JP2000019243A - Ultrasonic sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress a side lobe and to sharpen the wave transmitting-receiving direction characteristic in an ultrasonic sensor which is used for crime prevention or the like. SOLUTION: An ultrasonic vibrator T for wave transmission and an ultrasonic vibrator R for wave reception are arranged at a reflector 10 so as to have an orthogonal relationship. Ultrasonic waves which are outputted from the ultrasonic vibrator T for wave transmission are reflected in a region T so as to be wave-transmitted in the direction to a main sensor. Ultrasonic waves which are reflected by a reflecting object Q are reflected in a region R so as to be wave-received by the ultrasonic vibrator R for wave reception. The beam cross section of a wave transmitting beam and that of a wave receiving beam are flat, and both beam overlap each other partially by using their beam axis as the center. Thereby, when both beams are integrated as a result, a sharp wave transmitting-receiving direction characteristic is obtained. In addition, a side lobe is reduced. A composite sensor can be constituted by combining an ultrasonic sensor with an infrared sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic sensor, and more particularly to improvement of directivity in an ultrasonic sensor for detecting an object by transmitting and receiving ultrasonic waves.

[0002]

2. Description of the Related Art An ultrasonic sensor is a sensor for detecting, for example, the presence or absence of a person and the location of a person by transmitting and receiving ultrasonic waves in the air. It is used in ordinary households, offices, public facilities, and the like as an object detection sensor, security occupant search sensor, intrusion detection sensor, and the like.

[0003] In such an ultrasonic sensor, an ultrasonic pulse is generally transmitted, and a reflected wave from a detection target is received. In order to improve detection accuracy in transmitting and receiving waves, it is necessary to transmit and receive ultrasonic waves only in the detection direction corresponding to the main sensor direction, and to prevent transmission and reception of ultrasonic waves in other directions. This is to eliminate erroneous detections caused by surrounding obstacles and the like. For this reason, there is a need to control the directivity of the ultrasonic beam by some method so that the ultrasonic wave is transmitted and received only in a required direction.

A typical technique for controlling the directivity of an ultrasonic wave includes an acoustic horn and a reflector. In the case of the former acoustic horn, sidelobes do not disappear in theory even if narrow directivity can be achieved. The level of the side lobe is only several tens dB lower than the main lobe. For this reason, even if a narrow directivity can be realized for the main lobe, there is a possibility that an erroneous detection due to a surrounding obstacle may occur due to the influence of the side lobe. In contrast, when using the latter reflector, an ultrasonic element is arranged at the focal position of the parabolic reflector,
Transmission / reception is performed using the reflection and convergence of the ultrasonic wave at the reflector. However, it is known that a side lobe similar to that of a horn is generated by simply using a reflector.

[0005] By the way, conventionally, there is also known a method of forming a transmission directivity characteristic and a reception directivity characteristic different from each other and combining them to thereby improve the directivity of the main detection direction. However, when this method is applied to an ultrasonic sensor for detecting a human body, it becomes difficult to configure an asymmetrical transducer, and there is a problem that the sensor becomes particularly large when incorporated into the sensor. For example,
Regarding the ultrasonic sensor for security use, the size limit cannot be ignored due to aesthetic reasons. Further, in the case of forming a composite sensor combining an ultrasonic sensor and another sensor in order to improve the sensor performance, the problem of the size becomes particularly significant. For this reason, when a small-sized horn or the like is used, a large side lobe is generated.
Eventually, the combination of an acoustic tube and a horn to achieve a desired performance is actually performed.

However, in the case of a method of combining an acoustic tube and a horn, theoretical analysis is not easy. For this reason, it can only be manufactured by trial and error, and a great deal of labor and cost are required for design and manufacture. Moreover, when actually manufactured, desired performance cannot be obtained in most cases. Such a tendency is similarly observed in a system other than the horn, and it is a reality that the system is designed with the expectation that a high performance device will be obtained by chance. In the end, new designs are practically difficult and have so far had to rely on the few heuristically created horns. This has been a major constraint on the development of new sensors.

