Object detection equipment and parking aids

Abstract

An object detection device (100, 100a, 101, 102, 103, 104), comprising: a transducer (110) having a vibrator (111a) for transmitting and receiving ultrasonic waves, and configured to transmit a transmission signal encoded to be assigned identification information, and receive the transmission signal reflected by an object (X1) as a reception signal; a correlation processing unit (123) for acquiring a first correlation value and determining whether a reception signal assigned identification information having a predetermined level or higher similarity with the identification information of the transmission signal has been received, the first correlation value corresponding to the similarity between the identification information of the transmission signal and the reception signal; and a detection unit (124) configured to detect information about the object when it is determined that a reception signal assigned identification information having a predetermined level or higher similarity has been received.

Description

Technical Field

[0001] The present disclosure relates to an object detection device and a parking assist apparatus. Background Art

[0002] In the related art, a technology is known that obtains information about an object, such as a distance to the object, by transmitting a transmission signal as an ultrasonic wave via a vibrator (such as a piezoelectric element) and receiving the transmission signal reflected by an object as a reception signal via the vibrator to obtain a time difference between the transmission and reception of the ultrasonic wave. For example, see WO2016 / 167003 (reference 1).

[0003] In the above technology using a vibrator, since the vibrator continues to vibrate due to inertia even after the transmission of the transmission signal is completed, time is required until the vibration of the vibrator subsides. This time is called "reverberation time". Here, when a reception signal is received during the reverberation time, the vibration of the vibrator generated by the reception signal and the residual vibration of the vibrator due to inertia coexist. In this case, since it is difficult to accurately detect only the reception signal due to, for example, a fixed threshold value related to the vibration amplitude, conventionally, detection of the reception signal is avoided until the reverberation time ends.

[0004] However, in a case where an object as a detection target is very close, for example, in a case where the difference between the width of the vehicle and a parking frame (such as a wall) is very small, it is also conceivable that the transmission signal is returned before the reverberation time ends. Therefore, a technology for detecting a reception signal even before the reverberation time ends is required to achieve detection of an object existing at a shorter distance.

[0005] Thus, there is a need for an object detection apparatus and a parking assist device that can achieve detection of an object present at a shorter distance. Summary of the invention

[0006] According to one aspect of the present disclosure, an object detection device includes: a transducer, the transducer having a vibrator capable of sending and receiving ultrasonic waves, and configured to, through the vibrator, send a transmission signal that has been encoded to give identification information of a predetermined code length, and receive the transmission signal reflected by an object existing in the surrounding as a reception signal; a correlation processing unit, the correlation processing unit being configured to obtain a first correlation value immediately after the transmission of the transmission signal is completed, and based on a comparison result between the first correlation value and a first threshold, determine whether a reception signal that is given identification information with a predetermined level or higher similarity to the identification information of the transmission signal has been received, the first correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal; and a detection unit, the detection unit being configured to detect information about the object when it is determined that a reception signal that is given identification information with a predetermined level or higher similarity to the identification information of the transmission signal has been received.

[0007] According to the above configuration, it is possible to determine whether the transmission signal is reflected and returned as the reception signal using the identification information given to the transmission signal (and the reception signal) from immediately after the transmission of the transmission signal is completed. Thus, since the reception signal can be detected even before the reverberation time ends, it is possible to provide an object detection device capable of realizing detection of an object existing at a shorter distance.

[0008] In the above-mentioned object detection device, the correlation processing unit may acquire a first correlation value during the end of the reverberation time from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides, and determine whether a received signal to which identification information having a predetermined level or higher similarity with the identification information of the transmission signal has been received based on a comparison result between the first correlation value and a first threshold value, the first correlation value corresponding to the similarity between at least a part of the identification information of the transmission signal and at least a part of the identification information of the reception signal. With this configuration, since the time required to acquire (calculate) the first correlation value can be shortened unlike the case where information on all code lengths of the identification information is always considered, rapid detection of the object can be achieved.

[0009] In the above-mentioned object detection device, the correlation processing unit may set the first first threshold value as the first threshold value to be compared with the first correlation value after the reverberation time from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides, and set the second first threshold value as the first threshold value to be compared with the first correlation value during the time from immediately after the transmission of the transmission signal is completed until the reverberation time ends so as to be different from each other. With this configuration, appropriate object detection can be achieved by separately using different first threshold values ​​according to the situation.

[0010] In the above object detection device, the second first threshold value may be set to become smaller as time passes. With this configuration, a second first threshold value suitable for a transmission signal (reception signal) that attenuates as time passes (ie, as the propagation distance increases) can be obtained.

