JPH06292668A - Ultrasonic equipment - Google Patents

Abstract

PURPOSE:To measure the vector velocity of an object by performing an operation to transmit an ultrasonic wave and to transmit a reflected signal from a specified direction by plural elements several times, time-sequentially obtaining the received signals of respective elements corresponding to specified depth and performing Fourier transformation to the result. CONSTITUTION:Ultrasonic signals Tp are successively transmitted from an element for transmission to a comparatively wide range 2 at time intervals T, signals from a reflector are received by an arrangement type receiver 3, and the curvature of a wave surface depending on a distance to the reflector is corrected by a recessed surface delay circuit 4. Thus, received signals R (n, m, p) to be changed like 5, 6 and 7 are provided corresponding to the position of the reflector to be changed with the passage of time. Signals R0 (m, p) (=R (n0, m, p) at the specified time (a sample number n0) of such a received signal are changed like 8, 9 and 10. Fourier transformation is performed to such a signal in the arranging direction and normal projection processing is performed so as to measure operation velocity in the manner of a vector.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to vectorial velocity measurement of an object by ultrasonic waves.

[0002]

2. Description of the Related Art A method for measuring the velocity of an object by the Doppler effect of ultrasonic waves is known. There is also a method of making it possible to measure a velocity component in a direction orthogonal to the traveling direction of ultrasonic waves. This method performs an operation of transmitting ultrasonic waves and receiving a reflection signal from a specific direction by a plurality of elements a plurality of times, and Fourier transforms a reception signal corresponding to a specific depth in an array direction,
This is a method (hereinafter referred to as CV) of measuring the vectorial motion velocity by considering the resulting time change as a two-dimensional signal and performing radial Fourier transform.

[0003]

According to this CV, a radial Fourier transform is required and a special configuration is required. Therefore, this problem is solved and the equivalent effect is realized by the normal technique.

[0004]

An operation of transmitting an ultrasonic wave and receiving a reflected signal from a specific direction by a plurality of elements is performed a plurality of times, and a received signal of each element corresponding to a specific depth is obtained in time series. The result is subjected to a normal one-dimensional or two-dimensional Fourier transform, and a normal projection process is performed to measure the vectorial motion velocity. This method does not require a special Fourier transform with respect to the radial direction.

[0005]

The transmission / reception operation of this system will be described with reference to FIG. First, a relatively wide range 2 from the transmitting element 1 shown in FIG.
, The ultrasonic signal Tp (p = −P ... +) with the time interval T
P) are sequentially transmitted. The signal from the reflector is received by the arrayed wave receiver 3, and the curvature of the wavefront depending on the distance to the reflector is corrected by the concave delay circuit 4. The received signal R (n, m, p) thus obtained changes to 5, 6, and 7 in accordance with the position of the reflector that changes with time. A signal R of such a received signal at a specific time (sample number n ₀ )
₀ (m, p) (= R (n ₀ , m, p)) changes to 8, 9, and 10.

That is, the spatial frequency of the target signal corresponds to the movement of the reflector in the azimuth direction, and changes with time as shown in FIG. 2a. Here, M is the total number of elements. The signal R ₁ (ω, p) is obtained on the inclined straight line 11 by Fourier transforming such a signal in the array direction as shown in FIG. Here, the gradient θ _{0 of} this straight line corresponds to the azimuth direction velocity of the reflector.

Here, when the reflector simultaneously has a velocity component in the distance direction as shown in FIG. 3a, the phase of the signal rotates as shown in FIG. 3b. This phase rotation speed corresponds to the distance direction speed of the reflector.

Then, this R ₁ (ω,
If the two-dimensional Fourier transform of p) is performed, R ₂ (m,
f). Here, the first variable of R ₂ returns to the array element position variable m, which is an initial variable, from the relationship in the Fourier transform. The distance r ₀ in FIG. 4b corresponds to the frequency on the inclined straight line 11 of R ₁ (ω, p) and thus to the distance-wise velocity of the object.

This R ₂ (m, f) is represented by 12, 13, 14 in FIG.
Project in various directions as shown in. When this projection result is displayed in correspondence with the projection direction θ and the distance r from the center, FIG.
It becomes R (r, θ) of b, and a large signal is displayed at the position (r ₀ , θ ₀ ) corresponding to the azimuth direction and the distance direction speed of the target, which is the projection result in the direction indicated by 13. From this position, the target vector velocity can be obtained.

The entire processing described above is shown in FIG.
Here, 15 is a one-dimensional Fourier transform in the array direction, 16
Is a two-dimensional Fourier transform, and 17 is a projection process in the radial direction.

The above is the basic construction method which is formed by first performing the Fourier transform in the array direction and then the two-dimensional Fourier transform. Here, as shown in FIG.
The first dimension of ₂ (m, f) returns to the variable m for the initial device position. Therefore, the received signal R ₀ (m, p) is directly transformed into R
₂ (m, f) will be obtained. By projecting this R ₂ (m, f), the target vector velocity can be obtained as in the basic configuration. The whole of this simplified configuration is shown in FIG. Here, 18 is a one-dimensional Fourier transform in the time direction, and 17 is a projection process in the radial direction.

