JPH0781994B2 - measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a measuring device using ultrasonic waves, electromagnetic waves, and other wave motions.

In particular, the present invention relates to a measuring device such as an ultrasonic nondestructive inspection device using a pulse compression method.

[Prior Art] This type of conventional measuring device is shown in, for example, the following documents A, B and C.

Reference A: B. Bee. Lee and E. S. Ferguson "High-speed digital Golay code flaw detection system" Minutes of The Eye Triple E Ultrasonic Symposium 1981, No. 1
Pages 888-891.

(BBLee and ES Furgason, `` High-Speed Digital G
olay Code Flaw Detection System, '' in Proceedings o
f the IEEE Ultrasonics Symposium, 1981, pp.888-89
1) Reference B: Bee. Bee. Lee and E. S. Ferguson "Evaluation of Ultrasonic N.D.E Correlation Testing System" Sonic and Ultrasonic Eye Triple E Bulletin vol.SU-29, no.6,
November, 1982, pages 359-369.

(BBLee and ES Furgason, `` An Evaluation of Ultr
asound NDE Correlation Flaw Detection Systems, "IEE
E Transactions on Sonics and Ultrasonics, vol.SU-2
9, no. 6, November, 1982, pp.359-369) Reference C: B. Bee. Lee and E. S. Ferguson "High Speed Digital Golay Code Flaw Detection System" Ultrasound, July, 1983, pp. 153-161.

(BBLee and ES Furgason, `` High-Speed Digital G
olay Code Flaw Detection System, '' Ultrasonics, Jul
y, 1983, pp.153-161) The configuration of the conventional example will be described with reference to FIG.

FIG. 19 is a block diagram showing a conventional measuring apparatus using ultrasonic waves shown in Document C.

Referring to FIG. 19, the conventional measuring device includes a signal source (1),
Digital delay line (2) connected to this signal source (1)
A bipolar converter (3) connected to the signal source (1) and the digital delay line (2), a transmitter (4) connected to the bipolar converter (3), and also the signal source (1) and A bipolar transducer (5) connected to the digital delay line (2), an ultrasonic probe (6), an ultrasonic probe (6), a transmitter (4) and a bipolar converter (5). An analog correlator (7) connected,
Display (8) connected to this analog correlator (7)
And a system control (9).

The ultrasonic probe (6) is installed in the water of the aquarium,
A brass Darget S is arranged at a position facing the ultrasonic probe (6). Also, analog correlator (7)
Is composed of an ultrasonic probe (6) and a multiplier (7a) connected to the bipolar converter (5), and an integrator (7b) connected to the multiplier (7a). Further, a logic circuit such as an AND gate is provided between the signal source (1) and the bipolar converters (3) and (5) and between the digital delay line (2) and the bipolar converters (3) and (5). Has been inserted. The system control (9) is connected to each device and circuit described above for controlling.

Next, the operation of the above-mentioned conventional example will be described with reference to FIGS. 20 and 21.

20 and 21 are waveform diagrams showing a transmission signal and a compressed pulse of the conventional measuring apparatus shown in the document B.

In FIG. 20, the horizontal axis is expressed in units of bits (BITS), but the unit of the horizontal axis can be read as time if the unit time is associated with the unit bit. Literature B
In, the unit time corresponding to the unit bit is represented by the symbol δ. Therefore, the pulse width of the transmission signal shown in FIG. 20 is 63 × δ.

This transmission signal is a signal whose frequency band is baseband and whose amplitude is encoded by a special sequence. The encoding of the amplitude will be described later, and the sequence used will be described first.

The sequence used is a finite length sequence with a length of 63 bits and an m sequence (maxi with a period length of 63 bits).
mal length sequence) is cut off in one cycle.

Regarding the m-sequence, for example, "Code Theory" by Hiroshi Miyagawa, Yoshihiro Iwadari and Hideki Imai, published by Shokoido on June 29, 1979, No. 474.
Pages to 499 (hereinafter referred to as Document D) are described in detail.

The m-sequence is a periodic sequence having an infinite length and is a binary sequence in which the components forming the sequence are two elements. The two elements may be assigned a sign + and a sign −,
Numerical value +1 and numerical value -1, or numerical value 1 and numerical value 0 may be assigned. In the example of Fig. 20, the cycle length is 63
A finite-length sequence is created by extracting one cycle of the m-sequence having an infinite length in bits.

Next, amplitude encoding using this finite length sequence will be described.

Amplitude +1 is associated with one element of the finite length sequence, and amplitude -1 is associated with the other element, and the amplitude is modulated to a relative value ± 1 per unit time δ according to the order in which the two elements of the sequence appear. is doing. Such a signal is called a signal having a waveform whose amplitude is encoded.

In FIG. 21, as in FIG. 20, the horizontal axis is displayed in bit units, but if the unit bit is associated with the unit time δ, the horizontal axis unit can be read as time. .

This compressed pulse is an example in the case of using a transmission signal amplitude-coded by a finite length sequence having a length of 64 bits. This sequence has a length of 63 that was used when generating the transmission signal in FIG.
It is created by adding 1 bit to a finite length sequence of bits. Therefore, the pulse width of this transmitted signal is 64
Xδ. The pulse width of the echo is almost the same as this.

However, as shown in FIG. 21, most of the energy of the compressed pulse is within the central time width (several bits ×
Concentrate on δ). This central high amplitude signal portion is called the main lobe of the compressed pulse. The pulse width of the main lobe is short. This means that the energy of the echo, which was distributed almost uniformly over a time period as long as the pulse width of the transmission signal, was compressed to almost one point on the time axis. The small amplitude signal portions on either side of the main lobe are called the range side lobes of the compressed pulse.

Now, the transmission signal as shown in FIG. 20 is generated from the signal source (1) and the digital delay line (2) via the bipolar converter (3) and the transmitter (4). The ultrasonic probe (6) is driven by this transmission signal.

The ultrasonic waves emitted into the water from the ultrasonic probe (6) are reflected by the target S and are received again by the ultrasonic probe (6). The echo received by the ultrasonic probe (6) is transmitted to the multiplier (7a) of the analog correlator (7).

The pulse width of the echo described above is as long as the transmitted signal.
That is, the energy of the echo is long (corresponding to about 63 ×
δ, in the case of FIG. 21, almost evenly distributed over 64 × δ).

