The invention provides a design method of a free-form surface reflector for an LED automobile rear
fog lamp. The design method comprises the following steps: initial conditions are set, and a target lighting region is uniformly divided; a
light source solid angle is divided, and a mapping relation is established according to the
energy conservation law; discrete point coordinates of the free-form surface reflector are calculated; and discrete ordinate points are fitted into a curved surface by utilizing mechanical
modeling software. According to the design method provided by the invention, the size of the free-form surface reflector is small, the glare effect is low as a light emitting surface of a
light source is vertically installed upwards, and meanwhile, the light distribution requirements of
national standard GB 11554-2008 for the LED automobile rear
fog lamp can be met. According to the technical scheme provided by the invention, the light emitting surface of the
light source emits lights upwards perpendicular to the
optical axis direction and the light is reflected by the free-form surface reflector, and finally, the light emerges onto a lighting surface; and the free-form surface reflector has the advantages of symmetry, simple design and high efficiency.