Imaging optical lens system, image capturing unit and electronic device
An imaging optical lens system includes, in order from an object side to an image side, a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element. The first lens element has negative refractive power. The second lens element has an object-side surface being concave in a paraxial region thereof and an image-side surface being convex in a paraxial region thereof. The third lens element has positive refractive power. The fourth lens element has positive refractive power. The fifth lens element has negative refractive power. The sixth lens element has positive refractive power. The imaging optical lens system has a total of six lens elements.
1. An imaging optical lens system comprising six lens elements, the six lens elements being, in order from an object side to an image side: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element; each of the six lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;
wherein the first lens element has negative refractive power, the object-side surface of the first lens element is concave in a paraxial region thereof, the image-side surface of the second lens element is convex in a paraxial region thereof, the object-side surface of the fifth lens element is concave in a paraxial region thereof, at least one of the object-side surface and the image-side surface of the sixth lens element has at least one inflection point, and an axial distance between the first lens element and the second lens element is maximum among axial distances between each of all adjacent lens elements of the imaging optical lens system;
wherein a curvature radius of the object-side surface of the sixth lens element is R11, a curvature radius of the image-side surface of the sixth lens element is R12, and the following condition is satisfied:
1.50≤( R 11+ R 12)/( R 11− R 12)<5.5.
2. The imaging optical lens system of claim 1 , wherein the fifth lens element has negative refractive power.
3. The imaging optical lens system of claim 1 , wherein the object-side surface of the fourth lens element is convex in a paraxial region thereof, and the image-side surface of the fifth lens element is convex in a paraxial region thereof.
4. The imaging optical lens system of claim 1 , wherein there is an air gap in a paraxial region between each of all adjacent lens elements of the imaging optical lens system, at least one of the object-side surfaces and the image-side surfaces of the six lens elements of the imaging optical lens system is aspheric, and the object-side surface of the third lens element is convex in a paraxial region thereof.
5. The imaging optical lens system of claim 1 , wherein the third lens element has positive refractive power, the image-side surface of the third lens element is convex in a paraxial region thereof, a focal length of the second lens element is f2, a focal length of the third lens element is f3, and the following condition is satisfied:
−0.50< f 3/ f 2<0.60.
6. The imaging optical lens system of claim 1 , wherein a focal length of the imaging optical lens system is f, the axial distance between the first lens element and the second lens element is T12, and the following condition is satisfied:
0< f/T 12<1.50.
7. The imaging optical lens system of claim 1 , wherein a central thickness of the second lens element is CT2, a curvature radius of the object-side surface of the second lens element is R3, a curvature radius of the image-side surface of the second lens element is R4, and the following condition is satisfied:
−2.5<( CT 2/ R 3)+( CT 2/ R 4)<−0.75.
8. An imaging optical lens system comprising six lens elements, the six lens elements being, in order from an object side to an image side: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element; each of the six lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;
wherein the first lens element has negative refractive power, the object-side surface of the first lens element is concave in a paraxial region thereof, the object-side surface of fifth lens element is concave in a paraxial region thereof, the image-side surface of the fifth lens element is convex in a paraxial region thereof, at least one of the object-side surface and the image-side surface of the sixth lens element has at least one inflection point, an axial distance between the first lens element and the second lens element is maximum among axial distances between each of all adjacent lens elements of the imaging optical lens system, and the axial distance between the first lens element and the second lens element is larger than a central thickness of the second lens element;
wherein a curvature radius of the object-side surface of the sixth lens element is R11, a curvature radius of the image-side surface of the sixth lens element is R12, and the following condition is satisfied:
1.50≤( R 11+ R 12)/( R 11− R 12)<5.5.
9. The imaging optical lens system of claim 8 , wherein the third lens element has positive refractive power, the image-side surface of the third lens element is convex in a paraxial region thereof, and there is an air gap in a paraxial region between each of all adjacent lens elements of the imaging optical lens system.
10. The imaging optical lens system of claim 8 , wherein the image-side surface of the first lens element is concave in a paraxial region thereof, and the object-side surface of the third lens element is convex in a paraxial region thereof.
11. The imaging optical lens system of claim 8 , further comprising an aperture stop disposed between the second lens element and the third lens element.