On the other hand, the same signal as the transmission signal is transmitted to the multiplier (7a) of the analog correlator (7) via the digital delay line (2) and the bipolar converter (5).

The analog correlator (7) performs a correlation operation between the echo and the transmitted signal. By this correlation calculation, the energy of the echo, which is distributed almost uniformly on the time axis over a long time period equivalent to that of the transmission signal, is compressed to almost one point on the time axis. The pulse obtained by being compressed is called a compressed pulse.

The compressed pulse obtained by the analog correlator (7) is transmitted to the display (8) and displayed as the final result.

The distance resolution of the above-mentioned conventional measuring device is determined by the pulse width of the main lobe of the compressed pulse (hereinafter, abbreviated as the pulse width of the compressed pulse). Although the pulse width of the transmission signal is long, the pulse width of the compressed pulse is short as described above. Therefore, originally, a resolution equivalent to that in the case of the measuring device by the pulse echo method using a transmission signal having a short pulse width can be obtained.

On the other hand, the S / N ratio (signal to noise ratio) increases as the average transmission energy of the transmission signal increases. The average transmission energy increases as the pulse width of the transmission signal increases. Therefore, the conventional measuring device can obtain a higher S / N ratio than the pulse echo method which originally uses a transmission signal having a short pulse width.

As described above, the conventional measuring device has excellent resolution and S / N
The ratio can be high.

By the way, the correlation calculation between the echo and the transmission signal is ∫s (t−τ) r (t) dt [integration range: −∞ to ∞, where r (t) and s (t) are the echo and the transmission signal. ] The calculation represented by the formula is a calculation for obtaining a new function with τ as a variable. This new function is called the correlation function and corresponds to the compressed pulse. Of course, if either the echo r (t) or the transmission signal s (t) takes a value other than zero only within a finite time range and becomes zero outside the time range, the integration range is finite. Becomes

In the conventional measuring device, as described above, the correlation calculation between the echo and the transmission signal is performed using the analog correlator (7). However, the analog correlator (7) is a multiplier (7a)
And an integrator (7b). Therefore, the operation of changing the variable τ in the equation must be performed externally. That is, the operation of delaying the transmission signal s (t) by τ is performed by the digital delay line (2) and the system control (9), and the multiplier (7a) has s (t−τ).
Is entered. This means the following:

First, the analog correlator (7) is not exactly a correlator because the operation of changing the variable τ in the equation is not performed only by the analog correlator (7). Furthermore, the time waveform of the compressed pulse (correlation function) cannot be obtained by only one transmission. That is, what is obtained from one transmission is only the value of the compressed pulse when the variable τ is fixed to a certain value. In order to obtain the time waveform of the compressed pulse, it is necessary to repeat the transmission several times while sequentially changing the variable τ.
Therefore, it takes a considerable amount of time to obtain the final result.

Another correlator for performing the correlation calculation represented by the formula will be described with reference to FIG.

FIG. 22 is a block diagram showing another correlator shown in Japanese Patent Application No. 1-45316 related to the present invention.

In FIG. 22, the correlator (10) is a tapped delay line (10
a), a plurality of multipliers (10b) connected to each output tap of the delay line with taps (10a), and an adder (10c) connected to these plurality of multipliers (10b). ing.

The correlator (10) realizes the correlation calculation by utilizing the fact that the equation can be transformed as follows. That is, the equation can be transformed as follows.

∫s (t−τ) r (t) dt [integration range: −∞ to ∞] = ∫r (t + τ) s (t) dt [integration range: −∞ to ∞] = ∫r (t + τ) s (t ) Dt [integration range: 0 to T] ≉Σr (kΔt + 1lΔt) s (kΔt) [k = 1 to K] ... where the transmission signal s (t) takes zero outside the time range of 0 to T. I am trying. Also, k and l are integers, Δt
Is a sampling interval, K is a constant, and t = kΔt, τ
= LΔt, T = KΔT.

In the correlator (10), Δt is the delay time of the delay line with taps (10a), and K is the total number of taps. When the echo r (t) is input to the tapped delay line (10a), for example, the output of the k-th tap is the weight s (kΔ
t) is multiplied by the multiplier (10b). The adder (10c) then adds the outputs of all taps and the result is equal to the above equation.

In this correlator (10), the operation of changing the variable τ is equivalent to sequentially inputting the echo r (t) in the tapped delay line (10a). The echo r (t) is naturally input from the ultrasonic probe (6) sequentially in time. Therefore, the operation of changing the variable τ is automatically performed. That is, in the correlator (10) shown in FIG. 22,
The time waveform of the compressed pulse can be obtained by only one transmission.

However, as the duration of the transmission signal becomes longer, that is, as T becomes larger, the tapped delay line (10a) having a large number of taps K is required. Along with this, a large number of multipliers (10b) are required. In addition, the adder (1
0c) also requires a large number of input terminals. As described above, as the number of multipliers (10b) increases and the number of input terminals of the adder (10c) increases, the operation speed of the correlator (10) that can be realized becomes slower. In addition, the price of the device also increases.

[Problems to be Solved by the Invention] In the conventional measuring apparatus as described above, it takes time to obtain a compressed pulse as a final result, and if it is attempted to shorten the compressed pulse to realize real-time performance, the operation speed becomes slow. There was a problem that

The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to obtain a measuring device that can be operated at high speed at low cost.

[Means for Solving the Problems] The measuring apparatus according to the present invention includes the following means.

[1] Generate a basic unit signal based on the first sequence,
Transmission signal generating means for generating a transmission signal based on the basic unit signal and the second sequence.

[2] A transmitting unit that is excited by the transmission signal and transmits a wave to an object.

[3] Receiving means for receiving the echo reflected from the object.

[4] A first correlation unit that performs a correlation process on the echo using a first reference signal generated based on the first sequence.

[5] A second correlation unit that performs a correlation process on the output of the first correlation unit by using a second reference signal generated based on the second sequence.

[Operation] In the present invention, the transmission signal generating means allows the first
The basic unit signal is generated on the basis of the sequence and the transmission signal is generated on the basis of the basic unit signal and the second sequence.

Further, the transmitting means transmits the wave motion excited by the transmission signal to the object, and the receiving means receives the echo reflected from the object.

Further, the echo is subjected to correlation processing by the first correlation means using the first reference signal generated based on the first sequence.

