Image capturing optical assembly, imaging apparatus and electronic device

1. An image capturing optical assembly comprising, in order from an object side to an image side:

a first lens group, a second lens group and a third lens group;

wherein the first lens group comprises, in order from the object side to the image side, a first lens element and a second lens element; the second lens group comprises, in order from the object side to the image side, a third lens element, a fourth lens element and a fifth lens element; and the third lens group comprises, in order from the object side to the image side, a sixth lens element, a seventh lens element and an eighth lens element;

wherein each of the first lens element, the second lens element, the third lens element, the fourth lens element, the fifth lens element, the sixth lens element, the seventh lens element and the eighth lens element has an object-side surface facing towards the object side and an image-side surface facing towards the image side;

wherein at least one surface of at least one of the lens elements of the second lens group is aspheric, and at least one surface of at least one of the lens elements of the third lens group is aspheric;

wherein the image-side surface of the eighth lens element is concave in a paraxial region thereof and comprises at least one inflection point;

wherein at least one of the eight lens elements has an Abbe number smaller than 20;

wherein a maximum of refractive indexes of all the lens elements of the image capturing optical assembly is Nmax, and the following condition is satisfied:

1.30< N max<1.75.

2. The image capturing optical assembly of claim 1 , wherein the eighth lens element has negative refractive power; the image-side surface of the eighth lens element comprises at least one critical point.

3. The image capturing optical assembly of claim 1 , wherein the image-side surface of the fourth lens element is concave in a paraxial region thereof.

4. The image capturing optical assembly of claim 1 , wherein the object-side surface of the first lens element comprises at least one inflection point.

5. The image capturing optical assembly of claim 1 , wherein there are at least two of the eight lens elements with an Abbe number smaller than 23.0; a focal length of the image capturing optical assembly is f, a focal length of the second lens element is f2, and the following condition is satisfied:

−0.55< f/f 2<0.55.

6. The image capturing optical assembly 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<( R 11− R 12)/( R 11+ R 12)<0.80.

7. The image capturing optical assembly of claim 1 , wherein a focal length of the image capturing optical assembly is f, a curvature radius of an object-side surface of one of the lens elements of the image capturing optical assembly is Rf, a curvature radius of an image-side surface of the lens element of the image capturing optical assembly is Rr, and at least one of the lens elements satisfies the following condition:

| f/Rf|+|f/Rr|< 0.40.

8. The image capturing optical assembly of claim 1 , wherein a half of a maximum field of view of the image capturing optical assembly is HFOV, a focal length of the image capturing optical assembly is f, an entrance pupil diameter of the image capturing optical assembly is EPD, and the following condition is satisfied:

24.0<HFOV× EPD/f< 35.0.

9. The image capturing optical assembly of claim 1 , wherein an entrance pupil diameter of the image capturing optical assembly is EPD, a sum of central thicknesses of all the lens elements of the image capturing optical assembly is ΣCT, and the following condition is satisfied:

0.80< EPD/ΣCT< 2.0.

10. The image capturing optical assembly of claim 1 , wherein 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 image capturing optical assembly is ImgH, a focal length of the image capturing optical assembly is f, a focal length of the first lens element is f1, a focal length of the second lens element is f2, a focal length of the third lens element is f3, a focal length of the fourth lens element is f4, a focal length of the fifth lens element is f5, a focal length of the sixth lens element is f6, a focal length of the seventh lens element is f7, a focal length of the eighth lens element is f8, a focal length of i-th lens element is fi, a maximum of |f/fi| is |f/fi|max, and the following conditions are satisfied:

0.80< TL /ImgH<1.65; and

| f/fi |max<1.50, wherein i= 1˜8.

11. The image capturing optical assembly of claim 1 , wherein a focal length of the image capturing optical assembly is f, a curvature radius of the image-side surface of the eighth lens element is R16; the image-side surface of the eighth lens element comprises at least one critical point, a vertical distance of the critical point on the image-side surface of the eighth lens element and an optical axis is Yc82, and the following conditions are satisfied:

0.3< f/R 16<5.0; and

0.01< Yc 82/ f< 0.90.

12. The image capturing optical assembly of claim 1 , wherein each of relative distances between every adjacent lens elements of the first lens element, the second lens element, the third lens element, the fourth lens element, the fifth lens element, the sixth lens element, the seventh lens element and the eighth lens element is a constant value, an entrance pupil diameter of the image capturing optical assembly is EPD, an axial distance between the image-side surface of the eighth lens element and an image surface is BL, and the following condition is satisfied:

2.0< EPD/BL< 6.2.

13. An imaging apparatus, comprising:

the image capturing optical assembly of claim 1 ; and

an image sensor disposed on an image surface of the image capturing optical assembly.

14. An electronic device, comprising:

the imaging apparatus of claim 13 .

15. An image capturing optical assembly comprising, in order from an object side to an image side:

a first lens group, a second lens group and a third lens group;

wherein the first lens group comprises, in order from the object side to the image side, a first lens element and a second lens element; the second lens group comprises, in order from the object side to the image side, a third lens element, a fourth lens element and a fifth lens element; and the third lens group comprises, in order from the object side to the image side, a sixth lens element, a seventh lens element and an eighth lens element;

wherein each of the first lens element, the second lens element, the third lens element, the fourth lens element, the fifth lens element, the sixth lens element, the seventh lens element and the eighth lens element has an object-side surface facing towards the object side and an image-side surface facing towards the image side;

wherein at least one surface of at least one of the lens elements of the second lens group is aspheric, and at least one surface of at least one of the lens elements of the third lens group is aspheric;

wherein the image-side surface of the eighth lens element is concave in a paraxial region thereof and comprises at least one inflection point;

wherein at least one of the eight lens elements has an Abbe number smaller than 20;

wherein a maximum of refractive indexes of all the lens elements of the image capturing optical assembly is Nmax, the image capturing optical assembly further comprises an aperture stop, an axial distance between the aperture stop and the image-side surface of the eighth lens element is SD, an axial distance between the object-side surface of the first lens element and the image-side surface of the eighth lens element is TD, and the following conditions are satisfied:

1.30< N max<1.95; and

0.70< SD/TD< 1.10.

