JP4682577B2 - Ultrasonic imaging method and ultrasonic imaging apparatus - Google Patents

Description

  The present invention relates to an ultrasonic imaging apparatus and an image for generating a distance image of an object by measuring a distance to the detection object and its azimuth by receiving a reflected wave of the transmitted ultrasonic wave from the detection object. It relates to the conversion method.

  Conventionally, the time (propagation time) from when the sound wave transmitted from the ultrasonic transmitter is reflected by the object and received by the ultrasonic receiver is measured, and each direction is determined based on the propagation time and the sound velocity. A technique for measuring the distribution of the distance to an object in is generally known. For example, in a general ultrasonic imaging field used for underwater exploration, non-destructive inspection, and medical diagnosis, a probe that uses piezoelectric elements arranged one-dimensionally and is shared for transmission and reception of ultrasonic waves is used. The probe is mechanically rotated to perform angular scanning, and an image of the cross section through which the fan-shaped beam passes is obtained by echoes from parts with different acoustic impedances (for example, biological tissue boundaries). There is.

  In addition, in the air, reflected ultrasonic waves are received by an ultrasonic array sensor in which a plurality of ultrasonic receiving elements are arranged in an array, and the incident angle of the ultrasonic wave and the element's angle are received with respect to the reception signal of each ultrasonic receiving element. A technique is known in which only a reflected wave from an arbitrary direction is selectively extracted by performing arithmetic processing with a delay corresponding to the positional relationship (see Patent Document 1). According to this, the distance and azimuth of the object reflecting the ultrasonic waves by the so-called electronic scanning, in which the azimuth is scanned only by electrical signal processing without performing mechanical scanning, that is, the three-dimensional of the object. Can acquire information related to various positions, and can obtain a distance image of an object.

In addition, since the ultrasonic wave has a lower frequency and a lower propagation speed than light such as laser light, there is an advantage that it can be configured inexpensively in terms of circuit. For this reason, an object recognition sensor such as an obstacle using ultrasonic waves is being used in the same manner as a sensor using light such as laser light.
JP 2002-156451 A

  However, in Patent Document 1 and other disclosed documents, a method and an apparatus for generating a distance image capable of recognizing a plurality of objects having different ultrasonic reflectivities and performing object behavior analysis and tracking can be seen. Absent.

  The present invention solves the above-described problems, and does not depend on the ultrasonic reflectance of the target object, and can generate an object distance image that can easily analyze and track the behavior of the object. An object is to provide an imaging method and an ultrasonic imaging apparatus.

In order to achieve the above-mentioned object, the invention of claim 1 is directed to an ultrasonic azimuth sensor using an ultrasonic array sensor formed by two-dimensionally arranging a plurality of ultrasonic receiving elements in the X and Y directions at predetermined intervals. An ultrasonic imaging method for obtaining a distance image of an ultrasonic reflection object in the image and generating a distance image of the object, receiving a reflected ultrasonic wave from the front and outputting a signal of each ultrasonic reception element for each direction A delay addition step for obtaining the distance of the ultrasonic reflecting object by delay addition, a viewing angle setting step for setting a viewing angle in the X direction and the Y direction from the center of the ultrasonic array sensor, and a directivity of the ultrasonic array sensor The angle resolution setting step for setting the angular resolution in the X direction and the Y direction from the characteristics, and the numbers obtained by dividing the set viewing angles in the X direction and the Y direction by the angular resolutions in the X direction and the Y direction, respectively. That X direction pixel number, image generating step of generating a pixel number setting step for the Y-direction number of pixels, a distance image in association with the orientation in each pixel of the two-dimensional map consisting of the X-direction pixel number and the Y-direction pixel number If the provided distance image in the image generation step using the distance and direction corresponding to the peak signal in the signal intensity distribution formed from the signal strength of the delay addition to obtained signals and said orientation at said delay adding step Is generated.

  According to a second aspect of the present invention, in the imaging method according to the first aspect, the distance image is generated by detecting the distance and direction of a specific two-dimensional plane in the front three-dimensional space.

  According to a third aspect of the present invention, in the imaging method according to the second aspect, the delay addition step is time-divided to generate a plurality of the distance images.

