JPH0781992B2 - Ultrasonic measuring device - Google Patents

Description

The present invention relates to a measuring apparatus that employs a correlation processing method using ultrasonic waves, for example.

Particularly, the transmission waves excited by the first and second transmission signals having a sine waveform are transmitted by the object,
S / N ratio (signal-to-noise ratio) because the first and second echoes from the target object corresponding to the second transmission signal and the second transmission signal are respectively subjected to correlation processing and the correlation processing results are subjected to signal processing. The present invention relates to a measuring device which is good, has a small energy loss of a transmission signal, and can have a low range sidelobe level.

For convenience of explanation, an ultrasonic flaw detector (ultrasonic nondestructive inspection device) will be described as an example of the measuring device.

[Prior Art] In the nondestructive inspection apparatus using ultrasonic waves, the impulse method is often used. The structure of a conventional example adopting the impulse method will be described with reference to FIG.

Fig. 17 shows, for example, "Ultrasonic flaw detection", Japan Society for the Promotion of Science, Steelmaking 19th Committee, December 20, 1977, published by Nikkan Kogyo Shimbun, pages 114-140, pages 173-174. FIG. 7 is a block diagram showing a conventional ultrasonic nondestructive inspection device shown in FIG.

In FIG. 17, a conventional ultrasonic non-destructive inspection apparatus includes a pulse oscillation circuit (1), an ultrasonic probe (2) connected to the pulse oscillation circuit (1), and the ultrasonic probe. (2)
The receiving circuit (3) is connected to the receiving circuit (3), and the display (4) such as a CRT connected to the receiving circuit (3).

The ultrasonic probe (2) is in contact with the test body S such as a steel material.

Next, the operation of the above-mentioned conventional example will be described with reference to FIGS. 18 (a) and 18 (b).
And (c) will be described.

18 (a) to 18 (c) are waveform charts showing the operation of the conventional ultrasonic nondestructive inspection apparatus.

The pulse oscillating circuit (1) is as shown in FIG.
Oscillates a pulse with a short vibration duration.

The ultrasonic probe (2) is driven by the above-mentioned pulse and sends an ultrasonic wave having a short pulse width into the test body S. And
The reflected echo reflected in the test body S is received and transmitted to the receiving circuit (3).

The receiving circuit (3) amplifies the reflected echo and displays it (4)
Communicate to.

The display (4) displays the amplified reflected echo. First
As shown in FIG. 18B, the reflected echo appears at the position of time t = t ₀ .

Since this time t ₀ is the time required for the ultrasonic waves to reciprocate up to the reflector in the test body S, the position of the reflector can be calculated by measuring the time t ₀ .

However, in the above-described conventional example, as shown in FIG. 18 (c), when the level of the reflected echo is small and the noise level superimposed on the reflected echo is large under a poor S / N ratio environment, There is a problem that the position of the body cannot be inspected with accurate accuracy.

The solution to the above-mentioned problem is to increase the amplitude of the pulse that drives the ultrasonic probe (2), but the limitation of the elements constituting the pulse oscillation circuit (1) and the ultrasonic probe (2 The pulse amplitude has an upper limit due to reasons such as the limitation of the withstand power of (1) and so is not a complete solution.

Compared to the conventional example described above, even in an environment with a poor S / N ratio,
There is a method using correlation processing that can inspect the position of the reflector in the test body S with accurate accuracy. Among the methods using this correlation processing, there is a method of using a complementary sequence as a code sequence excellent in range side lobe.

Here, the principle of the method of using the correlation process which employs the complementary sequence will be described with reference to FIGS. 19 (a), (b) and (c).

FIGS. 19 (a) to 19 (c) show, for example, correlation processing using complementary sequences shown in “Code Theory” by Miyagawa et al., June 29, 1979, Shokoido, pages 474-492. It is explanatory drawing which shows a principle.

The complementary sequence is composed of a first sequence having a finite length consisting of two values and a second sequence having a finite length consisting of two values and having a complementary relationship with the first sequence.

Complementary relationship means that when the autocorrelation function of the first series and the autocorrelation function of the second series are compared, the main lobes and the side lobes have the same shape,
Regarding the phase, it means that the main lobes have the same phase and the side lobes have the opposite phase.

Therefore, if the sum of the autocorrelation function of the first series and the autocorrelation function of the second series is taken, the main lobes are mutually strengthened and the side lobes are canceled out to zero.

The complementary sequence having a length of 4 is, for example, the first sequence. And the second series Is expressed as Two series components aj, bj (j = 0,1,2,3)
May be assigned a positive or negative sign as described above, or may be assigned +1 for a positive sign and -1 for a negative sign.

Therefore, the autocorrelation function of the first series is expressed as ρa (k). As shown in FIG. 19 (a), ρa (k) is the first sequence , As an infinite length sequence with zeros on both sides, that is, Ρa (k) = Σaj + k aj [j = −∞ to ∞]. However, +1 and -1 are assigned as aj.

Similarly, the autocorrelation function of the second sequence is represented by ρb (k). ρb (k) is also treated as an infinite length sequence, +1 and −1 are assigned as bj, and ρb (k) = Σbj + k bj [j = −∞ to ∞] ...

