| 摘要 |
An apparatus and method for detecting wrinkling of sheets of material is provided. A change in an angle the sheet forms with a reference line can be detected. When the change in the angle exceeds a threshold value, wrinkling of the sheet can be detected. In an exemplary embodiment, ultrasound signals may be used to detect wrinkling. As ultrasound passes through a sheet of material, for example, paper, there is both a phase shift and an amplitude reduction to that ultrasound signal. As the angle of the sheet changes with respect to the ultrasound signal due to wrinkling of the sheet, the phase shift and amplitude of the signal after it passes through the sheet changes. Thus, as the sheet begins to wrinkle, there is a change in the phase shift and amplitude of the signal. These changes can be used to detect the start of a document jam or wrinkling of a sheet of material.
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