  According to a fourth aspect of the present invention, in the imaging method according to any one of the first to third aspects, a distance and direction corresponding to the maximum peak signal among a plurality of peak signals are generated as a distance image. Is.

  According to a fifth aspect of the present invention, in the imaging method according to any one of the first to fourth aspects, the distance and direction of the ultrasonic reflecting object are detected in time series, and are continuously displayed on the distance image. The moving direction of the sound wave reflecting object can be estimated.

  According to a sixth aspect of the present invention, in the imaging method according to the fifth aspect, the interval for obtaining the distance of the ultrasonic reflecting object is changed depending on whether the ultrasonic reflecting object is recognized or not.

  According to a seventh aspect of the invention, there is provided an ultrasonic wave transmitting means and an ultrasonic array sensor formed by two-dimensionally arranging a plurality of ultrasonic receiving elements in the X direction and the Y direction at a predetermined interval, from the ultrasonic wave transmitting means. An ultrasonic imaging apparatus that receives reflected ultrasonic waves reflected by a forward object by the ultrasonic array sensor and obtains an orientation and a distance of the object to generate a distance image of the object, A signal amplifying means for amplifying a signal of the ultrasonic receiving element; a delay synthesizing means for calculating a distance for each direction by delay combining and AD converting each signal amplified by the signal amplifying means; Peak signal extraction means for extracting the distance and azimuth corresponding to the peak signal in the signal intensity distribution formed from the signal intensity and azimuth of the signal obtained by the delay synthesis means, and the directivity and viewing angle of the ultrasonic array sensor Imaging means for generating a distance image using the distance and the direction corresponding to the peak signal, with the direction corresponding to each pixel of the two-dimensional map of the number of X direction pixels and the number of Y direction pixels set based on It is a thing.

  According to an eighth aspect of the present invention, in the imaging method according to the seventh aspect, the image analyzing means for analyzing the moving direction and behavior of the imaged object based on the temporal change of the distance image, and the image analyzing means And an external notification means for notifying the obtained result to the outside.

  According to the first aspect of the present invention, since the distance image is generated based on the peak signal in the ultrasonic signal intensity distribution, the object can be recognized even when the reflectance of the ultrasonic reflection object is low, and the reflectance varies. It is possible to generate a distance image that is not affected by.

  According to the invention of claim 2, a distance image can be generated with a smaller amount of data processing than when a three-dimensional image is obtained, and a simple distance image that can be used for object behavior analysis and tracking can be obtained.

  According to the invention of claim 3, a plurality of distance information can be obtained efficiently.

  According to the fourth aspect of the present invention, it is possible to clearly analyze and track the behavior of a plurality of objects in a group activity or an object having a plurality of ultrasonic reflection intensity peaks based on the behavior of representative points.

  According to the invention of claim 5, the time-series behavior of the object is easy to understand and the movement of the object can be easily predicted.

  According to the invention of claim 6, by changing the interval for obtaining the distance of the ultrasonic reflecting object spatially or temporally, the distance following the movement of the object, regardless of whether the moving speed of the object is fast or slow. An image can be generated. For this reason, for example, a recording medium can be saved when an image is recorded.

  According to the seventh aspect of the present invention, since the distance image is generated based on the peak signal in the ultrasonic signal intensity distribution, the object can be recognized even when the reflectance of the ultrasonic reflection object is low, and the reflectance varies. It is possible to generate a distance image that is not affected by.

  According to the eighth aspect of the present invention, it is possible to estimate the behavior of an object, sound an alarm for an approaching object, and repel it.

  Hereinafter, an ultrasonic imaging apparatus according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a block configuration of the ultrasonic imaging apparatus 10. The ultrasonic imaging apparatus 10 includes an ultrasonic transmission unit 1 that is a sound source that emits sound waves of a predetermined frequency (for example, about 40 to 100 kHz) and a plurality of ultrasonic reception elements 20 in the X direction and the Y direction at regular intervals. An ultrasonic array sensor 2 formed in a two-dimensional array, and the ultrasonic array sensor 2 receives the reflected ultrasonic waves reflected by the object T in front of the ultrasonic waves transmitted from the ultrasonic transmission means 1 and that object. It is an imaging device which produces | generates a distance image by calculating | requiring the azimuth | direction and distance.

