Surface Fiber Orientation Measurement from On-line Imaging, PaperCon 2010 Conference

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There have been a great variety of methods used over the years to measure fiber orientation and anisotropy in the lab and on-line, both with varying degrees of success. The small feature size of the fibers, the web’s varying optical reflectance properties, and the high manufacturing speed of board, but more significantly paper, have excluded the use of cameras and image analysis for on-line use in measuring fiber orientation. In recent years, however, there have been rapid advances in camera and image analysis technology enabling accurate and highly reliable on-line, non-contacting measurement of fiber orientation and its related characteristics.

It has taken the combination of state-of-the-art camera technology with new illumination innovations, the computational power of dedicated image analysis processors and image analysis algorithms in a scanning quality control system to deliver reliable fiber orientation measurements to the paper and board maker on-line. By pulsing a very powerful ring light it is possible to freeze the motion of the sheet to obtain a high quality image of the surface. Using proprietary algorithms and a dedicated image analysis processor, numerical values for fiber orientation angle, anisotropy, MD/CD and Max/Min orientation ratios are generated. These values are then made available for display, profiling and trending, along with the captured images and fitted curves with complete polar histograms. This new online measurement application offers a powerful tool for paper and board manufactures to help correct challenges like stack-lean, twist-warp, curl and print misregister.