JP2004147852A - Ultrasonic measuring apparatus - Google Patents

Ultrasonic measuring apparatus Download PDF

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JP2004147852A
JP2004147852A JP2002316171A JP2002316171A JP2004147852A JP 2004147852 A JP2004147852 A JP 2004147852A JP 2002316171 A JP2002316171 A JP 2002316171A JP 2002316171 A JP2002316171 A JP 2002316171A JP 2004147852 A JP2004147852 A JP 2004147852A
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waves
wave
frequency domain
fundamental
reflected
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JP3920194B2 (en
Inventor
Norio Tagawa
憲男 田川
Tadashi Moriya
正 守屋
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Japan Science and Technology Agency
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Japan Science and Technology Agency
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Abstract

<P>PROBLEM TO BE SOLVED: To improve compression performance by separating reception signals into respective basic waves and taking correlation for the each basic wave. <P>SOLUTION: When a synthesized wave of a plurality of basic waves s<SB>1</SB>(t), s<SB>2</SB>(t) is transmitted, and a reflected wave r(t) of the transmitted ultrasonic wave is received, the received reflected wave r(t) is converted into a representation R(ω) in a frequency domain by Fourier transformation 210. Reflected waves R<SB>1</SB>(ω), R<SB>1</SB>(ω) for the basic waves of the frequency representation are acquired by dividing the reflected wave R(ω) as the frequency domain representation by H<SB>1</SB>(ω), H<SB>2</SB>(ω) obtained from a spectral ratio in the frequency domain between different basic waves. After the reflected waves r<SB>1</SB>(t), r<SB>2</SB>(t) of the basic waves are obtained from the reflected waves R<SB>1</SB>(ω), R<SB>1</SB>(ω) corresponding to the basic waves of the frequency representation by inverse Fourier transformation 232, 234, compressed reception signals w<SB>1</SB>(t), w<SB>2</SB>(t) are acquired from the reflected waves r<SB>1</SB>(t), r<SB>2</SB>(t) of the basic waves by correlation 242, 244 with the basic waves. <P>COPYRIGHT: (C)2004,JPO

Description

【0001】
【発明の属する技術分野】
本発明は、超音波を用いて計測を行う分野に関する。
【技術的背景】
超音波を送信し、その反射波を受信することにより、反射した物体の画像を表示することは、例えば、医療の分野でよく行われている。
超音波による画像化手法の1つである、パルス圧縮方式に基づく画像化法では、送信系の物理的条件や、スタンドオフ領域の制限、あるいはドップラ計測の実現などの理由により、時間幅が狭く、かつ情報量の多い送信信号を用いる必要がある。ただし、圧縮性能(圧縮後のパルス幅や、サイドローブレベル、SN比等)も重視されることから、性能の保証されている基本的な符号化波形を足し合わせて合成送信信号とすることが多い。ダウンチャープ信号とアップチャープ信号を用いたものとして、例えば、特許文献1がある。
【0002】
さて、合成送信信号が周波数帯域の異なる基本波を足し合わせたものであれば、受信信号を各周波数帯域に基づいて容易に分離できる。しかし、例えば、アップチャープとダウンチャープ、あるいは位相の異なるチャープを足し合わせた合成送信信号を用いる場合は、周波数帯域に基づく受信信号の分離ができない。
この場合の圧縮処理として、合成送信信号が対象物体から反射されて戻ってくる受信信号に対して、合成送信信号による相関計算を行ったのでは、通常、単一の基本波を送信信号として用いたときよりも圧縮性能が劣化する。したがって、各基本波による圧縮処理を行い、得られる複数の圧縮信号に対して適切な処理を施すことによって、圧縮性能の向上を目指すことが考えられる。
【特許文献1】
特開2002−136522号公報
【0003】
