Light beam scanning apparatus and image forming apparatus

A light beam scanning apparatus comprising:

• plural light beam generating means for generating a light beam;
• plural optical means, provided to each of said plural light beam generating means respectively, for combining the plural light beams;
• single scanning means for reflecting the light beams combined by said combining means toward a surface to be scanned and causing said light beams to scan said surface in a main scanning direction;
• light beam power sensing means for using a first light-receiving element to sense the power of each of the light beams caused by said scanning means to scan said surface;
• and
• light beam power control means for controlling each of said plural light beam generating means on the basis of the result of sensing at said light beam power sensing means so that the difference between the power of one of said light beams scanning said surface and the power of each of the remaining three may be equal to or less than a specific value.

A light beam scanning apparatus comprising:

• plural light beam generating means for generating a light beam;
• plural optical means, provided to each of said plural light beam generating means respectively, for combining the plural light beams;
• single scanning means for reflecting the light beams combined by said combining means toward a surface to be scanned and causing said light beams to scan said surface in a main scanning direction;
• first light beam position sensing means for using light-receiving elements arranged linearly at intervals corresponding to a first resolution in the sub-scanning direction perpendicular to said main scanning direction to sense the light beams caused by said scanning means to scan said surface;
• second light beam position sensing means for using light-receiving elements arranged linearly at intervals corresponding to a second resolution differing from said first resolution in said sub-scanning direction to sense the light beams caused by said scanning means to scan said surface;
• and
• light beam passing position control means for controlling the light beams caused to scan by said scanning means on the basis of the results of sensing at said first and second light beam position sensing means so that each of the passing positions of the light beams on said surface may become a proper position according to said first or second resolution.