Method and apparatus for determining the fiber orientation of paper

Here are disclosed method and apparatus for rapidly and accurately determining fiber orientation of paper being in a standstill or moving in a paper machine and useful for grade study and quality control of the paper. The projector means projects an unpolarized light beam perpendicularly to a surface of the paper to be tested, then a light beam reflected by the paper surface is caught by eight or more light receiving means distributed on a circumference of circle defined, on the incident side of the unpolarized light beam, in a plane extending in parallel to the paper surface around a point at which the above-mentioned parallel plane intersects an axis of the incident light beam, and a light information signals output from these light receiving means are subjected to a predetermined arithmetic processing to obtain the fiber orientation characteristics such as fiber orientation index value and fiber orientation angle.