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JPH04242399

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This translation is machine-generated. It cannot be guaranteed that it is intelligible, accurate,
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DESCRIPTION JPH04242399
[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a
method and apparatus for scanning a beam using a plurality of ultrasonic transducers.
[0002]
2. Description of the Related Art As shown in FIG. 13, in a transducer array in which a plurality of
ultrasonic transducers are arranged at equal intervals, in order to have directivity characteristics
in the direction of the θ direction from perpendiculars, each vibration It is well known that the
delay amount or phase amount corresponding to dk = d · (k−1) · sin θ (k = 1, 2... N) should be
given to the child. The beam can be scanned in the desired direction by changing it arbitrarily.
[0003]
However, in the above configuration, a delay circuit or a phase application circuit is required to
provide a delay amount or a phase amount to each ultrasonic transducer, so that the circuit
configuration is complicated. There was a problem of
[0004]
The present invention has been made to solve the above-mentioned problems, and it is an object
of the present invention to provide a novel method and an apparatus based thereon capable of
scanning a beam with a simple circuit configuration.
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[0005]
SUMMARY OF THE INVENTION In the beam scanning method according to the present
invention, predetermined weighting is applied to a plurality of ultrasonic transducers arranged at
equal intervals, and the distance between the ultrasonic transducers is set. The ultrasonic beam is
scanned by changing the parameter. A plurality of ultrasonic transducers arranged at equal
intervals and a predetermined value for each ultrasonic transducer are provided as a beam
scanning apparatus based on this. A weight setting unit for giving weights, signal combining
means for combining transmitted and received signals from the plurality of ultrasonic
transducers, and mutual space changing means for changing the mutual space in each ultrasonic
wave signal. It is characterized by
[0006]
Operation As shown in FIG. 12, for a minute sound source of dx length separated by a distance x
from the central portion O of the linear sound source of length l and weighted with excitation
signals in the length direction Consider the sound field at a far distance R0 (R0 >> l) in the θ
direction with respect to the perpendicular.
The directivity coefficient D (θ) in this case is expressed by equation (1).
[0007]
Φ (x) is a sound source distribution function.
[0008]
In Equation 1, when Φ (x) is considered as a time function Φ (t), Fourier transform yields
Equation 2.
[0009]
When Equations 1 and 2 are compared, it is in the form of a variable transformation of x → t 1
→ T k sin θ → ω.
That is, Equation (1) can be expressed by Equation (3) when the sound source distribution is
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given by Φ (x) = cos (ksinθ0x) Φ (x) = sin (ksinθ0x).
[0010]
In the equation 3, when θ ≠ ± θ0 and D (θ) = 0θ = ± θ0, D (θ) ≠ 0, and the beam is
directed in the ± θ0 direction.
Therefore, it is possible to scan the beam in any direction by changing the distance x, ie, the
transducer spacing in the transducer array.
The specific method of changing the transducer spacing will be described in detail in the
following embodiments.
[0011]
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a block diagram showing
an embodiment of an apparatus based on the beam scanning method of the present invention.
1 (1a, 1b,... 1f) are ultrasonic transducers arranged at equal intervals along a straight line, and
the mutual spacing x of the ultrasonic transducers is variable according to a mechanism
described later.
Reference numeral 2 denotes a transformer for the ultrasonic transducer 1. The ultrasonic
transducers 1a, 1d,... Are connected between the secondary coils 2b of the transformer 2, and
one end of the secondary coil 2b and the middle are connected The ultrasonic transducers 1b, 1c,
1e, 1f,... Are connected between the taps, and the ultrasonic transducers 1b, 1c, 1e, 1f are
connected to the ultrasonic transducers 1a, 1d. It connects so that it may become opposite
polarity. Therefore, each ultrasonic transducer 1 is given a weight of an excitation signal
corresponding to each point on the lower sine wave of FIG. The primary coil 2 a of the
transformer 2 is selectively connected to the transmitter 4 or the receiver 5 via the duplexer 3.
