HP Color 9850mfp Service Manual - Page 93

II UNIT EXPLANATION hp Color 9850mfp WRITE 3. Calculating and correcting the color drift amount The transfer belt rotates to record the passage time for each color registration mark. The passage time is determined by the clock signal count corresponding to the detection edge of each registration mark as shown below. The detected values from PS8 and PS9 are recorded individually. [1] [5] 0 123 4567 8 [2] [4] 150 300 180 330 [1] Direction of the edge detection (direction of image) [2] Address number of the detected edge [3] Clock signal count value corresponding to the address for each detected edge [3] [4] Clock signal [5] Binarized digital signals The passage time differences between black (K) and each color are determined from the passage times detected at above. The time difference is called the color drift amount due to the image write timing. It also determines the difference between the edge detection timing difference for black (K) and the edge detection timing differences for each color. It is called the color drift amount due to the angle of the write unit. The determined value is compared with the set point and then it is corrected to meet the set point. 2-19