Imaging lens system, image capturing unit and electronic device

1. An imaging 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 first lens element has positive refractive power, the object-side surface of the first lens element is convex in a paraxial region thereof, the second lens element has negative refractive power, the object-side surface of the second lens element is concave in a paraxial region thereof, the object-side surface of the fourth lens element is convex in a paraxial region thereof, the sixth lens element has positive refractive power, the image-side surface of the seventh lens element is concave in a paraxial region thereof, and the image-side surface of the seventh lens element has at least one inflection point in an off-axis region thereof;

wherein a curvature radius of the object-side surface of the first lens element is R 1 , a curvature radius of the object-side surface of the second lens element is R 3 , a curvature radius of the image-side surface of the second lens element is R 4 , a curvature radius of the image-side surface of the seventh lens element is R 14 , an axial distance between the third lens element and the fourth lens element is T 34 , an axial distance between the fourth lens element and the fifth lens element is T 45 , and the following conditions are satisfied:

( R 3+ R 4)/( R 3− R 4)<0;

0< T 34/ T 45<10.0; and

0.45< R 1/ R 14<5.0.

2. The imaging lens system of claim 1 , wherein a focal length of the imaging lens system is f, a curvature radius of the image-side surface of the fourth lens element is R 8 , and the following condition is satisfied:

0≤ f/R 8<10.0.

3. The imaging lens system of claim 1 , wherein a minimum value among Abbe numbers of all lens elements of the imaging lens system is Vmin, and the following condition is satisfied:

10.0 <V min<22.0.

4. The imaging lens system of claim 1 , wherein the object-side surface of the second lens element has at least one convex critical point in an off-axis region thereof, a vertical distance between a critical point on the object-side surface of the second lens element and an optical axis is Yc 21 , a central thickness of the second lens element is CT 2 , and the following condition is satisfied:

0.50< Yc 21/CT2<8.50.

5. The imaging lens system of claim 1 , wherein an Abbe number of the second lens element is V2, an Abbe number of the fourth lens element is V4, an Abbe number of the fifth lens element is V5, and the following condition is satisfied:

30.0< V 2+ V 4+ V 5<93.0.

6. The imaging 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, an entrance pupil diameter of the imaging lens system is EPD, and the following condition is satisfied:

1.0< TL /EPD<2.35.

7. The imaging lens system of claim 1 , wherein a central thickness of the second lens element is CT 2 , a central thickness of the third lens element is CT 3 , a central thickness of the fourth lens element is CT 4 , a central thickness of the fifth lens element is CT 5 , a central thickness of the sixth lens element is CT 6 , and the following condition is satisfied:

0.30<(CT2+CT3+CT4+CT5)/CT6<1.80.

8. The imaging lens system of claim 1 , wherein a focal length of the fifth lens element is f5, a focal length of the seventh lens element is f7, and the following condition is satisfied:

−0.40< f 7/ f 5<0.40.

9. An image capturing unit, comprising:

the imaging lens system of claim 1 ; and

an image sensor disposed on an image surface of the imaging lens system.

10. An electronic device, comprising:

a first image capturing unit, comprising the imaging lens system of claim 1 and a first image sensor, wherein the first image sensor is disposed on an image surface of the imaging lens system; and

a second image capturing unit, comprising an optical lens assembly and a second image sensor, wherein the second image sensor is disposed on an image surface of the optical lens assembly.

11. An imaging 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 first lens element has positive refractive power, the second lens element has negative refractive power, the object-side surface of the second lens element is concave in a paraxial region thereof, the object-side surface of the fourth lens element is convex in a paraxial region thereof, the seventh lens element has negative refractive power, the image-side surface of the seventh lens element is concave in a paraxial region thereof, and the image-side surface of the seventh lens element has at least one inflection point in an off-axis region thereof;

wherein a curvature radius of the object-side surface of the second lens element is R 3 , a curvature radius of the image-side surface of the second lens element is R 4 , a curvature radius of the image-side surface of the fifth lens element is R 10 , a curvature radius of the object-side surface of the seventh lens element is R 13 , a curvature radius of the image-side surface of the seventh lens element is R 14 , an axial distance between the third lens element and the fourth lens element is T 34 , an axial distance between the fourth lens element and the fifth lens element is T 45 , a focal length of the imaging lens system is f, a focal length of the first lens element is f1, and the following conditions are satisfied:

( R 3+ R 4)/( R 3− R 4)<0.50;

0< T 34/ T 45<10.0;

0.15<( R 13+ R 14)/( R 13− R 14)<2.80;

−1.80< f/R 10<10.0; and

0.30< f/f 1<3.50.

