Paper is one of the most commonly used mediums to transmit information. The quality of the paper used as the medium to transfer information reflects the choice of how the information is to be conveyed. The substantial differences in the type and quality of paper need to be understood before making a choice. The differences of paper types are based on composition, color, coating, and consistency. Another difference, the structure of the paper’s surface, is critical to the impression and the stamping characteristics of the printed characters and images. The paper’s surface structure can range from very rough to extremely smooth. The large degree of surface roughness variation causes frequent problems for printing systems. The measurement and characterization of the paper’s surface structure then becomes an important task. Sensofar is offering perfect solutions for different paper measurement applications, with no limitations of mechanical profilers (which interact and modify the surface while measuring), point measuring sensors (extremely slow) or white light interferometers (fast but limited resolving highly structured surfaces).

MEASUREMENT OF PAPER HOLES
General low quality paper, like envelopes or recycled paper, have problems during the printing process. If the quantity of ink deposited on the surface is low, then some white or brown pits appear. To increase the quality,a higher amount of ink is used, but increasing the printing cost. Surface characterization or measuring surface roughness are some of the clues to reduce the cost of printing.

PERIODIC STRUCTURES OF PAPER AND ROUGHNESS ISOLATION
Paper usually has periodic structures (nets), which come from the fiber filter. Also periodic structures are made on purpose to get some particular effects. Traditionally, the measuring method consists on pressing the paper with an aluminum cylinder. As a consequence of the surface roughness the ring doesn’t contact with the whole surface. Air pressure is applied at one extreme of the cylinder and part of this air escapes between the paper and the cylinder. As a result, the loss of pressure is an indirect measurement of the surface roughness. With Sensofar's optical profilers the measurement of the surface roughness is done directly. Main frequencies of papers that have a periodic structure can be removed digitally. This way the high frequency structure can be separated from low order components. The Fourier transform and parameters are calculated by SensoMAP.