A self light emitting device having a function of correcting drops in brightness
in self light emitting elements in a pixel portion, and capable of displaying a
uniform image without brightness irregularities, is provided. A specific test pattern
is displayed when an electric power source is connected, brightnesses are detected
by photoelectric conversion elements arranged in each pixel, and then stored in
a memory circuit. A correction circuit then corrects a first image signal based
on portions which are insufficient from standard brightnesses (brightnesses of
normal self light emitting elements at the same gray stale, stored in advance),
and a second image signal is obtained. Display of an image in a display device
is performed in accordance with the second image signal.