  The ultrasonic imaging apparatus 10 further includes an amplifying means 3 for amplifying a signal from the ultrasonic array sensor 2 and delay synthesis for delay synthesis and AD conversion of the signal to calculate a distance for each direction and store it in a memory. Means 4, imaging means 5 for generating a distance image based on the stored data, image analysis means 8 for analyzing the moving direction and behavior of the imaged object based on the time change of the distance image, The peak signal extraction means 9 for extracting the distance and direction corresponding to the peak signal in the signal intensity distribution formed from the signal intensity and direction of the signal obtained by the delay synthesis means, and the imaging means 5 via the input / output unit 61 External notification means 6 for notifying the detection result of the object to the outside, image display means 7 for displaying an image, and a waveform generator 11 for causing the ultrasonic transmission means 1 to transmit ultrasonic waves are provided.

  Each signal of the ultrasonic receiving element 20 is amplified by the signal amplifying means 3, and a predetermined delay processing for each signal and synthesis of the delayed signals are performed for each direction by the analog delay synthesizer 41 in the delay synthesizing means 4. A process for obtaining one delayed composite signal for one azimuth is performed for each azimuth. The digital data processor 42 AD-converts the delayed composite signal obtained for each direction and calculates the digital data to obtain the distance (of the ultrasonic reflecting object) for each direction. The distance obtained for each azimuth and the signal strength of the delayed composite signal from which the distance is obtained are stored in the frame memory 43.

  The imaging unit 5 associates the azimuth with each pixel of the two-dimensional map of the X direction pixel number and the Y direction pixel number set based on the directivity and the viewing angle of the ultrasonic array sensor 2, and stores them in the frame memory 43. A distance image for displaying the distance in gray on each pixel is generated. Further, the imaging means 5 uses the distance obtained for each azimuth as it is as a distance image, and also displays the distance and the azimuth corresponding to the peak signal obtained by the peak signal extraction means 9 in a two-dimensional map in grayscale. Is generated. The distance and direction corresponding to the peak signal are obtained by the peak signal extraction means 9 based on the distance for each direction stored in the frame memory 43 and the signal strength of the delayed composite signal from which the distance is obtained. The generation of the distance image is performed by the control unit 51 of the imaging unit 5 based on a program stored in the ROM 52 or the RAM 53.

  The imaging unit 5 includes an image analysis unit 8 that analyzes the behavior of the detected and imaged object based on the temporal change of the distance image. The result obtained by the image analysis means 8 is notified to the outside by the external notification means 6.

  FIG. 2 shows a cross section of the ultrasonic receiving element 20. The ultrasonic receiving element 20 is obtained by forming a ferroelectric PZT film having upper and lower electrodes made of Pt on a membrane portion 21 on a silicon substrate having a diaphragm structure such as an SOI (Silicon on Insulator) substrate. The silicon substrate is formed into a diaphragm shape by forming recesses 22 by anisotropic etching. When the pressure wave (ultrasonic wave) emitted from the ultrasonic wave transmitting means 1 is reflected on the object T on the membrane part 21, a minute voltage is generated by the piezoelectric effect of PZT (ferroelectric film). This voltage is extracted to the outside as a voltage signal waveform through Pt (platinum) electrodes provided on the upper and lower parts of the PZT. The ultrasonic receiving element 20 having such a configuration can be miniaturized and integrated, and is suitably used for the ultrasonic array sensor 2.

  FIGS. 3A, 3B, and 3C show the ultrasonic array sensor 2 in which the ultrasonic receiving element 20 described above is incorporated. The ultrasonic array sensor 2 is configured by mounting the ultrasonic receiving elements 20 using a package 25 or the like and forming an array in a cross shape. The ultrasonic array sensor 2 is configured by arranging 5 elements in the X direction and 5 elements in the Y direction with one element as the center. As shown in FIG. 3C, the viewing angle α of each element is determined by the shape and size of the effective aperture desired by the membrane portion 21.

  Moreover, as shown in FIG. 4, the ultrasonic array sensor 2 in which the ultrasonic receiving elements 20 are two-dimensionally arranged at equal intervals can be used for generating a distance image. In this case, the number of elements can be selected according to the required angular resolution. In addition, it is possible to use ultrasonic receiving elements 20 arranged in an oblique matrix arrangement, a concentric arrangement, or an unequal interval arrangement.