[0011] In the above-mentioned object detection device, after acquiring the first correlation value, the correlation processing unit may acquire the second correlation value, and, based on the comparison result between the second correlation value and the second threshold value, determine whether a plurality of signals have been received as received signals to which identification information having a predetermined level or higher similarity with identification information of a transmitted signal has been assigned, the second correlation value corresponds to the similarity between at least a part of a first pattern and a second pattern, the first pattern corresponds to a time change of the first correlation value, the second pattern is preset to include a first peak and a second peak adjacent to the first peak and smaller than the first peak, and, when it is determined that a plurality of signals have been received, the detection unit may detect information about a plurality of objects that respectively provide reflections of the plurality of signals as information about the object. With this configuration, information about reflections in a plurality of patterns can be accurately detected by two correlation processes including a correlation process for acquiring the first correlation value and a correlation process for acquiring the second correlation value.

[0012] In this case, the correlation processing unit can change a part of the second pattern used to obtain the second correlation value according to the time elapsed after the transmission of the transmission signal is completed. With this configuration, an appropriate second correlation value can be obtained using an appropriate part of the second pattern according to the time elapsed after the transmission of the transmission signal is completed.

[0013] Furthermore, in this case, when the time elapsed after the transmission of the transmission signal is completed is short, the correlation processing unit can use the terminal side portion of the second pattern to obtain the second correlation value, and when the time elapsed after the transmission of the transmission signal is completed is equal to or longer than the predetermined time, the correlation processing unit uses the entire second pattern to obtain the second correlation value. With this configuration, the portion of the second pattern for obtaining the second correlation value can be appropriately set according to the relationship between the time elapsed after the transmission of the transmission signal is completed and the predetermined time.

[0014] In this case, the predetermined time may be the reverberation time from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides. With this configuration, the second pattern for acquiring the second correlation value can be appropriately set in consideration of the reverberation time.

[0015] In the above-mentioned object detection device, the detection unit may include a distance measurement unit, and the distance measurement unit is configured to calculate the distance to the object based on the difference between the time when the transmission signal is transmitted and the time when the reception signal is received, as the information about the object. With this configuration, the distance to the object can be obtained as the detection result.

[0016] According to another aspect of the present disclosure, an object detection device includes: a transducer having a vibrator capable of transmitting and receiving ultrasonic waves, and configured to transmit, through the vibrator, a transmission signal to which encoding has been performed to give identification information of a predetermined code length, and receive the transmission signal reflected by an object existing in the periphery as a reception signal; a correlation processing unit, the correlation processing unit being configured to obtain a correlation value during a reverberation time period from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides, and determine whether a reception signal to which identification information having a predetermined level or higher similarity with the identification information of the transmission signal has been received based on a comparison result between the correlation value and a threshold value, the correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal; and a detection unit, the detection unit being configured to detect information about the object when it is determined that a reception signal to which identification information having a predetermined level or higher similarity with the identification information of the transmission signal has been received.

[0017] According to the above configuration, it is possible to determine whether the transmission signal is reflected and returned as a reception signal using identification information given to the transmission signal (and the reception signal) during the reverberation time from after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides. Thus, since the reception signal can be detected even before the reverberation time ends, it is possible to provide an object detection device capable of realizing detection of an object existing at a shorter distance.

[0018] According to another aspect of the present disclosure, an object detection device includes: a transducer, the transducer having a vibrator capable of transmitting and receiving ultrasonic waves, and being configured to, through the vibrator, transmit a transmission signal that has been encoded to give identification information of a predetermined code length, and receive the transmission signal reflected by an object existing in the surrounding as a reception signal; a correlation processing unit, the correlation processing unit being configured to obtain a first correlation value after the transmission of the transmission signal is completed, and to obtain a second correlation value, the first correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal, the second correlation value corresponding to the similarity between the first pattern and at least a part of the second pattern, the first pattern corresponding to the time change of the first correlation value, the second pattern being preset to include a first peak and a second peak adjacent to the first peak and smaller than the first peak; and a detection unit, the detection unit being configured to detect information about the object based on a comparison result between the second correlation value and a threshold.

[0019] According to the above configuration, it is possible to provide an object detection device capable of realizing detection of an object existing at a shorter distance by performing two correlation processes including a correlation process for acquiring a first correlation value and a correlation process for acquiring a second correlation value after transmission of a transmission signal is completed.

[0020] A parking assist device according to another aspect of the present disclosure includes: an object detection device installed in a vehicle and including a transducer, a correlation processing unit, and a detection unit, the transducer having a vibrator capable of transmitting and receiving ultrasonic waves and configured to transmit, by the vibrator, a transmission signal to which encoding has been performed to be assigned identification information of a predetermined code length, and receive the transmission signal reflected by an object existing in the periphery as a reception signal, the correlation processing unit configured to acquire a first correlation value from immediately after the transmission of the transmission signal is completed, and determine whether a reception signal assigned identification information having a predetermined level or more of similarity to the identification information of the transmission signal has been received based on a comparison result between the first correlation value and a first threshold value, the first correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal; and a detection unit configured to detect information about the object when determining that a reception signal assigned identification information having a predetermined level or more of similarity to the identification information of the transmission signal has been received; and a parking assist processing unit installed in the vehicle to perform parking assist of the vehicle based on the information about the object detected by the detection unit of the object detection device.

