| 摘要 |
PROBLEM TO BE SOLVED: To improve the discontinuity of gradation characteristics due to abrupt increase in the density of dots, constituting a dot dither, accompanying a carriage return by an image output device, such as a color laser printer which concurrently uses a dot dither gradation process and laser pulse width modulation (PWM). SOLUTION: A gradation processor 9 is composed of a main address arithmetic part 68, a subordinate address arithmetic part 67, a default register 6, a select signal generation part 69, and a laser pulse width modulation (PWM) table 22. The select signal generation part 69 further assigns processes to the subordinate address arithmetic part 67 and default register 61 depending upon a threshold nc , even after an input value ni exceeds an intermediate PWM level processed by the main address arithmetic part 68. The laser irradiation time of dots, exceeding the intermediate level represented by PWM, is controlled in two stages and combined with a threshold pattern 84 to shorten the pulse time of dots, before a carriage return at the same time with the generation of the carriage return dots, thereby preventing density discontinuity with accompanies the carriage return of the dots from being generated. |
