APPARATUS FOR OPTICALLY DETECTING CONTAMINATION IN PARTICLES OF LOW OPTICAL-LOSS MATERIAL
 Inventors: William E. Wolf, Chesapeake, Md.;
Robert H. Livermore, Horten,
Norway; David D. Dreyfuss,
Kettering, Ohio; John J. Majeski,
Aston, Pa.; Eugene F. Palecki,
Wilmington, Del.; Thomas W.
Simpson, Boothwyn, Pa.
 Assignee: E. I. Du Pont de Nemours and
Company, Wilmington, Del.
Related U.S. Application Data
 Continuation-in-part of Ser. No. 693,523, Apr. 30, 1991, abandoned, and a continuation-in-part of Ser. No. 693,524, Apr. 30, 1991, abandoned.
 Int. CI.' G01N 15/06
 U.S. CI 250/574; 250/228;
 Field of Search 250/228, 234-236,
250/563, 573, 574; 356/237, 335, 338, 341, 343
 References Cited
U.S. PATENT DOCUMENTS
3,549,263 12/1970 Osawa et al 356/209
3,920,336 11/1975 Sackett 356/201
4,186,838 2/1980 Levitt et al 209/581
4,422,760 12/1983 Webster 356/244
4,601,576 7/1986 Galbraith 250/572
4,626,101 12/1986 Ogawa et al 250/563
4,740,708 4/1988 Batchelder 250/572
4,781,742 11/1988 Hill et al 65/29
4,885,473 12/1989 Shofner et al 250/574
4,892,409 1/1990 Smith 356/414
4,902,131 2/1990 Yamazaki et al 356/336
4,965,454 10/1990 Yamauchi et al 250/372
4,972,258 11/1990 Wolfetal 358/93
4,976,540 12/1990 Kitamura et al 356/38
Goodman, Joseph W. et al., "Laser Applications", vol. 4 Academic Press, New York (1980), pp. 171-174. Reynolds Metal Company, "Contamination Detector for Extrudable Dielectrics", Prepared for Electric Power Research Institute, (Final Rpt Jul. 1979).
Primary Examiner—David C. Nelms
Assistant Examiner—S. Allen
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.
37 Claims, 21 Drawing Sheets