Patent ID: 8373935
Filing Date: 2013-02-12
Classification: G02B

Abstract:
1. A fixed-focus lens, disposed between an enlarged side and a reduced side, the fixed-focus lens comprising: a first lens group, comprising a first lens, wherein the first lens is an aspheric lens; and a second lens group, having a positive dioptre, disposed between the first lens group and the reduced side, the second lens group comprising a second lens, wherein the second lens is an aspheric lens, wherein an f-number of the fixed-focus lens is smaller than or equal to 2, the fixed-focus lens focuses by moving the first lens group and the second lens group, and the fixed-focus lens satisfies 0.1<|f/f1|<1, 0.2<|f/f2|<1.5, and 1.5<L/BEL<3.5, wherein f is a focal length of the fixed-focus lens, f1 is an effective focal length of the first lens group, f2 is an effective focal length of the second lens group, L is a total length of the fixed-focus lens, and BFL is a back focal length of the fixed-focus lens.