16. The image capturing optical assembly of claim 15 , wherein the object-side surface of the seventh lens element is convex in a paraxial region thereof, and the image-side surface of the seventh lens element is concave in a paraxial region thereof.

17. The image capturing optical assembly of claim 15 , wherein the image-side surface of the second lens element is concave in a paraxial region thereof; a maximum optical effective radius of the object-side surface of the first lens element is Y11, a maximum optical 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.

18. The image capturing optical assembly of claim 15 , wherein a maximum of axial distances between every adjacent lens elements of the image capturing optical assembly is ATmax, a maximum image height of the image capturing optical assembly is ImgH, and the following condition is satisfied:

AT max/ImgH<0.30.

19. The image capturing optical assembly of claim 15 , wherein 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 image capturing optical assembly is ImgH, an entrance pupil diameter of the image capturing optical assembly is EPD, and the following condition is satisfied:

TL{circumflex over ( )} 2/(ImgH× EPD )<3.40.

20. The image capturing optical assembly of claim 15 , wherein an Abbe number of the first lens element is V1, an Abbe number of the second lens element is V2, an Abbe number of the sixth lens element is V6, and the following condition is satisfied:

( V 2+ V 6)/ V 1<1.0.

21. The image capturing optical assembly of claim 15 , wherein 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 image capturing optical assembly is ImgH, a focal length of the image capturing optical assembly is f, an entrance pupil diameter of the image capturing optical assembly is EPD, and the following condition is satisfied:

2.0< TL /ImgH+ f/EPD≤ 3.20.

22. The image capturing optical assembly of claim 15 , wherein the second lens group has positive refractive power, and the third lens group has negative refractive power.

23. An image capturing optical assembly comprising, in order from an object side to an image side:

a first lens group, a second lens group and a third lens group;

wherein the first lens group comprises, in order from the object side to the image side, a first lens element and a second lens element; the second lens group comprises, in order from the object side to the image side, a third lens element, a fourth lens element and a fifth lens element; and the third lens group comprises, in order from the object side to the image side, a sixth lens element, a seventh lens element and an eighth lens element;

wherein each of the first lens element, the second lens element, the third lens element, the fourth lens element, the fifth lens element, the sixth lens element, the seventh lens element and the eighth lens element has an object-side surface facing towards the object side and an image-side surface facing towards the image side;

wherein at least one surface of at least one of the lens elements of the first lens group is aspheric, at least one surface of at least one of the lens elements of the second lens group is aspheric, and at least one surface of at least one of the lens elements of the third lens group is aspheric;

wherein the image-side surface of the eighth lens element is concave in a paraxial region thereof and comprises at least one inflection point;

wherein at least one of the eight lens elements has an Abbe number smaller than 20;

wherein a maximum of refractive indexes of all the lens elements of the image capturing optical assembly is Nmax, an axial distance between the object-side surface of the first lens element and an image surface is TL, a focal length of the image capturing optical assembly is f, and the following conditions are satisfied:

1.30< N max<1.95; and

TL/f< 1.60.

24. The image capturing optical assembly of claim 23 , wherein the second lens element has negative refractive power, the object-side surface of the second lens element is convex in a paraxial region thereof, and the image-side surface of the second lens element is concave in a paraxial region thereof; the first lens element, the second lens element, the third lens element, the fourth lens element, the fifth lens element, the sixth lens element, the seventh lens element and the eighth lens element are made of plastic materials.

25. The image capturing optical assembly of claim 23 , wherein the axial distance between the object-side surface of the first lens element and the image surface is TL, an entrance pupil diameter of the image capturing optical assembly is EPD, and the following condition is satisfied:

1.0< TL/EPD< 2.27.

26. The image capturing optical assembly of claim 23 , wherein a focal length of the image capturing optical assembly is f, a curvature radius of the image-side surface of the eighth lens element is R16, and the following condition is satisfied:

0.3< f/R 16≤3.39.

27. The image capturing optical assembly of claim 23 , wherein there is an air gap in a paraxial region between each of adjacent lens elements of the image capturing optical assembly; at least one surface of at least one of the lens elements of the first lens group comprises at least one inflection point, at least one surface of at least one of the lens elements of the second lens group comprises at least one inflection point, and at least one surface of at least one of the lens elements of the third lens group comprises at least one inflection point; the axial distance between the object-side surface of the first lens element and the image surface is TL, and the following condition is satisfied:

TL< 12.0 mm.

28. The image capturing optical assembly of claim 23 , wherein the focal length of the image capturing optical assembly is f, a focal length of the second lens group is fG2, a focal length of the third lens group is fG3, and the following conditions are satisfied:

−0.4< f/fG 2<1.5; and

−1.5< f/fG 3<0.5.

29. The image capturing optical assembly of claim 23 , wherein the image-side surface of the seventh lens element comprises at least one critical point, a vertical distance of the critical point on the image-side surface of the seventh lens element and an optical axis is Yc72, and the following condition is satisfied:

0.01< Yc 72/ f< 0.90.