PAPER CARRYING DEVICE, IMAGE FORMING DEVICE, THRESHOLD VALUE SETTING METHOD, AMPLIFICATION FACTOR ADJUSTING METHOD, PROGRAM AND RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To reduce time and labor requiring a user to set again a threshold value suitable for the thickness of use paper in a threshold value setting method in each case where the thickness of use paper is changed. SOLUTION: An image forming device 11 has a paper carrying path 31; an ultrasonic receiver 120 outputting a signal of which intensity becomes lower as the thickness of paper increases, when the paper is carried to the paper carrying path 31; and a comparator 125 for determining whether or not double feeding occurs on the paper carrying path 31 by comparing a value indicating the intensity of the signal with a threshold value. The image forming device 11 is further provided with a threshold value setting circuit 124 for setting, as the threshold value, an intermediate value between a signal value B indicating the intensity of a first signal and a signal value A indicating the intensity of a second signal when acquiring the first signal output from the comparator 125 by superposing and simultaneously carrying two pieces of plain paper on the paper carrying path 31 and the second signal output from the comparator 125 by carrying thick paper thicker than plain paper on the paper carrying path 31. COPYRIGHT: (C)2009,JPO&INPIT