Method and apparatus for measuring orientation of constituents of webs or sheets

DETAILED DESCRIPTION The present invention, intended to achieve the aforesaid object, provides a method and apparatus for measuring the orientation of the constituents of web or sheet products by using a cavity resonator composed of a pair of waveguides having in their bottoms a transmitting antenna and a receiving antenna, respectively, and opposed at their openings to each other with a small clearance defined therebetween, said method comprising the steps of: inserting a sample portion of said web or sheet product into said small clearance, emitting linearly polarized microwaves from said transmitting antenna toward said open ends to allow them to fall on the surface of said sample portion at right angles thereto while producing a relative motion betwen the plane of polarization of microwaves and said sample portion around the axis of said cavity resonator, receiving the microwaves guided from the waveguide disposed on the transmitting side via the sample portion in said clearance to the waveguide disposed on the receiving side so as to find the amount of microwaves absorbed by said sample portion, and determining the orientation of the constituents of said web or sheet product from the angular position of said sample portion, where said amount of absorption is at a maximum, relative to said plane of polarization.