein an image-side surface of the fifth lens is convex.
18. The optical system of claim 1 , wherein the fifth lens has positive refractive power.
19. The optical system of claim 1 , wherein the view angle difference between the first optical system and the second optical system is greater than 25 degrees and less than 80 degrees.