KR960001825B1 - Inspecting apparatus - Google Patents

Abstract

No content.

Description

Inspection device

1 is a block diagram showing an inspection apparatus according to the prior art.

FIG. 2 is a waveform diagram showing a transmission signal from the conventional inspection device shown in FIG.

3 is a waveform diagram showing compressed pulses obtained by the conventional inspection apparatus shown in FIG.

4 is a block diagram showing a correlator of a conventional inspection apparatus.

5 is a block diagram showing a first embodiment of the present invention.

6 and 7 are waveform diagrams showing first and second basic unit signals of the first embodiment.

8 to 11 are waveform diagrams showing first to fourth transmission signals of the first embodiment.

12 and 13 are waveform diagrams showing first and second basic unit compression pulses of the first embodiment.

14 to 17 are waveform diagrams showing the results of correlation operations performed by the first correlator of the first embodiment.

18 and 19 are waveform diagrams showing third and fourth reference signals of the first embodiment.

20 to 23 are waveform diagrams showing first to fourth compression pulses of the first embodiment.

FIG. 24 is a waveform diagram showing a composite compression pulse of the first embodiment. FIG.

FIG. 25 is a waveform diagram showing the synthesized basic unit compression pulse of the first embodiment. FIG.

FIG. 26 is a waveform diagram showing another first transmission signal of the first embodiment; FIG.

FIG. 27 is a block diagram showing a specific configuration of a first correlator of the first embodiment. FIG.

FIG. 28 is a block diagram showing a specific configuration of a second correlator of the first embodiment. FIG.

29A and 29B are waveform diagrams showing other waveforms that can be used in the first embodiment.

30 is a block diagram showing a second embodiment of the present invention.

FIG. 31 is a block diagram showing a third embodiment of the present invention. FIG.

32 and 33 are waveform diagrams showing first and second basic unit signals of the third embodiment.

34 is a waveform diagram showing another unit waveform that can be used in the third embodiment.

35 to 38 are waveform diagrams showing first to fourth transmission signals of the third embodiment.

39 to 41 are block diagrams showing fourth to sixth embodiments of the present invention.

42 is a waveform diagram showing a composite compression pulse of a modification of the first embodiment.

43 is a block diagram showing a modification of the first embodiment.

* Explanation of symbols for main parts of the drawings

6: ultrasonic probe 7: analog correlator

11: first correlator 12: second correlator

15: adder

The present invention relates to an inspection apparatus using ultrasonic waves, electromagnetic waves, and the like, and more particularly, to an inspection apparatus such as an ultrasonic non-destructive inspection apparatus using a pulse compression method.

Conventional inspection apparatuses of the above-described type are described, for example, in Documents A, B, and C described below.

Document A: B. Lee and E. S. Furgason, "High-Speed Digital Golay Code Flaw Detection System", in proceedings of IEEE Ultrasonics Symposium, 1981, pp. 888-891.

Literature B: B. Lee and E. S. Furgason, "An Evaluation of Ultrasound NDE Correlation Flaw Detection Systems", IEEE Transactions on Sonics and Ultrasonics, Vol. SU-29, No. 6, Novemver, 1982, pp. 35-369.

Document C: B. Lee and E. S. Furgason, "High-Speed Digital Golay Code Flaw Detection System", Ultrasonics, July, 1983, pp. 15-161.

The configuration of the prior art will be described with reference to FIG.

1 is a block diagram showing an inspection apparatus using ultrasonic waves as shown in Document C. The inspection apparatus of FIG. 1 comprises a signal source 1, a digital delay line 2 indirectly connected to the signal source 1, a bipolar converter 3 indirectly connected to the signal source 1 and the digital delay line 2; ), A bipolar transducer 5, an ultrasonic probe 6, an ultrasonic probe 6, indirectly connected to a transmitter 4 connected to a bipolar transducer 3, a signal source 1 and a digital delay line 2, An analog correlator 7 connected to the transmitter 4 and a bipolar converter 5, an indicator 8 to which the analog correlator 7 is connected, and a system control unit 9.

The ultrasonic probe 6 is submerged in the water in the tank, and the target S to be inspected is disposed at a position facing the ultrasonic probe 6 in the tank. The analog correlator 7 is composed of a multiplier 7a connected to the ultrasonic probe 6 and the bipolar transducer 5 and an integrator 7b connected to the multiplier 7a. In addition, a logic circuit such as a NAND gate or the like is inserted 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. The system control unit is connected to each element as described above for controlling the system.

The operation of the prior art as shown in FIG. 1 will be described with reference to FIGS. 2 and 3.

2 and 3 are waveform diagrams each showing a compressed pulse signal and a transmission signal provided by the inspection apparatus as described in Document B. FIG.

In FIG. 2, the horizontal axis is shown in bits, but assuming that the unit time corresponds to a bit unit, the unit of the horizontal axis can be taken as the time unit. In Document B, the unit time corresponding to the unit bit is represented by δ. Therefore, the pulse width of the transmission signal of FIG. 2 is 63xδ.

This transmission signal includes a signal having a baseband frequency and an amplitude encoded by a specific sequence. The sequence used for encoding is explained first, and encoding of amplitude is described next.

The used sequence is a finite length sequence prepared by drawing one cycle of the maximum length sequence (M sequence), which is a cycle sequence having a period length of 63 bits.

The sequence M was co-authored by Hiroshi Miyagawa, Yoshihiro Iwatare and Hideki Imai, published on June 29, 1979 by Shokodo, "Coding Theory", p. 474-499 (hereinafter referred to as document D).

The M sequence is a periodic sequence of infinite length and is a binary sequential component consisting of two elements. Two elements may optionally be assigned the sign (+) and (-), the numbers +1 and -1 or the numbers 1 and 0. In the example shown in FIG. 2, a finite length sequence is prepared by using one cycle of M sequence having a period length of 63 bits and an infinite length.

Encoding the amplitude of the signal using this one period or finite length sequence of the M sequence will be described.

By providing one element of a finite length sequence with an amplitude of +1 and another element with an amplitude of -1, the amplitude per unit time δ is modulated to ± 1 by relative value in the order in which the two elements are represented. do. The modulated signal is called an amplitude coded signal.

Similarly to Fig. 2, in Fig. 3, the horizontal axis is expressed in units of bits. However, when a bit as a unit is regarded as a unit of time δ, the unit of the horizontal axis can be read as time.

This compressed pulse signal is an example in which a transmission signal amplitude encoded by a finite length sequence having a length of 64 bits is used. This sequence with 64 bits was prepared by adding 1 bit to the finite length sequence with 63 bits used to generate the transmission signal as shown in FIG. Therefore, the pulse width of this transmission signal is 64xδ. The pulse widths of the corresponding echo signals are also approximately the same length.

However, as shown in FIG. 3, most of the energy of the compressed pulse signal is concentrated in the center portion of the horizontal axis (time) (several bits x δ) in the figure. The portion of the signal located in the center of the transverse axis with very large amplitude is called the main lobe of the compression pulse. The pulse width of the main lobe is short. This means that, like the pulse width of the transmission signal, the energy of the echo signal distributed approximately uniformly over a long time is compressed at one point along the time axis. The part of the signal with less amplitude on both sides of the main lobe is called the range side lobe of the compression pulse.

The transmission signal as shown in FIG. 2 is generated from the signal source 1 via the digital delay line 2, the bipolar transducer 3, and the transmitter 4, and by this transmission signal, the ultrasonic probe 6 Driven to emit ultrasonic waves.

The ultrasonic waves carried out into the water in the container by the ultrasonic probe 6 are reflected by the target S and returned to the ultrasonic probe 6.

The echo signal received at the ultrasonic probe 6 is transmitted to the multiplier 7a of the analog correlator 7.

The pulse width of the echo signal has a length approximately equal to the pulse width of the transmission signal. In particular, the energy of the echo signal was distributed almost uniformly over a long time approximately corresponding to the pulse width of the transmission signal (i.e., approximately 63x? In the case of FIG. 2, approximately 64x? In the case of FIG. 3).

The same signal as the transmission signal as described above 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 signal and the transmitted signal. This correlation operation causes the energy of the echo signal, which is distributed almost uniformly along the time axis for a long time equivalent to the transmission signal, to be compressed at about one point along the time axis. The pulse signal obtained through this correlation is called a compression pulse.

The compression pulse provided by the analog correlator 7 is transmitted to the indicator 8 where the final result is displayed.

The distance resolution of the conventional inspection apparatus described above depends on the width of the main lobe of the compression pulse (hereinafter referred to as the pulse width of the compression pulse). The pulse width of the compressed pulse is short as described above even if the pulse width of the transmission signal is long. Thus, a resolution equivalent to that of a conventional inspection apparatus according to the pulse echo method using a transmission signal having a short pulse width is obtained.

On the other hand, as the average transmission energy of the transmission signal increases, the S / N ratio (signal-to-noise ratio) increases, and as the pulse width of the transmission signal increases, the average transmission energy increases. Therefore, according to the conventional inspection apparatus, a high S / N ratio can be obtained as compared with the pulse echo method using a transmission signal having a short pulse width.

As described above, the conventional inspection apparatus using the finite length sequence is excellent in resolution and can achieve high S / N ratio.

Here, the result of the correlation operation between the echo signal and the transmission signal is represented by a new function having τ as a variable and expressed by the following equation.

(One)

(Where r (t) and s (t) represent an echo signal and a transmission signal, respectively). This new function represents the compression pulse described above and is called the correlation function. If either the echo signal r (t) or the transmitted signal s (t) takes a non-zero value s within the finite time range and zeros outside the finite time range, then the integral range (-∞ to ∞) Naturally, it can be limited to a finite range of time.

