JP4802730B2 - Object detection device - Google Patents

Description

  The present invention relates to an object detection apparatus that transmits ultrasonic waves and detects an object using reflected ultrasonic waves.

  Conventionally, an object detection apparatus that transmits ultrasonic pulses to a target detection region and detects an ultrasonic reflection object in the detection region from time information of the reflected ultrasonic pulse has been used. Such an object inspection device is used, for example, for obstacle detection in front of a moving direction of a vehicle or a mobile robot, intruder detection for crime prevention, or the like. The ultrasonic transmitter and receiver can be shared, but when performing object detection repeatedly in a short time, for example, to avoid the effects of reverberation, the transmitter and receiver are A separate one is used. Further, the receiver is composed of a plurality of receiving elements, and the direction of the detected object is obtained from the time difference of the received signals between the receiving elements.

  In object detection using ultrasonic waves as described above, when a ghost signal due to noise, that is, a signal that is not an actual detection signal, is generated, there is a possibility that false detection for detecting an object that does not exist in the detection region may occur. . Since false detection reduces the convenience of object detection, it needs to be eliminated. Such erroneous detection can be suppressed, for example, by increasing the ratio of signal intensity to noise intensity, that is, the S / N ratio. When attention is paid to the signal intensity, the intensity of the ultrasonic wave to be transmitted may be increased in order to increase the signal intensity from the reflected ultrasonic wave. In order to increase the intensity of the ultrasonic wave to be transmitted, there are, for example, a method of enhancing the ultrasonic wave transmission circuit and a method of increasing the directivity of the ultrasonic wave to be transmitted and increasing the ultrasonic intensity in a specific visual field range. The former method for strengthening the ultrasonic wave transmission circuit has a problem that the circuit is complicated and large, and the cost is increased.

As the latter method described above, there is known an example in which an ultrasonic lens is used in a medical ultrasonic probe or an ultrasonic detection type catheter in order to improve the directivity of ultrasonic waves to be transmitted (see, for example, Patent Document 1). ).
JP-A-2-302251

  However, as shown in Patent Document 1 described above, the method of simply increasing the directivity and increasing the S / N ratio by using an ultrasonic lens is capable of detecting an object (obstacle or intruder) in a detection area with a wide field of view. There is a problem that you can not.

  The present invention solves the above-described problem, and can increase the S / N ratio without increasing the ultrasonic transmission circuit in a wide visual field detection region and detect the distance and orientation of an object while suppressing erroneous detection. An object of the present invention is to provide an object detection apparatus using ultrasonic waves.

In order to achieve the above object, an invention according to claim 1 is directed to a transmitter for transmitting an ultrasonic wave to a detection region, and a reflected wave of the ultrasonic wave reflected by a measurement object in the detection region. A plurality of receiving elements that convert the ultrasonic waves into received signals that are electrical signals, and the time from when the ultrasonic waves are transmitted to when they are received based on the received signals of the receiving elements. A detection unit that detects a distance to the corresponding object to be measured and detects a direction of the object to be measured corresponding to a time difference between each received signal in each wave receiving element to detect the object to be measured. And provided with an ultrasonic lens that keeps or changes the direction of transmission when disposed in front of the transmitter, narrows the detection area , and increases the sound pressure of the transmitted ultrasonic wave, The detection unit is configured such that the ultrasonic lens is not disposed in front of the transmitter. Performs detection, then again in a state of being arranged in front of the transmitters of said ultrasonic lens so as to face the transmitting direction in the direction of the detected object, and performs object detection.

  According to a second aspect of the present invention, in the object detection device according to the first aspect, the ultrasonic lens comprises a refracting gas having a higher density than air and an outer container enclosing the refracting gas. is there.

  According to the first aspect of the present invention, object detection is performed in two stages, object detection with a wide field of view and object detection with a narrow field of view, and directivity is increased by the effect of the ultrasonic lens in object detection with a narrow field of view. Therefore, it is possible to increase the S / N ratio without increasing the ultrasonic transmission circuit, and to detect the distance and direction of the object while suppressing false detection in a detection area with a wide field of view. be able to.

  According to the invention of claim 2, it is possible to easily manufacture an ultrasonic lens that collects ultrasonic waves and increases directivity.

  Hereinafter, an object detection device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1A shows a state in which an ultrasonic lens is not disposed in front of the transmitter in the object detection apparatus according to an embodiment of the present invention, and FIG. The state which has arrange | positioned the ultrasonic lens is shown. This object detection apparatus receives a reflected wave of the ultrasonic wave reflected by the object to be measured in the detection area and a transmitter 1 that transmits the ultrasonic wave to the detection area, and converts the ultrasonic wave into an electric signal. A plurality of receiving elements 2 to be converted into a certain received signal, and an object to be measured corresponding to a time from when an ultrasonic wave is transmitted to when it is received based on the received signal of the receiving element 2 And a detector 3 that detects the object to be measured by obtaining the distance and obtaining the direction of the object to be measured corresponding to the time difference of each received signal in each wave receiving element 2.

