| 摘要 |
A method and a device for measuring the fibre orientation anisotropy in a fibrous structure such as a sheet of paper or a textile. According to this method, a linearly polarized, far infrared laser beam is directed towards one side of the fibrous structure whose fibre orientation anisotropy is to be measured. The incident energy of the laser beam is measured before this beam traverses the fibrous structure, and its transmitted energy is measured on the other side of the fibrous structure. The transmission coefficient T of the laser beam is determined in at least two different orientations of the polarization plane of the beam with respect to the fibrous structure, this coefficient T being the ratio of the transmitted-to-incident energies. This coefficient T varies exponentially with the basis weight of the fibrous structure and the ratio alpha of the absorption coefficients that can be derived from two measurements of coefficient T in two different orientations of the polarized beam, gives a quantitative evaluation of the amount of fibre orientation anisotropy, the value of this ratio alpha be equal to 1 when no anisotropy is present in the fibrous structure.
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