Optical imaging lens

1. An optical imaging lens comprising 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 sequentially from an object side to an image side along an optical axis, each of the first, second, third, fourth, fifth, sixth, seventh and eighth lens elements having an object-side surface facing toward the object side and allowing imaging rays to pass through as well as an image-side surface facing toward the image side and allowing the imaging rays to pass through, the optical imaging lens comprises no other lens elements having refracting power beyond the first, second, third, fourth, fifth, sixth, seventh and eighth lens elements wherein:

an optical axis region of the image-side surface of the first lens element is concave;

the second lens element has negative refracting power;

a periphery region of the object-side surface of the fifth lens element is concave;

an optical axis region of the image-side surface of the fifth lens element is convex;

an optical axis region of the image-side surface of the sixth lens element is concave;

an optical axis region of the image-side surface of the seventh lens element is concave;

materials of the third lens element, the fourth lens element, and the eighth lens element are plastic;

a distance from the object-side surface of the first lens element to the image-side surface of the eighth lens element along the optical axis is represented by TL;

a distance from the image-side surface of the eighth lens element to an image plane along the optical axis is represented by BFL; and

the optical imaging lens further satisfies an inequality: TL/BFL≤5.500.

2. The optical imaging lens according to claim 1 , wherein a sum of thicknesses of the eight lens elements from the first lens element to the eighth lens element along the optical axis is represented by ALT, a thickness of the first lens element along the optical axis is represented by T1, a distance between the image-side surface of the second lens element and the object-side surface of the third lens element along the optical axis is represented by G23, and the optical imaging lens further satisfies an inequality: ALT/(T1+G23)≤5.000.

3. The optical imaging lens according to claim 1 , wherein a sum of seven air gaps from the first lens element to the eighth lens elements along the optical axis is represented by MG, a thickness of the first lens element along the optical axis is represented by T1, a thickness of the fifth lens element along the optical axis is represented by T5, and the optical imaging lens further satisfies an inequality: AAG/(T1+T5)≤2.500.

4. The optical imaging lens according to claim 1 , wherein a thickness of the sixth lens element along the optical axis is represented by T6, a thickness of the seventh lens element along the optical axis is represented by T7, a thickness of the eighth lens element along the optical axis is represented by T8, and the optical imaging lens further satisfies an inequality: (T7+T8)/T6≤3.300.

5. The optical imaging lens according to claim 1 , wherein a thickness of the fourth lens element along the optical axis is represented by T4, a distance between the image-side surface of the fourth lens element and the object-side surface of the fifth lens element along the optical axis is represented by G45, a thickness of the fifth lens element along the optical axis is represented by T5, a distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element along the optical axis is represented by G34, and the optical imaging lens further satisfies an inequality: (T4+G45+T5)/G34≥1.500.

6. The optical imaging lens according to claim 1 , wherein an effective focal length of the optical imaging lens is represented by EFL, a thickness of the sixth lens element along the optical axis is represented by T6, a thickness of the seventh lens element along the optical axis is represented by T7, and the optical imaging lens further satisfies an inequality: EFL/(T6+T7)≥3.900.

7. The optical imaging lens according to claim 1 , wherein a thickness of the sixth lens element along the optical axis is represented by T6, a distance between the image-side surface of the sixth lens element and the object-side surface of the seventh lens element along the optical axis is represented by G67, a thickness of the seventh lens element along the optical axis is represented by T7, a distance between the image-side surface of the seventh lens element and the object-side surface of the eighth lens element along the optical axisis represented by G78, a thickness of the eighth lens element along the optical axis is represented by T8, a thickness of the first lens element along the optical axis is represented by T1, a distance between the image-side surface of the first lens element and the object-side surface of the second lens element along the optical axis is represented by G12, a thickness of the second lens element along the optical axis is represented by T2, and the optical imaging lens further satisfies an inequality: (T6+G67+T7+G78+T8)/(T1+G12+T2)≤2.200.

8. The optical imaging lens according to claim 1 , wherein a thickness of the third lens element along the optical axis is represented by T3, a distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element along the optical axis is represented by G34, a thickness of the second lens element along the optical axis is represented by T2, a distance between the image-side surface of the second lens element and the object-side surface of the third lens element along the optical axis is represented by G23, and the optical imaging lens further satisfies an inequality: (T3+G34)/(T2+G23)≤2.800.

