Patent ID: 7750929

Claim:
An image forming apparatus comprising: an image bearing member; a charging unit configured to charge the image bearing member by applying charging bias to the image bearing member; an exposure unit configured to irradiate the image bearing member with a laser beam so as to form an electrostatic latent image on the image bearing member charged by the charging unit; a driving unit configured to supply a pulse signal to a light source so that the exposure unit emits the laser beam; a pattern forming unit configured to have the charging unit, the exposure unit and the driving unit form a plurality of latent image patterns of potential levels different from each other in order to control the density of a toner image to be formed on the image bearing member; a control unit configured to control the charging bias and developing bias to be kept constant and change a pulse width of the pulse signal when forming the plurality of latent image patterns in order to control a potential difference between the electrostatic latent image and the developing bias to be a predetermined value; a developing unit configured to apply the developing bias to a toner and develop the plurality of latent image patterns with the toner; a measuring unit configured to measure potentials of the plurality of latent image patterns; and a density detecting unit configured to detect the density of the plurality of predetermined toner patterns, wherein the control unit controls the pulse width of the pulse signal so that exposure areas formed with one pulse signal and adjacent to each other are overlapped when the plurality of latent image patterns are formed on the image bearing member, and wherein the control unit controls at least one of the charging bias and the developing bias based on a measurement result of the measuring unit and a detection result of the density detecting unit so that the potential difference between the electrostatic latent image and the developing bias is controlled to be predetermined value.