Patent ID: 7656398

Claim:
A surface light source device comprising: light source driving means for driving light sources on a light emission block basis, a light exit area being sectioned into two or more light emission blocks; light quantity detecting means for detecting light quantities on the basis of output light beams that are led out from the two or more light emission blocks; light transmitting means for transmitting output light beams of the respective light emission blocks to the light quantity detecting means; and drive control means for adjusting emission light quantities of the light sources corresponding to the respective light emission blocks on the basis of light quantities that are detected during lighting periods set in time-series order, each of the lighting periods in which the light source for only predetermined light emission blocks are lit up are subjected to light quantity detection by the light quantity detecting means, wherein the light quantity detecting means detects the light quantities of the output light beam in series corresponding to the lighting period, wherein the output light beams are led out from the respective light emission blocks and are transmitted by the light transmitting means.