JP2005300429A - Acoustic sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an acoustic sensor capable of precisely detecting the incoming direction of sound waves with a simple structure. <P>SOLUTION: Sensor elements 11a-11e are arranged on one plane and convert sound waves to a receiving signal that is an electric signal. A delay means 12 outputs sets of delay signals obtained by delaying the receiving signal outputted from each sensor element 11a-11e with a delay time according to the position of each sensor element 11a-11e. An addition means 13 adds the sets of delay signals delayed by the delay means 12. A determination means 14 compares the addition result by the addition means 13 with a regulated threshold, and determines, when an addition result exceeding the threshold is obtained, that the sound wave comes from a direction corresponding to the delay time set by the delay means 12. The delay means 12 comprises delay elements 12a-12h having BBD connected thereto by different numbers in conformation of the sensor elements 11a-11e so that delay times according to the sensor elements 11a-11e can be obtained. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an acoustic sensor capable of detecting the direction of arrival of sound waves.

  2. Description of the Related Art Conventionally, an acoustic sensor is known in which a plurality of sensor elements that convert sound waves into electrical signals are arranged and the direction of arrival of sound waves is detected from the difference in the arrival time of sound waves at each sensor element (for example, Patent Document 1). reference). In this type of acoustic sensor, for example, as shown in FIG. 5, the sensor elements 11a to 11e are arranged one-dimensionally at equal intervals, and the angle of the wavefront of the sound wave with respect to the surface on which the sensor elements 11a to 11e are arranged is θ. Assume a certain case. In this case, the arrival direction of the sound wave (that is, the incident angle of the sound wave) with respect to the surface on which the sensor elements 11a to 11e are arranged is θ. If the distance between the sensor elements 11a to 11e is d and the speed of sound is c, the time difference at which the wavefronts of the sound waves reach the adjacent sensor elements 11a to 11e is d · sin θ / c.

  In the technique described in Patent Document 1, the electrical signals output from the sensor elements 11a to 11e are delayed by the delay means 12A to 12E by the time corresponding to the position of each sensor element 11, and delayed by the delay means 12A to 12E. The added electrical signals are added by an adder 13 ', and it is configured to determine whether or not the arrival direction of the sound wave is the incident angle θ using the output waveform of the adder 13'.

  Each of the delay units 12A to 12E is configured using a BBD (bucket brigade device), and the delay time in each of the delay units 12A to 12E is designated by the delay time designation unit 15A to 15E. For example, as shown in FIG. 5, when sound waves arrive from above with respect to the normals of the surfaces on which the sensor elements 11a to 11e are arranged, the delay times by the delay means 12A to 12E are respectively 4T, 3T, 2T, The delay time can be specified by the delay time specifying means 15A to 15E so as to be T, 0. However, T = d · sin θ / c.

In this case, the peak value of the output waveform of the adder 13 'with respect to the sound wave whose arrival direction is θ is significantly larger than the peak value of the output waveform of the adder 13' with respect to the sound wave arriving from other directions (see FIG. In the example shown, the five sensor elements 11a to 11e are used so that the sound wave having the same amplitude is approximately five times larger), and the peak value of the output waveform of the adder 13 'is compared with the appropriate threshold value. Thus, it is possible to determine whether or not there is a sound wave whose arrival direction is θ. Further, if the delay time of each of the delay units 12A to 12E is changed with time, the arrival direction θ for detecting the sound wave can be changed, and the arrival direction θ of the sound wave to be detected is scanned. It becomes possible.
JP 2002-156451 A

  By the way, in the configuration shown in FIG. 5, in order to set the delay times of the delay means 12A to 12E configured using BBD by the delay time specification means 15A to 15E, respectively, the delay means 12A to 12E are designated with the delay time. Since it is necessary to provide clock signals of different frequencies from the means 15A to 15E, there is a problem that the configurations of the delay means 12A to 12E and the delay time designation means 15A to 15E become complicated.

  Patent Document 1 also discloses a configuration provided with a loop circuit that feeds back the outputs of the delay units 12A to 12E to the inputs of the delay units 12A to 12E using the standby delay units 17A to 17E, as shown in FIG. ing. This is a configuration for the purpose of obtaining signals in any desired direction using reception signals output from the sensor elements 11a to 11e by receiving a single sound wave obtained from the sensor elements 11a to 11e. Then, after delaying by the delay means 12A to 12E, an operation of returning to the same phase relationship as the received signal by the standby delay means 17A to 17E and re-inputting to the delay means 12A to 12E is adopted.

