Halftone processing device for laser printer, facsimile using laser PWM in combination with distributed point accumulation halftone processing

摘要

Device has pulse width modulation (PWM) circuit (9) to control multi level toning using laser PWM. A threshold field converts toning value (ni) of input pixel to PWM toning value (p) on basis of threshold value (nc). PWM toning value is assigned to corresponding laser pulse pattern using PWM correspondence table (22) The PWM toning value (p) has a first bit area which has a value which is determined dependent on differential value between the input toning value and the threshold value. A second bit area has a value determined dependent on value represented by threshold value.