Ultrasonic system for measurement of thin layers
US5513531A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Sep 1, 1993 |
| Grant date | May 7, 1996 |
| Priority date | — |
| Expiry date | Sep 1, 2013 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N2291/0421
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
To improve and simply ultrasonic measurement of thin layers, an adaptive least-mean-square (LMS) implementation of a Wiener filter is used to deconvolve ultrasonic waveforms. This filter is structured as a finite-impulse-response (FIR) filter and solved using Widrow's adaptive linear combiner. The filter is implemented on a microcomputer with gating features for automated signal peak identification and measurement. The deconvolution process begins by assuming an impulse (the desired response) to a known input (the ultrasonic response). A transfer function is then determined that, when convolved with the response, results in the assumed impulse. The transfer function in this case is a long FIR filter typically requiring up to 128 taps to achieve acceptable results.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.