JPS6275258A - Motor controller for mechanical scan type ultrasonic probe - Google Patents

Abstract

PURPOSE:To improve the resolution of the center part of an ultrasonic image by providing a converting means which inputs a rotational angle signal from a counter and a signal of the preset scanning speed of a vibrator and converts them into data on the rotating speed of a motor on the output side of the counter, and inputting its output data as a command to a differential amplifier. CONSTITUTION:A controller is provided with the 2nd ROM 16 and a D/A converter 17 between the counter 1 and differential amplifier 9. Then, the data on a rotating speed omegam which is outputted 16 is D/A-converted 17 and the signal of the speed omegam is inputted as the command of the rotating speed to the differential amplifier 9. For the purpose, the amplifier 9 compares a voltage signal omegaf proportional to the rotating speed of a motor 3 with the command of the speed omegam of the motor 3 and outputs a deviation signal epsilon. This signal epsilon is amplifier 10 and applied as a control voltage V to the motor 3. At this time, a voltage V varies reversely with the difference from the command at any time, so the actual rotating speed of the motor 3 varies while following up the command of the speed omegam is outputted 17 and the scanning speed omegas of the vibrator becomes a constant speed which is set 18.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a motor control device for a mechanical scanning ultrasound probe in which a transducer performs a pendulum motion to scan in an ultrasound tomography device, and in particular to This invention relates to a motor control device iT for a mechanical scanning ultrasonic probe that can improve the resolution at the center.

As shown in FIG. 4, a conventional mechanically running type ultra-7'f-wave probe 1 includes a transducer 2 for transmitting and receiving ultrasonic pulses, and a transducer 2 for transmitting and receiving ultrasonic pulses.
A motor 3 is provided between the rotary shaft 4 of this motor 3 and the vibrator 2, and the rotational movement of the rotation +1ii 114 is driven in a swing T- shape as shown by arrows Δ and B. It comprises a converter 5 for converting motion into motion, and an encoder 6 as a rotation speed detector connected to an extension of the rotation shaft 4 of the motor 3 and detecting the rotation speed of the motor 3.

In FIG. 4, reference numeral 7 indicates transmission oil as a medium that improves the transmission of ultrasonic waves.

As shown in FIG. 5, the motor control device that controls the rotation of the motor 3 of the mechanical scanning ultrasonic probe 1 includes, in addition to the motor 3 and the encoder 6, the rotation of the motor 3 of the mechanical scanning ultrasonic probe 1. A frequency-voltage converter (hereinafter referred to as rF/V converter) that inputs a rotational speed signal (rotational frequency) S and outputs an analog voltage signal proportional to the rotational speed of the motor 3.
) 8 and the voltage signal ω from this F/V converter 8.

and a constant voltage motor speed command value ω given as a target value. A differential amplifier 9 outputs a deviation signal E by comparing the difference signal E, a servo amplifier 10 amplifies this deviation signal ε, and a servo amplifier 10 amplifies the deviation signal ε. The counter 11 outputs a signal.

Next, the operation of the motor control device for the mechanical scanning ultrasonic probe configured as described above will be explained.

First, the motor 3 rotates, and the signal S of the rotation speed of the motor 3 obtained by the encoder 6 is input to the F/V converter 8 and converted into a voltage signal ω proportional to the rotation speed of the motor 3. be done. This voltage signal ωa is then input to one terminal of the differential amplifier 9.

Here, a motor speed command value ω of a constant voltage is inputted to the other terminal of the differential amplifier 9 as a target value.

Therefore, this differential amplifier 9 outputs the voltage signal ω and the motor speed command value ω. are compared, and if there is a difference between the two, a deviation signal E is output. This deviation signal ε is amplified by a servo amplifier 10 and applied to the motor 3 as a control voltage ■. At this time, since the control voltage V always changes in the opposite direction to the speed change of the motor 3, the rotational speed of the motor 3 is always controlled to be constant. On the other hand, the rotational speed signal S□ from the encoder 6 is input to a counter 11 and counted, and the signal of the rotation angle 0 of the motor 3 outputted from the counter 11 is input to a ROM (read-only memory) 12. The ROM 12 converts and outputs synchronization signals and addresses for emitting, receiving, and raster scanning ultrasonic pulses at every fixed rotation angle of the motor 3. With such an operation, as shown in FIG. 6, the probe 1 is pressed against the test site of the subject 13, and the transducer 2 is scanned in the directions of arrows A and B, as shown in FIG. An ultrasound image 14 like this was obtained.

