JP2021032767A - Ultrasonic measuring method and ultrasonic measuring device - Google Patents

Abstract

To provide an ultrasonic measuring method and an ultrasonic measuring device that can reduce cost related to ultrasonic measurement and reduce processing time.SOLUTION: An ultrasonic measuring method is for an ultrasonic measuring device comprising: an ultrasonic transmitting unit that transmits an ultrasonic wave to an object; an ultrasonic receiving unit that receives the ultrasonic wave reflected on the object and outputs a received signal in a signal waveform including a plurality of peaks; and a variable gain amplifier that amplifies the received signal. The ultrasonic measuring method executes a gain setting step of setting the gain of the variable gain amplifier, and a zero-cross detection step of detecting a zero-cross point of the received signal output from the variable gain amplifier, and the gain setting step sets the gain of the variable gain amplifier so that a predetermined number-th peak included in the signal waveform of the received signal output from the variable gain amplifier becomes equal to or more than a threshold voltage.SELECTED DRAWING: Figure 1

Description

The present invention relates to an ultrasonic measuring method and an ultrasonic measuring device.

Conventionally, an ultrasonic measuring device has been known in which ultrasonic wave transmission / reception processing is performed toward an object and the distance to the object is measured based on the time from the ultrasonic wave transmission timing to the ultrasonic wave reception timing. (See, for example, Patent Document 1).

In such an ultrasonic measuring device, the reception timing is specified based on the zero crossing point of the received signal exceeding the threshold value in the waveform data of the received signal when the ultrasonic wave is received. However, as the distance from the ultrasonic measuring device to the object increases, the sound pressure of the ultrasonic waves received by the ultrasonic receiving unit decreases, so that the number and position of received signals exceeding the threshold value also fluctuate. In this case, the zero cross point set as the ultrasonic wave reception timing may fluctuate for each measurement, and an offset error occurs. For example, in the first measurement, the zero cross point of the first output received signal is set as the reception timing, and in the second measurement, the zero cross point of the second output received signal is set as the reception timing. Then, the deviation of the received signal for one wave becomes an offset error, and the measurement accuracy is lowered.

Therefore, in the ultrasonic measuring apparatus described in Patent Document 1, ultrasonic processing is performed a plurality of times, and waveform data corresponding to each time is obtained. Next, a temporary reference zero cross point is set for the waveform data of the first ultrasonic processing, and the reference zero cross point of the waveform data of the i-th ultrasonic processing is set as the reference zero cross point of the i-1th waveform data. Set based on. After that, the amplitude in the j-th (j = 0, 1, 2, ... J) wave of each time is obtained, and the average amplitude _Sj is calculated. Then, the reception timing is set to the zero cross point two waves after the zero cross point of the wave in which the amplitude ratio R _{j of the jth} average amplitude S j and the j + 1th average amplitude S _{j + 1 is maximum, and the target is set from the ultrasonic measuring device.} Calculate the distance to the object.

Japanese Unexamined Patent Publication No. 5-34192

However, in the ultrasonic measurement method using the ultrasonic measuring device described in Patent Document 1, in order to measure the distance to the object once, the ultrasonic treatment is performed a plurality of times, and the ultrasonic treatment is performed a plurality of times. It is necessary to store each of the obtained waveform data in the storage unit. Therefore, there is a problem that a large-capacity storage area is required as a storage unit, the cost of the ultrasonic measuring device is high, and the processing time is long.

In the ultrasonic measurement method according to the first application example, an ultrasonic transmission unit that transmits ultrasonic waves to an object and a received signal having a signal waveform including a plurality of peaks by receiving the ultrasonic waves reflected by the object are used. It is an ultrasonic measurement method of an ultrasonic measuring device including an ultrasonic receiving unit for outputting and a variable gain amplifier for amplifying the received signal, and a gain setting step for setting the gain of the variable gain amplifier is performed. In the gain setting step, a predetermined peak included in the signal waveform of the received signal output from the variable gain amplifier is equal to or higher than the threshold voltage, or is obtained from a peak having the threshold voltage or higher. The gain of the variable gain amplifier is set so that the time width of the line becomes a predetermined time width.

In the ultrasonic measurement method of the first application example, the gain setting step detects the maximum signal voltage among the plurality of signal voltages of the peaks included in the received signal, and the maximum signal voltage is a predetermined reference voltage. If it is different from the above, the gain may be set to be (reference voltage / maximum signal voltage) times the reference gain.

In the ultrasonic measurement method of the first application example, the gain setting step forms the envelope, detects the time width of the period during which the signal voltage of the envelope becomes equal to or higher than the threshold voltage, and the time width and the said. The gain may be set with respect to the detected time width based on the first calibration curve data showing the relationship with the gain.

In the ultrasonic measurement method of the first application example, the gain setting step measures the number of the peaks having the threshold voltage or more included in the received signal, and the number of the peaks having the threshold voltage or more and the gain. It was measured based on the relationship or the second calibration line data showing the relationship between the gain and the time width of the period during which the plurality of received signals obtained from the number of peaks continuously exceed the threshold voltage. The gain may be set for the number of peaks.

The ultrasonic measuring device according to the second application example has an ultrasonic transmitting unit that transmits ultrasonic waves to an object and a received signal having a signal waveform including a plurality of peaks by receiving the ultrasonic waves reflected by the object. The output ultrasonic receiver, the variable gain amplifier that amplifies the received signal, and the predetermined peak included in the signal waveform of the received signal output from the variable gain amplifier are set to be equal to or higher than the threshold voltage. A control unit that sets the gain of the variable gain amplifier so that the time width of the envelope obtained from the peak above the threshold voltage becomes a predetermined time width is provided.

The ultrasonic measuring device of the second application example includes a voltage measuring unit for measuring signal voltages of a plurality of the peaks included in the received signal output from the variable gain amplifier, and the control unit is the voltage measuring unit. The maximum signal voltage among the plurality of signal voltages of the peaks measured by is detected, and when the maximum signal voltage is different from a predetermined reference voltage, it is multiplied by (reference voltage / maximum signal voltage) with respect to the reference gain. The gain may be set.

In the ultrasonic measuring device of the second application example, the envelope processing unit that forms the envelope output from the variable gain amplifier and detects the time width of the period during which the signal voltage of the envelope becomes equal to or higher than the threshold voltage. The control unit may set the gain with respect to the time width detected by the envelope processing unit based on the first calibration line data showing the relationship between the time width and the gain.

The ultrasonic measuring device of the second application example further includes a zero cross detection unit that detects a zero cross point of the received signal output from the variable gain amplifier, and the zero cross detection unit is included in the waveform of the received signal. A zero-cross detection pulse is output for the peak above the threshold voltage, and the control unit outputs the peak above the threshold voltage included in the received signal based on the zero-cross detection pulse output from the zero-cross detection unit. The relationship between the number of peaks above the threshold voltage and the gain, or the time width of the period during which the plurality of received signals obtained from the number of peaks continuously exceed the threshold voltage. The gain may be set with respect to the number of measured peaks based on the second calibration line data showing the relationship between the gain and the gain.

