US 4,972,091 A · Method and apparatus for detecting the presence of flaws in a moving sheet of material

Abstract

The present disclosure describes an apparatus and a method for detecting the presence of flaws in a moving sheet of material. The apparatus comprises a light source for projecting a light beam; a beam shaping unit for shaping the light beam into a predetermined structured light pattern, and projecting the structured light pattern onto a portion of the surface of the sheet; an optical unit for collecting light emitted from the portion of the surface; and a light detecting unit for receiving the light collected by the optical unit and generating an electrical signal indicative of the intensity of the light generated from the portion of the surface. A signal processing unit is provided for filtering the electrical signal, the signal processing unit having predetermined characteristics specifically adapted to match an expected electrical signal corresponding to the predetermined structured light pattern. The present invention can be used in a transmission mode wherein the light beam is projected onto one side of the moving sheet and detected from the opposite side, or in a reflective mode wherein the light beam is projected onto and detected from the same side of the moving sheet.

Claims12

Dependent claims

An apparatus for detecting the presence of flaws in a moving sheet of material, comprising:

a coherent laser light source for projecting a light beam;
beam shaping means for shaping said light beam into a predetermined structured light pattern, and projecting said structured light pattern onto a portion of the surface of said sheet;
optical means for collecting light emitted from said portion of said surface;
light detecting means for receiving said light collected by said optical means, and generating a time-resolved electrical signal matching said predetermined structured light pattern, said signal being indicative of the intensity of said light emitted from said portion of said surface;
signal processing means for filtering said electrical signal, said signal processing means having predetermined characteristics specifically adapted to match an expected electrical signal corresponding to said predetermined structured light pattern;
and
signal detecting means connected to the output of said signal processing means for detecting the presence of flaws in said sheet.

4 more elements

A method for detecting the presence of flaws in a moving sheet of material, comprising the steps of:

(a) projecting a laminar light beam;
(b) shaping said light beam into a predetermined structured light pattern;
(c) projecting said predetermined light pattern onto a portion of the surface of said sheet;
(d) collecting light emitted from said portion of said surface;
(e) generating an electrical signal indicative of the intensity of said light collected during said step (d);
(f) filtering said electrical signal with a filter having predetermined characteristics specifically adapted to match an expected electric signal corresponding to said predetermined structured light pattern;
and
(g) detecting the presence of flaws in said sheet from the output signal of said filter.

5 more elements

Dependencies are inferred from the claim text.

Method and apparatus for detecting the presence of flaws in a moving sheet of material

Life of this patent

Method and apparatus for detecting the presence of flaws in a moving sheet of material

Life of this patent

Abstract

Claims12