Optical imaging lens
Present embodiments provide for an optical imaging lens. The optical imaging lens comprises a first lens element, a second lens element, a third lens element and a fourth lens element positioned in an order from an object side to an image side. Through controlling the convex or concave shape of the surfaces of the lens elements and designing parameters satisfying at least one inequality, the optical imaging lens shows better optical characteristics and enlarge field angle while the total length of the optical imaging lens is shortened.
1. An optical imaging lens, sequentially from an object side to an image side along an optical axis, comprising first, second, third and fourth lens elements, each of said first, second, third and fourth lens elements having refracting power, an object-side surface facing toward said object side and an image-side surface facing toward said image side, wherein:
said object-side surface of said first lens element comprises a convex portion in a vicinity of the optical axis, and said image-side surface of said first lens element comprises a concave portion in a vicinity of a periphery of said first lens element;
said second lens element has positive refracting power, and said image-side surface of said second lens element comprises a convex portion in a vicinity of the optical axis;
said object-side surface of said third lens element comprises a convex portion in a vicinity of the optical axis;
said object-side surface of said fourth lens element comprises a concave portion in a vicinity of a periphery of said fourth lens element, and said image-side surface of said fourth lens element comprises a convex portion in a vicinity of a periphery of said fourth lens element;
said optical imaging lens comprises no other lenses having refracting power beyond said first, second, third and fourth lens elements;
a distance between said object-side surface of said first lens element and an image plane along the optical axis is represented by TTL, a central thickness of said second lens element along the optical axis is represented by T2, an air gap between said third lens element and said fourth lens element along the optical axis is represented by G34, and TTL, T2 and G34 satisfy the equation: TTL/(T2+G34)≦4.5, and TTL and G34 satisfy the equation: TTL/G34≦13.7.
2. The optical imaging lens according to claim 1 , wherein an air gap between said first lens element and said second lens element along the optical axis is represented by G12, and G12 and T2 satisfy the equation: G12/T2≧1.3.
3. The optical imaging lens according to claim 1 , wherein an air gap between said first lens element and said second lens element along the optical axis is represented by G12, and TTL and G12 satisfy the equation: TTL/G12≦5.4.
4. The optical imaging lens according to claim 1 , wherein a sum of the central thicknesses of all lens elements is represented by ALT, an air gap between said first lens element and said second lens element along the optical axis is represented by G12, and ALT, G12, and G34 satisfy the equation: ALT/(G12+G34)≦2.
5. The optical imaging lens according to claim 1 , wherein an air gap between said first lens element and said second lens element along the optical axis is represented by G12, and wherein TTL, G12 and G34 satisfy the equation: TTL/(G12+G34)≦4.
6. The optical imaging lens according to claim 1 , wherein a sum of the central thicknesses of all lens elements is represented by ALT, an air gap between said first lens element and said second lens element along the optical axis is represented by G12, and ALT and G12 satisfy the equation: ALT/G12≦2.6.
7. The optical imaging lens according to claim 1 , wherein a central thickness of said third lens element along the optical axis is represented by T3, and T2, T3 and G34 satisfy the equation: (T2+T3)/G34≦5.
8. The optical imaging lens according to claim 1 , wherein an air gap between said first lens element and said second lens element along the optical axis is represented by G12, a central thickness of said third lens element along the optical axis is represented by T3, and G12, T3 and T2 satisfy the equation: (G12+T3)/T2≧2.3.
9. The optical imaging lens according to claim 1 , wherein a sum of all air gaps between all lens elements along the optical axis is represented by Gaa, and Gaa and T2 satisfy the equation: Gaa/T2≧2.2.
10. The optical imaging lens according to claim 1 , wherein a distance from said object-side surface of said first lens element to said image-side surface of said fourth lens element along the optical axis is represented by TL, an air gap between said first lens element and said second lens element along the optical axis is represented by G12, and TL, G12 and G34 satisfy the equation: TL/(G12+G34)≦3.2.
11. The optical imaging lens according to claim 1 , wherein an air gap between said first lens element and said second lens element along the optical axis is represented by G12, and G12, G34 and T2 satisfy the equation: (G12+G34)/T2≧1.9.
12. The optical imaging lens according to claim 1 , wherein a central thickness of said third lens element along the optical axis is represented by T3, and T3 and G34 satisfy the equation: T3/G34≦2.5.
13. The optical imaging lens according to claim 1 , wherein an air gap between said second lens element and said third lens element along the optical axis is represented by G23, and G23, T2 and G34 satisfy the equation: (T2+G23)/G34≦3.5.
14. The optical imaging lens according to claim 1 , wherein a sum of the central thicknesses of all lens elements is represented by ALT, and ALT and G34 satisfy the equation: ALT/G34≦6.9.
15. The optical imaging lens according to claim 1 , wherein a distance from said object-side surface of said first lens element to said image-side surface of said fourth lens element along the optical axis is represented by TL, and TL and G34 satisfy the equation: TL/G34≦11.
16. The optical imaging lens according to claim 1 , wherein a central thickness of said first lens element along the optical axis is represented by T1, and T2, T1 and G34 satisfy the equation: (T2+T1)/G34≦3.5.
17. The optical imaging lens according to claim 1 , a central thickness of said fourth lens element along the optical axis is represented by T4, and T4, T2 and G34 satisfy the equation: (T4+T2)/G34≦3.5.
18. The optical imaging lens according to claim 1 , wherein an effective focal length of said optical imaging lens is represented by EFL, and EFL and G34 satisfy the equation: EFL/G34≦2.6.
19. The optical imaging lens according to claim 1 , wherein a central thickness of said fourth lens element along the optical axis is represented by T4, a central thickness of said third lens element along the optical axis is represented by T3, and T4, T3 and G34 satisfy the equation: (T4+T3)/G34≦3.2.