| 摘要 |
PURPOSE:To accurately measure the density of a gradation correction pattern even though the gradation correction pattern forming area of an intermediate transfer body is damaged because of secular change by detecting the surface density of the intermediate transfer body at plural positions where the gradation correction pattern is formed and setting the detected result as a white reference for each gradation correction pattern. CONSTITUTION:Both output from a density sensor 32 and output from a 2nd density sensor 42 are inputted in the A/D conversion port of a CPU 43, and the CPU 43 can always refer to the output from the sensors 32 and 42. In the case of detecting the density of the gradation correction pattern, the CPU 43 reads the output from the sensor 32 in timing when the gradation correction pattern formed on the intermediate transfer body 1 reaches the position of the sensor 32. Hereafter, the density of one of the gradation correction patterns is detected in a specified cycle specified times, and the result of read is averaged and stored in a RAM 45 via the CPU 43. Then, it is set as the white reference for each gradation correction pattern. |