As described above, according to the conventional inspection apparatus, the correlation operation between the echo signal and the transmission signal is performed using the analog correlator 7. However, since the analog correlator 7 consists only of the multiplier 7a and the integrator 7b, the operation of changing the variable tau in equation (1) must be executed externally. That is, an operation for delaying the transmission signal s (t) by τ is executed by the digital delay line 2 and the system control unit 9 so that s (t-τ) is input to the multiplier 7a. This means that

Since the operation of changing the variable τ in the relationship of equation (1) cannot be executed only in the analog correlator 7, the correlation operation is strictly meant that the analog correlator 7 is not a correlator. Also, one transmission does not provide the waveform of the compression pulse (correlation function). That is, the only result obtained in one transmission is the value of the compression pulse for a fixed arbitrary value of the variable τ. In order to obtain the waveform of the compressed pulse, one transmission must be repeated several times by changing the value of the variable τ each time it is transmitted. Therefore, it takes a relatively long time until the final result of the entire waveform of the compression pulse is obtained.

Another correlator that performs the correlation operation exactly as shown in equation (1) (exactly) will be described according to FIG.

4 is Japanese Patent Application No. A block diagram showing another correlator described in 1-45316.

In FIG. 4, the correlator 10 includes a delay line 10a having an output tap, several multipliers 10b connected to the output taps of the delay line 10a, respectively, and an adder 10c connected to these multipliers 10b. It consists of).

The correlator 10 performs correlation operation using the fact that equation (1) can be modified as follows.

(2)

(Here, the transmission signal s (t) takes zero outside the time range from 0 to T, k and ι are integers, Δt is the sampling interval, k is a constant, t = kΔt, τ = ι △ t, t = kΔt).

According to the correlator 10, Δt is the unit time delay of the delay line 10a between adjacent taps, and k is the total number of taps. When the echo signal r (t) is input to the delay line 10a, the output at the k-th tap (k = 1, 2, ..., k) is previously prepared with a weight value s (kΔt) and a multiplier 10b. Multiplied by Subsequently, the adder 10c adds the outputs from all the multipliers 10b, and the result of the addition becomes equal to the expression (2).

According to this correlator 10, the operation of changing the variable? Corresponds to inputting the echo signal r (t) to the delay line 10a at sequential timing. Of course, the echo signal r (t) is input from the ultrasonic probe 6 in sequential timing. Therefore, the operation of changing the variable τ is automatically executed. That is, according to the correlator 10 shown in FIG. 4, the time waveform of the compression pulse can be obtained in real time by only one transmission.

However, when the duration of the transmission signal, i.e., T, becomes large, a delay line 10a having a very large number of taps is required, and thus a very large number of multipliers 10b are also required. In addition, when a large number of multipliers 10b are needed, an adder 10c having a large number of input terminals is also required. As the number of multipliers 10b and the number of adders 10c increase, the operating speed of the correlator 10 decreases. In addition, the cost of such a correlator is very expensive.

Further, as shown in FIG. 3, the conventional apparatus has a defect that the level of the side lobes of the compression pulse is relatively high.

Therefore, the inspection apparatus as described above takes a lot of time to obtain the compression pulse as the final result, and if the time required to obtain the compression pulse is shortened to realize real-time inspection, the operation speed becomes slow and the price of the apparatus becomes expensive.

Moreover, there also exists a problem that the level of the side lobe of a compression pulse is high conventionally.

An object of the present invention is to solve the problems as described above, to provide an inspection apparatus that can increase the operating speed and low cost.

Another object of the present invention is to provide an inspection apparatus capable of obtaining compressed pulses having low-level, preferably zero-level side lobes in addition to being able to obtain low cost and high speed operation.

In order to achieve these objects, the inspection apparatus according to the present invention includes (1) the first and second basic unit signals ga (t) and gb (t) according to the first and second sequences {a} and {b}. ), A first transmission signal Sap (t) is generated according to the first basic unit signal ga (t) and the third sequence {p}, and the first basic unit signal ga (t) is generated. And a second transmission signal Saq (t) according to the fourth sequence {q}, and generating a third transmission signal Sbp according to the second basic unit signal gb (t) and the third sequence {p}. transmission signal generating means for generating (t) and generating a fourth transmission signal Sbq (t) according to the second basic unit signal gb (t) and the fourth sequence {q}, (2) the first Transmission means for transmitting a wave driven by the first, second, third and fourth transmission signals to a target; (3) an echo signal Rap corresponding to the first, second, third and fourth transmission signals; from the target to provide (t), Raq (t), Rbp (t) and Rbq (t) Receiving means for receiving the first, second, third and fourth echo signals, (4) the first reference signal Ua (t) generated according to the first sequence {a}; The first and second echo signals Rap (t) and Raq (t) are correlated and processed, and the third and third reference signals Ub (t) generated according to the second sequence {b} are used. A first correlation means for correlating and processing a fourth echo signal Rbp (t) and Rbq (t), and (5) a third reference signal Ip (t) generated according to the third sequence {p}. Using the first and third echo signals Rap (t) and Rbp (t) to correlate and process the outputs of the first correlating means, and generate the fourth generated sequence according to the fourth sequence q. Second correlation means for correlating and processing the outputs of said first correlation means corresponding to said second and fourth echo signals Raq (t) and Rbq (t) using four reference signals Uq (t); And (6) from said second correlating means. Adding means for adding each output is provided.

EMBODIMENT OF THE INVENTION Hereinafter, the structure of this invention is demonstrated with an Example.

In addition, in all the drawings for demonstrating an embodiment, the thing which has the same function attaches | subjects the same code | symbol, and the repeated description is abbreviate | omitted.

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

As shown in FIG. 5, the first embodiment of the present invention has the same ultrasonic probe 6 and indicator 8 and amplitude encoded transmission signal generator 1A as those of the conventional apparatus as shown in FIG. The first correlator 11 connected to the generator 1A and the ultrasonic probe 6, the first correlator and the second correlator 12 connected to the generator 1A, and the input thereof has a second correlator ( And an output 15 connected to the display 8 and having a memory function. The ultrasonic probe 6 is connected not only to the first correlator but also to the generator 1A and is in contact with the target S to be inspected.

The operation of the first embodiment will be described with reference to Figs.

6 and 7 are waveform diagrams showing the first and second basic unit signals ga (t) and gb (t), respectively, of the first embodiment.

8 to 11 are waveform diagrams showing the first to fourth transmission signals Sap (t), Saq (t), Sbp (t), and Sbq (t), respectively.

The generator 1A internally generates the first to fourth sequences {a}, {b}, {p} and {q} and is defined by the first and second sequences {a} and {b}, respectively. First and second basic unit signals ga (t) and gb (t) as shown in FIG. 6 and FIG.

The generator 1A externally generates the first to fourth transmission signals. The first transmission signal is prepared according to the third sequence {p} and the first basic unit signal ga (t), and the second transmission signal is the fourth sequence {q} and the first basic unit signal ga (t), and the third transmission signal is prepared according to the third sequence {p} and the second basic unit signal gb (t), and the fourth transmission signal is the fourth sequence {q}. And the second basic unit signal gb (t).

These first to fourth transmission signals are repeatedly generated at a constant transmission repetition period Tr, and then sequentially transmitted to the ultrasonic probe 6.

The first sequence {a} has a length M of 8 and is represented as follows.

{a} = {a ₁ , a ₂ , a ₃ , a ₄ , a ₅ , a ₆ , a ₇ , a ₈ }

{+, +, +,-, +, +,-, +}

As shown in FIG. 6, the first basic unit signal ga (t) is generated by encoding the amplitude in sequence {a}, similarly to the conventional technique shown in FIG. In FIG. 6, in order to better understand the relationship between the first sequence {a} and the amplitude coding operation, the symbols (+) and (-), which are the contents of the components of the sequence {a}, are also inserted. δ is a fixed time width.

Similarly, the second basic unit signal gb (t) is generated by encoding the amplitude in a sequence {b} of length 8 and represented as follows.

{b} = {b ₁ , b ₂ , b ₃ , b ₄ , b ₅ , b ₆ , b ₇ , b ₈ }

{+,-, +, +, +,-,-,-}

The first and second transmission signals Sap (t) and Saq (t) are shown in FIGS. 8 and 9, respectively, with signs (+) and (-) indicating the contents of the third and fourth sequential elements. It is. These sequences {p} and {q} are represented as follows.

{p} = {p ₁ , p ₂ , p ₃ , p ₄ }

{+, +, +,-}

{q} = {q ₁ , q ₂ , q ₃ , q ₄ }

{+,-, +, +}

The first transmission signal Sap (t) is generated in accordance with the following relationship.

When the element of the third sequence {p} is positive, the signal Sap (t) is assigned to the first basic unit signal ga (t), and when the element is negative, the signal ga (t) is-. The signal Sap (t) is assigned to the signal -ga (t) obtained by multiplying by one. Therefore, the first transmission signal Sap (t) is formed by arranging ga (t) and -ga (t) along the time axis in the order in which the signs (+) and (-) of the third sequence {p} appear. do.

In a similar manner, the second transmission signal Saq (t) is generated according to the fourth sequence {q} and the first basic unit signal ga (t).

10 and 11 show the third and fourth transmission signals Sbp (t) and Sbq with arrangements in the signs (+) and (-) according to the third and fourth sequences {p} and {q}. (t) is shown respectively. These signals Sbp (t) and Sbq (t), like the first and second transmission signals Sap (t) and Saq (t), are symbols of the third and fourth sequences {p} and {q} (+ Are formed by arranging the signals gb (t) and -gb (t) along the time axis in the order of "

The ultrasonic probe 6 is driven by the first to fourth transmission signals to emit ultrasonic waves to the target or the specimen S for inspection, and receives the reflection reflected from an object such as a defect in the specimen S. The received electrical echo signals corresponding to the first to fourth transmission signals, respectively, are referred to as first to fourth echo signals, and are represented by Rap (t), Raq (t), Rbp (t), and Rbq (t), respectively. Indicates.

The received first to fourth echo signals are transmitted to the first correlator 11.

On the other hand, the first reference signal Ua (t) to be used for the correlation processing of the first and second echo signals Rap (t) and Raq (t) is generated by the generator 1A to generate the first correlator 11. Is delivered to. The first reference signal is a signal related to the first sequence {a}, for example the signal ga (t). The second reference signal Ub (t), which will be used for correlation of the third and fourth echo signals Rbp (t) and Rbq (t), is also generated by the generator 1A and transferred to the first correlator 11. do. The second reference signal Ub (t) is a signal related to the second sequence {b}, for example, gb (t).

