Technique for determining defect positions in three dimensions in a transparent structure
US5790247A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 26, 1996 |
| Grant date | Aug 4, 1998 |
| Priority date | — |
| Expiry date | Sep 26, 2016 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N21/958
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A method (500) for inspecting anomalies, which are likely defects of several types, namely, particles on the surface, scratches into surface, and defects in bulk material, is provided. This inspection method involves two types of illumination, which can be used separately or together. These two types highlight anomalies sufficiently differently to enable the defect monitoring tool to distinguish between defect type and defect location along an inspection axis. The illumination methods are direct internal side illumination (114) where the plate is used as light pipe, and external front-side illumination (117). In direct internal side illumination, a fiber optic feed (115) with flared end arranged as a line source is abutted to an edge (123) of the plate (102). In external side illumination, the source is light directed at an acute angle, preferably a grazing angle, to one of the surfaces (121). Anomalies such as dust particles on the illuminated surface will scatter light much more efficiently with external front-side illumination, than direct internal side lighting, since particles on the surface would otherwise scatter light only through weak evanescent coupling via the internal s…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.