| 摘要 |
PURPOSE:To make relation between density and the output value of an optical sensor linear where feedback control is easy by providing a means for logarithmically converting the output value of the optical sensor, and a means for setting a process control value according to the toner density value obtained by logarithmically converting the output value. CONSTITUTION:The density of a toner image A formed on a photosensitive body 4 on a specified condition is detected by the optical sensor 6. The value detected by the sensor 6 (sensor output value corresponding to toner density) is logarithmically converted and the process control value such as the electrostatic charging potential of the photosensitive body and the light quantity of a copying lamp is set according to the value (toner density value). Generally, exponential change is replaced with the linear change by logarithmic conversion. Therefore, by logarithmically converting the output value of the sensor 6 which is exponentially changed, the relation between the density and the sensor output value becomes linear and the succeeding process control processing is facilitated. |
