Ultrasonic-based material analysis using an annular impulse beam
US5793489A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Feb 14, 1997 |
| Grant date | Aug 11, 1998 |
| Priority date | — |
| Expiry date | Feb 14, 2017 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01S5/02255
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
Disclosed herein is an interferometric-based materials analysis system (10) that employs a novel combination of laser beam shaping and pointing techniques, the use of a low cost, rugged, and compact diode laser (22) as a detection laser, and the use of signal processing techniques that compensate for inherent instabilities and short-term drift in the diode laser. A matched filter processing technique is disclosed for processing interferometrically-obtained data points from a target being analyzed. The matched filter technique is shown to be especially useful for detecting and analyzing Lamb modes within thin targets, such as a silicon wafer undergoing a rapid thermal processing cycle. Also disclosed is a method and apparatus for interferometrically monitoring a target to determine, in accordance with predetermined criteria, an occurrence of a period of time that is optimum for obtaining a data point. In response to detecting such a period an impulse source, such as an impulse laser (14), is triggered to launch an elastic wave within the target so that a data point can be obtained. A plurality of data points so obtained are subsequently processed, such as by the matched filter techn…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.