The first correlator 11 performs a correlation operation between the first echo signal Ra (t) and the first reference signal Ua (t). The result of this correlation operation is represented by Caap (t) and is called the first correlation operation result. The first correlator 11 also performs a correlation operation between the second echo signal Raq (t) and the first reference signal Ua (t). The result of this correlation operation is represented by Caaq (t) and is called the second correlation operation result. The first correlator 11 is provided between the third echo signal rbp (t) and the second reference signal Ub (t) and between the fourth echo signal Rbq (t) and the second reference signal Ub (t). Perform a correlation operation. The results of these correlation operations are denoted by Cbbp (t) and Cbbq (t), respectively, and are referred to as third and fourth correlation results.

The results of these first to fourth correlation operations of the first correlator 11 are transferred to the second correlator 12.

On the other hand, the third and fourth reference signals Up (t) and Uq (t) to be used for correlation processing in the second correlator 12 are generated by the generator 1A and transferred to the second correlator 12. . The third and fourth reference signals are signals related to the third and fourth sequences {P} and {Q}, respectively.

In the second correlator 12, between the first correlation calculation result Caap (t) and the third reference signal Up (t), the second correlation calculation result Caaq (t) and the fourth reference signal Uq (t ), Between the third correlation operation result Cbbp (t) and the third reference signal Uq (t) and between the fourth correlation operation result Cbbq (t) and the fourth reference signal Uq (t). Is executed. The results of these correlation operations in the second correlator 12 are represented by Caapp (t), Caaqq (t), Cbbpp (t) and Cbbqq (t), respectively, and are referred to as first to fourth compression pulses.

These first to fourth compression pulses are delivered to and stored in the adder 15, and these compression pulses are added as follows.

C = Caapp (t) + Caaqq (t) + Cbbpp (t) + Cbbqq (t)

The result of this addition operation is called a synthetic compression pulse.

This composite compression pulse C is transmitted from the adder 15 to the indicator 8 and displayed in the same manner as in the prior art.

The operating principle of the above-described first embodiment will be described with reference to FIGS. 12 to 25.

12 and 13 are waveform diagrams showing the first and second basic unit compression pulses according to the first embodiment of the present invention, and FIGS. 14 to 17 are the first to fourth correlation calculation results. Waveform diagrams showing Caap (t), Caaq (t), Cbbp (t) and Cbbq (t), respectively, and FIGS. 18 and 19 show the third and fourth reference signals Up (t) and Iq (t). ) Are waveform diagrams each showing FIGS. 20 to 23 are waveform diagrams showing the first to fourth compression pulses Caapp (t), Caaqq (t), Cbbpp (t) and Cbbqq (t), respectively. . 24 is a waveform diagram showing the synthesis compression pulse C, and FIG. 25 is a waveform diagram showing the synthesis basic unit compression pulses Aa (tt ₀ ) + Ab (tt ₀ ).

The first transmission signal Sap (t) shown in FIG. 8 is expressed by the following equation.

Sap (t) = p _i Ga [t- (i-1) Tp]

= p ₁ ga (t) + p ₂ Ga (t-Tp) + p ₃ Ga (t-2Tp) + p ₄ ga (t-3Tp) (3)

Here, since the signs (+) and (-) of the element p _i of the third sequence {p} are considered equal to +1 and -1, respectively, ga (t) is multiplied by p _i (the next transmission signal The same applies to).

Transmission signal Saq (t) of a second as shown in FIG. 9 is the formula (3) right-hand side in the component p _i of the third sequence {p} of the substituted expressions as elements q _i in the sequence {q} of the fourth Can be displayed. The third transmission signal sbp (t) shown in FIG. 10 is represented by an equation in which the first basic unit signal ga (t) is replaced with the second basic unit signal gb (t) at the right side of equation (3). Can be. In addition, substitutions at the right side of the fourth transmission signal Sbq (t) is the equation (3) shown in claim 11 is also a component p _i of the third sequence {p} of the elements q _i in the sequence {q} of the fourth The first basic unit signal ga (t) may be represented by substituting the second basic unit signal gb (t). The time origin is respecified for each occurrence time of the second to fourth transmission signals.

The first echo signal Rap (t) is represented by the following equation.

(4)

Here, t ₀ is a constant, and h (t) is input from the output terminal of the generator 1A to the first correlator 11 via the ultrasonic probe 6, the reflector of the test body s and the ultrasonic probe 6 again. Fourier inverse transformation of the frequency response characteristic in the signal propagation path to the terminal. In other words, h (t) represents the impulse response characteristic in the signal propagation path. t ₀ is the time required for the ultrasonic wave to reciprocate to the reflector of the test specimen s.

Generality is not lost even when Co = 1 is applied. Therefore, Co = 1 is used in the following description.

The second to fourth echo signals Raq (t), Rbp (t), and Rbq (t) represent the first transmission signal Sap (t) at the right side of equation (4) and the second to fourth transmission signals Saq ( t), Sbp (t) and Sbq (t), respectively.

The first correlation calculation side and Caap (t) are expressed as follows.

(5)

Formula

(6)

The final Caap (t) is expressed by the following equation according to equations (3) to (6).

= p ₁ Aa (tt ₂ )

+ p ₂ Aa (tt ₀ -Tp)

+ p ₃ Aa (tt ₀ -2Tp)

+ p ₄ Aa (tt ₀ -3Tp) (7)

In equation (7), Aa (tt ") drives the ultrasonic probe 6 with the first basic unit signal ga (t) to obtain an echo signal and uses the first reference signal Ua (t) as the reference signal. Corresponding to the compression pulse obtained by correlating the echo signal, this compression pulse is called the first basic unit compression pulse and is shown in FIG.

Four first basic unit compression pulses Aa (tt ₀ ) are arranged along the time axis with respect to time by 0, Tp, 2Tp and 3Tp, and the placed pulses are arranged in the third order {p} elements p ₁ , p ₂ It can be seen from Equation (7) that Caap (t) is the same as that obtained by multiplying by p ₃ and p ₄ and adding all of them.

As a result of the second correlation operation, Caaq (t) may be expressed by a formula in which the first echo signal Rap (t) is replaced with the second echo signal Raq (t) at the right side of Equation (5). This is the same as the formula in which p _i is substituted by q _i (i = 1, 2, 3, 4) on the right side of equation (7).

Similarly, as a result of the third correlation operation, Cbbp (t) replaces the first echo signal Rap (t) with the third echo signal Rbp (t) at the right side of Equation (5), and the first reference signal Ua ( It can be expressed by the formula replacing t) with the second reference signal Ub (t). This Cbbp (t) is equivalent to the formula in which Aa (t) is replaced with Ab (t) on the right side of equation (7), if the following equation (8) is applied.

(8)

Ab (t-To) corresponds to the compression pulse obtained by driving the ultrasonic probe 6 with the second basic unit signal gb (t) and correlating the echo signal using the second reference signal Ub (t). do. This compression pulse Ab (t-To) is called a 2nd basic unit compression pulse, and is shown in FIG.

As a result of the fourth correlation operation, Cbbq (t) replaces the first echo signal Rap (t) with the fourth echo signal Rbq (t) at the right side of Equation (5), and the first reference signal Ua (t). May be represented by substituting the second reference signal Ub (t). The final cbbq (t) is equivalent to a formula in which Aa (t) is replaced with Ab (t) and p _i is substituted with q _i (i = 1, 2, 3, 4) on the right side of equation (7).

The first compression pulse Caapp (t) can be expressed by the following equation.

(9)

The second compression pulse Caaqq (t) replaces the first correlation result Caap (t) with the second correlation result Caaq (t) at the right side of Equation (9) and the third reference signal Up (t). May be represented by substituting the fourth reference signal Uq (t). The third compression pulse Cbbpp (t) may be expressed by a formula in which the first correlation calculation result Caap (t) is replaced with the third correlation calculation result Cbbp (t) at the right side of Equation (9). The fourth compressed pulse Cbbqq (t) replaces the first correlation operation result Caap (t) with the fourth correlation operation result Cbbq (t) at the right side of Equation (9) and the third reference signal Up (t). May be represented by substituting the fourth reference signal Uq (t). Therefore, the second, third and fourth compression pulses Caaqq (t), Cbbpp (t) and Cbbqq (t) are expressed as follows.

The first basic unit compression pulse Aa (tt ₀ ) shown in FIG. 12 uses the signal shown in FIG. 6 as the first basic unit signal ga (t), and the first basic unit signal ga ( t) was used as the first reference signal Ua (t) and was prepared as a result of the calculation of equation (6) using h (t), which is a delta (δ) function.

The second basic unit compression pulse Ab (tt ₀ ) shown in FIG. 13 uses the signal shown in FIG. 7 as the second basic unit signal gb (t), and the second basic unit signal gb (t). t) is used as the second reference signal Ub (t), and h (t), which is a delta (δ) function, is prepared as a result of calculation of equation (8).

As a result of the first correlation calculation by the first correlator 11 shown in FIG. 14, Caap (t) is represented by the first basic unit compression pulse Aa (tt ₀ ) shown in FIG. Was prepared as a result.

The result of the second correlation calculation by the first correlator 11 shown in FIG. 15 is the same as when Caaq (t) uses the first basic unit compression pulse Aa (tt ₀ ) shown in FIG. The result of the calculation. As a result of the third and fourth correlation calculations Cbbp (t) and Cbbq (t) shown in FIGS. 16 and 17, the second basic unit compression pulse Ab (tt ₀ ) shown in FIG. 13 may be used. The same is the result of the calculation. In these calculations, Tp was set to 8δ.

14 to 17, it can be seen that the results of the first to fourth correlation calculations represent the energy dispersed along the time axis. The dispersion of energy along the time axis does not change even when Tp varies from 8δ to other time intervals.

However, the first through fourth correlation calculation results may be respectively compressed through correlation processing by the second correlator 12.

On the other hand, as the third and fourth reference signals, the signals shown in FIGS. 18 and 19 generated using the third and fourth sequences {p} and {q}, respectively, will be described.

The signal Up (t) shown in FIG. 18 has a waveform having an amplitude encoded using a third sequence {p} = {+, +, +,-}. In order to better understand the relationship between this signal and the signs (+) and (-) of the third sequence {p}, these codes are shown in correspondence with FIG.

