Apparatus and method for analyzing parameters of a fibrous substrate
AssigneeChampion International Corporation
InventorIrving R. Brenholdt
Life of this patent
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Abstract
A radiation sensor provides on-line measurement of web MD/CD fiber orientation ratio, formation indexes of multiple spatial frequencies, and optical density as it relates to basis weight. A light source illuminates one side of a substrate to be measured. The radiation passing through the substrate is detected by a pair of detectors having fields of view along narrow strips which are perpendicular to each other. The combined field of view is scanned in a repetitive pattern traversing an area on the substrate to be analyzed. The detector outputs are processed to provide fiber orientation ratio, formation, and basis weight measurements.
Claims22
Apparatus for analyzing a fibrous substrate such as paper to evaluate the orientations of fibers therein comprising:
- light source means for illuminating one side of a substrate to be analyzed;
- first and second light detector means for detecting light from said light source which has passed through to the other side of the substrate and producing an output proportional to the light detected thereby;
- means for limiting the field of view of said first light detector means to an elongated narrow strip along a first direction;
- means for limiting the field of view of said second light detector means to an elongated narrow strip along a second direction;
- means for jointly scanning the fields of view of said light detectors in a repetitive pattern traversing said first and second directions to cover an area on the substrate being analyzed;
- means for filtering the output of said first detector to eliminate components thereof below a predetermined frequency;
- means for filtering the output of said second detector to eliminate components thereof below a predetermined frequency;
- and
- means for processing the filtered outputs of said detectors to produce a combined signal indicative of the ratio of fibers of said substrate oriented in said first direction to those oriented in said second direction.
Apparatus for analyzing properties of a fibrous substrate comprising:
- means for directing light from a light source through a substrate to be analyzed;
- a first light detector;
- first slit means for limiting the field of view of said first light detector to an elongated narrow strip in a first direction;
- a second light detector;
- second slit means for limiting the field of view of said second light detector to an elongated narrow strip in a second direction generally perpendicular to said first direction;
- optical means for superimposing and scanning the limited fields of view of said detectors across said substrate in said first and second directions to monitor light passed through the substrate from said source and produce output signals in accordance therewith;
- and
- means for processing the output signals from said detectors to provide information as to specific properties of said substrate.
A method for analyzing the fiber orientation ratio of a fibrous substrate such as paper comprising the steps of:
- directing light from a light source through a substrate to be analyzed;
- viewing the light passing through the substrate with a first detector having a field of view limited to an elongated slit in a first direction and a second detector having a field of view limited to an elongated slit in a second direction perpendicular to said first direction;
- scanning the fields of view of said first and second detectors in a repetitive pattern traversing said first and second directions to cover an area on the substrate being analyzed;
- and
- processing the outputs of said first and second detectors during said scanning step to produce a signal indicative of the ratio of fibers of said substrate oriented in the direction of said first slit to those oriented in the direction of said second slit.
Dependencies are inferred from the claim text.