Then, the output of the first correlation means is subjected to correlation processing by the second correlation means using the second reference signal generated based on the second sequence.

[Embodiment] Six embodiments of the present invention will be sequentially described below.

First, the configuration of the first embodiment of the present invention will be described with reference to FIG.

FIG. 1 is a block diagram showing a first embodiment of the present invention, in which an ultrasonic probe (6) and an indicator (8) are exactly the same as those of the conventional device shown in FIG. .

In FIG. 1, the first embodiment of the present invention is exactly the same as that of the conventional apparatus described above, an amplitude-encoded transmission signal generator (1A), and this amplitude-encoded transmission signal generator (1A).
And a first correlator (1) connected to the ultrasonic probe (6)
1) and a second correlator (12) whose input side is connected to the first correlator (11) and amplitude coded transmission signal generator (1A) and whose output side is connected to the display (8), It consists of

The ultrasonic probe (6) is also connected to the amplitude-coded transmission signal generator (1A) and is in contact with the test body S.

Next, the operation of the above-described first embodiment will be described with reference to FIGS. 2 and 3.

2 and 3 are waveform charts showing the basic unit signal and the transmission signal in the first embodiment of the present invention.

The amplitude coded transmission signal generator (1A) has a first sequence {a}.
Is generated and a basic unit signal is generated using this sequence.
Also, a second sequence {p} is generated, and a transmission signal is generated from the basic unit signal and the second sequence {p} according to the procedure described below. Then, the transmission signal is transmitted to the ultrasonic probe (6).

As shown in FIG. 2, the basic unit signal has a length M of 4 as the first sequence {a}, {a} = {a ₁ , a ₂ , a ₃ , a ₄ } = {+ , +,-, +} Is adopted and the signal has a waveform in which the amplitude is coded as in the conventional case. To make the relationship between the first sequence {a} and the amplitude coding easier to understand, the sign (±) of this sequence
Is also entered in the figure. Further, in the figure, δ is a fixed time. Hereinafter, the basic unit signal is represented by g (t). However, t is time.

As shown in FIG. 3, the transmission signal has a length N of 3 as the second sequence {p}, {p} = {p ₁ , p ₂ , p ₃ } = {+, +, − }, And the basic unit signal g shown in FIG.
(T) is a signal generated according to the procedure described below. That is, the basic unit signal g (t) is assigned to the code + of the second sequence {p}, and the signal −g (t) obtained by multiplying the basic unit signal g (t) by −1 is assigned to the code −. The ± g (t) s are arranged on the time axis according to the order in which the codes of the second series {p} are assigned. Second
In order to make it easier to understand the relationship between the sign (±) of the series {p} and the signal ± g (t), the sign of the second series {p} is also entered in the figure. There is. Tp is a fixed time.

The transmission signal shown in FIG. 3 is expressed by the following equation.

_{s (t) = Σp i g} [t- (i-1) Tp] ( sum taken for i to _{1~N.) = p 1 g (} t) + p 2 g (t-Tp) + p 3 g (t −2Tp) Formula Here, the sign ± of p _i (i = 1, 2, ..., N) is regarded as the same as ± 1 (composite same order) and multiplied (the same applies hereinafter).

The ultrasonic probe (6) is driven by the transmission signal s (t) and transmits ultrasonic waves into the test body S. Then, the ultrasonic probe (6) receives the echo reflected by a reflector such as a defect in the test body S.

The echo r (t) is expressed by the following equation.

r (t) = C ₀ × ∫s (t ₁ ) h (t−t ₀ −t ₁ ) dt ₁ [integration range: −∞ to ∞] Formula Here, C ₀ represents a constant. Further, h (t) is passed from the output end of the amplitude-encoded transmission signal generator (1A) to the ultrasonic probe (6), the reflector of the test body S, and the ultrasonic probe (6) again. Then, the inverse Fourier transform of the frequency response characteristic in the signal propagation path up to the input terminal of the first correlator (11) is represented. That is, it represents the impulse response of the signal propagation path. Further, t ₀ is the time required for the ultrasonic waves to reciprocate to the reflector in the test body S.

Since the generality is not lost even if C ₀ = 1 is set, the following description will be made with C ₀ = 1.

The received echo r (t) is transmitted to the first correlator (11). On the other hand, the first reference signal used for echo correlation processing is generated by the amplitude-coded transmission signal generator (1A) and is also transmitted to the first correlator (11). First
The reference signal of is the signal associated with the first sequence {a}.
This signal is represented by ua (t).

The first correlator (11) executes a correlation calculation between the echo r (t) and the first reference signal ua (t). That is,
If the result of the correlation calculation is Ca (t), it is expressed by the following equation.

Ca (t) = ∫ua (t ₂ −t) r (t ₂ ) dt ₂ [integration range: −∞ to ∞] ... Formula Note that the result of this correlation calculation is A (t) = ∫∫ua (t ₂₋ t) g (t ₁ ) h (t ₂ −t ₁ ) dt ₁ dt ₂ [Integration range: −∞ to ∞] Speaking of expression, from expression to expression, it is equal to the following expression.

Ca (t) = Σp _i A [t−t ₀ − (i−1) Tp] (The sum is 1 to N for i.) = P ₁ A (t−t ₀ ) + p ₂ A (t−t) in _{0 -Tp) + p 3 A (} t-t 0 -2Tp) ... formula this formula, A (t-t ₀₎ is the basic unit signal g
The ultrasonic probe (6) is driven by (t), and the echo obtained at this time is used as a reference signal for the first reference signal ua.
This corresponds to a compressed pulse obtained by performing a correlation process using (t) (hereinafter referred to as a basic unit compressed pulse).

Further, from the equation, Ca (t) is arranged such that the three basic unit compression pulses A (t−t ₀ ) are shifted by 0, Tp, 2Tp on the time axis, respectively, and the second sequence {p } Component p ₁ ,
It can be seen that it is equal to the product of multiplying p ₂ and p ₃ .

Ca (t) which is the output of the first correlator (11) is transmitted to the second correlator (12). On the other hand, the second reference signal used for the correlation processing in the second correlator (12) is generated by the amplitude coding transmission signal generator (1A) and transmitted to the second correlator (12). This second reference signal is the signal associated with the second sequence {p}.

The second reference signal is represented by up (t). Second correlator (1
In 2), the correlation calculation is executed between Ca (t) which is the output of the first correlator (11) and the second reference signal up (t).
That is, if the result of this correlation calculation is C (t), the correlation calculation is expressed by the following equation.

