Detection system for distinguishing between voids and foreign particles in materials and method

A system for detecting the presence of particles or voids in material of the type which is substantially transparent to radiation at a given wavelength in the far infrared range of about 70 microns to about 2000 microns, said system comprising:

• (a) means for producing a laser beam of electromagnetic radiation at said given wavelength;
• (b) means for directing said beam into said material along a predetermined path incident to said material such that
• (i) any portion of said beam which passes through said material unobstructed by voids or foreign particles within said material does so along predictable non-impinging paths, and
• (ii) any portion of said beam which impinges one of said voids or foreign particles as it passes through said material is scattered thereby along scattering paths which define an overall scattering pattern distinctly characteristic of whether the impinged void or foreign particle is generally spherical or non-spherical in shape;
• and
• (c) a detection arrangement for detecting said scattered radiation, if any, and distinguishing between whether the impinged upon void or particle is generally spherical or non-spherical and whether or not it is a relatively large or small particle relative to wave length of said beam, said detection arrangement including means detecting for scattered radiation at least at four distinct points behind said material relative to said incident path and equidistant from said material, said four points including
• (i) first and second points respectively located in intersecting perpendicular planes, each of which includes said incident path, said first and second points being equidistant from the line of intersection of said planes, and
• (ii) third and fourth points respectively located in said planes equidistant from said intersection line but further from the latter than said first and second points.

A method of detecting the presence of particles or voids in a material of a specific type capable of passing a particular beam of radiation therethrough, said method comprising:

• (a) producing said beam of radiation;
• (b) directing said beam into said material along a predetermined path incident to said material such that
• (i) any portion of said beam which passes through said material unobstructed by voids or foreign particles within said material does so along predictable non-impinging paths, and
• (ii) any portion of said beam which impinges one of said voids or foreign particles as it passes through said material is scattered thereby along scattering paths which define an overall scattering pattern distinctly characteristic of whether the impinged void or foreign particle is generally spherical or non-spherical in shape;
• and
• (c) detecting said scattered radiation, if any, and distinguishing between whether the impinged upon void or foreign particle is generally spherical or non-spherical in shape.

A method of detecting the presence of particles or voids in material of the type which is substantially transparent to radiation at a given wavelength in the far infrared range of about 70 microns to about 2000 microns, said method comprising:

• (a) producing a laser beam of electromagnetic radiation at said given wavelength;
• (b) directing said beam into said material along a predetermined path incident to said material such that
• (i) any portion of said beam which passes through said material unobstructed by voids of foreign particles within said material does so along predictable non-impinging paths, and
• (ii) any portion of said beam which impinges one of said voids or foreign particles as it passes through said material is scattered thereby along scattering paths which define an overall scattering pattern distinctly characteristic of whether the impinged void or foreign particle is generally spherical or non-spherical in shape;
• and
• (c) detecting said scattered radiation, if any, and distinguishing between whether the impinged upon void or particle is generally spherical or non-spherical and whether or not it is a relatively large or small particle, said detection step including detecting for scattered radiation at least at four distinct point behind said material relative to said incident path and equidistant from said material, said four points including
• (i) first and second points respectively located in intersecting perpendicular planes, each of which includes said incident path, said first and second points being equidistant from the line of intersection of said planes, and
• (ii) third and fourth points respectively located in said planes equidistant from said intersection line but further from the latter than said first and second points.