| 摘要 |
PROBLEM TO BE SOLVED: To always obtain an appropriate registration and image density by reducing the soiling of a sensor for detecting the registration, density, etc., of an image. SOLUTION: This device is provided with a test pattern forming means for forming a test pattern image on each photoreceptor drum and optical sensors 8a to 8c that are sensors to detect the test pattern image transferred on an electrostatic transfer belt 1 from each photoreceptor drum and provided on a side of an electrostatic transfer belt 1 where the transfer material is carried. In this case, the test pattern image on the electrostatic transfer belt 1 is detected by the optical sensors 8a to 8c after a separating position where the transfer material is separated from the electrostatic transfer belt 1 is passed by the test pattern and before a supporting position where the electrostatic transfer belt 1 is supported by a tension roll 4 is first passed by the above mentioned test pattern image on the electrostatic transfer belt 1. |