  In this configuration, the delay times of the delay means 12A to 12E respectively corresponding to the sensor elements 11a to 11e are different, but the delay time of the delay means 12A to 12E and the delay time of the standby delay means 17A to 17E are different. The sum is set to the same value so that the signals inputted to the delay means 12A to 12E after being delayed by the standby delay means 17A to 17E have the same phase relationship as the original signal (that is, the received signal). It is. Therefore, a reception signal obtained by receiving one sound wave is circulated in a loop circuit including the delay means 12A to 12E and the standby delay means 17A to 17E, and the delay time of the delay means 12A to 12E and the standby delay means are meanwhile. By changing the delay times of 17A to 17E, it is possible to detect the arrival of sound waves in a plurality of directions.

  However, if this configuration is adopted, a plurality of types of clock signals are required in the delay means 12A to 12E, and the frequency of the clock signal must be changed for each loop, so that the processing becomes complicated. In addition, since the total delay time of the standby delay means 17A to 17E needs to be at least about the total delay time of the delay means 12A to 12E, the delay means 12A to 12E and the standby delay means 17A to 17E are required. There is a problem that the number of BBDs constituting the number increases. Furthermore, if it is attempted to detect the arrival of a sound wave in a plurality of directions, the reception signal due to the reception of one sound wave is circulated a plurality of times in the loop circuit, so that the waveform of the reception signal, which is an analog signal, increases in distortion, There is also a problem that the error due to distortion increases and the detection accuracy of the direction of arrival decreases.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide an acoustic sensor that can accurately detect the arrival direction of a sound wave with a simple configuration.

  The invention according to claim 1 is a receiver in which a plurality of sensor elements for converting sound waves into received signals that are electrical signals are arranged in a prescribed arrangement pattern, and received signals output from the sensor elements are respectively sensor elements. A delay means for outputting a set of delay signals delayed by a delay time corresponding to the arrangement pattern of the above, an addition means for adding the set of delay signals delayed by the delay means, an addition result by the addition means, and a prescribed threshold value And determining means for determining that a sound wave has arrived from the direction corresponding to the delay time set by the delay means when an addition result exceeding the threshold value is obtained. A delay element that delays an analog signal with a constant time is connected in a different number in association with the sensor element so that a delay time corresponding to the sensor element is obtained.

  According to this configuration, since the delay time necessary for each sensor element is ensured by the number of delay elements, it is not necessary to provide a plurality of types of clock signals to the delay means as in the conventional configuration, and the configuration is simplified. In addition, since it is not necessary to provide a loop circuit in the delay means, the delay means can be configured with a relatively small number of delay elements, and since the number of delay elements until the delay signal is extracted is small, the delay signal output from the delay means can be reduced. Waveform distortion is also reduced. As a result, the time error in the delay signal added by the adding means is reduced, and the arrival direction of the sound wave can be detected with high accuracy.

  According to a second aspect of the present invention, in the first aspect of the invention, a transmitter that intermittently transmits a sound wave, a time at which the sound wave whose direction of arrival is detected by the determination means is received by the receiver, and a transmitter And a position calculating means for obtaining a distance to an object reflecting the sound wave transmitted from the transmitter according to a time from the time when the sound wave is transmitted from.

  According to this configuration, since the distance to the object can be obtained using sound waves, the position of the object is two-dimensionally or three-dimensionally combined with the presence direction of the object detected by the arrival direction of the reflected wave. It becomes possible to ask for.

  According to a third aspect of the present invention, in the second aspect of the present invention, the determination means compares a peak hold circuit for detecting a peak value of the addition result by the addition means, and a peak value obtained by the peak hold circuit with a threshold value. And a comparison circuit.

  According to this configuration, since the peak value of the addition result by the addition means is detected by the peak hold circuit, the evaluation of the addition result by the addition means can be formulated and the detection accuracy of the object position can be made almost constant.

  According to a fourth aspect of the invention, in the third aspect of the invention, the peak hold circuit detects the peak value of the addition result at a fixed time interval shorter than the time interval at which the transmitter transmits a sound wave. Features.

  According to this configuration, the accuracy of the distance to the object can be defined by the time interval at which the peak hold circuit detects the peak value.

  According to a fifth aspect of the present invention, in the first to fourth aspects of the invention, the receiver has at least a part of the sensor elements arranged on a straight line at equal intervals, and the delay means is the straight line. A set of delay signals obtained by incrementing the number of delay elements corresponding to each sensor element toward the other end with respect to the sensor element at one end of And a set of delay signals obtained by increasing the number of delay elements corresponding to each sensor element by one.

  According to this configuration, it is possible to simultaneously detect sound waves from two directions without increasing the number of sensor elements constituting the receiver. In other words, when sound waves from two directions are detected by different receivers, the arrival direction of the sound waves needs to be corrected based on the positional relationship of the receivers. The error related to the direction of arrival of the sound wave is a minute error about the position of both ends of the straight line on which the sensor elements are arranged, and can be detected substantially without error.

  According to a sixth aspect of the present invention, in the first to fifth aspects of the present invention, the delay element is a bucket brigade device.

