John J Majeski Deceased2201 Springhouse Ln, Chester, PA 19014

5256886, Oct 26, 1993

Apr 10, 1992

7/863961

William E. Wolf - Chesapeake MD
Robert H. Livermore - Horten, NO
David D. Dreyfuss - Kettering OH
John J. Majeski - Aston PA
Eugene F. Palecki - Wilmington DE
Thomas W. Simpson - Boothwyn PA

E. I. Du Pont de Nemours and Company - Wilmington DE

G01N 1506

250574

An apparatus for optically detecting light-absorbing contamination in at least one particle of low optical-loss material comprises an optical integrating chamber for containing the particles. A laser for emitting a laser beam to illuminate the particles is mounted in the plane of rotation of a rotating mirror such that the laser beam scans in a fan scan. A scanning assembly is mounted in optical alignment with the laser for reflecting the laser beam and for causing the laser beam to scan the particles in the optical integrating chamber. A focusing assembly is mounted in optical alignment with the laser for focusing the scanning laser beam onto the particles in the chamber, the focusing assembly operating in conjunction with the scanning assembly so that light from the laser beam is reflected from the particles and is repeatedly scattered onto the interior walls of the integrating chamber. A light sensing assembly is mounted on the integrating chamber for receiving the repeatedly scattered light from the interior walls of the integrating chamber and for generating a signal indicative of the intensity of the repeatedly scattered light. A decrease in the intensity of the repeatedly scattered light is a function of the presence of light-absorbing contamination in the material.