JP2013165883A - Subject information acquisition apparatus, and method for controlling the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a subject information acquisition apparatus capable of correcting variations in the transmission characteristics and reception characteristics of a CMUT (Capacitive Micromachined Ultrasonic Transducer) element.SOLUTION: A subject information acquisition apparatus for use includes: an output means for outputting a pulse for transmission and a pulse for characteristic acquisition; a capacitive transducer which includes a plurality of elements transmitting a corresponding acoustic wave when the pulse for the transmission is input and outputting a corresponding electric element when receiving the acoustic wave; a first conversion means for converting an electric current into a voltage, which current is output when the pulse for the acquisition of the characteristics is input into the elements; a characteristic acquisition means for acquiring reception characteristics of the elements from a signal output from the first conversion means; a second conversion means for converting an electric current into a voltage, which current is output when the elements receive a reflected wave transmitted from a transmission/reception means and reflected from the subject; a generation means for generating subject information from output produced by the second conversion means; and a control means for reducing differences among the reception characteristics of the respective elements in the reception of the reflective wave.

Description

  The present invention relates to a subject information acquisition apparatus and a control method thereof.

As a transducer for transmitting and receiving ultrasonic waves, a capacitive micromachined ultrasonic transducer (CMUT), which is a capacitive ultrasonic transducer, has been proposed.
The CMUT is manufactured using a micro electro mechanical systems (MEMS) process that applies a semiconductor process. In addition, there is a measurement method for obtaining information on a measurement target by transmitting an ultrasonic wave to the measurement target using an ultrasonic transducer and receiving the ultrasonic wave reflected by the measurement target. As a transmission / reception transducer used in this measurement method, a method using a CMUT having a characteristic that the frequency range of ultrasonic waves to be transmitted / received is relatively wide (broadband) has been proposed.

JP 2011-004280 A

Conventionally, when transmitting and receiving ultrasonic waves using CMUT, both transmission wave output and reception wave input are performed in the same CMUT element.
However, in the CMUT element, there are variations in capacitance and the like due to the semiconductor process, and therefore the transmission characteristic and the reception characteristic vary for each CMUT element. When an ultrasonic beam is transmitted without considering variations in transmission characteristics, there is a problem that a desired transmission beam is not formed and the image quality of the acquired ultrasonic image is deteriorated. Note that examples of reception characteristics include the intensity of an electric signal output when receiving the same ultrasonic wave and the difference of each waveform element. Further, as an example of transmission characteristics, there is a difference for each element of ultrasonic waves transmitted when driven by pulses having the same voltage and waveform.

In addition, even if the transmission beam is correctly formed, if reception beam forming is performed without considering the variation in reception characteristics for each CMUT element, the image quality of the acquired ultrasonic image is also deteriorated. is there.
In addition, when a transmission waveform is output, since a high voltage is applied to the CMUT element, there is a problem that transmission characteristics and reception characteristics change with time in the CMUT element.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a subject information acquisition apparatus capable of correcting variations in transmission characteristics and reception characteristics of CMUT elements.

The present invention employs the following configuration. That is, an output means for outputting a transmission pulse and a characteristic acquisition pulse;
An electrostatic capacitance type including a plurality of elements that transmit an acoustic wave corresponding to the transmission pulse when the transmission pulse is input and output a current corresponding to the acoustic wave when the acoustic wave is received Transmitting / receiving means comprising a transducer;
First conversion means for converting a current output from the element into a voltage when the characteristic acquisition pulse is input to the element of the transmission / reception means;
Based on the signal output from the first conversion means, characteristic acquisition means for acquiring the reception characteristics of the elements of the transmission / reception means;
Second conversion means for converting a current output when the transmission / reception means receives a reflected wave transmitted from the transmission / reception means and reflected by a subject to a voltage;
Generating means for generating subject information inside the subject based on the output of the second conversion means;
Control means for performing control to reduce a difference for each element of the reception characteristic acquired by the characteristic acquisition means when receiving the reflected wave;
A subject information acquisition apparatus characterized by comprising:

The present invention also adopts the following configuration. That is, an output unit that outputs a transmission pulse and a characteristic acquisition pulse under the control of the control unit;
An electrostatic capacitance type including a plurality of elements that transmit an acoustic wave corresponding to the transmission pulse when the transmission pulse is input and output a current corresponding to the acoustic wave when the acoustic wave is received Transmitting / receiving means comprising a transducer;
Conversion means for converting a current output from the element into a voltage when the characteristic acquisition pulse is input to the element of the transmission / reception means;
Based on the signal output from the conversion means, characteristic acquisition means for acquiring the transmission characteristics of the elements of the transmission / reception means;
Generating means for generating subject information inside the subject based on the reflected wave received from the transmitting / receiving means after being transmitted from the transmitting / receiving means and reflected by the subject;
Have
The control means controls the output means so as to reduce a difference for each element of the transmission characteristic acquired by the characteristic acquisition means when an acoustic wave is transmitted from the transmission / reception means to the subject. This is a characteristic object information acquisition apparatus.

The present invention also adopts the following configuration. That is, a control method of a subject information acquisition apparatus that includes a transmission / reception unit including a capacitive transducer including a plurality of elements, and acquires subject information based on an acoustic wave received by the transmission / reception unit,
A characteristic acquisition step of acquiring a reception characteristic of the element of the transmission / reception means, and an information acquisition step of acquiring subject information from the subject;
The characteristic acquisition step includes:
Outputting a characteristic acquisition pulse to the element of the transceiver means;
Converting the current output from the element into a voltage when the characteristic acquisition pulse is input to the element of the transmitting and receiving means;
Obtaining reception characteristics for each element of the transmission / reception means based on the signal converted to the voltage,
The information acquisition step includes
The transmitting / receiving means receiving a transmission pulse and transmitting an acoustic wave corresponding to the pulse;
The transmitting / receiving means receiving a reflected wave reflected by the subject from the acoustic wave transmitted from the transmitting / receiving means;
The signal based on the current output from the element when the reflected wave is received is processed to reduce the difference in the reception characteristics for each element, and object information inside the object is generated. And a method for controlling a subject information acquiring apparatus.