12. The imaging optical lens system of claim 8 , wherein a focal length of the second lens element is f2, a focal length of the third lens element is f3, and the following condition is satisfied:
−0.50< f 3/ f 2<0.60.
13. The imaging optical lens system of claim 8 , wherein a maximum effective radius of the object-side surface of the first lens element is Y11, a maximum effective radius of the image-side surface of the sixth lens element is Y62, and the following condition is satisfied:
| Y 62/ Y 11|<1.5.
14. The imaging optical lens system of claim 8 , wherein half of a maximum field of view of the imaging optical lens system is HFOV, and the following condition is satisfied:
|1/tan(HFOV)|<0.50.
15. The imaging optical lens system of claim 8 , wherein a curvature radius of the object-side surface of the second lens element and a curvature radius of the image-side surface of the second lens element are both positive or both negative.
16. The imaging optical lens system of claim 8 , wherein an absolute value of a focal length of the second lens element is maximum among absolute values of focal lengths of each of the six lens elements of the imaging optical lens system.
17. An image capturing unit, comprising:
the imaging optical lens system of claim 8 ; and
an image sensor, wherein the image sensor is disposed on an image surface of the imaging optical lens system.
18. An electronic device, comprising:
the image capturing unit of claim 17 .
19. An imaging optical lens system comprising six lens elements, the six lens elements being, in order from an object side to an image side: a first lens element, a second lens element, a third lens element, a fourth lens element, a fifth lens element and a sixth lens element; each of the six lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;
wherein the first lens element has negative refractive power, the object-side surface of the fifth lens element is concave in a paraxial region thereof, the image-side surface of the fifth lens element is convex in a paraxial region thereof, at least one of the object-side surface and the image-side surface of the sixth lens element has at least one inflection point, an axial distance between the first lens element and the second lens element is maximum among axial distances between each of all adjacent lens elements of the imaging optical lens system, an absolute value of a focal length of the second lens element is maximum among absolute values of focal lengths of each of the six lens elements of the imaging optical lens system, the absolute value of the focal length of the fifth lens element is minimum among the absolute values of the focal lengths of each of the six lens elements of the imaging optical lens system, an absolute value of a curvature radius of the object-side surface of the third lens element is larger than an absolute value of a curvature radius of the image-side surface of the third lens element;
wherein a curvature radius of the object-side surface of the sixth lens element is R11, a curvature radius of the image-side surface of the sixth lens element is R12, and the following condition is satisfied:
0<( R 11+ R 12)/( R 11− R 12)<5.5.
20. The imaging optical lens system of claim 19 , wherein the third lens element has positive refractive power, the object-side surface of the third lens element is convex in a paraxial region thereof, and the image-side surface of the third lens element is convex in a paraxial region thereof.
21. The imaging optical lens system of claim 19 , wherein the image-side surface of the second lens element is convex in a paraxial region thereof, and there is an air gap in a paraxial region between each of all adjacent lens elements of the imaging optical lens system.
22. The imaging optical lens system of claim 19 , further comprising an aperture stop disposed between the second lens element and the third lens element.
23. The imaging optical lens system of claim 19 , wherein the curvature radius of the object-side surface of the sixth lens element is R11, the curvature radius of the image-side surface of the sixth lens element is R12, and the following condition is satisfied:
1.32≤( R 11+ R 12)/( R 11− R 12)<5.5.
24. The imaging optical lens system of claim 19 , wherein the focal length of the second lens element is f2, the focal length of the third lens element is f3, and the following condition is satisfied:
−0.50< f 3/ f 2<0.60.
25. The imaging optical lens system of claim 19 , wherein a maximum effective radius of the object-side surface of the first lens element is Y11, a maximum effective radius of the image-side surface of the sixth lens element is Y62, and the following condition is satisfied:
| Y 62/ Y 11|<1.5.
26. The imaging optical lens system of claim 19 , wherein a curvature radius of the object-side surface of the second lens element and a curvature radius of the image-side surface of the second lens element are both positive or both negative.
27. The imaging optical lens system of claim 19 , wherein a curvature radius of the object-side surface of the fourth lens element and a curvature radius of the image-side surface of the fourth lens element are both positive or both negative.
28. The imaging optical lens system of claim 19 , wherein the axial distance between the second lens element and the third lens element is larger than the axial distance between the fourth lens element and the fifth lens element.