【発明が解決しようとする課題】
本発明の目的は、超音波の合成送信信号を送信し、その反射波を受信するパルス圧縮方式の計測器において、受信信号を、各基本波に劣化することなく分離を行うことができるようにして、各基本波ごとの圧縮受信信号を得ることにより、計測精度を高めた計測器を提供しようとするものである。
【0004】
【課題を解決するための手段】
上記目的を達成するために、本発明は、複数の基本波を送信し、その反射波を受信し、圧縮して測定を行う超音波測定装置であって、複数の基本波からなる超音波を送信する超音波送信手段と、送信された超音波の反射波を受信する超音波受信手段と、前記受信した反射波を周波数領域での表現とするフーリエ変換手段と、前記周波数領域表現とした反射波から、異なる基本波間の周波数領域のスペクトル比を用いて、周波数表現の基本波の反射波を求める分離手段と、前記周波数表現の基本波に対応した反射波から、基本波の反射波を求める逆フーリエ変換手段と、前記基本波の反射波から、圧縮受信信号を得る基本波との相関手段とを備えることを特徴とする。
前記複数の基本波をs(j)(t)(j=1,2,・・・,M)、その周波数領域の表現をS(j)(ω)とし、受信した反射波をr(t)、その周波数領域の表現をR(ω)、周波数領域の基本波の反射波をR(j)(ω)としたとき、
前記異なる基本波間の周波数領域のスペクトル比は、
【数6】

Figure 2004147852
であり、
前記分離手段は、H(j)(ω)=1+G(j)(ω)とすると、
【数7】
Figure 2004147852
により行うことができる。
【0005】
また、前記複数の基本波を初期位相の異なる複数のアップ/ダウンチャープとして階層的に用い、複数のアップチャープ信号をsu(j)(t)(j=1,2,・・・,M)、複数のダウンチャープ信号をsd(j)(t)(j=1,2,・・・,M)、その周波数領域の表現をSu(j)(ω),Sd(j)(ω)とし、受信した反射波をr(t)、その周波数領域の表現をR(ω)、周波数領域の基本波の反射波をRu(j)(ω),Rd(j)(ω)としたとき、
前記異なる基本波間の周波数領域のスペクトル比は、
【数8】
Figure 2004147852
および
【数9】
Figure 2004147852
(Gu,はjに対して不変)であり、
前記分離手段は、Hu(j)(ω)=Gu(j)(ω)+1,H(ω)=G(ω)+1およびHd(j)(ω)=Gd(j)(ω)+1,H(ω)=G(ω)+1とすると、
【数10】
Figure 2004147852
により行うことができる。
【0006】
【発明の実施の形態】
本発明の実施の形態を、図面を参照して説明する。
本発明では、パルス圧縮方式において、異なる基本波形間の周波数領域における比(スペクトル比)を利用して、周波数帯域による基本波成分の分離が困難な場合に、それを実現する方法を与える。
図1は、本発明の実施形態である超音波測定装置の構成を示すブロック図である。図1は計測器の特に受信部における分離圧縮フィルタ200を示している。
図1において、今、基本信号発生器112,114からの2つの基本波s(t),s(t)を合成器120により足し合わせて作成した、合成送信信号s(t)(パルス)を超音波振動子130から対象物140に対して送信する場合を考える。
【数11】
Figure 2004147852
この関係を、フーリエ変換により周波数領域で表現すると
【数12】
Figure 2004147852
となる。ここで、次の比を計算する。
【数13】
Figure 2004147852
次に、反射体がN個存在するときの、式(1)の送信信号に対する反射(受信)信号r(t)を考えると、反射体142,144,146を区別する添字を iとして
【数14】
Figure 2004147852
となる。
【0007】
図1の分離圧縮フィルタ200において、受信信号r(t)をフーリエ変換器210で、周波数領域における表現にすると、
【数15】
Figure 2004147852
となる。ここで、適当な基本波を用いると、以下の関係と成る。
【数16】
Figure 2004147852
このとき、H(ω)=1+G(ω)とすると、式(5)は、
【数17】
Figure 2004147852
と書ける。この関係から、H(ω)が0となるωが測度ゼロの集合であれば、そのようなωでの成分はゼロとおき、それ以外の成分について
【数18】
Figure 2004147852
と、除算器222によりH(ω)で除算することで、基本波s(t)に対応する周波数表現の反射波R(ω)を求めることができる。これを逆フーリエ変換器232で時間表現のr(t)とし、基本波としてアップ/ダウンチャープ信号を用いた場合等の必要なときに相関器242で基本波s(t)との相関をとると、圧縮受信信号w(t)となる。
同様にH(ω)を求めることにより、基本波s(t)に対する圧縮受信信号w(t)を求めることができる。
【0008】
上述では、基本波を2つの場合で説明したが、一般的に複数の基本波を用いた場合でも適用することができる。
この場合、複数の基本波をs(j)(t)(j=1,2,・・・,M)とし、その周波数領域の表現をS(j)(ω)とすると、上述の比であるG(j)(ω)は、
【数19】
Figure 2004147852
で求めることができる。これにより、H(j)(ω)=1+G(j)(ω)とすると、
【数20】
Figure 2004147852
により、各基本波の受信信号を上述と同様に求めることができ、各基本波に対応する圧縮受信信号r(j)(t)は、上述と同様に求めることができる。
【0009】
また、階層的に、初期位相の異なる複数のアップ/ダウンチャープを足し合わせた送信信号を用いた場合でも適用可能である。図2(a)にアップチャープ信号、図2(b)にダウンチャープ信号を示す。図2(a)に示すように、アップチャープ信号は時間Tの間に周波数fがΔf上昇してfとなる。図2(b)に示すように、ダウンチャープ信号は時間Tの間に周波数fがΔf下降してfとなる。
アップとダウンを区別する添字をu,d、初期位相を区別する添字をj(=1,2,…,M)とすると、
【数21】
Figure 2004147852
および
【数22】
Figure 2004147852
(Gu,はjに対して不変)から、Hu(j),HおよびHd(j),Hを前述と同様に定義することで、
【数23】
Figure 2004147852
として各成分を分離できる。
【0010】
【実施例】