The present invention also adopts the following configuration. That is, a control method of a subject information acquisition apparatus that includes a transmission / reception unit including a capacitive transducer including a plurality of elements, and acquires subject information based on an acoustic wave received by the transmission / reception unit,
A characteristic acquisition step of acquiring a transmission characteristic of an element of the transmission / reception means, and an information acquisition step of acquiring subject information from the subject,
The characteristic acquisition step includes:
Outputting a characteristic acquisition pulse to the element;
Converting the current output when the characteristic acquisition pulse is input to the element of the transmission / reception means into a voltage;
Obtaining a transmission characteristic for each element of the transmission / reception means based on the signal converted into the voltage,
The information acquisition step includes
Outputting a transmission pulse so as to reduce the difference between the elements of the transmission characteristics during transmission of the acoustic wave to the subject; and
The transmitting / receiving means transmitting an acoustic wave corresponding to the transmission pulse;
The transmitting / receiving means receiving a reflected wave reflected by the subject from the acoustic wave transmitted from the transmitting / receiving means;
And a step of generating subject information inside the subject based on the reflected wave received by the transmitting / receiving means.

  ADVANTAGE OF THE INVENTION According to this invention, the subject information acquisition apparatus which can correct | amend the transmission characteristic and reception characteristic dispersion | variation of a CMUT element can be provided.

The figure which shows the structure of the subject information acquisition apparatus based on embodiment of this invention. The figure which shows the structure of the subject information acquisition apparatus based on embodiment of a prior art example. The figure which shows the structure of a part of subject information acquisition apparatus based on 1st Embodiment. The figure which shows the structure of the waveform output control part based on 1st Embodiment. The figure which shows the structure of the receiving beam shaping apparatus based on 1st Embodiment. The figure which shows the operation | movement flow of the subject information acquisition apparatus based on 1st-2nd embodiment. The figure which shows the structure of a part of subject information acquisition apparatus based on 2nd Embodiment. The figure which shows the structure of a part of subject information acquisition apparatus based on 3rd Embodiment. The figure which shows the structure of the receiving beam shaping apparatus based on 3rd Embodiment. The figure which shows the one part structure of the subject information acquisition apparatus based on 4th Embodiment. The figure which shows the structure of a CMUT element.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. However, the dimensions, materials, shapes, and relative arrangements of the components described below should be changed as appropriate according to the configuration of the apparatus to which the invention is applied and various conditions. It is not intended to limit the following description.

For objects to which the present invention is applied, an acoustic wave such as an ultrasonic wave is transmitted to the subject, a reflected wave (echo wave) reflected and propagated inside the subject is received, and subject information is acquired as image data. Devices using ultrasonic echo technology.
In the case of such an apparatus, the acquired object information is information reflecting the difference in acoustic impedance of the tissue inside the object. Such an apparatus can be called a subject information acquisition apparatus. Since the image inside the subject generated by the subject information acquiring apparatus can be used for living body diagnosis, such an apparatus can also be called an ultrasonic diagnostic apparatus.

The acoustic wave referred to in the present invention is typically an ultrasonic wave and includes an elastic wave called a sound wave or an acoustic wave. The subject information acquisition apparatus of the present invention transmits an acoustic wave into the subject and receives the reflected and propagated acoustic wave by a probe having a CMUT element (element).

<First Embodiment>
(Device configuration of this embodiment)
FIG. 1A is a diagram showing a configuration of a subject information acquisition apparatus 1 according to an embodiment of the present invention.
The object information acquisition apparatus 1 includes a probe 2, an AD conversion unit 3, a reception beam shaping device 4, a signal processing unit 5, an image processing unit 6, an image display unit 7, a data memory control circuit 8, and a weighting coefficient supply circuit. 9 includes a control CPU 10 and an ultrasonic transmission unit 11.

The ultrasonic transmission unit 11 transmits ultrasonic waves to the measurement region of the subject under the control of the control CPU 10 or the like. An ultrasonic signal that is a reflected wave of the ultrasonic wave transmitted to the subject is received by the probe 2.
The received ultrasonic signal is converted into an analog electric signal by the probe 2 and further digitized by the AD converter 3. The digitized reception signal is subjected to phasing and addition processing by the reception beam shaping device 4 and is subjected to processing such as filter processing, logarithmic compression, and envelope detection by the signal processing unit 5. The signal processing unit performs appropriate processing according to the nature of the signal to be handled. Furthermore, the output data of the signal processing unit is input to the image processing unit 6 and subjected to a plurality of processes necessary for image generation, and then becomes image data. The image display unit 7 displays an ultrasonic image according to the image data generated by the image processing unit 6. The control CPU 10 supplies data and control signals necessary for controlling each block.

  The data memory control circuits 8-1 to 8 -N process the delay data of the reception signal, and perform reception data writing or reading control of the data memory in the reception beam shaping device 4. Note that N indicates the number of data memories existing in the reception beam shaping apparatus 4. The weighting coefficient supply circuits 9-1 to 9-N process weighting data for apodization and supply weighting coefficients to the multipliers in the reception beam shaping apparatus 4. N indicates the number of apodization multipliers present in the reception beam forming apparatus 4.

(Conventional device configuration)
FIG. 1B is a diagram showing a configuration of an ultrasonic diagnostic apparatus using a CMUT in a conventional example.
The probe 2 includes CMUT units 12-1 to 12 -K each including a CMUT element 21, switches 22, 23 and 24, and a preamplifier 25. The ultrasonic transmitter 11 includes transmission waveform output pulsars 26-1 to 26 -M and a waveform output controller 30. The AD conversion unit 3 includes AD conversion units 36-1 to 36 -N. The AD conversion unit 36 includes an AD converter 27 and a protection circuit 28.

  In the conventional example, transmission / reception of ultrasonic waves using CMUT is performed as follows. At the time of ultrasonic transmission, the switch 23 in the probe 2 is turned on and the switches 22 and 24 are turned off. In accordance with the control content supplied from the control CPU 10, the waveform output control unit 30 inputs the waveform data to the pulsar 26 at a desired timing. According to the waveform data, the transmission voltage output from the pulsar 26 is input to the CMUT element 21, and the ultrasonic wave is transmitted to the subject. This transmission voltage corresponds to the transmission pulse of the present invention.

On the other hand, when receiving ultrasonic waves, the switch 23 in the probe 2 is turned off, and the switches 22 and 24 are turned on. The ultrasonic signal received by the CMUT element 21 is IV converted by the preamplifier 25 and input to the AD conversion unit 3. The reception data digitized by the AD conversion unit 3 is transferred to the reception beam shaping device 4, subjected to signal processing operations such as phasing addition, and becomes ultrasonic image data. In the probe 2, the quantity K of the CMUT element 21, the quantity M of the pulsar 26 in the ultrasonic transmission unit 11, and the AD converter 27 in the AD conversion unit 3.
The quantity N may be different. The connection state is appropriately changed by the connection changeover switch 29 so that transmission and reception of ultrasonic waves are appropriately performed. As described above, in the conventional example, ultrasonic transmission / reception is performed by the same CMUT element 21.

