Electrophotographic image forming apparatus

An image forming apparatus, comprising:

• a light source constructed to output a light beam;
• a light amount control unit constructed to execute light amount control to make a light amount of the light beam output from the light source equal to a target light amount;
• a deflection unit constructed to deflect the light beam output from the light source and scan a surface of a scan target using the deflected light beam;
• a shading control unit constructed to control the light amount of the light beam output from the light source by controlling a driving current for the light source for each scanning position on the surface of the scan target;
• a correction unit constructed to correct the driving current using a correction amount corresponding to (i) a detected value of a first patch formed with a light amount obtained by the light amount control unit reducing the target light amount by a predetermined percentage, and (ii) a detected value of a second patch formed with a light amount obtained by the shading control unit reducing the target light amount by the predetermined percentage;
• and
• a correction coefficient determination unit that determines a correction coefficient that is used by the shading control unit for a degree of control for each scanning position in common, so that there is no difference between the detected value of the first patch formed with the light amount obtained by the light amount control unit reducing the target light amount by the predetermined percentage and the detected value of the second patch formed with the light amount obtained by the shading control unit reducing the target light amount by the predetermined percentage,
• wherein the correction unit corrects the driving current using the correction amount by multiplying the degree of control for each scanning position by the correction coefficient, and
• the shading control unit controls the driving current for the light source using the degree of control for each scanning position that has been corrected using the correction amount.