Abstract: A light emitting device includes at least one light emitting unit, a switching unit, a comparator unit, a charge storage unit and a sensing unit. The switching unit is electrically connected to the light emitting unit. The comparator unit is electrically connected to the switching unit. The charge storage unit is electrically connected to the comparator unit and stores an amount of electric charges. The sensing unit has a light sensing circuit and is electrically connected to the charge storage unit. The light sensing circuit senses a light intensity of the light emitting unit. The sensing unit adjusts the amount of the electric charges and a voltage corresponding to the amount of the electric charges according to the light intensity. The comparator unit compares the voltage with a threshold voltage. The switching unit controls the light emitting unit in accordance with the result of the comparison.

Abstract: A calibrating method of a light emitting device, which includes at least one light-emitting diode (LED) unit. The calibrating method includes the steps of inputting a brightness control signal to the LED unit, measuring a lighting brightness of the LED unit, and writing an initial relation of the brightness control signal and the lighting brightness into a memory unit. In addition, a light emitting device and a controlling method thereof are also disclosed.