However, in a CMUT element, transmission characteristics and reception characteristics are generally different for each CMUT element due to variations in capacitance and the like caused by semiconductor processes. Further, when a transmission waveform is output, a high voltage of several tens of volts is applied to the CMUT element 21, so that the transmission characteristics and reception characteristics in the CMUT element 21 change with time.
If no countermeasure is taken against such variations in transmission characteristics / reception characteristics and changes with time, there is a concern that the image quality of the acquired ultrasonic image may be deteriorated. Therefore, it is necessary to correct variations in transmission characteristics and reception characteristics of CMUT elements and changes with time.

(Composition of CMUT element)
FIG. 7 is a diagram for specifically explaining the configuration and driving method of a general CMUT. CMUT is a capacitive transducer.
FIG. 7 is a schematic view of the cross section of the CMUT element and the DC voltage applying means 105 and the current-voltage converting means 102. In the capacitive CMUT element, a lower electrode 505 is formed on a substrate 506, and an upper electrode 502 is disposed with the lower electrode 505 and a gap 504 (usually several tens to 900 nm) in between. In this embodiment, the upper electrode 502 is formed on the vibration film 501, and the vibration film 501 is supported by a support portion 503 formed on the substrate 506. In the present invention, the minimum unit that vibrates is called a cell, with the two electrodes opposed to each other with the gap 504 sandwiched between the vibrating membrane 501 in this way. A configuration in which a plurality of cells are electrically connected in parallel is referred to as an element. Here, one element is formed by two cells, but one element may be formed by one cell, or a plurality of cells may be connected in a two-dimensional array. Further, an arbitrary number of elements can be provided, and they may be arranged in a two-dimensional array. CMUT, which is an electromechanical conversion device, usually has about 100 to 3000 cells as one element (one pixel), and 200 to 4000 elements are two-dimensionally arranged. CMUT itself is about 1 to 10 cm in size. It is.

  As the upper electrode, at least one of a metal selected from Al, Cr, Ti, Au, Pt, Cu, Ag, W, Mo, Ta, and Ni, and an alloy selected from AlSi, AlCu, AlTi, MoW, and AlCr. You can choose a seed to use. Also, the upper electrode can be provided in at least one of the upper surface, the back surface, and the inside of the vibration film, or when the vibration film is formed of a conductor or semiconductor, the vibration film itself can also serve as the upper electrode. is there. Further, as the lower electrode used in the present invention, the same metal as that of the upper electrode can be used. When the substrate uses a semiconductor substrate such as silicon, the substrate may also serve as the lower electrode.

  All of the plurality of upper electrodes 502 are electrically connected, and they are connected to the DC voltage applying means 105. The DC voltage applying unit 105 applies a predetermined DC voltage uniformly to the upper electrode 502 so that a desired potential difference is generated between the DC voltage applying unit 105 and the lower electrode 505. When an acoustic wave is input to the vibration film 501, the vibration film 501 vibrates in accordance with the magnitude of the acoustic wave. In the lower electrode 505, electrostatic induction occurs due to the vibration of the vibrating membrane 501, and a minute current is generated. The current-voltage conversion means 102 connected to the lower electrode 505 for each element (here, two cells) converts the current value into a voltage value, and acquires the acoustic wave reception signal as a voltage value. Can be taken out every time. The upper electrode 502 may be electrically separated for each element, the current / voltage converting means 102 may be connected to the upper electrode 502, the lower electrode 505 may be electrically common to all elements, and the DC voltage applying means 105 may be connected to the lower electrode 505. It is possible to configure the device. Further, both the upper electrode 502 and the lower electrode 505 may be electrically separated for each element.

(Detailed apparatus configuration of this embodiment)
FIG. 2A is a diagram showing the probe 2, the ultrasonic transmitter 11, and the AD converter 3 according to the first embodiment of the present invention.
The probe 2 is composed of K CMUT units 35. Further, the CMUT unit 35 includes a CMUT element 21, switches 22, 23, 24, 33, a preamplifier 25, and a decoupling capacitor 34.
The ultrasonic transmission unit 11 includes pulsers 26-1 to M for transmitting waveform output, a waveform output control unit 30, and connection changeover switches 31-1 to 31-M. The AD conversion unit 3 includes AD conversion units 36-1 to 36 -N. The AD conversion unit 36 includes an AD converter 27 and a protection circuit 28.

  FIG. 2B is a diagram illustrating a configuration of the waveform output control unit 30 according to the first embodiment of the present invention. The waveform output control unit 30 includes waveform memories 50-1 to 50-M for storing waveform data to be supplied to the pulsers 26-1 to M, writing waveform data to the waveform memories 50-1 to 50-M, and waveform memories 50-1 to M. It comprises a waveform memory control circuit 51 for controlling the waveform data output from.

FIG. 2C is a diagram showing the reception beam shaping device 4 and its peripheral circuits in the first embodiment of the present invention. Here, in the Nch reception beam shaping apparatus 4, a configuration for performing phasing addition is taken as an example.
The reception beam shaping apparatus 4 includes data memories 14-1 to 14 -N, apodization multipliers 15-1 to 15 -N, and an adder circuit 13.

(Transmission and reception of ultrasonic waves)
Next, the operation of the first exemplary embodiment of the present invention will be described.
At the time of ultrasonic transmission, the switch 23 in the CMUT unit 35 is turned on, and the switches 22, 24, and 33 are turned off. The connection changeover switches 31-1 to 31 -M connect the pulsers 26-1 to 26 -M to the connection changeover switch 29.
In accordance with the control content supplied from the control CPU 10, the waveform output control unit 30 inputs the waveform data to the pulsers 26-1 to 26-M at a desired timing. According to the waveform data, the transmission voltage output from the pulsers 26-1 to 26-M is input to the CMUT element 21 via the connection changeover switch 29 and the switch 23, and an ultrasonic wave is transmitted to the subject.

On the other hand, when receiving ultrasonic waves, the switches 22 and 24 in the CMUT unit 35 are turned ON, and the switches 23 and 33 are turned OFF. In addition, the connection changeover switches 31-1 to 31 -M may remain connected to the pulsars 26-1 to 26 -M toward the connection changeover switch 29.
The ultrasonic signal received by the CMUT element 21 is subjected to current-voltage conversion by the preamplifier 25 and input to the AD conversion unit 3 via the connection changeover switch 29. Since the output of the CMUT element 21 in ultrasonic reception is a very small current, it is desirable to provide a preamplifier 25 for converting a change in a very small current into a voltage as a component.

