| 摘要 |
PURPOSE:To attain the miniaturization and reduction in cost of a developing device by receiving reflected light from a two-component developer with a light receiving element for detection and obtaining a toner concentration that the temp. characteristic of the light emission output of a light emitting element is corrected, unless a light receiving element for reference is provided on a toner concentration detecting means. CONSTITUTION:A temp. detecting device 13 is installed to detect the temp. of environment that the main bodies of the developing units 3M-3B of each color, having the installation of the toner concentration detecting means are placed and a toner concentration controller corrects the temp. of the detection output of the light receiving element through the use of the detected temp., based on a change in the temp. of the detection output of the light receiving element by the temp. characteristic of the light emission output of the light emitting element is corrected. Thus, the toner concentration that the temp. characteristic of the light emission output of the light emitting element can be obtained, without providing the light receiving for reference, and the developing units 3M-3B can be miniaturized and reduced in cost. |
