Patent ID: 8192033
Filing Date: 2012-06-05
Classification: G02B,G03B

Abstract:
1. A fixed-focus lens adapted to be disposed between an object side and an image side, the fixed-focus lens comprising: a reflector disposed in a light path between the object side and the image side; a curved reflector disposed in the light path between the reflector and the image side; a first lens group disposed in the light path between the curved reflector and the image side and comprising a first lens and a second lens arranged in sequence from the object side to the image side, wherein each of the first lens and the second lens is an aspheric lens; a second lens group disposed in the light path between the first lens group and the image side and comprising a spherical lens and an aspheric lens, wherein the aspheric lens of the second lens group is closest to the image side in the second lens group; and a dichroic minor, disposed in the light path between the first lens group and the second lens group and adapted to transmit a non-visible light from the first lens group to the second lens group, wherein an effective focal length of the fixed-focus lens is f, an effective focal length of the second lens group is f2, a clear aperture of the aspheric lens of the second lens group is D, and the fixed-focus lens satisfies at least one of following conditions: 0.04<f/f2<0.078 and 0.05<f/D<0.18.