The reception data digitized by the AD conversion unit 3 is transferred to the reception beam shaping device 4, subjected to signal processing operations such as phasing addition, and becomes ultrasonic image data. In the receiving beam shaping apparatus 4, phasing addition is not necessarily performed. The data stored in the data memories 14-1 to 14-N may be directly processed by the host CPU as it is to generate image data (not shown).
When the number K of the CMUT units 35 is different from the number M of the pulsars 26 in the ultrasonic transmission unit 11 and the number N of the AD converters 27 in the AD conversion unit 3, the connection switching is performed so that transmission and reception of ultrasonic waves are appropriately performed. The connection state is appropriately changed by the switch 29.

(Reception characteristics variation detection)
As described above, the CMUT element 21 has reception characteristic variations due to capacitance variations and the like. If the characteristics of the K CMUT elements 21 vary, reception beam forming is not performed normally, and the image quality of the acquired ultrasonic image may be deteriorated.
Therefore, in the first embodiment of the present invention, the reception characteristic variation of the CMUT element 21 is detected and corrected. The process is as follows.

When detecting and correcting the reception characteristic variation of the CMUT element 21, the switches 22, 24, and 33 are turned on and the switch 23 is turned off. Then, the outputs of the pulsers 26-1 to 26 -M are connected to the connection changeover switch 32 by the connection changeover switch 31.
The connection changeover switch 29, the connection changeover switch 32, and the switch 33 select one that performs reception characteristic variation detection from among the K CMUT elements 21, and are connected to the ultrasonic transmission unit 11 and the AD conversion unit 3. .

  In accordance with the control contents supplied from the control CPU 10, the waveform memory control circuit 51 writes the waveform data for evaluating reception characteristic variations in the waveform memories 50-1 to 50-M. And according to control of the waveform memory control circuit 51, the waveform memories 50-1 to 50-M output waveform data to the pulsers 26-1 to 26-M at a desired timing. According to the waveform data, the transmission voltage output from the pulsers 26-1 to 26 -M is applied to the CMUT element 21 via the connection changeover switch 32 and the switch 33. The pulse output at this time corresponds to the characteristic acquisition pulse of the present invention.

The waveform data for detecting reception characteristic variation may be different from the waveform for normal ultrasonic transmission. It is desirable that a waveform that can confirm the impulse response of the CMUT element 21 can be input. For example, when transmitting and receiving an ultrasonic wave of about 10 MHz from the ultrasonic transmission dedicated CMUT element 21, it is desirable to be able to input a pulse having a pulse width narrower than 50 ns.
Further, not only the waveform data but also the output voltages of the pulsers 26-1 to 26-M can be changed for detection of reception characteristic variation. The output voltage of the pulsar may be set to an appropriate voltage depending on the situation in the range of several volts to several tens of volts.
The response signal of the CMUT element 21 with respect to the waveform for detecting characteristic variation is current-voltage converted by the preamplifier 25 and input to the AD conversion unit 3 via the connection changeover switch 29. The response signal of the CMUT element 21 digitized by the AD conversion unit 3 is transferred to the reception beam shaping device 4. The preamplifier at this time corresponds to the first conversion means of the present invention.

The reception signal digitized by the AD conversion unit 3 is first taken into the data memory 14. The response signal data of the CMUT element 21 stored in the data memories 14-1 to 14-N is transferred to the waveform data analysis unit. The waveform data analysis unit corresponds to a control signal analysis unit in the control CPU 10, another upper CPU (not shown), or the subject information acquisition apparatus 1 (not shown).
The waveform data analysis unit analyzes the spectrum and intensity of the output data of each CMUT element 21 and evaluates the characteristics of the CMUT element 21. It can be said that the control CPU or the like when performing such processing corresponds to the characteristic acquisition means of the present invention. The control CPU or the like simultaneously corresponds to the control means of the present invention.

When the above operation is completed, by switching the connection changeover switch 29, the connection changeover switch 32, and the switch 33, the unevaluated CMUT element 21 is selected and the characteristics are evaluated.

(Correction of reception characteristics)
When the characteristic evaluation of all desired CMUT elements 21 is completed, the reception characteristic variation of the CMUT elements 21 is corrected according to the characteristic of each CMUT element 21. The reception characteristic variation is corrected by correcting the reception parameter. The control CPU 10, another upper CPU (not shown), or the portion corresponding to the response signal analysis unit in the subject information acquisition apparatus 1 (not shown) corrects the reception parameter. Items to be corrected are a resistance value and a capacitance value that affect the frequency characteristics of the preamplifier 25, a drive current value of the preamplifier 25, a TGC curve input to a variable gain amplifier (not shown), and an apodization used in the phasing addition circuit. It is a weighting factor. The preamplifier at this time corresponds to the second conversion means of the present invention.
Through the above process, the reception characteristic variation of the CMUT element 21 is corrected.

(Merit of the invention)
As in the embodiment of the present invention, there are two merits of a method of acquiring response data by inputting a pulse for confirming an impulse response to all of the CMUT elements 21, that is, a reception characteristic variation detection waveform.
The first is that characteristics of a wide frequency band can be evaluated by analyzing the impulse response of the CMUT element 21. In order to evaluate the characteristics of the CMUT element 21, a method of inputting a plurality of waveforms having different frequency characteristics and evaluating the characteristics of the CMUT element 21 with respect to each waveform is conceivable, but is more complicated than the embodiment of the present invention. A procedure is required.
Second, since the pulser used for ultrasonic transmission in the ultrasonic diagnostic apparatus can be used for inputting the reception characteristic variation detection waveform, the characteristic of the CMUT element 21 can be evaluated without increasing the circuit scale. It is.

(Processing flow)
FIG. 3 is a flowchart of reception characteristic variation detection and correction of the CMUT element 21.
At S0, a reception characteristic variation detection and reception parameter correction mode starts.
In S1, based on the control of the control CPU 10, the waveform memory control circuit 51 of the waveform output control unit 30 inputs waveform data for detecting reception characteristic variations to the waveform memories 50-1 to 50-M. In addition, the output voltages of the pulsers 26-1 to 26-M are changed as necessary.