As can be seen from FIGS. 19 (a) and 19 (b), the autocorrelation functions ρa (k) and ρb (k) have the same shape between the main lobes and the side lobes, and the phases are the same between the main lobes. In phase, side lobes are in opposite phase. Therefore, when the sum of the autocorrelation functions ρa (k) and ρb (k) is taken, the side lobe level becomes zero as shown in FIG. 19 (c).

The above side lobes are called range side lobes when applied to the field of ultrasonic nondestructive inspection using correlation processing.

Now, the configuration of another conventional example using complementary sequence correlation processing will be described with reference to FIG.

Figure 20 shows, for example, "IEEE Ultrasonics Symposium Proce
eding 1981 P888-891 is another conventional ultrasonic non-destructive inspection device block diagram.

In FIG. 20, another conventional ultrasonic nondestructive inspection device is
Signal source (1A), digital delay line (11) connected to the signal source (1A), signal source (1A) and digital delay line (11)
A bipolar converter (12) connected to, a transmitter (13) connected to the bipolar converter (12),
A bipolar converter (14) also connected to the signal source (1A) and digital delay line (11), and a transmitter (1
3), bipolar converter (14) and ultrasonic probe (2)
It is composed of an analog correlator (5) connected to and an indicator (4) connected to the analog correlator (5).

The ultrasonic probe (2) is installed in the water tank in which the target S of brass is placed in the water. The analog correlator (5) includes a multiplier (5a) connected to the ultrasonic probe (2) and the bipolar converter (14), and an integrator (5b) connected to the multiplier (5a). ) And is composed of. In addition, the signal source (1A) and digital delay line (1
AND gate between the signal source (1A) and the bipolar converters (12) and (14) and between the digital delay line (11) and the bipolar converters (12) and (14). Etc. logic circuits are inserted.

Next, the operation of the other conventional example described above will be described with reference to FIGS. 21 (a) and 21 (b) and FIG.

FIGS. 21 (a) and 21 (b) are waveform diagrams showing a transmission signal of another conventional example, and FIG. 22 is a characteristic diagram showing a frequency characteristic of a transmission signal of another conventional example and an ultrasonic probe.

Transmission signals Sa (t) and Sb shown in FIGS. 21 (a) and 21 (b)
(T) is a signal source (1A), a digital delay line (11), a bipolar converter (12) and a transmitter (13),
It is transmitted to the ultrasonic probe (2).

The transmission signal Sa (t) is the first sequence forming a complementary sequence. (+, +, +,-) Is used as the transmission signal Sb
(T) uses (+, +,-, +) as the second sequence. The sign + corresponds to a rectangular wave having a positive amplitude, and the sign − corresponds to a rectangular wave having a negative amplitude with the same absolute value. Arranged above.

The ultrasonic probe (2) is driven by the transmission signal Sa (t) to transmit ultrasonic waves into water. Then, the reflection echo ga (t) reflected by the target S is delivered and transmitted to the multiplier (5a) of the analog correlator (5).

On the other hand, the same signal as the transmission signal Sa (t) is the signal source (1
A), digital delay line (11) and bipolar converter (1
It is transmitted to the multiplier (5a) by 4).

The analog correlator (5) executes a correlation calculation between the reflected echo ga (t) and the transmission signal Sa (t). That is, when the result of the correlation calculation is ρa (t), it is expressed as follows.

ρa (t) = ∫ga (t ′) Sa (t′−t) dt ′ [integration range: −∞ to ∞] ... Similarly, in the next time phase, the ultrasonic probe (2) has Driven by the transmission signal Sb (t), the analog correlator (5) produces a reflection echo gb (t) and the transmission signal Sb.
Correlation calculation with (t) is executed. That is, when the result of the correlation calculation is ρb (t), it is expressed as follows.

ρb (t) = ∫gb (t ′) Sb (t′−t) dt ′ [integration range: −∞ to ∞] ... Formula The analog correlator (5) thereafter adds the results of the correlation calculation of the formula and Then, it is transmitted to the display (4), and ρa (t) + ρb (t) is displayed.

By the way, generally, the ultrasonic probe (2) has a frequency response characteristic (solid line) as shown in FIG. On the other hand, the transmission signal Sa (t) shown in FIGS. 21 (a) and 21 (b).
Since Sb (t) and Sb (t) have a waveform consisting of only a rectangular portion, they have frequency characteristics (dotted line) as shown in FIG. That is, while the transmission signals Sa (t) and Sb (t) have considerable energy in the low frequency region,
The ultrasonic probe (2) does not respond in the low frequency region.

Therefore, in the other conventional example described above, most of the transmission energy is discarded by the ultrasonic probe (2), and there is a problem that the efficiency is low.

Another conventional example using the above-described correlation processing improves the S / N ratio, but as described above, if the efficiency is low, a considerable level of noise remains, and the test body S can be inspected with high accuracy. In the end, there is a problem in that it is necessary to increase the amplitude of the transmission signal.