The schematic diagram which shows the schematic structure of the ultrasonic wave measuring apparatus which concerns on 1st Embodiment. The cross-sectional view which shows the structural example of the ultrasonic device of 1st Embodiment. The figure which shows the connection example of the ultrasonic transducer of 1st Embodiment. The flowchart which shows the ultrasonic wave measurement method of 1st Embodiment. The timing chart of the transmission pulse, the reception signal, and the zero cross detection pulse in the ultrasonic transmission / reception processing of the first embodiment. The schematic diagram which shows the schematic structure of the ultrasonic wave measuring apparatus which concerns on 2nd Embodiment. The flowchart which shows the ultrasonic wave measurement method of 2nd Embodiment. The timing chart of the transmission pulse, the reception signal, the zero cross detection pulse, the envelope, and the time width in the ultrasonic transmission / reception processing of the second embodiment. The figure which shows an example of the 1st calibration curve data in 2nd Embodiment. The schematic diagram which shows the schematic structure of the ultrasonic wave measuring apparatus which concerns on 3rd Embodiment. The flowchart which shows the ultrasonic wave measurement method of 3rd Embodiment. The timing chart of the transmission pulse, the reception signal, and the zero cross detection pulse in the ultrasonic transmission / reception processing of the third embodiment. The figure which shows an example of the 2nd calibration curve data in 3rd Embodiment.

[First Embodiment]
Hereinafter, the ultrasonic measuring apparatus of the first embodiment will be described.
FIG. 1 is a schematic view showing a schematic configuration of the ultrasonic measuring device 10 of the present embodiment.
The ultrasonic measuring device 10 includes an ultrasonic device 20 and a control circuit 30 that controls the ultrasonic device 20. The ultrasonic measuring device 10 transmits ultrasonic waves from the ultrasonic device 20 toward the object 1 under the control of the control circuit 30, and receives the ultrasonic waves reflected by the object 1 by the ultrasonic device 20. Perform transmission / reception processing. Then, the control circuit 30 is based on the time from the transmission timing of the ultrasonic wave of the ultrasonic wave transmission / reception process by the ultrasonic wave device 20 to the reception timing of the ultrasonic wave reflected by the object 1 from the ultrasonic device 20 to the object. Calculate the distance to 1.
Hereinafter, details of each configuration of such an ultrasonic measuring device 10 will be described.

[Configuration of ultrasonic device 20]
FIG. 2 is a cross-sectional view showing a configuration example of the ultrasonic device 20.
The ultrasonic device 20 transmits ultrasonic waves to the object 1, performs an ultrasonic transmission / reception process for receiving the ultrasonic waves reflected by the object 1, and outputs a reception signal by receiving the ultrasonic waves. That is, in the present embodiment, the ultrasonic device 20 functions as an ultrasonic transmitting / receiving unit and an ultrasonic receiving unit. As shown in FIG. 2, the ultrasonic device 20 includes an element substrate 21, a diaphragm 22, and a piezoelectric element 23. In the following description, the transmission / reception direction of ultrasonic waves from the ultrasonic device 20 toward the object 1 is defined as the Z direction.

The element substrate 21 is a substrate that supports the diaphragm 22, and is composed of a semiconductor substrate such as Si. The element substrate 21 is provided with a plurality of openings 211 penetrating the element substrate 21 along the Z direction.

The diaphragm 22 is composed of, for example, _{a laminated body of SiO 2} and ZrO ₂ , and is provided on the −Z side of the element substrate 21. The diaphragm 22 is supported by the element substrate 21 constituting the opening 211, and closes the −Z side of the opening 211. The portion of the diaphragm 22 that overlaps with each opening 211 when viewed from the Z direction constitutes the diaphragm 221 that transmits and receives ultrasonic waves by vibration in the diaphragm 22.

The piezoelectric element 23 is provided on the diaphragm 22 at a position where it overlaps with each vibrating portion 221 when viewed from the Z direction. As shown in FIG. 2, the piezoelectric element 23 is configured by laminating a lower electrode 231, a piezoelectric film 232, and an upper electrode 233 in this order on a diaphragm 22.

In such an ultrasonic device 20, one ultrasonic transducer 24 is configured by one vibrating unit 221 and a piezoelectric element 23 arranged on the vibrating unit 221.
Then, in this ultrasonic device 20, when a voltage is applied between the lower electrode 231 and the upper electrode 233, the piezoelectric film 232 expands and contracts, and the vibrating portion 221 oscillates according to the opening width of the opening 211 and the like. It vibrates at a frequency. As a result, ultrasonic waves are transmitted from the vibrating unit 221 toward the + Z side.
Further, in the ultrasonic device 20, when the ultrasonic wave reflected by the object 1 is input to the vibrating unit 221, the vibrating unit 221 vibrates with an amplitude corresponding to the sound pressure of the input ultrasonic wave, and the piezoelectric film 232 A potential difference is generated between the lower electrode 231 side and the upper electrode 233 side of the above. Therefore, the received signal corresponding to the potential difference is output from each piezoelectric element 23.
That is, each ultrasonic transducer 24 of the ultrasonic device 20 functions as an ultrasonic transmitting unit that transmits ultrasonic waves to the object 1, and also serves as an ultrasonic receiving unit that receives the ultrasonic waves reflected by the object 1. Also works. Here, an ultrasonic device 20 including an ultrasonic transducer 24 with integrated transmission / reception is illustrated, but a transmission ultrasonic transducer that functions as an ultrasonic transmitter and a reception ultrasonic transducer that functions as an ultrasonic receiver are illustrated. The ultrasonic transducer and the ultrasonic transducer may be provided as separate bodies.

FIG. 3 is a diagram showing a connection example of the ultrasonic transducer 24 in the ultrasonic device 20.
In this embodiment, the plurality of ultrasonic devices 20 are arranged in a matrix of n rows and m columns. The lower electrodes 231 of each ultrasonic device 20 are connected to each other by the first bypass wiring 231A, and are connected to the first terminal 251 provided in a part of the element substrate 21. Similarly, the upper electrodes 233 of each ultrasonic device 20 are connected to each other by the second bypass wiring 233A and connected to the second terminal 252 provided in a part of the element substrate 21. These first terminal 251 and second terminal 252 are each connected to the control circuit 30. In such a configuration, by applying a voltage between the first terminal 251 and the second terminal 252, all the ultrasonic transducers 24 can be driven at the same time.
The example shown in FIG. 3 is a configuration example in which the lower electrodes 231 of all the ultrasonic transducers 24 are connected and connected to the first terminal 251. However, a predetermined number of ultrasonic transducers 24 are used as one channel. , The first terminal 251 may be provided for each channel. In this case, by inputting drive signals between all the first terminals 251 and the second terminals 252 at the same time, all the ultrasonic transducers 24 can be driven at the same time as in FIG. It is also possible to drive each first terminal 251 individually. In this case, the transmission sound pressure can be adjusted by controlling the number of channels to be driven, and the transmission direction of ultrasonic waves can be controlled by delay-controlling the drive timing of each channel. Further, a plurality of channels may be used separately as a transmission channel for transmitting ultrasonic waves and a reception channel for receiving ultrasonic waves.