The signal shown in FIG. 19 has a waveform having an amplitude encoded using a fourth sequence {q} = {+,-, +, +}, and is formed with the sign (+) and (-) as described above. Shown at 15 degrees.

When the third reference signal Up (t) shown in FIG. 18 is used, the first compression pulse Caapp (t) is as follows according to equation (9).

= p ₁ Caap (t)

+ p ₂ Caap (t + Tp)

+ p ₃ Caap (t + 2Tp)

+ p ₄ Caap (t + 3Tp) (10)

Here, N = 4 and the autocorrelation function of the third sequence {p} is represented by ρpp (k), [i-0, ± 1, ± 2,... (n-1)], the first compression pulse Caapp (t) is provided as follows according to equations (7) and (10).

Capp (t) = ρpp (0) Aa (tt ₀ )

+ ρpp (k) [Aa (tt ₀ -iTp) + Aa (tt ₀ + iTp)]

ρpp (0) Aa (tt ₀ )

+ ρpp (1) [Aa (tt ₀ -Tp) + Aa (tt ₀ + Tp)]

+ βpp (2) [Aa (tt ₀ -2TP) + Aa (tt ₀ + 2Tp)]

+ ρpp (3) [Aa (tt ₀ -3Tp) + Aa (tt ₀ + 3Tp)] (11)

The second compression pulse Caaqq (t) replaces Caap (t) with Caaq (t) and p _i with q _i (i = 1, 2, 3, 4) on the right side of equation (10). It may be indicated by. This substituted equation for Caaqq is equivalent to replacing the third order {p} autocorrelation function ρpp (i) with the fourth order {q} autocorrelation function ρpp (i) on the right side of equation (11) Do. The third compression pulse Cbbpp (t) may be expressed by substituting Caap (t) for Cbbp (t) on the right side of Equation (10), and Aa (t) on the right side of Equation (11) for Ab ( It is equivalent to the formula substituted by t). The fourth compression pulse Cbbqq (t) is obtained by replacing Caap (t) with Cbbq (t) and p _i with q _i (i = 1, 2, 3, 4) on the right side of Equation (10). The autocorrelation function rhopp (i) is replaced by the autocorrelation function rhoqq (i) and Aa (t) is replaced by Ab (t) on the right side of equation (11).

FIG. 20 shows the first compression pulse Caapp (t) prepared by calculating according to equation (11).

In FIG. 20, the pulse shown in FIG. 12 was used as the first basic unit compression pulse Aa (tt ₀ ), and ρpp (0) = 4, ρpp (1) -1, ρpp (2) -0 and ρpp (3) = -1 was used as the autocorrelation function ρpp (i) of the third sequence {p}. Tp was set to 8δ.

21 to 23 show the second compression pulse Caaqq (t), the third compression pulse Cbbpp (t), and the fourth compression obtained by performing the same calculation as the calculation of the first compression pulse Caapp (t), respectively. The pulses Cbbqq (t) are shown respectively. As the second basic unit compression pulse Ab (tt ₀ ), the pulse shown in FIG. 13 was adopted. In addition, as the autocorrelation function rhoqq (i) of the fourth sequence {q}, ρqq (0) = 4, ρqq (1) = -1, ρqq (2) = 0, and ρqq (3) = 1 were used. In addition, Tp = 8δ.

20 to 23, it can be seen that most of the signal energy of each of the first to fourth compression pulses is concentrated around t = t ₀ . That is, it has a large amplitude only near t = t ₀ , and has some small level of side lobes. However, the sidelobe is still relatively large even at a time position where time t is significantly away from t ₀ .

FIG. 24 shows the synthetic compression pulse C prepared by adding the first to fourth compression pulses, that is, C = Caapp (t) + Caaqq (t) + Cbbpp (t) + Cbbqq (t). In the synthetic compression pulse C, according to the addition operation, as shown in FIG. 24, the main lobes of the pulses Caapp (t), Caaqq (t), Cbbpp (t) and Cbbqq (t) are strong, and their side lobes. Offsets to zero.

Therefore, since a compressed pulse having a main lobe having a large amplitude at t = t ₀ and no side lobe can be obtained by the embodiment of the present invention described above, it is possible to easily detect the value of t ₀ . Able to know.

Further, when the first and second basic unit compression pulses Aa (tt ₀ ) and Ab (tt ₀ ) are added together, the pulses are used as the main lobe only in the vicinity of t = t ₀ , as shown in FIG. 25. It can also be seen that the amplitude is large and the amplitude in the other range is zero. This means that if the autocorrelation functions of the first and second sequences {a} and {b} are represented by ρaa (i) and ρbb (i), then ρaa (0) = ρbb (0) and ρaa (i) =-ρbb (i) derived from the fact that (i = 1, 2, ... M-1) can be used. This relationship between Aa (tt ₀ ) and Ab (tt ₀ ) or {a} and {b} may be referred to as a complementary relationship.

Similarly, between the third and fourth sequences {p} and {q}, ρpp (0) -ρqq (0) and ρpp (i) =-ρqq (i) (i = 1,2, ... N-1) Can also be used at Therefore, in the above-described embodiment, the first and second sequences {a} and {b} form a complementary relationship, and the third and fourth sequences {p} and {q} also form a complementary relationship.

The other effect obtained by the 1st Example of this invention is demonstrated.

In this kind of inspection apparatus, the improvement of the S / N ratio is further enhanced as the width of the transmission pulse signal becomes larger. In order to make the pulse width of the transmission signal longer, it is necessary to use a sequence having a longer sequence length.

According to the first embodiment of the present invention, as can be seen from FIGS. 8 to 11, the pulse width of the transmission signal is not only the first and second sequences {a} and {b} of the length M but also the first. It also depends on the length N of the third and fourth sequences {p} and {q}. As the length N of the third and fourth cycles becomes larger, the pulse width of the transmission signal becomes correspondingly larger.

These sequences with complementary relationships cannot exist at any length, but at a particular sequence length. According to the first embodiment of the present invention, since two types of sequential lengths M and N are used in combination, the actual sequential length of the transmission signal is M × N.

Therefore, the pulse width of the transmission signal can be made larger, so that the S / N ratio can be improved. In addition, by combining different lengths M and N, the degree of freedom of the pulse width with respect to the transmission signal can be increased.

Another effect of the first embodiment of the present invention will be described with reference to FIGS. 26 to 28. FIG.

FIG. 26 is a waveform diagram showing another first transmission signal Sap (t) when Tp = 8? According to the first embodiment of the present invention.

27 and 28 are block diagrams showing the configuration of the first and second correlators 11 and 12.

The first transmission signal shown in FIG. 26 is equivalent to a signal having an amplitude encoded using the following sequence.

{+, +, +,-, +, +,-, +,

+, +, +,-, +, +,-, +,

+, +, +,-, +, +,-, +,

-,-,-, +,-,-, +,-}

The sequence is equal to the following sequence having a length of 32 obtained using the first and third sequences {a} and {p}.

a ₁ p ₁ , a ₂ p ₁ , a ₂ p ₁ , a ₄ p ₁ , a ₅ p ₁ , a ₆ p ₁ , a ₇ p ₁ , a ₈ p ₁

a ₁ p ₂ , a ₂ p ₂ , a ₂ p ₂ , a ₄ p ₂ , a ₅ p ₂ , a ₆ p ₂ , a ₇ p ₂ , a ₈ p ₂

a ₁ p ₃ , a ₂ p ₃ , a ₂ p ₃ , a ₄ p ₃ , a ₅ p ₃ , a ₆ p ₃ , a ₇ p ₃ , a ₈ p ₃

a ₁ p ₄ , a ₂ p ₄ , a ₂ p ₄ , a ₄ p ₄ , a ₅ p ₄ , a ₆ p ₄ , a ₇ p ₄ , a ₈ p ₄

Here, the signs (+) and (-) are assumed to be equal to +1 and -1, so a multiplication operation is used.

Next, consider the case where the first transmission signal shown in FIG. 26 having a long pulse width is adopted as the transmission signal of the conventional apparatus shown in FIGS. 1 and 4 in order to improve the S / N ratio. do.

The duration T of the transmission signal is 32δ as shown in FIG. Therefore, when the sampling of K ₁ per unit time δ is performed and the correlator 10 shown in FIG. 4 is configured according to equation (2), the delay line having K = 32 × K ₁ taps is a multiplier. (10b) rosseoneun 32 × K ₁ of the multiplier, the adder (10c) rosseoneun need adder having a 32 × K ₁ input terminals.

The inspection apparatus according to the first embodiment of the present invention uses the first basic unit signal ga (t) as the first reference signal, and as shown in FIG. 6, the first basic unit signal ga ( The width of t) is 8xδ. Therefore, if equation (5) is modified as in equation (2), and sampling at K ₁ is performed for the unit time δ, the first correlator 11 is configured as shown in FIG.

27 as shown in Fig., The correlator 11 is 8 × K ₁ output delay line having a tab (11a), the 8 × K ₁ of connection to each output tap of the delay line (11a) of the first consists of a multiplier (11b) and the multiplier (11b) of 8 × adder (11c) K having _one input terminal connected to.

Next, a second correlator 12 of the inspection apparatus according to the first embodiment of the present invention is considered.

The second correlator 12 may be allowed if the function of calculating the right side of the equation (10) is provided according to the first correlation calculation result Caap (t) by the first correlator 11. The right side of expression 10 × p ₃ Caap (+) in Caap (t) × p _1, time (t + Tp) Caap (t) × p _2, time (t + 2Tp) at at time t , Caap (t) × p ₄ at time t + 3Tp, all of which are added together. Therefore, assuming that K ₁ sampling is performed for the unit time δ, Tp = 8δ, so the second correlator 12 may be configured as shown in FIG.

In particular, it may be configured as shown in FIG.

In particular, in the 28 degrees, the second correlator 12 includes a delay line (12a), 8 × K ₁ output tapped delay line (12a) each time (corresponding to each Tp) having a _single output tap 24ρK It consists of four multipliers 12b connected to the output tap and an adder 12c having four input terminals connected to the multiplier.

