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Analysis of the Paper Formation and Periodic Structures by FFT Processing

Abstract:

Paper manufacturing process parameters affect properties of the finished sheet in various ways. This work deals with the use of ImageJ for the frequency domain processing of a paper sheet image to distinguish between the paper formation uniformity and regular structures in the paper*. The described properties have an impact on the behavior of the paper substrate in the converting and printing processes, as they contribute to the overall quality of the paper, its properties and printability. The analysis is performed using Fast Fourier Transform (FFT) processing. Modification of the FFT power spectrum and filtering of the light-transmission images of paper, obtained by a flat-bed scanner, allows identification and separation of two distinct phenomena: the paper sheet formation (uniformity of fibers and flocs distribution) pattern on one hand and periodic, regular structures imprinted in the paper structure caused by papermaking wire or press- or drying felt on the other. The analyzed samples include office papers of various quality grades. The attempt of automating the procedure by using ImageJ macros has been made.

*Our analysis is based on the work of Dr. I'Anson from UMIST. See e.g. http://pygarg.ps.umist.ac.uk/ianson/image_analysis/frequency.html


Keywords:

Paper formation, Paper marks, Fast Fourier Transform, Image processing, Paper quality and printability

Authors 
Ales Hladnik, Tadeja Muck and Ms. Maja Stanic

Organisation   
University of Ljubljana, Faculty of Natural Sciences and Engineering

Homepage   
http://www.ntf.uni-lj.si/

Short Biography   

Ales Hladnik, born 16.7.1967, Ljubljana, Slovenia

Education:

  • B.Sc. of Chemistry (1994, University of Ljubljana, Faculty of Chemistry and Chemical Technology)
  • Ph.D. of Technical sciences (2003, Technical University Graz, Austria)

Employment and functions:

  • Pulp and Paper Institute Ljubljana (1995-2006): higher researcher II, research field - paper/board coating and printing
  • University of Ljubljana, Faculty of Natural Sciences, Dept. of Textiles (2006-): assistant professor at the Chair of Information and Graphic Arts Technology

Main research fields:

  • Implementation of modern statistical and computer supported methods in graphic arts and papermaking: artificial neural networks, multivariate analysis (PCA, PLS, clustering techniques, multifactorial ANOVA), experimental design, image processing and -analysis
  • Research in the field of digital, especially ink-jet, printing
  • Investigation of interactions between a substrate (paper, board, plastic foil) and a liquid (water, printing ink, coating colour, surface sizing agent)
  • Information communication technologies / Interactive media.
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