Patent ID: 7492346

Claim:
A surface lighting device having a light source and a light-guide-member, said light-guide-member comprising: an incident plane for receiving light emitted from said light source and for producing incident light; a light-guiding-section for receiving said incident light and for producing guided light; and a light-emitting-section for receiving said guided light and for producing emitted light, wherein a length of shorter side of said light-guiding-section is not more than 8 mm, an area of said light-emitting-section is not less than 500 mm 2 , a ratio of minimum luminance vs. maximum luminance of said light-emitting-section is not less than 0.3, an average luminance of said light-emitting-section ranges from 1 cd/m 2 to 200 cd/m 2 , and a luminance change amount per unit length is not more than (average luminance)×100 cd/m 3 .