  Here, the concept of electronic scanning (electronic scanning) using the ultrasonic array sensor 2 will be described with reference to FIG. In the electronic scan, the ultrasonic array sensor 2 is spatially fixed, and ultrasonic waves incident on the ultrasonic array sensor 2 from various directions are identified for each direction (referred to as an orientation) in the three-dimensional space. This is a method for acquiring the intensity of each received ultrasonic wave. The wavefront of the ultrasonic wave that reaches the ultrasonic array sensor 2 is treated as a plane within at least the reception surface of the ultrasonic array sensor 2. Therefore, as shown in FIG. 5A, the ultrasonic wavefront 2a coming from the front front N1 direction of the ultrasonic array sensor 2 is parallel to the receiving surface of the ultrasonic array sensor 2, and the ultrasonic array sensor 2 All the ultrasonic receiving elements 20 (not shown) arranged on the receiving surface simultaneously receive ultrasonic waves.

  Then, as shown in FIG. 5B, the ultrasonic wavefront 2 a coming from the direction N <b> 2 swung from the front N <b> 1 to the right (X direction) by the angle φ is an ultrasonic array sensor in the right half of the ultrasonic array sensor 2. It arrives earlier than the center of, and arrives late in the left half. Therefore, by performing an operation for correcting such a wavefront advance time and delay time on a signal output by receiving an ultrasonic wave with time by each ultrasonic receiving element 20, all the ultrasonic receiving elements 20 have the same effect. Time correction can be performed as if ultrasonic waves based on the wavefront at the same position were received at the same time. Therefore, when the signals subjected to time correction of the respective ultrasonic receiving elements 20 are added, a so-called delayed addition signal is obtained. From the position (t = t1) of the peak of the signal intensity appearing in the time-varying signal obtained by delay addition, the distance of the reflecting surface of the ultrasonic reflecting object existing in the direction N2 is obtained. If the origin of the time axis of the signal (t = 0) is the time when the ultrasonic wave is transmitted from the ultrasonic wave transmitting means 1 and the speed of sound is V, the distance Z is Z = It also stops at V · t1 / 2.

  Further, as shown in FIGS. 5C and 5D, with respect to the reflected ultrasonic wave coming from the direction N3 that is swung by the angle θ in the upper front direction (Y direction), or generally from φ to the right and the direction N4 swung upward to θ. However, based on the position where each ultrasonic receiving element 20 is arranged on the receiving surface of the ultrasonic array sensor 2 and the angles φ and θ, the signal delay time (with positive and negative) is corrected for each received signal. By adding the received signals, the distance of the ultrasonic reflecting object in an arbitrary direction can be obtained.

  Next, the directivity of the ultrasonic array sensor 2 will be described with reference to FIG. An ultrasonic reflection object T isolated at a predetermined distance in front of the ultrasonic array sensor 2 is disposed, transmits ultrasonic waves forward, and performs an electronic scan in the X direction, for example, by the ultrasonic array sensor 2, as shown in FIG. Directivity data in the X direction as shown is obtained. Since the ultrasonic array sensor 2 is symmetrical with respect to the X direction and the Y direction, the same directivity can be obtained in both directions. From this directivity graph, the angular resolution δ of the ultrasonic array sensor 2 is determined. In this characteristic chart of directivity, the horizontal axis represents the scanning angle φ, and the vertical axis represents the relative sensitivity of the sensor. The scanning angle φ is a scanning angle when the reception signal is electronically scanned in the X direction, for example, with the front direction of the ultrasonic array sensor 2 as the angle zero (for electronic scanning, the above-mentioned and, for example, Patent Document 1). reference).

  The angular resolution δ can be defined as an angle at which the relative sensitivity is reduced by 0.3 dB, for example. A curve a in FIG. 6 indicates the directivity of the ultrasonic array sensor 2 described above, and can be read as δ = 5 °. In the case of 4 elements, the angular resolution is about 7 ° from the curve b. The angular resolution can be increased by increasing the number of ultrasonic receiving elements constituting the array. Accordingly, it is possible to reduce the number of elements in the X and Y directions to 9 elements in advance and appropriately reduce to 7 elements, 5 elements, and 3 elements according to the usage situation. When the number of elements is reduced, the amount of calculation for delay synthesis and imaging can be reduced, and real-time performance is improved.

