Method and apparatus to monitor and control sheet characteristics on a creping process

A method of measuring the geometric characteristics of a crepe structure on a paper sheet, the method comprising the steps of:

• generating data values representing characteristics of positions on a paper sheet by repeatedly emitting at least two emission beams against each of the positions on the paper sheet and reflecting the two beams off of the positions and into a sensor constructed and arranged to absorb and measure the intensity of the reflected emission beams, wherein the positions on the crepe structure on the paper sheet lie along a substantially straight line extending in a substantially cross machine direction,
• correcting the measured intensity of the data values by using an nth order polynomial fit,
• performing a row-by-row smoothing operation of the corrected data values using a filter algorithm,
• identifying positive to negative transitions within the smoothed data values, and
• correlating the identified positive to negative transitions with previously identified values known to correspond to particular geometric dimensions to determine geometric features of the crepe structure, said determined geometric features comprising a beginning and ending of a crepe feature.