On-line fiber orientation distribution measurement

In a system for making paper in an environment of noise and vibration, the system having a papermaking pulp solution from stock, said pulp solution being fed into a forming apparatus, forming a web, said web being dewatered in a dewatering apparatus and dried in a drying apparatus, said web then becoming a moving sheet, said moving sheet having a first surface and a second surface and having a direction of motion and a width perpendicular to said direction of motion, wherein the improvement comprises:

• a source of coherent light for producing and directing a first light pattern onto said first surface of said moving sheet, said first light pattern having an intensity sufficient to transmit light through said sheet and form a second light pattern on the second surface, the shape of the second light pattern being dependent at least in part on the fiber orientation in the sheet;
• a sensor for sensing said second pattern produced on said second surface, said sensor and light source being subjected to the noise and vibration of the environment such that relative movement exists between said source and said sensor whereby said second pattern moves at or below a predetermined velocity and within a predetermined range relative to said sensor;
• said sensor further comprising video camera means for producing an image signal corresponding to an image of said second pattern and said camera means having a field of view that is substantially larger than the second pattern whereby the relative movement of the source and sensor will move the second light pattern through the predetermined range that is totally within the field of view of said camera;
• means for producing a freeze frame of said image signal, said freeze frame being representative of said second pattern during a period of time that is sufficiently long to allow the camera to produce an image signal and is sufficiently short to freeze the image of the second light pattern when it is moving at or below the predetermined velocity within the field of view;
• means for analyzing the shape of the second light pattern to determine the orientation of fibers;
• and
• means for generating control signals, said control signals controlling the forming apparatus until said means for determining the orientation of fibers in said sheet determines a desired orientation of fibers.