  According to this configuration, the delay means can be configured only by providing a plurality of bucket brigade devices having the same delay time, and therefore, it is easy to make an integrated circuit.

  The invention according to claim 7 is the invention according to claim 6, wherein a frequency filter for removing a noise component generated by the delay means is provided between the delay means and the determination means.

  According to this configuration, since the noise component due to the clock signal generated by using the bucket brigade device as a component of the delay unit is removed by the frequency filter, it is possible to prevent erroneous detection of the arrival direction of the sound wave due to the mixing of the noise component. Can do.

  According to an eighth aspect of the present invention, in the first to seventh aspects of the present invention, the delay means includes a delay element group in which the number of delay elements corresponding to the sensor element is one delay element, and the delay elements are cascade-connected. Is provided for each sensor element, and the delayed signals obtained through the same number of delay elements for each received signal from each sensor element are output in pairs.

  According to this configuration, since a plurality of delay elements cascaded for each sensor element are provided, a set of delay signals obtained through the same number of delay elements for each sensor element is given to the adding means. This makes it possible to detect sound waves coming from the direction corresponding to the set of delayed signals. That is, it is possible to detect the arrival of sound waves from a plurality of directions using a single receiver, and to accurately detect the arrival directions of sound waves.

  According to a ninth aspect of the invention, in the eighth aspect of the invention, the adding means includes a plurality of adders for adding a plurality of sets of delayed signals output from the delay means for each set.

  According to this configuration, by providing a plurality of adders that add for each set of delayed signals corresponding to the arrival direction of the sound wave, it is possible to simultaneously detect the arrival direction of the sound wave in a plurality of directions.

  According to a tenth aspect of the present invention, in the ninth aspect of the invention, the determination unit compares each of a plurality of addition results output from the addition unit with a threshold value.

  According to this configuration, since the addition results of the plurality of adders corresponding to the arrival directions of the sound waves are compared with the threshold values in the determination unit, it is possible to set the threshold values according to the addition results of the respective adders. It is possible to make an accurate determination by setting an appropriate threshold value according to the direction of arrival of.

  According to the configuration of the present invention, since the delay time required for each sensor element is ensured by the number of delay elements, it is not necessary to provide a plurality of types of clock signals to the delay means as in the conventional configuration, and the configuration is simplified. Since there is an advantage and it is not necessary to provide a loop circuit in the delay means, the delay means can be configured with a relatively small number of delay elements, and since the number of delay elements until the delay signal is extracted is small, the delay means outputs the delay means. As a result, there is an advantage that the waveform of the delayed signal is reduced, and as a result, the time error in the delayed signal added by the adding means is reduced, and the arrival direction of the sound wave can be detected with high accuracy.

(Embodiment 1)
In the embodiment described below, as shown in FIG. 2, ultrasonic waves are intermittently transmitted from the transmitter 2 provided in the ultrasonic wave generation means, and the ultrasonic waves transmitted from the transmitter 2 are the object. In the time until the reflected wave is received by the receiver 1 after the reflected wave reflected by 3 is received by the receiver 1 provided in the acoustic sensor and the ultrasonic wave is transmitted from the transmitter 2. Based on this, the distance to the object 3 is obtained, the arrival direction of the reflected wave to the receiver 1 is detected, and the relative position of the object 3 can be obtained from the obtained distance and the arrival direction of the reflected wave. A sonic sensor is illustrated.

  However, the acoustic sensor described in the present embodiment can be used not only for an ultrasonic sensor but also for various applications for detecting the arrival direction of a sound wave. In addition, the type of sound wave is not limited to the ultrasonic wave as long as the condition that the sound wave incident on the receiver 1 is a plane wave is satisfied. In the following description, in order to simplify the description, a case where the relative position of the object 3 with respect to the receiver 1 is obtained by two-dimensional polar coordinates is illustrated. However, the following description is given so as to obtain the position of the object 3 in a three-dimensional space. It is easy to extend the configuration of this embodiment.

  As shown in FIG. 1, the receiver 1 used in this embodiment includes a plurality of (in the illustrated example, five) sensor elements 11 a to 11 e that convert ultrasonic waves into electrical signals in a one-dimensional manner (on a straight line). It is composed of sensor arrays arranged at equal intervals, and furthermore, a large number (in the example shown, 9 × 8 stages = 72) for delaying electrical signals (hereinafter referred to as reception signals) output from the individual sensor elements 11a to 11e. Delay means 12 comprising delay elements 12a to 12h. The delay means 12 outputs a plurality of sets of delay signals (in the example shown, one set of five, 19 sets), and the delay signals are input to adders 13a to 13s provided in the addition means 13 for each set. The addition result by 13a-13s is input into the determination means 14, and the determination means 14 determines the arrival direction of an ultrasonic wave.

