Patent ID: 7593028

Claim:
An optical scanning method for writing an image in an image carrying member by using a black writing illuminant and a color writing illuminant wherein said black writing illuminant writes said image at a plurality of record densities and said color writing illuminant writes said image at a single predetermined record density, the method comprising the steps of: adjusting a beam pitch position for a full-color image with respect to a main scanning direction and a sub-scanning direction by changing a beam pitch position of said black writing illuminant in accordance with one of the plurality of record densities such that the beam pitch among black and the other colors to be equal interval; determining whether the beam pitch position of said black writing illuminant is located at said adjusted beam pitch position when writing said full-color image; switching the beam pitch position of said black writing illuminant in accordance with said adjusted beam pitch position when the beam pitch position of said black writing illuminant is determined to be different from said adjusted beam pitch position; and writing said full-color image at said adjusted beam pitch position in said image carrying member.