  The object detection apparatus includes an ultrasonic lens 4 that can change the transmission direction when disposed in front of the wave transmitter 1 and can narrow the detection region. As shown in FIG. 1A, object detection is performed in a state where the ultrasonic lens 4 is not disposed in front of the transmitter 1, and thereafter, as shown in FIG. Object detection is performed again in a state where the ultrasonic lens 4 is disposed in front of the transmitter 1 so as to further improve the directivity of the ultrasonic wave to be transmitted.

  The object detection device of the present invention includes a switching mechanism (described later, FIGS. 3 and 4) for switching between the placement and non-placement of the ultrasonic lens 4 as described above. Is output to the switching mechanism to switch between the placement and non-placement of the ultrasonic lens 4. Further, the ultrasonic wave transmission direction can be changed by switching the ultrasonic lens 4. The object detection by changing the transmission direction will be described later. Hereinafter, each component and its operation will be described in detail.

  The above-described transmitter 1 includes a transmission circuit 10 and a transmission element 11. The transmission circuit 10 excites the transmission element 11 by outputting electric energy for transmission and an electrical signal as a transmission signal to the transmission element 11. The transmission element 11 receives electrical energy, converts a transmission signal into an air density wave, and transmits the air as an ultrasonic wave in the air.

  The plurality of wave receiving elements 2 are arranged close to each other and in a line in the same plane. When reflected ultrasonic waves from a sufficiently far distance are incident on the plane formed by the receiving elements 2 arranged in this way, the reflected ultrasonic waves are incident as plane waves. Then, as is well known, the propagation direction of the reflected ultrasonic wave can be obtained from the angle formed by the wavefront of the reflected ultrasonic wave with respect to the plane formed by the wave receiving element 2. In other words, the propagation direction of the reflected ultrasonic wave is obtained from the arrangement interval of each receiving element 2 and the delay of each receiving time. Further, as is well known, the distance to the ultrasonic reflection object, that is, the object to be measured, can be obtained from the sound speed of the ultrasonic wave and the time required for reception by the wave receiving element 2. In this way, the object detection device can detect an ultrasonic reflection object. The plurality of receiving elements 2 are arranged close to each other in the same plane, for example, arranged in a row in a direction orthogonal to each other, arranged in a cross shape, or arranged in a two-dimensional array. Can also be used.

  The detection unit 3 performs a calculation for obtaining the propagation direction of the reflected ultrasonic wave, the direction of the measured object, and the distance to the measured object. In order to do this, the detection unit 3 receives an electric signal generated when each receiving element 2 receives an ultrasonic wave, and converts the time information of the electric signal and the geometric arrangement information of each receiving element 2. Based on this, the above-described calculation can be performed.

  Since the ultrasonic lens 4 narrows the detection area and increases the directivity of the ultrasonic wave transmitted by the transmitter 1, it is possible to increase the reach of the transmitted ultrasonic wave and increase the sound pressure. Such an ultrasonic lens 4 can be configured to include a refracting gas having a higher density than air and an outer container enclosing the refracting gas. The action of the ultrasonic lens 4 can be understood by analogy with geometrical optics for glass in the air. Since the refractive gas having a higher density than air has a refractive index larger than that of air with respect to the ultrasonic wave, a convex lens for the ultrasonic wave can be configured by making the outer container into the shape of a convex lens.

  According to the object detection apparatus of the present invention, as shown in FIG. 1 (a), the left and right visual field angle θ is, for example, a wide field object detection in the range of θ = + 45 ° to −45 °, and FIG. As shown in (b), the left and right visual field angle θ can be detected in two stages, for example, an object detection with a narrow visual field in the range of θ = + 30 ° to −30 °, and In object detection in a narrow field of view, object detection can be performed with increased directivity by the effect of the ultrasonic lens 4.

  In addition, when the ultrasonic lens 4 shown in FIG. 1B is disposed and the directivity is increased with respect to the detection area a having a wide field of view shown in FIG. 1A, the detection area a is narrowed. The ultrasonic wave reaches the detection area b farther than the detection area a. That is, in the latter case using the ultrasonic lens 4, the ultrasonic wave has a strong intensity in the detection area a before the detection area b without increasing the transmission circuit 10. Accordingly, since a reflected ultrasonic signal with an improved S / N ratio is obtained, the distance and direction of the object can be detected with higher accuracy, that is, without erroneous detection.

