| 摘要 |
PROBLEM TO BE SOLVED: To perform density control with high reliability by accurately grasping whether a movable density measuring means is properly positioned at a normal measuring position or not by detecting reflected light quantity for specified emitted light quantity on an image carrier and comparing a detected value with a threshold value using the density measuring means. SOLUTION: A toner image formed on a transfer drum 6, namely, a patch is irradiated with the light of the specified emitted light quantity by a movable density sensor 18 and an output signal in accordance with the reflected light quantity is transmitted to a CPU 22. In the case that the reflected light quantity is not varied in proportion to the emitted light quantity of a light emitting light source 24, and in the case that the reflected light quantity deviates from a previously set range, the density sensor 18 is judged not to be at the normal measuring position for the drum 6. Thus, a D/A setting part 32 previously sets the output level of the case that the density sensor 18 is not at the normal position as the threshold value, so that a sensor position detecting part 33 detects whether the density sensor 18 is at the normal measuring position or not. |