図3〜図5に、アップチャープ信号とダウンチャープ信号の2つの基本信号を送信した例を示す。図3は、合成送信信号s(t)(送信周波数19〜22MHz,パルス幅100μsを、媒質内(媒質内音速1500m/s)に距離をおいて設置している3つの反射体A,B,C(反射率はそれぞれ、0.5,0.1,0.5)に対して送信し、各反射体からの反射波r(t)を受けていることを示している。
図4は、受けた反射波を示しており、図5(a),図5(b)は、図1に示した構成で、上述のアップチャープ,ダウンチャープ信号の場合のように求めた圧縮受信信号w(t),w(t)を示している。図5(a),図5(b)に示すように分離されて、圧縮受信信号w(t),w(t)が求められる。図5から分かるように、圧縮受信信号w(t),w(t)には、各反射体A,B,Cからの反射が同じように明確に認められる。
【0011】
【発明の効果】
本発明の分離圧縮フィルタの構成を用いることにより、周波数の重なった送信チャープ信号でも、明確に分離することができ、複数の送信信号を用いることにより、得られる情報量を増加させることで、S/N比を増加することができる。したがって、例えば、超音波の反射により画像を生成する場合でも、明瞭な画像を得ることができる。
【図面の簡単な説明】
【図1】本発明の実施形態である超音波測定器の構成を示すブロック図である。
【図2】アップチャープ波、ダウンチャープ波を示す図である。
【図3】実施例における反射体等を示す図である。
【図4】実施例における反射波(受信波)を示す図である。
【図5】実施例における圧縮受信波を示す図である。
【符号の説明】
112,114 基本信号発生器
120 合成器
130 超音波振動子(超音波送受信器)
140 反射体(測定対象)
200 分離圧縮フィルタ
210 フーリエ変換器
222,224 除算器
232,234 逆フーリエ変換器
242,244 相関器[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to the field of performing measurement using ultrasonic waves.
[Technical background]
Displaying an image of a reflected object by transmitting an ultrasonic wave and receiving a reflected wave thereof is often performed, for example, in the medical field.
In the imaging method based on the pulse compression method, which is one of the imaging methods using ultrasonic waves, the time width is narrow due to the physical conditions of the transmission system, the limitation of the stand-off area, or the realization of Doppler measurement. In addition, it is necessary to use a transmission signal having a large amount of information. However, since the compression performance (pulse width after compression, side lobe level, SN ratio, etc.) is also emphasized, it is possible to add a basic coded waveform whose performance is guaranteed to form a combined transmission signal. Many. As an example using a down-chirp signal and an up-chirp signal, there is, for example, Patent Document 1.
[0002]
By the way, if the combined transmission signal is obtained by adding the fundamental waves having different frequency bands, the reception signal can be easily separated based on each frequency band. However, for example, when a combined transmission signal obtained by adding up chirp and down chirp or chirps having different phases is used, it is not possible to separate the received signal based on the frequency band.
As a compression process in this case, if a correlation calculation based on the synthesized transmission signal is performed on the received signal that is returned by reflecting the synthesized transmission signal from the target object, a single fundamental wave is generally used as the transmission signal. Compression performance is worse than when Therefore, it is conceivable to improve the compression performance by performing compression processing using each fundamental wave and performing appropriate processing on a plurality of obtained compressed signals.
