KNIFE MARK DETECTING CIRCUIT OF KNIFE MARK DETECTING DEVICE

摘要

PURPOSE:To ensure the detection of the knife mark, by amplifying the output of a photomultiplier, dividing the result by a divider through a low pass filter and an high pass filter, comparing the output of the divider with a preset threshold level, and outputting a judging signal when the output of the divider exceeds the threshold level. CONSTITUTION:The output of the photomultiplier is amplified 13 and inputted into the subtractor 15 through the low pass filter 14 whose passing frequency is about 20Hz. Subtraction is performed with regard to the output which is not passed the low pass filter 14, and the effect of the fluctuation of a material to be checked 4 is removed. A power source noise is removed by the high pass filter 16 whose passing source noise is removed by the high pass filter 16 whose passing frequeny is about 200Hz. The divider 17 divides the signal which has passed the high pass filter 16 by the output of the amplifier 13 through the low pass filter 14 in order to remove the effect of difference in brightness of the material to be checked 4 due to the kinds of the material. The output of the divider 17 is compared with the preset threshold level L in a comparator 18. When the output exceeds the said threshold level L, the judging signal is generated.