An light device, includes a plurality of first light cells arranged axisymmetrically about an axis; a plurality of second light cells arranged axisymmetrically around the axis; and a controller coupled to a brightness adjust unit, and determines whether to activate the first light cells and second light cells according to a brightness adjust value of the brightness adjust unit, wherein the average distance between the first light cells and the axis is shorter than the average distance between the second light cells and the axis.