Patent ID: 7762705

Claim:
A surface light source device comprising: a housing having an opening portion on at least one face; a light source held by one face of the housing opposing said opening portion, the light source being a point light source; and a light guiding plate arranged at a position so as to cover said opening portion and said light source, and including an emission surface to emit light and a reflection and emission surface opposing said emission surface, wherein said light guiding plate includes: a first cylindrical recess provided at a position corresponding to said light source in said reflection and emission surface for storing a part of said light source; and a second cylindrical recess provided in said light emission surface opposite to said first cylindrical recess; and the surface light source device further comprises light quantity adjusting means provided at a bottom part of said second recess for adjusting light from said light source, wherein said light quantity adjusting means includes means for reflecting a portion of light from said light source and for transmitting at least 2% of light transmitted by said light source.