[0021] According to the above configuration, it is possible to determine whether the transmission signal is reflected and returned as the reception signal using the identification information given to the transmission signal (and the reception signal) from immediately after the transmission of the transmission signal is completed. Thus, since the reception signal can be detected even before the reverberation time ends, a parking assist device capable of realizing detection of an object existing at a shorter distance can be provided.

[0022] In the parking assist apparatus described above, the object detection device may include a plurality of object detection devices, and the plurality of object detection devices may simultaneously detect information about the object using different pieces of identification information. With this configuration, since the environment around the vehicle can be quickly and accurately detected based on a plurality of detection results acquired at the same time, rapid and accurate parking assist can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The foregoing and additional features and characteristics of the present disclosure will become more apparent from the following detailed description considered with reference to the accompanying drawings, in which:

[0024] Figure 1 is an exemplary and schematic diagram illustrating the appearance of a vehicle having the object detection apparatus according to the first embodiment (and the second embodiment) as viewed from above;

[0025] Figure 2 is an exemplary and schematic diagram illustrating the configuration of an object detection apparatus according to a first embodiment;

[0026] Figure 3 are exemplary and schematic diagrams illustrating examples of waveforms of signals transmitted and received by the object detection device according to the first embodiment;

[0027] Figure 4 is an exemplary and schematic flowchart illustrating a series of processes performed by the object detection device according to the first embodiment for detecting an object;

[0028] Figure 5 is an exemplary and schematic block diagram illustrating the configuration of a parking assist apparatus including an object detection device according to a modification of the first embodiment;

[0029] Figure 6 is an exemplary and schematic view for explaining the necessity of the second embodiment;

[0030] Figure 7 is an exemplary and schematic diagram illustrating a reference version according to a second embodiment;

[0031] Figure 8 is an exemplary and schematic diagram illustrating the result of secondary correlation processing according to the second embodiment; and

[0032] Fig. 9 is an exemplary and schematic flowchart illustrating a series of processes performed by the object detection apparatus according to the second embodiment for detecting an object. DETAILED DESCRIPTION

[0033] The embodiments disclosed herein will be described below with reference to the accompanying drawings. The configuration of the embodiments to be described below and the actions and results (effects) caused by the configuration are given as examples only and are not limited to the following description.

[0034] <First Embodiment>

[0035] Figure 1 1 is an exemplary and schematic diagram illustrating the appearance of a vehicle 1 having object detection devices 101 to 104 according to the first embodiment (and the second embodiment to be described below) viewed from above. Although described in detail below, the object detection devices 101 to 104 are sensing devices that detect information about an object, such as a person existing in the surroundings (e.g., Figure 2 Obstacle X1 shown in the figure).

[0036] like Figure 1 As shown, object detection devices 101 to 104 are mounted on a vehicle body 2 of a four-wheeled vehicle 1, which includes a pair of left and right front wheels 3F and a pair of left and right rear wheels 3R. More specifically, object detection devices 101 to 104 are arranged at different positions on the rear end of the vehicle body 2, for example, on a rear bumper.

[0037] Furthermore, in the first embodiment, the respective object detection devices 101 to 104 have the same hardware configuration and functions. Therefore, in the following description, for simplicity, the object detection devices 101 to 104 may be collectively referred to as the object detection device 100 in some cases.

[0038] Figure 2 1 is an exemplary and schematic diagram illustrating the configuration of the object detection device 100 according to the first embodiment. Figure 2 As shown, the object detection device 100 includes a transceiver 110 and a controller 120 .

[0039] The transceiver 110 includes a transducer 111. The transducer 111 includes a vibrator 111a such as a piezoelectric element, and transmission and reception of ultrasonic waves are achieved through the vibrator 111a.

[0040] More specifically, the transducer 111 transmits ultrasonic waves generated according to the vibration of the vibrator 111a as a transmission signal, and receives vibrations of the vibrator 111a caused when the ultrasonic waves transmitted as the transmission signal are reflected and returned from an object existing outside as a reception signal. Figure 2 In FIG. 1 , an obstacle X1 disposed on a road surface X2 is illustrated as an object that reflects ultrasonic waves from the transducer 111 .

[0041] Here, in the above technique using the vibrator 111a, since the vibrator 111a continues to vibrate due to inertia even after the transmission of the transmission signal is completed, time (so-called reverberation time) is required until the vibration of the vibrator 111a subsides. Here, when the reception signal is received during the reverberation time, the vibration of the vibrator 111a generated by the reception signal and the residual vibration of the vibrator 111a due to inertia coexist. In this case, since it is difficult to accurately detect only the reception signal due to, for example, a fixed threshold value related to the vibration amplitude, conventionally, detection of the reception signal is avoided until the reverberation time ends.

