Control method of vertical scan speed

In a method of controlling vertical scan speed in the relative movement of a document and a recording medium by a predetermined length in a vertical scan direction and effecting reading and recording of said document, the improvement comprising:

• storing the signals thus read in a line buffer memory for storing signals which are scheduled to be recorded;
• setting vertical scan speeds in accordance with the number of the buffered code bits of said line buffer memory in at least a first vertical scan mode and a second vertical scan mode which is different from said first scan mode;
• changing the mode from said first vertical scan mode to said second vertical scan mode when the number of the buffered code bits of said line buffer memory reaches a first reference value;
• and
• changing the mode from said second vertical scan mode to said first vertical scan mode when the umber of the buffered code bits of said line buffer memory reaches a second reference value which is different from said first reference value, wherein recording to said recording medium is effected in the highest speed vertical scan speed mode irrelevantly to the number of the buffered code bits after the last code of a page is received.

In a method of controlling vertical scan speed in the relative movement of a document and a recording medium by a predetermined length in a vertical scan direction and effecting reading and recording of said document, the improvement comprising:

• storing the signals thus read in a line buffer memory for storing signals which are scheduled to be recorded;
• setting vertical scan speeds in accordance with the number of the buffered code bits of said line buffer memory in at least a first vertical scan mode and a second vertical scan mode which is different from said first scan mode;
• changing the mode from said first vertical scan mode to said second vertical scan mode when the number of the buffered code bits of said line buffer memory reaches a first reference value;
• and
• changing the mode from said second vertical scan mode to said first vertical scan mode when the number of the buffered code bits of said line buffer memory reaches a second reference value which is different from said first reference value, wherein the application time of a current to said recording head for printing in the scan line unit is different in accordance with the content of said video signals of the scan line to be recorded;
• the vertical scan speed is divided in advance into V.sub.o (stop)<V21<
• . . . <V.sub.N and is changed stepwise only one stage at a time so that the acceleration and deceleration of the vertical scan speed is below a predetermined level, and is changed only one stage by one;
• and
• the vertical scan speed further includes:
• a first vertical scan mode wherein when the vertical scan speed of a present scan line and that of a next scan line are assumed to be V.sub.i and V.sub.i+1, respectively, and when the vertical scan speed after the next scan line and so forth are decelerated one stage by one, the vertical speed is accelerated and the vertical scan speed of the next scan line is set to V.sub.i+1 if there does not exist any scan line having a printing speed lower than the vertical scan speed and when the vertical scan speed of the next scan line is assumed to be V.sub.i in cases other than the case described above and when the vertical scan speeds after the next scan line are decelerated one stage by one and when there does not exist any scan line having a printing speed lower than the vertical scan speed, the vertical scan speed of the next scan line is set to V.sub.i (uniform speed) and the vertical scan speed of the next scan line is decelerated to V.sub.i-1 in cases other than the two cases described above;
• and
• a second vertical scan mode wherein the vertical scan speed is set below the lowest printing speed.