Here, the total number of the multipliers 11b and 12b required by the first and second correlators 11 and the second correlators 11 and 12 of the first embodiment of the present invention is known. It compares with the number of multipliers 10b required by the correlator 10 shown in FIG. According to the first embodiment of the present invention, a total (8 × K ₁ +4) multipliers are required, whereas for the conventional apparatus, 32 × K ₁ multipliers are required. That is, according to the first embodiment of the present invention, a plurality of multipliers can be reduced. By reducing the number of multipliers, the speed of operation of the device and the cost can be reduced.

In addition, the weighting pi (i = 1, 2, 3, 4) of the multiplier 12b required for the second correlator 12 is one of ± 1 according to the first embodiment described above. If the weight is +1, it means that multiplier 12b is not needed. If the weight is -1, it means that the multiplier 12b should be replaced with an inverter. Thus, the first embodiment of the present invention is more advantageous for high speed and low cost.

Next, a similar comparison is made with an adder. The first embodiment of the present invention requires an adder having an adder (11c) and fourth input terminals with a 8 × K ₁ input terminals. On the other hand, the conventional apparatus requires an adder having 32 × K ₁ input terminals. In general, the adder operates to accumulate input values, so that the smaller the number of required input terminals, the more the operation speed can be increased and the cost can be further reduced. Thus, the first embodiment is more advantageous.

For the correlation processing of the second echo signal, the same correlator as shown in FIG. 27 can be used as the first correlator 11, and weighted p _i (i = 1, 2, 3 for the multiplier 12b). The second correlator 12 shown in FIG. 28 in which 4 is substituted with qi can be used.

For correlation processing of the third echo signal, shown in FIG. 27 in which weighted Ua (kΔt) (k = 1, 2, ..., 8ki) is replaced by Ub (kΔt) for the multiplier 11b. One correlator may be used as the first correlator 11 and the same as that shown in FIG. 28 may be used as the second correlator 12.

As for the correlation processing of the fourth echo signal, as the first correlator 11, the weighted Ua (kΔt) (k = 1, 2, ..., 8K is applied to the multiplier 11b in the correlator shown in FIG. _i ) may be substituted with Ub (kΔt), and as the second correlator 12, weighted p _i (i = 1, 2, 3) to the multiplier 12b in the correlator shown in FIG. And 4) may be substituted with qi. Alternatively, the first and second correlators may be separately provided for the correlation processing of the second, third and fourth echo signals.

As for the first embodiment described above, as shown in Figs. 6 and 7, the unit waveforms corresponding to the respective elements (±) of the first and second sequences {a} and {b} are shown in Figs. It demonstrated as square in the 1st and 2nd basic unit signal. However, even if the unit waveform is deformed to the shape shown in FIG. 29 (a) or 29 (b) rather than a rectangle, the above-described operation and effects can be obtained in the same manner.

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

In this figure, the first and second correlators 11 and 12, the adder 15, the ultrasonic probe 6 and the indicator 8 are the same as in the first embodiment, but with an amplitude coded transmission signal generator. 1A does not have the same configuration and function as the generator 1A of the first embodiment. That is, in the second embodiment, the generator 1A uses the first to fourth transmission signals Sap (t), Saq (t), Sbp (t) and Sbq (t) in the same manner as in the first embodiment. Is generated, but the first to fourth reference signals Ua (t), Ub (t), Up (t), and Uq (t) do not occur. Instead, the first to fourth reference signal generators 13A, 13B, 14A, and 14B are incorporated as shown in FIG.

The generators 13A and 13B are enabled by the transmission signal generator 1A and obtained when the ultrasonic probe 6 is driven by the first and second basic unit signals ga (t) and gb (t). Generate first and second reference signals, each having a waveform identical or similar to the waveform of the echo signal. These generated reference signals are transmitted to the first correlator 11.

On the other hand, the generators 14A and 14B are enabled by the generator 1A and have the same or similar waveforms as the third and fourth reference signals Up (t) and Uq (t) in the first embodiment. Third and fourth reference signals having the same and are supplied to the second correlator 12.

The reference signal generated by the generators 13A and 13B is the same or similar to the signal indicated by the substitution of Sap (t) by ga (t) and gb (t) on the right side of equation (4). Therefore, each of the generators 13A and 13B has frequency response characteristics relating to ultrasonic reflections from reflection portions such as frequency response characteristics in the transmission and reception of the ultrasonic probe 6, frequency response characteristics of the specimen S, defects in the specimen S, and the like. Functions as a filter with

The correlation processing of the echo signal by using a reference signal having the same or similar waveform as the waveform of the echo signal such as the first and second reference signals generated by the generators 13A and 13B is a signal hidden in the noise. Equivalent to signal processing that allows an echo signal to pass through a quasi-matching filter or matched filter, which is effective to receive a maximum S / N ratio.

Accordingly, the second embodiment of the present invention, in addition to the advantages provided by the first embodiment using the first and second basic unit signals themselves as reference signals for the first correlator 11, There is an advantage of further improving the S / N ratio.

It will be appreciated that the generators 13A and 13B may be allowed if they have the function of generating the next reference signal.

First, when the ultrasonic probe 6 is driven by the first basic unit signal ga (t), it is reflected from the front or the bottom of the test body S so that the reflection of the surface or the bottom received by the ultrasonic probe 6 is measured and large. When providing the S / N ratio, the waveform of the echo signal corresponding to the surface or bottom echo is measured, and the first reference signal generator 13A is a signal having the same or similar waveform as the measured waveform as the first reference signal. Caused by). The second reference signal from the second reference signal generator 13B is similarly generated, but the second basic unit signal gb (t) is used instead of the first basic unit signal.

If a sufficient S / N ratio cannot be obtained due to reflections reflected from the front or bottom face of specimen S, another specimen S ₁ shall be prepared. Then, as above, the ultrasonic probe 6 is driven by the first and second basic unit signals ga (t) and gb (t), respectively, and the echo reflected from the test body S ₁ is transmitted to the ultrasonic probe 6. Are received by the generators 13A and 13B as reference signals.

When the ultrasonic probe 6 is generated by the first basic unit signal, the ultrasonic probe 6 passes through the ultrasonic probe 6 and the test body S from the amplitude encoded transmission signal generator 1A of the first basic unit signal. The correlator 13A may be configured to generate a reference signal having a waveform calculated according to the frequency response characteristic of the signal transmission path to the input terminal of the first correlator 11 via s). Similarly, the correlator 13B may be configured in consideration of the second basic unit signal. In these cases, the S / N ratio is further improved by including the frequency response characteristic of the reflection by the reflector in the test body S in the frequency response characteristic of the signal transmission path.

In addition, when a plurality of first and second reference signals having different frequency response characteristics with respect to reflections from the reflector in the test object S are prepared to be generated, the function of discriminating the reflector is a Japanese patent in the field of the present invention. Application No. Additionally as described in 86383/89.

Regarding the third and fourth reference signal generators, the generators 14A and 14B may be configured to generate, as the third and fourth reference signals, a signal whose amplitude is slightly converted from +/- 1 for each time Tp. The third and fourth signals for enabling the synthetic compression pulse C or the first to fourth compression pulses Caapp (t), Caaqq (t), Cbbpp (t), and Cbbqq (t) provided at a high S / N ratio. It may be generated as a reference signal.

When that point is present the problem embodiment _three samples K to the duration of the first or second reference signal by an example of the second and the duration Tp of K ₂ sampling in the invention, as with the method shown in Claim 27 is also the The correlator 11 of 1 has a delay line having K ₃ taps, a K ₃ multiplier connected to each of the output taps of the delay line, and K ₃ inputs, as can be seen by changing equation (5) to equation (2). It is good to be comprised with the adder which has a terminal. The second correlator 12 has a delay line having (N-1) × K ₂ taps, N multipliers connected to the output taps of the delay line every K ₂ taps, and N, similar to the method shown in FIG. It is sufficient to be configured with an adder having two input terminals. Weighting p _i and q _i (i = 1, 2, 3, ..., N) with N multipliers may be performed as ±, or as described above, the first to fourth compression pulses and the synthetic compression pulse are high. It may vary from ± 1 for each i so as to be obtained with an S / N ratio.

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

The third embodiment includes the same components as those of the first embodiment except that the phase coded transmission signal generator 1B replaces the amplitude coded transmission signal generator 1A of the first embodiment.

The operation of the third embodiment will be described with reference to Figs.

32 and 33 are waveform diagrams showing the first and second basic unit signals ga (t) and gb (t) of the third embodiment. 34A and 34B are waveform diagrams showing other unit waveforms that constitute the basic unit signal. 35 to 38 show waveforms of the first to fourth transmission signals Sap (t), saq (t), Sbp (t), and sbq (t), respectively.

In FIG. 32, the first basic unit signal ga (t) is a signal generated using the same first sequence {a} as in the first embodiment, and δ and δ ₀ represent a fixed time. In order to easily understand the relationship between the first sequence {a} and the first basic unit signal ga (t), the signs (+) and (-) of the first sequence {a} are also shown in the figures.

In FIG. 33, the second basic unit signal gb (t) is a signal generated using the second sequence {b} which is the same as in the first embodiment. The signs (+) and (-) of the second sequence {b} are also shown in the figure.

32 and 33, the unit waveforms shown corresponding to the elements (+) and (-) of the first or second sequences {a} and {b} are shown as sinusoids. The unit waveform described above may be a waveform having a gentle curve or an oscillation waveform having an intersection point with an uneven constant amplitude or zero, as shown in FIG. 34 (a) or (b).

When δ = δ ₀ , it can be seen from FIGS. 32 and 33 that the first and second basic unit signals ga (t) and gb (t) may have a phase coded waveform. The method of encoding a phase is described in Japanese Patent Application No. It is described in detail in 45316/89.

In FIG. 35, the first transmission signal Sap (t) is obtained by using the same third sequence {p} as in the first embodiment and the first basic unit signal ga (t) shown in FIG. This signal is generated in the same steps as in the first embodiment. In particular, the first basic unit signal ga (t) is assigned to the sign (+) of the third sequence {p}, and the signal -ga (t) obtained by multiplying the first basic unit signal ga (t) by -1. ) Is assigned to the sign (-), and ± ga (t) is arranged along the time axis in the order in which the sign of the third sequence {p} appears. In order to easily understand the relationship between the sign (+) and (-) of the third sequence {p} and the signal ± ga (t), the sign of the third sequence {p} is also shown in the figure.

