US Patent 7809037 Laser array circuit

A laser array circuit decreases the size of a circuit pattern. A laser-diode (LD) driving switching element with a low on resistance is used in common with and switches conduction and non-conduction of a large current to each of a plurality of charge capacitors and charge switching elements that accumulate charge in the charge capacitors in respective drive circuits. An LD array and the LD driving switching element are closely located on a light-emitting board. By laying out the LD array and charge capacitors considering only the positional relationship therebetween, the size of a circuit pattern including LDs and the charge capacitors can be decreased.