[Structure of control circuit 30]
Returning to FIG. 1, the control circuit 30 will be described. The control circuit 30 is a control unit that controls the ultrasonic device 20, and is connected to the first terminal 251 and the second terminal 252 of the ultrasonic device 20 as described above.
As shown in FIG. 1, the control circuit 30 includes a switching circuit 31, a signal ground 32, a transmission circuit unit 33, a reception circuit unit 34, and a microcomputer 35 (microcontroller).

The switching circuit 31 is connected to the first terminal 251 of the ultrasonic device 20, the transmission circuit unit 33, and the reception circuit unit 34. Based on the control of the microcomputer 35, the switching circuit 31 switches between a transmission connection connecting the first terminal 251 and the transmission circuit unit 33 and a reception connection connecting the first terminal 251 and the reception circuit unit 34.
The signal ground 32 is a ground connected to the second terminal 252, and maintains the second terminal 252 at a predetermined reference potential.

The transmission circuit unit 33 includes a drive pulse generation circuit 331, a transmission drive circuit 332, and the like.
The drive pulse generation circuit 331 is controlled by the microcomputer 35, and at the start timing when the ultrasonic device 20 executes the ultrasonic transmission / reception processing, the drive pulse generation circuit 331 generates a transmission pulse having a predetermined wave number having the same frequency as the ultrasonic oscillation frequency to generate a transmission drive circuit. Output to 332.
The transmission drive circuit 332 outputs a drive signal having a predetermined voltage to the first terminal 251 at the input timing of the transmission pulse. As a result, each ultrasonic transducer 24 is driven, and ultrasonic waves are output from the ultrasonic device 20 toward the object 1.

The reception circuit unit 34 includes a variable gain amplifier 341, a comparator 342, a first reception processing circuit 343, and the like.
The variable gain amplifier 341 changes the gain based on the control signal from the microcomputer 35, and amplifies the received signal output when the ultrasonic device 20 receives the ultrasonic wave with the set gain.
The comparator 342 receives the threshold voltage from the microcomputer 35, and detects the zero crossing point of the received signal whose signal voltage exceeds the threshold voltage among the received signals amplified by the variable gain amplifier 341. That is, the comparator 342 functions as a zero cross detection unit. Then, the comparator 342 outputs the zero cross detection pulse to the microcomputer 35 at the timing when the zero cross point is detected. In this embodiment, the threshold voltage set by the microcomputer 35 is a constant value.

The first reception processing circuit 343 receives the reception signal from the variable gain amplifier 341. The first reception processing circuit 343 includes a peak hold circuit and a waveform shaping circuit. That is, the first reception processing circuit 343 samples the input received signal at a predetermined sampling cycle and generates a signal waveform of the received signal. The signal waveform of this received signal shows the change in the signal voltage of the received signal with respect to time, and includes a plurality of peaks. Then, the first reception processing circuit 343 measures the peak voltage, which is the signal voltage of each peak in the signal waveform of the received signal. That is, the first reception processing circuit 343 of this embodiment functions as a voltage measuring unit. Further, the first reception processing circuit 343 outputs the peak voltage of each peak to the microcomputer 35.
Here, the first reception processing circuit 343 is configured to include a peak hold circuit and a waveform shaping circuit that forms a signal waveform of the received signal, but instead of the waveform shaping circuit, an envelope of the received signal is used. An envelope forming circuit to be formed may be provided, and in this case, the maximum signal voltage may be detected based on the envelope.

The microcomputer 35 includes a memory 351 that stores various programs and various data, and a processor 352 that executes an instruction set of the programs stored in the memory 351. Then, the microcomputer 35 functions as a transmission command unit 353, a gain setting unit 354, a reception setting unit 355, and a distance measurement unit 356 by executing the program stored in the memory 351 by the processor 352.

The transmission command unit 353 outputs a transmission pulse generation command to the drive pulse generation circuit 331. The transmission pulse generation command is issued based on the distance measurement request input from the external device connected to the ultrasonic measuring device 10. For example, the ultrasonic measuring device 10 of the present embodiment can be incorporated into an electronic device or an industrial device, and a transmission pulse is input by inputting a distance measurement request from a control unit of the electronic device or the industrial device. Command the generation of. The ultrasonic measuring device 10 may be provided with an input operation unit, or the user may operate the input operation unit to input a distance measurement request.

The gain setting unit 354 sets the gain of the variable gain amplifier 341 based on the peak voltage of each peak of the received signal input from the first reception processing circuit 343. At this time, the gain setting unit 354 sets the gain so that the predetermined peak included in the signal waveform of the received signal output from the variable gain amplifier 341 to the comparator 342 is equal to or higher than the threshold voltage.

The reception setting unit 355 calculates the time (zero cross detection time) from the ultrasonic transmission timing to the detection timing of the zero cross point. Here, in the present embodiment, the received signal is a signal output by the vibration of one wave of the vibrating unit 221, and when the vibrating unit 221 vibrates, the received signal including a plurality of peaks is output. Therefore, a zero cross detection pulse for the zero cross point of each peak exceeding the threshold voltage is input to the microcomputer 35 from the comparator 342. The reception setting unit 355 calculates the zero cross detection time for each of the zero cross points corresponding to each peak from these zero cross detection pulses.
Further, the reception setting unit 355 sets a zero cross point (reception zero cross point) as an ultrasonic wave reception timing based on the calculated zero cross detection time.

The distance measuring unit 356 calculates the distance from the ultrasonic device 20 to the object 1 based on the zero cross detection time corresponding to the received zero cross point from the ultrasonic transmission timing.

[Ultrasonic measurement method]
Next, the distance measurement process including the ultrasonic measurement method by the ultrasonic measurement device 10 will be described.
FIG. 4 is a flowchart showing the distance measurement process of the present embodiment. FIG. 5 is a timing chart of the transmission pulse, the reception signal, and the zero cross detection pulse in the ultrasonic transmission / reception processing of the present embodiment.
The ultrasonic wave transmission / reception process described in the present embodiment is a process of transmitting ultrasonic waves for a predetermined wave number and receiving the reflected waves. In the present embodiment, in order to measure the distance between the object 1 and the ultrasonic device 20, one ultrasonic transmission / reception process may be performed.
Further, in the present embodiment, the distance from the object 1 to the ultrasonic device 20 fluctuates at a predetermined speed, and an example in which the process of measuring the distance from the ultrasonic device 20 to the object 1 is performed a plurality of times. Shown.

