Patent ID: 7394107

Claim:
A surface light source device comprising: at least one primary light source; a light guide plate having two major faces to provide an emission face, a back face and an incidence end face for introducing light supplied by said primary light source; and a direction modifying member disposed along said emission face, wherein said back face is provided with a great number of projection-like micro-reflectors for direction-conversion of light, each of which has a guiding portion and a conversion output portion that includes a ridge portion and a pair of first and second reflection surfaces formed on both sides of the ridge portion respectively as to be inclined with respect to a general plane representative of said back face, said ridge portion and said first and second reflection surfaces forming a valley in each of said micro-reflectors, said valley getting narrower and shallower as being distant from the guiding portion so that an inner input light reaching the valley via the guiding portion is reflected by one of the first and second reflection surfaces and is further reflected by the other of the first and second reflection surfaces as to produce an inner output light having a main propagation direction that is inclined with respect to a frontal direction in a plane perpendicular to said incidence end face so as to get remote from said incidence end face, and said direction modifying member receives the inner output light emitted from said emission face as an input and provides an output light that is approximately directed to the frontal direction in a plane perpendicular to said incidence end face.