PURPOSE: To synchronize normal variable density values with signal levels so as to deal with the demand for the improvement of devices by a method wherein the printing speed is detected, wherein the clock frequency of the driving signals of photo receiving elements in proportion to the detected printing speed signals, and wherein the scanning position of the photo receiving elements on a printing object is consistently maintained at a certain level.
CONSTITUTION: A detector 7 for detecting the number of revolutions of a rubber cylinder 2 is mounted at the axial end of the rubber cylinder 2 for detecting the number of revolutions of the rubber cylinder 2 by virtue of the number of pulses generated per unit time. A speed converter converts the number of pulses into the printing speed of a printer. The amplification ratio of an amplifier 9 for amplifying to an appropriate signal level a variable density value detection signal representing a printing pattern from a linear camera 5 can be altered in a stepless way, and this amplifier 9 alters the variable density value detection signal representing the printing pattern from the linear camera 5 in proportion to a printing speed signal detected by speed detection devices 7, 8 so as to consistently maintain the signal level of the variable density value detection signal at a certain level. A scanning position retaining device 10 alters the frequency of a driving signal from the linear camera 5 in proportion to the printing speed signal detected by the speed detection devices 7, 8 so as to consistently retain the scanning direction of the linear camera 5.
KAWADA NORIYUKI
SHIMADA HITOAKI
MATSUMOTO TAKEMASA
