Apparatus for optically detecting contamination in particles of low optical-loss material

US5256886A · kind A · utility

Assignee

• E.I. DU PONT DE NEMOURS AND COMPANY · US

Inventors

• William E. Wolf · Chesapeake City, US
• Robert Livermore · Wilbraham, US
• David Dreyfuss · Nicholasville, US
• John J. Majeski · Chester, US
• Eugene Palecki · Wilmington, US
• Thomas Simpson · Rochester, US

Key dates

• Filing date: Apr 10, 1992
• Grant date: Oct 26, 1993
• Expiry date: Apr 10, 2012

Classification

• Technology area (CPC G): Physics
• CPC primary: G01N2201/1087
• WIPO field: Measurement
• WIPO sector: Instruments

Abstract

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 sc…