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Browse Prior Art Database

Surface Contamination Particle Counter

IP.com Disclosure Number: IPCOM000079335D
Original Publication Date: 1973-Jun-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 33K

Publishing Venue

IBM

Related People

Hopkins, WG: AUTHOR [+3]

Abstract

Described is a device to detect and count particles or asperities lodged on a flat surface, particularly upon a surface having a RMS value of 1-3 mu". The device comprises laser 10 aligned to direct beam 11 upon a moving flat surface 12, having particles 13, 14, 15 thereon. A condenser lens assembly 16 is aligned to detect the scattered light 17, 18, 19 from particles 13, 14, 15, respectively, for focusing into a light-sensitive means 20 such as a photomultiplier tube (PMT) or other light detector, in circular or stripe form. Means 20 generates a signal to amplifier 21, for comparison via comparator 22 against a reference voltage from reference means 23. A display means 24 for example, displays the result, in numerical format if desired.

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Surface Contamination Particle Counter

Described is a device to detect and count particles or asperities lodged on a flat surface, particularly upon a surface having a RMS value of 1-3 mu". The device comprises laser 10 aligned to direct beam 11 upon a moving flat surface 12, having particles 13, 14, 15 thereon. A condenser lens assembly 16 is aligned to detect the scattered light 17, 18, 19 from particles 13, 14, 15, respectively, for focusing into a light-sensitive means 20 such as a photomultiplier tube (PMT) or other light detector, in circular or stripe form. Means 20 generates a signal to amplifier 21, for comparison via comparator 22 against a reference voltage from reference means 23. A display means 24 for example, displays the result, in numerical format if desired.

In operation the surface is moved past the light beam to generate a pulse of light from the surface particle. This allows the amplifier to be AC coupled, thereby negating ambient light levels of a steady-state nature. Light-detection may be from a photodiode operating in the photovoltaic mode, for high sensitivity and low noise.

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