[0042] However, in a case where an object as a detection target is very close, for example, in a case where the difference between the width of the vehicle and a parking frame (such as a wall) is very small, it is also conceivable that the transmission signal is returned before the reverberation time ends. Therefore, a technology is required that detects a reception signal even before the reverberation time ends, thereby realizing detection of an object existing at a shorter distance.

[0043] Therefore, in the first embodiment, the transceiver 110 and the controller 120 have the following hardware and functions to achieve detection of an object existing at a shorter distance.

[0044] In the first embodiment, the transceiver 110 includes an oscillator 112, a modulator 113, and a demodulator 114 in addition to the transducer 111. These components are implemented in hardware using analog circuits, for example.

[0045] The oscillator 112 oscillates a signal of a predetermined frequency to vibrate the vibrator 111 a of the transducer 111 , and outputs the oscillation signal to the modulator 113 .

[0046] The modulator 113 modulates the signal input from the oscillator 112 based on the signal input from the controller 120, and outputs the modulated signal to the transducer 111 as a voltage signal for vibrating the vibrator 111a. In addition, in the first embodiment, as the modulation method, known methods such as an amplitude modulation method, a phase modulation method, and a frequency modulation method can be used alone or in combination. In addition, in the first embodiment, the modulator 113 can be configured to perform appropriate switching between a plurality of modulation methods based on an instruction from the controller 120.

[0047] The demodulator 114 demodulates the signal input from the transducer 111, and outputs the demodulated signal to the controller 120. A demodulation method corresponding to the modulation method used by the modulator 113 is used.

[0048] The controller 120 includes a storage unit 121, an encoding processing unit 122, a correlation processing unit 123, and a distance measurement unit 124. For example, when the controller 120 is constructed as a processing device having hardware (such as a processor or a memory) similar to that of a general computer, these components are functionally implemented as a result of the processor reading and executing a program stored in the memory (i.e., by the cooperation of hardware and software). In addition, in the first embodiment, each unit constituting the controller 120 can be implemented, for example, in hardware by a dedicated analog circuit.

[0049] The storage unit 121 stores various data used by the controller 120 to implement its functions.

[0050] The coding processing unit 122 performs coding using the modulation of the modulator 113, which assigns identification information of a predetermined code length to the transmission signal. More specifically, the coding processing unit 122 generates a bit string that is a sequence of 0 or 1 bits as identification information unique to the object detection device 100. The length of the bit string corresponds to the code length of the identification information assigned to the transmission signal. The coding processing unit 122 outputs the generated bit string to the modulator 113, and causes the modulator 113 to perform modulation according to each bit of the bit string, thereby achieving coding that assigns the identification information corresponding to the bit string to the transmission signal.

[0051] For example, in the case of using the amplitude modulation method as the modulation method, when a bit string as identification information is input from the encoding processing unit 122, the modulator 113 changes the magnitude of the amplitude of the voltage signal to be output to the transducer 111 according to whether each bit of the bit string is 0 or 1. Similarly, in the case of using the phase modulation method as the modulation method, the modulator 113 changes the phase of the voltage signal to be output to the transducer 111 according to whether each bit of the bit string input from the encoding processing unit 122 is 0 or 1, and in the case of using the frequency modulation method as the modulation method, the modulator 113 changes the frequency of the voltage signal to be output to the transducer 111 according to whether each bit of the bit string input from the encoding processing unit 122 is 0 or 1.

[0052] The correlation processing unit 123 obtains a correlation value corresponding to the similarity (consistency) between the identification information of the transmitted signal and the identification information of the received signal, and determines whether the similarity is above a predetermined level based on the comparison result between the correlation value and the threshold value (first threshold value). When the waveforms of the transmitted signal and the received signal are consistent with each other, the correlation value reaches a peak value exceeding the threshold value. For example, such a correlation value can be obtained (calculated) based on a generally well-known correlation function. The correlation processing unit 123 uses, for example, the correlation value obtained based on the correlation function to determine whether the bit string generated by the encoding processing unit 122 as the identification information assigned to the transmitted signal and the bit string as the identification information specified by the received signal demodulated from the demodulator 114 are similar (consistent) to each other, and based on the determination result, determines whether the received signal demodulated by the demodulator 114 is a transmitted signal reflected and returned by an object.

[0053] The distance measurement unit 124 is a detection unit that detects information about an object (such as whether an object exists or not, or the distance to the object) when it is determined that the similarity is above a predetermined level. More specifically, based on the difference between the time when a transmission signal is transmitted (more specifically, transmission starts) and the time when a reception signal is received (more specifically, reception starts), the distance measurement unit 124 calculates the distance to the object by a so-called time of flight (TOF) method as the information about the object.

[0054] Here, in the first embodiment, as described above, identification information is given to the transmission signal, and based on the correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal, it is determined whether the reception signal demodulated by the demodulator 114 is the transmission signal reflected and returned by the object. Since the identification information is not substantially lost by reflection, even when the reception signal is received during the reverberation time, only the former can be detected from the vibration of the vibrator 111a generated by the reception signal and the residual vibration of the vibrator 111a due to inertia based on the identification information.

