Patent ID: 7445370

Claim:
A surface light source device comprising a point-like light source and a light flux control member which receives light from said point-like light source and has an emission face from which said light is emitted, wherein said light flux control member has a back face opposite to said emission face which is provided with a recess corresponding to said point-like light source, said recess having a concave section meeting a convex section and being configured so as to satisfy the following Conditions 1 and 2 for at least light which is emitted toward the recess within a half-intensity-angular-range from said point-like light source; {Condition 1: Relation θ 5 /θ 1 >1 is satisfied except for light emitted toward the recess within an angular-neighborhood of a normal direction with respect to said emission face; Condition 2; Value of θ 5 /θ 1 falls gradually according to increasing of θ 1 ; (where θ 1 is an emission angle of any light at being emitted from said point-like light source and θ 5 is an emission angle of that light at being then emitted from said emission face)}.