  The determination unit 14 includes peak hold circuits 14a to 14s that detect peak values of output signals from the adders 13a to 13s, and comparison circuits that compare outputs of the peak hold circuits 14a to 14s with appropriate threshold values. 15a-15s. Each of the comparison circuits 15a to 15s outputs a binary signal corresponding to the magnitude relationship between the output of the peak hold circuits 14a to 14s and the threshold value. The threshold value in each of the comparison circuits 15a to 15s is set for each of the comparison circuits 15a to 15s by the threshold setting unit 15. Although it is possible to set a plurality of levels of threshold values in each of the comparison circuits 15a to 15s, it is assumed here that one level of threshold value is set in each of the comparison circuits 15a to 15s. Each of the comparison circuits 15a to 15s is associated with the arrival direction of the ultrasonic wave, and can determine the arrival direction of the ultrasonic wave depending on which comparison circuit 15a to 15s has obtained an output exceeding the threshold value. . This technique will be described later.

  The outputs of the comparison circuits 15a to 15s are input to the position calculation means 16, where the position calculation means 16 transmits the ultrasonic wave from the transmitter 2 and the peak hold circuits 14a to 14a from any of the comparison circuits 15a to 15s. The distance to the object 3 is calculated based on the time difference from the timing when the output indicating that the output of 14s exceeds the threshold is obtained. Therefore, in the position calculating means 16, the arrival directions of the ultrasonic waves can be determined by the comparison circuits 15a to 15s that have obtained outputs exceeding the threshold value, and the distance to the object 3 can be determined by the timing of transmission and reception.

  This will be described more specifically. The ultrasonic wave generation means has a timing control circuit 21 for controlling the drive timing of the ultrasonic vibrator provided in the transmitter 2. The timing control circuit 21 outputs a rectangular wave having a constant time width at a constant period, and the transmitter 2 intermittently transmits ultrasonic waves in synchronization with the rectangular wave output from the timing control circuit 21. The time width for transmitting the ultrasonic wave once is set according to the minimum delay time of the delay elements 12a to 12h (resolution regarding the arrival direction of the ultrasonic wave) and the interval between the adjacent sensor elements 11a to 11e.

  As the sensor elements 11a to 11e constituting the receiver 1, one that converts sound waves into an electric signal by the piezoelectric effect as shown in FIG. 3 and one that converts sound waves into a change in capacitance as shown in FIG. Is widely known, so one having any structure is used.

  3 shows a platinum thin film lower electrode 31 having a titanium base on a main surface of an SOI substrate 30 of about 1 mm square, a piezoelectric layer 32 made of a PZT thin film formed by a sol-gel method, and an upper electrode made of platinum. 33 in this order. The SOI substrate 30 has silicon oxide film layers 30b and 30c on both front and back surfaces of a support substrate 30a formed from a silicon wafer. The silicon oxide film layer 30b on the main surface side of the support substrate 30a further includes a silicon layer 30d and a silicon layer. An oxide film layer 30e is sequentially stacked. In the central portion of the SOI substrate 30, a groove portion 30f reaching the silicon layer 30d from the lower surface is formed. With this configuration, when sound pressure acts on a thin laminated body of the silicon layer 30d, the silicon oxide film layer 30e, the lower electrode 31, the piezoelectric layer 32, and the upper electrode 33 at a portion corresponding to the groove 30f, the piezoelectric effect causes Since a voltage corresponding to the pressure of the sound wave is generated in the piezoelectric layer 32, a minute voltage change occurs according to the pressure of the sound wave between the lower electrode 31 and the upper electrode 33, so that the sound wave is converted into an electric signal. be able to.

On the other hand, the one shown in FIG. 4 has a groove 40a in the center of a support substrate 40 made of an n ⁻ -type silicon substrate, and a p ^{+ -type} straddling the bottom and periphery of the groove 40a on the main surface side of the support substrate 40. The back vent 41 is provided. Further, a silicon nitride film layer 43 is laminated on the main surface of the back vent 41 around the groove 40a via a silicon oxide film layer 42, and n ⁺ -type polysilicon facing the back vent 41 at a portion corresponding to the groove 40a. The peripheral portion of the diaphragm 44 made of is bonded to the silicon nitride film layer 43. Exhaust holes 41 a communicating with the front and back are formed in the back vent 41 at appropriate positions, and electrode pads 45 and 46 made of a metal thin film are provided in part of the back vent 41 and the diaphragm 44. In this configuration, a capacitor having the diaphragm 44 and the back vent 41 as electrodes is formed. Therefore, when the diaphragm 44 receives a sound wave pressure and changes the distance from the back vent 41, the diaphragm 44 and the back vent 41 The capacitance during the change. Therefore, if a DC bias voltage is applied between the electrode pads 45 and 46, a minute voltage change occurs between the electrode pads 45 and 46 in accordance with the pressure of the sound wave, so that the sound wave is converted into an electrical signal. be able to.