[0055] Therefore, in the first embodiment, immediately after the transmission of the transmitted signal is completed, the correlation processing unit 123 obtains the correlation value and determines whether the similarity between the identification information of the transmitted signal and the identification information of the received signal is above a predetermined level based on the comparison result between the correlation value and the threshold (first threshold).

[0056] Figure 3 1 is an exemplary and schematic diagram illustrating an example of the waveform of a signal transmitted and received by the object detection device 100 according to the first embodiment. Figure 3 In the graph illustrated in , the horizontal axis corresponds to time, and the vertical axis corresponds to the signal level (eg, amplitude) of the signal transmitted and received by the object detection device 100 via the transducer 111 (vibrator 111 a ).

[0057] exist Figure 3 In the graph illustrated in FIG. 1 , the solid line L11 indicates an example of an envelope representing the time variation of the signal level of the signal transmitted and received by the object detection device 100, that is, the degree of vibration of the vibrator 111a. It can be read from the solid line L11 that the vibrator 111a is driven to vibrate only during the time T1 from the time t0, the transmission of the transmission signal is completed at the time t1, and thereafter, during the time T2 until the time t2, the vibration of the vibrator continues to decay simultaneously due to inertia. Thus, in Figure 3 In the diagram shown in , the time T2 corresponds to the so-called reverberation time.

[0058] The solid line L11 indicates that the vibration level of the vibrator 111a reaches a peak value exceeding (or, equal to or greater than) a predetermined threshold value Th1 indicated by the single-dot chain line L21 at time t4, at which only time Tp has elapsed since time t0 when the transmission of the transmission signal was started. The threshold value Th1 is an example of a first threshold value, and is a value preset in order to identify whether the vibration of the vibrator 111a is caused by receiving a signal as a detection target object (e.g., Figure 2 Whether the vibration of the vibrator 111a is caused by the reception signal of the transmitted signal reflected and returned by the obstacle X1 shown in the figure, or whether the vibration of the vibrator 111a is caused by the reception of an object other than the detection target object (such as Figure 2 The received signal of the transmitted signal is caused by the reflection and return of the road surface X2) shown in the figure. In addition, although Figure 3 An example in which the threshold value Th1 is set to a fixed value that does not change with the elapse of time is illustrated, but in the first embodiment, the threshold value Th1 may be set to a value that changes with the elapse of time.

[0059] For example, a vibration having a peak value exceeding (or equal to or greater than) the threshold value Th1 may be determined to be caused by receiving a received signal as a transmission signal reflected and returned by the detection target object, and a vibration having a peak value equal to or less than (or lower than) the threshold value Th1 may be determined to be caused by receiving a received signal as a transmission signal reflected and returned by an object other than the detection target object. Thus, it can be read from the solid line L11 that the vibration of the vibrator 111a at time t4 is caused by receiving a received signal as a transmission signal reflected and returned by the detection target object.

[0060] Furthermore, in the solid line L11, after time t4, the vibration of the vibrator 111a attenuates. Therefore, time t4 corresponds to the moment when the reception of the reception signal as the transmission signal reflected and returned by the detection target object is completed, in other words, corresponds to the moment when the transmission signal last transmitted at time t1 is returned as the reception signal. Furthermore, in the solid line L11, time t3 as the starting point of the peak at time t4 corresponds to the moment when the reception of the reception signal as the transmission signal reflected and returned by the detection target object is started, in other words, corresponds to the moment when the transmission signal first transmitted at time t0 is returned as the reception signal. Therefore, in the solid line L11, the time ΔT between time t3 and time t4 is equal to time T1 as the transmission time of the transmission signal.

[0061] Here, in order to obtain the distance to the detection target object by the TOF method, it is necessary to obtain the time Tf between the time t0 when the transmission signal starts to be transmitted and the time t3 when the reception signal starts to be received. The time Tf can be obtained by subtracting the time ΔT equal to the time T1 as the transmission time of the transmission signal from the time Tp as the difference between the time t0 and the time t4 at which the signal level of the reception signal reaches a peak value exceeding the threshold Th1. Since the time t0 can be easily specified as the time when the object detection device 100 starts to operate, and the time T1 is preset by setting, for example, it is important to specify the time t4 in order to obtain the distance to the detection target object by the TOF method.

[0062] Thus, in the first embodiment, as described above, a predetermined encoding is applied to the transmission signal so that identification information of a predetermined code length is assigned to the transmission signal and the reception signal. Then, in the first embodiment, a correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal is obtained, and based on the comparison result between the correlation value and the first threshold value, it is determined whether the similarity is above a predetermined level. In addition, the first threshold value as a comparison target of the correlation value is a value corresponding to the above threshold value Th1. According to this configuration, since the moment when the similarity is determined to be above a predetermined level can be designated as the moment t4 when the reception signal reaches a peak value exceeding the threshold value Th1, the distance to the detection target object can be obtained by the TOF method.