[0012]
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Next, a mechanism for changing the mutual spacing x of the ultrasonic transducers 1 will be
described with reference to FIGS. 2 and 3. FIG. In FIG. 2, a pair of ribs 23 and 24 fixed to the
parallel rods 21 and 22 at one end (left end) side is provided to the two parallel rods 21 and 22
kept parallel, and the other end (right end) is provided The slide tubes 25 and 26 movable along
the parallel rods 21 and 22 are inserted, and the slide tubes 25 and 26 are provided with ribs 27
and 28. Then, X-shaped link mechanisms 29 are provided between the ribs 23 and 28 located at
diagonal positions and between the ribs 24 and 27. Furthermore, a return type air cylinder 30 is
bridged between the parallel rods 21 and 22 on the left side of the ribs 23 and 24.
[0013]
In such a configuration, when the air cylinder 30 is caused to extend, the parallel mechanisms 21
and 22 are moved following the movement of the sliding pipes 25 and 26 in the left direction in
the figure by the action of the link mechanism 29. The separation distance is increased while
keeping the parallel.
[0014]
In FIG. 3, 21 and 22 are the same as the parallel bars in FIG. 2, but may be other bars held
parallel to the parallel bars 21 and 22.
31 is a rhombus-shaped frame which is foldable in the vertical (left and right) direction, and
joints 31a and 31b at the top and bottom with respect to one of the frames 31 (shown by 31 ') ,
22 fixed to the pair of ribs 32 and 33, and the joints 31a and 31b of the top and bottom of each
frame 31 other than this are inserted in the parallel rods 21 and 22 and the ribs of the sliding
tube 34 Lock on 35 Furthermore, the frames 31 and 31 'are connected to each other by joining
the joints 31c in the lateral direction between the frames 31 and 31'.
[0015]
In the above construction, when the separation distance between the parallel rods 21 and 22 in
FIG. 3 is reduced, for example, by acting the air cylinder 30, the frame pair 31 'is crushed in the
vertical direction at the fixed position, The distance between the joints 31c on both sides is
increased. At the same time, the other frames 31 also undergo the same deformation, but with
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this deformation, the sliding tubes 34 of the respective frames 31 move in the lateral direction,
and the frames 31 themselves follow the parallel rods. Moving.
[0016]
Since all the frames 31, 31 'receive the same deformation as described above, the joints 31c are
always kept at equal intervals. Therefore, if the ultrasonic transducers 1 are provided in these
joints 31c, the mutual intervals x of the ultrasonic transducers 1 are changed at equal intervals
as the air cylinders 30 expand and contract. Can.
[0017]
By uniformly changing the mutual spacing x between the ultrasonic transducers 1 in this
manner, the directivity coefficient D (θ) changes as shown by the equation (3), so that the
desired direction is obtained. Can scan the beam.
[0018]
FIG. 8 shows the beam directivity characteristic when the mutual spacing of the ultrasonic
transducers is x, and FIG. 9 shows the directional characteristic when this mutual spacing is
larger than x, and the deflection angle of the beam Changes from θ1 to θ2.
The air cylinder 30 described above is provided between the parallel rods 21 and 22. However,
the frame 31 may be directly deformed by the expansion and contraction action of the air
cylinder 30, and instead of the air cylinder 30, a motor, rotational movement Alternatively, a gear
for converting linear motion into a linear motion, a stroke motor integrated with a telescopic rod,
or the like may be used.
[0019]
As a simple method of changing the mutual distance x while keeping the ultrasonic transducers
at equal intervals, as shown in FIG. By mutually connecting the coil springs 41 and changing the
tensile force from both ends, the mutual spacing between the ultrasonic transducers 1 can be
changed. The above is an example in which the mutual spacing of the ultrasonic transducers is
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mechanically changed, but a method will be described in which the mutual spacing is
equivalently changed.
[0020]
In FIG. 5, the distance between the ultrasonic transducers 1A, 2A, 3A, 4A, 5A, 6A (referred to as
group A) indicated by circles is d, and the ultrasonic transducers 1B, 2B, indicated by squares.
