Patent US1827571A successfully refreshed from Google Patents.
EP0119844A2
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EP
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Measuring apparatus utilizing spectrum profile
Assignee: Fujitsu Ltd
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Filing: 1984-03-16
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Granted: —
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Expires: 2004-03-16
Abstract
Abstract Measuring or imaging of a characteristic of the structure of a medium is carried out utilizing the power spectrum profile of a received signal wave, which is derived from an incident beam pulse applied to the medium after travelling through the medium by transmission and reflection. The received signal wave is processed to obtain its cepstrum, which is filtered to separate slowly varying cepstra (including a desired Gaussian shaped pulse signal) from fast varying cepstra. The filtered cepstrum is subject to a further Fourier transformation to eliminate the effects of line cepstra in a lower frequency region and to eliminate the effects of the frequency dependence of reflecting indices of the structure. The target power spectrum is recovered by a series of inverse transformations. Correction apparatus utilizing momenta of the distored power spectrum to obtain the target Gaussian shaped profile is disclosed.
Inventors
- 👤 Hirohide Miwa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-23 08:10
CPC Classifications
G; G01; G01N; G01N29/00; G01N29/44; G01N29/4463; G01N29/04; G01N29/07; G01N29/34; G01N29/341; G01N29/343; G01N29/348; G01S; G01S15/00; G01S15/88; G01S15/89; G01S15/8906; G01S15/8977; G01S7/00; G01S7/02; G01S7/28; G01S7/285; G01S7/292; G01S7/52; G01S7/52017; G01S7/52023; G01S7/52025; G01S7/52026; G01S7/52036; G01N2291/00; G01N2291/02; G01N2291/028; G01N2291/02854; G01S7/52077
Claims Analysis
Total Claims: 13
Claim 1
Independent Claim
100 words
An apparatus utilizing the spectrum profile of a received signal wave, derived from an incident pulse signal, which may be sonic, e.g. ultrasonic, or electromagnetic, after transmission through or reflection in an object, to measure a characteristic of the object, having signal processing means comprising: means for deriving the cepstrum,of the received signal wave; filtering means for separating line-like rapidly varying cepstrum components from slowly varying cepstrum components contained in the derived cepstrum; means for recovering a power spectrum at least from said separated slowly varying cepstrum components; and means for extracting the said characteristic from the recovered power spectrum.
Claim 2
Independent Claim
100 words
An apparatus utilizing the spectrum profile of a received signal wave, derived from an incident pulse signal, which may be sonic, e.g. ultrasonic, or electromagnetic, after transmission through or reflection in an object, to measure a characteristic of the object, having signal processing means comprising: means for deriving the cepstrum,of the received signal wave; filtering means for separating line-like rapidly varying cepstrum components from slowly varying cepstrum components contained in the derived cepstrum; means for recovering a power spectrum at least from said separated slowly varying cepstrum components; and means for extracting the said characteristic from the recovered power spectrum.
Claim 3
Dependent Claim
47 words
Apparatus as claimed in claim 1, wherein the filtering means comprise: means for low-pass filtering the cepstrum, with a cut-off set to pass the slowly varying cepstrum components, mainly originating from the incident pulse waveform, and reject the rapidly varying line-like cepstrum components, originating from pulse overlap.
Claim 4
Dependent Claim
32 words
Apparatus as claimed in claim 1, wherein the filtering means comprise means for high-pass filtering the cepstrum, to reject the slowly varying cepstrum components and to pass the rapidly varying cepstrum components.
Claim 5
Dependent Claim
28 words
Apparatus as claimed in claim 1 or 2, wherein the filtering means comprise a non-linear lowpass filter, such as a median filter, to reject the line-like cepstrum components.
Claim 6
Dependent Claim
66 words
Apparatus as claimed in claim 1, or 2 or 4, wherein the means for recovering a power spectrum from the cepstrum, as processed by H omomorphic filtering with a cut off quefrency τ g , or as filtered in accordance with claim 2 or 4, comprise means for obtaining distortion indices of the power spectrum, and means for correcting the distortion by reference to said indices.
Claim 7
Dependent Claim
40 words
Apparatus as claimed in claim 5, wherein the cepstrum is processed by Homomorphic filtering with a cutoff quefrency Z set within pulse or minus 50% of the reciprocal of the doubled band-width of the spectrum of the incident pulse signal.
Claim 8
Dependent Claim
26 words
Apparatus as claimed in any preceding claim, comprising means for transmitting an incident pulse ultrasonic or electromagnetic wave signal having a Gaussian or quasi-Gaussian shaped spectrum.
Claim 9
Dependent Claim
74 words
Apparatus as claimed in any one of claims 1 to 6, comprising means for transmitting an incident pulse ultrasonic or electromagnetic wave signal of a non-Gaussian spectrum; means for approximating said non-Gaussian spectrum to a product of a Gaussian distribution and a polynominal consisting of a summation of powers of frequency; and means for processing the Gaussian component of the non-Gaussian spectrum as if it were the whole spectrum of the incident pulse signal.
Claim 10
Dependent Claim
48 words
Apparatus as claimed in any preceding claim, wherein the means for recovering a power spectrum from the processed cepstrum comprise means for estimating the center frequency of an undistorted Gaussian spectrum from the distorted recovered power spectrum with the aid of distortion indices of the recovered power spectrum.
Claim 11
Dependent Claim
71 words
Apparatus as claimed in any preceding claim, wherein the means for recovering a power spectrum of the processed cepstrum comprise: means for calculating the momenta of Oth order, first order, second order, third order and higher orders from the recovered power spectrum; and means for calculating distortion indices of the recovered power spectrum, such as center frequency, band-width, skew, those indices expressing the distortion and the correction factors using said mementa.
Claim 12
Dependent Claim
127 words
Apparatus as claimed in any preceding claim, wherein the means for recovering a power spectrum of the processed cepstrum comprise: means for correcting distortion of the recovered spectrum, providing correction from a higher order approximation (namely equations (18), (19) and (20) herein) using a table prepared to provide f - f z0 (given in equation (28)) as a function of M 2 /M 0 , M 3 / M O (given in equations (19) and (20)) said table being prepared by calculation of f a - f z0' M 2 /M 0 , M 3 /M 0 for possible combinations of p, q and associated calculated results, and performing the subtraction f z0 = f a - (f a - f z0 ) to obtain f z0.
Claim 13
Dependent Claim
50 words
Apparatus as claimed in any preceding claim, wherein the incident pulse signal is ultrasonic, further comprising: means for imaging a characteristic of biological tissue such as attenuation coefficient, reflection coefficient and measures of heterogeneity; and means for displaying the characteristic image together and/or combined with a conventional B mode image.
References Cited (Backward Citations)
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