Apparatus for characterizing fibrous materials using stokes parameters

An apparatus for determining fiber orientation parameters of sheet material during production processing, comprising:

• a polarized radiation generating system operable for providing polarized radiation having a frequency of at least 1×108 Hz up to 30 THz, said polarized radiation aligned to be incident on a sheet material to be characterized;
• a polarimeter aligned to receive radiation transmitted by said sheet material;
• a photodetector for measuring radiation received after polarization processing by said polarimeter, and
• a processor coupled to said photodetector for calculating Stokes parameters of said sheet material based upon intensities of said radiation received and determining at least one fiber orientation parameter of said sheet material based upon said Stokes parameters;
• wherein said sheet material is processed as a moving sheet by a processing system, further comprising a closed loop control between said processor and said processing system for automatically modifying at least one parameter of a production process run by said processing system based on said Stokes parameters or said fiber orientation parameter.