The distance between the ultrasonic transducers 1C, 2C, 3C, 4C, 5C, and 6C (called group C)
indicated by triangles with a distance of 1.5 d between the 3B, 4B, 5B, 6B (called group B) They
are arranged so as to be 2 d, and are connected to the secondary coil 2 b via the changeover
switches 51 and 52 in order to set weights as shown in FIG. 6 to the respective ultrasonic
transducers.
[0021]
In this configuration, if the group A is selected by the switches 51 and 52, the transducer spacing
functions as a transducer array of d, and if the group B or the group C is similarly selected, the
transducer spacing is each It works as a 1.5d or 2d transducer array, so it can scan the beam
stepwise.
[0022]
The side lobes of the beam can be suppressed by adding Chebyshev weights to the sine wave
signals given as weights to the ultrasonic transducers in the above embodiments.
Also, although the signal level of one sine wave is used as the weight of the excitation signal
given to the ultrasonic transducer, different signal waves may be superimposed, for example, as
shown in FIG. A direct current signal, a sine wave signal of (B) and a signal obtained by
superimposing sine wave signals of different periods of (C) may be applied as weights to the
ultrasonic transducer, and the directivity characteristic in this case is shown in FIG. As shown,
multiple beams indicated by A, B and C according to the signals (A), (B) and (C) are obtained.
[0023]
In all the embodiments described above, although the beam is always output in two directions as
seen in FIGS. 8, 9 and 11, in order to scan the beam in only one direction, FIG. As shown, each
ultrasonic transducer 61, 62 is given a weight of 1, 1-1, -1, 1, 1, -1, -1, respectively, and groups
of every other ultrasonic transducer 62 are arranged in parallel. And the other groups of
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ultrasonic transducers 61 are connected in parallel, and then input to the adder 63 via the delay
/ phase shifter 64 which changes the delay or phase. At the output of the adder 63, beam signals
can be obtained only in one direction.
[0024]
As described above, according to the present invention, a predetermined weight is given to a
plurality of ultrasonic transducers arranged at equal intervals, and the mutual intervals of the
ultrasonic transducers are changed. Thus, the beam can be easily scanned without using a delay
circuit or the like as conventionally required.
[0025]
Brief description of the drawings
[0026]
1 is a block diagram showing an embodiment of a beam scanning apparatus based on the beam
scanning method of the present invention.
[0027]
FIG. 2 is a view showing a mechanism for changing an interval between ultrasonic transducers in
the apparatus of FIG. 1;
[0028]
3 is a view showing a mechanism for changing an interval between ultrasonic transducers in the
apparatus of FIG. 1;
[0029]
FIG. 4 shows another mechanism for changing the mutual spacing of the ultrasonic transducers.
[0030]
Fig. 5 is a circuit diagram in which the distance between the ultrasonic transducers is changed
electrically.
[0031]
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FIG. 6 is a view showing weight values set for the ultrasonic transducer of FIG. 5;
[0032]
FIG. 7 is a block diagram illustrating an embodiment for scanning a beam in only one direction.
[0033]
FIG. 8 is a diagram showing a change in beam directivity characteristics when the mutual spacing
of ultrasonic transducers is changed.
[0034]
FIG. 9 is a view showing a change in beam directivity characteristics when the mutual spacing of
the ultrasonic transducers is changed.
[0035]
Fig. 10 is a waveform diagram showing weight signals given to the ultrasonic transducer.
[0036]
11 is a diagram showing a beam directivity characteristic obtained by the signal of the weight
shown in FIG.
[0037]
12 is a diagram showing the principle of the beam scan of the present invention.
[0038]
FIG. 13 is a diagram showing the principle of a conventional beam scanning method.
[0039]
Explanation of sign
[0040]
DESCRIPTION OF SYMBOLS 1 Ultrasonic advancing child 2 Transformer 3 Transmissionreception switch 4 Transmission part 5 Reception part 21,22 Parallel rod 23,24,27,28,35 Tab
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25,26,34 Sliding pipe 29 Link mechanism 30 Air cylinder 31a, 31b, 31c Joint 41 Coil Spring 61,
62 Ultrasonic Transducer 63 Adder 64 Delay / Phaser
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