JPH0943209A - Ultrasonic measuring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable an ultrasonic measurement in a wide frequency range and to prevent adverse influence due to the saturation of an amplifier in a high frequency. SOLUTION: A transmission signal is taken from a burst wave generated by an oscillation means 2 and it is applied to an ultrasonic wave transmission/ reception means 4, 5 through a switch 10. The reflection wave from a specimen 6 is converted to a reception signal by the ultrasonic wave transmission/ reception means 4, 5 to be inputted to a side of a reception circuit through the switch 10. A timing of switching of transmission/reception by a switch 11 is set to one whereby the reflection in a lens is removed. Filter switching means 11, 12 switch passages such that the reception signal is inputted to detection means 15-17 by being passed through a high pass filter 13 when it is a high frequency and it is inputted to the detection means 15-17 by being not passed therethrough when it is a low frequency. Outputs of the detection means 15-17 are stored in a memory to be used for forming of an ultrasonic image and measuring of an elastic characteristic.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic measuring device for measuring elastic properties of a minute portion of a sample by using ultrasonic waves.

[0002]

2. Description of the Related Art An apparatus for converging an ultrasonic wave to enter a sample, receiving a reflected wave from the sample, and creating an ultrasonic image based on the intensity of the reflected wave, or a convergence point of the ultrasonic wave is Z.
V obtained from the reflected waves of the sample at a plurality of positions displaced in the direction
An ultrasonic microscope is known as an apparatus for measuring the elastic properties of a minute portion of a sample using a (Z) curve. This type of ultrasonic microscope measures only the intensity of the reflected wave from the sample. On the other hand, an ultrasonic measuring device for detecting the intensity and phase of the reflected wave has been developed in order to obtain more information about the elastic properties of the sample. For example, Japanese Patent Laid-Open No. 5-
No. 26854 describes an ultrasonic measuring device that detects the intensity and phase of a reflected wave of a sample and analyzes the elastic properties of the sample.

FIG. 3 is a block diagram of an ultrasonic measuring device configured to detect a phase. The reference signal oscillator 101 always outputs a continuous wave having a constant frequency. Computer 10
2 inputs a transmission trigger to the control unit 103, and the control unit 10
3 outputs an on / off signal corresponding to the time width of several tens of cycles of the frequency of the reference signal oscillator 101 to the analog switch 104 in synchronization with the transmission trigger. Analog switch 1
04 is switched according to ON / OFF of the on / off signal. When ON / OFF signal is ON, analog switch 104
Is connected to the terminal a side, and the signal generated by the reference signal oscillator 101 is output to the circulator 105 to generate a transmission burst signal. This transmission burst signal passes through the circulator 105 and is applied to the transducer 106. The transmission burst wave is electroacoustic converted by the transducer 106 and converted into ultrasonic waves. This ultrasonic wave is generated by the acoustic lens 1.
07 and is incident on the sample 109 placed on the sample stage 108. A space between the acoustic lens 107 and the sample 109 is filled with a coupler liquid 110 for the propagation of ultrasonic waves. The ultrasonic wave incident on the sample 109 is reflected by the sample 109, propagates again through the coupler liquid 110 and the acoustic lens 107, and is converted into an electric signal by the transducer 106. Hereinafter, this signal is referred to as a received signal.

The received signal passes through the circulator 105 and is amplified by the preamplifier 111 to generate two multiplication units 112a and 112a.
12b is input. The multiplication unit 112a multiplies the continuous wave output from the reference signal oscillator 101 and the received signal and outputs an in-phase component. In the multiplication unit 112b, the continuous wave output from the reference signal oscillator 101
° Multiply the phase-shifted signal and the received signal and output the quadrature phase component.

Now, assume that the signal output from the reference signal oscillator 101 is sin (ωt). Here, ω is frequency and t is time. Since the phase of the received signal is delayed with respect to the transmission due to the elastic properties of the sample, the time required for propagating in the acoustic lens and the coupler liquid, and the like, if this phase delay is φ, it can be written as Bsin (ωt−φ). B is the strength of the received signal.

Therefore, the in-phase output u ₁ of the multiplication unit 112a and the quadrature phase output u ₂ of the multiplication unit 112b are as follows. u ₁ (t) = B / 2 {cosφ− cosφcos (2ωt) − cosφsin (2ωt)} (1) u ₂ (t) = B / 2 {sinφ + sinφcos (2ωt) − cosφsin (2ωt)} (2) φ Since u is a constant and sin φ and cos φ are also constants, u ₁ and u ₂ have a DC component and a frequency of 2ω,
Except for the 2ω component, sin, co of the phase delay φ of the received signal
s can be taken out.