C (t) = ∫up (t ₃ −t) Ca (t ₃ ) dt ₃ [integration range: −∞ to ∞] ... The output C (t) of the second correlator (12) is the display ( It is transmitted to 8) and displayed as before.

Here, the operating principle of the first embodiment of the present invention described above will be explained with reference to FIG. 4, FIG. 5, FIG. 6 and FIG.

FIG. 4 is a waveform diagram showing the basic unit compressed pulse of the first embodiment of the present invention, FIG. 5 is a waveform diagram showing the output signal of the first correlator (11), and FIG. 6 is the second reference signal. FIG. 7 is a waveform diagram showing an output signal (compressed pulse) of the second correlator (12).

The basic unit compression pulse A (t−t ₀ ) shown in FIG. 4 uses the signal shown in FIG. 2 as the basic unit signal g (t), and the basic unit as the first reference signal ua (t). Signal g
(T) itself is used, and h (t) is a calculation result by an equation when a delta function is used.

As shown in FIG. 4, the basic unit compression pulse A (t−t ₀ ).
Has a large amplitude (main lobe) only near t = t ₀ , and t
It can be seen that the amplitude (sidelobe level) at ≠ t ₀ is small.

Output signal Ca (t) of the first correlator (11) shown in FIG.
Is the calculation result from the basic unit compression pulse A (t−t ₀ ) shown in FIG. 4 and the equation. Incidentally, Tp was set to 6δ.
As shown in FIG. 5, the output signal Ca of the first correlator (11) is
At (t), energy is dispersed on the time axis. Thus, the dispersion of energy on the time axis is Tp
Does not change even if is changed from 6δ.

However, the output signal Ca (t) of the first correlator (11) is
By performing the correlation processing by the correlator (12), the output signal Ca (t) of the first correlator (11) can be compressed as shown below.

For this, the second sequence {p} as the second reference signal
The signal shown in FIG. 6 invented by using will be described.

The signal shown in FIG. 6 is a signal having a waveform in which the amplitude is encoded using the second sequence {p}. In order to facilitate understanding of the relationship between this signal and the code of the second sequence {p}, the code of the second sequence {p} is also shown in the figure.

When the second reference signal up (t) shown in FIG. 6 is used, C
(T) is as follows from the equation.

C (t) = Σp _i Ca [t + (i−1) Tp] (The sum is 1 to N for i.) = P ₁ Ca (t) + p ₂ Ca (t + Tp) + p ₃ Ca (t + 2Tp) Furthermore, let the autocorrelation function of the second sequence {p} be ρpp
Expressing (i), (i = 0, ± 1, ± 2, ..., ± (N-1)), C (t) is as follows from the equation and.

C (t) = ρpp (0) A (t−t ₀ ) + Σρpp (i) [A (t−t ₀ −iTp) + A (t−t ₀ + iT
p)] (sum taken for i to 1~N) = ρpp (0) A (t-t 0) + ρpp (1) [A (t-t 0 -Tp) + A (t-t 0 + Tp)] + ρpp (2) [A (t−t ₀ −2Tp) + A (t−t ₀ + 2Tp)] Formula From this formula, the autocorrelation function ρpp of the second sequence {p}
If (i) has a large amplitude (main lobe) at i = 0 and a small amplitude (sidelobe level) at i ≠ 0, the second and third terms on the right side of the equation are the first and second terms.
It can be seen that it is smaller than the term.

Furthermore, if the basic unit compression pulse A (t−t ₀ ) has a large amplitude (main lobe) only in the vicinity of t = t ₀ and the amplitude at t ≠ t ₀ (sidelobe level) is small, the right side of the equation is calculated. It can be seen that the first term of has a large amplitude (main lobe) only in the vicinity of t = t ₀ , and the amplitude (side lobe level) at t ≠ t ₀ becomes small. That is, it can be seen that the output Ca (t) of the first correlator (11) is compressed and the compressed pulse C (t) having a low sidelobe level is obtained.

FIG. 7 shows the compressed pulse C calculated from the equation.
(T) is shown.

In FIG. 7, the basic unit compression pulse A (t−t ₀ ) shown in FIG. 4 is used, and in the autocorrelation function ρpp (i) of the second sequence, ρpp (0) = 3, ρpp (1)
It was used that = 0 and ρpp (2) =-1. Also, Tp
= 4δ.

In FIG. 7, most of the signal energy is concentrated near t = t ₀ . That is, it can be seen that a compressed pulse having a large amplitude (main lobe) only near t = t ₀ and a small amplitude (sidelobe level) at t ≠ t ₀ is obtained.

That is, also in the first embodiment of the present invention, similarly to the conventional case, a compressed pulse having a large amplitude (main lobe) only near t = t ₀ and a small amplitude (side lobe level) at t ≠ t ₀ is generated. It turned out to be obtained.

Next, regarding the effect of the first embodiment of the present invention, FIG.
A description will be given with reference to FIGS. 9 and 10.

FIG. 8 is a waveform diagram showing a transmission signal when Tp = 4δ according to the first embodiment of the present invention, FIG. 9 is a block diagram showing the configuration of the first correlator (11), and FIG. It is a block diagram which shows the structure of the two correlators (12).

The transmission signal is, as shown in FIG. 8, a third sequence {+,
+,-, +, +, +,-, +,-,-, +,-} Is equivalent to a signal having a waveform whose amplitude is encoded. In addition,
The third sequence is equal to the sequence of length 12 generated from the first sequence {a} and the second sequence {p} according to the following equation.

{A ₁ p ₁ , a ₂ p ₁ , a ₃ p ₁ , a ₄ p ₁ , a ₁ p ₂ , a ₂ p ₂ , a ₃ p ₂ , a ₄ p ₂ ,
a ₁ p ₃ , a ₂ p ₃ , a ₃ p ₃ , a ₄ p ₃ } Here, the sign (±) is regarded as equivalent to ± 1, and multiplication is performed.

Now, let us consider a conventional inspection apparatus using the transmission signal shown in FIG.

The duration T of the transmission signal is 12δ according to FIG. Therefore, if K ₁ samples are taken per unit time δ and the correlator (10) shown in FIG.
Since the K = 12 × K _1, taps 12 × K ₁ single tapped delay line and (10a), 12 × K ₁ single multiplication connected to each output tap of the tapped delay line (10a) It requires an adder (10b) and an adder (10c) with 12 × K ₁ input terminals.

