| 摘要 |
PURPOSE:To realize many tone wedge expressions with simple constitution by executing the multivalued pulse width modulation for the picture element concerning the main scanning direction. CONSTITUTION:An input picture signal 36 synchronizes with a picture element clock, is inputted to respective comparators 41, 42 and 43 and on the other hand, read only memories 44, 45 and 46 synchronize with a double picture element clock of the double frequency of the picture element clock and outputs a threshold. In an output 51 of a comparator 41, an 'AND' is obtained with a pulse signal phiA at a gate 47, and in an output 53 of a comparator 42, the 'AND' is obtained with a pulse phiB at a gate 48 respectively. The pulse width of pulse signals phiA and phiB is 1/3 and 2/3 of the pulse width of respective picture element clocks. In the output signal of the gate 47, the output signal of the gate 48 and an output 55 of a comparator 43, the 'AND' is obtained by an OR gate 49 and a dither picture 37 is obtained.
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