[Problems to be Solved by the Invention] In the conventional ultrasonic nondestructive inspection apparatus as described above, the S / N
In an environment with a poor ratio, when the level of the reflected echo is low and the noise level superimposed on the reflected echo is high, there is a problem that the reflector cannot be accurately measured.

Further, in other conventional ultrasonic nondestructive inspection apparatus as described above, most of the transmission energy is discarded by the ultrasonic probe, there is a problem that efficiency is insufficient and sufficient S / N ratio cannot be obtained. there were.

This invention was made to solve the above-mentioned problems, and it is possible to measure a reflector with accurate accuracy even in an environment with a poor S / N ratio, and to improve the efficiency of use of transmitted energy. An object is to obtain an ultrasonic measuring device that can be increased in height.

[Means for Solving the Problems] The ultrasonic measurement device according to the present invention includes the following means.

(I). First transmission signal generating means for generating a first transmission signal having a sine waveform.

(Ii). Second transmission signal generating means for generating a second transmission signal having a sine waveform and having a complementary relationship with the first transmission signal.

(Iii). A first transmitting unit that is excited by the first transmission signal and transmits a transmission wave to an object.

(Iv). A second transmitting unit that is excited by the second transmission signal and transmits a transmission wave to an object.

(V). First receiving means for receiving a first echo corresponding to the first transmission signal.

(Vi). Second receiving means for receiving a second echo corresponding to the second transmission signal.

(Vii). A first correlation processing of the first echo using a first reference signal defined by the first transmission signal;
Correlation processing means.

(Viii). A second correlation processing of the second echo using a second reference signal defined by the second transmission signal;
Correlation processing means.

(Ix). Addition means for adding the signal obtained by the first correlation processing means and the signal obtained by the second correlation processing means.

[Operation] In the present invention, the first transmission signal generating means generates the first transmission signal having a sine waveform,
The second transmission signal having the sine waveform and having a complementary relationship with the first transmission signal is generated by the transmission signal generating means.

Further, the first transmitting means excites the transmitted wave to the object by being excited by the first transmitting signal, and the second transmitting means excites the transmitted wave by being excited by the second transmitting signal to the object. Sent to.

Further, the first receiving means receives the first echo corresponding to the first transmission signal, and the second receiving means receives the second echo corresponding to the second transmission signal. .

Furthermore, the first correlation processing means performs correlation processing on the first echo, and the second correlation processing means
The second echo is correlated.

Then, the signal obtained by the first correlation processing means and the signal obtained by the second correlation processing means are added by the adding means to output a signal with side lobes reduced.

[Embodiment] The configuration of a 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 (2) and an indicator (4) are exactly the same as those of the conventional device shown in FIG. .

In FIG. 1, the first embodiment of the present invention is the same as the conventional device described above, and a transmission signal generator (1
B), the correlator (5A) connected to the transmission signal generator (1B) and the ultrasonic probe (2), and the correlator (5A)
And an adder (6) including a memory and connected to.

The ultrasonic probe (2) is connected to the transmission signal generator (1B), and the display (4) is connected to the adder (6).

Next, the operation of the above-described first embodiment will be described with reference to FIGS.
A description will be given with reference to FIGS. 4 and 5.

2 (a) and 2 (b) are waveform diagrams showing a transmission signal of the first embodiment of the present invention, and FIGS. 3 (a) and 3 (b) are results of the correlation calculation of the first embodiment of the present invention. FIG. 4 is a waveform diagram showing the addition result of the correlation calculation of the first embodiment of the present invention, and FIG. 5 is a transmission signal of the first embodiment of the present invention and the frequency characteristics of the ultrasonic probe. It is a characteristic view to show.

The transmission signal generator (1B) outputs the transmission signals Sa ^* (t) and Sb ^*.
(T) is generated and transmitted to the ultrasonic probe (2).

As shown in FIGS. 2A and 2B, the transmission signal Sa
^* (T) is the first sequence forming a complementary sequence (+, +, +,-) As the transmission signal Sb
^* (T) uses (+, +,-, +) as the second series. The sign + is assigned sin2πf ₀ t (0 ≦ t ≦ T), the code − is assigned −sin2πf ₀ t (0 ≦ t ≦ T), and the sine wave described above is assigned to the time axis according to the order in which the sign appears. Arranged above. However, t is a time variable,
T is a fixed time and f ₀ is a fixed frequency.

The ultrasonic probe (2) is driven by the transmission signal Sa ^* (t) to transmit ultrasonic waves to the test body S. Then, the reflection echo ga ^* (t) reflected by the reflector of the test body S is received and transmitted to the correlator (5A).

On the other hand, the same signal as the transmission signal Sa ^* (t) is transmitted to the correlator (5A).

In the correlator (5A), the reflection echo ga ^* (t) and the transmission signal Sa
^* Perform correlation calculation with (t). That is, when the result of the correlation calculation is ρa ^* (t), it is expressed as follows.

ρa ^* (t) = ∫ga ^* (t ′) Sa ^* (t′−t) dt ′ [integration range: −∞ to ∞] ... Similarly, in the next time phase, the ultrasonic probe (2 ) Is driven by the transmission signal Sb ^* (t), and the correlator (5A) controls the reflection echo gb ^* (t) and the transmission signal Sb.
^* Perform correlation calculation with (t). That is, when the result of the correlation calculation is ρb ^* (t), it is expressed as follows.