On the other hand, in the measuring device according to the first embodiment of the present invention, the first
The basic unit signal g (t) is used as the reference signal of.
The duration of the basic unit signal g (t) is 4 × δ from FIG.
Is. Therefore, the equation is modified in the same manner as the equation, and K ₁ samples are taken per unit time δ, and the first
If the correlator (11) is constructed as shown in FIG.

In FIG. 9, the first correlator (11) has a tap number of 4 ×
K ₁ single tapped delay line and (11a), 4 × K ₁ single multiplier and (11b), the input terminal number 4 × K ₁ cells connected to each output tap of the tapped delay line (11a) And an adder (11c).

Next, consider the second correlator (12) of the measuring apparatus according to the first embodiment of the present invention.

The second correlator (12) has only to have a function of calculating the right side of the equation from Ca (t) which is the output of the first correlator (11). The right side of the equation is that the value of Ca (t) at time t is multiplied by p ₁ and the value of Ca (t) at time (t + Tp) is
Multiply by p ₂ , multiply the value of Ca (t) at time (t + 2Tp) by p ₃
It means multiplying by and adding them. Therefore, assuming that K ₁ samples are taken per unit time δ, Tp = 4δ, and therefore the second correlator (12) may be constructed as shown in FIG.

That is, in FIG. 10, the second correlator (12) has a tapped delay line (12a) with 8 × K ₁ taps and 4 × K _{1 at} the output taps of this tapped delay line (12a). 3 multipliers (12 corresponding to every Tp)
b) and an adder (12c) having three input terminals.

Now, the total number of multipliers (11b) and (12b) required in the first correlator (11) and the second correlator (12) of the measuring apparatus according to the first embodiment of the present invention is Compare with the number of multipliers (10b) required in the correlator (10) of the conventional measuring device. In the first embodiment of the present invention,
The total number (4 × K ₁ +3) is 12 × K ₁ in the conventional device. That is, in the first embodiment of the present invention,
The number of multipliers can be greatly reduced. As described above, reducing the number of multipliers has an effect of improving the operation speed of the device and reducing the cost.

Further, the weighting to the multiplier (12b) required in the second correlator (12) is ± 1 in the above-mentioned first embodiment.
Is one of. The weighting of +1 means that the multiplier (12b) is unnecessary. Further, the weighting being −1 means that the multiplier (12b) can be replaced by an inverter. Therefore,
The first embodiment of the present invention is more advantageous in terms of operation speed and price.

On the other hand, similarly, the adders will be compared. In the first embodiment of the present invention, an adder (11c) having 4 × K ₁ input terminals and an adder (12c) having 3 input terminals are sufficient.
On the other hand, the conventional device requires an adder (10c) having 12 × K ₁ input terminals. Since the adder adds to the mouse formula, if the number of input terminals is reduced, this also has the effect of improving the operation speed and reducing the price.

In the first embodiment described above, in the basic unit signal g (t), the case where the waveform corresponding to each element (±) of the first series {a) is a rectangle has been described, but it corresponds to each element described above. Even when the waveform is close to a rectangle, the same operation and effect as those of the first embodiment can be obtained.

The configuration of the second embodiment of the present invention will be described with reference to FIG.

FIG. 11 is a block diagram showing a second embodiment of the present invention, in which an amplitude coded transmission signal generator (1A), a first correlator (11), a second correlator (12) and an ultrasonic wave are used. The probe (6) and the display (8) are exactly the same as those in the first embodiment.

In FIG. 11, the second embodiment of the present invention is the same as that of the first embodiment described above, except that the input side is connected to the amplitude coded transmission signal generator (1A) and the first correlator is used. A first reference signal generator whose output side is connected to (11) (1
3) and a second reference signal generator (14) whose input side is connected to the amplitude coded transmission signal generator (1A) and whose output side is connected to the second correlator (12). .

The first reference signal generator (13) uses the basic unit signal g (t) in the above-described first embodiment to generate the ultrasonic probe (6).
, A signal having a waveform similar to or the same as the waveform of the echo obtained when driven is generated and transmitted to the first correlator (11) as the first reference signal.

The second reference signal generator (14) generates a signal having a waveform similar to or the same as that of the second reference signal in the first embodiment, and uses this as a second reference signal for the second correlator ( 12) Communicate to.

The waveform of the first reference signal is s on the right side of the equation.
It is approximately equal to the waveform of the signal obtained when replaced by (t ₁₎ to g (t _1). Therefore, the first reference signal generator (13) has a frequency response characteristic that the ultrasonic probe (6) has in total transmission and reception, a frequency response characteristic of the test body S, and
It works as a filter having a frequency response characteristic in combination with a frequency response characteristic relating to ultrasonic reflection of a reflector such as a defect.

In this way, correlating echoes is equivalent to performing signal processing in which echoes are passed through a matched filter or an approximately matched filter. The matched filter has the effect of receiving a signal buried in noise with the maximum S / N ratio.

Therefore, the second embodiment of the present invention is S / S compared to the first embodiment using the basic unit signal itself as the first reference signal.
The effect of further improving the N ratio is synergistic with the operation and effect of the first embodiment.

The second reference signal generator (14) may generate, as the second reference signal, a signal whose amplitude slightly deviates from ± 1 at each time Tp. It suffices to generate the second reference signal having a waveform in which the compressed pulse C (t) is obtained with a high S / N ratio.

Also, in the second embodiment of the present invention, there are K ₃ sampling points within the duration of the first reference signal, and K ₂ during the time Tp.
Assuming that there are sampling points, the first correlator (11) has a tapped delay line with K ₃ taps and this tapped delay line, as can be seen by transforming the equation in the same manner as the equation. and K ₃ amino multiplier connected to each output tap, from the input terminal number K ₃ adders, may be configured similarly to the ninth FIG. The second correlator (12) has the number of taps (N−1) × K ₂
Delay lines with taps, and N multipliers connected every K ₂ at each output tap of the delay line with taps,
The adder having N input terminals may be configured in the same manner as in FIG. However, weighting p _i (i =
1, 2, 3, ..., N) may be ± 1 or may be a value from ± 1 for each i so that the compression pulse C (t) can be obtained with a high S / N ratio as described above. May be shifted.

