Patent ID: 6249307
Filing Date: 2001-06-19
Classification: B41J,G02B

Abstract:
An image forming apparatus which scans a plurality of optical beams over an image bearer to form an image on the image bearer by exposure, said apparatus comprising:a plurality of optical beam generating means for outputting the optical beams;scanning means for scanning the optical beams over the image bearer by reflecting the optical beams emitted from the optical beam generating means toward the image bearer;optical beam sensing means, arranged near a beam scanned region of the image bearer, for outputting a sensing signal corresponding to timings at which the scanning means scans the optical beams in a scanning direction, a sensing signal corresponding to power of each of the optical beams, and a sensing signal corresponding to a position determined in a direction orthogonal to the scanning direction;changing means for changing power of each of the optical beams emitted from the optical beam generating means, independently of one another;first setting means, operating when the timings at which the scanning means scans the optical beams in the scanning direction and the position determined in the direction orthogonal to the scanning direction are adjusted, for causing the changing means to change the power of each of the optical beams output from the optical beam generating means independently of one another on the basis of the sensing signal corresponding to the power of each of the optical beams from the optical beam sensing means, and for setting the power of each of the optical beams incident on the optical beam sensing means to be first power, which is constant without reference to a characteristic change said image bearer may undergo with time; andsecond setting means, operating when the image is formed on the image bearer, for causing the changing means to change the power of each of the optical beams output from the optical beam generating means independently of one another on the basis of the sensing signal corresponding to the power of each of the optical beams from the optical beam sensing means, and for setting the power of each of the optical beams incident on the optical beam sensing means to be second power, which is greater than the first power and which gradually increases therefrom in accordance with the characteristic change said image bearer may undergo with time.