Light beam scanning apparatus

A light beam scanning apparatus comprising: a plurality of light beam emitting devices for outputting light beams; a beam scanner for reflecting the light beams output from said light beam emitting devices towards a to-be-scanned surface to scan the to-be-scanned surface by use of the light beams in a main scanning direction; a beam position detector for detecting the light beam scanned on the to-moved surface by said beam scanner and generating an analog signal which is continuously changed with a variation in the passage position in a sub-scanning direction perpendicular to the main scanning direction of the light beam; a first target light detecting member having a first passage target and disposed separately from said beam position detector in the main scanning direction; a second target light detecting member having a second passage target separated from the first passage target in the sub-scanning direction by a distance corresponding to preset resolution; light beam passage position changing means for changing the passage position of at least one of the plurality of light beams; and a controller for controlling the relation of the, respective passage positions of the plurality of light beams to a preset relation by use of said light beam passage position changing means based on the outputs of said beam position detector respectively obtained when the light beam has passed through the first and second passage targets.

A light beam scanning apparatus comprising: a plurality of light beam emitting devices for outputting light beams; a beam scanner for reflecting a plurality of light beams output from said plurality of light beam emitting devices toward a to-moved surface to scan the to- be-scanned surface by use of the plurality of light beams; a beam position detector for detecting the light beam scanned across the to-be-scanned surface and generating an analog signal which is continuously changed with a variation in the passage position in a sub-scanning direction perpendicular to the main scanning direction of the light beam; a first target beam sensing member located away from the beam position detector and having a first passage target; a second target beam sensing member having a second passage target which is located away from the first passage target in the sub-scanning direction by a distance corresponding to a predetermined resolution; light beam passage position changing means for changing a passage position of at least one of said plurality of light beams; and a controller including, first means for controlling the light beam passage position changing means such that the light beam passes the first passage target, and for receiving a first sensing output produced from the beam position detector; second means for controlling the light beam passage position changing means such that the light beam passes the second passage target, and for receiving a second sensing output produced from the beam position detector; and third means for controlling the light beam passage position changing means on the basis of the first and second sensing outputs received by the first and second means while sensing the scan position relationship of the light beams by use of said beam position detector, such that said plurality of light beams satisfy a predetermined scan position relationship.