Patent ID: 7154525

Claim:
A focus adjustment method for an optical writing unit extending from a first end to a second end transversely across a surface of an image-carrying member, said focus adjustment method comprising: a pattern image forming process utilizing said optical writing unit to form a test pattern by projecting light modulated by image data of the test pattern from an array of multiple light-emitting elements corresponding to pixels arranged along the main scanning direction over an image forming area onto said surface of said image-carrying member, converting an electrostatic latent image formed on said surface of said image-carrying member into a visible toner image, and transferring said visible toner image from said surface of said image-carrying member onto a printing medium, said test pattern including; uninterrupted multiple pattern elements disposed generally all along said image forming area in a main scanning direction, said multiple pattern elements being of gradually varying density levels corresponding to different amounts of adjustment; and adjustment quantity information showing the amount of adjustment corresponding to the density levels of said multiple pattern elements; and a position adjustment process for separately adjusting the position of said ends of said optical writing unit in such a manner that said optical writing unit is positioned at a proper distance from, and parallel to, said surface of said image-carrying member based on density levels of end portions of each of said multiple pattern elements of said test pattern formed on said printing medium and based upon said adjustment quantity information.