Contactless acoustic sensing system with detector array scanning and self-calibration
US6087652A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jul 12, 1999 |
| Grant date | Jul 11, 2000 |
| Priority date | — |
| Expiry date | Jul 12, 2019 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG01N29/2418
- WIPO fieldMeasurement
- WIPO sectorInstruments
Abstract
A contactless system for imaging an acoustic source within a workpiece directs a preferably annular optical probe beam pattern onto the vibrating workpiece surface, with the vibrationally modulated beam then detected by an array of preferably non-steady-state photo-emf detectors arranged in a similar pattern. The probe beam is scanned over the vibrating surface, either mechanically or through an electronically simulated phased array scheme. Time gating is used to suppress unwanted side-lobes when the individual detector outputs are summed over an appreciable waveband. A self-calibration scheme is also preferably used that provides a quantitative as well as qualitative output. A calibration modulation is imposed on at least one of the probe and reference beams, with the calibration modulation later removed at a post-detector stage and used to normalize the acoustic modulation output. Variations of the self-calibration scheme include reference-beam and time-delay interferometers based upon a calibrating phase modulation, and a photon flux measurement approach based upon a calibrating amplitude modulation.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.