Subsequently, the process proceeds to each element.
In S2, the connection changeover switches 29, 31, 32, and 33 select one or a plurality of CMUT elements 21 that perform reception characteristic variation detection from the K CMUT elements 21, and the ultrasonic transmission unit 11, AD Connect to the converter 3.
In S3, the waveform memory control circuit 51 of the waveform output control unit 30 detects the reception characteristic variation from the waveform memory 50 connected to the CMUT element 21 that detects the reception characteristic variation among the waveform memories 50-1 to 50-M. Outputs waveform data. The pulser 26 driven by the waveform data outputs a pulse to the selected CMUT element 21, and the response signal is input to the AD conversion unit 3 via the switch 22, the preamplifier 25 and the switch 24. The AD conversion unit 3 converts the response signal into digital data and transfers it to the data memory 14 in the reception beam shaping device 4.

In S <b> 4, the data memory 14 transfers the response signal data to the control CPU 10, another upper CPU (not shown), or the response signal analysis unit in the subject information acquisition apparatus 1 (not shown).
If the reception characteristic variation detection of all the desired CMUT elements 21 has not been completed in S5, the process returns to S2 to select an unselected CMUT element 21, and the processes of S3 and S4 are executed. In this way, the processes of S2 to S5 are repeated until the detection of the reception characteristic variation of all the desired CMUT elements 21 is completed. When the reception characteristic variation detection of all the elements in the desired CMUT element 21 is completed, the process proceeds to S6.

  In S <b> 6, the control signal 10 corresponding to all desired CMUT elements 21 is analyzed by the control CPU 10, another host CPU (not shown), or the response signal analysis unit in the subject information acquisition apparatus 1 (not shown). For example, in S <b> 6, information on the strength of the response signal input from the CMUT element 21 to the AD conversion unit 3 via the preamplifier 25 is obtained by measuring the amplitude of the response signal. Further, the frequency characteristics of the response signal input from the CMUT element 21 to the AD conversion unit 3 via the preamplifier 25 are obtained by performing FFT analysis (fast Fourier transform) on the response signal.

In S7, the reception parameter is corrected so that the reception characteristic variation of the desired CMUT element 21 is corrected based on the analysis result in S6. The correction of the reception parameter may be performed by any of the control CPU 10, another upper CPU (not shown), or the response signal analysis unit in the subject information acquisition apparatus 1 (not shown). The reception parameters to be corrected are a resistance value and a capacitance value that affect the frequency characteristics of the preamplifier 25, a driving current value of the preamplifier 25, a TGC curve input to a variable gain amplifier (not shown), and an apodization used in the phasing addition circuit. Is a weighting coefficient.
For example, if the intensity of the response signal deviates from the intensity assumed by the user in S6, the TGC curve input to the variable gain amplifier corresponding to the CMUT element 21 whose intensity is deviated is adjusted in S7. Thereby, the amplification factor of the response signal is changed, and the intensity can be adjusted to a value assumed by the user. Alternatively, it is possible to eliminate the variation in the signal intensity output from the preamplifier 25 by adjusting the weighting coefficient during the phasing addition.
As a result of the FFT analysis in S6, the frequency characteristic of the response signal input to the AD conversion unit 3 from a certain CMUT element 21 via the corresponding preamplifier 25 may be different from the frequency characteristic expected by the user. To do. In this case, the frequency characteristic of the response signal input to the AD conversion unit 3 can be changed to a desired characteristic by adjusting the capacitance value and the resistance value connected to the corresponding preamplifier 25 in S7. For example, the center frequency of the response signal output from the preamplifier 25 can be increased by decreasing the capacitance value connected to the preamplifier 25 or increasing the resistance value. Conversely, by increasing the capacitance value connected to the preamplifier 25 or decreasing the resistance value, the center frequency of the response signal output from the preamplifier 25 can be lowered. Furthermore, it is possible to extract a signal having a desired frequency by changing the filter characteristics of an analog filter or a digital filter installed at a stage subsequent to the preamplifier 25.
However, the response signal analysis items and correction means in S6 and S7 are not limited to this.

When the reception parameter correction is completed, the reception characteristic variation detection and correction mode ends in S8.
As a result of detection and correction of reception characteristic variation, reception characteristic variation of a desired CMUT element 21 can be suppressed, and reception beam forming can be performed in a good state.

In FIG. 2A, a bias voltage (hereinafter referred to as a bias voltage) terminal, a decoupling capacitor 34, and a switch 33 are arranged one by one for one CMUT unit 35. However, such a configuration is not necessarily required. Absent. All CMUT units 3
5-1 to K may share one bias voltage terminal, decoupling capacitor 34, and switch 33 (not shown). In that case, a circuit configuration in which one of the pulsers 26-1 to 26-M is connected to the switch 33 may be employed (not shown).

  As described above, according to the first embodiment of the present invention, it is possible to correct the reception characteristic variation of the CMUT element 21 without greatly increasing the circuit scale and to improve the reception beam forming state without using a complicated method. You can do it. As a result, the image quality of the acquired ultrasonic image can be improved.

<Second Embodiment>
FIG. 4 is a diagram showing the probe 2, the ultrasonic transmission unit 11, and the AD conversion unit 3 according to the second embodiment of the present invention.
The second embodiment of the present invention is different from the first embodiment of the present invention in that the reception characteristic evaluation pulser 26- (M + 1) is connected to the switch 33.
In the second embodiment of the present invention, a reception characteristic variation evaluation waveform is applied to the CMUT element 21 using the pulser 26- (M + 1) in the reception characteristic variation detection and correction mode.
Other apparatus configurations and operations are the same as those in the first embodiment of the present invention, and thus will not be described in detail.

  In FIG. 4, one bias voltage terminal, one decoupling capacitor 34, and one switch 33 are arranged for each CMUT unit 35. However, such a configuration is not necessarily required. All the CMUT units 35-1 to 35-K may share one bias voltage terminal, the decoupling capacitor 34, and the switch 33 (not shown). In that case, the circuit configuration is such that the pulser 26- (M + 1) is connected to one switch 33 (not shown).

  According to the second embodiment of the present invention, it is possible to correct the reception characteristic variation of the CMUT element 21 without greatly increasing the circuit scale and to perform reception beam forming in a good state without using a complicated method. As a result, the image quality of the acquired ultrasonic image can be improved.

<Third Embodiment>
(Detailed apparatus configuration of this embodiment)
FIG. 5A is a diagram showing a probe 2, an ultrasonic transmitter 11, and an AD converter 3 according to a third embodiment of the present invention.
In the third embodiment of the present invention, a switch 37, a selection switch 38, and a transmission characteristic evaluation preamplifier 40 are added to the probe 2, and an AD converter 43 for transmission characteristic evaluation is added to the AD conversion unit 3. This is different from the first embodiment of the present invention.
In the third embodiment of the present invention, the reception characteristic variation of the CMUT element 21 can be corrected as in the first embodiment. In addition, the transmission characteristic variation evaluation and correction of the CMUT element 21 can be performed. . The operation will be described below.

