| 摘要 |
PURPOSE:To output precisely plural output pictures without superposing, separation and uneven density by detecting a real sub-scanning position of an output head and correcting the detected position to an objective sub-scanning position. CONSTITUTION:The rotation of an output drum 30 is detected by a rotary encoder 13, and outputted as a pulse signal MP through a frequency multiplying circuit 61 and an 1/M frequency divider 63. The signal MP indicates the objective sub-scanning position of the output head 32 and a pulse signal from a linear encoder 35 indicates the real sub-scanning position of the output head 32. When the real sub-scanning position of the output head 32 coincides with the objective position MP=LP is formed. When the real position is advanced and delayed, MP<LP and MP>LP are formed respectively. Consequently, the outputs of an up/down counter 64 are ''0'', ''-'' and ''+'', respectively. The counted value of the counter 64 is compared with leading data LD and delaying data DD by comparators 65, 66 respectively and a data selector 67 changes the frequency dividing ratio of a programmable frequency divider 62 on the basis of the compared results to change the turning speed of a pulse motor 33, i.e. the sub-scanning speed of the output head 32.
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