ρb ^* (t) = ∫gb ^* (t ′) Sb ^* (t′−t) dt ′ [integration range: −∞ to ∞] ... Formula The adder (6) then calculates the correlation result of the formula and Is added and transmitted to the display (4), and ρa ^* (t) + ρb ^* (t) is displayed. Incidentally, the adder (6) stores .rho.a ^* (t) to the memory until pb ^* (t) is obtained.

Here, the operation principle of the above-described first embodiment of the present invention will be described.

First And the second If and are in a complementary relationship, the transmission signals Sa ^* (t) and Sb
^* (T) is in a complementary relationship, and when both are added, the level of the range side lobe becomes zero in principle.

When the autocorrelation functions of the transmission signals Sa ^* (t) and Sb ^* (t) are represented by ρa ^* (τ) and ρb ^* (τ), the autocorrelation functions ρa ^* (τ) and ρb ^* (τ) are , Is defined as follows.

ρa ^* (τ) = ∫Sa ^* (t) Sa ^* (t−τ) dt [Integration range: −∞ to ∞] Equation ρb ^* (τ) = ∫Sb ^* (t) Sb ^* (t−τ) dt [integration range: −∞ to ∞] Equation As shown in FIGS. 3A and 3B, the autocorrelation function ρ
Comparing a ^* (τ) and ρb ^* (τ), the main lobes have the same shape and the side lobes have the same shape, and the main lobes have the same phase and the side lobes have the opposite phase. Therefore, the autocorrelation functions ρa ^* (τ) and ρ
When b ^* (τ) is added, the side lobe level becomes zero as shown in FIG. That is, the first And the second If and are complementary, the transmission signals Sa ^* (t) and Sb
^* It has the same relationship with (t).

2 (a) and 2 (b), sin2πf ₀ t and −sin2
Although the case where the arrangement interval T ′ with πf ₀ t is larger than T is shown, the above-described relationship holds when the arrangement interval T ′ is equal to T. Further, the case where the number of cycles of sin2πf ₀ t and −sin2πf ₀ t is 3 (= f ₀ T) is shown, but the above-described function holds regardless of the number of cycles.

Consider the case where the above-mentioned relationship is applied to a nondestructive inspection using ultrasonic waves.

When the ultrasonic probe (2) is driven by the transmission signal Sa ^* (t) and the time required for the ultrasonic waves to reciprocate up to the reflector in the test body S is t ₀ , the reflected echo is approximate. To Sa
^It is expressed as ^* (t−t ₀ ). This reflected echo Sa ^* (t-
t ₀ ) and the transmission signal Sa ^* (t) are correlated, ∫Sa ^* (t−t ₀ ) Sa ^* (t−τ) dt = ρa ^* (τ−t ₀ ) [Integration range: −∞ ~ ∞] ... the formula is obtained.

Similarly, when the ultrasonic probe (2) is driven by the transmission signal Sb ^* (t) in the next time phase, the reflected echo is approximately represented by Sb ^* (t−t ₀ ). When the correlation between the reflected echo Sb ^* (t−t ₀ ) and the transmission signal Sb ^* (t) is calculated, ∫Sb ^* (t−t ₀ ) Sb ^* (t−τ) dt = ρb ^* (τ−t) ₀ ) [Integration range: −∞ to ∞] Equation is obtained.

When the results of the above-described correlation calculation are added, ρa ^* (τ−t ₀ ) + ρb ^* (τ−t ₀ ) is obtained. The result of this addition is the waveform shown in FIG.
Equivalent to the waveform translated by t ₀ along the time axis. That is, τ = t ₀ has a main lobe and the range sidelobe level is zero. Therefore, the position of the reflector can be known from the time position where the main lobe appears.

The result of the first embodiment of the present invention will be described. By setting the frequency f ₀ of the transmitted signal Sa ^{* (t)} and Sb ^{* (t)} in the vicinity of the center frequency of the ultrasonic probe (2), the transmission signal Sa ^*
(T) and Sb ^* (t) and the frequency response characteristics of the ultrasonic probe (2) have a relationship as shown in FIG. Transmission signal
Sa ^* (t) and Sb ^* (t) have almost no energy in the low frequency region. Most of that energy is
It can be seen that it passes through the ultrasonic probe (2). Therefore, the utilization efficiency of transmission energy is higher than that of other conventional examples.

This effect is obtained by using the transmission signal having the sine waveform in the first embodiment of the present invention, while the transmission signal having the waveform consisting of only the rectangular portion is used in the other conventional examples. It is a thing. It is not limited to a sine waveform in the strict sense. The same effect can be obtained if the transmission signal has a sinusoidal vibration waveform that allows most of the energy to pass through the ultrasonic probe (2).

Next, in order to see the effect of improving the range side lobe level and the S / N ratio of the first embodiment of the present invention, another transmission signal having a sine wave is used, and operation under the conditions described below is performed. Will be described with reference to FIG. 6, FIG. 7, FIG. 8 and FIG.

