Imagery optical system
An imagery optical system, sequentially from an object side to an image side on an optical axis comprising: the first lens element with positive refractive power, the second lens element with positive refractive power, the third lens element, the fourth lens element, and the fifth lens element having at least one inflection point. Each of the five lens elements may be made of plastic and comes with bi-aspheric surfaces. The imagery optical system satisfies conditions related to shorten the total length and to reduce the sensitivity for use in compact cameras and mobile phones with a camera function.
1. An imagery optical system, sequentially arranged from an object side to an image side, comprising:
a first lens element with positive refractive power;
a second lens element with positive refractive power;
a third lens element;
a fourth lens element having a concave object-side surface and a convex image-side surface, and at least one of the object-side and image-side surfaces being aspheric;
a fifth lens element made of plastic, and having at least one of object-side and image-side surfaces being aspheric, and at least one of the object-side and image-side surfaces having at least one inflection point;
wherein, an axial distance between the third lens element and the fourth lens element is T 34 , an axial distance between the fourth lens element and the fifth lens element is T 45 , a curvature radius of the image-side surface of the second lens element is R 4 , a curvature radius of the object-side surface of the third lens element is R 5 , an Abbe number of the first lens element is v 1 , an Abbe number of the third lens element is v 3 , and the following relations are satisfied:
0.1 <T 45 /T 34 <2.0;
−3.0 <R 4 /R 5 <0.7; and
28.0 <v 1 −v 3 .
2. The imagery optical system of claim 1 , wherein the object-side surface of the first lens element is convex, and the image-side surface of the second lens element is convex.
3. The imagery optical system of claim 2 , wherein the image-side surface of the fifth lens element is concave.
4. The imagery optical system of claim 3 , further comprising a stop and an image plane, wherein an axial distance from the object-side surface of the first lens element to the image plane is TTL, an axial distance from the stop to the image plane is SL, and the following relation is satisfied:
0.7 <SL/TTL <1.2.
5. The imagery optical system of claim 4 , wherein the axial distance between the third lens element and the fourth lens element is T 34 , a thickness of the fourth lens element near the optical axis is CT 4 , and the following relation is satisfied:
0.3 <T 34 /CT 4 <2.0.
6. The imagery optical system of claim 5 , wherein a focal length of the imagery optical system is f, a focal length of the first lens element is f 1 , a focal length of the second lens element is f 2 , and the following relation is satisfied:
1.0<( f/f 1 )+( f/f 2 )<2.2.
7. The imagery optical system of claim 5 , wherein a focal length of the fifth lens element is f 5 , a focal length of the fourth lens element is f 4 , and the following relation is satisfied:
0.7 <|f 5 /f 4 |<2.0.
8. The imagery optical system of claim 7 , wherein the axial distance between the third lens element and the fourth lens element is T 34 , the axial distance between the fourth lens element and the fifth lens element is T 45 , and preferably the following relation is satisfied:
0.3 <T 45 /T 34 <1.3.
9. The imagery optical system of claim 4 , wherein a focal length of the imagery optical system is f, a focal length of the third lens element is f 3 and the following relation is satisfied:
−1.2 <f/f 3 <−0.4.
10. The imagery optical system of claim 9 , wherein the curvature radius of the image-side surface of the second lens element is R 4 , the curvature radius of the object-side surface of the third lens element is R 5 , and preferably the following relation is satisfied:
−1.5 <R 4 /R 5 <0.2.
11. The imagery optical system of claim 9 , wherein an axial distance from the object-side surface of the first lens element to the image-side surface of the third lens element is D R1R6 , an axial distance from the object-side surface of the first lens element to the image-side surface of the fifth lens element is T d , and the following relation is satisfied:
0.20 <D R1R6 /T d <0.45.
12. The imagery optical system of claim 9 , wherein the fourth lens element has positive refractive power, the fifth lens element has negative refractive power, and the image-side surface of the third lens element is concave.
13. The imagery optical system of claim 12 , wherein a curvature radius of the object-side surface of the fourth lens element is R 7 , a curvature radius of the image-side surface of the fourth lens element is R 8 , and the following relation is satisfied:
1.30<( R 7 +R 8 )/( R 7 −R 8 ).
14. The imagery optical system of claim 1 , further comprising an image sensor at an image plane, wherein an axial distance from the object-side surface of the first lens element to the image plane is TTL, and ImgH is half of the diagonal length of an effective photosensitive area of the image sensor; and the following relation is satisfied:
TTL/ImgH <2.1.
