JPH11226010A - Ultrasonic wave transducer driving method and device, and ultrasonic image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide ultrasonic wave transducer driving method and device for transmitting bipolar ultrasonic waves by unipolar drive and an ultrasonic image pickup device provided with such an ultrasonic wave transducer driving device. SOLUTION: The waveform of driving signals is provided with a level elevation part 500 where a signal level is gently elevated from a 0 level to a first level, a level change part 502 where it is changed between a second level and a third level which are respectively the levels above and below the first level with the first level at a center at a high speed and a level lowering part 504 where it is gently lowered from the first level to the 0 level. By AC signals 502 superimposed on DC bias 500 and 504, an ultrasonic wave transducer is driven and the ultrasonic wave transducer is made to perform bipolar vibration.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer driving method and apparatus and an ultrasonic imaging apparatus, and more particularly to an ultrasonic transducer driving method and apparatus for driving an ultrasonic transducer by a unipolar driving signal. Also, the present invention relates to an ultrasonic imaging apparatus provided with such an ultrasonic transducer driving device.

[0002]

2. Description of the Related Art An ultrasonic imaging apparatus transmits an ultrasonic wave to a subject, and forms an image of the inside of the subject based on an echo thereof. An ultrasonic transducer is used for transmitting ultrasonic waves. The ultrasonic transducer is driven by a pulse voltage to vibrate and emit ultrasonic waves.

[0003] There are two types of driving of the ultrasonic transducer by the pulse voltage: unipolar driving and bipolar driving. Unipolar driving is performed by a pulse voltage having a positive or negative polarity. Bipolar driving is performed by an alternating pulse in which the polarity of the pulse voltage alternates between positive and negative, that is, an AC pulse.

[0004]

The unipolar driving has the advantage that the driving device can be simplified because the polarity of the pulse voltage can be either positive or negative. Has a direct-current component and low-frequency components in the vicinity of the direct-current component, and there is a problem that echoes to these direct-current and low-frequency ultrasonic waves degrade image quality.

On the other hand, according to the bipolar driving, the polarity of the pulse voltage alternately changes to positive and negative, so that the frequency spectrum of the transmitted ultrasonic wave has a DC component and a low frequency component near the DC component. Although no component is contained and the above-described problem does not occur, there is a problem that the configuration of the driving device is complicated because a bipolar pulse voltage is generated.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object of the present invention is to provide an ultrasonic transducer driving method and apparatus for transmitting bipolar ultrasonic waves by unipolar driving, and to provide such a method. It is an object of the present invention to realize an ultrasonic imaging apparatus provided with a simple ultrasonic transducer driving device.

[0007]

(1) A first invention for solving the problem is an ultrasonic transducer driving method for driving an ultrasonic transducer by a unipolar driving signal, wherein the unipolar driving method is used. A method of driving an ultrasonic transducer, comprising: changing a level of a signal between a second level which is relatively high and a third level which is relatively low with reference to the first level. It is.

(2) A second invention for solving the problem is an ultrasonic transducer driving device for driving an ultrasonic transducer by a unipolar driving signal, wherein the ultrasonic transducer driving device is relatively high with respect to a first level. A driving means for driving the ultrasonic transducer by a unipolar driving signal whose level alternates between a second level of the level and a third level of a relatively low level. It is an ultrasonic transducer driving device.

(3) According to a third aspect of the present invention, there is provided an ultrasonic transducer for transmitting an ultrasonic wave by driving an ultrasonic transducer with a unipolar drive signal and generating an image based on an echo reception signal. An imaging apparatus, comprising: a driving signal having a unipolar driving level whose level alternates between a second level relatively high and a third level relatively low with respect to the first level. An ultrasonic imaging apparatus comprising: driving means for driving an acoustic transducer.

