Photographing optical lens system, image capturing unit and electronic device

1. A photographing optical lens system comprising seven lens elements, the seven 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, a sixth lens element and a seventh lens element; each of the seven lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;

wherein the object-side surface of the first lens element is convex in a paraxial region thereof, the seventh lens element has negative refractive power, and the object-side surface of the seventh lens element is concave in a paraxial region thereof;

wherein at least one of all lens surfaces of the seven lens elements is aspheric and has at least one inflection point, an axial distance between the object-side surface of the first lens element and an image surface is TL, a maximum image height of the photographing optical lens system is ImgH, a focal length of the photographing optical lens system is f, a focal length of the second lens element is f2, an entrance pupil diameter of the photographing optical lens system is EPD, a curvature radius of the image-side surface of the seventh lens element is R14, a sum of central thicknesses of all lens elements of the photographing optical lens system is ΣCT, a central thickness of the seventh lens element is CT7, and the following conditions are satisfied:

TL/ImgH< 1.75;

f/EPD≤ 1.70;

f/R 14≤0;

f/f 2<0.70; and

1.00<Σ CT/CT 7<20.0.

2. The photographing optical lens system of claim 1 , wherein the axial distance between the object-side surface of the first lens element and the image surface is TL, the maximum image height of the photographing optical lens system is ImgH, half of a maximum field of view of the photographing optical lens system is HFOV, and the following conditions are satisfied:

0.50< TL/ImgH< 1.60;

3.0 [mm]< TL< 7.0 [mm]; and

35.0 [deg.]< HFOV< 65.0 [deg.].

3. The photographing optical lens system of claim 1 , wherein the sum of central thicknesses of all lens elements of the photographing optical lens system is ΣCT, the central thickness of the seventh lens element is CT7, and the following condition is satisfied:

1.00<Σ CT/CT 7<15.0.

4. The photographing optical lens system of claim 1 , wherein an axial distance between the sixth lens element and the seventh lens element is largest among all axial distances between all adjacent lens elements of the photographing optical lens system.

5. The photographing optical lens system of claim 1 , wherein the focal length of the photographing optical lens system is f, a focal length of the first lens element is f1, the focal length of the second lens element is f2, a focal length of the seventh lens element is f7, and the following conditions are satisfied:

f 2/ f 1<1.0; and

f/f 7<−0.50.

6. The photographing optical lens system of claim 1 , 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:

0.10<( R 11+ R 12)/( R 11− R 12).

7. The photographing optical lens system of claim 1 , wherein a curvature radius of the object-side surface of the first lens element is R1, a curvature radius of the object-side surface of the seventh lens element is R13, and the following condition is satisfied:

−1.0< R 13/ R 1<0.

8. The photographing optical lens system of claim 1 , wherein the object-side surface of the seventh lens element has at least one convex critical point in an off-axis region thereof.

9. The photographing optical lens system of claim 1 , wherein a number of lens elements having an Abbe number smaller than 20 among the seven lens elements is V20, and the following condition is satisfied:

2≤ V 20.

10. The photographing optical lens system of claim 1 , wherein an absolute value of a curvature radius of the object-side surface of the seventh lens element is a minimum among absolute values of curvature radii of all lens surfaces of the seven lens elements.

11. An image capturing unit, comprising:

the photographing optical lens system of claim 1 ; and

an image sensor disposed on the image surface of the photographing optical lens system.

12. An electronic device, comprising:

the image capturing unit of claim 11 .