Patent ID: 8054541

Claim:
A fixed-focus lens, adapted to be disposed between a primary image side and a second image side and having an optical axis, the fixed-focus lens comprising: a first lens group disposed between the primary image side and the second image side and comprising an aspheric lens; a second lens group disposed in a light path between the primary image side and the first lens group and comprising a first lens, a second lens, and a third lens sequentially arranged from the primary image side to the second image side, wherein refractive powers of the first lens and the third lens are both positive, and each of the first lens, the second lens, and the third lens is a spherical lens; and a curved reflector disposed in a light path between the primary image side and the second image side, wherein a refractive power of the curved reflector is negative; wherein an image light beam transmitted from the primary image side and passing through the first lens group and the second lens group forms one of a butterfly spot and a trapezoid spot on a reference plane, and the reference plane is located between the first lens group and the curved reflector and perpendicular to a part of the optical axis between the first lens group and the curved reflector; wherein the image light beam forming the butterfly spot is compensated to form a rectangular spot after being reflected by the curved reflector, and the image light beam forming the trapezoid spot is compensated to form another rectangular spot after being reflected by the curved reflector.