In any one of the first to third inventions, the level of the unipolar drive signal is changed from 0 level to the first level at a relatively slow change speed,
Next, the level of the drive signal is alternated between the second level and the third level at a relatively fast changing speed,
Next, it is preferable to change the level of the drive signal from the first level to the 0 level at a relatively slow rate of change from the viewpoint of performing echo reception by the ultrasonic transducer when the level of the drive signal is 0. .

In this case, it is preferable to generate the drive signal based on the digital data stored in the waveform memory in order to obtain an effective drive signal. (Operation) In the present invention, the ultrasonic transducer is driven by the AC signal superimposed on the DC bias to cause the ultrasonic transducer to perform bipolar vibration.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. Note that the present invention is not limited to the embodiment. FIG. 1 shows a block diagram of the ultrasonic transmitting / receiving apparatus. This device is an example of an embodiment of the present invention. An example of an embodiment relating to the device of the present invention is shown by the configuration of the present device. An example of an embodiment relating to the method of the present invention is shown by the operation of the present apparatus.

As shown in FIG. 1, the apparatus has a waveform memory (m
emory) 300. The waveform memory 300 stores a waveform of a drive signal for driving the ultrasonic transducer as digital data. The details of the drive signal will be described later.

The reading of the waveform memory 300 is controlled by a controller 302, and the read data is converted into an analog signal by a digital-to-analog (D / A) converter 304, and the read data is converted to a linear power amplifier.
plifier) 306. The controller 302 also controls a strobe of the linear power amplifier 306. The control of the strobe will be described later.

The linear power amplifier 306 has a common (c
ommon) to a unipolar DC power supply voltage + HV (for example, +
60V). A capacitor 308 is connected between the supply line (line) of the DC power supply voltage + HV and the common.

The output terminal of the linear power amplifier 306
A series circuit of diodes 310, 312 and 314 is connected in the forward direction. Diode 310, 31
A diode 316 is connected in parallel with the opposite polarity to the series circuit 2,314. Downstream of these diode circuits along the supply direction of the amplified output, a series circuit of capacitors 318 and 320 is connected between the amplified output line and the common. A feedback path for an amplified output signal is formed from the series connection point of the capacitors 318 and 320 to the input terminal of the linear power amplifier 306.

The above-described portion including the waveform memory 300 to the capacitors 318 and 320 is an example of the embodiment of the driving means in the present invention. A pair of electrodes of the ultrasonic transducer 322 are connected to the amplified output line and the common, respectively. An electrode connected to the amplification output line is an active electrode, and an electrode connected to the common is a common electrode.

The active electrode of the ultrasonic transducer 322 is connected through a resistor 324 to a negative DC voltage -VEE.
(For example, -3.3 V). The active electrodes of the ultrasonic transducer 322 also
Transistor 3 through diode 326
It is connected to 48 emitters. The base of transistor 348 is connected to common.
The polarity of the diode 326 is forward with respect to the emitter.

The collector of transistor 348
r) is connected through a resistor 350 to a source of a positive DC voltage + VCC (eg + 3.3V). One end of the capacitor 352 is connected to a series connection point of the collector and the resistor 350, and the other end is connected to a reception signal processing circuit (not shown).

The operation of the apparatus will be described. Controller 3
Under the control of 02, the waveform data of the drive signal is read from the waveform memory 300, converted into an analog signal by the D / A converter 304, and input to the linear power amplifier 306.

FIG. 2 shows an example of the waveform of the drive signal. As shown in the drawing, the waveform of the drive signal includes a level increasing section 500 in which the signal level gradually increases from 0 level to the first level, and a level increasing section 500 with the first level as the center and the upper and lower levels respectively. It has a level switching unit 502 that switches between the second level and the third level at high speed, and a level lowering unit 504 that gradually drops from the first level to the 0 level.

The second level is selected to be, for example, twice the first level, and the third level is selected to be, for example, the zero level.
The frequency of the alternation of these signal levels is the center frequency of the vibration of the ultrasonic transducer 322 (for example, 5 MHz).
z). The level change in the level raising section 500 and the level lowering section 504 is performed, for example, over about ten times the duration of the level changing section 502.
The first to third levels are all on one side (+ in this case) with respect to the 0 level. That is, the drive signal is a unipolar signal.