When a distance measurement request is input from, for example, an external device or an input operation unit, the microcomputer 35 first initializes the variable m indicating the measurement times and sets m = 1 (step S1).
Next, the gain setting unit 354 of the microcomputer 35 sets the gain G _m and outputs the gain to the variable gain amplifier 341 (step S2). That is, in step S2, the initial gain G1 when m = ₁ is set in the variable gain amplifier 341. The initial gain G ₁ is stored in the memory 351 in advance, and the gain setting unit 354 _{reads the initial gain G 1} from the memory 351 and outputs the initial gain G 1 to the variable gain amplifier 341.

Next, the transmission command unit 353 switches the switching circuit 31 to the transmission connection, outputs a transmission pulse generation command to the drive pulse generation circuit 331, and transmits ultrasonic waves from the ultrasonic device 20 toward the object 1. (Step S3).
That is, the drive pulse generation circuit 331 generates a transmission pulse having a predetermined wave number having the same pulse frequency as the ultrasonic oscillation frequency based on the generation command, and outputs the transmission pulse to the transmission drive circuit 332. As a result, the transmission drive circuit 332 applies a drive voltage to each ultrasonic transducer 24 in synchronization with the rising timing of the transmission pulse.
Further, in the present embodiment, the timing at which the transmission pulse is transmitted from the drive pulse generation circuit 331 is defined as the transmission timing.

After that, the microcomputer 35 switches the switching circuit 31 to the reception connection (step S4).
When the reception connection is switched in step S4, the reception signal output from the ultrasonic device 20 is input to the reception circuit unit 34 when the ultrasonic device 20 receives the ultrasonic waves. This received signal is amplified by the variable gain amplifier 341 and then input to the comparator 342 and the first reception processing circuit 343.
_{The comparator 342 detects the zero cross point of the peak of the signal voltage equal to or higher than the threshold voltage Vth} among the peaks included in the received signal, and outputs the zero cross detection pulse to the microcomputer 35 at the detection timing of the zero cross point.
Further, the first reception processing circuit 343 samples the received signal input at a cycle sufficiently shorter than the ultrasonic cycle, forms a signal waveform of the received signal, and measures the peak voltage of each peak. Output to the microcomputer 35.
The microcomputer 35 receives the reception result including the zero cross detection pulse, the signal waveform of the reception signal, and the peak voltage of each peak output from the reception circuit unit 34 (step S5).

_{Next, the gain setting unit 354 detects the maximum value (maximum signal voltage VH m} ) of the peak voltage of each peak received in step S5 (step S6).
Then, the gain setting unit 354 _{determines whether or not VH m} = VH _{m-1 by using the maximum signal voltage VH m-1} in the m-1st measurement as a reference voltage (step S7). When m = 1, the preset initial reference voltage VH ₀ is stored in the memory 351 and it is determined whether or not _{VH 1} = VH _0.

If NO is determined in step S7, the reception zero cross point is not set by the reception setting unit 355, and the process proceeds to the gain setting step of step S8. That is, the gain setting unit 354, the gain _{G m-1} that has been set in the ultrasonic transmission and reception process of the m-1 th and reference gain, the gain _{G m} of the variable gain amplifier _341, G m = _{(VH m-1} / VH _m ) × G _{m-1 is} calculated. Then, the gain setting unit 354 _{outputs a new gain G m} to the variable gain amplifier 341. As a result, the gain of the variable gain amplifier 341 is changed from G _{m -1 to G m.} Thereafter, the flow returns to step S3, using the newly set gain G _m, implementing the ultrasonic transmission and reception process.

Here, the method of setting the threshold value in the present embodiment will be described in more detail based on FIG.
In the example shown in FIG. 5, five transmission pulses having the same pulse frequency as the ultrasonic oscillation frequency are input from the drive pulse generation circuit 331 to the transmission drive circuit 332. Therefore, the transmission drive circuit 332 inputs the periodic drive voltage of the pulse frequency to the ultrasonic device 20 by 5 waves. Therefore, the vibrating unit 221 vibrates by driving the piezoelectric element 23 for five waves, and then damped and vibrates according to the elasticity of the vibrating unit 221. The vibration frequency at the time of attenuated vibration is the resonance frequency of the ultrasonic transducer 24, but in the present embodiment, the frequency of the transmission pulse is the same frequency as the resonance frequency of the ultrasonic transducer 24.

On the other hand, when the ultrasonic wave transmitted from the ultrasonic device 20 is reflected by the object 1 and the ultrasonic wave is received by the ultrasonic transducer 24, the vibrating unit 221 is displaced, and then according to the elasticity of the vibrating unit 221. It resonates and vibrates and becomes a reverberant component. In the present embodiment, the ultrasonic waves of five waves reflected by the object 1 are received at the same pulse frequency as the oscillation frequency of the ultrasonic waves. Therefore, the phases of the vibration of the vibrating unit 221 due to the reception of the reflected ultrasonic waves and the vibration of the reverberation component match, and as shown in FIG. 5, the peak voltage of each peak of the received signal gradually increases. Then, after the last ultrasonic wave reflected by the object 1 is received by the ultrasonic device 20, the vibrating unit 221 damped and vibrates, so that the peak voltage of each peak of the received signal is gradually reduced. Therefore, when observing a plurality of received signals in chronological order, the peak voltage of the peak in the first half and the peak voltage of the peak in the second half become substantially symmetrical with the reception timing of the peak of the _{maximum signal voltage V Hm as a boundary.} ..

By the way, in the example shown in FIG. 5, the distance between the object 1 and the ultrasonic device 20 is increased at the mth measurement as compared with the m-1th measurement. In this case, as shown in FIG. 5, the time until the reflected ultrasonic wave is received by the ultrasonic device 20 increases by the time corresponding to the distance, and the signal voltage of the received signal also decreases.
However, the signal waveform of the received signal has substantially the same shape regardless of the distance between the object 1 and the ultrasonic device 20. That is, the peak voltage of the peak in the first half and the peak voltage of the peak in the second half are substantially symmetrical with the reception timing of the peak of the maximum signal voltage VH _{m as a boundary.}
Therefore, as described above, if the gain G _m set in the variable gain amplifier 341 is amplified as G _m = (VH _m-1 / VH _m ) × G _m-1 , the object 1 and the ultrasonic device 20 can be obtained. Even if the distance is changed, a received signal with a signal waveform having substantially the same shape is always obtained, and the maximum signal voltage VH _m is also controlled to be a constant value, that is, the initial reference voltage VH _{0 recorded in the memory 351.} Will be done. In this case, the predetermined third peak (second peak in the present embodiment) in the signal waveform of the received signal always _{exceeds the threshold voltage Vth} , and the zero cross point of this second peak is set as the reception zero cross point. can do.