  Next, an imaging method for generating a distance image will be described with reference to the flowchart of FIG. Here, the case where the ultrasonic array sensor 2 (FIG. 3) with five ultrasonic receiving elements in the X and Y directions is used will be described. Moreover, the above figure is referred suitably. Since this sensor is symmetric in the X and Y directions, the parameters appearing below are the same in the X and Y directions unless otherwise noted. First, in the delay addition step (S1), the reflected ultrasonic waves are received and the signals of the ultrasonic receiving elements 20 are delayed and added for each direction to obtain the distance of the ultrasonic reflecting object in each direction, and the delay addition is performed. Thus, the distance and direction corresponding to the peak signal in the signal intensity distribution formed from the signal intensity and the direction of the signal obtained in this manner are obtained.

  Subsequently, in the viewing angle setting step (S2), viewing angles α in the X direction and the Y direction are set. As the viewing angle α, a value smaller than the maximum value determined by the sensor geometry can be arbitrarily selected. For example, a smaller viewing angle is selected when zooming in a specific angle range. In this case, ± 45 ° from the front of the sensor, that is, α = 90 °.

  Subsequently, in the angular resolution setting step (S3), the angular resolutions in the X direction and the Y direction are determined based on the directivity of the ultrasonic array sensor. In this case, δ = 5 ° is set according to the result of FIG.

  Subsequently, in the pixel number setting step (S4), the number of pixels p in the X direction and the Y direction is obtained using the viewing angle α and the angular resolution δ described above. That is, the number of pixels p = 19 is obtained from p = (α / δ + 1) = (90 ° / 5 ° + 1). The total number of pixels is 19 × 19 = 361 pixels.

  Subsequently, in the distance image generation step (S5), a distance image is obtained in which the distance is displayed with the direction corresponding to each pixel of the two-dimensional map having the above-mentioned number of pixels two-dimensionally in the X and Y directions. It is done. As a display method of the distance image, grayscale display (grading) can be used for each pixel according to the grayscale scale according to the distance at which the object is detected. For example, near objects are bright and far objects are dark. By color display, for example, the vicinity may be warm and the distance may be cool.

  Of the above five steps, the viewing angle setting step (S2), the angular resolution setting step (S3), and the pixel number setting step (S4) may be performed at least once in the cycle of ultrasonic image generation. In addition, when an ultrasonic image is generated regularly or continuously and zooming up by changing the resolution, it is possible to dynamically handle these three steps as appropriate. .

  Next, a specific ultrasonic distance image will be described with reference to FIGS. FIG. 8 shows the presence of two objects T1 and T2 in the front (Z direction) field of view. In FIGS. 8 and 9, the X direction is the horizontal direction (horizontal direction), the Y direction is the vertical direction (vertical direction), The Z direction is the depth direction (forward distance). FIG. 9A shows an example of a three-dimensional distance image of two objects T1 and T2. Objects T1 and T2 existing in the vicinity of 15 ° to the left front and 20 ° to the right front are detected by the ultrasonic array sensor 2 and displayed as a three-dimensional image (distance image) having distance information in grayscale in FIG. 9A. Yes. The object T2 is detected farther than the object T1, and the farther object T2 is displayed darker. In the distance separation image, each angular resolution and the number of pixels are as described above.

  FIG. 9B shows an example of the reflected ultrasound signal intensity distribution based on the three-dimensional distance image shown in FIG. 9A for two angles θ = θ1 and θ2. These signal intensity distributions are two cross sections of the signal intensity distribution in the (X, Y) or (φ, θ) plane. In the distribution at each angle θ = θ1 and θ2, sections G1 and G2 in which portions with large signal intensity are concentrated corresponding to the objects T1 and T2 are recognized. These sections G1 and G2 are recognized as two peaks (groups) corresponding to the objects T1 and T2 in the (φ, θ) plane. When the maximum peak is extracted from these peaks, it is assumed that these are peak signals P1 and P2 in the graph shown in FIG. 9B, for example. The three-dimensional distance image shown in FIG. 9C is a distance image generated using the distance and direction corresponding to the peak signals P1 and P2 in the signal intensity distribution extracted as described above. In this example, the distance and direction corresponding to the maximum peak signal are generated as a distance image.