[0007] Japanese Patent Publication No. 54-2112, Japanese Patent Application Laid-Open No. 2-238881, and Japanese Utility Model Publication No. 5-33984 disclose techniques related to the present invention. No ultrasonic sensor is disclosed that meets the purpose of the present invention.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to provide an ultrasonic sensor capable of improving directivity with few side lobes and suitable for miniaturization.

Another object of the present invention is to provide an ultrasonic sensor which is easy to design and is particularly suitable for detecting a human body.

[0010]

Means for Solving the Problems (1) In order to achieve the above object, the present invention comprises a transmitting element and a transmitting reflecting section for reflecting ultrasonic waves from the transmitting element. A wave transmitting means for forming a flat transmitting beam having a beam cross section orthogonal to the azimuth, and a wave receiving element and a wave receiving reflector for reflecting ultrasonic waves toward the wave receiving element. Receiving means for forming a receiving beam having a flattened beam cross section orthogonal to the transmitting beam, wherein the transmitting beam and the receiving beam partially overlap each other around the sensor main direction.

According to the above configuration, the pattern of the transmission beam formed by the transmission means (transmission directivity) and the pattern of the reception beam formed by the reception means (wave reception directivity) correspond to the sensor main direction. (Beam axis) is partially overlapped, so if the transmitting and receiving of the ultrasonic wave is performed using the transmitting and receiving means, as a result, their directional characteristics are synthesized, and the side lobe is reduced. It is possible to form a transmitting and receiving beam having a sharp directivity in the sensor main azimuth direction while reducing the size. In particular,
The wave transmitting means and the wave receiving means use a reflection part, and a small or thin ultrasonic sensor can be configured. Note that the flat beam cross section is formed by unevenly distributing acoustic power in a plane orthogonal to the beam axis, and its form includes an elliptical shape and other non-circular shapes.

(2) Preferably, the reflection part for transmitting wave and the reflection part for receiving wave are set on a single concave reflector. According to this configuration, there is an advantage that the size of the sensor can be further reduced, and since the fixing and positioning of the transmitting element and the receiving element can be simplified, the adjustment of the directional characteristics is easy.

Preferably, the wave transmitting element and the wave receiving element are displaced from the center of the concave reflector and are arranged toward different transmitting reflection center points and different receiving reflection center points. Preferably, the wave transmitting element and the wave receiving element are arranged toward the transmission reflection center point and the reception reflection center point, respectively, while passing through the focal point of the concave reflector. More preferably, the wave transmitting element and the wave receiving element are arranged orthogonally when viewed from the sensor main azimuth direction.

[0014] The wave transmitting reflecting portion and the wave receiving reflecting portion may be respectively constituted by separate concave reflectors.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, the principle of the embodiment will be described.
This will be described with reference to the drawings.

FIG. 1 shows the configuration of the wave transmitting section in the ultrasonic sensor. As shown in the figure, an ultrasonic transducer 12 is installed inside a parabolic reflector 10, and an ultrasonic wave is transmitted. Specifically, in this example, the ultrasonic vibrator 12
Is set in the vicinity of the focal point P of the parabola, from which the ultrasonic wave 100 is emitted in parallel with the y-axis. The ultrasonic wave 1
When 00 is irradiated on the surface of the reflector 10 while passing through the focal point P of the reflector 10, the reflected ultrasonic waves 102 are emitted in the Z-axis direction. Incidentally, in FIG. 1, the center of the reflection region irradiated with the ultrasonic wave is indicated by K. In this example, the direction of the ultrasonic wave 100 is made parallel to the y-axis and passes through the focal point P. However, other configurations can be adopted. Note that the z-axis coincides with the sensor main direction, and the x-axis and the y-axis are axes orthogonal to the z-axis.

FIG. 2 shows a virtual transmission beam pattern in the case where transmission is performed using the configuration of the transmission section shown in FIG. That is, when the ultrasonic sensor has a structure as shown in FIG. 1, the pattern (directivity) of the transmitted beam has a flat beam cross section orthogonal to the beam axis as shown in FIG. Specifically, the power distribution on the xy plane is elliptical as shown by the hatched portion in the figure, narrow in the x-axis direction, and wide in the y-axis direction. Notable features include the fact that, in the case of such a structure, the directivity in the x direction is very narrow and the side lobe is very small as compared with a case where a simple acoustic horn is used. . Note that point F indicates a sensor center point, and point S indicates an observation point in the main direction.