On the other hand, if YES is determined in step S7, the reception setting unit 355 sets the zero cross point at the preset position as the reception zero cross point (step S9: zero cross detection step). For example, in the present embodiment, as shown in FIG. 5, the zero cross point corresponding to the first input zero cross detection pulse is set as the reception zero cross point. Further, the reception setting unit 355 calculates the _{zero cross detection time t d} , which is the time from the ultrasonic transmission timing to the detection timing of the set reception zero cross point.
After that, the distance measuring unit 356 calculates the distance from the ultrasonic device 20 to the object 1 based on _{the zero cross detection time t d and the speed of sound (step S10).
Further, the gain setting unit 354 records the maximum signal voltage VH m} obtained at the time of remeasurement as a reference voltage in the memory 351 and records the gain G _m at the time of remeasurement as a reference gain in the memory 351.

After the above, the microcomputer 35 adds 1 to the variable m (step S11), and determines, for example, whether or not to end the measurement (step S12). In step S12, the microcomputer 35 receives, for example, an operation signal to end the measurement by an input operation by the measurer, or when the number of measurements (variable m) reaches a preset number of times. , Judge that the measurement is finished.
If NO is determined in step S12, that is, if the measurement is to be continued, the process returns to step S3. As a result, the ultrasonic measuring device 10 restarts the distance measurement between the ultrasonic device 20 and the object 1.

[Action and effect of this embodiment]
The ultrasonic measuring device 10 of the present embodiment includes an ultrasonic device 20 and a control circuit 30. The ultrasonic device 20 performs an ultrasonic transmission / reception process of transmitting ultrasonic waves to the object 1 based on the transmission pulse and receiving the reflected ultrasonic waves reflected by the object 1, and a plurality of ultrasonic devices are received by receiving the ultrasonic waves. Outputs the received signal of the signal waveform including the peak of. The control circuit 30 includes a variable gain amplifier 341 that amplifies the received signal output from the ultrasonic device 20, a comparator 342 that detects a zero crossing point of the received signal output from the variable gain amplifier 341, and a microcomputer 35. .. Then, the microcomputer 35 functions as a gain setting unit 354, and the gain of the variable gain amplifier 341 is set so that the predetermined peak included in the waveform of the received signal output from the variable gain amplifier 341 is equal to or higher than the _{threshold voltage Vth.} To set.
That is, when the ultrasonic measuring device 10 detects the reception zero cross point set as the reception timing in the zero cross detection step of step S9, the predetermined th peak among the plurality of peaks included in the reception signal is the threshold voltage V. _The gain setting step is performed so that the value becomes th or more.

As a result, even if the distance between the object 1 and the ultrasonic device 20 fluctuates for each measurement and the signal voltage of the received signal increases or decreases, the predetermined peak can always be detected, and the reception zero cross point can be detected. The position of is not changed. Therefore, the inconvenience of offset error can be suppressed, and highly accurate distance measurement can be performed.
Further, when the distance between the object 1 and the ultrasonic device 20 fluctuates, it is sufficient to perform the ultrasonic transmission / reception processing twice, and it is not necessary to perform the ultrasonic wave transmission / reception processing three times or more, so that the capacity is large. The memory 351 having the storage capacity of is unnecessary. Therefore, in the present embodiment, the configuration of the ultrasonic measuring device 10 can be simplified, and the processing time related to the distance measurement processing can be shortened.

In the present embodiment, the reception circuit unit 34 includes a first reception processing circuit 343 that measures the signal voltages of a plurality of peaks included in the reception signal output from the variable gain amplifier 341. Then, the gain setting unit 354 of the microcomputer 35 _{detects the maximum signal voltage VH m} among the peak voltages for the plurality of peaks, and the maximum signal voltage VH _m is the reference voltage m-1st maximum signal voltage VH. when _{the m-1} different sets the gain _{G m} for a _{VH m-1} / VH _m times the m-1 th gain _{G m-1} is the reference gain.
As a result, even if the distance between the object 1 and the ultrasonic device 20 fluctuates for each measurement and the signal voltage of the received signal increases or decreases, the maximum signal voltage VH _m of the received signal becomes the initial reference voltage VH _0. As described above, the gain of the variable gain amplifier 341 is adjusted. Therefore, the predetermined peak in the received signal always _{becomes the peak voltage exceeding the threshold voltage Vth} , and the reception zero crossing point can be set appropriately.

[Second Embodiment]
Next, the second embodiment will be described.
The ultrasonic measuring device 10 of the first embodiment is based on the maximum signal voltage measured in the m-1st ultrasonic transmission / reception process, and the gain of the variable gain amplifier 341 when the mth ultrasonic wave transmission / reception process is performed. It was set. On the other hand, the second embodiment is different from the first embodiment in that the gain is set based on the envelope of the received signal.
FIG. 6 is a schematic view showing a schematic configuration of the ultrasonic measuring device 10A of the second embodiment.
The configurations already described are designated by the same reference numerals, and the description thereof will be omitted or simplified.

The ultrasonic measuring device 10A of the present embodiment includes an ultrasonic device 20 and a control circuit 30A. Since the ultrasonic device 20 has the same configuration as that of the first embodiment, the description thereof is omitted here.
As shown in FIG. 6, the control circuit 30A includes a switching circuit 31, a signal ground 32, a transmission circuit unit 33, a reception circuit unit 34A, and a microcomputer 35A. Further, in the present embodiment, the receiving circuit unit 34A includes a variable gain amplifier 341, a comparator 342, and a second receiving processing circuit 343A.
The second reception processing circuit 343A receives the reception signal from the variable gain amplifier 341. The second reception processing circuit 343A includes an envelope forming circuit and a second comparator. In such a second reception processing circuit 343A, the envelope forming circuit forms the envelope waveform of the input received signal. Then, the second comparator detects the time width of the period in _{which the signal voltage exceeds the threshold voltage V th} of the formed envelopes based on the _{threshold voltage V th input from the microcomputer 35A.} That is, in the present embodiment, the second reception processing circuit 343A functions as an envelope processing unit. Further, the second reception processing circuit 343A outputs the time width of the period exceeding the _{threshold voltage Vth in the envelope to the microcomputer 35A.}

Further, the processor 352 of the microcomputer 35A of the present embodiment executes the instruction set of the program recorded in the memory 351 to execute the transmission command unit 353, the second gain setting unit 354A, the reception setting unit 355, and the distance measurement unit. Functions as 356.
The second gain setting unit 354A sets the gain of the variable gain amplifier 341 based on the time width input from the second reception processing circuit 343A. At this time, the second gain setting unit 354A sets the gain so that the predetermined peak included in the signal waveform of the received signal output from the variable gain amplifier 341 to the comparator 342 is equal to or higher than the _{threshold voltage Vth.} ..

