Patent ID: 7480320

Claim:
A semiconductor laser driving device which performs a driving control of a semiconductor laser to control current supplied to the laser so that a desired amount of emission light is obtained, said semiconductor laser driving device comprising: a first current generating unit generating a first current that is below an oscillation threshold current of the laser, and outputting the first current to the laser invariably; a second current generating unit generating a second current that is needed for light emission of the laser responsive to an input signal; a third current generating unit generating a third current that controls the laser such that a detected amount of emission light from the laser accords with a given value, and outputting the third current to the laser; an auxiliary current control unit causing the second current generating unit to generate a predetermined auxiliary current, the second current generating unit outputting a sum of the second current and the auxiliary current to the laser; and an initialization unit performing an initialization operation to detect luminescence characteristics of the laser, and outputting a signal, indicating a value of the second current derived from the detected luminescence characteristics, to the second current generating unit, wherein the third current generating unit controls the third current so that an amount of light outputted by the laser which receives a sum of the first current, the second current, the third current and the auxiliary current, accords with a predetermined amount.