[Patent Document 1]
JP-A-2002-136522
[Problems to be solved by the invention]
SUMMARY OF THE INVENTION An object of the present invention is to provide a pulse compression measuring instrument that transmits a synthesized transmission signal of an ultrasonic wave and receives a reflected wave thereof, so that the received signal can be separated without deteriorating into each fundamental wave. It is an object of the present invention to provide a measuring instrument with improved measurement accuracy by obtaining a compressed reception signal for each fundamental wave.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the present invention is an ultrasonic measurement device that transmits a plurality of fundamental waves, receives reflected waves thereof, compresses and measures, and transmits an ultrasonic wave composed of a plurality of fundamental waves. Ultrasonic transmitting means for transmitting, ultrasonic receiving means for receiving a reflected wave of the transmitted ultrasonic wave, Fourier transform means for expressing the received reflected wave in a frequency domain, and reflection in the frequency domain expression From the waves, using the spectral ratio of the frequency domain between different fundamental waves, a separating unit for finding the reflected waves of the fundamental waves in the frequency expression, and finding the reflected waves of the fundamental waves from the reflected waves corresponding to the fundamental waves in the frequency expression An inverse Fourier transform unit is provided, and a correlation unit is provided with a fundamental wave for obtaining a compressed reception signal from a reflected wave of the fundamental wave.
The plurality of fundamental waves is represented by s (j) (t) (j = 1, 2,..., M), its frequency domain is represented by S (j) (ω), and the received reflected wave is represented by r (t) ), The expression in the frequency domain is R (ω), and the reflected wave of the fundamental wave in the frequency domain is R (j) (ω),
The spectral ratio of the frequency domain between the different fundamental waves,
(Equation 6)
Figure 2004147852
And
When the separation means sets H (j) (ω) = 1 + G (j) (ω),
(Equation 7)
Figure 2004147852
Can be performed.
[0005]
Further, the plurality of fundamental waves are hierarchically used as a plurality of up / down chirps having different initial phases, and a plurality of up chirp signals are represented by su (j) (t) (j = 1, 2,..., M ), A plurality of down-chirp signals are represented by s d (j) (t) (j = 1, 2,..., M), and their frequency domain expressions are represented by S u (j) (ω) and S d (j). (Ω), the received reflected wave is r (t), its frequency domain expression is R (ω), and the fundamental wave reflected wave in the frequency domain is R u (j) (ω), R d (j) ( ω)
The spectral ratio of the frequency domain between the different fundamental waves,
(Equation 8)
Figure 2004147852
And [Equation 9]
Figure 2004147852
(G u, G d are invariant with respect to j).
The separating means includes Hu (j) (ω) = Gu (j) (ω) +1, Hu (ω) = Gu (ω) +1 and Hd (j) (ω) = Gd (j ) (Ω) +1, H d (ω) = G d (ω) +1,
(Equation 10)
Figure 2004147852
Can be performed.
[0006]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiments of the present invention will be described with reference to the drawings.
According to the present invention, a method is provided in which, in a pulse compression system, when it is difficult to separate a fundamental wave component by a frequency band using a ratio (spectral ratio) in a frequency domain between different fundamental waveforms, it is realized.
FIG. 1 is a block diagram illustrating a configuration of an ultrasonic measurement device according to an embodiment of the present invention. FIG. 1 shows a separate compression filter 200 in the measuring instrument, particularly in the receiving section.
In FIG. 1, a combined transmission signal s (t) (pulse) created by adding two fundamental waves s 1 (t) and s 2 (t) from the fundamental signal generators 112 and 114 by the combiner 120. ) Is transmitted from the ultrasonic transducer 130 to the object 140.
[Equation 11]
Figure 2004147852
Expressing this relationship in the frequency domain by Fourier transform,
Figure 2004147852
It becomes. Here, the following ratio is calculated.
(Equation 13)
Figure 2004147852
Next, considering the reflection (reception) signal r (t) for the transmission signal of Equation (1) when there are N reflectors, the subscript that distinguishes the reflectors 142, 144, and 146 is i and 14]
Figure 2004147852
It becomes.
[0007]
In the separation compression filter 200 of FIG. 1, when the received signal r (t) is expressed in the frequency domain by the Fourier transformer 210,
[Equation 15]
Figure 2004147852
It becomes. Here, when an appropriate fundamental wave is used, the following relationship is obtained.