The problem that the invention seeks to solve However, in such a motor control device.

Since the motor speed command value ω, which is a target value given to the differential amplifier 9, is a constant voltage, the motor 3 is controlled to always rotate at a constant speed. In this state, as shown in FIG.
Drive the converter 5 installed at 1, and the rotation speed of the rotating shaft 4! When Fl+ is converted into a pendulum motion like the arrows Δ and B, the arrows A and [3
The speed on the reciprocating side 1ft+ of the direction is not constant. That is, arrow A.

The reciprocating motion in the 13 directions is fast at the center and slow at the side edges. This ultimately directly affects the scanning speed of the transducer 2, and as shown in FIG. It was fast at C, and slow at the side edges, and slow at E. Therefore, as is clear from FIG. 7, in the ultrasound image 14, the density of the raster 15 is low at the scanning center C, and the density of the raster 15 is low at both ends of the scan, and at E, the density of the raster 15 is low.
It was a secret. In other words, the resolution at the center of the scan is reduced. For example, in an ultrasonic diagnostic apparatus, the most important part for diagnosis is at the center C of scanning the ultrasonic image 14, and at both ends, E.
There are very few parts that are important for diagnosis. Therefore, in the conventional apparatus, the resolution of the most important part for diagnosis deteriorates. To deal with this, doubling the number of rasters to improve the resolution in the center of the scan by a factor of, say, doubles the number of rasters while the ultrasound is reflected back from the desired diagnostic depth. Since the rotational speed of the motor 3 cannot be produced, the rotational speed of the motor 3 must be reduced, for example, by half. In this case, the number of ultrasonic image frames 11, that is, the number of frames obtained per second, is halved, resulting in another problem in that real-time performance is degraded.

Therefore, it is an object of the present invention to solve these problems.6 Means for Solving the Problems The means of the present invention for solving the above problems are based on a motor, a rotation speed detector, and a frequency detector. In a motor control device for a mechanical scanning ultrasonic probe that includes a voltage converter, a differential amplifier, and a counter, a rotation angle signal from the counter and a preset transducer are transmitted to the output side of the counter. A converting means is provided for inputting a scanning speed signal and converting the received signal into data of the rotational speed of the motor, and the data outputted from the converting means is inputted as a target value of the differential amplifier. done by

Embodiments One embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of a motor control device for a mechanical scanning ultrasound probe according to the present invention. This motor control device is a servo control system that controls the rotation of the motor 3 of the mechanical scanning ultrasonic probe 1 shown in FIG. , a differential amplifier 9 , a servo amplifier 10 , and a counter 11 .゛The encoder 6 serves as a rotation speed detector that detects the rotation speed of the motor 3. For example, a light emitting diode or the like is used to irradiate a disc with a slit rotated by the rotation shaft of the motor 3, The number of rotations of the motor 3 is detected based on the on/off frequency of the light provided by the attached disc. The F/V'& converter 8 inputs the rotational speed signal (rotational frequency) S from the encoder 6 and outputs an analog voltage signal ω5 proportional to the rotational speed of the motor 3. The differential amplifier 9 has the above F/
A deviation 48 is determined by comparing the voltage signal ω from the V converter 8 and a signal of the motor speed ω, which will be described later, given as a target value.
This outputs the number E. The servo amplifier 10 amplifies the deviation signal E from the differential amplifier 9 and supplies a control voltage V to the motor 3. The counter 11 counts the rotational speed signal S1 from the encoder 6 and outputs a signal representing the rotational angle O of the motor 3. Note that the first ROM 12 connected to this counter 11 inputs the signal of the rotation angle θ and stores a synchronization signal and an address for emitting, receiving, and rask scanning ultrasonic pulses at every fixed rotation angle of the motor 3. It is converted into .

Here, in the present invention, a second ROM 16 and a D/A converter 17 are provided between the counter 11 and the differential amplifier 9.
is provided. Furthermore, control signals from the console 18 are input to the second ROM 1.6. The second ROM 1 (3) inputs the signal of the rotation angle 0 from the counter 11, and also inputs the signal of the scanning speed ω5 of the vibrator 2, which is preset by operating the console 18, and responds to these. It serves as a conversion means for converting the rotational speed ω1 of the motor 3 into data, and has the answer calculated using a predetermined arithmetic expression as a conversion table.At this time, the rotational angle O of the motor 3 and