(Transmission and reception of ultrasonic waves)
At the time of ultrasonic transmission, the switch 23 in the CMUT unit 60 is turned on, and the switches 22, 24, 33, and 37 are turned off. The connection changeover switches 31-1 to 31 -M connect the pulsers 26-1 to 26 -M to the connection changeover switch 29.
In accordance with the control content supplied from the control CPU 10, the waveform output control unit 30 inputs the waveform data to the pulsers 26-1 to 26-M at a desired timing. According to the waveform data, the transmission voltage output from the pulsers 26-1 to 26-M passes through the connection changeover switch 29 and the switch 23, and
Input to the CMUT element 21. As a result, ultrasonic waves are transmitted to the subject.

  On the other hand, when receiving ultrasonic waves, the switches 22 and 24 in the CMUT unit 60 are turned on, and the switches 23, 33, and 37 are turned off. The ultrasonic signal received by the CMUT element 21 is current-voltage converted by the preamplifier 25 and input to the AD converter 3. The reception data digitized by the AD conversion unit 3 is transferred to the reception beam shaping device 4, subjected to signal processing operations such as phasing addition, and becomes ultrasonic image data.

(Reception characteristics variation detection)
The CMUT element 21 has transmission characteristic variations due to capacitance variations and the like. When the transmission characteristics of the K CMUT elements 21 vary, the ultrasonic transmission beam formation is not improved, and the state of the received ultrasonic signal is adversely affected. As a result, the image quality of the acquired ultrasonic image is increased. May decrease. Therefore, it is necessary to detect and correct the transmission characteristic variation of the CMUT element 21 in order to prevent deterioration of the image quality of the ultrasonic image.
When detecting and correcting the transmission characteristic variation of the CMUT element 21, the switches 33 and 37 are turned on, and the switches 22, 23, and 24 are turned off. Then, the outputs of the pulsers 26-1 to 26 -M are connected to the connection changeover switch 32 by the connection changeover switch 31.

In accordance with the control contents supplied from the control CPU 10, the waveform output control unit 30 inputs waveform data for detecting transmission characteristic variations to the pulsers 26-1 to 26-M at a desired timing.
The waveform data for detecting the transmission characteristic variation may be different from the waveform for normal ultrasonic transmission. It is desirable that a pulse that can confirm the impulse response of the CMUT element 21 can be input. For example, when transmitting an ultrasonic wave of about 10 MHz from the ultrasonic transmission dedicated CMUT element 21, it is desirable that a pulse having a pulse width narrower than 50 ns can be input.
In addition, not only the waveform data but also the output voltages of the pulsers 26-1 to 26-M can be changed for detecting transmission characteristic variations. The output voltage of the pulsar may be set to an appropriate voltage depending on the situation in the range of several volts to several tens of volts.

  The selection switch 38 selects the K CMUT elements 21 that are to be subjected to transmission characteristic variation detection. The response signal of the CMUT element 21 with respect to the waveform for detecting the transmission characteristic variation is input to the transmission characteristic evaluation preamplifier 40 and subjected to IV conversion. The output of the transmission characteristic evaluation preamplifier 40 is input to the transmission characteristic evaluation AD converter 43, and the output of the transmission characteristic evaluation AD converter 43 is input to the reception beam shaping apparatus 4.

  It should be noted that one transmission characteristic evaluation preamplifier 40 is preferably arranged for all CMUT elements 21. In general, the transmission characteristic evaluation preamplifier 40 also has characteristic variations. Therefore, when a plurality of transmission characteristic evaluation preamplifiers 40 are provided, the characteristic evaluation contents of the CMUT element 21 may vary. If a method for evaluating all the CMUT elements 21 with one transmission characteristic evaluation preamplifier 40 as in the third embodiment of the present invention is used, it is possible to eliminate variations in the characteristic evaluation contents of the CMUT elements 21. Become. Further, since only one transmission characteristic evaluation preamplifier 40 is required, there is an advantage that the CMUT element 21 can be evaluated without increasing the circuit scale.

FIG. 5B is a diagram showing the reception beam shaping device 4 and its peripheral circuits in the third embodiment of the present invention. Here, in the Nch reception beam shaping apparatus 4, a configuration for performing phasing addition is taken as an example.
The reception beam shaping apparatus 4 includes data memories 14-1 to 14-(N + 1), apodization multipliers 15-1 to 15 -N, and an adder circuit 13. The difference from the first and second embodiments is that a data memory 14- (N + 1) is added.
In the receiving beam shaping apparatus 4, phasing addition is not necessarily performed. The data stored in the data memories 14-1 to 14-N may be directly processed by the host CPU as it is to generate image data (not shown).
The data memory 14- (N + 1) is a memory for detecting transmission characteristic variations. The output of the AD converter 43 for transmission characteristic evaluation is input to the data memory 14- (N + 1). Data input to the data memory 14-(N + 1) is a response signal of the CMUT element 21 with respect to the transmission characteristic variation detection waveform.

The K switch CMUT elements 21 are sequentially selected one by one by the selection switch 31, the connection changeover switch 32, the switches 33 and 37, and the selection switch 38, and the above-described transmission characteristic variation detection process is repeated K times. In this way, response signal data to the transmission characteristic variation detection waveform is acquired for all K CMUT elements 21. The acquired response signal data is analyzed for spectrum, intensity, and the like by the waveform data analysis unit, and the characteristics of the CMUT element 21 are evaluated.
The waveform data analysis unit corresponds to a control signal analysis unit in the control CPU 10, another upper CPU (not shown), or the subject information acquisition apparatus 1 (not shown).

(Reception characteristics correction)
The waveform output control unit 30 corrects the transmission waveform data corresponding to each CMUT element 21 so that the transmission characteristics of all the CMUT elements 21 are matched in accordance with the characteristic analysis result of the CMUT elements 21. That is, the difference in transmission characteristics between CMUT elements is reduced. The items to be corrected are the wavelength of the transmission wave, the wave number, the duty ratio, and the pulsar drive current and output voltage. The corrected transmission waveform data is stored in the waveform memories 50-1 to 50-M, and is used for ultrasonic transmission at the time of ultrasonic image capturing.

(Processing flow)
FIG. 3 can also be a flowchart for detecting and correcting variations in transmission characteristics of the CMUT element 21.
At S0, transmission characteristic variation detection and transmission waveform data correction modes start.
In S1, based on the control of the control CPU 10, the waveform memory control circuit 51 of the waveform output control unit 30 inputs waveform data for transmission characteristic variation detection to the waveform memories 50-1 to 50-M. In addition, the output voltages of the pulsers 26-1 to 26-M are changed as necessary.