The configuration of the third embodiment of the present invention will be described with reference to FIG.

FIG. 12 is a block diagram showing a third embodiment of the present invention, except for the above-mentioned first embodiment except for the phase-coded transmission signal generator (1B).
It is exactly the same as that of the embodiment.

Next, the operation of the above-described third embodiment will be described with reference to FIGS. 13, 14, and 15.

FIG. 13 is a waveform diagram showing a basic unit signal in the third embodiment of the present invention, FIGS. 14 (a) and 14 (b) are waveform diagrams showing other unit waveforms constituting the basic unit signal, and FIG. It is a wave form diagram which shows a transmission signal.

In FIG. 13, the basic unit signal is a signal generated using the same first sequence {a} as in the case of the first embodiment described above. In the figure, δ ₀ is a fixed time. In order to make the relationship between the first series and the basic unit signal easy to understand, the sign (±) of the first series {a} is also entered.

Although FIG. 13 shows the case where the unit waveform corresponding to each element (±) of the first series {a) is a sine wave, the unit waveform is shown in FIG. 14 (a) or (b). As shown, it may be a waveform having a smooth curved portion or a vibration waveform in which the amplitude or the interval between zero cross points is not constant.

Note that, in FIG. 13, when the fixed time δ is equal to the fixed time δ ₀ , the basic unit signal is a signal having a waveform in which the phase is encoded. The phase encoding method is described in detail in Japanese Patent Application No. 1-45316, which is related to the present invention.

In FIG. 15, the transmission signal has the same second sequence {p} as in the case of the first embodiment described above and the basic unit signal shown in FIG. This is a signal generated according to the procedure. That is, the second sequence {p}
The basic unit signal g (t) is assigned to the sign + of
Is assigned a signal −g (t) obtained by multiplying the basic unit signal g (t) by −1, and ± g (t) is a time axis according to the order in which the code of the second sequence {p} appears. Arranged above. Sign ± of the second sequence {p} and signal ± g
In order to make the relationship with (t) easier to understand, the sign ± of the second series {p} is also shown in the figure.

In the third embodiment of the present invention, the transmission signal of the first embodiment shown in FIG. 3 is replaced with the transmission signal shown in FIG. 15 to drive the ultrasonic probe (6). The echo signal processing is the same as in the first embodiment. That is, the basic unit signal shown in FIG. 13 is used as the first reference signal, and the same reference signal as that of the first embodiment is used as the second reference signal.

Also in the third embodiment of the present invention, equations (1) to (3) hold regardless of the shape of the waveform of the basic unit signal g (t),
Also, the basic unit compression pulse A (t−t ₀ ) obtained by substituting the basic unit signal shown in FIG. 13 into the equation has a large amplitude only in the vicinity of t = t _0, and the amplitude at t ≠ t ₀ is Since it is small, it has the same operation as the first embodiment. Since the above-described characteristics of the basic unit compressed pulse are established even when the unit waveforms shown in FIGS. 14 (a) and 14 (b) are used, the same operation as in the first embodiment is obtained in this case as well.

Next, the effect of the above-described third embodiment will be described.

In the third embodiment of the present invention, the same operation and effect as in the first embodiment are obtained, and as can be seen from Japanese Patent Application Nos. 1-45316 and 1-86383 related to the present invention. , Bringing the frequency characteristics of the signal close to the frequency characteristics of the ultrasonic probe (6), the frequency characteristics of the test body S, and the frequency characteristics related to the ultrasonic reflection of the reflector of the test body S combined. You can

Therefore, it can be expected that the utilization efficiency of signal energy is increased. On the contrary, if the unit waveform corresponding to the element (±) of the first series is selected so as to have a frequency characteristic close to the above-mentioned combined frequency characteristic, the utilization efficiency of the signal energy becomes higher and the S / N ratio becomes higher. Can be expected to improve.

The first correlator (11) and the second correlator (12) are
When the delay line with taps, the multiplier and the adder are used, the construction method is the same as that of the first embodiment.

The configuration of the fourth embodiment of the present invention will be described with reference to FIG.

FIG. 16 is a block diagram showing a fourth embodiment of the present invention, which is exactly the same as that of the second embodiment described above except for the phase-coded transmission signal generator (1B).

The first reference signal generator (13) has the same or similar waveform as the waveform of the echo obtained when the ultrasonic probe (6) is driven by using the basic unit signal in the third embodiment described above. A signal having the same is generated and is transmitted to the first correlator (11) as a first reference signal.

The second reference signal generator (14) generates a signal having a waveform that is the same as or similar to the waveform of the second reference signal in the above-described third embodiment, and uses this as a second reference signal for the second reference signal. It is transmitted to the correlator (12).

Next, the effect of the above-described fourth embodiment will be described.

Also in the fourth embodiment, the first reference signal has a waveform of a signal obtained when s (t ₁ ) in the right side of the equation is replaced with the basic unit signal g (t ₁ ) in the third embodiment. They are almost equal.

Therefore, it can be expected that the same effect as that of the second embodiment described above is synergistic with the operation and effect of the third embodiment described above.

Also in the fourth embodiment, the second reference signal generator (14) may generate, as the second reference signal, a signal whose amplitude is slightly deviated from ± 1 for each time Tp. Compressed pulse C
The second waveform having such a waveform that (t) can be obtained with a high S / N ratio.
It is sufficient to generate the reference signal of.

In addition, the first correlator (11) and the second correlator (12) are
When the delay line with taps, the multiplier and the adder are used, the construction method is the same as that of the second embodiment.

The configuration of the fifth embodiment of the present invention will be described with reference to FIG.

FIG. 17 is a block diagram showing a fifth embodiment of the present invention, which is completely the same as that of the above-mentioned fourth embodiment except for the ultrasonic probe (6A) for transmission and the (6B) for reception. It is the same.

The fifth embodiment has the same actions and effects as those of the fourth embodiment.

Of course, the ultrasonic probe for transmission (6A) and the ultrasonic probe for reception (6B) may be applied to the first, second and third embodiments of the present invention.

The configuration of the sixth embodiment of the present invention will be described with reference to FIG.

FIG. 18 is a block diagram showing a sixth embodiment of the present invention, in which a third correlator (15) and a third reference signal generator (1
Except for 6), it is exactly the same as that of the fifth embodiment described above.

