Patent ID: 6894740

Claim:
A surface light source device, comprising: a primary light source; a light guide plate supplied with light from said primary light source; and a light diffusion member, wherein said light guide plate has an emission face provided by a major face, a back face provided by another major face opposite with said emission face and an incidence face for being supplied with light from said primary light source, said back face being provided with a great number of projection-like micro-reflectors for light-travelling-direction-conversion, each of said micro-reflectors has a conversion-output-portion including a first inner-reflection face and a second inner-reflection face which provide a valley in said light guide plate and meet each other as to give a valley bottom of said valley, said valley being opened as to get deeper and wider toward a main light coming direction of an inner input light reaching the valley, thereby generating an inner output light reaching the valley, thereby generating an inner output light containing a first inner output light and a second inner output light from said inner input light reaching the valley, the first inner output light being produced through being inner-reflected by said first inner-reflection face and then by said second inner-reflection face, the second inner output light being produced through being inner-reflected by said second inner-reflection face and then by said first-inner reflection face, said first and second inner-reflection faces being inclined so that said first inner output light and said second inner output light are non-parallel and thereby said emission face provides a direction-split emission having two emission intensity peaks, said light diffusion member being disposed along said emission face in order to input said direction-split emission having the two intensity peaks thereto and to output an emission having a single emission intensity peak by dissolving said direction-split emission.