In FIG. 36, the second transmission signal Saq (t) is the same as the fourth sequence {q} used in the first embodiment and the first basic unit signal ga (t) shown in FIG. The signal is generated in the same steps as in the first embodiment. Similarly to FIG. 35, the signs (+) and (-) of the sequence {q} of FIG. 4 are also shown in the figure.

In FIG. 37, the third public signal Sbp (t) is the first according to the same third sequence {p} as in the first embodiment and the second basic unit signal gb (t) shown in FIG. Codes (+) and (-), which are signals generated in the same steps as in the embodiment of Fig. 3 and correspond to element codes of the third sequence {p}, are also shown.

In FIG. 38, the fourth transmission signal Sbq (t) is the first in accordance with the same fourth sequence {q} as in the first embodiment and the second basic unit signal gb (t) shown in FIG. These signals are generated in the same steps as in the embodiment of the present invention, and the signs (+) and (-) correspond to the element codes of the fourth sequence {q}.

According to the third embodiment, the first, second, third and fourth transmission signals shown in FIGS. 35 to 38 are routed to the phase coded transmission signal generator 1B to drive the ultrasonic probe 6. Supplied from. Signal processing of the echo signal is the same as in the first embodiment. That is, in the third embodiment, the first basic unit signal ga (t) shown in FIG. 32 is used as the first reference signal for the first correlator 11, and the third shown in FIG. The basic unit signal gb (t) of 2 is used as the second reference signal for the correlator 11, and the same signal as the third and fourth reference signals of the first embodiment is sent to the second correlator 12. It is used as the third and fourth reference signals.

Further, according to the third embodiment, equations (3) to (11) can be applied irrespective of the first basic unit signal ga (t) waveform, and the equations (6) and (8) in FIG. 32 and The synthesized basic unit compression pulse resulting from the addition of the first and second basic unit compression pulses Aa (t) and Ab (t) obtained using the first and second basic unit signals shown in FIG. 33 is t. Since a large amplitude is provided only around = t ₀ , the amplitude is zero, that is, Aa (t) and Ab (t) are complementary, and the third and fourth sequences {p} and {q} are complementary. The same operation and advantages as in the first embodiment are provided. The correlation as described above between the first and second basic unit compression pulses holds even when the unit waveforms shown in FIG. 34 (a) or 34 (b) are used. The same effect as in the example can be obtained.

As described above, the third embodiment has the same operation and effect as the first embodiment. In addition, Japanese Patent Application No. As can be seen from 45316/89 and 86383/89, in the third embodiment, the frequency characteristic is characterized by the frequency characteristic in the transmission and reception of the ultrasonic probe 6, the frequency characteristic of the specimen S and the frequency of the ultrasonic reflection of the reflector in the specimen S. The characteristics can be made closer to the synthesized frequency characteristics.

Therefore, high utilization efficiency of signal energy can be expected. As shown in the period δ ₀ or 34 (a) or 34 (b) of FIG. 32 or 33, the elements (+) of the first and second sequences {a} and {b} and When the unit waveform corresponding to (-) is selected to have a frequency characteristic close to the synthesized frequency characteristic as described above, the S / N ratio can be increased by greatly improving the utilization efficiency of signal energy.

When the first correlator 11 and the second correlator 12 are composed of delay lines, multipliers, and adders having taps, the same configuration as that of the first embodiment can be adopted.

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

The fourth embodiment includes the same components as those of the second embodiment described above, except that the phase coded transmission signal generator 1B is adopted in place of the amplitude coded transmission signal generator of the second embodiment. .

In the third embodiment, the first and second reference signal generators 13A having the same or similar waveform as the echo signal obtained when the ultrasonic probe 6 is driven with the signals ga (t) and gb (t). The generator 1B generates the first and second basic unit signals ga (t) and gb (t), which are the same as those of the third embodiment, for each of (13B).

The third and fourth reference signal generators 14A and 14B respectively generate third and fourth reference signals having waveforms the same as or similar to those in the third embodiment to generate a second correlator 12. To pass).

In the fourth embodiment, the first and second reference signals are set to Sap (t) on the right side of equation (4), respectively, and the first and second basic unit signals ga (t) and in the third embodiment. This signal is the same as or similar to the signal obtained by replacing gb (t). Therefore, the fourth embodiment has the same advantages as the second embodiment in addition to the advantages of the third embodiment.

In the fourth embodiment, the generators 13A and 13B may be configured in other formats similar to those described in connection with the second embodiment.

Also, in the fourth embodiment, the generators 14A and 14B, like the second embodiment, generate signals as the third and fourth reference signals having a slightly converted amplitude from ± 1 per Tp. It may be configured to. That is, it is sufficient to generate the third and fourth reference signals having waveforms such that the first to fourth compressed pulses or the synthesized compressed pulses are obtained at a high S / N ratio.

The first correlator 11 and the second correlator 12 may be configured in the same manner as in the second embodiment.

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

The fifth embodiment includes the same components as those of the fourth embodiment except that the transmitting ultrasonic and probe 6A and the receiving ultrasonic probe 6B are adopted in this embodiment.

The fifth embodiment has an effect similar to that of the fourth embodiment.

Of course, the ultrasonic probes 6A and 6B can 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.

The sixth embodiment is the fifth correlator shown in FIG. 40 except that the third correlator 16, the fifth and sixth reference signal generators 17A and 17B are newly incorporated in this embodiment. The configuration is the same as in the embodiment.

The generators 17A and 17B are connected to receive a signal from the phase coded transmission signal generator 1B, and the third correlator 16 connects the second correlator 12 and the generators 17A and 17B. It is connected to receive a signal from and supply its output signal to the adder 15.

According to the sixth embodiment, the transmission signal generator 1B newly generates the fifth and sixth sequences {v} and {w}, as shown in FIGS. 35 to 38 with respect to the fifth embodiment. The first to fourth transmission signals Sap (t), Saq (t), Sbp (t), and Sbq (t) are divided into g ₁ (t), g ₂ (t), g ₃ (t), and g ₄ ( A new first transmission signal is generated by using the new first to fourth basic unit signals indicated by t) and using the fifth sequence {v} and the first basic unit signal g ₁ (t). do. The step of generating this first transmission signal is the first transmission signal Sap (t) using the first basic unit signal ga (t) and the third sequence {p}, as applied in the fifth embodiment. Follow the same steps as the step of generating).

That is, the first basic unit signal g1 (t) is assigned to the element code (+) of the fifth sequence {v}, and the signal -g obtained by multiplying -1 by the first basic unit signal g ₁ (t) ₁ (t) is applied to the element code (-) of the fifth sequence {v}, and these signals g ₁ (t) and -g ₁ (t) are the signs (+) of the fifth sequence {v} and They are arranged in the order in which they appear. The duration for each sign is determined as Tpp.

Further, in the same manner, the sequential {v} and the second basic unit signals g ₂ (t), the sequential {v} and the third basic unit signals g ₃ (t) and the sequential {v} and the fourth basic units Signals g ₄ (t) and sequential {v} are used to generate new second, third and fourth transmission signals, respectively. Further, the sixth sequential {w} and the first basic unit signals g ₁ (t), the sequential {w} and the second basic unit signals g ₃ (t), and the sequential {w} and the third basic units The fifth to eighth transmission signals are generated using the signal g ₃ (t), the sequential {w} and the fourth basic unit signal g ₄ (t), respectively.

These first to eighth transmission signals are transmitted to the ultrasonic probe 6A at regular repetition cycles.

Generators 17A and 17B generate fifth and sixth reference signals, respectively, that are the same or similar to the signal amplitude encoded using the fifth and sixth sequences {v} and {w} to generate a third correlator. Deliver them to 16.

The correlator 16 performs correlation processing of the output from the second correlator 13 with respect to the first to fourth transmission signals using the fifth reference signal. In addition, correlation processing of the output from the correlator 12 is performed on the fifth to eighth transmission signals using the sixth reference signal, and the result of these correlation processing is transmitted to the adder 15.

The adder 15 stores the results from the third correlator 16 for the first to eighth transmission signals, adds them to obtain a composite compression pulse, and delivers this composite compression pulse to the display 8. .

In this case, if the fifth and sixth sequences {v} and {w} are complementary, the combined compression pulses provide a zero range side lobe.

Also, when the third correlator 16 is composed of delay lines, multipliers, and adders with taps, this configuration is the same as that of the second correlator 12. However, if the length of each of the fifth and sixth sequential {v} and {w} is L, a total of L multipliers must be provided to be connected to output taps that are separated from each other in correspondence to the time interval Tpp. The adder must also have L input terminals.

According to the sixth embodiment, the duration of each transmission signal can be longer than in the case of the fifth embodiment. In this way, the longer the duration of the transmission signal, the number of multipliers as well as the number of input terminals of the adder is significantly reduced compared to the above-described prior art, which is more advantageous in terms of operating speed and cost.

Further, in the sixth embodiment, the seventh and eighth corresponding to the newly assumed basic unit signal by repeating the step of generating the transmission signal or by repeatedly repeating the waveform of the transmission signal as a new basic unit signal. , Ninth, tenth,... , Reference signal generator and fourth, fifth,... By providing a correlator, the duration of the new synthesized signal S becomes longer, so that the number of multipliers between the prior art that can generate a long duration transmission signal similar to the inspection apparatus capable of generating the new synthesized transmission signal, and The difference in the number of input terminals of the adder is gradually increased, which is more advantageous for the operation speed and cost.

As described above with respect to the sixth embodiment, the generation step of the synthesized transmission signal having a long duration can of course also be applied to the first to fourth embodiments.

Hereinafter, various modifications will be described.

First, the second sequence {b} is not used for the generator 1A of the first embodiment shown in FIG. 5, so that the second reference signal Ub (t), the third and fourth transmission signals Sbp ( Modifications in which t) and Sbq (t) are also not generated from the generator 1A will be described.