The 2ω component of the in-phase output of the multiplication unit 112a and the quadrature phase output of the multiplication unit 112b are removed by the low-pass filters 114a and 114b, respectively, and only the DC components corresponding to sin φ and cos φ remain.

The A / D converters 115a and 115b A / D-convert the detection outputs of the in-phase and quadrature phases, respectively, and convert the phase detection output of the sample reflection into a digital signal, which is stored in the memory of the computer 102. To do. The computer 102 stores the sample reflection si
The phase and the reflection intensity are calculated from the nφ and cosφ components. Z
The scanning unit 116 changes the distance between the acoustic lens and the sample according to a command from the computer 102, and adjusts focusing and the like.

[0009]

The conventional ultrasonic measuring device as described above has the following drawbacks. When performing the above-mentioned phase detection, it is not necessary to provide a gate circuit for cutting out a necessary signal component, but the absorption of ultrasonic waves in the coupler liquid increases with the exponential function of the square of the frequency as the used frequency increases. . Therefore, the focal length becomes shorter as the acoustic lens is used at a higher frequency. Not all the ultrasonic waves generated by the transducer propagate in the liquid coupler, and a part of the ultrasonic waves is reflected by the lens surface of the acoustic lens. When the focal length is shortened, the reflected signal from the sample becomes very close to the reflected signal from the lens surface of the acoustic lens. On the other hand, the reflected wave from the sample becomes smaller than the internal reflection of the acoustic lens at a high frequency due to absorption in the coupler liquid, reflection on the sample surface, and the like. Therefore, if the amplification factor of the amplifier is set according to the sample reflection signal, the amplifier is saturated due to the internal reflection of the acoustic lens which is larger than the sample reflection signal.
Normal operation will stop in the time range of about 00 nsec. For this reason, there occurs a problem that the sample reflection signal is not amplified.

Although it is possible to apply a gate to the internal reflection signal to remove the internal reflection signal, there is a possibility that the amplifier will be saturated by noise generated when the gate circuit is turned on and off. In order to avoid saturation, focusing on the fact that the gate noise frequency is 300 to 500 MHz, it is conceivable to provide a high-pass filter with a cutoff frequency of about 500 MHz in the latter stage of the gate circuit. Measurement becomes impossible.

The present invention has been made in view of the above points, and an amplifier for amplifying a received signal saturates due to an internal reflection component of an acoustic lens and gate noise over a wide band from a low frequency to a high frequency. It is an object of the present invention to provide an ultrasonic measurement device that can obtain information on sample reflection without the need.

[0012]

In order to achieve the above object, the present invention takes the following measures. According to the present invention, which corresponds to claim 1, a burst wave oscillating means for generating a burst wave, and an ultrasonic wave which converges the burst wave signal into a minute spot to be incident on a sample and receive a reflected wave from the sample. Ultrasonic transmission / reception means for wave-converting into an electric reception signal, a transmission state in which the ultrasonic transmission / reception means can apply the transmission signal to the ultrasonic transmission / reception means, and the reception signal is extracted from the ultrasonic transmission / reception means Transmission / reception switching means for switching to a possible reception state, setting means for setting transmission / reception switching timing by the transmission / reception switching means, high-pass filter for removing low frequency components from the reception signal, and detection means for detecting the reception signal , The path of the received signal extracted from the ultrasonic wave transmitting / receiving means to the detecting means is passed through the high pass filter before Comprising a filter switching means for switching to a second path to be input to the detecting means without passing through the first path to be input to the detection means the high-pass filter and a memory for storing the detection information of the received signal.

According to the present invention, when the frequency used is low, a burst wave is made incident on the sample and the reflected signal is input to the detection means as it is for phase detection or peak detection to obtain complex information or intensity information of the sample reflected signal. Save to memory. On the other hand, when the used frequency is high, the sample reflection signal can be filtered through a high pass filter to remove the gate noise and then input to the detection means to obtain the detection information. Therefore, it is possible to measure ultrasonic waves at a wide frequency with a common receiving circuit, and it is possible to eliminate the adverse effect of saturation of the amplifier at high frequencies.