  Next, an advantage of generating a distance image based on the peak signal in the ultrasonic signal intensity distribution will be described with reference to FIGS. FIG. 10A shows an ultrasonic wave transmitting means 1, an ultrasonic array sensor 2 as a receiving means, and an isolated ultrasonic reflection object T. Under such a simple situation, when a reflected ultrasonic wave is received at a certain scanning angle φ and the signal is delayed and added, if the ultrasonic reflectance of the ultrasonic reflecting object T is high, FIG. The waveform of the signal intensity as shown in FIG. 10B is obtained, and the waveform of the signal intensity as shown in FIG. 10C with a low ultrasonic reflectivity of the ultrasonic reflecting object T is obtained (on the time axis). The distance of the ultrasonic reflecting object T is known from the position of the signal waveform).

  When the signal obtained by delay addition as described above is electronically scanned in the φ direction within the range of the viewing angle of the ultrasonic array sensor 2 and the peak value in the signal intensity waveform corresponding to each angle φ is graphed, FIG. (A) As shown in (b) (similar to the directivity graph shown in FIG. 6). When a threshold TH1 based on signal strength is used to determine whether or not to adopt the signal as a significant signal for each signal, the signal intensity signal shown in FIG. Sound wave signals are also discarded. Therefore, when the ultrasonic reflectance of the ultrasonic reflecting object T is high, the ultrasonic reflecting object T is displayed at a predetermined angle and distance as shown in FIG. When the rate is low, there is a problem that the ultrasonic reflecting object T is not displayed as shown in FIG. FIGS. 10C and 10D are distance images obtained by detecting the distance and direction of a specific two-dimensional plane in the front three-dimensional space, for example, a horizontal plane.

  In the above description, data whose signal intensity does not reach the threshold value TH1 is discarded. Therefore, instead of the threshold value TH1, when a threshold value TH2 (TH2 <TH1) corresponding to a small intensity signal is set as shown in FIGS. 12 (a) and 12 (b), it is shown in FIGS. 12 (c) and 12 (d). As described above, even when the signal intensity is low (the ultrasonic reflectivity is low), it is possible to display the ultrasonic reflection object T (in FIG. 12, two ultrasonic reflection objects T are close to each other). Is assumed). However, when the threshold value is lowered (threshold value TH1 → threshold value TH2), there are generally problems such as a decrease in angular resolution, noise mixing, and ghosting. For example, an object with a high reflectivity is an actual object. There is a problem in that it is recognized that it exists in a wider range than the width, and two adjacent objects cannot be distinguished.

  Therefore, in order to solve the above problem, a distance image is generated based on the peak signal in the ultrasonic signal intensity distribution instead of suppressing the occurrence of noise and ghost using a threshold based on the signal intensity. Then, as shown in FIGS. 13A and 13B, the peak signals P3, P4, P5, and P6 in the ultrasonic signal intensity distribution are irrespective of the intensity of the ultrasonic signal (the magnitude of the ultrasonic reflectance). As shown in FIGS. 13 (c) and 13 (d), even when the ultrasonic reflectance is high or low, it is not affected by the variation in reflectance, and noise and ghost are not generated. A distance image can be generated.

  Next, with reference to FIG. 14, FIG. 15, and FIG. 16, the moving direction and behavior of the object (person) T using the two-dimensional distance image by the ultrasonic imaging method and ultrasonic imaging apparatus 10 of the present invention. Explain the application of analysis. FIG. 14A shows a situation in which a distance image is generated by electronically scanning a walking person (ultrasonic reflection object) T from above and rearward using the ultrasonic imaging apparatus 10 incorporating an ultrasonic array sensor. Show. In performing this electronic scan, if the electronic scan is performed in a specific plane, a two-dimensional distance image can be generated, and the time for the electronic scan is divided into so-called time sharing. Thus, a two-dimensional distance image on a plurality of planes can be generated, and a three-dimensional distance image can be generated by electronic scanning in all directions. Which distance image is to be generated can be selected dynamically (in real time) depending on the data processing capability of the ultrasonic imaging apparatus 10 and the cycle and situation of image generation.

