Patent ID: 8036254
Filing Date: 2011-10-11
Classification: G11B,H01S

Abstract:
1. A semiconductor laser driving circuit, comprising: a voltage source that supplies an anode voltage to an anode of a semiconductor laser; a drive portion that is connected to a cathode of the semiconductor laser and that changes an amount of current that is drawn in from the semiconductor laser in accordance with an emission strength of the semiconductor laser, so as to control, via feedback, an optical output of the semiconductor laser; a measurement portion that is connected to the cathode of the semiconductor laser and that measures a cathode voltage of the semiconductor laser; and a voltage control portion that is connected to the voltage source, and that, when the drive portion changes the amount of current that is drawn in from the semiconductor laser in accordance with the emission strength of the semiconductor laser, controls the anode voltage supplied by the voltage source such that the cathode voltage of the semiconductor laser is at least a first level, which is a voltage level of at least a minimum voltage at which an operation of the drive portion is guaranteed, wherein the anode voltage is equal to or greater than a withstand voltage of the drive portion and a withstand voltage of the measurement portion, when the drive portion controls, via feedback, the optical output of the semiconductor laser, wherein, during a predetermined period in which the semiconductor laser emits light at a peak power, the measurement portion measures a bottom value of the cathode voltage of the semiconductor laser, and wherein the voltage control portion sets the bottom value of the cathode voltage of the semiconductor laser measured by the measurement portion as the first level, and controls the anode voltage supplied by the voltage source.