  As shown in FIGS. 2A and 2B, the above-described ultrasonic lens 4 is changed from the transmitter 1 by changing the shape and type of the ultrasonic lens 4 disposed in front of the transmitter 1. While changing the direction of transmission to the direction of a specific region, the directivity of the transmitted ultrasonic wave toward that region can be increased. The ultrasonic lens 4 in FIG. 2A is an ultrasonic lens that narrows down the ultrasonic wave transmitted from the transmitter 1 to the left side, that is, increases the directivity toward the left side. The ultrasonic lens 4 is an ultrasonic lens that narrows the ultrasonic wave transmitted from the transmitter 1 to the right side. The ultrasonic lens 4 shown in FIG. 1B is an ultrasonic lens 4 that narrows the ultrasonic wave transmitted from the transmitter 1 in the front direction without changing the direction.

  The ultrasonic lens 4 that squeezes the ultrasonic wave and changes the direction is usually configured by an asymmetric structure with respect to the front direction (center axis direction) of the transmitter 1. For example, an ultrasonic lens that uses a convex lens-shaped ultrasonic lens 4 to squeeze the ultrasonic wave and change the direction by shifting its central axis in parallel with the central axis of the transmitter or tilting the central axes of the transmitter. 4 can be configured.

  Next, referring to FIGS. 3A, 3B and 4A, 4B, in order to switch between different types of arrangement and non-arrangement of the ultrasonic lens 4 in front of the transmission element 11. FIG. An example of the switching mechanism will be described. The ultrasonic lens switching mechanism shown here fixes a plurality of different types of ultrasonic lenses 4 in a predetermined arrangement, and switches the position of the ultrasonic lenses 4 by mechanical movement. 3 (a) and 3 (b) show a state in which the respective ultrasonic lenses 4 are disposed or a state in which the ultrasonic lenses are not disposed 41 for the left direction, the central direction, or the right direction of the visual field. The ultrasonic lenses 4 are arranged in a row on the switching plate 40 so as to be switched. By sliding the switching plate 40 as indicated by an arrow x, it is possible to switch between the ultrasonic lens 4 disposed in front of the wave transmitting element 11 or the ultrasonic lens non-disposed 41.

  4 (a) and 4 (b) are obtained by arranging the above three types of ultrasonic lenses 4 on a turret-like switching plate 40. FIG. By rotating the switching plate 40 as indicated by an arrow R, it is possible to switch between the ultrasonic lens 4 disposed in front of the wave transmitting element 11 or the ultrasonic lens non-disposed 41.

  The operation of this object detection device will be described below. FIG. 5 shows a state of object detection by the object detection device, and FIGS. 6A to 6C show a state of object detection performed following the object detection shown in FIG. The object detection device of the present invention includes, for example, as described above, the ultrasonic lens 4 is not disposed, the ultrasonic lens 4 that squeezes the ultrasonic wave in the center, the ultrasonic lens 4 that squeezes the ultrasonic wave on the left side, and the right side. The four types of detection conditions can be selected: an ultrasonic lens 4 for narrowing down the ultrasonic wave. In addition, the viewing angle range of the detection region is, for example, ± 45 ° when the ultrasonic lens 4 is not disposed around the direction of the highest intensity of transmitted ultrasonic waves (direction of directivity). When using the kind of ultrasonic lens 4, for example, ± 30 °.

  When detecting an object, first, the object is detected in a state where the ultrasonic lens 4 is not provided. That is, using the object detection device of the present invention, as shown in FIG. 5, coarse object detection is performed in a state where a wide visual field region is provided in which the ultrasonic lens 4 is not disposed in front of the transmitter 1. This rough object detection is, so to speak, detecting an object as a candidate, and the next object detection determines whether the candidate object is a ghost or a true object. That is, the ultrasonic lens 4 is selected according to the area where the candidate object is detected by the rough object detection operation, and detection is performed with the detection area narrowed down. By detecting this confirmation, it is possible to detect an object without erroneous detection. In the example shown in FIG. 5, the measured object M1 as a candidate is detected in the left direction. Next, as shown in FIG. 6A, detailed object detection is performed with a narrow field of view in a state where the ultrasonic lens 4 that is narrowed to the left is disposed in front of the transmitter 1. At this time, since the intensity of the ultrasonic wave transmitted to the position of the measured object M1 has increased, the S / N ratio has increased. For this reason, in the case of rough object detection, even if an object that does not actually exist is erroneously detected that the object is present due to noise or the like, in the next detailed object detection to be performed, erroneous detection is performed again. The possibility of doing is reduced. In this way, erroneous detection of an object can be suppressed without increasing the ultrasonic transmission circuit. In addition, since the object can be detected in a state where the S / N ratio is increased, there is also an effect that the distance and direction of the object can be measured more accurately, that is, with high resolution.