The third reference signal generator (16) is connected to the phase-encoded transmission signal generator (1B), and the third correlator (15) is the second correlator (12) and the third reference signal generator. The input side is connected to (16) and the output side is connected to the display (8).

In this sixth embodiment, a phase-coded transmission signal generator (1B)
Generates a third sequence {v} anew, while regarding the transmission signal s (t) generated in the fifth embodiment as a new second basic unit signal g ₂ (t), A transmission signal is generated using the third sequence {v} and the second basic unit signal g ₂ (t). The transmission signal generation procedure follows the same procedure as the transmission signal generation procedure using the basic unit signal g (t) and the second sequence {p} in the fifth embodiment.

That is, the code + of the third sequence {v} is assigned the _second basic unit signal g ₂ (t), and the code − is obtained by multiplying the second basic unit signal g ₂ (t) by −1. Assigned signal −g ₂ (t), and arrange the signals ± g ₂ (t) according to the order of appearance of the symbols ± of the third sequence {v}.

The third reference signal generator (16) has a third waveform having the same or similar waveform as the amplitude-encoded waveform by the third sequence.
Generate the reference signal of.

The third correlator (15) uses the third reference signal,
Correlation processing of the output of the second correlator (12) is executed. The output of the third correlator (15) is transmitted to the display (8) and displayed.

When the third correlator (15) is composed of a delay line with taps, a multiplier and an adder, the construction method is the same as that of the second correlator (12) described above.

In the sixth embodiment, the duration of the transmission signal can be made longer than that in the fifth embodiment described above. in this way,
The longer the duration of the transmission signal, the larger the difference in the number of multipliers and the number of input terminals of the adder compared to the conventional device, and the more advantageous the operation speed and the price.

Further, the transmission signal generating procedure in the sixth embodiment is repeatedly used, and correspondingly, fourth, fifth, ... Reference signal generators and fourth, fifth, .. For example, since the duration of the transmission signal becomes longer and longer, the difference in the number of multipliers and the number of input terminals of the adder will become larger and larger in comparison with the conventional equipment, which will increase the operating speed and price. Be advantageous

In addition, the same configuration as that of the sixth embodiment has the above-described first to fourth features.
You may apply to an Example.

Next, various application examples will be described.

In each of the above-described embodiments, the case where the length M is 4 as the first series {a} and the length N is 3 as the second series {p} has been described. Length M
And N are not limited to this. It is also applicable when the lengths M and N are arbitrary natural numbers.

For example, when a basic unit signal is used as the first reference signal and there are K ₁ sampling points during time δ,
Consider the lengths M and N as arbitrary natural numbers. In particular, M or N may be 1.

When Tp = Mδ, the first correlator (11) is connected to the tapped delay line (11a) having M × K ₁ taps and each output tap of the tapped delay line (11a). The M × K ₁ multiplier (11b) and the number of input terminals M × K ₁ adder (11c) may be configured in the same manner as in FIG.

The second correlator (12) has a tap number (N-1) × M.
× K ₁ tapped delay line (12a), and N taped multipliers (12b) connected every M × K _{1 at} the output taps of this tapped delay line (12a) and the number of input terminals The N adders (12c) may be configured in the same manner as in FIG.

Also in this case, in the conventional device, the tapped delay line (10a) having M × N × K ₁ taps and M × N × K ₁ connected to each output tap of the tapped delay line (10a) are provided. Multiplier of (10
Since b) and the adder (10c) having M × N × K ₁ input terminals are required, the same effect as that of the above-described embodiment can be obtained.

Next, consider the case where Tp> Mδ or Tp <Mδ. In these cases, assuming that there are K ₂ samplings during the time Tp, the first correlator (11) has a tapped delay line (11a) with M × K ₁ taps, Similar to FIG. 9, the M × K ₁ multiplier (11b) connected to each output tap of the tapped delay line (11a) and the adder (11c) having M × K ₁ input terminals are used. And also a second correlator (12)
Is the number of taps (N-1) × K ₂ delay lines with taps (12
a), and at the output tap of this tapped delay line (12a), from the N multipliers (12b) connected every K ₂ and the adder (12c) having N input terminals, The configuration may be similar to that shown in FIG. Also in this case, the same operation and effect as those in the above-described embodiment are obtained.

Further, in general, assuming that there are K ₃ sampling points within the duration of the first reference signal and K ₂ samplings during the time Tp, the first correlator (11) is Delay line with taps (11a) with K taps of ₃ and delay line with taps (1
K ₃ multipliers (11b) connected to each output tap in 1a)
And an adder (11c) having K ₃ input terminals, the second correlator (12) has a number of taps (N−1) × K ₂ taps. With delay line (12a), N multipliers (12b) connected every K ₂ in the output tap of this delay line with tap (12a), and adder (12c) with N input terminals Therefore, the configuration may be similar to that shown in FIG. Also in this case, the same operation as in the above-mentioned embodiment,
effective. When M is 1, the waveform of the basic unit signal is equal to the unit waveform itself such as a rectangular waveform, an approximate rectangular waveform, a sine waveform, a waveform having a smooth curved portion, or a vibration waveform. Therefore, in this case, the first correlator (11) may be removed in the above-described first and third embodiments. In addition, the second embodiment, the fourth embodiment, the fifth
In the embodiment and the sixth embodiment, the first correlator (11)
Can be left intact to function as a matched filter or an approximate matched filter. Also, N is 1
In this case, the second correlator (12) may be removed in the above-mentioned first to sixth embodiments.

Furthermore, in each of the above-described embodiments, the case where h (t) is a delta function has been described, but also in the case of the above-described embodiments, h (t) is a function having an arbitrary waveform including a vibration component and the like. Has the same action and effect as.

Furthermore, in each of the above-described embodiments, the case where the first series and the second series are different has been described, but these two series may be the same. Also, there are no restrictions on the characteristics of these sequences.

Furthermore, in each of the above-described embodiments, the case where the first and second sequences are binary finite length sequences has been described, but the present invention is not limited to this, and either of the first and second sequences is One or both may be a binary periodic sequence. Two
In the case of the value period series, the first or second correlator may be configured in the same manner as in the above-described embodiment for one period of the corresponding binary period sequence.

Further, the above-mentioned first reference signal is the same as the waveform of the echo from the surface or bottom of the test body S obtained by this ultrasonic probe when the ultrasonic probe is excited by the basic unit signal, or The signal may have a similar waveform or a waveform that is the same as or similar to the waveform of the echo from the surface or the bottom surface of another object.

