Optics: measuring and testing – By dispersed light spectroscopy – Utilizing a spectrometer
Patent
1997-05-01
2000-06-13
Kim, Robert H
Optics: measuring and testing
By dispersed light spectroscopy
Utilizing a spectrometer
356357, G01B 902
Patent
active
060756039
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.
REFERENCES:
patent: 4966459 (1990-10-01), Monchalin
patent: 5131748 (1992-07-01), Monchalin et al.
patent: 5546187 (1996-08-01), Pepper et al.
patent: 5684592 (1997-11-01), Mitchell et al.
O'Meara Thomas R.
Pepper David M.
Duraiswamy V. D.
Hughes Electronics Corporation
Kim Robert H
Lee Andrew H.
Sales M. W.
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