Patent ID: 8305412

Claim:
An image forming apparatus comprising: a light source that outputs a plurality of laser beams; a splitting unit that splits each of the laser beams into a first laser beam that is used for light intensity control and a second laser beam that is used to scan a photosensitive element; a light-intensity-signal output unit that outputs for each of the first laser beams a corresponding light intensity signal that is indicative of the light intensity thereof; and a control unit that adjusts the light intensity of each of the laser beams to a target light intensity by referring to the light intensity signal, wherein the control unit includes a common-control-value calculating unit that calculates a common control value that is used for light intensity control of every laser beam; a correction-value calculating unit that calculates a correction value for each of the laser beams, wherein the correction value is used to correct the common control value; and a threshold calculating unit that calculates a threshold of each of the laser beams, wherein the threshold corresponds to a value of current at which oscillation of the laser beam starts, the correction-value calculating unit calculates the correction value so that, when the laser beam is driven by a first control value, the light intensity of the laser beam is equal to the target light intensity, wherein the first control value is a value calculated by correcting the common control value using the correction value to obtain a corrected control value and adding the threshold to the corrected control value, and the threshold calculating unit calculates the threshold so that, when the laser beam is driven by a second control value, the light intensity of the laser beam is equal to the target light intensity multiplied by a predetermined factor, wherein the second control value is a value calculated by correcting the common control value using the correction value to obtain the corrected control value, multiplying the corrected control value by the predetermined factor to obtain a multiplied control value, and adding the threshold to the multiplied control value.