(Equation 16)
Figure 2004147852
At this time, if H 1 (ω) = 1 + G 1 (ω), the equation (5) becomes
[Equation 17]
Figure 2004147852
Can be written. From this relationship, if ω at which H 1 (ω) becomes 0 is a set of zero measures, the component at such ω is set to zero, and the other components are expressed as
Figure 2004147852
When, by the divider 222 is divided by H 1 (ω), it can be obtained reflected wave R 1 (ω) of the frequency representation corresponding to the fundamental wave s 1 (t). This is taken as r 1 (t) in time representation by the inverse Fourier transformer 232, and when necessary, such as when an up / down chirp signal is used as the fundamental wave, the correlator 242 correlates with the fundamental wave s 1 (t). Then, a compressed reception signal w 1 (t) is obtained.
Similarly, by obtaining H 2 (ω), the compressed received signal w 2 (t) for the fundamental wave s 2 (t) can be obtained.
[0008]
In the above description, the case where two fundamental waves are used has been described. However, in general, the present invention can be applied to a case where a plurality of fundamental waves are used.
In this case, assuming that a plurality of fundamental waves are s (j) (t) (j = 1, 2,..., M) and the frequency domain expression is S (j) (ω), One G (j) (ω) is
[Equation 19]
Figure 2004147852
Can be obtained by Thus, if H (j) (ω) = 1 + G (j) (ω),
(Equation 20)
Figure 2004147852
Thus, the received signal of each fundamental wave can be obtained as described above, and the compressed received signal r (j) (t) corresponding to each fundamental wave can be obtained as described above.
[0009]
Further, the present invention can be applied even when a transmission signal obtained by adding up / down chirps having different initial phases hierarchically is used. FIG. 2A shows an up-chirp signal, and FIG. 2B shows a down-chirp signal. As shown in FIG. 2 (a), the frequency f 1 is f 2 rises Δf between the up-chirp signal time T. As shown in FIG. 2 (b), the frequency f 2 is f 1 and Δf lowered during the down-chirp signal is a time T.
If the suffix for distinguishing up and down is u, d and the suffix for distinguishing initial phase is j (= 1, 2,..., M),
(Equation 21)
Figure 2004147852
And
Figure 2004147852
(G u, G d are invariant to j) , H u (j) , H u and H d (j) , H d are defined in the same manner as described above.
(Equation 23)
Figure 2004147852
Can be used to separate each component.
[0010]
【Example】
3 to 5 show examples in which two basic signals, an up-chirp signal and a down-chirp signal, are transmitted. FIG. 3 shows three reflectors A, B, which are provided with a combined transmission signal s (t) (transmission frequency 19 to 22 MHz, pulse width 100 μs) at a distance in a medium (sound speed in the medium 1500 m / s). C (reflectances are 0.5, 0.1, and 0.5, respectively), indicating that reflected waves r (t) from each reflector are received.
FIG. 4 shows the received reflected wave, and FIGS. 5A and 5B show the configurations shown in FIG. 1 and the compression obtained as in the case of the up-chirp and down-chirp signals described above. The received signals w 1 (t) and w 2 (t) are shown. The compressed received signals w 1 (t) and w 2 (t) are separated as shown in FIGS. 5A and 5B. As can be seen from FIG. 5, the reflections from each of the reflectors A, B, and C are similarly clearly recognized in the compressed reception signals w 1 (t) and w 2 (t).
[0011]
【The invention's effect】
By using the configuration of the separation and compression filter of the present invention, it is possible to clearly separate even transmission chirp signals having overlapping frequencies, and by using a plurality of transmission signals to increase the amount of information obtained, / N ratio can be increased. Therefore, for example, even when an image is generated by reflection of ultrasonic waves, a clear image can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of an ultrasonic measuring device according to an embodiment of the present invention.
FIG. 2 is a diagram illustrating an up-chirp wave and a down-chirp wave.
FIG. 3 is a diagram showing a reflector and the like in the embodiment.
FIG. 4 is a diagram illustrating a reflected wave (received wave) in the example.
FIG. 5 is a diagram showing a compressed reception wave in the embodiment.