FIG. 3 shows a virtual reception in a case where the structure shown in FIG. 1 is rotated by 90 degrees on the xy plane to form a wave receiving unit and receives an ultrasonic wave coming from the outside. The beam pattern is shown. In this case, since the ultrasonic vibrator operates as a reversible electro-acoustic transducer, the shape of the beam pattern is exactly the same as in the case of transmitting waves (FIG. 2). However, the directional characteristic at the time of reception in FIG. 3 is rotated by 90 degrees with respect to the directional characteristic at the time of transmission in FIG.

FIG. 4 shows a transmitted / received beam pattern in a case where the above-described configuration of the transmitting section and the configuration of the receiving section are combined. As shown in the figure, as a result of the product of the directional characteristics of each other, that is, their integration, a sharp directional characteristic can be obtained in the z direction, and side lobes can be effectively suppressed over the entire region in the direction orthogonal to the z direction.

In the above example, the transmitting unit and the receiving unit are configured to be orthogonal to each other. However, the point is that the directional characteristics at the time of transmitting and the directional characteristics at the time of receiving are different from each other for integration. In, various applications are possible. For example, if the product of the two (the area of the hatched portion in FIG. 4) may be slightly widened, it is not always necessary to make them orthogonal, and the intersection angle can be set as appropriate.

Next, a preferred embodiment to which the above principle is applied will be described.

FIG. 5 shows the configuration of the first embodiment of the ultrasonic sensor according to the present invention. (A) is a front view of the ultrasonic sensor, and (B) is a side sectional view. In this embodiment, the ultrasonic sensor is composed of a single parabolic reflector 10 and an ultrasonic transducer T dedicated for transmitting and an ultrasonic transducer R dedicated for receiving, which are disposed inside the reflector 10 in directions orthogonal to each other. And

The reflector 10 is similar to that shown in FIG. 1 and has a concave shape, specifically a parabolic shape.
The reflector 10 is made of a member suitable for reflecting ultrasonic waves, for example, a resin. The size can be appropriately selected depending on the application and performance, but has a diameter of, for example, more than ten cm.

The ultrasonic transducers T and R are composed of the same transducer, and transmit and receive, for example, an ultrasonic pulse of 40 kHz. The frequency of the ultrasonic wave can be appropriately set according to the application and the like, and the vibrator is selected accordingly. Although it is possible to provide an acoustic lens or the like on the front surface of the ultrasonic transducers T and R, such a member is not required if the convergence of the reflector 10 is sufficient. In the present embodiment, as the ultrasonic transducers T and R, those in which a piezoelectric body is packaged in a cylindrical plastic case are used.

As shown in FIG. 5, the ultrasonic transducers T and R are arranged orthogonally in a plane orthogonal to the main direction of the sensor, and the path of the transmitted ultrasonic wave before reflection and the path of the received ultrasonic wave after reflection. Intersect at the focal point of the reflector 10, and the transmitted ultrasonic wave and the received ultrasonic wave are reflected on the reflector 10 at a region T200 and a region R202, respectively. Specifically, as shown also in FIG. 5, the transmitted ultrasonic wave emitted from the ultrasonic transducer T is applied to the region T20.
The light is reflected at 0 and transmitted toward the main sensor direction.
When the ultrasonic wave is reflected by the reflecting object Q, the reflected wave is reflected by the region R202, and is received by the ultrasonic transducer R as the received ultrasonic wave. As a result, it is possible to obtain the directional characteristics related to the transmission and reception as shown in FIG. In addition, code 20
Reference numerals 4 and 206 represent the centers (reflection center points) of the regions T200 and R202, respectively.