In this case, the synthesized transmission signal S from the generator 1A consists of the first and second transmission signals Sap (t) and Saq (t), so that the synthesized echo signal R is the first and second echo signals Rap. (t) and Raq (t) but not the third and fourth echo signals Rbp (t) and Rbq (t).

The first correlator 1 performs a correlation operation between the first reference signal Ua (t) and the first and second echo signals Rap (t) and Raq (t) to produce a correlation result Caap (t) and Caaq. (t), and the second correlator 12 performs correlation between Caap (t) and the third reference signal Up (t) and between correlation result Caaq (t) and the fourth reference signal Uq (t). Is performed to prepare the first and second correlation results Caapp (t) and Caaqq (t). These results are then added in adder 15 to provide a composite compression pulse C.

As can be seen from FIGS. 20 to 24, Caapp (t) and Caaqq (t) are not added with the resulting Caapp (t) and Caaqq (t), so the compression pulse C = Caapp (t) + Caaqq ( t) represents the non-zero side lobe of some amplitude as shown in FIG. 42, compared to the pulse C = Caapp (t) + Caaqq (t) + Cbbpp (t) + Cbbqq (t) shown in FIG. Have

In equation (11), Caapp (t) is represented as follows.

Caaqq (t) = ρqq (0) Aa (tt ₀ )

+ ρqq (1) [Aa (tt ₀ -Tp) + Aa (tt ₀ + Tp)]

+ ρqq (2) [Aa (tt ₀ -2Tp) + Aa (tt ₀ + 2Tp)]

+ ρqq (3) [Aa (tt ₀ -3TP) + Aa (tt ₀ + 3Tp)]

As the third and fourth sequences are complementary as described above,

ρpp (0) = ρqq (0)

ρpp (1) =-ρqq (1)

ρpp (2) =-ρqq (2)

ρpp (3) =-ρqq (3)

therefore,

Caapp (t) + Caaqq (t) = 2ρpp (0) Aa (tt ₀ ) (12)

In equation (12), if the first basic unit compression pulse Aa (tt ₀ ) has a substantially small side lobe, the compression pulse C = Caapp (t) + Caaqq (t) also has a substantially small side lobe.

The Barker sequence is a known sequence, so the autocorrelation function with small side lobes, such as the Barker sequence, is adopted as the first sequence {a} and the pulses are not used when the second sequence {b} is not used. The side lobe of C can be reduced.

In addition, the modification does not use not only the second sequence {b} but also the fourth sequence {q}.

In this case, since the transmission signal s includes only the first transmission signal Sap (t), the echo signal R includes only the first reflection signal Rap (t).

The correlation result in the first correlator 11 is only Caap (t) given from the first reference signal Ua (t) and the first echo signal Rap (t). The compression pulse C or correlation result in the second correlator 12 is only Caapp (t) as shown in FIG. 20 given from the final Caap (t) and the third reference signal Up (t).

The final Caapp (t) can be expressed as Equation (11). In other words,

Caapp (t) = ρqq (0) Aa (tt ₀ )

+ ρqq (1) [Aa (tt ₀ -Tp) + Aa (tt ₀ + Tp)]

+ ρqq (2) [Aa (tt ₀ -2TP) + Aa (tt ₀ + 2Tp)]

+ ρqq (3) [Aa (tt ₀ -3TP) + Aa (tt ₀ + 3Tp)]

Although the compression pulse Caapp (t) has a side lobe with some amplitude as shown in FIG. 20, the autocorrelation function value ρpp (0) is sufficiently larger than other ρpp (1) to ρpp (3), and If the basic unit compression pulse Aa (tt ₀ ) has a sufficiently large amplitude at tt ₀ (main lobe) and is closer to it than at other times t (side lobe), then the amplitude of the side lobe is changed to the main lobe at t = t ₀ . It can be lowered sufficiently.

As in the first variant, it is clear that the latter condition will be satisfied by the Barker sequential circulation {a}. Therefore, the Barker sequence is used as the first sequence {a}, and the autocorrelation function ρpp (i) of the third sequence {p} is different (i If it has a sufficiently large value at i = 0 compared with 1), the second modification can induce the same effect as in the first embodiment. In this case, since the compression pulse C includes only Caapp (t), the adder 15 of the first embodiment can be ignored as shown in FIG.

The above modified example described with respect to the first embodiment can also be applied to the second to fourth embodiments.

In each embodiment described so far, the length M of the first and second sequences {a} and {b} is 8 and the length N of the third and fourth sequences {p} and {q} is 4. Any natural number may be applied to the lengths M and N.

For example, if the first basic unit signal is used as the first reference signal and there are K ₁ sampling points in the period δ, let each of the lengths M and N be any natural number including one.

If TP = Mδ, each connected to a correlator 11 of the first output tap of the delay line (11a), a delay line (11a) in the same manner help of claim 27, having a M × K ₁ output tab M × K can be composed of _one multiplier (11b) and an adder (11c) having a M × K ₁ input terminal. In the same manner as in FIG. 28, the second correlator 12 has a delay line 12a having (N-1) × M × K output taps and a delay line 12a for each (M × K ₁ ) th tap. The multiplier 12c has N multipliers and N input terminals connected to the output taps.

As compared with the above-described embodiment, the correlator 10 of the conventional apparatus (FIG. 4) is M × N × delay having a K ₁ output tap line (10a), connected to the output tabs each M × N × K ₁ the multipliers (10b), and M × N × K ₁ of input terminals, so the need to obtain the same effects as those of the above-described embodiment, more input terminals of the large number of multipliers and adders are required.

Next, the case where Tp> Mδ or Tp <Mδ is considered. In these situations, that the period Tp dots of K ₂ sampling, as the degree of claim 27 method, the correlator 11 of the ₁ M × K 1 of tap delay line (11a), a delay line (11a) having a It may be composed of the M × K ₁ multipliers and an adder (11c) having a M × K ₁ input terminals connected to respective Tam. Claim the N connection like the 28-degree method, the output tap of the correlator 12 of the 2 (N-1) × K ₂ delay line (12a), a delay line (12a) each K ₂ second tab having tabs The multiplier 12b and the adder 12c having N input terminals can be configured. By this configuration, the same effects as in the above-described embodiment can be obtained. That is, the number of input terminals of the multiplier and the adder is reduced in comparison with the corresponding prior art.

If M = 1, the waveforms of the first and second basic unit signals are equivalent to unit waveforms such as rectangular waveforms, quasi rectangular waveforms, sinusoidal waveforms, waveforms with gentle curves, or vibration waveforms. Therefore, in this case, the first correlator 11 may be removed in the first and third embodiments. In the second, fourth, fifth and sixth embodiments, the first correlator 11 may be left as a matched filter or a pseudo matched filter. In the case where N = 1, the second correlator 12 may be removed in the first to sixth embodiments.

In addition, if there are generally K ₃ sampling points within the duration of the first reference signal and K ₂ sampling points within the period of Tp, the first correlator 11 may have K ₃ taps as in the method of FIG. 24. a delay line (11a), may be configured in a K ₃ of the multiplier (11b) and an adder (11c) having a K ₃ input terminals connected to a respective tap of the delay line (11a) having. The connected to the correlator 12 of the second tabs of the first 28 method, like degrees, (N-1) × K ₂ delay line (12a), a delay line (12a) each K ₂ second tab having taps the N You may comprise the multiplier 12b and the adder 12c which has N input terminals. These configurations also have the same effects and effects as the above-described embodiment.

In each of the above embodiments, the impulse response h (t) is a delta function. The present invention is not limited to these embodiments, and similar effects and effects can be expected as when the h (t) is any function, for example, a function having a vibrating waveform portion.

In each of the above-described embodiments, the first and second sequences are complementary. The present invention is not limited to these examples, and the same effects and effects as the above embodiments can be expected even when the first and second basic unit compression pulses are complementary.

In each of the above-described embodiments, the embodiments in which the third and fourth sequences are complementary have been described, but the present invention is not limited thereto. If the addition result of the first and third compression pulses and the addition result of the second and fourth compression pulses when the first and second basic unit compression pulses are complementary are the same as in the above embodiment, and Effect can be achieved.

Although the present invention has been described with respect to an ultrasonic defect device, other functions such as an ultrasonic diagnostic device can be performed.

In addition, although the situation where the test body S is in contact with the ultrasonic probe 6 has been described, the test body may not be in contact with the ultrasonic probe. Instead, the ultrasonic transmission and reception between the ultrasonic probe and the test body may be performed through a bonding medium such as water.

The present invention can also be applied to an ultrasonic transmission / reception system using a plurality of probe elements forming an ultrasonic probe array, and a transmission / reception system using another wave, for example, electromagnetic waves.

As mentioned above, although the invention made by this inventor was demonstrated concretely according to the said Example, this invention is not limited to the said Example, Of course, various changes are possible in the range which does not deviate from the summary.