In the configuration of FIG. 6 or 7, R
_In order to obtain ₂ (m, f), a Fourier transform with respect to the time axis direction p is performed somewhere.
8b is added to the p direction of the received signal R ₀ (m, p) shown in FIG. With such weighting,
As shown in FIG. 8C, the Fourier transform related to the weighting result p is such that a portion having half the amplitude and the opposite phase is added to both sides of the target signal output. Therefore, as shown in FIG. 9, although the projection in the θ ₀ direction 13 corresponding to the azimuth velocity of the object grows to a large value, the direction 1 deviated from that direction by a small amount Δθ.
The projection onto 2 or 14 is greatly reduced by the canceling effect of this antiphase portion. Therefore, the velocity resolution in the azimuth direction is significantly improved. Further, the weighting in this Fourier transform is not limited to this method, and it is possible to have various shapes in arbitrary directions, and the respective unique effects are expected.

A typical example can be seen in FIG. 7, but in the case of performing the Fourier transform in the time axis direction, as shown in FIG. 10, the portion A of the oldest signal from R ₂ (m, f) is Fourier-transformed. removed in the region, it is added to effect B latest signal R ₂ at the next time _{(m, f) R 2 '} (m, f) sequential processing to derive the _{R 2' (m, f)} = R 2 (m, f) -A + B greatly simplifies the Fourier transform in cases such as continuous measurement.

Next, considering the case where a fixed reflector is present, the measurement accuracy will be reduced as it is. Therefore, the difference R ₀ ′ (m,
If p) is R ₀ ′ (m, p) = R ₀ (m, p) −R ₀ (m, p + 1), only the signal corresponding to the moving object that changes with time remains largely, and By performing the speed measurement process, the target speed measurement can be performed without lowering the measurement accuracy. This difference processing may have any configuration as long as it is a means for suppressing a fixed signal, and is not limited to this configuration.

[0015]

FIG. 11 shows the structure of the entire apparatus according to the present invention. Here, 19 is an array type ultrasonic wave transmitter / receiver, and an ultrasonic wave is generated in a target region by vibrating a part of the ultrasonic wave transmitter / receiver by a signal from the drive signal source 20. The signal from the reflector is received by 19. This received signal is the amplifier 2
The signal is amplified by 1, digitized by the analog-digital converter 22, and input to the speed calculator 23. The speed calculation processing according to the present invention is performed by the speed calculation unit, and the display is made by the hue, the brightness, the numeral or the like on the 24 display unit. Other than this, the normal processing of the ultrasonic device is naturally used together. Further, various expanded configurations such as three-dimensional vector measurement performed in the CV are also possible in this system as well.

[0016]

According to the apparatus of the present invention, the vector velocity can be measured only by the ordinary Fourier transform.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of received signals.

FIG. 2 is an explanatory diagram of an array direction one-dimensional Fourier transform output.

FIG. 3 is an explanatory view of speed in a distance direction.

FIG. 4 is an explanatory diagram of a two-dimensional Fourier transform output.

FIG. 5 is a radial projection explanatory diagram.

FIG. 6 is an explanatory diagram of a basic configuration.

FIG. 7 is an explanatory diagram of a simple configuration.

FIG. 8 is an explanatory diagram of weighting.

FIG. 9 is an explanatory diagram of a weighting effect.

FIG. 10 is an explanatory diagram of a sequential Fourier transform.

FIG. 11 is a diagram showing an example of the overall configuration of the embodiment.

[Explanation of symbols]

Reference numeral 19 ... Transceiver, 20 ... Transmission signal source, 21 ... Amplifier, 2
2 ... Analog-digital converter, 23 ... Speed calculator,
24 ... Display section.

Claims (5)

[Claims] 1. A means for transmitting an ultrasonic wave, a plurality of elements for receiving a reflected signal from a specific direction, and a Fourier transform of a received signal corresponding to a specific depth obtained by performing the receiving operation a plurality of times in a time series direction. And an ultrasonic device comprising means for measuring the vectorial motion velocity by projecting the resulting two-dimensional signal in each direction. 2. A means for transmitting an ultrasonic wave, a plurality of elements for receiving a reflection signal from a specific direction, and a reception signal corresponding to a specific depth obtained by performing the receiving operation a plurality of times in the element array direction. An ultrasonic device comprising means for performing a Fourier transform, means for performing a two-dimensional Fourier transform of the result, and means for measuring the vectorial motion velocity by projecting the result in each direction. 3. The apparatus according to claim 1 or 2,
An ultrasonic device comprising means for performing signal difference processing during Fourier transform. 4. The apparatus according to claim 1 or 2,
An ultrasonic device comprising means for performing Fourier transform processing by sequential processing. 5. The apparatus according to claim 1 or 2,
An ultrasonic device comprising means for weighting signals during Fourier transform.