Next, the ultrasonic measurement method using the ultrasonic measuring device 10A of the present embodiment will be described. FIG. 7 is a flowchart showing the distance measurement process of the present embodiment. FIG. 8 is a timing chart of the transmission pulse, the reception signal, the zero cross detection pulse, the envelope, and the time width in the ultrasonic transmission / reception processing of the present embodiment.
In the present embodiment, the processes of steps S1 to S4 are carried out as in the first embodiment. As a result, in step S5A, the microcomputer 35A receives the zero cross detection pulse and _{the time width TW m} for a period exceeding the _{threshold voltage V th} in the envelope as a reception result.
After that, the second gain setting unit 354A _{determines whether or not TW m} = TW _{m-1 with the time width TW m-1 in the first} measurement of m-1 as the reference time width (step S7A). When m = 1, the preset initial time width TW ₀ is stored in the memory 351 and it is determined whether or not _{TW 1} = TW _0.

If NO is determined in step S7A, the second gain setting unit 354A reads the first calibration curve data stored in advance in the memory 351. FIG. 9 is a diagram showing an example of the first calibration curve data. As shown in FIG. 9, the first calibration line data is data showing _{the relationship between the time width of the period in which the signal voltage exceeds the threshold voltage Vth} in the envelope and the gain set in the variable gain amplifier 341. For example, the first calibration line data records that the gain of the variable gain amplifier 341 _{is set to the reference gain G 0} when the time width TW is a predetermined reference time width (initial time width TW _0). Data is recorded to the effect that the gain is increased as the time width TW becomes smaller.
Then, the second gain setting unit 354A reads out the gain G _{m corresponding to the time width TW m} received in step S5A from the first calibration curve data and outputs the gain G m to the variable gain amplifier 341 (step S8A).
After that, the process returns to step S3 and remeasurement is performed as in the first embodiment. Further, the second gain setting unit 354A _{records in the memory 351 with the time width TW m} obtained at the time of remeasurement as the reference time width.

Here, the method of setting the threshold value in the present embodiment will be described in more detail based on FIG.
In the example shown in FIG. 8, the distance between the object 1 and the ultrasonic device 20 is increased at the mth measurement as compared with the m-1th measurement.
In this case, as shown in FIG. 8, the time until the reflected ultrasonic wave is received by the ultrasonic device 20 increases by the time corresponding to the distance, and the signal voltage of the received signal also decreases. Therefore, in the envelope waveform of the received signal, the time width TW _{m exceeding the threshold voltage V th} is shortened, and the number of peaks exceeding the _{threshold voltage V th is also reduced.
On the other hand, the gain G m} set in the variable gain amplifier 341 is set to _{G m} = G ₀ × p based on the first calibration curve data. As a result, even if the distance between the object 1 and the ultrasonic device 20 fluctuates, the time width TW _{m exceeding the threshold voltage Vth} is always controlled to a constant value in the envelope waveform. That is, the number of peaks exceeding the _{threshold voltage Vth is always constant.} In this case, the predetermined third (for example, second) peak in the signal waveform of the received signal always _{exceeds the threshold voltage Vth} , and the zero crossing point of this second peak can be set as the receiving zero crossing point.
The other processes are the same as those in the first embodiment.

[Action and effect of the second embodiment]
In the ultrasonic measuring device 10A of the present embodiment, the receiving circuit unit 34A forms an envelope of the received signal output from the variable gain amplifier 341, and sets the time width of the period during _{which the envelope becomes the threshold voltage Vth or more.} It is provided with an envelope processing unit for detection. Then, the microcomputer 35A functions as the second gain setting unit 354A, reads the gain G _{m with respect to the time width TW m} detected by the second reception processing circuit 343A based on the first calibration curve data, _{and reads the gain G m,} and is a variable gain amplifier. It is set as a gain of 341.
Even in such an embodiment, the same effect as that of the first embodiment can be obtained.
Further, even if the distance between the object 1 and the ultrasonic device 20 fluctuates for each measurement, the time width of the period exceeding the _{threshold voltage Vth on the envelope is always constant.} Therefore, the predetermined peak included in the received signal is also _{controlled so as to always exceed the threshold voltage Vth,} and the position of the reception zero crossing point does not fluctuate. Therefore, the inconvenience of offset error can be suppressed, and highly accurate distance measurement can be performed.

[Third Embodiment]
Next, the third embodiment will be described.
The third embodiment is different from the first embodiment and the second embodiment in that the gain is set based on the number of peaks exceeding the _{threshold voltage Vth.}
FIG. 10 is a schematic view showing a schematic configuration of the ultrasonic measuring device 10B of the third embodiment.

The ultrasonic measuring device 10B of the present embodiment includes an ultrasonic device 20 and a control circuit 30B.
As shown in FIG. 10, the control circuit 30B includes a switching circuit 31, a signal ground 32, a transmission circuit unit 33, a reception circuit unit 34B, and a microcomputer 35B. Further, in the present embodiment, the receiving circuit unit 34B is composed of a variable gain amplifier 341 and a comparator 342.

Further, the processor 352 of the microcomputer 35B of the present embodiment executes the instruction set of the program recorded in the memory 351 to execute the transmission command unit 353, the third gain setting unit 354B, the reception setting unit 355, and the distance measurement unit. Functions as 356.
The third gain setting unit 354B sets the gain of the variable gain amplifier 341 based on the number of zero cross detection pulses output from the comparator 342, that is, _{the number of peaks included in the received signal that exceed the threshold voltage Vth.} To do. At this time, the third gain setting unit 354B sets the gain so that the predetermined peak included in the signal waveform of the received signal output from the variable gain amplifier 341 to the comparator 342 is equal to or higher than the _{threshold voltage Vth.} ..

Next, the ultrasonic measurement method using the ultrasonic measuring device 10B of the present embodiment will be described. FIG. 11 is a flowchart showing the distance measurement process of the present embodiment. FIG. 12 is a timing chart of the transmission pulse, the reception signal, and the zero cross detection pulse in the ultrasonic transmission / reception processing of the present embodiment.
In the present embodiment, the processes of steps S1 to S4 are carried out as in the first embodiment. As a result, in step S5B, the microcomputer 35A receives the zero cross detection pulse as a reception result.
After that, the third gain setting unit 354B counts the zero cross detection pulse received in step S5B, that is, counts the number of peaks (peak number S _{m ) exceeding the threshold voltage Vth} (step S6B).
Further, the third gain setting unit 354B _{determines whether or not S m} = S _m-1 with respect to the _{number of peaks S m-1} counted in the m-1st time (step S7B). When m = 1, the preset initial peak number S ₀ is stored in the memory 351 and it is determined whether or not _{S 1} = S _0.

