| 摘要 |
PROBLEM TO BE SOLVED: To calibrate a toner density sensor efficiently with high precision and to eliminate the need for a dedicated driving source for putting the sensor opposingly to a reference patch provided for a body to be measured. SOLUTION: As a secondary transfer roller 8a contacts and leaves an intermediate transfer belt 7a, the toner density sensor 17 moves to face selectively the secondary transfer roller 8a and one of reference patches 19 provided at specific places not on the secondary transfer roller 8. Consequently, the timing of the movement of the toner density sensor 17 is properly set. The density on the secondary transfer roller 8a is read more accurately and the toner density sensor 17 can be calibrated efficiently with high precision. Further, the driving means for allowing the secondary transfer roller 8a to contact and leave the intermediate transfer belt is used even as the driving means for moving the toner density sensor 17 so that the need for the dedicated driving means for moving the toner density sensor 17 is eliminated. |
