Abstract: A lens assembly includes a first lens including a first convex surface facing the object side, a first concave surface with an aperture stop facing the image side; a second lens including a second convex surface facing the object side and a second concave surface facing the image side; a first lens further including. Defining that f, f1, f2 are a focal length of the lens assembly, the first lens, and the second lens; D is a distance between the first lens and the second lens; TTL is a total track length; R1 is a radius of the first convex surface; R2 is a radius of the first concave surface; R3 and R4 are respectively radius of the second convex surface and the second concave surface; and ? is the image circle; the following conditions are satisfied: 0.01<|f/f2|<0.2; 0.1<R1/f1<0.5; 0.8<f1/TTL<1.1; 0.2<D/f<0.5; 0.3<R2/?<0.7; and 0.03<(R3?R4)/(R3+R4)<0.3.