Optics: measuring and testing – By shade or color – With color transmitting filter
Patent
1996-11-26
1998-10-13
McGraw, Vincent P.
Optics: measuring and testing
By shade or color
With color transmitting filter
25033902, 356429, G01J 351
Patent
active
058220704
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for the evaluation of material properties and more particularly to an apparatus for the detection of the material properties of moved paper webs.
BACKGROUND ART
In this connection it is known to measure material properties as e.g. humidity and basis weight of moved paper webs by illuminating the paper web and detecting and evaluating certain infrared absorption bands via infrared filters within the transmitted light or the reflected light, respectively. In order to scan the whole width of the paper web with respect to its properties a sensor head is movable transverse to the paper web or a stationary measuring device arranged above the paper web generates a moving light spot and the infrared absorption bands contained in the reflected light are evaluated. The last referenced measuring device e.g. may be taken from U.S. Pat. No. 5,073,712. In order to improve the measuring accuracy this known measuring device still provides for the arrangement of calibrating samples within the stationary measuring device and for the arrangement of compensation samples lateral of the moved web of material.
From EP-0 390 623 A2 furtheron an optical system for the detection of the properties of a moved sheet-like material is known at which on both sides of the web optical fibers are arranged which extend over the width of the web and are guiding light from a light source to the web and from the web to detectors.
DISCLOSURE OF THE INVENTION
Departing from this prior art it is the object of the present invention to devise a measuring apparatus which allows in a simple manner the scanning of material properties over its whole area. The solution of this object is achieved by the apparatus of the present invention whereby a moved material web (10) is illuminated along bands by an illumination device (12,12') located transversely to the moving material web (10). The illuminated bands are imaged onto a two-dimensional camera via optics (16) and a two-dimensional filter device (18). The filter device (18) consists of individual strips (18.sup.1 -18.sup.n) isolated by optically separating walls (28). The pixels produced by the filter strips are translated into absorption profiles by a computer (22).
BRIEF DESCRIPTION OF THE DRAWINGS
With respect to the figures of the attached drawing in the following the apparatus according to the invention shall be further described. It shows
FIG. 1 a basic representation of the whole apparatus;
FIG. 2 a representation of the used filter device;
FIG. 3 the scheme of evaluation of a portion of a camera picture; and
FIG. 4 the principle of the total evaluation.
BEST MODE FOR CARRYING OUT THE INVENTION
According to FIG. 1 a web 10 extending normal to the drawing plane and representing the material under test is illuminated by a line-shaped or rectangular light source 12, respectively, which is arranged transverse to the web 10. The light preferably comprises white light; however it also may be produced by an infrared radiator. For a material 10 which is more or less opaque the measuring is done with the reflected light and the light source 12 therefore is arranged above the web 10. At the measuring of transparent material the light source 12 is arranged below of the web 10.
On both sides of and lateral to the web 10 a reference light source 14, 14' is arranged which has a spectrum similar or equal to the material under test which is achieved by the series connection of an according combination of infrared filters ahead of the light source. However, it is also possible to use a reference sample of the actual material under test as compensation sample. In the event where the measuring task is frequently changing devices are required where individual filters may be added or removed in order to optimize the design of the reference light source.
The material under test provided by the web 10 comprises web-shaped, sheet-like materials as e.g. paper, coated cardboard, varnished sheet metal and transparent or opaque foils or plastic or ce
REFERENCES:
patent: 2466615 (1949-04-01), Rusca et al.
patent: 3906232 (1975-09-01), Melhofer
patent: 4224513 (1980-09-01), Casey et al.
patent: 5071514 (1991-12-01), Francis
patent: 5073712 (1991-12-01), Hellstrom
patent: 5166755 (1992-11-01), Gat
McGraw Vincent P.
Miologos Anthony
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