As described above, the region T200 and the region R202
Function as a reflecting portion, and each can be configured as a separate reflecting plate. However, in consideration of easiness of positioning, reduction in the number of parts, and the like, a single unit as in the first embodiment is used. It is desirable to make the reflector 10 function substantially as a transmitting reflector and a receiving reflector. In addition, if two ultrasonic transducers T and R are provided on a single reflector 10, a part of the space of the concave portion is used as a place for disposing the ultrasonic transducer to reduce the thickness of the ultrasonic sensor. There is an advantage that it can be made thin.

In the above method, the reflector 1 having a parabolic shape is used.
Since 0 is used, the gain can be improved as compared with the case where the vibrator is used alone. Here, the gain depends on the area of the region T200 during transmission, and depends on the area of the region R202 during reception. In short, the larger the area, the greater the gain. Therefore, it is desirable to determine the size of the reflector 10 according to the use of the ultrasonic sensor.

In the above embodiment, the shape of the reflector 10 can be changed or cut out at least in the region other than the region where the ultrasonic wave is reflected. When three-dimensional scanning is performed with an ultrasonic beam, a method of changing the positional relationship between each of the ultrasonic transducers T and R and the reflector 10 or tilting or rotating the ultrasonic sensor itself is used. Applicable.

As described above, in the conventional ultrasonic sensor using the reflector, the design has been made so that symmetry and uniformity can be obtained in a plane perpendicular to the main sensor direction. According to the present embodiment, the positions and directions of the transmission and reception waves are positively displaced to form a directional characteristic having a flat beam cross section, and a sharp transmission / reception beam can be formed as an integral of them, and the sidelobe Can be effectively suppressed.

In particular, according to the above embodiment, the adjustment of the directional characteristics generally requires only adjustment of the position of the ultrasonic vibrator, and a certain degree of directional characteristics is obtained even if the position of the ultrasonic vibrator is slightly shifted. Since it is easily obtained, the labor for redesigning the entire ultrasonic sensor and the labor for adjustment can be greatly reduced.

Next, a second embodiment will be described.

Although the embodiment shown in FIG. 5 is of the "single reflector type", in such an ultrasonic sensor, the two regions T on the reflector substantially reflect the ultrasonic waves.
200 and R202. Therefore, it is not necessary to integrate the reflection means for transmitting and receiving waves into an integrated type.
It is possible to use a shape that matches the shape of the region 200 or the region R202.

The second embodiment shown in FIG. 7 is an ultrasonic sensor designed based on the above idea. (A) is a front view of the ultrasonic sensor, and (B) is a side view of the ultrasonic sensor. In FIG. 7, the ultrasonic sensor includes two reflectors 20 and 22 and two ultrasonic transducers T and R. The ultrasonic transducers T and R are arranged orthogonally in the same manner as the embodiment shown in FIG. 5, but in this embodiment, the reflector 20 functions as a reflector dedicated to transmitting waves, 22 functions as a reflector exclusively for receiving waves. That is,
The ultrasonic transducer T and the reflector 20 constitute a wave transmitting unit, and the ultrasonic transducer R and the reflector 22 constitute a wave receiving unit. According to this embodiment, there is an advantage that the amount of the reflector can be reduced, and an advantage in arrangement space can be obtained.

In designing the reflector, the portion where the ultrasonic wave does not directly hit can be made to have a relatively free shape as long as acoustic diffuse reflection does not occur. If acoustic diffuse reflection occurs, reverberation components appear to increase when a received waveform is observed. Conversely, if the received waveform is observed and the reverberation component does not increase, the surrounding shape other than the reflector can be freely designed.

FIG. 8 shows a modification of the second embodiment which is a "reflector separated type".

In the configuration shown in FIG. 7, the reflector 10
The ultrasonic transducers T and R are arranged such that the transmitted ultrasonic wave before reflection and the received ultrasonic wave after reflection intersect at the focal position. However, this is not essentially a required condition, and it is possible to arrange as shown in FIG. That is, in the embodiment of FIG. 8, the wave transmitting unit (the ultrasonic vibrator T,
Reflector 20) and wave receiving unit (ultrasonic transducer R, reflector 2)
Although the orthogonal arrangement relationship of 2) is maintained, the ultrasonic paths do not intersect. According to such a configuration, although the entire ultrasonic sensor becomes large, there is an advantage that the signal accuracy can be improved by widening the aperture for transmitting and receiving waves.

