WRITE hp Color 9850mfp 2. Detecting the color registration mark PS8 and PS9 detect the edge of the color registration mark " " for each color and convert to digital sig- nals. The edge detection for one " " is performed at four positions. [4] [5] [1] II UNIT EXPLANATION [3] [2] [1] Direction of the edge detection (direction of [4] Color registration sensor F, R (PS8, PS9) image) [5] Color registration mark [2] Binarized digital signals [3] Detection signal of the color registration sen- sor F, R (PS8, PS9) (analog signal) 2-18