  The delay means 12 includes a plurality of delay element groups in which delay elements 12a to 12h having the same delay time are cascade-connected, and each delay element group is connected in association with one of the sensor elements 11a to 11e. Each delay element 12a to 12h is configured using a BBD driven by a two-phase clock signal as a delay element, and in this embodiment, in order to set the delay time per BBD to 1 μs, It is set to 500 kHz. The delay elements constituting the delay elements 12a to 12h only need to have a function of delaying and transferring charges with a clock signal, and may be configured using a CCD instead of a BBD.

  In FIG. 1, the delay elements 12a and 12h constituting the first-stage delay element group and the eighth-stage delay element group each have one BBD, and the second-stage and seventh-stage delay elements 12b and 12g. Includes two BBDs, the third and sixth delay elements 12c and 12f include three BBDs, and the fourth and fifth delay elements 12d and 12e include four BBDs. Prepare. The delay time of the delay elements 12a and 12h is 1 μs, the delay time of the delay elements 12b and 12g is 2 μs, the delay time of the delay elements 12c and 12f is 3 μs, and the delay time of the delay elements 12d and 12e is 4 μs. Accordingly, each of the delay elements 12a to 12h has a configuration in which a BBD having a delay time of 1 μs is used as a delay element and a different number is connected according to the sensor elements 11a to 11e. That is, the delay means 12 is configured to operate a number of BBDs of the same configuration corresponding to the delay time with one clock signal, and thus can be easily integrated.

  In the example shown in FIG. 1, there is a path for inputting the outputs of the two sensor elements 11a and 11e to the adding means 13 without passing through any of the delay elements 12a to 12h. This path has a delay time of 0 μs. It is assumed that a delay element is provided. That is, ten delay elements are provided, which is twice as many as the five sensor elements 11a to 11e, and the delay time of two of the delay elements is set to 0 μs. In short, the delay elements 12a to 12h constituting each delay element group need only have a difference of 1 μs in delay time, and the delay time is 1 μs in the path where the delay elements 12a to 12h are not provided in FIG. When a delay element group including delay elements is provided, the delay times of the delay elements 12a to 12h constituting the other delay element groups may be configured to be 2 μs, 3 μs, 4 μs, and 5 μs, respectively.

  As described above, the delay times of the nine delay elements 12a to 12h constituting one delay element group are equal to each other, and the delay elements 12a to 12h are cascade-connected in each delay element group. Time is added. For example, if one delay element 12a constituting the first-stage delay element group in FIG. 1 is passed, the signal is delayed by time T. If two delay elements 12a are passed, the signal is time 2T. Only delayed. Further, in the second delay element 12b, if one element is passed, the time is delayed by time 2T, and if two elements are passed, the time is delayed by time 4T.

  The delay time T is the adjacent sensor element 11a when the incident angle of the sound wave on the surface on which the sensor elements 11a to 11e are arranged is a specified angle (5 ° in the present embodiment) corresponding to the resolution related to the arrival direction of the sound wave. The time difference at which the same wavefront of the sound wave reaches ˜11e is substantially matched. For example, if the speed of sound is 340 m / s and the distance between the sensor elements 11a to 11e is 4 mm, the incident angle is 5 ° (the left-right direction in FIG. 1 is 0 ° and the lower angle is positive). In some cases, the time difference between the arrival of the same wavefronts at the sensor element 11a and the sensor element 11b is 1.03 μs. Therefore, the delay time T is set to 1 μs for the resolution of the sound wave arrival direction to be about 5 ° under the above conditions. It can be said that this should be set. That is, if the delay times of the delay elements 12a to 12h are set to 1 μs, 2 μs, 3 μs, and 4 μs, respectively, as described above, the resolution of about 5 ° can be achieved while driving the delay elements 12a to 12h with the same clock signal. Can be obtained. Further, in the configuration of the present embodiment, the number of BBDs constituting the delay means 12 is 180, so that the mounting area can be made relatively small, miniaturization is possible, and the device is provided at a relatively low cost. be able to.

  As shown in Table 1, when all the delay elements 12a to 12h are driven with the same clock signal, the time difference (arrival time difference) at which the sound waves of the same wavefront enter each sensor element 11a to 11e and the delay due to the delay elements 12a to 12h Although there is an error in time, it is only necessary to distinguish the addition result of one adder 13a to 13s from the addition result of the other adders 13a to 13s. Therefore, even if there is an error in the arrival time difference and the delay time, the delay means 12 The time width of the ultrasonic wave transmitted from the transmitter 2 may be set so that a part of the set of delayed signals output from each other overlap each other. However, if the time width of the ultrasonic wave transmitted from the transmitter 2 is made longer than necessary, the resolution with respect to the arrival direction of the sound wave is reduced. Therefore, the time width of the ultrasonic wave transmitted from the transmitter 2 is different from the arrival time difference. And the delay time and the resolution related to the direction of arrival of the sound wave. Further, since all the delay elements 12a to 12h can be driven by the same clock signal, the configuration and control of the delay means 12 are simple, and the IC of the delay means 12 becomes easy.

