Fast Fourier Transform and Filtered Image Analyses of Fiber Orientation in OSB

The objective of this paper is to investigate the relationship between resolution of images and measurement of fiber orientation in oriented strand board with the ultimate aim of optimising the fiber orientation and quality of the manufactured product. An important consideration has been the capture of images from a distance of 2 meters corresponding to conditions on an OSB production line. In this paper, Filtered Image Analysis (FIA) was used to measure fiber orientation at different resolutions, and results were compared with those for strand grid models. These grid models were adopted to investigate how the FIA technique measures orientation. A two-dimensional Fast Fourier Transform (FFT) analysis was also investigated as a comparative method for measuring fiber orientation. The following conclusions can be drawn: the FFT analysis measures the periodicity of lines and indicates the orientation of lines. The FIA measures the orientation of zones surrounded by lines and shows the orientation of the zones. Hence, the FFT analysis and the FIA analysis measure orientation differently. Both methods are able to measure the fiber orientation of the OSB from a high resolution image. In addition the FIA technique could also measure the fiber orientation from low-resolution images and from a distance of 2 meters. In conclusion, whilst the FFT method is able to analyse high resolution images successfully, the FIA method is superior for analysing low resolution images and the orientation of OSB strands under production condition. Received 16 November 1999