[0063] Incidentally, consider a case where a transmission signal is returned as a reception signal before the reverberation time ends because the detection target object exists at a short distance. Figure 3 In the graph illustrated in , a waveform represented by an envelope like a dotted line L12 appears during a time T2 (reverberation time) between a time t1 and a time t2.

[0064] Since the transmission signal returned during the reverberation time propagates only a short distance and attenuates at a low degree, the vibrator 111a experiences a vibration (see the dotted line L12) larger than the residual vibration due to inertia (see the solid line L11). Thus, in the first embodiment, even during the time from the time t1 immediately after the transmission of the transmission signal is completed to the time t2 when the reverberation time ends, it is possible to determine whether the transmission signal has been reflected by the detection target object and returned as a reception signal using the same method as the method after the above-mentioned time t2.

[0065] However, the signal level of the received signal as the detection target during the time period from immediately after time t1 until time t2 and the signal level of the received signal as the detection target after time t2 are different from each other. Therefore, it is necessary to use the threshold value Th2 (see the double-dashed line L22) as an example of the first first threshold value used during the time period from immediately after time t1 until time t2, and to use the threshold value Th1 (see the single-dashed line L21) as an example of the second first threshold value separately according to time.

[0066] In addition, since the transmission signal attenuates as the propagation distance increases, the signal level of the received signal decreases as the time when the transmission signal returns as the received signal is delayed. Therefore, in the first embodiment, in order to accurately detect the received signal with a signal level that decreases as time passes, the above threshold Th2 is set to decrease as time passes. In addition, although Figure 3 In the first embodiment, the single-dot chain line L21 indicating the threshold value Th1 and the double-dot chain line L22 indicating the threshold value Th2 are continuous at the time t2 when the reverberation time ends. However, the threshold value Th1 and the threshold value Th2 may be set discontinuously.

[0067] In this way, in the first embodiment, not only after the reverberation time ends, but also during the time from immediately after the transmission of the transmission signal is completed until the reverberation time ends, a correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal is acquired, and based on the comparison result between the correlation value and the threshold value, it is determined whether the similarity is a predetermined level or more.

[0068] However, in the first embodiment, the first first threshold value and the second first threshold value are made different, the first first threshold value as the first threshold value to be compared with the correlation value after the end of the reverberation time, and the second first threshold value as the first threshold value to be compared with the correlation value during the time from immediately after the transmission of the transmission signal is completed until the end of the reverberation time. The first first threshold value is a value corresponding to the above threshold value Th1. In addition, the second first threshold value is a value corresponding to the above threshold value Th2, and is set to decrease as time passes. In addition, in the first embodiment, it is assumed that the object detection device 100 (such as the correlation processing unit 123) itself performs switching between the first first threshold value and the second first threshold value. In this case, both the first first threshold value and the second first threshold value are stored in the storage unit 121.

[0069] Furthermore, when determination of similarity is performed based on all identification information (i.e., all bit strings as identification information), the reliability of the determination result increases, but time may be required for calculation. Therefore, for example, when the reverberation time is short, determination of similarity may not be performed based on all identification information. Thus, in the first embodiment, determination of similarity may be performed based on a portion of identification information, for example, only a few bits at the head of a bit string as identification information at least during a time period from immediately after the completion of transmission of the transmission signal until the end of the reverberation time. That is, in the first embodiment, a correlation value corresponding to the similarity between at least a portion of the identification information of the transmission signal and at least a portion of the identification information of the reception signal may be acquired during a time period from immediately after the completion of transmission of the transmission signal until the end of the reverberation time when the vibration of the vibrator 111a due to inertia subsides, and based on a comparison result between the correlation value and a threshold value (a second first threshold value), it may be determined whether the similarity is above a predetermined level.

[0070] Figure 4 is an exemplary and schematic flowchart illustrating a series of processes performed by the object detection device 100 according to the first embodiment for detecting an object.

[0071] exist Figure 4 In the processing flow illustrated in FIG. 4 , first, at S401 , the object detection device 100 (eg, the encoding processing unit 122 , the transducer 111 , the oscillator 112 , and the modulator 113 ) transmits an encoded signal as a transmission signal.

[0072] Then, at S402 , the object detection apparatus 100 (eg, the controller 120 ) determines whether a predetermined time has elapsed, the predetermined time being set as a transmission time for transmitting a signal.

[0073] In S402, when it is determined that the predetermined time has not elapsed, the process returns to S401. On the other hand, when it is determined that the predetermined time has elapsed in S402, the process proceeds to S403.

[0074] At S403, the object detection device 100 (eg, the correlation processing unit 123) obtains a correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal. That is, the object detection device 100 obtains the correlation value immediately after the transmission of the transmission signal is completed.

[0075] Then, at S404, the object detection device 100 (e.g., the relevant processing unit 123) determines whether the reverberation time has ended. This determination can be performed based on the reverberation time preset according to the specifications of the vibrator 111a, for example, or can be performed by monitoring the actual vibration of the vibrator 111a and detecting whether the vibration subsides.

