Patent ID: 6144680
Filing Date: 2000-11-07
Classification: H01S,H04N

Abstract:
A laser driving apparatus for driving a plurality of laser beam sources, comprising:a plurality of laser beam sources selectively emitting laser beams;a photodetector for producing a detection signal; indicative of an amount of light of the laser beams emitted from said plurality of laser beam sources;a plurality of current sources each for providing a level of current responsive to a control signal;a plurality of switches each selectively connecting one of said plurality of laser beam sources to a respective one of said plurality of current sources;a plurality of control means each for controlling a respective one of said plurality of laser beam sources by comparing the detection signal output by said photodetector with a reference signal and outputting the control signal to a respective one of said plurality of current sources, the control signal being indicative of a difference in magnitude between the detection signal and the reference signal;a plurality of sample-and-hold circuits each respectively interposed between said photodetector and one of said plurality of control means; andtiming adjustment means for outputting a plurality of timing signals of a first type for controlling said plurality of switches and a plurality of timing signals of a second type for controlling said plurality of sample-and-hold circuits,wherein said timing adjustment means outputs the plurality of timing signals of the first type for time-divisionally turning on said plurality of switches and sequentially making said plurality of laser beam sources emit the laser beams one by one,said timing adjustment means outputs the plurality of timing signals of the second type making each of said plurality of sample-and-hold circuits sample while a corresponding one of said plurality of switches is on, andsaid timing adjustment means outputs the plurality of timing signals of the second type making each of said plurality of sample-and-hold circuits sample while any one of said switches which are turned on before the corresponding switch is on.