According to a second aspect of the present invention, in the ultrasonic measuring apparatus having the above-mentioned configuration, the setting means is slower than the internal reflection signal of the ultrasonic transmission / reception means to the transmission / reception switching means, and is a sample. The transmission / reception switching timing for switching to the reception state at a timing earlier than the reflection signal of is set.

According to the present invention, since the transmission / reception switching means switches to the reception state at a timing later than the internal reflection signal of the ultrasonic transmission / reception means and earlier than the reflection signal of the sample, the internal reflection signal is removed from the reception signal. can do. Further, the gate noise caused by the transmission / reception switching means can be removed by passing it through a high pass filter.

According to a third aspect of the present invention, in the ultrasonic measuring apparatus having the above-mentioned configuration, the transmission / reception switching timing for switching from the setting means to the transmission / reception switching means to a reception state only in the vicinity of the reflection signal of the sample is set. Set.

According to the present invention, since the transmission / reception switching means switches to the reception state only in the vicinity of the reflection signal of the sample,
Only the sample reflection signal from which the internal reflection signal has been removed can be taken out, and the gate noise due to the transmission / reception switching means can be removed by passing it through a high pass filter.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. FIG. 1 is a diagram showing a configuration of an ultrasonic measurement device according to an embodiment of the present invention. In the ultrasonic measurement apparatus of this embodiment, the oscillator 2 generates a continuous wave having a frequency designated by the computer 1, and the semiconductor switch 3 cuts off a part of the signal sent from the oscillator 2.

A transducer 4 for performing electroacoustic conversion is attached to one end surface of an acoustic lens 5. The concave curved surface formed on the other end surface of the acoustic lens 5 converges the ultrasonic wave into a minute spot. A sample 6 is placed in a water tank 8 on a sample table 7 near the focal point of the acoustic lens 5.
The water tank 8 is filled with a coupler liquid 9 for propagating ultrasonic waves.

The transducer 4 has a semiconductor switch 1
0 is connected. The semiconductor switch 10 can switch the input / output of the transducer 4 between the oscillation unit 2 side and the first filter changeover switch 11 side. First
The filter changeover switch 11 can switch the signal from the transducer 4 between the second filter changeover switch 12 side and the high pass filter 13 side. The second filter changeover switch 12 is the amplifier 1
The terminal connected to the fourth input terminal is switched between the first filter changeover switch 11 and the high-pass filter 13.

The output stage of the amplifier 14 has two multiplication units 1
5a and 15b are connected. The continuous wave output from the oscillation unit 2 is input as the first reference signal to one multiplication unit 15a, and the first reference signal is input to the other multiplication unit 15b, for example, 90 °.
9 through the 90 ° phase shifter 16 composed of a hybrid
It is input as the second reference signal with a 0 ° phase delay.
Low-pass filters 17a and 17b are connected to the output stages of the multipliers 15a and 15b, respectively. The low pass filters 17a and 17b function to remove high frequency components. The characteristics of the low-pass filters 17a and 17b are set so that at least a frequency that is twice the frequency of the continuous wave output by the oscillator 2 can be removed during measurement.

The signals passed through the low pass filters 17a and 17b are A / D converted by the A / D converters 18a and 18b. The converted outputs of the A / D converters 18a and 18b are input to the computer 1. The computer 1 is connected to a pulse control unit 19 that controls the overall timing, a Z scanning unit 20 that changes the distance between the sample 6 and the acoustic lens 4, and a Z distance measuring unit 21 that measures the moving distance.

Next, the operation of the present embodiment will be described.
FIG. 2 is a time chart of this embodiment. First, the frequency to be measured is input to the computer 1. The computer 1 controls the switching timing of the first and second changeover switches 11 and 12 according to the set frequency. For example, if the frequency component of the switching noise generated by the semiconductor switch 10 is about 500 MHz, the cutoff frequency of the high-pass filter 13 is also set to about 500 MHz, so if the oscillation frequency is 600 MHz or less, the high-pass filter 13 will not enter. Switch to
When the frequency is higher than 600 MHz, the path is switched so that the path passes through the high pass filter 13.