The polarity of the drive signal is determined by the linear power amplifier 3
06 corresponds to the polarity of the power supply voltage adopted, and when a negative power supply voltage is used, the polarity of the drive signal is also negative. Also,
Here, the signal waveform in the level alternation section 502 is shown as an example of a rectangular wave, but is not limited thereto, and may be a sine wave, a triangular wave, or any other appropriate waveform.

The controller 302 operates the linear power amplifier 306 in the strobe 1 having a low slew rate while the drive signal level raising section 500 is being input to the linear power amplifier 306. Control. Also, during the period when the level lowering section 504 of the drive signal is being input to the linear power amplifier 306, control is performed so as to operate in the state of the strobe 1 having a low slew rate.

On the other hand, during the period when the level switching section 502 is input, the linear power amplifier 306 is controlled so as to operate in the state of the strobe 2 having a high slew rate. Thus, the input signal is power-amplified faithfully in the waveform, and is applied to the ultrasonic transducer 322 as a drive signal. Note that the strobe control is not performed for a linear power amplifier having no or unnecessary strobe function.

The size of the ultrasonic transducer 322 changes in response to a change in the level of the drive signal during the application of the level raising section 500. It is slow and generates little sound pressure fluctuation around it. That is, no ultrasonic waves are generated during this period.

The drive signal level changing section 502 changes the size of the drive signal from the size corresponding to the first level to the size corresponding to the second level at a high speed in accordance with the change of the high-speed level of the drive signal. In addition, the dimension corresponding to the first level changes rapidly to the dimension corresponding to the third level. First
The dimensional change corresponding to the second level and the dimensional change corresponding to the third level from the dimension corresponding to the level are opposite in direction to each other, such that when the dimension is enlarged, the dimension is reduced on the other side. Become.

An increase in size of the ultrasonic transducer 322 causes a positive change in sound pressure, and a decrease in size causes a change in negative sound pressure. Therefore, an ultrasonic wave whose sound pressure changes positively or negatively, that is, a bipolar ultrasonic wave is generated and transmitted to the sound field.

After oscillating at an appropriate wave number, the size of the ultrasonic transducer 322 is slowly returned to the original size by the level lowering section 504 of the drive signal. Level descending part 50
Since the change of the signal of No. 4 is slow, the sound pressure does not change due to the dimensional change of the ultrasonic transducer 322.

After the size of the ultrasonic transducer 322 is returned to the original size, the echo is received. At this time, the ultrasonic transducer 322 generates an electric signal according to the intensity of the received echo. The electrical signal becomes a bipolar signal corresponding to the bipolar echo. Transistor 348 can respond to a bipolar input signal by being supplied with a bipolar power supply voltage, that is, + VCC and -VEE, and changes a collector voltage according to an input electric signal. This voltage change is input to the reception processing circuit through the capacitor 342.

The above is an example of a single ultrasonic transducer, that is, an example of a single-channel ultrasonic transmitting / receiving apparatus. However, a plurality of ultrasonic transducers are used to form a multi-channel array. ), The same driving means and receiving means as described above may be provided for each ultrasonic transducer. In this case, it is not always necessary to provide a waveform memory for each channel, and it is preferable to use a common waveform memory for all channels or a plurality of appropriate channels in terms of simplifying the configuration.

FIG. 3 shows a block diagram of an ultrasonic imaging apparatus using the above-described ultrasonic transmitting / receiving apparatus. This device is an example of an embodiment of the present invention. An example of an embodiment relating to the device of the present invention is shown by the configuration of the present device.

As shown in FIG. 3, the present apparatus has an ultrasonic probe 2 (probe). The ultrasonic probe 2 has a multi-channel array configured by using a plurality of the ultrasonic transducers 322 shown in FIG. The plurality of ultrasonic transducers 322 forming an array are one-dimensionally arranged, for example, along an arc that protrudes forward. That is, the ultrasonic probe 2 is a convex probe.
x probe). The ultrasonic probe 2 is used in contact with the subject 4 by an operator.