There is a relationship between the scanning speed ω of the vibrator 2 and the rotation speed ω1 of the motor 3 as follows: ω=K (il+) ·ω−(1). Here, K(0) is a function related to any rotation/pendulum motion conversion mechanism that the converter 5 shown in FIG. 4 is. Transforming equation (1):

It becomes ω0. As is clear from this equation (2), the oscillator 2
If the scanning speed ω5 of the motor 3 is constant, then the rotational speed ω of the motor 3 is
, changes as a function of the rotation angle O. Therefore, by performing the calculation of equation (2) for the value of ω,
The answer may be stored in the second R2M 17 as a conversion table. Then, set a constant scanning speed ω3 of the transducer 2 corresponding to a certain display depth by operating +31 g, and change the rotation angle O of the motor 3 from the counter 1.
When the signals of are sequentially input, the second ROM 16 receives the following signals.

The conversion table that is the calculation result of the above equation (2) is looked up one after another, and ``--scanning speed ω and rotation angle 0 inputted by the criminal.
The data of the rotational speed ω1 of the motor 3 corresponding to the rotational speed ω1 of the motor 3 is sequentially output. That is, the second ROM 16 stores information about the motor 3 when the rotation angle θ of the motor 3 reaches a certain angle.
This outputs data on how much the rotational speed ω- should be.

The data of the rotational speed ω1 output from the second ROM 16 is input to the D/A converter 17 and converted into an analog signal. The signal of the rotational speed ω1 from the D/A converter 17 is inputted to the target value terminal of the differential amplifier 9 as a rotational speed command value. Therefore, this differential amplifier 9 receives a voltage signal proportional to the current rotation speed of the motor 3 inputted from the F/V converter 8, and a command value of the rotation speed ω□ at the rotation angle O of the motor 3. Compare the
If there is a difference between the two, a deviation signal E is output. This deviation signal E is amplified by a servo amplifier 10 and applied to the motor 3 as a control voltage V.

At this time, the control voltage V always changes in the opposite direction to the difference from the target value, so the actual rotational speed of the motor 3 is the rotational speed ω outputted via the D/A converter 17.
It changes following the second command value. In this way, the above-mentioned equation (2) is always satisfied, so that the scanning speed ω3 of the vibrator 2 becomes a constant speed set on the console 18.

Further, as described above, since the actual rotational speed of the motor 3 increases or decreases so as to satisfy the above-mentioned formula (2), the rotational speed signal S1 applied from the encoder 6 also changes. . Then, the output of the counter 11 that counts this rotational speed signal S also changes, and the rotational angle O signal from this counter 11 is inputted to emit, receive, and emit ultrasonic pulses at every fixed rotational angle of the motor 3. The synchronization signal of the first ROM 12 that performs raster scanning will also change. In other words, the emission period of the ultrasonic pulses from the five probes 1 changes. In this case, reception of reflected echoes is disturbed due to the displayed depth of the object, and a good ultrasound image cannot be obtained. Therefore, it is necessary to correct the change in the rotational speed signal S□ from the encoder 6 as described above. Now, the emission period Δ of the ultrasonic pulse is expressed on both sides of the equation (2) above.
Multiplying by T gives . Here, since ΔT·ω1 is nothing but the rotation angle interval Δ0 of the motor 3 at which ultrasonic pulses are to be emitted, the following equation is obtained. Therefore, a raster synchronization signal may be outputted from the first ROM 12 every 80 rotation angles. At this time, ω,・△T is the operation console 18
is given when setting the scanning speed ω3 of the vibrator, and the rotation angle O of the motor 3 is input from the counter 11, so the calculation of equation (4) is performed for several types of values of ω・△T. , use the answer as a conversion table in the first ROM above.
It is sufficient to store it in 12. As a result, the first ROM
From 12, a raster synchronization signal is output for each rotation angle of Δ0 given by the above equation (4).

A mechanical scanning ultrasonic probe 1 whose rotation of the motor 3 is controlled by such a motor control device is pressed against the examination site of the subject 13 as shown in FIG. By scanning in direction B, an ultrasonic image 14' as shown in FIG. 2 is obtained. That is, a constant value is input as the scanning speed ω3 of the vibrator 2 from the console 18, and the motor 3 is controlled to follow the command value of the rotational speed ω□ of the motor 3 so that the scanning speed is always constant. The actual rotation speed is slow at rotation angle 0 corresponding to the center C of the raster scan scanning range, and fast rotation at the rotation angle O corresponding to the side edges E. Therefore, the reciprocating speed of the pendulum motion by the transducer 5 provided on the rotating shaft 4 of the motor 3 is constant, and as a result, the scanning speed by the vibrator 2 is constant. For this reason, as shown in FIG. 2, in the ultrasound image 14', there are more rasters 15 at the center C of scanning than before, and at the side edges,
The number of rasters 15 in E is slightly reduced, and the density of rasters can be made uniform over the entire range.

