METHOD AND APPARATUS FOR OPTICALLY MEASURING PROPERTIES OF A MOVING WEB

摘要

The invention relates to a method and apparatus for measuring and controllin g optical properties of a moving web (2). Sensor heads (1a, 1b) are installed in the same location on the opposite sides of the web to be measured so that there is at least one means of illuminating (3a, 3b) the web and at least on e means of detecting radiances (4a, 4b) on both sides of the web. At least one means of illuminating the web of at least one side is controlled so as to provide at least two different lighting states. Measuring the values in different lighting states with both means of detecting radiances simultaneously allows determination of the optical properties of the web on its both sides.