| 摘要 |
PROBLEM TO BE SOLVED: To measure concentration with less errors, for enabling a more accurate feedback to an image forming condition by adopting such a constitution that a latent image formed for measuring the concn. of toner has an inclination gentler than that of the latent image at the time of executing normal printing, so as to make changes in the concn. and line width obtained when the image forming condition is varied great. SOLUTION: A developing bias voltage 36 as a reference value 35 previously set by a test, etc., is obtained from three kinds of toner image densities 34-a, 34-b and 34-c different in developing bias voltage, to be set as one at the time of forming an image. In the method of calculating a bias voltage correction value for correcting a process, the same sensor output as the reference value is obtained at a voltage lower than the developing bias voltage at the time of forming a toner image by about 20V, so that it is good that the developing bias voltage for an image forming operation is reduced by about 20V. |
