Photographing optical lens assembly, image capturing unit and electronic device

1. A photographing optical lens assembly comprising eight lens elements, the eight 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, a seventh lens element and an eighth lens element;

wherein the seventh lens element has an image-side surface being concave in a paraxial region thereof, at least one of an object-side surface and an image-side surface of the eighth lens element has at least one inflection point;

wherein the photographing optical lens assembly further comprises an aperture stop, a focal length of the photographing optical lens assembly is f, an entrance pupil diameter of the photographing optical lens assembly is EPD, a maximum refractive index among the lens elements of the photographing optical lens assembly is Nmax, an axial distance between the aperture stop and an image-side surface of the lens element closest to an image surface is SD, an axial distance between an object-side surface of the lens element closest to an imaged object and the image-side surface of the lens element closest to the image surface is TD, and the following conditions are satisfied:

f/EPD< 2.60;

1.639≤ N max<1.70; and

0.70< SD/TD< 1.10.

2. The photographing optical lens assembly of claim 1 , wherein the image-side surface of the eighth lens element is concave in a paraxial region thereof.

3. The photographing optical lens assembly of claim 1 , wherein the first lens element has positive refractive power, and the second lens element has negative refractive power.

4. The photographing optical lens assembly of claim 1 , wherein the focal length of the photographing optical lens assembly is f, the entrance pupil diameter of the photographing optical lens assembly is EPD, half of a maximal field of view of the photographing optical lens assembly is HFOV, and the following conditions are satisfied:

f/EPD≤ 2.20; and

30.0 degrees<HFOV<50.0 degrees.

5. The photographing optical lens assembly of claim 1 , wherein an axial distance between the object-side surface of the lens element closest to the imaged object and the image surface is TL, the entrance pupil diameter of the photographing optical lens assembly is EPD, and the following condition is satisfied:

1.5< TL/EPD< 4.0.

6. The photographing optical lens assembly of claim 1 , wherein an axial distance between the object-side surface of the lens element closest to the imaged object and the image surface is TL, and the following condition is satisfied:

TL< 12.0 millimeters.

7. The photographing optical lens assembly of claim 1 , wherein an axial distance between the object-side surface of the lens element closest to the imaged object and the image surface is TL, a maximum image height of the photographing optical lens assembly is ImgH, and the following condition is satisfied:

TL /ImgH<2.1.

8. The photographing optical lens assembly of claim 1 , wherein the focal length of the photographing optical lens assembly is f, a focal length of the eighth lens element is f8, and the following condition is satisfied:

−2.8< f/f 8<1.0.

9. The photographing optical lens assembly of claim 1 , wherein at least one of an object-side surface and the image-side surface of the seventh lens element has at least one critical point.

10. The photographing optical lens assembly of claim 1 , wherein the image-side surface of the eighth lens element has at least one critical point, and there is an air gap in a paraxial region between every two of the eight lens elements that are adjacent to each other.

11. An image capturing unit, comprising:

the photographing optical lens assembly of claim 1 ; and

an image sensor, wherein the image sensor is disposed on the image side of the photographing optical lens assembly.

12. A photographing optical lens assembly comprising eight lens elements, the eight 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, a seventh lens element and an eighth lens element;

wherein the seventh lens element has an image-side surface being concave in a paraxial region thereof, the eighth lens element has negative refractive power, at least one of an object-side surface and an image-side surface of the eighth lens element is aspheric; at least one of the object-side surface and the image-side surface of the eighth lens element has at least one inflection point;

wherein a focal length of the photographing optical lens assembly is f, an entrance pupil diameter of the photographing optical lens assembly is EPD, a maximum refractive index among the lens elements of the photographing optical lens assembly is Nmax, a curvature radius of the object-side surface of the eighth lens element is R15, a curvature radius of the image-side surface of the eighth lens element is R16, and the following conditions are satisfied:

f/EPD< 2.60;

1.639≤ N max<1.70; and

−0.9<( R 15− R 16)/( R 15+ R 16)<10.

13. The photographing optical lens assembly of claim 12 , wherein the object-side surface of the eighth lens element is convex in a paraxial region thereof.

14. The photographing optical lens assembly of claim 12 , wherein the focal length of the photographing optical lens assembly is f, the entrance pupil diameter of the photographing optical lens assembly is EPD, and the following condition is satisfied:

f/EPD≤ 2.20.