  In Table 1, “1, 8 stage” corresponds to the delay elements 12a, 12h, “2, 7 stage” corresponds to the delay elements 12b, 12g, and “3, 6 stage” represents the delay elements 12c, 12f. “4, 5 stages” correspond to the delay elements 12d and 12e. Further, “number” is the number of received signals passing through the delay elements 12 a to 12 h connected in cascade, “delay” is the delay time (delay time of the delayed signal with respect to the received signal), “arrival” by the delay elements 12 a to 12 h. Represents the delay time (arrival time difference) of the reception signals of the other sensors 12b to 12g that have received the sound waves of the same wavefront with respect to the reception signals of the sensor elements 12a and 12h serving as the reference. The unit of delay time and arrival time difference is [μs].

  The reception signal output from the sensor element 11a is output from the delay means 12 without passing through any of the delay elements 12a to 12h, or is output from the delay means 12 through the delay element 12e at the fifth stage. Similarly, the reception signal from the sensor element 11b is output from the delay means 12 through the delay elements 12a and 12f of the first and sixth stages, and the reception signal from the sensor element 11c is the second and seventh stages. Are output from the delay means 12 through the delay elements 12b and 12g, and the received signal from the sensor element 11d is output from the delay means 12 through the delay elements 12c and 12h at the third and eighth stages, and received from the sensor element 11e. The signal is output from the delay means 12 through the delay element 12d in the fourth stage, or is output from the delay means 12 without passing through any of the delay elements 12a to 12h.

  As described above, the delay signals output from the delay means 12 are 19 sets of 5 outputs, and the 5 outputs corresponding to one set are signals corresponding to the received signals of all the sensor elements 11a to 11e. Are combined to include One of the 19 sets is a combination in which the reception signals from the sensor elements 11a to 11e are extracted without passing through the delay elements 12a to 12h, and the other set is a combination of the reception signal output from the sensor element 11a. A combination of reception signals output from the sensor elements 11b to 11e and passed through the same number of delay elements 12a to 12d in the upper four stages, or a reception signal output from the sensor element 11e and output from the sensor elements 11a to 11d and lower four stages Any of the combinations with the received signals that have passed through the same number of delay elements 12e to 12h. In the delay means 12 shown in FIG. 1, a set of delay signals with the same angle is provided. For example, a set of five delayed signals denoted as + 40 °.

  The adding means 13 includes 19 adders 13a to 13s that add the delayed signals for each group. In FIG. 1, the adders 13 a to 13 s expressed in the form of Σθ (θ is an angle) means that the delay signals corresponding to the angle θ output from the delay means 12 are added. For example, a set of five delayed signals of + 40 ° is added in the adder 13b expressed as Σ + 40 °. Here, when the incident angle of the sound wave to the receiver 1 is θ, the five delay signals corresponding to the angle θ are input to the adders 13a to 13s at almost the same timing. When the reflected wave by the transmitted ultrasonic wave is incident on the receiver 1 at the incident angle θ, the peak value of the output of one adder 13a to 13s corresponding to the angle θ is ideally five. The peak value of the delayed signal is added. Therefore, only the outputs of the adders 13a to 13s corresponding to the incident direction of the sound wave are significantly larger than the outputs of the other adders 13a to 13s.

  The peak hold circuits 14a to 14s provided in the determination means 14 are circuits that hold the peak values of the outputs of the adders 13a to 13s at regular intervals (for example, every 0.6 ms). The previous peak value is held until it is held. That is, peak values are extracted at intervals of 0.6 ms, and the extracted peak values are held for 0.6 ms. Since 0.6 ms corresponds to 0.2 m when the sound speed is set to 340 m / s, the peak value extraction and holding in the peak hold circuits 14 a to 14 s is performed at intervals of 0.6 ms up to the object 3. This means that the distance resolution is 0.2 m. The peak hold circuits 14a to 14s start an operation of taking out and holding the peak value starting from the time point when the timing control circuit 21 instructs the transmitter 2 to transmit ultrasonic waves. That is, the peak hold circuits 14 a to 14 s are controlled by the timing control circuit 21.

  The determination means 14 is also provided with comparison circuits 15 a to 15 s for comparing the peak value held by the peak hold circuits 14 a to 14 s with the threshold set by the threshold setting unit 15. By the way, even when the distance to the object 3 is equal, the pressure received by the sensor elements 11a to 11e varies depending on the incident angle of the reflected wave to the wave receiver 1. Therefore, the peak values of the output signals of the adders 13a to 13s are also reflected waves. It depends on the incident angle. Therefore, it is desirable to vary the threshold values for the comparison circuits 15a to 15s. That is, as the incident angle increases, the level of the reception signal output from the sensor elements 11a to 11e decreases. Therefore, the threshold value set for the comparison circuits 15a to 15s is smaller as the threshold value compared with the reception signal having a larger incident angle. It is desirable to set it to a value.