  FIG. 14B shows an example of the generated two-dimensional distance image. This distance image is a distance image generated based on the peak signal in the ultrasonic signal intensity distribution as described above. According to such a distance image, a reflected ultrasonic wave from a part having a high ultrasonic reflectivity such as a head not covered with clothing or the like can be captured and the part can be regarded as a representative point of the person T. Then, the above-described image analysis means 8 analyzes the time change of the representative point appearing in the distance image to grasp the behavior of the person T, and based on the obtained result, the above-described external notification means 6 is used to alert the outside. Notifications can be handled.

  As an example of the image analysis described above, for example, as shown in FIG. 15A, a case where the person T is moving along the course R1 will be described. As shown in FIG. 15B, it is assumed that a two-dimensional distance image based on the above-described peak signal is generated, and the cycle of image generation is performed, for example, at intervals of 0.3 ms. This image generation is synchronized by the ultrasonic waves transmitted intermittently by the ultrasonic transmission means 1. In addition, the period of ultrasonic transmission is shortened when the person T is being detected, and is increased when the person T is not being detected.

The data of the position and direction of the object obtained in this way are accumulated in the frame memory 43 as continuous frames and displayed on the image display means 7 as a superimposed image as shown in FIG. Then, the moving direction of the person can be estimated from such a distance image having time lapse information . How the person T is moving, for example, only passing along the route R1 as shown in FIGS. 15 (a) and 15 (b), or FIGS. 16 (a) and 16 (b). As shown in FIG. 4, when it is determined that the person is trying to approach or intrude along the route R2, and it is determined that the person is a suspicious person trying to enter, external notification means 6 (incorporated in the ultrasonic imaging apparatus 10) An alarm can be issued using (not shown). Such estimation of the courses R1 and R2 can be automatically performed by the image analysis means 8 (not shown) of the ultrasonic imaging apparatus 10, and can also be performed based on the judgment of the user who observes the distance image. . The present invention is not limited to the above-described configuration, and various modifications can be made.

1 is a block configuration diagram of an ultrasonic imaging apparatus according to an embodiment of the present invention. Sectional drawing of the ultrasonic receiving element used with an imaging apparatus same as the above. (A) is a top view of the supersonic array sensor used with the imaging apparatus same as above, (b) is AA sectional drawing in (a), (c) is B section detailed sectional drawing in (b). The top view which shows the other example of the ultrasonic array sensor used with an imaging apparatus same as the above. (A)-(d) is a conceptual diagram of the ultrasonic array sensor explaining the electronic scanning by the ultrasonic array sensor in an ultrasonic imaging apparatus same as the above. The directivity graph of the ultrasonic array sensor used with an imaging apparatus same as the above. The flowchart which shows the process in the ultrasonic imaging method which produces | generates the distance image which concerns on one Embodiment of this invention. Explanatory drawing of the viewing angle in an imaging method same as the above. (A) is a three-dimensional distance image obtained by the above imaging apparatus and imaging method, (b) is a graph showing an example of an ultrasonic reflection signal intensity distribution based on the distance image, and (c) is a graph. The figure which produced | generated the distance and direction corresponding to the peak signal in signal intensity distribution as a distance image. (A) is a relational diagram of ultrasonic transmitting means, receiving means, and ultrasonic reflecting object, and (b) and (c) are temporal changes in reflected ultrasonic signal intensity from an object with high and low ultrasonic reflectivity, respectively. Graph. (A) and (b) are signal intensity distribution diagrams when the signal intensity of reflected ultrasound is greater than and less than the threshold value, respectively, and (c) and (d) are two-dimensional distances corresponding to (a) and (b), respectively. image. (A) and (b) are signal intensity distribution diagrams when the signal intensity of reflected ultrasonic waves from two adjacent objects is smaller than a threshold value, and (c) and (d) are respectively shown in (a) and (b). Corresponding two-dimensional distance image. (A) and (b) are signal intensity distribution diagrams for explaining signal peaks when the signal intensity of reflected ultrasonic waves from two adjacent objects is large and small, and (c) and (d) are (a) and (b), respectively. The two-dimensional distance image by the imaging apparatus and the imaging method according to the present invention in which the distance and direction corresponding to the peak signal are imaged. (A) is a perspective view for explaining a situation of distance measurement for generating a two-dimensional distance image according to an embodiment of the present invention, and (b) is a two-dimensional distance image generated in (a). (A) and (b) are diagrams for explaining behavior analysis in an imaging method according to an embodiment of the present invention. (A) and (b) are figures explaining other examples of behavior analysis in the imaging method concerning one embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Ultrasonic transmission means 2 Ultrasonic array sensor 3 Amplification means 4 Delay synthetic | combination means 5 Imaging means 6 External notification means 7 Image display means 8 Image analysis means 9 Peak signal extraction means 10 Ultrasonic imaging apparatus 20 Ultrasonic receiving element α , Α2 Viewing angle δ, δ2 Angle resolution p, px, py Number of pixels T, T1, T2 Object P1-P6 Peak signal