15. The photographing optical lens assembly of claim 12 , wherein the curvature radius of the object-side surface of the eighth lens element is R15, the curvature radius of the image-side surface of the eighth lens element is R16, and the following condition is satisfied:

0.03≤( R 15− R 16)/( R 15+ R 16)≤1.21.

16. The photographing optical lens assembly of claim 12 , wherein a maximum effective radius of an object-side surface of the first lens element is Y11, a maximum effective radius of the image-side surface of the eighth lens element is Y82, and the following condition is satisfied:

0.20< Y 11/ Y 82<0.70.

17. The photographing optical lens assembly of claim 12 , wherein a maximum axial distance among all axial distances between every two lens elements of the photographing optical lens assembly that are adjacent to each other is ATmax, a maximum image height of the photographing optical lens assembly is ImgH, and the following condition is satisfied:

AT max/ImgH<0.30.

18. The photographing optical lens assembly of claim 12 , wherein the focal length of the photographing optical lens assembly is f, a focal length of the first lens element is f1, a focal length of the second lens element is f2, the curvature radius of the image-side surface of the eighth lens element is R16, and the following conditions are satisfied:

−1.0< f 1/ f 2<0.7; and

0.3< f/R 16≤3.16.

19. The photographing optical lens assembly of claim 12 , wherein a central thickness of the seventh lens element is CT7, a central thickness of the eighth lens element is CT8, and the following condition is satisfied:

0.71≤ CT 7/ CT 8≤1.23.

20. The photographing optical lens assembly of claim 12 , wherein the maximum refractive index among the lens elements of the photographing optical lens assembly is Nmax, and the following condition is satisfied:

1.660≤ N max<1.70.

21. The photographing optical lens assembly of claim 12 , wherein each of the eight lens elements is made of plastic material, at least one of an object-side surface and the image-side surface of the seventh lens element has at least one critical point.

22. A photographing optical lens assembly comprising eight lens elements, the eight 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, a seventh lens element and an eighth lens element;

wherein the eighth lens element has an image-side surface being concave in a paraxial region thereof, at least one of an object-side surface and the image-side surface of the eighth lens element is aspheric, the image-side surface of the eighth lens element has at least one critical point, and the image-side surface of the eighth lens element has at least one inflection point;

wherein a focal length of the photographing optical lens assembly is f, an entrance pupil diameter of the photographing optical lens assembly is EPD, an axial distance between an object-side surface of the lens element closest to an imaged object and an image surface is TL, a maximum image height of the photographing optical lens assembly is ImgH, a vertical distance between the at least one critical point and an optical axis is Yc82, and the following conditions are satisfied:

f/EPD≤ 2.20;

TL /ImgH<2.1; and

0.10< Yc 82/ f< 0.80.

23. The photographing optical lens assembly of claim 22 , wherein an axial distance between an image-side surface of the lens element closest to the image surface and the image surface is BL, the entrance pupil diameter of the photographing optical lens assembly is EPD, and the following condition is satisfied:

0.10< BL/EPD< 0.70.

24. The photographing optical lens assembly of claim 22 , wherein a sum of every axial distance between every two lens elements of the photographing optical lens assembly that are adjacent to each other is ΣAT, an axial distance between an image-side surface of the lens element closest to the image surface and the image surface is BL, a sum of central thicknesses of the lens elements of the photographing optical lens assembly is ΣCT, and the following condition is satisfied:

(Σ AT+BL )/Σ CT< 0.80.

25. The photographing optical lens assembly of claim 22 , wherein a curvature radius of an object-side surface of the sixth lens element is R11, a curvature radius of an image-side surface of the sixth lens element is R12, and the following condition is satisfied:

−1.88≤( R 11− R 12)/( R 11+ R 12)≤0.27.

26. The photographing optical lens assembly of claim 22 , wherein a curvature radius of the object-side surface of the eighth lens element is R15, a curvature radius of the image-side surface of the eighth lens element is R16, and the following condition is satisfied:

0.03≤( R 15− R 16)/( R 15+ R 16)≤1.70.

27. The photographing optical lens assembly of claim 22 , wherein the focal length of the photographing optical lens assembly is f, a focal length of the first lens element is f1, and the following condition is satisfied:

0< f/f 1<1.5.

28. The photographing optical lens assembly of claim 22 , wherein at least one of an object-side surface and an image-side surface of the seventh lens element has at least one critical point, a vertical distance between the at least one critical point and the optical axis is Yc7, the focal length of the photographing optical lens assembly is f, and the following condition is satisfied:

0.10< Yc 7/ f< 0.60.