As shown in FIG. 2A, the oscillator 2 constantly outputs a continuous wave having a constant frequency set by the computer 1. When a transmission trigger is input to the pulse control unit 19 from the computer 1 (FIG. 2 (b)), the pulse control unit 19 synchronizes with the transmission trigger and the frequency of the oscillator 2 as shown in FIG. An on / off signal having a time width corresponding to a cycle is given to the semiconductor switch 3. Further, the pulse control unit 19 synchronizes with the transmission trigger so that the frequency of the oscillation unit 2 is 600 MHz.
When the frequency is equal to or lower than z (low frequency), the switching signal shown in FIG. 2D is turned on several tens nsec earlier than the on / off signal (c) and turned off several tens nsec later.
0, and the oscillation frequency of the oscillator 2 is 600 MHz.
At above (high frequency) several tens ns from the on / off signal (c)
A signal (FIG. 2E) that turns on faster and turns off later than the internal reflection of the first lens is output to the semiconductor switch 10.

The semiconductor switch 3 to which the ON / OFF signal shown in FIG. 2C is applied is switched in response to ON / OFF of the ON / OFF signal, and when ON, the signal generated by the oscillator 2 is output to the semiconductor switch 10. . In this way, the transmission burst signal shown in FIG. 2 (f) is produced.

On the other hand, the semiconductor switch 10 is shown in FIG.
Alternatively, when the switching signal shown in FIG. 2E is on, it is switched to the semiconductor switch 3 side, and when it is off, it is switched to the first filter switching switch 11 side. Semiconductor switch 1
When 0 is switched to the semiconductor switch 3 side, the transmission burst signal is applied to the transducer 4 through the semiconductor switch 10.

The transmitted burst wave is electroacoustic converted by the transducer 4 and converted into ultrasonic waves. This ultrasonic wave propagates through the acoustic lens 5, is converged, passes through the coupler liquid 9, and enters the sample 6. The ultrasonic wave incident on the sample 6 is reflected by the sample 6, propagates through the coupler liquid 9 and the acoustic lens 5 again, and is converted into a reception signal by the transducer 4.

Here, as shown in FIG. 2 (g), the received signal includes transmission leakage, lens first reflection, lens second reflection, etc. in addition to sample reflection. When the frequency is low, the received signal is the same as the first and second filter changeover switches 1
It is amplified by the amplifier 14 through 1 and 12. Even in this case, the output of the amplifier 14 may be saturated due to the internal reflection of the acoustic lens 5. For example, since the focal length of the acoustic lens used at a frequency near 400 MHz is about 600 μm, the timing difference from the internal reflection is 800 nsec. Therefore, even if the acoustic lens 5 and the sample 6 are brought close to each other and collide with each other, a lens having an opening half-angle of 60 ° has a timing difference of 300 nsec or more from internal reflection and is not affected by saturation.

On the other hand, at high frequency, the semiconductor switch 10
2 (d), the received signal is a signal delayed from the timing of the sample reflection signal and the on / off signal of the semiconductor switch 10 from the semiconductor switch 10 as shown in FIG. 2 (h). Changeover switch 1
It is output to 1. First filter changeover switch 11
On-off noise of the semiconductor switch 11 is removed by the high-pass filter 13 from the passed signal, and the signal passes through the second filter changeover switch 12 and is amplified by the amplifier 14. Since the transmission leakage and the signal having a timing earlier than the sample reflection are removed from the amplified signal, it becomes as shown in FIG. 2 (i).

The received signal amplified by the amplifier 14 is input to the multiplication units 15a and 15b. The multiplier 15a multiplies the received signal by the continuous wave output from the oscillator 2 as a reference signal and outputs the result. On the other hand, the signal output from the oscillator 2 is converted into a signal whose phase is delayed by 90 ° in the phase shift unit 16, and is multiplied by the reception signal in the multiplication unit 15b as the second reference signal, and the result is output. The low-pass filters 17a and 17b remove the double frequency components of the oscillating unit 2 from the multiplied signals, and a rectangular wave having a magnitude corresponding to cosφ and sinφ remains as in the conventional example.

The outputs of the low-pass filters 17a and 17b thus phase-detected are A / D converters 17a and 1b.
7b. In order to extract the sample reflection from the large number of signals in the A / D conversion units 18a and 18b, the pulse control unit 19 uses an A / D conversion trigger whose timing is delayed by Td with respect to the transmission trigger as shown in FIG. Make a signal. The A / D conversion trigger signal is given to the A / D conversion units 18a and 18b to perform A / D conversion on the respective detection outputs, and the phase detection output of the sample reflection is converted into a digital signal for computer 1
In the internal memory. The time delay amount Td of the trigger signal for transmission and A / D conversion can be set from the computer 1 to the pulse control unit 19.