  Further, as shown by a broken line in FIG. 5, when a measured object M2 as a candidate is detected in the center front direction, as shown in FIG. 6 (b), the ultrasonic lens 4 focused to the center is transmitted. It arrange | positions in front of the container 1, restrict | squeezes an ultrasonic wave to the center, and acquires the positional information on the to-be-measured object M2. Similarly, as shown by a broken line in FIG. 5, when the object to be measured M3 as a candidate is detected in the right direction, as shown in FIG. Positioned in front of the container 1, the ultrasonic wave is narrowed to the right side, and the position information of the object to be measured M3 is obtained.

  As described above, the object detection apparatus of the present invention performs object detection in two stages, that is, object detection with a wide field of view and object detection with a narrow field of view, and an ultrasonic lens is used for object detection with a narrow field of view. Therefore, object detection can be performed with increased directivity and sound pressure. Therefore, the S / N ratio is increased without increasing the ultrasonic transmission circuit in the detection area of a wide field of view, thereby suppressing false detection. Object detection that detects distance and direction is possible.

  Here, the object detection apparatus of the present invention includes an ultrasonic lens that squeezes the ultrasonic wave toward the center, an ultrasonic lens that squeezes the ultrasonic wave toward the left side, and an ultrasonic lens that squeezes the ultrasonic wave toward the right side. Furthermore, the types of the ultrasonic lens provided are not limited to these, and an ultrasonic lens that squeezes the ultrasonic wave upward and an ultrasonic lens that squeezes the ultrasonic wave downward may be provided. In addition, an ultrasonic lens that squeezes the ultrasonic wave to the upper left side, an ultrasonic lens that squeezes the ultrasonic wave to the lower left side, an ultrasonic lens that squeezes the upper right side, and an ultrasonic lens that squeezes the lower right side may be provided. Good. By including such a kind of ultrasonic lens, it is possible to detect the distance and orientation of an object while suppressing erroneous detection even in a detection region having a wide stereoscopic field of view.

  The present invention is not limited to the above-described configuration, and various modifications can be made. For example, when the functions of the above-described various ultrasonic lenses 4 are changed and used, instead of moving and replacing the ultrasonic lens 4, an outer container that constitutes the ultrasonic lens 4 by enclosing a refraction gas is used. The shape may be changed. For example, when the shape of the outer container is flat and the same thickness, the ultrasonic lens 4 is not disposed, and when the shape is inclined to the left or right, the ultrasonic lens 4 that is squeezed right or left is disposed. If a normal convex lens shape is used, it is possible to realize a state of focusing to the center.

(A) Conceptual explanatory drawing of the state which does not arrange | position the ultrasonic lens in front of the wave transmitter of the object detection apparatus which concerns on one Embodiment of this invention, (b) is the wave transmission of the same object detection apparatus. The conceptual explanatory drawing of the state which has arrange | positioned the ultrasonic lens ahead of the vessel. (A) (b) is a schematic sectional drawing explaining an effect | action and effect of an ultrasonic lens with which an object detection apparatus same as the above is equipped. (A) is a top view which shows the example of the ultrasonic lens switching mechanism used for an object detection apparatus same as the above, (b) is the side surface sectional drawing. (A) is a top view which shows the other example of the ultrasonic lens switching mechanism used for an object detection apparatus same as the above, (b) is the side sectional drawing. The top view which shows the mode of the object detection by an object detection apparatus same as the above. (A) (b) (c) is a top view which shows the mode of the object detection performed following the object detection by the object detection apparatus same as the above shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmitter 2 Receiver element 3 Detection part 4 Ultrasonic lens M1, M2, M3 Object to be measured

Claims (2)

A transmitter for transmitting ultrasonic waves to the detection area;
A plurality of receiving elements that receive the reflected wave of the ultrasonic wave reflected by the object to be measured in the detection region and convert the ultrasonic wave into a received wave signal that is an electrical signal;
Based on the received signal of the receiving element, the distance to the object to be measured corresponding to the time from when the ultrasonic wave is transmitted until it is received is obtained, and the time difference of each received signal at each receiving element is obtained. A detection unit that detects the measurement object by obtaining the orientation of the corresponding measurement object, and an object detection device comprising:
When disposed in front of the transmitter, the ultrasonic wave direction is left unchanged or changed , the detection area is narrowed , and an ultrasonic lens for increasing the sound pressure of the transmitted ultrasonic wave is provided,
The detection unit performs object detection in a state where the ultrasonic lens is not disposed in front of the transmitter, and thereafter, the ultrasonic lens is set so that the transmission direction is directed to the direction of the detected object. An object detection apparatus that performs object detection again in a state of being disposed in front of a transmitter. 2. The object detection apparatus according to claim 1, wherein the ultrasonic lens includes a refracting gas having a higher density than air and an outer container enclosing the refracting gas.

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