[Explanation of symbols]
112, 114 Basic signal generator 120 Synthesizer 130 Ultrasonic transducer (ultrasonic transceiver)
140 reflector (measurement target)
200 Separation / compression filter 210 Fourier transformers 222, 224 Dividers 232, 234 Inverse Fourier transformers 242, 244 Correlator

Claims (3)

複数の基本波を送信し、その反射波を受信し、圧縮して測定を行う超音波測定装置であって、
複数の基本波からなる超音波を送信する超音波送信手段と、
送信された超音波の反射波を受信する超音波受信手段と、
前記受信した反射波を周波数領域での表現とするフーリエ変換手段と、
前記周波数領域表現とした反射波から、異なる基本波間の周波数領域のスペクトル比を用いて、周波数表現の基本波の反射波を求める分離手段と、
前記周波数表現の基本波に対応した反射波から、基本波の反射波を求める逆フーリエ変換手段と、
前記基本波の反射波から、圧縮受信信号を得る基本波との相関手段と
を備えることを特徴とする超音波測定装置。
An ultrasonic measurement device that transmits a plurality of fundamental waves, receives the reflected waves, compresses and measures,
Ultrasonic transmission means for transmitting ultrasonic waves composed of a plurality of fundamental waves,
Ultrasound receiving means for receiving a reflected wave of the transmitted ultrasonic wave,
Fourier transform means to represent the received reflected wave in the frequency domain,
From the reflected waves in the frequency domain representation, using a spectral ratio of the frequency domain between different fundamental waves, a separating unit that determines the reflected waves of the fundamental waves in the frequency representation,
From the reflected wave corresponding to the fundamental wave of the frequency expression, an inverse Fourier transform means for obtaining a reflected wave of the fundamental wave,
An ultrasonic measurement device comprising: a correlation unit for obtaining a compressed reception signal from a reflected wave of the fundamental wave with a fundamental wave.
請求項1に記載の超音波測定装置において、
前記複数の基本波をs(j)(t)(j=1,2,・・・,M)、その周波数領域の表現をS(j)(ω)とし、受信した反射波をr(t)、その周波数領域の表現をR(ω)、周波数領域の基本波の反射波をR(j)(ω)としたとき、
前記異なる基本波間の周波数領域のスペクトル比は、
Figure 2004147852
であり、
前記分離手段は、H(j)(ω)=1+G(j)(ω)とすると、
Figure 2004147852
により行うことを特徴とする超音波測定装置。
The ultrasonic measurement device according to claim 1,
The plurality of fundamental waves is represented by s (j) (t) (j = 1, 2,..., M), its frequency domain is represented by S (j) (ω), and the received reflected wave is represented by r (t) ), The expression in the frequency domain is R (ω), and the reflected wave of the fundamental wave in the frequency domain is R (j) (ω),
The spectral ratio of the frequency domain between the different fundamental waves,
Figure 2004147852
And
When the separation means sets H (j) (ω) = 1 + G (j) (ω),
Figure 2004147852
An ultrasonic measurement device characterized by performing the following.
請求項1に記載の超音波測定装置において、
前記複数の基本波を初期位相の異なる複数のアップ/ダウンチャープとして階層的に用い、複数のアップチャープ信号をsu(j)(t)(j=1,2,・・・,M)、複数のダウンチャープ信号をsd(j)(t)(j=1,2,・・・,M)、その周波数領域の表現をSu(j)(ω),Sd(j)(ω)とし、受信した反射波をr(t)、その周波数領域の表現をR(ω)、周波数領域の基本波の反射波をRu(j)(ω),Rd(j)(ω)としたとき、
前記異なる基本波間の周波数領域のスペクトル比は、
Figure 2004147852
および
Figure 2004147852
(Gu,はjに対して不変)であり、
前記分離手段は、Hu(j)(ω)=Gu(j)(ω)+1,H(ω)=G(ω)+1およびHd(j)(ω)=Gd(j)(ω)+1,H(ω)=G(ω)+1とすると、
Figure 2004147852
により行うことを特徴とする超音波測定装置。
The ultrasonic measurement device according to claim 1,
The plurality of fundamental waves are hierarchically used as a plurality of up / down chirps having different initial phases, and a plurality of up chirp signals are represented by su (j) (t) (j = 1, 2,..., M); A plurality of down-chirp signals are represented by s d (j) (t) (j = 1, 2,..., M), and their frequency domain expressions are represented by S u (j) (ω) and S d (j) (ω ), R (t) is the received reflected wave, R (ω) is its frequency domain expression, and R u (j) (ω), R d (j) (ω) are the reflected waves of the fundamental wave in the frequency domain. And when
The spectral ratio of the frequency domain between the different fundamental waves,
Figure 2004147852
and
Figure 2004147852
(G u, G d are invariant with respect to j).
The separating means includes Hu (j) (ω) = Gu (j) (ω) +1, Hu (ω) = Gu (ω) +1 and Hd (j) (ω) = Gd (j ) (Ω) +1, H d (ω) = G d (ω) +1,
Figure 2004147852
An ultrasonic measurement device characterized by performing the following.
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