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US 5,513,531 AGranted
Ultrasonic system for measurement of thin layers
AssigneeCombustion Engineering, Inc.
InventorsMark A. Sapia, David S. Leonard
Life of this patent
Estimating the term…
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.
Claims18
An apparatus for measuring films located on a test member comprising:
- a transducer for providing an ultrasonic impulse to the test member;
- detection means for detecting ultrasonic signals transferred through the test member, said detection means providing data signals indicative of said ultrasonic signals;
- filtering means for providing a filtered time-based deconvolved waveform based on data signals provided by the detection means, said filtering means including processing means for applying a finite-impulse-response (FIR) filter to a waveform based on said data signals provided by the detection means;
- and
- measurement means for providing a measurement of the test member based on the deconvolved waveform, said measurement means including gate means for identifying portions of the filtered time-based deconvolved waveform corresponding to a backwall of the test member and a backwall of a film located on the test member, whereby the thickness of the film may be measured;
- wherein said gate means includes a reference gate for identifying a portion of the filtered time-based deconvolved waveform corresponding to the backwall of the test member, and a measurement gate for identifying a portion of the filtered time-based deconvolved waveform corresponding to the backwall of the film.
3 more elements
An apparatus for measuring films located on a test member comprising:
- a transducer for providing an ultrasonic impulse to the test member;
- detection means for detecting ultrasonic signals transferred through the test member, said detection means providing data signals indicative of said ultrasonic signals;
- filtering means for providing a filtered time-based deconvolved waveform based on data signals provided by the detection means;
- and
- measurement means for providing a measurement of the test member based on the deconvolved waveform, said measurement means including gate means for identifying portions of the filtered time-based deconvolved waveform corresponding to a backwall of the test member and to a backwall of a film located on the test member, whereby the thickness of the film may be measured;
- wherein said gate means includes a reference gate for identifying a portion of the filtered time-based deconvolved waveform which corresponds to the backwall of the test member, and a measurement gate for identifying a portion of the filtered time-based deconvolved waveform which is associated with a backwall of the film;
- and
- wherein said measurement gate floats relative to said reference gate.
5 more elements
A method of measuring films located on a test member comprising:
- providing an ultrasonic impulse to the test member with a transducer;
- detecting ultrasonic signals transferred through the test member;
- providing data signals indicative of said ultrasonic signals to a processing apparatus;
- deconvolving in said processing apparatus a filtered time-based waveform based on data signals provided by the detection means;
- and
- displaying a measurement of the test member based on the filtered waveform;
- wherein the step of deconvolving includes applying a finite-impulse-response (FIR) filter to a waveform based on said data signals provided by the detection means;
- and
- wherein said method further includes the steps of identifying a portion of the deconvolved waveform corresponding to a backwall of the test member, and identifying a portion of the deconvolved waveform corresponding to a backwall of a film located on the test member, whereby the thickness of the film may be measured;
- and
- wherein the step of identifying a portion of the deconvolved waveform corresponding to the backwall of the test member utilizes a reference gate, and wherein the step of identifying a portion of the deconvolved waveform corresponding to the backwall of the film utilizes a measurement gate.
8 more elements
A method of measuring films located on a test member comprising:
- providing an ultrasonic impulse to the test member with a transducer;
- detecting ultrasonic signals transferred through the test member;
- providing data signals indicative of said ultrasonic signals to a processing apparatus;
- deconvolving in said processing apparatus a filtered time-based waveform based on data signals provided by the detection means;
- and
- displaying a measurement of the test member based on the filtered waveform;
- wherein said method further includes the steps of identifying a portion of the deconvolved waveform corresponding to a backwall of the test member, and identifying a portion of the deconvolved waveform corresponding to a backwall of a film located on the test member, whereby the thickness of the film may be measured;
- wherein the step of identifying a portion of the deconvolved waveform corresponding to the backwall of the test member utilizes a reference gate, and wherein the step of identifying a peak of the deconvolved waveform corresponding to the backwall of the film utilizes a measurement gate;
- and
- wherein said measurement gate floats relative to said reference gate.
7 more elements
Dependencies are inferred from the claim text.