Patent ID: 7466501

Claim:
A fixed-focus lens, comprising: a first lens group, located between an object side and an image side, having a negative refractive power, and comprising at least one aspheric lens; a second lens group, disposed between the first lens group and the image side, having a positive refractive power, and comprising a lens; and a third lens group, disposed between the second lens group and the image side, having a positive refractive power, and comprising a triple cemented lens, wherein an effective focal length of the fixed-focus lens is f, an effective focal length of the first lens group is f 1 , an effective focal length of the second lens group is f 2 , an effective focal length of the third lens group is f 3 , an axial distance between the first lens group and the second lens group is d, and the fixed-focus lens satisfies: 2.5<<|f 1 /f|<4.5, 7.5<f 2 /f<10, 4.5<f 3 /f<8.5, and 13<d/f<14.