6 (a) and 6 (b) are waveform diagrams showing other transmission signals of the first embodiment of the present invention, and FIGS. 7 (a) and 7 (b) are other reflections of the first embodiment of the present invention. Waveform diagram showing echo, No. 8
FIGS. 9 (a) and 9 (b) are waveform diagrams showing the result of another correlation calculation of the first embodiment of the present invention, and FIG. 9 is a waveform showing the addition result of another correlation calculation of the first embodiment of the present invention. It is a figure.

As the ultrasonic probe (2), a so-called broadband probe having a frequency of 5 MHz and a specific bandwidth of 60% or more was used, and a steel material was used as the test body S.

As the complementary series, a series having a length of 8 shown below was used.

Also these Corresponding to the transmission signals Sa ^** (t) and Sb
^** (t) used the signals shown in FIGS. 6 (a) and 6 (b). f ₀ = 5MHz, f ₀ T = 1.5, interval T ′ between unit waveforms is T
Set equal to.

First, when the ultrasonic probe (2) was driven by the transmission signal Sa ^** (t), the reflection echo ga ^** (t) as shown in FIG. 7 (a) was measured. Similarly, the transmitted signal Sb
^The reflected echo gb ^** (t) as shown in FIG. 7 (b) was measured by ^** (t).

The reason why the waveforms of the reflected echoes ga ^** (t) and gb ^** (t) are different from the waveforms of the transmission signals Sa ^** (t) and Sb ^** (t) is that the ultrasonic probe (2) The reason is that the filter action of the ultrasonic probe (2) has acted because the bandwidth of ω is finite. This filter action is based on the transmission signal Sa ^**
Since (t) and Sb ^** (t) pass twice when the ultrasonic probe (2) transmits and receives, it works double.

When the correlation calculation between the transmission signal Sa ^** (t) and the reflection echo ga ^** (t) was performed, the result as shown in FIG. 8 (a) was measured. Similarly, when the correlation calculation between the transmission signal Sb ^** (t) and the reflected echo gb ^** (t) was performed, the result shown in FIG. 8 (b) was measured.

Then, when the above two calculation results were added, the addition result as shown in FIG. 9 was measured. The S / N ratio including the range sidelobe level was about -32 dB, and a considerably low result was obtained.

Further, for comparison, the transmission signal Sa ^** (t) described above is used.
And Sb ^** (t), the operation of the conventional example adopting the impulse method shown in FIG. 17 when driven by a signal having the same waveform will be described with reference to FIG.

10 (a) and 10 (b) are waveform charts showing the operation of the conventional ultrasonic nondestructive inspection apparatus.

The ultrasonic probe (2) and the test body S are the same as in the case of the first embodiment using other transmission signals described above.

The ultrasonic probe (2) was driven by a signal as shown in Fig. 10 (a). This signal has the same waveform and amplitude peak value as the transmission signals Sa ^** (t) and Sb ^** (t).

Then, a reflection echo as shown in FIG. 10 (b) was measured. Noise is superimposed on this reflected echo, and S /
The N ratio is only about 25 dB.

Therefore, as described above, the first embodiment of the present invention compares the results shown in FIGS. 9 and 10 (a) with S /
The N ratio is improved by about 7 dB, and the utilization efficiency of transmission energy can be increased as shown in FIG.

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 a transmission signal generator (1B), an ultrasonic probe (2), a correlator (5A), an adder (6) and an indicator. (4) is exactly the same as that of 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 transmission signal generator (1B) and the output is provided to the correlator (5A). It is composed of a reference signal generator (7) whose sides are connected.

Next, the operation of the above-described second embodiment will be described with reference to FIGS. 12 and 13.

12 (a) and (b) and FIG. 13 are waveform charts showing the operation of the second embodiment of the present invention.

The implementation conditions are the same as in the case of the first embodiment described above.

First, the transmission signal generator (1B)
^** (t) and Sb ^** (t) are generated to drive the ultrasonic probe (2). These transmitted signals Sa ^** (t) and
Sb ^** (t) is the same as in the first embodiment described above.

The ultrasonic probe (2) transmits the transmitted signals Sa ^** (t) and Sb.
Driven by ^** (t), ultrasonic waves are transmitted to the test body S, and the reflected echoes ga ^** (t) and gb ^** (t) are received and transmitted to the correlator (5A). .

On the other hand, the reference signal generator (7) outputs the transmission signal Sa ^** (t).
And reference signals ha (t) and hb based on Sb ^** (t)
(T) is generated and transmitted to the correlator (5A).