9. The optical imaging lens according to claim 1 , wherein a thickness of the first lens element along the optical axis is represented by T1, a distance between the image-side surface of the first lens element and the object-side surface of the second lens element along the optical axis is represented by G12, a thickness of the fifth lens element along the optical axis is represented by T5, a distance between the image-side surface of the fifth lens element and the object-side surface of the sixth lens element along the optical axis is represented by G56, and the optical imaging lens further satisfies an inequality: (T1+G12)/(T5+G56)≤2.200.

10. The optical imaging lens according to claim 1 , wherein a thickness of the first lens element along the optical axis is represented by T1, a thickness of the eighth lens element along the optical axis is represented by T8, and the optical imaging lens further satisfies an inequality: T1/T8≥1.200.

11. The optical imaging lens according to claim 1 , wherein a distance from the object-side surface of the first lens element to an image plane along the optical axis is represented by TTL, a sum of thicknesses of the eight lens elements from the first lens element to the eighth lens element along the optical axis is represented by ALT, and the optical imaging lens further satisfies an inequality: TTL/ALT≤2.200.

12. The optical imaging lens according to claim 1 , wherein a sum of seven air gaps from the first lens element to the eighth lens elements along the optical axis is represented by MG, a distance between the image-side surface of the first lens element and the object-side surface of the second lens element along the optical axis is represented by G12, a distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element along the optical axis is represented by G34, and the optical imaging lens further satisfies an inequality: AAG/(G12+G34)≥2.000.

13. The optical imaging lens according to claim 1 , wherein a thickness of the first lens element along the optical axis is represented by T1, a distance between the image-side surface of the first lens element and the object-side surface of the second lens element along the optical axis is represented by G12, a thickness of the second lens element along the optical axis is represented by T2, and the optical imaging lens further satisfies an inequality: T1/(G12+T2)≥1.300.

14. The optical imaging lens according to claim 1 , wherein a thickness of the third lens element along the optical axis is represented by T3, a thickness of the fifth lens element along the optical axis is represented by T5, a thickness of the fourth lens element along the optical axis is represented by T4, and the optical imaging lens further satisfies an inequality: (T3+T5)/T4≥2.500.

15. The optical imaging lens according to claim 1 , wherein a thickness of the sixth lens element along the optical axis is represented by T6, a thickness of the seventh lens element along the optical axis is represented by T7, a thickness of the second lens element along the optical axis is represented by T2, and the optical imaging lens further satisfies an inequality: (T6+T7)/T2≤3.800.

16. The optical imaging lens according to claim 1 , wherein an effective focal length of the optical imaging lens is represented by EFL, a sum of seven air gaps from the first lens element to the eighth lens elements along the optical axis is represented by MG, and the optical imaging lens further satisfies an inequality: EFL/AAG≥2.200.

17. The optical imaging lens according to claim 1 , wherein a distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element along the optical axis is represented by G34, a distance between the image-side surface of the fourth lens element and the object-side surface of the fifth lens element along the optical axis is represented by G45, a distance between the image-side surface of the second lens element and the object-side surface of the third lens element along the optical axis is represented by G23, and the optical imaging lens further satisfies an inequality: (G34+G45)/G23≤4.000.

18. The optical imaging lens according to claim 1 , wherein a thickness of the first lens element along the optical axis is represented by T1, a thickness of the third lens element along the optical axis is represented by T3, a distance between the image-side surface of the third lens element and the object-side surface of the fourth lens element along the optical axisis represented by G34, and the optical imaging lens further satisfies an inequality: (T1+T3)/G34≥1.500.

19. The optical imaging lens according to claim 1 , wherein a sum of thicknesses of the eight lens elements from the first lens element to the eighth lens element along the optical axis is represented by ALT, a sum of seven air gaps from the first lens element to the eighth lens elements along the optical axis is represented by MG, and the optical imaging lens further satisfies an inequality: ALT/AAG≥1.600.

20. An optical imaging lens comprising 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 sequentially from an object side to an image side along an optical axis, each of the first, second, third, fourth, fifth, sixth, seventh and eighth lens elements having an object-side surface facing toward the object side and allowing imaging rays to pass through as well as an image-side surface facing toward the image side and allowing the imaging rays to pass through, the optical imaging lens comprises no other lens elements having refracting power beyond the first, second, third, fourth, fifth, sixth, seventh and eighth lens elements wherein:

the image-side surface of the first lens element is concave from an optical axis region to a periphery region without a transition point;

the second lens element has negative refracting power;

a periphery region of the object-side surface of the fifth lens element is concave;

an optical axis region of the image-side surface of the fifth lens element is convex;

an optical axis region of the image-side surface of the sixth lens element is concave;

an optical axis region of the image-side surface of the seventh lens element is concave; and

materials of the third lens element, the fourth lens element, and the eighth lens element are plastic.