The Z scanning section 20 changes the distance between the acoustic lens 5 and the sample 6 in response to a command from the computer 1 to adjust focusing and the like. When performing V (z) measurement, the A / D conversion timing Td is first adjusted to the sample reflection position while looking at the oscilloscope or the like. The Z scanning unit 20 changes the distance between the acoustic lens 5 and the sample 6, and the above process is repeated while measuring the amount of movement by the Z distance measuring unit 21. The complex information cos φ and sin φ of the sample reflection are moved by Z. It is taken into the computer 1 together with. The A / D conversion timing changes depending on the distance between the acoustic lens 5 and the sample 6. Assuming that the amount of Z movement from the measurement start position is Δz, the timing shift is ΔTd, and the sound velocity of the coupler liquid is v, the timing of A / D conversion is calculated by the computer 1 from the following equation and the timing is changed.

ΔTd = 2Δz / v (3) As described above, according to this embodiment, the on / off timing of the input from the acoustic lens 5 to the receiving unit is changed according to the frequency of the oscillating unit 2 to change the acoustic lens 5. Since the internal reflection component of is removed and the high-pass filter 13 is passed only at the high frequency, the complex information of the reflection from the sample 6 is not affected by the saturation due to the internal reflection of the amplifier 14 from the low frequency to the high frequency. Can be measured.

In this embodiment, only phase detection is described, but the present invention is not limited to this, and the same can be applied to the case of peak detection. It is also conceivable that the transmission / reception switching signal of the acoustic lens is turned off only near the sample reflection, and the switch is switched so as to pass through the high-pass filter only at high frequencies.

Further, when the timing of sample reflection changes as in the measurement of V (z), the high-pass filter may be passed only when the reflection signal from the sample approaches the internal reflection signal.

The intensity and phase of the two-dimensional reflected wave can be measured by repeating the measurement while the two-dimensional scanning is performed by using the XY scanning unit. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention.

[0037]

As described above in detail, according to the present invention, the internal reflection of the lens is removed by switching the transmission / reception, and the gate noise signal generated by the internal reflection removal is removed when the ultrasonic measurement is performed with the high frequency signal. Therefore, it is possible to prevent the ultrasonic wave from being passed at the time of low frequency measurement, and it is possible to measure ultrasonic waves at a wide frequency with a common receiving circuit, and it is possible to eliminate the adverse effect of the saturation of the amplifier at high frequency.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an ultrasonic measurement device according to an embodiment of the present invention.

FIG. 2 is a time chart of the ultrasonic measurement device shown in FIG.

FIG. 3 is a configuration diagram of a conventional ultrasonic measurement device.

[Explanation of symbols]

1 ... Computer, 2 ... Oscillation part, 3, 10 ... Semiconductor switch, 4 ... Transducer, 5 ... Acoustic lens, 11 ...
First filter changeover switch, 12 ... Second filter changeover switch, 13 ... High-pass filter, 14
... amplifier, 15a, 15b ... multiplication section, 17a, 17b ...
Low-pass filter, 19 ... Pulse control unit, 20 ... Z scanning unit, 21 ... Z distance measuring unit.

Claims (3)

[Claims] 1. A burst wave oscillating means for generating a burst wave; and a burst wave signal which is converted into an ultrasonic wave which converges into a minute spot to enter a sample and which receives a reflected wave from the sample and electrically An ultrasonic wave transmitting / receiving means for converting the ultrasonic wave transmitting / receiving means into a transmission state in which the transmission signal can be applied to the ultrasonic wave transmitting / receiving means, and a reception state in which the reception signal can be taken out from the ultrasonic wave transmitting / receiving means. Transmission / reception switching means for switching to, transmission / reception switching means for setting transmission / reception switching timing, a high-pass filter for removing low-frequency components from the reception signal, detection means for detecting the reception signal, and ultrasonic transmission / reception The reception signal extracted from the means is passed through the high-pass filter to the detection means after passing through the path to the detection means. A filter switching means for switching between a first path for input and a second path for inputting to the detection means without passing through the high-pass filter, and a memory for storing detection information of the received signal. Sound wave measuring device. 2. A transmission / reception switching timing for switching from the setting means to the transmission / reception switching means so as to switch to the reception state at a timing later than the internal reflection signal of the ultrasonic transmission / reception means and earlier than the reflection signal of the sample. The ultrasonic measuring device according to claim 1, wherein 3. The ultrasonic measurement apparatus according to claim 1, wherein the setting means sets the transmission / reception switching timing for switching to the reception state only in the vicinity of the reflection signal of the sample, to the transmission / reception switching means.