These reference signals ha (t) and hb (t) are transmitted signals Sa
^** (t) and Sb ^** (t) are signals obtained when passing through the ultrasonic probe (2) having the filter characteristics at the time of transmitting and receiving. That is, when the filter characteristics (impulse response characteristics) of the ultrasonic probe (2) when transmitting and receiving ultrasonic waves are represented by u ₁ (t) and u ₂ (t),
It is expressed by the following formula.

ha (t) = ∬Sa ^** (t ′) u ₁ (t ″ −t ′) u ₂ (t ″ −t) dt′dt ″ [integration range: −∞ to ∞] Equation hb (t) = ∬Sb ^** (t ′) u ₁ (t ″ −t ′) u ₂ (t ″ −t) dt′dt ″ [integration range: −∞ to ∞] ... Formula Note that the reference signal ha ( t) and hb (t) are
The ultrasonic probe (2) transmits signals Sa ^** (t) and Sb ^**
It is a signal obtained by previously measuring the reflection echo from the bottom surface of the test body S by driving by (t). The reason is that the reflected echo from the bottom surface of the test body S is transmitted signals Sa ^** (t) and Sb.
^** (t) is equal to a signal that is passed through the ultrasonic probe (2) having filter characteristics twice in the stages of transmission and reception, and the reflection echo from the bottom surface is high
It can be measured by S / N ratio.

The correlator (5A) then reflects the reflection echo ga ^** (t) and
The correlation calculation between gb ^** (t) and the reference signals ha (t) and hb (t) is performed while changing the variable τ. When expressed by a mathematical expression, it is expressed as follows.

∫ga ^** (t) ha (t−τ) dt [Integration range: −∞ to ∞]… Equation ∫gb ^** (t) hb (t−τ) dt [Integration range: −∞ to ∞]… Equation The integration range in the actual and equations is the reference signal ha
(T) and hb (t) were considered to be almost zero, and they were truncated to a finite range. That is, the reference signals ha (t) and
Tb is the time width that has a large value that hb (t) cannot be regarded as zero.
Letting a and Tb, the integration ranges are −Ta / 2 + τ to Ta / 2 + τ and −Tb / 2 + τ to Tb / 2 + τ, respectively, in the above equation and equation.

12 (a) and 12 (b) show the results of the correlation calculation of and in the above-mentioned integration range.

Finally, the adder (6) adds the results of the correlation calculation of and. That is, the result of the correlation calculation of the formula is temporarily stored in the internal memory, and the result of the correlation calculation of the formula and the stored result of the correlation calculation of the formula are added in the next time phase. FIG. 13 illustrates the result of addition.

Here, comparing with the result of the correlation calculation of the first embodiment of the present invention shown in FIG. 9, the level of the range side lobe of the first embodiment is about −32 dB, while the second embodiment of the present invention is The range sidelobe level in the example is about −48 dB as shown in FIG. 13, and the range sidelobe level is the first level.
It is improved by about 16 dB as compared with the embodiment.

Since the second embodiment of the present invention has the above-mentioned configuration, it is effective even in an environment with a poor S / N ratio, and the range side lobe level can be made extremely small. Play.

In the first and second embodiments described above,
All signals were digitally converted, and correlation calculation and addition processing were performed by a computer.

By the way, various means for performing the correlation calculation can be considered. Two specific examples of means for performing the correlation calculation will be described with reference to FIGS. 14 and 15.

FIG. 14 is a block diagram showing an example of the correlator of the present invention.

In FIG. 14, the correlator (5B) is an ultrasonic probe (2).
The delay line with taps (50) connected to the reference signal generator (7) and the delay line with taps (50)
Each of the multipliers (51) and an adder (52) connected to the multiplier (51).

This correlator (5B) 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.

∫ga ^** (t) ha (t−τ) dt [integration range: −∞ to ∞] = ∫ga ^** (t + τ) ha (t) dt [integration range: −∞ to ∞]
∞] ≈ ∫ga ^** (t + τ) ha (t) dt [integration range: 0 to Ta] ≈Σga ^** (kΔt + lΔt) ha (kΔt) [k = 1 to Ka] ... where k and l are integers , Δt is a sampling interval, Ka is a constant, and t = kΔt, τ = 1lΔt, and Ta = KaΔt.

In the correlator (5B), Δt is the delay time between taps of the delay line with taps (50), and Ka is the total number of taps. Reflection echo ga
^{When **} (t) is input to the delay line (50) with taps, for example, the output of the k-th tap is the weight that is known in advance.
ha (kΔt) is multiplied by the multiplier (51).
After that, the adder (52) adds the outputs of all the taps, and the result is equal to the above-mentioned equation.

Also, the equation can be transformed as follows.

∫gb ^** (t) hb (t-τ) dt [Integration range: -∞ to ∞] ≒ Σgb ^** (kΔt + 1lΔt) hb (kΔt) [k = 1 to Kb] ... where Tb = KbΔt .

Since the correlation calculation of the formula and the correlation calculation of the formula may be performed in different phases in terms of time, the weight is set to hb (kΔ
It only has to be replaced with t).

Further, even if two systems of the delay line with tap (50), the multiplier (51) and the adder (52) are provided and the respective correlation operations are performed separately, the same action and effect can be expected.

FIG. 15 is a block diagram showing another example of the correlator of the present invention.

In FIG. 15, a correlator (5C) is a Fourier transformer (53) connected to the reference signal generator (7), a corrector (54) connected to the Fourier transformer (53), A Fourier transformer (55) connected to the acoustic probe (2), a corrector (56) connected to the Fourier transformer (55),
Multiplier (57) connected to compensators (54) and (56)
And an inverse Fourier transformer (58) connected to this multiplier (57).