Further, the above-mentioned first reference signal, when the ultrasonic probe is excited by the reference unit signal, is transmitted from the output end of the amplitude or phase encoded transmission signal generator to the ultrasonic probe, the test object S,
It may be a signal having a waveform calculated based on the frequency response characteristic of the signal propagation path reaching the input end of the first correlator via the ultrasonic probe and the basic unit signal. In addition,
The frequency response characteristic of the signal propagation path may include the frequency characteristic regarding the reflection of the reflector of the test body S.

As described above, the embodiment of the present invention has an effect that the structure of the correlator is simpler than that of the conventional one, whereby the operation speed can be improved, and the cost can be reduced, and the first series. If the waveform selected in consideration of the frequency response characteristics of the ultrasonic probe, test body and its reflector is used as the unit waveform corresponding to the element (±) of, the use efficiency of signal energy can be improved and When the transmission signal is passed through a reference signal generator that has the overall frequency response characteristics of the ultrasonic probe, test piece, and its reflector, the S /
It has the effect of being able to inspect with N ratio.

By the way, in the above description, the case of using it for the ultrasonic flaw detector is described, but it goes without saying that it can also be used for other ultrasonic diagnostic equipment.

Further, in the above description, the case where the ultrasonic probe is brought into contact with the test body has been described, but the ultrasonic probe may not be brought into contact. In this case, transmission / reception of ultrasonic waves between the ultrasonic probe and the test body may be performed via a coupling medium such as water.

Further, the present invention may be applied to an ultrasonic wave transmission / reception circuit system of individual elements constituting an ultrasonic array probe.

Further, in the above description, the case where the ultrasonic wave is used as the wave has been described, but the invention may be applied to a wave other than the ultrasonic wave, for example, a transmission / reception circuit system of a system using an electromagnetic wave.

[Effects of the Invention] As described above, the present invention includes transmission signal generating means for generating a basic unit signal based on a first sequence and generating a transmission signal based on the basic unit signal and a second sequence. A transmitting unit that is excited by the transmitting signal to transmit a wave to an object, a receiving unit that receives an echo reflected from the object, and a first reference signal generated based on the first sequence. Using a first correlating means for correlating the echo, and a second reference signal generated based on the second sequence for correlating the output of the first correlating means. Since the second correlation means is provided, the operation speed can be improved and the price can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram showing the first embodiment of the present invention, and FIG.
FIG. 4 is a waveform diagram showing a basic unit signal of the first embodiment of the present invention, FIG. 3 is a waveform diagram showing a transmission signal of the first embodiment of the present invention, and FIG. 4 is a basic diagram of the first embodiment of the present invention. FIG. 5 is a waveform diagram showing a unit compressed pulse, FIG. 5 is a waveform diagram showing an output signal of the first correlator of the first embodiment of the present invention, and FIG. 6 is a second reference signal of the first embodiment of the present invention. FIG. 7 is a waveform diagram showing the compressed pulse of the first embodiment of the present invention, and FIG.
FIG. 9 is a waveform diagram showing another transmission signal of the first embodiment of the present invention, FIG. 9 is a block diagram showing a first correlator of the first embodiment of the present invention, and FIG. 10 is a first diagram of the present invention. FIG. 11 is a block diagram showing a second correlator of the embodiment, FIG. 11 is a block diagram showing the second embodiment of the present invention, FIG. 12 is a block diagram showing the third embodiment of the present invention, and FIG. A waveform diagram showing a basic unit signal of a third embodiment of the invention, FIGS. 14 (a) and 14 (b) are waveform diagrams showing a unit waveform of the third embodiment of the invention, and FIG. 15 is a third embodiment of the invention. FIG. 16 is a waveform diagram showing a transmission signal of an embodiment, FIG. 16 is a block diagram showing a fourth embodiment of the present invention, FIG. 17 is a block diagram showing a fifth embodiment of the present invention, and FIG. 6 is a block diagram showing an embodiment, FIG. 19 is a block diagram showing a conventional measuring device, FIG. 20 is a waveform diagram showing a transmission signal of the conventional measuring device, and FIG. Waveform diagram showing a compressed pulse of the measuring apparatus, FIG. 22 is a block diagram showing a correlator of a conventional measuring device. In the figure, (1A) ... amplitude encoded transmission signal generator, (1B) ... phase encoded transmission signal generator, (6) ... ultrasonic probe, (6A) ... transmission ultrasonic waves. Probe, (6B) ... ultrasonic probe for reception, (8) ... indicator, (11) ... first correlator, (12) ... second correlator, (13) ) ... the first reference signal generator, (14) ... the second reference signal generator, (15) ... the third correlator, (16) ... the third reference signal generator. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (4)

[Claims] 1. A transmission signal generating means for generating a basic unit signal based on a first sequence and generating a transmission signal based on the basic unit signal and a second sequence; Transmitting means for transmitting to the object, receiving means for receiving the echo reflected from the object, first correlating the echo using a first reference signal generated based on the first sequence Second correlating means for correlating the output of the first correlating means with a second reference signal generated based on the second sequence.
A measuring device comprising: 2. The basic unit signal is a signal having a waveform that is amplitude-encoded or phase-encoded using the first sequence, and a unit waveform is a positive code or a negative code of the first sequence. Alternatively, a signal to which a waveform obtained by multiplying the unit waveform by -1 is assigned, a rectangular waveform or a waveform obtained by multiplying -1 to the rectangular waveform is assigned to the positive sign or the negative sign of the first sequence. A signal, or a signal in which a vibration waveform or a waveform obtained by multiplying the vibration waveform by -1 is assigned to the positive or negative sign of the first sequence. Measuring device. 3. The transmission signal is assigned a waveform obtained by multiplying the waveform of the basic unit signal or the waveform of the basic unit signal by -1 to the positive or negative sign of the second sequence. The measuring device according to claim 1, wherein the measuring device is a signal. 4. The first reference signal is a signal having a waveform of the basic unit signal, or a waveform of an echo from the object obtained by the receiving unit when the transmitting unit is excited by the basic unit signal. A signal having a waveform similar to or similar to the above, or the second reference signal is a signal having a waveform similar to or similar to the waveform amplitude-coded using the second sequence. The measuring device according to claim 1.