12. The imaging lens system of claim 11 , wherein the focal length of the imaging lens system is f, the curvature radius of the image-side surface of the fifth lens element is R 10 , and the following condition is satisfied:

0≤ f/R 10<5.0.

13. The imaging lens system of claim 11 , wherein a maximum effective radius of the image-side surface of the third lens element is Y 32 , 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 imaging lens system is ImgH, and the following condition is satisfied:

1.0<( Y 32 +TL )/Img H <2.0

14. The imaging lens system of claim 11 , wherein the focal length of the imaging lens system is f, the 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 i-th lens element is fi, a minimum absolute value of f/fi is |f/fi|min, and the following condition is satisfied:

| f/fi |min<0.10, wherein i= 1, 2, 3, 4, 5, 6, 7.

15. The imaging lens system of claim 11 , further comprising an aperture stop, wherein an axial distance between the aperture stop and the image-side surface of the seventh lens element is SD, an axial distance between the object-side surface of the first lens element and the image-side surface of the seventh lens element is TD, the focal length of the imaging lens system is f, a curvature radius of the object-side surface of the sixth lens element is R 11 , and the following conditions are satisfied:

0.75< SD/TD< 1.0; and

0≤ f/R 11<2.50.

16. The imaging lens system of claim 11 , wherein the axial distance between the fourth lens element and the fifth lens element is T 45 , an axial distance between the fifth lens element and the sixth lens element is T 56 , the focal length of the imaging lens system is f, an entrance pupil diameter of the imaging lens system is EPD, and the following conditions are satisfied:

0< T 45/ T 56<1.0; and

1.0< f /EPD<2.0.

17. The imaging lens system of claim 11 , 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 imaging lens system is ImgH, the focal length of the imaging lens system is f, an entrance pupil diameter of the imaging lens system is EPD, and the following condition is satisfied:

1.50<( TL /Img H )+( f /EPD)<3.40.

18. The imaging lens system of claim 11 , wherein an axial distance between the fifth lens element and the sixth lens element is T 56 , an axial distance between the sixth lens element and the seventh lens element is T 67 , the curvature radius of the image-side surface of the fifth lens element is R 10 , a curvature radius of the object-side surface of the sixth lens element is R 11 , and the following conditions are satisfied:

0.6< T 67/ T 56<2.80; and

−0.70<( R 10− R 11)/( R 10+ R 11)<2.0.

19. An imaging 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 second lens element is concave in a paraxial region thereof, the object-side surface of the third lens element is convex in a paraxial region thereof, the object-side surface of the fourth lens element is convex in a paraxial region thereof, the image-side surface of the fifth lens element is concave in a paraxial region thereof, the seventh lens element has negative refractive power, the image-side surface of the seventh lens element is concave in a paraxial region thereof, and the image-side surface of the seventh lens element has at least one inflection point in an off-axis region thereof;

wherein a curvature radius of the object-side surface of the second lens element is R 3 , a curvature radius of the image-side surface of the second lens element is R 4 , an axial distance between the third lens element and the fourth lens element is T 34 , an axial distance between the fourth lens element and the fifth lens element is T 45 , a focal length of the imaging lens system is f, a focal length of the seventh lens element is f7, a central thickness of the first lens element is CT 1 , a central thickness of the second lens element is CT 2 , and the following conditions are satisfied:

−0.80< R 3/ R 4;

0< T 34/ T 45<10.0;

−3.80< f/f 7<−0.25; and

1.35<CT1/CT2<7.0.

20. The imaging lens system of claim 19 , wherein the object-side surface of the sixth lens element is convex in a paraxial region thereof, and the object-side surface and the image-side surface of the third lens element are both aspheric.

21. The imaging lens system of claim 19 , wherein the object-side surface of the seventh lens element has at least one convex critical point in an off-axis region thereof, a vertical distance between a critical point on the object-side surface of the seventh lens element and an optical axis is Yc 71 , the focal length of the imaging lens system is f, and the following condition is satisfied:

0.20< Yc 71/ f< 1.0.