Claims (36)

The first and second basic unit signals ga (t) and gb (t) are generated according to the first and second {a} and {b}, respectively, and the signals ga (t) and the third sequence { p}, the signal ga (t) and the fourth sequence {q}, the signal gb (t) and the sequence {p} and the signal gb (t) and the sequence {q}, respectively, and arranged in sequence Generating means for generating a composite transmission signal S consisting of the transmission signals Sap (t), Saq (t), Sbp (t), and Sbq (t) of FIGS. Transmission means for transmitting S to a target; first to fourth echo signals Rap (t) and Raq corresponding to the respective transmission signals Sap (t), Saq (t), Sbp (t), and Sbq (t) receiving means for receiving an echo reflected from the target to provide a synthesized echo signal R consisting of (t), Rbp (t) and Rbq (t); first and second correlation results Caap (t) and Caaq (t ) By using the first reference signal Ua (t) according to the sequence {a}. A second according to the sequence {b} to correlate the echo signal Rap (t) and Raq (t) provided by the stage and to provide third and fourth correlation results Cbbp (t) and Cbbq (t) First correlation means for correlating the echo signal Rap (t) and Rbq (t) provided by the receiving means using the reference signal Ub (t) of the first and second compression pulses Caapp (t) And the resultant Caap (t) and Cbbp (t) provided by the first correlation means using the third reference signal Up (t) according to the sequence {p} to provide Caapp (t). Provided by the first correlation means using the fourth reference signal Uq (t) according to the sequence {q} to process and provide third and fourth compression pulses Caaqq (t) and Caaqq (t). The compression pulses Caapp (t) and Caaqq (t) provided by the second correlation means to provide a second correlation means and a synthetic compression pulse C for correlating the Caaq (t) and Cbbq (t). , Cbbpp (t) and Cb and adding means for adding bqq (t) to increase the main lobe level of the synthetic compression pulse C, and to reduce the side lobe level thereof sufficiently. The method of claim 1, wherein the first and second sequences {a} and {b} are complementary relations having the same number of elements of the first and second types, and the third and fourth sequences {p}. } And {q} are inspection apparatuses having the same number of elements of the first and second types and having a complementary relationship. The method of claim 2, wherein the generating means comprises: the first and second basic unit signals ga (t) and gb (t) having amplitudes encoded in the order {a} and {b}, respectively, And means for amplitude encoding the waveform signal in accordance with the elements of the first and second sequences {a} and {b}. 4. The waveform of claim 3, wherein the waveform signal has a unit square wave signal, and the first and second basic unit signals ga (t) and gb (t) are the first and second sequences (a) and (b). An inverted unit square wave obtained by multiplying the square wave signal by -1 by the square wave signal assigned to the element of the first kind and the second kind of sequence {a} and {b} Inspection device including a signal. The method of claim 2, wherein the generating means comprises: the first and second basic unit signals ga (t) and gb (t) each having a phase coded waveform in the order {a} and {b}, And means for phase encoding a waveform signal in accordance with the elements of the first and second sequences {a} and {b}. The method of claim 5, wherein the waveform signal has a unit wave signal, and the first and second basic unit signals ga (t) and gb (t) are the first and second sequences {a} and {b. The inverted unit wave signal assigned to the element of the first kind and the second kind of element of the sequence {a} and {b} and inverted obtained by multiplying the unit wave signal by -1. Inspection device including a unit wave signal. The apparatus of claim 6, wherein the unit wave signal is a unit square wave signal. The inspection apparatus of claim 6, wherein the unit wave signal is an oscillation wave signal. 3. The apparatus of claim 2, wherein the first and second transmission signals Sap (t) and Saq (t) are assigned to the first kind of elements of the third and fourth sequences {p} and {q}. The first basic unit signal ga (t) and the inversed first obtained by multiplying the signal ga (t) by −1 and assigning to the element of the second kind of sequential {p} and {q} A basic unit signal -ga (t), respectively, wherein the third and fourth transmission signals Sbp (t) and Sbq (t) are added to the element of the first kind in the sequence {p} and {q}. An inverted 2's assigned to the second basic unit signal gb (t) assigned and the second kind of elements of the sequence {p} and {q} and obtained by multiplying the signal gb (t) by -1. Inspection device each containing a basic unit signal -gb (t). The method of claim 1, wherein the first and second reference signals Ua (t) and Ub (t) are the same as or similar to the waveforms of the first and second basic unit signals ga (t) and gb (t). Inspection device each having a waveform. The method of claim 1, wherein the first and second reference signals Ua (t) and Ub (t) are transmitted by the transmitting means by the first and second basic unit signals ga (t) and gb (t). And an inspection apparatus each having the same or similar waveform as the waveform of the echo signal obtained by the reflection from the target to the receiving means when constructed. The signal of claim 1, wherein the third and fourth reference signals Up (t) and Uq (t) are obtained by amplitude-encoding a waveform signal in the third and fourth sequences {p} and {q}. Inspection apparatus having a waveform identical or similar to a waveform, respectively. A basic unit signal ga (t) is generated according to the first sequence {a}, and the signal ga (t) and the second sequence {p} and the signal ga (t) and the third sequence {q} are generated. Generating means for generating a composite transmission signal S consisting of first and second transmission signals Sap (t) and Saq (t), which are sequentially and sequentially arranged, and transmitting the composite transmission signal S generated by the generation means to a target; From the target to provide a synthesized echo signal R consisting of the first and second echo signals Rap (t) and Raq (t) corresponding to the transmitting means and the respective transmitted signals Sap (t) and Saq (t). Receiving means for receiving the reflected echo, using the first reference signal Ua (t) according to the sequence {a} to provide first and second correlation result Caap (t) and Caaq (t) A first correlation means for correlating the echo signal Rap (t) and Raq (t) provided by the means, and the first and second compression pulses Caapp (t) and Caaqq (t), respectively; The resultant Caap (t) and Caaq (t) prepared by the first correlation means using the second and third reference signals Up (t) and Uq (t) according to the order {p} and {q}. The main lobe of the synthetic compression pulse C by adding the compression pulses Caapp (t) and Caaqq (t) provided by the second correlation means to provide a second correlation means correlating And an adding means, in which the level becomes large and the side lobe level thereof becomes sufficiently small. 14. The method of claim 13, wherein the first sequence {a} is a Barker sequence with elements of the first and second types, and the second and third sequences {p} and {q} are the first and second sequences. An inspection apparatus having complementary relations having the same number of elements of a second kind. 15. The test according to claim 14, wherein the generating means includes means for amplitude encoding the waveform signal according to the element of the sequence {a} so that the signal ga (t) has a waveform encoded in the sequence {a}. Device. The waveform of claim 15, wherein the waveform signal has a unit square wave signal, and the basic unit signal ga (t) is the square wave signal and the sequence assigned to the element of the first kind in the first sequence {a}. and an inverted unit square wave signal assigned to the element of the second kind of {a} and obtained by multiplying the square wave signal by -1. 16. The apparatus of claim 15, wherein the generating means phase-codes a waveform signal according to the element of the first sequence {a} such that the basic unit signal ga (t) has a waveform that is phase coded in the sequence {a}. An inspection apparatus comprising means. 18. The method of claim 17, wherein the waveform signal has a unit wave signal, and the basic unit signal ga (t) is the unit wave signal assigned to the element of the first kind in the first sequence {a} and the And an inverted unit wave signal assigned to the elements of the second kind in sequence {a} and obtained by multiplying the unit wave signal by -1. 19. The test apparatus of claim 18, wherein the unit and the signal are unit square wave signals. The inspection apparatus according to claim 18, wherein the unit wave signal is an oscillation wave signal. 15. The system of claim 14, wherein the first and second transmission signals Sap (t) and Saq (t) are elements of the second kind of the second and third sequences {p} and {q}. An inverted first basic signal assigned to the first basic unit signal ga (t) and the second kind of elements of the {p} and {q} and multiplying the signal ga (t) by −1 An inspection apparatus each comprising a unit signal -ga (t). The inspection apparatus of claim 13, wherein the first reference signal Ua (t) has a waveform identical or similar to a waveform of the basic unit signal ga (t). The waveform of the echo signal obtained by the reflection from the target to the receiving means when the transmitting means is driven by the basic unit signal ga (t). Inspection apparatus having the same or similar waveforms to. The signal of claim 13, wherein the second and third reference signals Up (t) and Ug (t) are obtained by amplitude-encoding a waveform signal in the second and third sequences {p} and {q}. An inspection device each having a waveform similar to the waveform. Generating means for generating a basic unit signal ga (t) according to the first sequence {a} and generating a transmission signal Sap (t) according to the signal ga (t) and the second sequence {p}, the generation Transmitting means for transmitting the signal Sap (t) generated by the means to a target, receiving means for receiving the echo reflected from the target to provide an echo signal Rap (t) corresponding to the signal Sap (t), a correlation result Second correlation means for compressing the echo signal Rap (t) provided by the receiving means using the first reference signal Ua (t) according to the sequence {a} to provide Caap (t) and compression A second correlation for correlating the resultant Caap (t) provided by the first correlation means using a second reference signal Up (t) according to the sequence {p} to provide a pulse Caapp (t) An inspection apparatus comprising means. 27. The method of claim 25, wherein the first sequence {a} is a Barker sequence having elements of a first and a second kind, and the second sequence {p} represents an element of a first and a second kind. And having a large autocorrelation function ρpp (i) at i = 0 compared to other places (i ≠ 0). 27. The apparatus of claim 26, wherein the generating means includes means for amplitude encoding the waveform signal in accordance with the element of the sequence {a} even if the signal ga (t) has a waveform encoded in the sequence {a}. Device. 28. The waveform of claim 27, wherein the waveform signal has a unit square wave signal, and the basic unit signal ga (t) is the square wave signal and the sequence assigned to the element of the first kind in the first sequence {a}. and an inverted unit square wave signal assigned to the element of the second kind of {a} and obtained by multiplying the square wave signal by -1. 28. The apparatus of claim 27, wherein the generating means phase-encodes a waveform signal according to the element of the first sequence {a} such that the basic unit signal ga (t) has a waveform that is phase coded in the sequence {a}. An inspection apparatus comprising means. The unit wave signal according to claim 29, wherein the waveform signal has a unit wave signal, and the basic unit signal ga (t) is the unit wave signal assigned to the element of the first kind in the first sequence {a} and the And an inverted unit wave signal assigned to elements of the second kind in the sequence {a} and obtained by multiplying the unit wave signal by -1. 31. The apparatus of claim 30, wherein the unit wave signal is a unit square wave signal. The inspection apparatus according to claim 30, wherein the unit wave signal is an oscillation wave signal. 27. The apparatus of claim 26, wherein the transmission signal Sap (t) is the first unit signal ga (t) and the order {p} assigned to the element of the first kind of the second sequence {p}. And an inverted basic unit signal -ga (t), assigned to elements of the two types, obtained by multiplying the signal ga (t) by -1. 26. The inspection apparatus of claim 25, wherein the first reference signal Ua (t) has the same or similar waveform as that of the basic unit signal ga (t). The waveform of the echo signal obtained by the reflection from the target to the receiving means when the transmitting means is driven by the basic unit signal ga (t). Inspection apparatus having the same or similar waveforms to. The inspection apparatus according to claim 25, wherein the second reference signal Up (t) has a waveform identical or similar to a waveform of a signal obtained by amplitude-encoding a waveform signal in the second sequence {p}.