FIG. 3 is a block diagram showing another embodiment.

In this embodiment, the F/V converter 8 is a digital speed counter that counts the rotation speed signal S1 from the encoder 6 in a fixed time, and the differential amplifier 9 is a digital subtracter. A /A converter 17 is provided between the differential amplifier 9 and the servo amplifier 0. In this case, the voltage signal ω proportional to the rotational speed ω of the motor 3 as a target value and the rotational speed of the motor 3, and the deviation signal ε between the two are digital quantities. This deviation signal ε is then converted into an analog signal by the D/A converter 17 and sent to the servo amplifier 10.

Effects of the Invention As explained above, the present invention inputs the signal of the rotation angle θ of the motor 3 from the counter 11 and the signal of the preset scanning speed ω5 of the vibrator 2 to the output side of the counter 11. A second ROM 1'6 (conversion means) is provided to convert these into data of the rotational speed ω1 of the motor 3 corresponding to these data, and the data output from this ROM 16 is inputted as a target value of the differential amplifier 9. Therefore, the rotational speed of the motor 3 can be changed following the data on the rotational speed ω outputted from the second ROM 16.

Here, by setting the scanning speed ω3 of the vibrator 2 to a constant value, the actual rotational speed of the motor 3 changes between the center and side edges of the scanning range of the raster scan of the vibrator 2. As a result, the scanning speed of the vibrator 2 can be kept constant. Therefore, as shown in Figure 2,
In the ultrasonic image 14', the number of rasters 15 at the center C of the scan is larger than before, and the number of rasters 157J' at the side edges is slightly smaller than that at the center of scanning, and the density of rasters can be made uniform over the entire range.

Therefore, it is possible to prevent the density of the raster 15 from becoming coarse in the center of the raster scan as in the conventional method, and improve the resolution of the center of the ultrasound image. Therefore,
For example, in a diagnostic image of an ultrasound diagnostic device, the most important part for diagnosis in the center of one image can be captured with high resolution at t81? '3
can do. Also.

If the resolution in the center of the ultrasound image is kept at the same level as in the conventional technology and the raster density in the entire range is made uniform, motor 3
The rotation time required for one scan is shortened, the number of ultrasonic image frames is increased, and real-time performance can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a motor control device for a mechanical scanning ultrasound probe according to the present invention, FIG. 2 is an explanatory diagram showing an ultrasound image obtained by implementing the present invention, and FIG. A block diagram showing another embodiment of the present invention, FIG. 4 is a sectional view showing the structure of a mechanical scanning ultrasonic probe, FIG. 5 is a block diagram showing a conventional motor control device, and FIG. 6 is a mechanical FIG. 7 is an explanatory diagram showing a state in which a scanning ultrasound probe is pressed against a subject for inspection, and FIG. 7 is an explanatory diagram showing an ultrasound image obtained by implementing the conventional example. 1... Mechanical scanning ultrasonic probe 2... Transducer 3... Motor 5/Converter 6... Encoder (rotation speed detector) 8... Frequency voltage converter 9... Differential amplifier 10... Servo amplifier 11... Counter 12... First ROM 16... Second ROM (conversion means) 17... D/A
Converter 18/operation console

Claims (1)

[Claims] A motor that drives and scans a vibrator that transmits and receives ultrasonic pulses in a pendulum shape, a rotation speed detector that is coupled to the rotation shaft of this motor and detects the rotation speed of the motor, and a rotation speed detector that detects the rotation speed of the motor. a frequency-voltage converter that outputs a voltage signal proportional to the rotational speed of the motor using a numerical signal; and a differential amplifier that compares the voltage signal from the frequency-voltage converter with a predetermined target value and outputs a deviation signal. and a counter that counts the rotational speed signal from the rotational speed detector and outputs a rotation angle signal of the motor, wherein the output side of the counter includes: A conversion means is provided for inputting a rotation angle signal from the counter and a preset scanning speed signal of the vibrator and converting the data into corresponding data on the rotation speed of the motor, and output from the conversion means. A motor control device for a mechanical scanning ultrasonic probe, characterized in that data is input as a target value of the differential amplifier.