Patent ID: 8379681

Claim:
A laser diode driving device for driving laser diodes with driving currents obtained by adding switch currents to corresponding bias currents less than or equal to threshold currents of the laser diodes and for controlling the driving currents to adjust light intensities of the laser diodes, the device comprising: a common switch current generating circuit configured to generate a common switch current according to an input signal; switch current generating circuits provided for the corresponding laser diodes and configured to generate the switch currents based on the common switch current and according to input signals; switches configured to control the output of the switch currents to the corresponding laser diodes according to input signals; bias current generating circuits configured to generate the bias currents and output the generated bias currents to the corresponding laser diodes; and a control unit configured to detect the light intensities of the respective laser diodes and to control the common switch current generating circuit, the switch current generating circuits, and the switches to adjust the light intensities of the respective laser diodes, wherein the common switch current from the common switch current generating circuit is supplied to plural ones of the switch current generating circuits, and each of the plural ones of the switch current generating circuits generates a switch current based on the common switch current, and wherein the switch currents generated by the plural ones of the switch current generating circuits are proportional to the common switch current.