The ultrasonic probe 2 is connected to the transmission / reception unit 6. The transmission / reception unit 6 transmits a driving signal to the ultrasonic probe 2 to transmit ultrasonic waves into the subject 4. The transmitting and receiving unit 6 also receives an echo signal from the subject 4 that the ultrasonic probe 2 has received. The portion including the ultrasonic probe 2 and the transmission / reception unit 6 has the configuration shown in FIG. 1 for each channel, for example.

The ultrasonic probe 2 and the transmission / reception unit 6 perform scanning, for example, as shown in FIG. As shown in the figure, a sound ray 202 emitted from a radiation point 200 moves on a circular arc 204, thereby forming a fan-shaped two-dimensional area 2.
06 is scanned, so-called convex scan is performed. When the sound ray 202 is extended in the direction opposite to the ultrasonic wave transmission direction (z direction), all the sound rays intersect at one point 208. Point 208 is a divergence point of all sound rays.

The transmitting / receiving section 6 is connected to a B-mode (mode) processing section 10 and a Doppler processing section 12.
The echo reception signal for each sound ray output from the transmission / reception unit 6 is:
It is input to the B-mode processing unit 10 and the Doppler processing unit 12.

The B-mode processing section 10 forms B-mode image data. The B-mode processing unit 10 includes a logarithmic amplifier circuit 102 and an envelope detection circuit 104 as shown in FIG.
It has. The B-mode processing unit 10 includes a logarithmic amplifier 1
02, the echo reception signal is logarithmically amplified, and the envelope detection circuit 1
At 04, a signal representing the intensity of the echo at each reflection point on the sound ray by performing envelope detection, that is, an A-scope signal is obtained. Mode image data is formed.

The Doppler processing section 12 forms Doppler image data. The Doppler processing unit 12 includes a quadrature detection circuit 120 and an MTI filter (movin filter) as shown in FIG.
g target indication filter) 122, autocorrelation circuit 1
24, an average flow velocity operation circuit 126, a dispersion operation circuit 128, and a power operation circuit 130.

The Doppler processing unit 12 includes a quadrature detection circuit 12
0, the echo reception signal is subjected to quadrature detection, and the MTI filter 12
2, an autocorrelation circuit 124 performs an autocorrelation operation, an average flow velocity operation circuit 126 obtains an average flow velocity from the autocorrelation operation result, and a dispersion operation circuit 128 obtains a variance of the flow velocity from the autocorrelation operation result. The arithmetic circuit 130 obtains the power of the Doppler signal from the autocorrelation operation result.

As a result, respective data representing the average flow velocity of the blood flow and the like in the subject 4 and the variance thereof and the power of the Doppler signal, that is, Doppler image data, are obtained for each sound ray. The flow velocity is obtained as a component in the sound ray direction. The direction of the flow is distinguished between a direction approaching and a direction away from it.

The B-mode processing unit 10 and the Doppler processing unit 12 are connected to an image processing unit 14. Image processing unit 1
Reference numeral 4 is for generating a B-mode image and a Doppler image based on data input from the B-mode processing unit 10 and the Doppler processing unit 12, respectively.

As shown in FIG. 7, the image processing unit 14 includes a sound ray data memory (d) connected by a bus 140.
ata memory) 142, digital scan converter
(digital scan converter) 144, an image memory 146, and an image processor 148.

The B-mode image data and the Doppler image data input from the B-mode processing unit 10 and the Doppler processing unit 12 for each sound ray are stored in the sound ray data memory 142, respectively. A sound ray data space is formed in the sound ray data memory 142.

Digital Scan Converter 144
Is for converting data in a sound ray data space into data in a physical space by scan conversion. The image data converted by the digital scan converter 144 is stored in the image memory 146. That is, the image memory 1
Reference numeral 46 stores image data of the physical space. The image processor 148 performs appropriate data processing on the data in the sound ray data memory 142 and the image memory 146, respectively.

