Image lens with high resolution, low chromatic aberration, and long flange back distance
An image lens includes a first lens and a second lens. The first lens includes a first surface and a second surface. The second lens includes a third surface and a fourth surface. The image lens satisfies: FB/TTL>0.38; R 11 /F 1 >2.23; Z/Y>0.11; Z/T<0.42; R 23 /F 2 <R 12 /F 2 <R 24 /F 2 . FB is a distance between the fourth surface and an image plane, TTL is a total length of the image lens, Z is a distance from a central point of the fourth surface to an outer edge of the fourth surface along an optical axis of the image lens, Y is a distance from the central point of the fourth surface to the edge of the fourth surface along a direction perpendicular to the optical axis, T is a thickness of the second lens, R 23 , R 24 , R 11 and R 12 are curvature radiuses of the third, fourth, first and second surfaces, F 2 is a focal length of the second lens.
1. An image lens for imaging an object on an image plane, in the order from the object side to the image side thereof, comprising:
a first lens having positive refraction power and comprising a first surface facing the object side and a second surface facing the image side; and
a second lens having negative refraction power and comprising a third surface facing the object side and a fourth surface facing the image side;
wherein the image lens satisfies the following formulas:
FB/TTL>0.38; (1)
R 11/ F 1>2.23; (2)
Z/Y> 0.11; (3)
Z/T< 0.42; (4)
R 23/ F 2< R 12/ F 2< R 24/ F 2; (5)
wherein FB is a distance between the fourth surface and the image plane along an optical axis of the image lens, TTL is a total length of the image lens, Z is a distance from a central point of the fourth surface to an outer edge of the fourth surface along the optical axis of the image lens, Y is a distance from the central point of the fourth surface to the outer edge of the fourth surface along a direction perpendicular to the optical axis of the image lens, T is a thickness of the second lens on the optical axis, R 23 is a curvature radius of the third surface, R 24 is a curvature radius of the fourth surface, R 11 is a curvature radius of the first surface; R 12 is a curvature radius of the second surface, and F 2 is a focal length of the second lens.
2. The image lens as claimed in claim 1 , wherein the image lens further satisfies the formulas:
R 12/ F 2<0.36; (6)
R 23/ F 2<0.27; (7)
R 24/ F 2<0.46 (8).
3. The image lens as claimed in claim 1 , wherein the image lens further satisfies the formulas:
Vd 1>53; and (9)
Vd 2<33; (10)
wherein Vd 1 is the Abbe number of the first lens, and Vd 2 is the Abbe number of the second lens.
4. The image lens as claimed in claim 1 , wherein the first lens and the second lens are aspherical lenses.
5. The image lens as claimed in claim 4 , wherein the first surface is a convex surface facing the object side, the second surface is a convex surface facing the image side, the third surface is a concave surface facing the object side, and the fourth surface is a convex surface facing the image side.
6. The image lens as claimed in claim 1 , wherein the image lens further comprises an aperture stop positioned at the objected side of the first lens.
7. The image lens as claimed in claim 1 , further comprising a filter glass, wherein the filter glass is positioned between the second lens and the image plane.
8. The image lens as claimed in claim 7 , further comprising a cover glass, wherein the cover glass is positioned between the filter glass and the image plane.
9. The image lens as claimed in claim 1 , wherein the central point is positioned at a centre of a circle formed by the outer edge of the fourth surface.