Photographing optical lens system, image capturing unit and electronic device

1 . A photographing optical lens system 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, and each of the eight lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;

wherein the image-side surface of the seventh lens element has at least one inflection point, the object-side surface of the eighth lens element has at least one inflection point, the image-side surface of the eighth lens element has at least one inflection point, and the photographing optical lens system further comprises an aperture stop; and

wherein 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 condition is satisfied:

0.7

<

Sd

/

Td

<

1.2

.

2 . The photographing optical lens system 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 system of claim 1 , wherein the eighth lens element has negative refractive power.

4 . The photographing optical lens system of claim 1 , wherein the sixth lens element has at least one inflection point.

5 . 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-side surface of the eighth lens element is Td, a focal length of the photographing optical lens system is f, and the following condition is satisfied:

Td

/

f

<

1.5

.

6 . The photographing optical lens system of claim 1 , wherein a sum of central thicknesses of all lens elements of the photographing optical lens system is ΣCT, 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:

2.5

<

Σ

⁢

CT

/

BL

<

6.5

.

7 . The photographing optical lens system 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 photographing optical lens system is ImgH, and the following condition is satisfied:

TL

/

ImgH

<

3.

.

8 . The photographing optical lens system of claim 1 , wherein the object-side surface and the image-side surface of the fifth lens element are both aspheric; and

wherein a focal length of the second lens element is f2, a focal length of the seventh lens element is f7, and the following condition is satisfied:

❘

"\[LeftBracketingBar]"

f

⁢

7

/

f

⁢

2

❘

"\[RightBracketingBar]"

<

1.

.

9 . The photographing optical lens system of claim 1 , 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 eighth lens element is Y82, and the following condition is satisfied:

Y

⁢

11

/

Y

⁢

82

<

1

.

2

⁢

5

.

10 . The photographing optical lens system of claim 1 , wherein a vertical distance between a non-axial critical point on the image-side surface of the eighth lens element and an optical axis is Yc82, a focal length of the photographing optical lens system is f, and the following condition is satisfied:

0

.

1

⁢

0

<

Yc

⁢

82

/

f

<

0

.

8

⁢

0

.

11 . An image capturing unit comprising:

the photographing optical lens system of claim 1 ; and

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

12 . An electronic device comprising:

the image capturing unit of claim 11 .

13 . A photographing optical lens system 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, and each of the eight lens elements having an object-side surface facing toward the object side and an image-side surface facing toward the image side;

wherein the sixth lens element has at least one inflection point, and the image-side surface of the seventh lens element has at least one inflection point; and

wherein a sum of central thicknesses of all lens elements of the photographing optical lens system is ΣCT, an axial distance between the image-side surface of the eighth lens element and an image surface is BL, a focal length of the photographing optical lens system is f, a composite focal length of the first lens element, the second lens element and the third lens element is f123, and the following conditions are satisfied:

1.5

<

Σ

⁢

CT

/

BL

;

and

0.3

<

f

/

f

⁢

123

<

1.5

.

14 . The photographing optical lens system of claim 13 , wherein the object-side surface of the second lens element is convex in a paraxial region thereof, and the image-side surface of the third lens element is concave in a paraxial region thereof.

15 . The photographing optical lens system of claim 13 , wherein a curvature radius of the object-side surface of the eighth lens element is R 15 , a curvature radius of the image-side surface of the eighth lens element is R 16 , and the following condition is satisfied:

-

0.5

<

(

R

⁢

1

⁢

5

+

R

⁢

16

)

/

(

R

⁢

15

-

R

⁢

16

)

.

16 . The photographing optical lens system of claim 13 , wherein the object-side surface and the image-side surface of the eighth lens element are both aspheric, the image-side surface of the eighth lens element is concave in a paraxial region thereof, and the image-side surface of the eighth lens element has at least one convex shape in an off-axis region thereof.

17 . The photographing optical lens system of claim 13 , wherein the eighth lens element has at least one inflection point; and

wherein the sum of central thicknesses of all lens elements of the photographing optical lens system is ΣCT, the axial distance between the image-side surface of the eighth lens element and the image surface is BL, and the following condition is satisfied:

2.

<

Σ

⁢

CT

/

BL

<

10.

18 . The photographing optical lens system of claim 17 , wherein 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, the focal length of the photographing optical lens system is f, and the following condition is satisfied:

Td

/

f

<

2.

.

19 . The photographing optical lens system of claim 17 , wherein a maximum image height of the photographing optical lens system is ImgH, the focal length of the photographing optical lens system is f, and the following condition is satisfied:

0.65

<

ImgH

/

f

<

1

.

4

⁢

0

.

20 . The photographing optical lens system of claim 13 , wherein the first lens element has positive refractive power.

21 . The photographing optical lens system of claim 13 , wherein 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, an entrance pupil diameter of the photographing optical lens system is EPD, and the following condition is satisfied:

Td

/

EPD

<

3.

.