US Patent 7354185 Light guiding plate and backlight module using the same

A back light module (3) includes a light guide plate (31) and a light source (30). The light guide plate includes a light incident surface (311), a light emitting surface (313), and a bottom surface (312) opposite to the light emitting surface. The bottom surface has a plurality of dissymmetric protrusions (314). The dissymmetric protrusions defines an angle α between a first side (3142) thereof and a reference line of a length of the light guiding plate, and an angle β between a second side (3144) thereof and the reference line. The light guiding plate has high brightness and uniformity.