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US 4,931,657 AGranted
On-line texture sensing
AssigneeMacMillan Bloedel Limited
InventorsKevin C. D. Houston, Roman E. Popil
Life of this patent
Estimating the term…
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AssigneeMacMillan Bloedel Limited
InventorsKevin C. D. Houston, Roman E. Popil
Estimating the term…
The texture of a travelling web is determined by instantaneously illuminating an area of the web via a strobe light and phtographing the illuminated area by a video camera correlated to operate in conjunction with the strobe. The signal from the camera is digitized, histogrammed and analyzed to determine the characteristics of the web. The strobe light may direct the light through the web or at an angle to the web and the video camera depending on the characteristics to be determined may be positioned to receive specularly reflected light from the web or reflected light or positioned on the opposite side the web to receive light transmitted through the web. In one embodiment the light is polarized and directed at Brewster's angle onto the surface of the web and only similarly polarized specularly reflected light is received by the camera.
An optical system for determining the texture of a travelling paper web comprising a strobe light means for instantaneously illuminating areas on a first surface of said web as said web traverses said strobe light means, means to polarize said light from said strobe means in a direction substantially parallel to the plane of travel of said web thereby to illuminate each said area with light polarized parallel to the plane of said web, said beam of light being, directed to said paper at an angle within 3 degrees of Brewster's angle for the paper, video camera means focused to view at least a portion of said areas when illuminated by said strobe light means, said camera means having its focal axis aligned to receive a specular light from said illuminated areas, polarized filter means to transmit to said camera only light polarized substantially parallel to the light polarized by said means to polarized said light thereby to provide video image signals representing said portions of said areas in substantially stop motion and means to analyze said video signals to determine texture characteristics of said web.
An optical system for determining the texture of a travelling paper web comprising a strobe light means for instantaneously illuminating areas on a first surface of said web as said web traverses said strobe light means, video camera means focused to view at least a portion of said areas when illuminated by said light means thereby to provide a video image signals representing said portions of said areas in substantially stop motion, means to digitize of said video image signals, means to form a histogram of such digitized video signals indicating degrees of brightness versus frequency, and means to analyze said histograms to determine the standard deviation of distribution of different brightness.
An optical system for determining the amount of dirt on a travelling cellulosic fibre web comprising a strobe light means for instantaneously illuminating areas on a first surface of said web as said web traverses said strobe light means, video camera means focused to view at least a portion of said areas when illuminated by said strobe light means thereby to provide a video image signals representing said portions of said areas in substantially stop motion, means to digitize said video image signals to provide a video signal and analysis means to analyze said video signals to determine the locations and sizes of areas on said web reflecting light of selected intensities relative to selected threshold intensity to obtain a measure of colour areas of the selected intensities in said web.
An optical system for detecting plastic pieces in a travelling cellulosic fibre web comprising an infra red strobe light means for instantaneously illuminating areas on a first surface of said web with infra red light as said web traverses said strobe light means, video camera means focused to view at least a portion of said areas when illuminated by said strobe light means thereby to provide a video image signals representing said portions of said areas in substantially stop motion, means to digitize said video image signals to provide video signals and analysis means to analyze said video signals to determine the locations and size of areas on said web reflecting infra red light having an intensity below a selected threshold thereby to detect plastic in said pulp.
Dependencies are inferred from the claim text.