15. An imagery optical system, sequentially arranged from an object side to an image side, comprising:
a first lens element with positive refractive power, having a convex object-side surface;
a second lens element with positive refractive power, having a convex image-side surface;
a third lens element with negative refractive power;
a fourth lens element having a concave object-side surface and a convex image-side surface, and at least one of the object-side and image-side surfaces being aspheric;
a fifth lens element made of plastic having a concave object-side surface and a concave image-side surface, and at least one of the object-side and image-side surfaces being aspheric, and at least one of the object-side and image-side surfaces of the fifth lens element having at least one inflection point;
wherein an axial distance between the third lens element and the fourth lens element is T 34 , an axial distance between the fourth lens element and the fifth lens element is T 45 , a curvature radius of the image-side surface of the second lens element is R 4 , a curvature radius of the object-side surface of the third lens element is R 5 , and the following relations are satisfied:
0.1 <T 45 /T 34 <2.0; and
−3.0 <R 4 /R 5 <0.7
wherein a focal length of the fifth lens element is f 5 , a focal length of the fourth lens element is f 4 , and the following relation is satisfied:
0.7 <|f 5/ f 4|<2.0.
16. The imagery optical system of claim 15 , wherein the axial distance between the third lens element and the fourth lens element is T 34 , the axial distance between the fourth lens element and the fifth lens element is T 45 , and preferably the following relation is satisfied:
0.3 <T 45 /T 34 <1.3.
17. The imagery optical system of claim 16 , wherein an Abbe number of the first lens element is v 1 , an Abbe number of the third lens element is v 3 , and the following relation is satisfied:
28.0 <v 1 −v 3 .
18. The imagery optical system of claim 16 , wherein a focal length of the imagery optical system is f, a focal length of the first lens element is f 1 , a focal length of the second lens element is f 2 , and the relation is satisfied:
1.0<( f/f 1 )+( f/f 2 )<2.2.
19. The imagery optical system of claim 16 , wherein a focal length of the imagery optical system is f, a focal length of the first lens element is f 1 , a focal length of the second lens element is f 2 , and the relation is satisfied:
1.2<( f/f 1 )+( f/f 2 )<1.7.
20. The imagery optical system of claim 16 , wherein the image-side surface of the third lens element is concave, and at least one of the object-side and image-side surfaces of the third lens element has at least one inflection point.
21. The imagery optical system of claim 15 , wherein a curvature radius of the object-side surface of the fourth lens element is R 7 , a curvature radius of the image-side surface of the fourth lens element is R 8 , and the following relation is satisfied:
1.30<( R 7 +R 8 )/( R 7 −R 8 ).
22. The imagery optical system of claim 15 , wherein the curvature radius of the image-side surface of the second lens element is R 4 , the curvature radius of the object-side surface of the third lens element is R 5 , and preferably the following relation is satisfied:
−1.5 <R 4 /R 5 <0.2.
23. An imagery optical system, sequentially from an object side to an image side, comprising:
a first lens element with positive refractive power, having a convex object-side surface;
a second lens element with positive refractive power;
a third lens element with negative refractive power;
a fourth lens element with positive refractive power, having a concave object-side surface and a convex image-side surface, and at least one of the object-side and image-side surfaces being aspheric; and
a fifth lens element with negative refractive power, made of plastic, having a concave image-side surface, and at least one of the object-side and image-side surfaces having at least one inflection point;
wherein an axial distance between the third lens element and the fourth lens element is T 34 , an axial distance between the fourth lens element and the fifth lens element is T 45 , an Abbe number of the first lens element is v 1 , an Abbe number of the third lens element is v 3 , and the following relations are satisfied:
0.1 <T 45 /T 34 <2.0; and
28.0 <v 1 −v 3
wherein a focal length of the imagery optical system is f, a focal length of the first lens element is f 1 a focal length of the second lens element is f 2 and the following relation is satisfied:
1.0<( f/f 1 )+( f/f 2 )<2.2.
24. The imagery optical system of claim 23 , wherein an axial distance from the object-side surface of the first lens element to the image-side surface of the third lens element is D R1R6 , an axial distance from the object-side surface of the first lens element to the image-side surface of the fifth lens element is T d , and the relation is satisfied:
0.20 <D R1R6 /T d <0.45.
25. The imagery optical system of claim 23 , further comprising a stop and an image plane, wherein the object-side surface of the fifth lens element is concave, and an axial distance from the object-side surface of the first lens element to the image plane is TTL, an axial distance from the stop to the image plane is SL, and the following relation is satisfied:
0.7 <SL/TTL< 1.2.
26. The imagery optical system of claim 23 , wherein a focal length of the fifth lens element is f 5 , a focal length of the fourth lens element is f 4 , and the following relation is satisfied:
0.7 <|f 5 /f 4 |<2.0.