Claims (8)

Using an ultrasonic array sensor formed by two-dimensionally arranging a plurality of ultrasonic receiving elements at predetermined intervals in the X and Y directions, the distance of the ultrasonic reflecting object in each front direction is obtained, and the distance image of the object An ultrasonic imaging method for generating
A delay addition step of obtaining a distance of the ultrasonic reflecting object by receiving a reflected ultrasonic wave from the front and delay-adding the signal of each ultrasonic receiving element for each direction;
A viewing angle setting step of setting viewing angles in the X direction and the Y direction from the center of the ultrasonic array sensor;
An angular resolution setting step for setting an angular resolution in the X direction and the Y direction from the directivity of the ultrasonic array sensor;
A pixel number setting step in which the numbers obtained by dividing the set viewing angles in the X direction and the Y direction by the angular resolutions in the X direction and the Y direction are respectively the X direction pixel number and the Y direction pixel number;
And an image generating step of generating a distance image in association with the orientation in each pixel of the two-dimensional map consisting of the X-direction pixel number and the Y-direction pixel number,
Generating a distance image in the image generation step using the distance and direction corresponding to the peak signal in the signal intensity distribution formed from the signal strength of the delay addition to obtained signals and said orientation at said delay adding step An ultrasonic imaging method characterized by the above.   The ultrasonic imaging method according to claim 1, wherein the distance image is generated by detecting a distance and a direction with respect to a specific two-dimensional plane in the front three-dimensional space.   The ultrasonic imaging method according to claim 2, wherein the delay adding step is time-divided to generate a plurality of the distance images.   4. The ultrasonic imaging method according to claim 1, wherein a distance and a direction corresponding to the maximum peak signal among a plurality of peak signals are generated as a distance image.   5. The method according to claim 1, wherein the distance and direction of the ultrasonic reflecting object are detected in time series and are continuously displayed on the distance image so that the moving direction of the ultrasonic reflecting object can be estimated. An ultrasonic imaging method according to claim 1.   6. The ultrasonic imaging method according to claim 5, wherein an interval for obtaining the distance of the ultrasonic reflection object is changed depending on whether the ultrasonic reflection object is recognized or not. And an ultrasonic array sensor formed by two-dimensionally arranging a plurality of ultrasonic receiving elements at predetermined intervals in the X direction and the Y direction, and the ultrasonic waves transmitted from the ultrasonic transmitting means An ultrasonic imaging apparatus that receives reflected ultrasonic waves reflected by an object by the ultrasonic array sensor, obtains an orientation and a distance of the object, and generates a distance image of the object,
Signal amplifying means for amplifying the signal of the ultrasonic receiving element;
Delay synthesis means for delay-synthesizing and AD-converting each signal amplified by the signal amplifying means, calculating a distance for each direction, and storing it in a memory;
Peak signal extraction means for extracting the distance and azimuth corresponding to the peak signal in the signal intensity distribution formed from the signal intensity and azimuth of the signal obtained by the delay synthesis means;
An azimuth is made to correspond to each pixel of the two-dimensional map of the X direction pixel number and the Y direction pixel number set based on the directivity and the viewing angle of the ultrasonic array sensor, and the distance and the azimuth corresponding to the peak signal are used. An ultrasonic imaging apparatus comprising: an imaging unit that generates a distance image. Image analysis means for analyzing the moving direction and behavior of the imaged object based on the time change of the distance image;
The ultrasonic imaging apparatus according to claim 7, further comprising an external notification unit that notifies the result obtained by the image analysis unit to the outside.

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