Subsequently, the process proceeds to each element.
In S2, the selection switch 31, the connection changeover switch 32, the switches 33 and 37, and the selection switch 38 select one CMUT element 21 that performs reception characteristic variation detection from the K CMUT elements 21, and the AD conversion unit Connect to 3.
In S3, the waveform memory control circuit 51 of the waveform output control unit 30 detects the transmission characteristic variation from the waveform memory 50 connected to the CMUT element 21 that detects the transmission characteristic variation among the waveform memories 50-1 to 50-M. Outputs waveform data. The pulser 26 driven by the waveform data outputs a pulse to the selected CMUT element 21, and the response signal is input to the AD conversion unit 3 via the switch 37, the selection switch 38 and the preamplifier 40. The AD conversion unit 3 converts the response signal into digital data and transfers it to the data memory 14 in the reception beam shaping device 4.

In S <b> 4, the data memory 14 transfers the response signal data to the control CPU 10, another upper CPU (not shown), or the response signal analysis unit in the subject information acquisition apparatus 1 (not shown).
If the transmission characteristic variation detection of all desired CMUT elements 21 has not been completed in S5, the process returns to S2, selects an unselected CMUT element 21, and executes the processes of S3 and S4. In this manner, the processes of S2 to S5 are repeated until transmission characteristic variation detection of all the desired CMUT elements 21 is completed. When the transmission characteristic variation detection of all the desired CMUT elements 21 is completed, the process proceeds to S6.

  In S <b> 6, the control signal 10 corresponding to all desired CMUT elements 21 is analyzed by the control CPU 10, another host CPU (not shown), or the response signal analysis unit in the subject information acquisition apparatus 1 (not shown). For example, in S6, information on the strength of the response signal is obtained by measuring the amplitude of the response signal. Further, the frequency characteristic of the CMUT element 21 is obtained by performing FFT analysis on the response signal.

In S7, the transmission waveform data is corrected so that the transmission characteristic variation of the desired CMUT element 21 is corrected based on the analysis result in S6. The correction of the transmission waveform data may be performed by either the control CPU 10, another upper CPU (not shown), or the response signal analysis unit in the subject information acquisition apparatus 1 (not shown). The transmission waveform data to be corrected is the wavelength, wave number, duty ratio, pulser drive current and output voltage of the transmission wave.
For example, if there is a deviation as a result of comparing the intensity of the response signal with a predetermined value that is assumed by the user in S6, the intensity of the response signal is adjusted to the value assumed by the user by adjusting the pulsar output voltage in S7. Combine with. Alternatively, processing such as changing the wave number of the transmission wave is performed.
If the frequency characteristics of the plurality of CMUT elements 21 vary as a result of the FFT analysis in S6, the frequency band common to as many CMUT elements 21 as possible is specified among the plurality of CMUT elements 21 in S7. . Then, processing is performed to minimize variations in the transmission characteristics of a plurality of CMUT elements 21 by adjusting the wavelength and duty ratio of the transmission waveform data so that the frequency of the transmission wave matches the frequency band. Is also possible.
However, the response signal analysis items and correction means in S6 and S7 are not limited to this.

When the correction of the transmission waveform data is completed, the transmission characteristic variation detection and correction mode ends in S8.
As a result of transmission characteristic variation detection and correction, transmission characteristic variation of a desired CMUT element 21 is suppressed, and a transmission beam can be formed in a good state.

  The analysis result of the CMUT element 21 is not necessarily fed back only to the transmission waveform data, and may be used for correction of reception parameters. The reception parameters to be corrected include a resistance value and a capacitance value that affect the frequency characteristics of the preamplifier 25, a drive current value of the preamplifier 25, a TGC curve input to a variable gain amplifier (not shown), and an apodization used in the phasing addition circuit. The weighting factor for

  In FIG. 5A, one bias voltage terminal, one decoupling capacitor 34, and one switch 33 are arranged for each CMUT unit 60. However, such a configuration is not necessarily required. All the CMUT units 60-1 to 60-K may share one bias voltage terminal, the decoupling capacitor 34, and the switch 33 (not shown). In that case, a circuit configuration in which one of the pulsers 26-1 to 26-M is connected to the switch 33 may be employed (not shown).

In FIG. 5A, the ultrasonic transmission unit 11 has the same configuration as that of the first embodiment, but it is not necessarily required to be this way. As shown in the second embodiment, a reception characteristic evaluation pulsar 26- (M + 1) may be provided and the connection changeover switch 32 may be omitted (not shown).

  Thus, according to the third embodiment of the present invention, it is possible to correct variations in transmission characteristics and reception characteristics of the CMUT element 21 without increasing the device scale and without using a complicated method. Thereby, ultrasonic transmission of the probe 2 can be performed in a good state and reception beam forming can be performed in a good state, so that the image quality of the acquired ultrasonic image can be improved.

<Fourth Embodiment>
FIG. 6 is a diagram showing the probe 2, the ultrasonic transmission unit 11, and the AD conversion unit 3 according to the fourth embodiment of the present invention.
The fourth embodiment of the present invention is different from the third embodiment of the present invention in that a transmission characteristic evaluation preamplifier 40 is connected to an AD converter 27-N via a selection switch 45.

In the fourth embodiment of the present invention, in the transmission characteristic variation detection and correction mode, the response signal is converted into digital data using the AD converter 27-N, and the data memory 14- of the reception beam shaping apparatus 4 shown in FIG. 2C is used. Forward to N.
The data memory 14 -N transfers the response signal data to the control CPU 10, another upper CPU (not shown), or the response signal analysis unit in the subject information acquisition apparatus 1 (not shown).

Other apparatus configurations and operations are the same as those of the third embodiment of the present invention, and thus will not be described in detail.
Also in the fourth embodiment of the present invention, transmission waveform data and reception parameters can be corrected in the same manner as in the third embodiment.
Note that the transmission characteristic evaluation preamplifier 40 does not necessarily have to be connected to the AD converter 27 -N among the AD converters 27-1 to 27 -N via the selection switch 45. It may be connected to any one of the AD converters 27-1 to 27 -N (not shown).

