A display device includes a panel assembly, a backlight unit supplying light to the panel assembly, a first photosensor, a second photosensor, a sensing signal processor and a signal controller. The first photosensor is supplied with ambient light and light from the backlight unit to generate a first sensing signal. The second photosensor is blocked from the ambient light and receives the light from the backlight unit to generate a second sensing signal. The sensing signal processor receives the first and the second sensing signals from the first and the second photosensors for processing. The signal controller determines a sensing state responsive to processed first and second sensing signals from the sensing signal processor and performing a predetermined control operation responsive to the sensing state.