  When the output value of the peak hold circuits 14a to 14s exceeds the threshold value in any of the comparison circuits 15a to 15s, it indicates that the sound wave is incident on the receiver 1 at an incident angle corresponding to the comparison circuits 15a to 15s. Since the comparison circuits 15a to 15s output binary signals, if there are comparison circuits 15a to 15s whose outputs are inverted, the sound wave is received by the receiver 1 at an incident angle corresponding to the comparison circuits 15a to 15s. It is incident on. Here, in this embodiment, the arrival direction of the sound wave is detected in increments of 5 °, and it is inconvenient if the sound wave is not detected when the sound wave is incident at an intermediate angle (for example, 22.5 °). When the sound wave is incident at an intermediate angle, it is desirable to invert the output in the two comparison circuits 15a to 15s (comparative circuits 15e and 15f in the illustrated example) sandwiching the angle. In order to satisfy such a condition, the addition result of only one set of delayed signals is not larger than the addition result of the other sets of delayed signals in the adding means 13, but the addition result of the two sets of delayed signals is different from the other results. It is necessary to set the time width of the ultrasonic wave transmitted from the transmitter 2 so as to be larger than the addition result of the set of delay signals. Under this condition, the peak values of the output signals of the two adders 13a to 13s are larger than the peak values of the output signals of the other adders 13a to 13s, and the outputs of the two comparison circuits 15a to 15s are inverted. Therefore, when the outputs of the two comparison circuits 15a to 15s are inverted, the position calculation means 16 determines that the sound wave is incident at an intermediate angle between the incident angles corresponding to both the comparison circuits 15a to 15s. Although depending on the time width of the ultrasonic wave transmitted from the transmitter 2, when a sound wave is incident at an intermediate angle, all of the five delay signals paired in the peak hold circuits 14a to 14s are set. In some cases, it may not be possible to obtain an added peak value. For example, a peak value obtained by adding three delay signals may result in a peak value obtained by adding five delay signals to the threshold values set in the comparison circuits 15a to 15s. It is desirable to set it lower than when the value is obtained.

  Note that a noise filter due to a clock signal used for driving the delay elements 12a to 12s is removed by providing a frequency filter composed of a low-pass filter or a band-pass filter in any one of the preceding and succeeding stages of the adders 13a to 13s. Is desirable. Therefore, when an ultrasonic wave of several tens kHz is used, the cut-off frequency of the low pass filter or the band pass filter is set so as to pass 20 to 100 kHz and block 500 kHz.

  Further, when the outputs of the sensor elements 11a to 11e are small, a preamplifier for amplifying the outputs of the sensor elements 11a to 11e may be added before the delay means 12. For example, since the sensor elements 11a to 11e described above generally have a sensitivity of several mV / Pa, if the sensitivity of the sensor elements 11a to 11e is 5 mV / Pa and the sound pressure is 0.01 Pa, the sensor element Since the outputs of 11a to 11e are 0.05 mV, if the input voltage required for the delay means 12 is 5 to 50 mV, two or three amplifiers are provided as preamplifiers, and the amplification factor is 40 to 60 dB. Good. Also, it is desirable to use an amplifier having an AGC function or a logarithmic amplifier as the preamplifier, and to increase the amplification factor when the output voltage is low and to decrease the amplification factor when the output voltage is high. .

  In the configuration example described above, the acoustic sensor capable of detecting the direction of arrival at ± 45 ° with respect to the sound wave incident from above and the sound wave incident from below with respect to the normal line of the surface on which the sensor elements 11a to 11e are arranged is illustrated. In the case where it is only necessary to detect the direction of arrival of the sound wave incident from either one of the upper side and the lower side with respect to the normal of the surface on which the sensor elements 11a to 11e are arranged, the upper four steps and the lower in the delay means 12 Only one of the four delay elements 12a to 12h may be provided, and the number of delay elements 12a to 12h is halved. Further, the number of adders 13a to 13s, peak hold circuits 14a to 14s, and comparison circuits 15a to 15s is also substantially halved. Furthermore, although the resolution regarding the arrival direction of the sound wave is 5 ° and the resolution regarding the distance is 0.2 m, this value is an example and can be appropriately set according to the purpose.

  In the above configuration example, an ultrasonic sensor that detects the position of the object 3 by transmitting an ultrasonic wave from the transmitter 2 and detecting a reflected wave using an acoustic sensor is illustrated. The acoustic sensor can also be used for the purpose of detecting the direction of the sound source generating the sound wave. In this case, the distance to the sound source cannot be detected. However, as is clear from the above description, the sound source The direction in which the sound wave exists (the arrival direction of the sound wave) can be detected. However, when detecting the direction in which the sound source exists, it is not necessary to synchronize with the transmission side by the timing control circuit 21, so that the clock signal given to the delay means 12 and the holding time of the peak hold circuits 14a to 14s are set. The signal to be controlled may be given at an appropriate timing, and the signal used for the calculation of the distance to the object 3 in the position calculation means 16 becomes unnecessary.