[0076] When it is determined in S404 that the reverberation time has ended, the process proceeds to S405. Then, in S405, the object detection device 100 (e.g., the correlation processing unit 123) determines whether the correlation value acquired in S403 is equal to or greater than a first first threshold value, which is set as a comparison target of the correlation value after the reverberation time ends.

[0077] In S405, when it is determined that the correlation value is less than the first threshold value, it can be determined that the identification information of the transmitted signal and the identification information of the received signal are not similar (consistent) to each other at a predetermined level or more, that is, the transmitted signal has not been returned as a received signal by reflection. Thus, in this case, the process returns to S403 and the correlation value is acquired again.

[0078] On the other hand, when it is determined in S404 that the reverberation time has not ended, the process proceeds to S406. Then, in S406, the object detection device 100 (e.g., the correlation processing unit 123) determines whether the correlation value acquired in S403 is equal to or greater than a second first threshold value, which is set as a comparison target of the correlation value during the reverberation time.

[0079] When it is determined in S406 that the correlation value is less than the second first threshold value, it can be determined that the identification information of the transmitted signal and the identification information of the received signal are not similar (consistent) to each other at a predetermined level or more, that is, the transmitted signal has not been returned as a received signal by reflection. Thus, in this case, the process returns to S403 and the correlation value is acquired again.

[0080] Here, when it is determined in S405 that the correlation value is equal to or greater than the first first threshold value and when it is determined in S406 that the correlation value is equal to or greater than the second first threshold value, it can be determined that the identification information of the transmission signal and the identification information of the reception signal are similar (consistent) to each other at a predetermined level or higher, that is, the transmission signal has been returned as a reception signal by reflection. Thus, in this case, the process proceeds to the next S407.

[0081] In S407, based on the difference between the time when the transmission signal is transmitted (more specifically, transmission starts) and the time when the reception signal is received (more specifically, reception starts) as the transmission signal returned by reflection, the object detection device 100 (e.g., the distance measurement unit 124) acquires (calculates) the distance to the object that has reflected the transmission signal by the TOF method. Then, the process ends.

[0082] As described above, the object detection device 100 according to the first embodiment includes the transceiver 110, the correlation processing unit 123, and the distance measurement unit 124 configured as follows. The transceiver 110 includes a vibrator 111a capable of transmitting and receiving ultrasonic waves, and transmits a transmission signal to which encoding has been performed to give identification information of a predetermined code length, and receives the transmission signal reflected by the object as a reception signal via the vibrator 111a. The correlation processing unit 123 obtains a correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal from immediately after the transmission of the transmission signal is completed, and determines whether the similarity is equal to or greater than a predetermined level corresponding to the threshold value based on a comparison result between the correlation value and a first threshold value (above the first first threshold value or above the second first threshold value). When it is determined that the similarity is above the predetermined level, the distance measurement unit 124 detects information about the object (the distance to the object).

[0083] According to the above configuration, it is possible to determine whether the transmission signal has been reflected and received as a reception signal using the identification information given to the transmission signal (and the reception signal) from immediately after the transmission of the transmission signal is completed. Thus, since the reception signal can be detected even before the reverberation time ends, detection of an object existing at a shorter distance can be achieved.

[0084] In addition, the above configuration is effective when a plurality of object detection devices 100 are provided. Figure 1In the configuration shown in which a plurality of object detection devices 101 to 104 are provided, when the identification information of the object detection devices 101 to 104 is made different, it is possible to prevent one object detection device 100 from erroneously detecting a received signal when a transmission signal transmitted by another object detection device is returned as a received signal. That is, in the first embodiment, the object detection devices 101 to 104 can synchronously detect information about an object using different pieces of identification information. According to this configuration, since the environment around the vehicle 1 can be quickly and accurately detected based on a plurality of detection results acquired at the same time, rapid and accurate parking assistance can be achieved.

[0085] <Modification example>

[0086] In addition, in the above description, the technology of the first embodiment is applied to a structure for detecting information about an object by sending and receiving ultrasonic waves, but the technology of the first embodiment can also be applied to a structure for detecting information about an object by sending and receiving, for example, sound waves, millimeter waves, or electromagnetic waves other than ultrasonic waves.

[0087] In addition, the above-mentioned first embodiment illustrates a configuration in which the object detection device 100 itself controls operations such as switching the modulation method of the transmission signal or switching between the first first threshold and the second first threshold. However, these operations can be implemented under external control, as in the following modified example.

[0088] Figure 5 1 is an exemplary and schematic block diagram illustrating the configuration of a parking assist device 500 including an object detection apparatus 100a according to a modification example of the first embodiment. Figure 5 As shown, the parking assist apparatus 500 includes an object detection device 100 a and a parking assist electronic control unit (ECU) 501 .

