A surface light source device includes a light guide plate which guides
light upward and downward, a light quantity adjustment unit which is
provided on at least one of top and bottom surfaces of the light guide
plate and adjusts the quantity of light above the light guide plate to be
different from that below the light guide plate, an emitting device which
is provided to at least one side of the light guide plate, and diffusion
plates which are respectively installed at the top and bottom surfaces of
the light guide plate. By adjusting the quantities of light radiated above
and below the light guide plate, the brightness of an image can be easily
adjusted.
