Patent ID: 7701480

Claim:
A circuit for driving a plurality of light emitting units, the circuit comprising: an overshoot-current generating unit that generates an overshoot current; and a current adding unit that biases a light emitting current that is determined based on an amount of light emitted from each of the light emitting units with the overshoot current, and supplies resultant current to each of the light emitting units, wherein the light emitting units and the driving circuit are accommodated in separate packages, the overshoot-current generating unit includes a resistance-capacitance circuit, which includes a resistor and a capacitor, that generates the overshoot current, and the current adding unit determines a resistance and capacitance of the resistance-capacitance circuit so that rise characteristics that are characteristic of light emitted from each of the light emitting units and depends on a difference in a time constant, the time constant being obtained based on a resistance of each of the light emitting units, a capacitance of each of the packages, and a coupling capacitance of each of wires, is equal among the light emitting units.