If NO is determined in step S7B, the third gain setting unit 354B reads the second calibration curve data stored in advance in the memory 351. FIG. 13 is a diagram showing an example of the second calibration curve data. As shown in FIG. 13, the second calibration line data is data showing _{the relationship between the number of peaks in which the signal voltage included in the received signal exceeds the threshold voltage Vth} and the gain set in the variable gain amplifier 341. .. For example, in the second calibration curve data, _{it is recorded that the gain of the variable gain amplifier 341 is set to the reference gain G 0} when the number of peaks is 6, and the gain is increased as the number of peaks decreases. Record the data to the effect.
Then, the third gain setting unit 354B reads out the gain G _{m corresponding to the number of peaks S m} received in step S5B from the second calibration curve data and outputs the gain G m to the variable gain amplifier 341 (step S8B).
After that, the process returns to step S3 and remeasurement is performed as in the first embodiment. Further, the third gain setting unit 354B _{records in the memory 351 the peak number S m} obtained at the time of remeasurement as the reference peak number.

Here, the method of setting the threshold value in the present embodiment will be described in more detail based on FIG.
In the example shown in FIG. 12, the distance between the object 1 and the ultrasonic device 20 is increased at the mth measurement as compared with the m-1th measurement. In this case, as shown in FIG. 12, the time until the reflected ultrasonic wave is received by the ultrasonic device 20 increases by the time corresponding to the distance, and the signal voltage of the received signal also decreases. Therefore, the number of peaks decreases.
_{On the other hand, the gain G m} set in the variable gain amplifier 341 is set to _{G m} = G ₀ × p based on the second calibration curve data. As a result, even if the distance between the object 1 and the ultrasonic device 20 fluctuates, the number of peaks exceeding the _{threshold voltage Vth is always controlled to a constant value in the received signal.} In this case, the predetermined third (for example, second) peak in the signal waveform of the received signal always _{exceeds the threshold voltage Vth} , and the zero crossing point of this second peak can be set as the receiving zero crossing point.
The other processes are the same as those in the first embodiment.

[Action and effect of the third embodiment]
In the ultrasonic measuring device 10B of the present embodiment, the microcomputer 35B functions as a third gain setting unit 354B, detects the number of peaks S _m based on the zero-cross detection pulses output from the comparator 342. Then, the third gain setting unit 354B reads the gain G _{m with respect to the number of peaks S m} from the second calibration curve data and sets it as the gain of the variable gain amplifier 341.
Even in such an embodiment, the same effects as those in the first embodiment and the second embodiment can be obtained.
Further, even if the distance between the object 1 and the ultrasonic device 20 fluctuates for each measurement, the number of peaks having _{a threshold voltage Vth or higher included in the received signal is always constant.} Therefore, the predetermined peak included in the received signal is also _{controlled so as to always exceed the threshold voltage Vth,} and the position of the reception zero crossing point does not fluctuate. Therefore, the inconvenience of offset error can be suppressed, and highly accurate distance measurement can be performed.
Further, in the present embodiment, since the zero cross detection pulse may be counted by the microcomputer 35B, the first reception processing circuit 343 and the second reception processing circuit 343A are not required, and the configuration of the control circuit 30B can be simplified. Can be done.

[Modification example]
The present invention is not limited to the above-described embodiments, and the present invention includes configurations obtained by modifying, improving, and appropriately combining the respective embodiments within the range in which the object of the present invention can be achieved. It is a thing.

[Modification 1]
In the first embodiment, in step S7, _{it is determined whether or not VH m} = VH _m-1 , but the present invention is not limited to this. It may be determined whether or not | VH _m −VH _m-1 | is equal to or less than a predetermined margin set in advance. Further, _{it may be determined whether or not VH m} / VH _m-1 is within a predetermined allowable range centered on 1. That is, in the first embodiment, the m-th maximum signal voltage VH _m and the reference voltage m-1st maximum signal voltage VH _m-1 do not have to be exactly the same, and are set in advance. If it is within the margin or the allowable range, it may be determined as Yes in step S7.

The same applies to the second embodiment, and in step S7A, _{it is determined whether or not TW m} = TW _m-1 , but the present invention is not limited to this. For example, the second gain setting unit 354A may _{determine whether | TW m} −TW _m-1 | is equal to or less than a predetermined margin set in advance, and TW _m / TW _m-1 is set to 1. It may be determined whether or not it is within a predetermined allowable range centered on it.

[Modification 2]
In the first embodiment, in step S7, the maximum signal voltage VH _m measured in the m-th ultrasonic transmission / reception process and the maximum signal voltage VH _{m-1 measured in the m-1th ultrasonic transmission / reception process are combined.} Compared. That is, the maximum signal voltage VH _{m-1 at the m-1st time} is used as the reference voltage. On the other hand, the maximum signal voltage VH _{m is compared with the initial reference voltage VH 0 in} which the reference voltage is recorded in the memory 351 in advance, and the gain G _m is set to G _m = (VH ₀ / VH _m ) × G. _It may be calculated by 0.
The same applies to the second embodiment, and in step S7A, the time width TW _m measured in the m-th ultrasonic transmission / reception process and the time width TW _{m-1 measured in the m-1th ultrasonic wave transmission / reception process.} However, the time width TW _m may be compared with the _{initial time width TW 0} previously recorded in the memory 351. Similarly, in the third embodiment, in step S7B, the peak number S _m may be compared with the _{initial peak number S 0} previously recorded in the memory 351.

[Modification 3]
In the first embodiment, the gain setting unit 354 _{calculates the gain G m} by G _m = (VH ₀ / VH _m ) × G ₀ , but the gain is not limited to this. For example, as in the second embodiment and the third embodiment, the relationship data indicating the relationship between the maximum signal voltage VH and the gain G may be stored in the memory 351 in advance. In this case, when the maximum signal voltage VH _m is detected, it is _{only necessary to read the gain corresponding to the maximum signal voltage VH m} from the related data, and the processing speed can be increased.

[Modification example 4]
In the third embodiment, an example is shown in which the third gain setting unit 354B reads out the gain corresponding to the number of peaks based on the second calibration curve data showing the relationship between the number of peaks and the gain. On the other hand, as the second calibration curve data, the calibration curve data showing the relationship between the time width of the period during which the plurality of received signals continuously exceed the threshold voltage and the gain may be used.
That is, since the received signal is output at the same frequency as the ultrasonic frequency, the time during which a plurality of received signals continuously exceed the threshold voltage by integrating the ultrasonic period with respect to the number of peaks. It becomes the width. In other words, the time width of the period during which the plurality of received signals continuously exceed the threshold voltage and the number of peaks are in a proportional relationship. Therefore, the third gain setting unit 354B calculates the time width of the period during which the plurality of received signals continuously exceed the threshold voltage based on the number of detected peaks, and sets the gain corresponding to the time width as described above. (Ii) By reading out based on the calibration curve data, the same effect as that of the third embodiment can be obtained.