This correlator (5C) utilizes the fact that the correlation calculation shown by the above and the equation is equal to the signal obtained by subjecting each signal to Fourier transform, multiplication, and then inverse Fourier transform.

That is, the Fourier transformer (53) Fourier transforms the reference signals ha (t) and hb (t) from the reference signal generator (7), and the Fourier transformer (55) is an ultrasonic probe ( 2) Reflected echoes from ga ^* (t) and gb ^** (t)
Fourier transform of.

The correctors (54) and (56) use the Fourier-transformed reference signals ha (t) and hb (t) and the reflected echo ga ^** (t).
And gb ^** (t) are corrected for the frequency characteristics of the ultrasonic attenuation rate of the test body S. This is because the signals described above are converted from the time axis to the frequency axis and processed.

The multiplier (57) has a corrected reflection echo ga ^** (t).
And the reference signal ha (t) are multiplied, and the similarly reflected echo gb ^** (t) and the reference signal hb (t) are also multiplied.

An inverse Fourier transformer (58) inverse Fourier transforms the result of the above two multiplications.

This correlator (5C) can bring the level of the range side lobe close to an ideal state of zero for the reason described later.

That is, the correctors (54) and (56) can also correct the frequency response characteristic of the ultrasonic probe (2), that is, the filter characteristic. For example, reference signals ha (t) and hb
(T) is determined depending on the time response characteristics u ₁ (t) and u ₂ (t) of the ultrasonic probe (2) as indicated by and. Therefore, if the frequency response characteristics are corrected on the frequency axis so that the time response characteristics u ₁ (t) and u ₂ (t) are as close as possible to the delta function, the reference signal ha (t) will be the transmission signal Sa ^** ( t) and the reference signal hb (t) approaches the transmission signal Sb ^** (t). Therefore, the level of the range side lobe can be brought close to an ideal state of zero.

By the way, in the above-mentioned correlator (5C), the reference signals ha (t) and hb (t) are Fourier-transformed by the Fourier transformer (53). The same operation and effect can be expected by storing the converted calculation result in an appropriate memory and transmitting it to the multiplier (57) when necessary.

Further, in the correlator (5C) described above, the two correctors (54) and (56) are connected, but even if one corrector is connected after the multiplier (57), the intended purpose can be achieved. It goes without saying that you will get it.

In the correlators (5B) and (5C) described above, the correlation calculation between the reflected echo and the reference signal has been described, but it can be used for the correlation calculation between the reflected echo and the transmission signal. In this case, the portion corresponding to the reference signal may be replaced with the transmission signal. Further, the correlators (5B) and (5C) may be configured by software or hardware.

In addition, it was confirmed that each of the examples has various effects described above even under the conditions described below.

By changing the number of cycles f ₀ T of the transmission signal every 0.5 to 0.5 to 3.0, the arrangement interval T 'of sin wave 0.5 per until f ₀ T~f ₀ T + 2.0 with respect to further each cycle number f ₀ T It changed and carried out.

As the test body S, a high attenuation metal such as austenitic stainless steel or titanium alloy was also tested.

Further, in the second embodiment, the reference signals ha (t) and hb
Although the actual measurement data of the reflection echo from the bottom surface of the test body S is used as (t), the same operation can be expected by using the data obtained from the calculation method described below. That is, if the acoustic material constants of each member constituting the test body S and the ultrasonic probe (2) are known, for example, “Non-destructive inspection” Vol. 30, No. 1
0, (October, 1981 issue), using the calculation method shown in P.762-767, it is possible to obtain the time response characteristic of the ultrasonic probe (2) and the frequency response characteristic which is its Fourier transform. it can.

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

FIG. 16 is a block diagram showing a third embodiment of the present invention, which is exactly the same as that of the second embodiment except the ultrasonic probe (2).

In FIG. 16, the third embodiment of the present invention is exactly the same as that of the second embodiment described above, and an ultrasonic probe (for transmitting waves) connected to a transmission signal generator (1B) ( 2A) and a receiving ultrasonic probe (2B) connected to a correlator (5A).

In the third embodiment, and u ₁ (t) of the equation uses the time response characteristic of the ultrasonic probe (2A), and u ₂ (t) is the time response of the ultrasonic probe (2B). Use characteristics.

The third embodiment of the present invention has the same operation and effect as the above-mentioned second embodiment.

Of course, the ultrasonic probe for wave transmission (2A) and the ultrasonic probe for wave reception (2B) may be applied to the first embodiment of the present invention.

Further, in the above-described third embodiment, as the first transmitting means and the second transmitting means, the same single ultrasonic probe (2
Although A) is also used, these two transmitting means may be provided individually and individually.

Further, in the above-mentioned third embodiment, the same single ultrasonic probe (2B) is used as the first receiving means and the second receiving means, but these two receiving means are used together. The means may be provided individually and individually.

Furthermore, in the above-mentioned first, second and third embodiments,
Although the same single transmission signal generator (1B) is used as the first transmission signal generation means and the second transmission signal generation means, these two transmission signal generation means are used individually. It may be provided separately.