The display unit 16 is connected to the image processing unit 14. The display unit 16 is provided with an image signal from the image processing unit 14 and displays an image based on the image signal. The display section 16 is capable of displaying a color image.

The transmitting / receiving unit 6, the B-mode processing unit 10,
Doppler processing unit 12, image processing unit 14, and display unit 16
Is connected to the control unit 18. The control unit 18 supplies a control signal to each unit to control its operation. Also, various notification signals are input from each of the controlled units.

Under the control of the controller 18, the B mode operation and the Doppler mode operation are executed. An operation unit 20 is connected to the control unit 18. The operation unit 20 is operated by an operator, and inputs desired commands and information to the control unit 18. The operation unit 20 is, for example, a keyboard
(panel) with (keyboard) and other operating tools
l)

In the thus constructed apparatus, the transmitting / receiving unit 6 transmits the bipolar ultrasonic wave by the unipolar driving signal as described above. Therefore, by generating an image based on the echo, it is possible to obtain an image with good image quality that is not affected by the DC component of the ultrasonic frequency spectrum and low-frequency components in the vicinity thereof.

The transmission and reception of the ultrasonic beam may be performed by dedicated ultrasonic transducer arrays. In this case, the ultrasonic transducer for transmitting waves may be driven by a drive signal whose level is centered at a constant level without raising and lowering, and whose level alternates at a high frequency above and below the level. This is preferable in that the drive control unit is simplified.

[0050]

As described above in detail, according to the present invention, a method and an apparatus for driving an ultrasonic transducer for transmitting a bipolar ultrasonic wave by a unipolar drive, and
An ultrasonic imaging device including such an ultrasonic transducer driving device can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device according to an example of an embodiment of the present invention.

FIG. 2 is a waveform diagram illustrating an example of a driving signal in the device according to an embodiment of the present invention;

FIG. 3 is a block diagram of an apparatus according to an embodiment of the present invention.

FIG. 4 is a conceptual diagram of sound ray scanning performed by the apparatus according to an embodiment of the present invention;

FIG. 5 is a block diagram of a B-mode processing unit in the apparatus according to the embodiment of the present invention;

FIG. 6 is a block diagram of a Doppler processing unit in the apparatus according to the embodiment of the present invention;

FIG. 7 is a block diagram of an image processing unit in the apparatus according to the embodiment of the present invention;

[Explanation of symbols]

 Reference Signs List 300 Waveform memory 302 Controller 304 D / A converter 306 Linear power amplifier 322 Ultrasonic transducer 500 Level rising section 502 Level changing section 504 Level falling section 2 Ultrasonic probe 4 Subject 6 Transmitting / receiving section 10 B mode processing section 12 Doppler processing section 14 image processing unit 16 display unit 18 control unit 20 operation unit

Claims (3)

[Claims] 1. An ultrasonic transducer driving method for driving an ultrasonic transducer by a unipolar driving signal, wherein the level of the unipolar driving signal is relatively high with respect to a first level. 2. A method for driving an ultrasonic transducer, comprising: alternating between a second level and a third level which is relatively low. 2. An ultrasonic transducer driving device for driving an ultrasonic transducer by a unipolar driving signal, comprising: a second level having a relatively high level and a relatively low level having a first level as a reference. An ultrasonic transducer driving device, comprising: driving means for driving the ultrasonic transducer by a unipolar driving signal whose level alternates with a third level. 3. An ultrasonic imaging apparatus which drives an ultrasonic transducer with a unipolar drive signal to transmit ultrasonic waves and generates an image based on an echo reception signal, wherein the first level is used as a reference. Driving means for driving the ultrasonic transducer by a unipolar driving signal whose level alternates between a relatively high level second level and a relatively low level third level. An ultrasonic imaging apparatus characterized by the following.