  By the way, in the above-described example, the configuration for detecting the arrival direction of the sound wave has been described. However, in order to change the direction in which the sound wave is radiated in the wave transmitter 2, a plurality of wave transmitting elements are arranged and the wave transmitter 2 is arranged. It is possible to incline the wavefront of the ultrasonic wave to be transmitted with respect to the surface on which the transmission elements are arranged by shifting the drive timing of each transmission element provided in the transmitter 2. In order to shift the drive timing of each transmission element, a delay means including a plurality of delay elements is used as in the case of the acoustic sensor, and each transmission element is delayed by a delay element having a delay time corresponding to the ultrasonic wave transmission direction. The drive timing is delayed. If such a configuration is adopted, the ultrasonic wave transmission direction is specified. Therefore, when the position of the object 3 is detected using the ultrasonic wave reflected by the object 3 as described above, an unnecessary direction is used. Therefore, it is possible to detect only the object 3 existing in the target direction. Further, by preventing the ultrasonic wave from being transmitted in an unnecessary direction, it becomes difficult to be affected by multiple reflection, and noise due to multiple reflection included in the reflected wave received by the receiver 1 is reduced.

It is a block diagram which shows the acoustic sensor used for embodiment of this invention. It is a block diagram which shows the usage example of this invention. It is sectional drawing which shows an example of the sensor element used for the same as the above. It is sectional drawing which shows the other example of the sensor element used for the same as the above. It is a block diagram which shows a prior art example. It is a principal part block diagram same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Receiver 2 Transmitter 3 Object 11a-11e Sensor element 12 Delay means 12a-12h Delay element 13 Adder 13a-13s Adder 14 Judgment means 14a-14s Peak hold circuit 15 Threshold setting part 15a-15s Comparison circuit 16 Position calculation means

Claims (10)

  A receiver in which a plurality of sensor elements for converting sound waves into received signals, which are electrical signals, are arranged in a prescribed arrangement pattern, and a reception signal output from each sensor element is delayed in accordance with the arrangement pattern of the sensor elements. A delay means for outputting a set of delayed signals delayed by time, an adding means for adding a set of delayed signals delayed by the delay means, and comparing the result of the addition by the adding means with a prescribed threshold value Determining means for determining that a sound wave has arrived from a direction corresponding to the delay time set by the delay means when an addition result exceeding the delay time is obtained. A different number of delay elements for delaying signals are connected in association with sensor elements so that a delay time corresponding to the sensor element can be obtained.   A transmitter that intermittently transmits a sound wave, and a transmitter according to the time between the time when the sound wave whose direction of arrival has been detected by the determination means is received by the receiver and the time when the sound wave is transmitted from the transmitter The acoustic sensor according to claim 1, further comprising: a position calculation unit that obtains a distance to an object that reflects the sound wave transmitted from.   3. The determination means comprises a peak hold circuit that detects a peak value of the addition result by the addition means, and a comparison circuit that compares the peak value obtained by the peak hold circuit with a threshold value. Acoustic sensor.   4. The acoustic sensor according to claim 3, wherein the peak hold circuit detects the peak value of the addition result at a fixed time interval shorter than a time interval at which the transmitter transmits a sound wave.   The receiver has at least a part of the sensor elements arranged on a straight line at equal intervals, and the delay means corresponds to each sensor element toward the other end with respect to the sensor element at one end of the straight line. A set of delay signals obtained by increasing the number of delay elements to be incremented one by one, and the number of delay elements corresponding to each sensor element is incremented by one toward one end with reference to the sensor element at the other end of the straight line The acoustic sensor according to any one of claims 1 to 4, wherein a set of delayed signals obtained by the processing is output.   The acoustic sensor according to claim 1, wherein the delay element is a bucket brigade device.   The acoustic sensor according to claim 6, wherein a frequency filter for removing a noise component generated by the delay unit is provided between the delay unit and the determination unit.   The delay means includes a delay element group corresponding to the sensor elements as one delay element, a delay element group in which the delay elements are cascade-connected, and the same number of received signals from each sensor element. The acoustic sensor according to any one of claims 1 to 7, wherein the delay signals obtained through the delay elements are output in pairs.   9. The acoustic sensor according to claim 8, wherein the adding means includes a plurality of adders for adding a plurality of sets of delay signals output from the delay means for each set.   The acoustic sensor according to claim 9, wherein the determination unit compares each of a plurality of addition results output from the addition unit with a threshold value.

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