Optics: measuring and testing – By polarized light examination – With light attenuation
Patent
1996-11-27
2000-05-23
Font, Frank G.
Optics: measuring and testing
By polarized light examination
With light attenuation
356371, 356429, G01B 1124, G01B 1130, G01N 2184
Patent
active
060671629
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for measuring the roughness of the surface of a material and more particularly to a method of measuring the roughness of a material surface by measuring a light scattering ellipse reflected off the surface along the scattering ellipse's minor axis.
2. Discussion of the Related Art
Such a method is known from Swiss patent 552 197. Moreover, it is proposed to use a line of detectors along the major axis of the scattering light ellipse which arises in the event where the surface of the material shows a certain roughness and is illuminated by a bundle of parallel light beams under a predetermined angle. Preferably there the scattering light cone at the half width in the vicinity of the glancing angle is measured and is used as a measure for the roughness of the investigated surface. Furthermore, an evaluation using a television camera instead of an evaluation with a line of detectors is described.
The evaluation of the roughness is of remarkable importance at the manufacturing of paper since the roughness or reciprocally the smoothness gives evidence about the printability of the paper.
In the known device it must be cared for that at the location of the illumination of the web of material by the bundle of light beams this web has to be guided in such a way that due to the movement no too large positional changes result in the plane where the web of material extends in order to avoid that the scattering light ellipse is moving out of the scanning area of the detector. The same problem results where the surface to be measured is too rough so that the scattering light distribution within the major axis of the scattering light ellipse is exceeding the scanning field as provided by the line of detectors or the television camera, respectively.
BRIEF SUMMARY OF THE INVENTION
Therefore, it is the object of the present invention to develop the method as exercised by the known device in such a way that the roughness of very rough surfaces still may also be detected. The solution of this object is achieved by a method for measuring the roughness of the surface of a material, such as a paper web, traveling in a first direction. The surface of the material is illuminated by a bundle of parallel light beams at a glancing angle, causing the light reflected off the surface of the material to form a scattering ellipse of reflected light whose major axis is parallel to the direction of the material travel and which is evaluated by detector means oriented along the major axis of the scattering ellipse, whereby the evaluation of the roughness of the surface of the material includes the step of deviating the detector means away from the major axis of the scattering ellipse toward a minor axis that is perpendicular to the travel of the material. Further advantageous embodiments of the inventive method may be taken from the dependent claims.
BRIEF DESCRIPTION OF THE SEVERAL VIEW OF THE DRAWINGS
With respect to embodiments shown in the attached drawings the invention shall be further explained in the following. It shows:
FIG. 1 the basic measuring device; and
FIG. 2 a schematic drawing for explaining the method according to the invention.
DETAILED DESCRIPTION OF THE INVENTION
According to FIG. 1, the surface 14 to be investigated is illuminated by means of a collimated bundle of light beams 12 which are expanded by a telescopic means 10. The beams 16 reflected from the rough surface 14 via an optic means 18 are projected onto a receiver 20 which may consist of a line-shaped or an aerial detector device and in particular may be provided by a line or aerial camera (Vidicon or CCD).
According to FIG. 2, it may be taken that a line camera 20' where it is aligned along the direction of movement of the surface 14 as shown by the arrow does not completely encompass the major axis of the scattering light ellipse in the event where the material shows a great roughness and the scattering ellipse is accordingly expanded. Rotation of the li
REFERENCES:
patent: 3922093 (1975-11-01), Danliker et al.
Hagen Werner
Schaust Karlheinz
Font Frank G.
Honeywell AG
Merlino Amanda
Miologos Anthony
Sapelli Arthur A.
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