22. The imaging lens system of claim 19 , wherein the object-side surface of the second lens element has at least one convex critical point in an off-axis region thereof, a vertical distance between a critical point on the object-side surface of the second lens element and an optical axis is Yc 21 , the central thickness of the second lens element is CT 2 , and the following condition is satisfied:

0.50< Yc 21/CT2<8.50.

23. The imaging lens system of claim 19 , wherein an Abbe number of the second lens element is V2, an Abbe number of the fourth lens element is V4, an Abbe number of the fifth lens element is V5, and the following condition is satisfied:

30.0< V 2+ V 4+ V 5<93.0.

24. The imaging lens system of claim 19 , wherein an axial distance between the object-side surface of the first lens element and an image surface is TL, an entrance pupil diameter of the imaging lens system is EPD, and the following condition is satisfied:

1.0< TL /EPD<2.35.

25. The imaging lens system of claim 19 , wherein a curvature radius of the object-side surface of the third lens element is R 5 , a curvature radius of the image-side surface of the third lens element is R 6 , 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 imaging lens system is ImgH, and the following conditions are satisfied:

−40.0<( R 5+ R 6)/( R 5− R 6)<3.0; and

1.0< TL /Img H <1.80.

26. The imaging lens system of claim 19 , wherein the image-side surface of the seventh lens element has at least one convex critical point in an off-axis region thereof, a vertical distance between a critical point on the image-side surface of the seventh lens element and an optical axis is Yc 72 , a maximum effective radius of the image-side surface of the seventh lens element is Y 72 , an axial distance between the object-side surface of the first lens element and an image surface is TL, the focal length of the imaging lens system is f, and the following conditions are satisfied:

0.10< Yc 72/ Y 72<1.0; and

0.80< TL/f< 1.40.

27. An imaging 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 second lens element is concave in a paraxial region thereof, the image-side surface of the second lens element is concave in a paraxial region thereof, the image-side surface of the seventh lens element is concave in a paraxial region thereof, and the image-side surface of the seventh lens element has at least one inflection point in an off-axis region thereof;

wherein a curvature radius of the object-side surface of the second lens element is R 3 , a curvature radius of the image-side surface of the second lens element is R 4 , a curvature radius of the image-side surface of the fifth lens element is R 10 , an Abbe number of the fifth lens element is V5, half of a maximum field of view of the imaging lens system is HFOV, a focal length of the imaging lens system is f, a focal length of the third lens element is f3, and the following conditions are satisfied:

−0.80< R 3/ R 4;

10.0 <V 5<28.0;

30.0 [deg.]< H FOV<55.0 [deg.];

−0.90< fR 10<10.0; and

−3.0< f/f 3<1.0.

28. The imaging lens system of claim 27 , wherein the focal length of the imaging lens system is f, a curvature radius of the image-side surface of the fourth lens element is R 8 , and following condition is satisfied:

0≤ f/R 8<10.0.

29. The imaging lens system of claim 27 , wherein an axial distance between the image-side surface of the seventh lens element and an image surface is BL, a maximum value among central thicknesses of all lens elements of the imaging lens system is CTmax, and the following condition is satisfied:

0 <BL /CTmax<1.0.

30. The imaging lens system of claim 27 , wherein a central thickness of the second lens element is CT 2 , a central thickness of the third lens element is CT 3 , a central thickness of the fourth lens element is CT 4 , a central thickness of the fifth lens element is CT 5 , a central thickness of the sixth lens element is CT 6 , and the following condition is satisfied:

0.50<(CT2+CT3+CT4+CT5)/CT6<1.50.

31. The imaging lens system of claim 27 , 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 imaging lens system is ImgH, the focal length of the imaging lens system is f, an entrance pupil diameter of the imaging lens system is EPD, and the following condition is satisfied:

1.50<( TL /Img H )+( f /EPD)<3.40.

32. The imaging lens system of claim 27 , wherein the image-side surface of the fifth lens element has at least one critical point in an off-axis region thereof, a vertical distance between a critical point on the image-side surface of the fifth lens element and an optical axis is Yc 52 , the focal length of the imaging lens system is f, and the following condition is satisfied:

0.05< Yc 52/ f< 0.80.

33. The imaging lens system of claim 27 , wherein each of at least three lens elements of the imaging lens system has an Abbe number ranging from 10.0 to 32.0, the focal length of the imaging lens system is f, a maximum image height of the imaging lens system is ImgH, and the following condition is satisfied:

0.55 <f /Img H <1.50.