Patent ID: 6397671
Filing Date: 2002-06-04
Classification: B65H

Abstract:
A sheet detecting device comprising:transmitting means for transmitting a transmission signal; receiving means for receiving the transmission signal from the transmission means, through a feeding path in which a sheet is fed, and the receiving means for outputting a reception signal; phase comparing means for comparing a phase of the reception signal outputted from the receiving means with a predetermined reference phase, and the phase comparing means for outputting a signal having a level corresponding to a phase difference therebetween; memory means for storing a predetermined reference level; and level comparing means for comparing the signal outputted from the phase comparing means with the reference level stored in the memory means, and the level comparing means for outputting a result of the comparison therebetween; first storing means for storing a phase of the reception signal outputted from the receiving means when no sheet is present in the feeding path; second storing means for storing at a predetermined time a phase of the reception signal outputted from the receiving means when no sheet is present in the feeding path; and third storing means for storing a phase of the reception signal outputted from the receiving means when one sheet is present in the feeding path, wherein the predetermined reference phase is determined in accordance with a difference between a sum of the phase stored in the first storing means and the phase stored in the third storing means, and the phase stored in the second storing means.