In any case, according to each of the above embodiments, there is no particular restriction other than the restriction of the orthogonal relationship between the transmitting part and the receiving part.
A highly flexible sensor design can be realized.

Next, a composite sensor to which the present invention is applied will be described.

FIGS. 9 to 11 show an example of a composite sensor. FIG. 9 is a sectional view of the composite sensor, and FIG.
0 is a perspective view, and FIG. 11 is a front view.

In FIG. 9, the composite sensor is a combination of an ultrasonic sensor and an infrared sensor, and is used, for example, for crime prevention. A back plate 33 is provided on the back surface of the cylindrical case 32, and a protection net 31 is provided on the front surface thereof. Inside the case 32,
An ultrasonic sensor and an infrared sensor are provided. The protection net 31 is preferably made of a member that can transmit infrared rays, for example, polyethylene.

Specifically, the ultrasonic sensor is a case 32
A generally concave reflector 30 provided inside the
It comprises a pair of transmitting and receiving ultrasonic vibrators T and R fixed to the vibrator mounting portion 40 of the reflector 30. The infrared sensor is composed of a light receiving element 48 provided at the back of the center of the reflector 30 and a Fresnel lens 34 forming the center of the reflector 30. The light receiving element 48 is provided on a substrate 46, and the substrate 46 and each of the ultrasonic transducers T and R are electrically connected by a signal line 42.

The Fresnel lens 34 has a light transmitting function and a light condensing function, and may be formed of a different member from the reflector 30 itself, or may be formed of the same member. However, it is desirable that the Fresnel lens 34 is formed in a region other than the region where the ultrasonic wave is reflected so as not to disturb the directivity. FIG. 12 shows a state in which infrared rays are detected by the light receiving element 48 via the Fresnel lens, where (A) is a schematic front view and (B) is a schematic side sectional view. .

As shown in FIGS. 9 and 12, the ultrasonic sensor has basically the same form as the embodiment shown in FIG. 5, and as described above, a pair of ultrasonic transducers T and R are arranged orthogonally, and the combination of directional characteristics having asymmetry is realized.

FIG. 13 shows another example of the composite sensor. In this example, all or a part of the reflector 50 is made of a material that transmits infrared light of a specific wavelength. The infrared light transmitted through the reflector 50 is reflected by the mirror 54 and received by the light receiving element 52. Note that polyethylene or the like can be used as a material that allows infrared rays to pass therethrough. When an infrared ray is transmitted through the acoustic horn, if the angle between the surface of the horn and the incident direction of the infrared ray becomes small, the transmittance of the infrared ray deteriorates. In the example of FIG. There is an advantage that can be taken large.

As described above, according to the embodiment of the present invention, it is possible to configure an ultrasonic sensor having sharp directivity and having a very small side lobe. For this reason, when such an ultrasonic sensor is used as an object detection sensor or an intrusion sensor, the boundary between the detection area and the non-detection area can be clarified, and the detection accuracy can be improved. Further, since the gain is increased as compared with the element alone, the S / N is improved.

Another feature of the present embodiment is that design and manufacture are easy. Although performance can be improved by utilizing the acoustic interference effect in ultrasonic sensors using acoustic horns, designs that take such acoustic interference into account are usually extremely difficult, and experimental Unless verified, it is difficult to design reliably.

On the other hand, according to the above embodiment, such an acoustic interference is not used, and in the present embodiment, only the ultrasonic wave reflection phenomenon is used. The concept of design can be applied. That is, the interference effect depends on the wavelength of the ultrasonic wave to be used, but the reflection phenomenon can be designed without depending on the wavelength. This means that the number of parameters (wavelengths) to be considered is one less, which means that it is easier to design on a desk.