Further, in the above-mentioned first, second and third embodiments, the same single single correlator (5A) is also used as the first correlation processing means and the second correlation processing means. , These 2
The two correlation processing means may be provided individually and individually.

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.

[Effects of the Invention] As described above, the present invention has a first transmission signal generating means for generating a first transmission signal having a sine waveform, and a sine waveform that is complementary to the first transmission signal. Second transmission signal generating means for generating a related second transmission signal;
First transmitting means that is excited by the first transmission signal to transmit a transmission wave to the object; and second transmitting means that is excited by the second transmission signal and transmits the transmission wave to the object. First receiving means for receiving a first echo corresponding to the first transmission signal, second receiving means for receiving a second echo corresponding to the second transmission signal, and the first First correlation processing means for correlating the echo by using the first reference signal defined by the first transmission signal, and the second echo by the second correlation processing means defined by the second transmission signal. Since the second correlation processing means for performing correlation processing using the reference signal and the adding means for adding the signal obtained by the first correlation processing means and the signal obtained by the second correlation processing means are provided, Accurately measure reflectors even in environments with poor S / N ratio It can be, it is possible to increase the utilization efficiency of the transmission energy, and an effect that it is possible to reduce the level of the range sidelobes.

[Brief description of drawings]

FIG. 1 is a block diagram showing the first embodiment of the present invention, and FIG.
FIGS. 3 (a) and 3 (b) are waveform diagrams showing the transmission signal of the first embodiment of the present invention, and FIGS. 3 (a) and 3 (b) are waveforms showing the result of the correlation calculation of the first embodiment of the present invention. 4 and 5 are waveform charts showing the addition result of the correlation calculation according to the first embodiment of the present invention,
FIG. 5 is a characteristic diagram showing the frequency characteristics of the transmission signal and the ultrasonic probe of the first embodiment of the present invention, and FIGS. 6 (a) and 6 (b) are other transmissions of the first embodiment of the present invention. FIG. 7 (a) and FIG. 7 (b) are waveform diagrams showing other reflected echoes of the first embodiment of the present invention, and FIGS. 8 (a) and 8 (b) are first waveform diagrams of the present invention. FIG. 9 is a waveform diagram showing the result of another correlation calculation of the embodiment, FIG. 9 is a waveform diagram showing the addition result of another correlation calculation of the first embodiment of the present invention, and FIGS. 10 (a) and 10 (b).
Is a waveform diagram showing the operation of the conventional ultrasonic nondestructive inspection device,
FIG. 11 is a block diagram showing a second embodiment of the present invention, FIGS. 12 (a) and 12 (b) are waveform diagrams showing the result of the correlation calculation of the second embodiment of the present invention, and FIG. 13 is a diagram showing the present invention. FIG. 14 is a waveform diagram showing the addition result of the correlation calculation of the second embodiment, FIG. 14 is a block diagram showing an example of the correlator of the present invention, and FIG. 15 is a block diagram showing another example of the correlator of the present invention. Fig. 16 shows the third part of this invention
FIG. 17 is a block diagram showing an embodiment, FIG. 17 is a block diagram showing a conventional ultrasonic nondestructive inspection apparatus, and FIGS. 18A to 18C are waveform diagrams showing the operation of the conventional ultrasonic nondestructive inspection apparatus. 19 (a) to 19 (c) are graphs showing the principle of correlation calculation, FIG.
FIG. 21 is a block diagram showing another conventional ultrasonic non-destructive inspection apparatus, FIGS. 21 (a) and 21 (b) are waveform diagrams showing transmission signals of another conventional ultrasonic non-destructive inspection apparatus, and FIG. It is a characteristic view which shows the transmission signal of another conventional ultrasonic nondestructive inspection device, and the frequency characteristic of an ultrasonic probe. In the figure, (1B) ... Transmission signal generator, (2) ... Ultrasonic probe, (4) ... Display, (5A) ... Correlator, (6) ... Adder, (7) ) …… Reference signal generator, (5B) …… Correlator, (50) …… Delay line with tap, (51) …… Multiplier, (52) …… Adder, (5C) …… Correlator, (53) …… Fourier transformer, (54) …… Compensator, (55) …… Fourier transformer, (56) …… Compensator, (57) …… Multiplier, (58) …… Inverse Fourier transform Vessel, (2A), (2B) ... An ultrasonic probe. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A first transmission signal generating means for generating a first transmission signal having a sine waveform, and a second transmission signal having a sine waveform and having a complementary relationship with the first transmission signal. Second transmitting signal generating means, first transmitting means that is excited by the first transmitting signal and transmits a transmitting wave to the target object, and second transmitting signal that is excited by the second transmitting signal and transmits the transmitting wave to the target object Second transmitting means, first receiving means for receiving a first echo corresponding to the first transmitting signal, second receiving means for receiving a second echo corresponding to the second transmitting signal First correlation processing means for correlating the first echo with a first reference signal defined by the first transmission signal, the second echo defined by the second transmission signal Correlation processing using a second reference signal Means, and the signal obtained by the first correlation processing means and the second signal
An ultrasonic measuring device, comprising: an addition unit that adds the signal obtained by the correlation processing unit.