[Modification 5]
In each of the above-described embodiments, an example is shown in which the signal voltage of the received signal decreases due to the fluctuation of the distance from the object 1 to the ultrasonic device 20, but the present invention is not limited to this. For example, when the signal voltage of the received signal changes depending on the material of the reflector, calibration may be performed to set an appropriate gain by the method shown in each of the above-described embodiments. In this case, the gain can be set so that the signal voltage of the received signal becomes the reference voltage level even for reflectors made of various materials.

[Modification 6]
The ultrasonic measuring devices 10, 10A, and 10B described in each of the above embodiments may be used as a single measurement sensor for measuring the distance to the object 1, or may be used by being incorporated into various electronic devices or industrial devices. Good.
For example, the ultrasonic measuring devices 10, 10A and 10B may be incorporated in a printing device such as an inkjet printer. In this case, the ultrasonic measuring devices 10, 10A, and 10B may be mounted on the carriage on which the ink head that ejects ink to the print medium is mounted, and the distance between the carriage and the print medium may be measured. Alternatively, the ink tank may be provided with ultrasonic measuring devices 10, 10A, 10B to measure the position of the liquid level in the ink tank.
Further, in an industrial device such as a robot arm, ultrasonic measuring devices 10, 10A and 10B may be incorporated in an arm that grips an object to measure the distance from the arm to the object.

1 ... Object, 10,10A, 10B ... Ultrasonic measuring device, 20 ... Ultrasonic device (ultrasonic transmitter, ultrasonic receiver), 30,30A, 30B ... Control circuit, 31 ... Switching circuit, 32 ... Signal Ground, 33 ... Transmission circuit unit, 34, 34A, 34B ... Reception circuit unit, 35, 35A, 35B ... Microcomputer, 251 ... First terminal, 252 ... Second terminal, 331 ... Drive pulse generation circuit, 332 ... Transmission drive circuit , 341 ... Variable gain amplifier, 342 ... Comparator, 343 ... First reception processing circuit, 343A ... Second reception processing circuit, 351 ... Memory, 352 ... Processor, 353 ... Transmission command unit, 354 ... Gain setting unit, 354A ... Second gain setting unit, 354B ... Third gain setting unit, 355 ... Reception setting unit, 356 ... Distance measurement unit, TW _m ... Time width, TW _m-1 ... Time width, VH _m ... Maximum signal voltage, VH _{m- 1} ... Maximum signal voltage, V _th ... Threshold voltage, td ... Zero cross detection time.

Claims (8)

An ultrasonic transmitter that transmits ultrasonic waves to an object, an ultrasonic receiver that receives ultrasonic waves reflected by the object and outputs a reception signal of a signal waveform including a plurality of peaks, and the received signal. It is an ultrasonic measurement method of an ultrasonic measuring device equipped with a variable gain amplifier for amplification.
A gain setting step for setting the gain of the variable gain amplifier is performed.
The gain setting step is an envelope obtained so that a predetermined first peak included in the signal waveform of the received signal output from the variable gain amplifier is equal to or higher than the threshold voltage, or is obtained from a peak having the threshold voltage or higher. An ultrasonic measurement method characterized in that the gain of the variable gain amplifier is set so that the time width of is set to a predetermined time width. In the ultrasonic measurement method according to claim 1,
The gain setting step detects the maximum signal voltage among the plurality of signal voltages of the peaks included in the received signal, and when the maximum signal voltage is different from a predetermined reference voltage, the gain setting step ( An ultrasonic measurement method characterized in that the gain is set to be doubled (reference voltage / maximum signal voltage). In the ultrasonic measurement method according to claim 1,
The gain setting step forms the envelope, detects the time width of the period during which the signal voltage of the envelope is equal to or higher than the threshold voltage, and the first calibration line data showing the relationship between the time width and the gain. A method for measuring an ultrasonic wave, which comprises setting the gain with respect to the detected time width based on the above. In the ultrasonic measurement method according to claim 1,
The gain setting step measures the number of the peaks above the threshold voltage included in the received signal, and is obtained from the relationship between the number of peaks above the threshold voltage and the gain, or the number of peaks. To set the gain with respect to the number of measured peaks based on the second calibration line data showing the relationship between the gain and the time width of the period during which the plurality of received signals continuously exceed the threshold voltage. An ultrasonic measurement method characterized by. An ultrasonic transmitter that transmits ultrasonic waves to an object,
An ultrasonic receiver that receives ultrasonic waves reflected by the object and outputs a received signal of a signal waveform including a plurality of peaks.
A variable gain amplifier that amplifies the received signal and
The time width of the envelope obtained so that the predetermined first peak included in the signal waveform of the received signal output from the variable gain amplifier is equal to or higher than the threshold voltage or the peak obtained from the peak equal to or higher than the threshold voltage is a predetermined time. A control unit that sets the gain of the variable gain amplifier so that it has a width, and
An ultrasonic measuring device characterized by being provided with. In the ultrasonic measuring apparatus according to claim 5,
A voltage measuring unit for measuring the signal voltages of a plurality of the peaks included in the received signal output from the variable gain amplifier is provided.
The control unit detects the maximum signal voltage among the plurality of signal voltages of the peaks measured by the voltage measuring unit, and when the maximum signal voltage is different from a predetermined reference voltage, the control unit refers to the reference gain. An ultrasonic measuring device characterized in that the gain is set to be doubled (reference voltage / maximum signal voltage). In the ultrasonic measuring apparatus according to claim 5,
It is provided with an envelope processing unit that forms the envelope output from the variable gain amplifier and detects the time width of the period during which the signal voltage of the envelope becomes equal to or higher than the threshold voltage.
The control unit sets the gain for the time width detected by the envelope processing unit based on the first calibration curve data showing the relationship between the time width and the gain. Measuring device. In the ultrasonic measuring apparatus according to claim 5,
Further, a zero cross detection unit for detecting a zero cross point of the received signal output from the variable gain amplifier is provided.
The zero-cross detection unit outputs a zero-cross detection pulse for the peak having a threshold voltage or higher included in the waveform of the received signal.
Based on the zero-cross detection pulse output from the zero-cross detection unit, the control unit measures the number of the peaks above the threshold voltage included in the received signal, and sets the number of peaks above the threshold voltage. Based on the relationship with the gain or the second calibration line data showing the relationship between the gain and the time width of the period during which the plurality of received signals obtained from the number of peaks continuously exceed the threshold voltage. , An ultrasonic measuring device, characterized in that the gain is set with respect to the number of measured peaks.

Images