In the above embodiment, it is only required that the reflection be performed accurately, and the degree of freedom of the shape of the reflector and the arrangement of the elements is very large. For this reason, the acoustic design of the ultrasonic wave has conventionally imposed various restrictions on other designs, but many restrictions have been relaxed. Further, the number of unknown points that cannot be understood without trial and error is reduced, and the merit in terms of labor and cost required for design is great.

When applied as an intrusion detection sensor for security, a horn length is conventionally required to some extent, so that the height of the sensor tends to increase. For this reason, it often became an aesthetic problem. On the other hand, according to the present embodiment, the height can be reduced to about half of the horn. However, a certain size is required in the diameter direction, but this is not enough to increase the diameter of a general sensor.

In the case of configuring a composite sensor, when using a horn, the optical design tends to be difficult. On the other hand, if the above embodiment is applied, there is a degree of freedom in both optical design and acoustic design, and it is possible to design a small and low-cost sensor.

[0051]

As described above, according to the present invention,
It is possible to provide an ultrasonic sensor which can improve directivity with few side lobes and is suitable for miniaturization.

[Brief description of the drawings]

FIG. 1 is a diagram showing transmission of an ultrasonic wave using a reflector.

FIG. 2 is a diagram illustrating an example of an asymmetric transmission directivity characteristic.

FIG. 3 is a diagram showing a reception directivity obtained by rotating the directivity of FIG. 2 by 90 degrees.

FIG. 4 is a diagram showing directional characteristics obtained by integrating the directional characteristics of FIGS. 2 and 3;

FIG. 5 is a diagram showing a configuration of an embodiment according to the present invention.

FIG. 6 is a diagram showing the operation of the configuration shown in FIG. 5;

FIG. 7 is a diagram illustrating a configuration of another embodiment.

FIG. 8 is a diagram illustrating a configuration of another embodiment.

FIG. 9 is a diagram illustrating a configuration example of a composite sensor.

FIG. 10 is a perspective view of a composite sensor.

FIG. 11 is a front view of the composite sensor.

FIG. 12 is a diagram for explaining the operation of the composite sensor.

FIG. 13 is a diagram showing another example of the composite sensor.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Oizumi 6-11-23 Shimorenjaku, Mitaka City, Tokyo Inside Secom Co., Ltd. (72) Keita Shimozawa 6-11-23 Shimorenjaku, Mitaka City, Tokyo Secom F term in the company (reference) 5J083 AA02 AB12 AB15 AC03 AC15 AC31 AE08 AG05 CA01 CA02 CA18 CA20 CA35

Claims (6)

[Claims] A transmitting unit configured to form a transmitting beam having a flattened beam cross-section orthogonal to a main direction of a sensor, the transmitting unit comprising a transmitting element and a transmitting reflection unit that reflects ultrasonic waves from the transmitting element; A wave receiving means comprising a wave receiving element and a wave receiving reflector for reflecting ultrasonic waves toward the wave receiving element, and forming a wave receiving beam having a flat beam section orthogonal to the sensor main direction. The ultrasonic sensor according to claim 1, wherein the transmitting beam and the receiving beam partially overlap each other around the sensor main direction. 2. The ultrasonic sensor according to claim 1, wherein the reflection part for transmitting waves and the reflection part for receiving waves are set on a single concave reflector. 3. The ultrasonic sensor according to claim 2, wherein the wave transmitting element and the wave receiving element are displaced from the center of the concave reflector and are different from each other in the transmission reflection center point and the reception reflection center point. An ultrasonic sensor, wherein the ultrasonic sensor is arranged to face. 4. The ultrasonic sensor according to claim 3, wherein the transmitting element and the receiving element pass through the focal point of the concave reflector, respectively, while the transmitting reflection center point and the receiving reflection center are located. An ultrasonic sensor characterized by being arranged toward a point. 5. The ultrasonic sensor according to claim 4, wherein the transmitting element and the receiving element are arranged such that directions of the transmitting beam and the receiving beam are orthogonal to each other when viewed from a main azimuth direction of the sensor. An ultrasonic sensor characterized by being performed. 6. The ultrasonic sensor according to claim 1, wherein the wave transmitting reflecting portion and the wave receiving reflecting portion are each configured by a separate concave reflector.