In FIG. 6, one bias voltage terminal, one decoupling capacitor 34, and one switch 33 are arranged for each CMUT unit 60, but such a configuration is not necessarily required. All the CMUT units 60-1 to 60-K may share one bias voltage terminal, the decoupling capacitor 34, and the switch 33 (not shown). In that case, a circuit configuration in which one of the pulsers 26-1 to 26-M is connected to the switch 33 may be employed (not shown).
In FIG. 6, the ultrasonic transmission unit 11 has the same configuration as that of the first embodiment, but this is not necessarily the case. As shown in the second embodiment, a reception characteristic evaluation pulsar 26- (M + 1) may be provided and the connection changeover switch 32 may be omitted (not shown).

  As described above, according to the fourth embodiment of the present invention, it is possible to correct variations in transmission characteristics and reception characteristics of the CMUT element 21 without increasing the apparatus scale and without using a complicated method. Thereby, ultrasonic transmission of the probe 2 can be performed in a good state and reception beam forming can be performed in a good state, so that the image quality of the acquired ultrasonic image can be improved.

  As mentioned above, although preferred embodiment of this invention was described, embodiment mentioned above is only a mere illustration in all the points, and does not limit the scope of the present invention.

  2: probe, 3: AD conversion unit, 4: reception beam shaping device, 5: signal processing unit, 6: image processing unit, 10: control CPU, 11: ultrasonic transmission unit

Claims (11)

An output means for outputting a transmission pulse and a characteristic acquisition pulse;
An electrostatic capacitance type including a plurality of elements that transmit an acoustic wave corresponding to the transmission pulse when the transmission pulse is input and output a current corresponding to the acoustic wave when the acoustic wave is received Transmitting / receiving means comprising a transducer;
First conversion means for converting a current output from the element into a voltage when the characteristic acquisition pulse is input to the element of the transmission / reception means;
Based on the signal output from the first conversion means, characteristic acquisition means for acquiring the reception characteristics of the elements of the transmission / reception means;
Second conversion means for converting a current output when the transmission / reception means receives a reflected wave transmitted from the transmission / reception means and reflected by a subject to a voltage;
Generating means for generating subject information inside the subject based on the output of the second conversion means;
Control means for performing control to reduce a difference for each element of the reception characteristic acquired by the characteristic acquisition means when receiving the reflected wave;
A subject information acquisition apparatus characterized by comprising: 2. The object information acquisition according to claim 1, wherein the characteristic acquisition unit acquires the reception characteristic by comparing an amplitude of a signal output from the first conversion unit with a predetermined value. apparatus. 3. The object information acquiring apparatus according to claim 2, wherein the control unit corrects the reception characteristic by changing an amplification factor of the signal output from the second conversion unit for each element. . The object information acquiring apparatus according to claim 2, wherein the control unit corrects the reception characteristic by changing a weight for each element when the generation unit generates the object information. The characteristic acquisition unit acquires the reception characteristic by performing Fourier transform on a signal output from the first conversion unit when the characteristic acquisition pulse is input to each of the plurality of elements. The object information acquiring apparatus according to claim 1, wherein: An output means for outputting a transmission pulse and a characteristic acquisition pulse under the control of the control means;
An electrostatic capacitance type including a plurality of elements that transmit an acoustic wave corresponding to the transmission pulse when the transmission pulse is input and output a current corresponding to the acoustic wave when the acoustic wave is received Transmitting / receiving means comprising a transducer;
Conversion means for converting a current output from the element into a voltage when the characteristic acquisition pulse is input to the element of the transmission / reception means;
Based on the signal output from the conversion means, characteristic acquisition means for acquiring the transmission characteristics of the elements of the transmission / reception means;
Generating means for generating subject information inside the subject based on the reflected wave received from the transmitting / receiving means after being transmitted from the transmitting / receiving means and reflected by the subject;
Have
The control means controls the output means so as to reduce a difference for each element of the transmission characteristic acquired by the characteristic acquisition means when an acoustic wave is transmitted from the transmission / reception means to the subject. Characteristic object information acquisition apparatus. The object information acquiring apparatus according to claim 6, wherein the characteristic acquisition unit acquires the transmission characteristic by comparing an amplitude of a signal output from the conversion unit with a predetermined value. The said control means adjusts the output voltage at the time of outputting a pulse from the said output means so that the amplitude of the signal output from the said conversion means may become predetermined value. Subject information acquisition apparatus. The characteristic acquisition unit acquires the transmission characteristic by performing Fourier transform on a signal output from the conversion unit when the characteristic acquisition pulse is input to each of the plurality of elements. The subject information acquisition apparatus according to claim 6. A method for controlling a subject information acquisition apparatus, comprising: a transmission / reception means comprising a capacitive transducer including a plurality of elements, wherein the subject information is acquired based on an acoustic wave received by the transmission / reception means,
A characteristic acquisition step of acquiring a reception characteristic of the element of the transmission / reception means, and an information acquisition step of acquiring subject information from the subject;
The characteristic acquisition step includes:
Outputting a characteristic acquisition pulse to the element of the transceiver means;
Converting the current output from the element into a voltage when the characteristic acquisition pulse is input to the element of the transmitting and receiving means;
Obtaining reception characteristics for each element of the transmission / reception means based on the signal converted to the voltage,
The information acquisition step includes
The transmitting / receiving means receiving a transmission pulse and transmitting an acoustic wave corresponding to the pulse;
The transmitting / receiving means receiving a reflected wave reflected by the subject from the acoustic wave transmitted from the transmitting / receiving means;
The signal based on the current output from the element when the reflected wave is received is processed to reduce the difference in the reception characteristics for each element, and object information inside the object is generated. And a method for controlling the subject information acquiring apparatus. A method for controlling a subject information acquisition apparatus, comprising: a transmission / reception means comprising a capacitive transducer including a plurality of elements, wherein the subject information is acquired based on an acoustic wave received by the transmission / reception means,
A characteristic acquisition step of acquiring a transmission characteristic of an element of the transmission / reception means, and an information acquisition step of acquiring subject information from the subject,
The characteristic acquisition step includes:
Outputting a characteristic acquisition pulse to the element;
Converting the current output when the characteristic acquisition pulse is input to the element of the transmission / reception means into a voltage;
Obtaining a transmission characteristic for each element of the transmission / reception means based on the signal converted into the voltage,
The information acquisition step includes
Outputting a transmission pulse so as to reduce the difference between the elements of the transmission characteristics during transmission of the acoustic wave to the subject; and
The transmitting / receiving means transmitting an acoustic wave corresponding to the transmission pulse;
The transmitting / receiving means receiving a reflected wave reflected by the subject from the acoustic wave transmitted from the transmitting / receiving means;
And a step of generating subject information inside the subject based on the reflected wave received by the transmitting / receiving means.

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