Photographing system, image capturing unit and electronic device
A photographing system includes, 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 with refractive power. The first lens element with positive refractive power has an object-side surface being convex in paraxial region. The second lens element with refractive power has an image-side surface being concave in paraxial region. The third, fourth and fifth lens elements all have refractive powers. The sixth lens element with refractive power has an image-side surface being concave in paraxial region, wherein the image-side surface has at least one convex shape in off-axis region, and both of two surfaces are aspheric. The seventh lens element with refractive power has an object-side surface being concave in paraxial region, and both of two surfaces are aspheric.
1. A photographing system comprising seven lens elements, the seven lens elements being, in order from an object side to an image side:
a first lens element having positive refractive power;
a second lens element having negative refractive power;
a third lens element having an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof;
a fourth lens element having an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof;
a fifth lens element;
a sixth lens element; and
a seventh lens element having an image-side surface being concave in a paraxial region thereof, wherein at least one of an object-side surface and the image-side surface of the seventh lens element has at least one inflection point;
wherein there is an air gap in a paraxial region between every adjacent lens element 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 and the seventh lens element, a focal length of the photographing system is f, 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, and the following condition is satisfied:
| f/f 3 |+|f/f 4 |+|f/f 5|≤0.94.
2. The photographing system of claim 1 , wherein a focal length of the first lens element is f1, a focal length of the second lens element is f2, the focal length of the third lens element is f3, the focal length of the fourth lens element is f4, the focal length of the fifth lens element is f5, a focal length of the sixth lens element is f6, a focal length of the x-th lens element is fx, and the following condition is satisfied:
| f 1 |<|fx |, wherein x= 2, 3, 4, 5, 6.
3. The photographing system of claim 1 , wherein a focal length of the second lens element is f2, the focal length of the third lens element is f3, the focal length of the fourth lens element is f4, the 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 x-th lens element is fx, and the following condition is satisfied:
| f 7 |<|fx |, wherein x= 2, 3, 4, 5, 6.
4. The photographing system of claim 1 , wherein the second lens element has an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof.
5. The photographing system of claim 1 , wherein an Abbe number of the first lens element is V1, an Abbe number of the second lens element is V2, and the following condition is satisfied:
25 <V 1 −V 2<45.
6. The photographing system of claim 1 , wherein an f-number of the photographing system is Fno, and the following condition is satisfied:
Fno≤2.25.
7. The photographing system of claim 1 , wherein the sixth lens element has an image-side surface being concave in a paraxial region thereof, and the image-side surface of the sixth lens element has at least one convex shape in an off-axis region thereof.
8. The photographing system of claim 1 , wherein an axial distance between an object-side surface of the first lens element and the image-side surface of the fourth lens element is Dr1r8, an axial distance between an object-side surface of the fifth lens element and the image-side surface of the seventh lens element is Dr9r14, and the following condition is satisfied:
0.75< Dr 1 r 8/ Dr 9 r 14<1.5.
9. The photographing system of claim 1 , wherein the focal length of the photographing system is f, a composite focal length of the third lens element, the fourth lens element and the fifth lens element is f345, and the following condition is satisfied:
−0.30< f/f 345<0.60.
10. The photographing system of claim 1 , wherein a sum of axial distances between every adjacent lens element 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 and the seventh lens element is ΣAT, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and the following condition is satisfied:
3.0 <ΣAT /( T 34+ T 45)<10.0.
11. The photographing system of claim 1 , wherein the focal length of the photographing system is f, a curvature radius of an image-side surface of the sixth lens element is R12, a curvature radius of the object-side surface of the seventh lens element is R13, and the following condition is satisfied:
0.40<( f/R 12)−( f/R 13)<3.5.
12. The photographing system of claim 1 , wherein the first lens element has an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof.
13. The photographing system of claim 1 , wherein the image-side surface of the third lens element has at least one convex shape in an off-axis region thereof.
14. An image capturing unit, comprising:
the photographing system of claim 1 ; and
an image sensor disposed on an image surface of the photographing system.
15. An electronic device, comprising:
the image capturing unit of claim 14 .
16. A photographing system comprising seven lens elements, the seven lens elements being, in order from an object side to an image side:
a first lens element having positive refractive power;
a second lens element with negative refractive power having an image-side surface being concave in a paraxial region thereof;
a third lens element having an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof;
a fourth lens element having an object-side surface being convex in a paraxial region thereof and an image-side surface being concave in a paraxial region thereof;
a fifth lens element;
a sixth lens element; and
a seventh lens element having an image-side surface being concave in a paraxial region thereof, wherein at least one of an object-side surface and the image-side surface of the seventh lens element has at least one inflection point;
wherein there is an air gap in a paraxial region between every adjacent lens element 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 and the seventh lens element, a focal length of the photographing system 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 x-th lens element is fx, and the following conditions are satisfied:
| f 1|<| fx |, wherein x= 2, 3, 4, 5, 6; and
| f/f 3|+| f/f 4 |+|f/f 5|<1.5.
17. The photographing system of claim 16 , wherein a sum of axial distances between every adjacent lens element 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 and the seventh lens element is ΣAT, an axial distance between the third lens element and the fourth lens element is T34, an axial distance between the fourth lens element and the fifth lens element is T45, and the following condition is satisfied:
3.0<Σ AT /( T 34 +T 45)<10.0.
18. The photographing system of claim 16 , wherein the focal length of the photographing system is f, a curvature radius of an image-side surface of the sixth lens element is R12, a curvature radius of the object-side surface of the seventh lens element is R13, and the following condition is satisfied:
0.40<( f/R 12)−( f/R 13)<3.5.
19. The photographing system of claim 16 , wherein an Abbe number of the first lens element is V1, an Abbe number of the second lens element is V2, and the following condition is satisfied:
25< V 1 −V 2<45.
20. The photographing system of claim 16 , wherein an f-number of the photographing system is Fno, and the following condition is satisfied:
Fno≤2.25.
21. The photographing system of claim 16 , wherein an axial distance between an object-side surface of the first lens element and the image-side surface of the fourth lens element is Dr1r8, an axial distance between an object-side surface of the fifth lens element and the image-side surface of the seventh lens element is Dr9r14, and the following condition is satisfied:
0.75 <Dr 1 r 8/ Dr 9 r 14<1.5.
22. The photographing system of claim 16 , wherein an object-side surface of the sixth lens element has at least one critical point in an off-axis region thereof, and an image-side surface of the sixth lens element has at least one critical point in an off-axis region thereof.
23. The photographing system of claim 16 , wherein the image-side surface of the third lens element has at least one convex shape in an off-axis region thereof.
24. The photographing system of claim 16 , wherein the focal length of the second lens element is f2, the focal length of the third lens element is f3, the focal length of the fourth lens element is f4, the focal length of the fifth lens element is f5, the focal length of the sixth lens element is f6, a focal length of the seventh lens element is f7, the focal length of the x-th lens element is fx, and the following condition is satisfied:
| f 7 |<|fx |, wherein x= 2, 3, 4, 5, 6.
25. An image capturing unit, comprising:
the photographing system of claim 16 ; and
an image sensor disposed on an image surface of the photographing system.
26. An electronic device, comprising:
the image capturing unit of claim 25 .