[0089] The object detection device 100a is a sensing device that detects information about an object existing in the periphery, such as the object detection device 100 according to the first embodiment described above. In addition, the parking assist ECU 501 is a microcomputer as a parking assist controller that implements parking assistance (including automatic parking). The object detection device 100a and the parking assist ECU 501 are connected to each other via a communication path 550 using a local interconnect network (LIN) or a universal asynchronous receiver / transmitter (UART).

[0090] In this modification, the basic hardware configuration and functions of the transducer 110a and the controller 120a included in the object detection device 100a are substantially the same as those in the above-described first embodiment. However, this modification is different from the above-described first embodiment in that operations performed in the object detection device 100a (such as switching the modulation method of the transmission signal or switching between the first first threshold value and the second first threshold value) are implemented under the control of the parking assist ECU 501. With this configuration, the functions of the object detection device 100a can be simplified.

[0091] <Second Embodiment>

[0092] In the first embodiment described above, information about an object is detected based on (the peak value of) a correlation value obtained as a result of a correlation process. Figure 6 As shown, for example, it is assumed that it is difficult to accurately detect information about an object by considering only a correlation value obtained as a result of a correlation process.

[0093] Figure 6 is an exemplary and schematic diagram for explaining the necessity of the second embodiment. Figure 6 In the example illustrated in FIG, the solid line L610 is an envelope representing a pattern of time changes in the correlation value of the transmitted signal that is returned at a strong level, for example, in response to reflection from a hard object or from an object at a short distance, and the dotted line L620 is an envelope representing a pattern of time changes in the correlation value of the transmitted signal that is returned at a weak level, for example, in response to reflection from a soft object or from an object at a long distance.

[0094] Generally, the envelope of the pattern representing the time variation of the correlation value is known to have a first peak called a main lobe and a second peak called a side lobe, the second peak being adjacent to the first peak and smaller than the first peak. Figure 6 In the example illustrated in FIG. 6 , the solid line L610 has a first peak P611 and second peaks P612 and P613 on both sides of the first peak P611 , and the dotted line L620 has a first peak P621 and second peaks P622 and P623 on both sides of the first peak P621 .

[0095] In addition, Figure 6 In the example illustrated in , for simplicity, there is one side lobe on each side of the main lobe, and the levels (sizes) of the two side lobes are roughly consistent with each other, but, in reality, there is a possibility that there are more than two side lobes on each side, and there is a possibility that the individual side lobes have various levels.

[0096] In addition, Figure 6In the example illustrated in FIG. 6 , for convenience of explanation, the time variation patterns of two types of correlation values ​​according to reflections in two different modes are separately indicated by a solid line L610 corresponding to the reflection in the first mode and a dotted line L620 corresponding to the reflection in the second mode. However, because the reflection modes cannot usually be distinguished in advance, the time variation pattern of the correlation value actually obtained in the correlation process is a combination pattern of the solid line L610 and the dotted line L620.

[0097] Here, among the correlation values ​​obtained by the technique of the above-described first embodiment, the first peak value referred to as the main lobe can be compared with a threshold value (first threshold value). Figure 6 In the example illustrated in , since the first peak P621 of the dotted line L620 corresponding to the reflection in the second mode partially overlaps with the second peak P613 of the solid line L610 corresponding to the reflection in the first mode as viewed in time series, it is difficult to accurately extract only the first peak P621 of the dotted line L620 from the combined pattern. Figure 6 In the example illustrated in , it is difficult to accurately detect information about the object causing reflection in the second mode.

[0098] Thus, even in a case where time changes of a plurality of (e.g., two) correlation values ​​according to reflections in a plurality of (e.g., two) different modes appear in a partially overlapping form, the object detection apparatus 1100 according to the second embodiment (see Figure 2 ) also enables accurate detection of information about each object causing reflection in each mode, such as based on the construction and processing described below Figure 6 As in the example illustrated in .

[0099] Furthermore, the configuration of the object detection apparatus 1100 according to the second embodiment is similar to the configuration of the object detection apparatus 100 according to the above-described first embodiment (see Figure 2 However, in the second embodiment, the functions of the correlation processing unit 1123 and the distance measuring unit 1124 of the controller 1200 are different from those in the first embodiment described above.

[0100] More specifically, in the second embodiment, the correlation processing unit 1123 first obtains a first correlation value corresponding to the similarity between the identification information of the transmitted signal and the identification information of the received signal through the correlation processing as in the first embodiment. Figure 6 In the example illustrated in FIG. 1 , the combination of the solid line L610 and the dotted line L620 corresponds to the time variation of the first correlation value. In addition, in the following description, the first correlation value may be referred to as a main correlation value, and the correlation process for obtaining the main correlation value may be referred to as a main correlation process. The main correlation process may be obtained based on a generally well-known correlation function, etc.

[0101] Then, in the second embodiment, the correlation processing unit 1123 obtains a second correlation value corresponding to the similarity between the first pattern and at least a portion of the second pattern preset as a reference pattern, and the first pattern corresponds to the time change of the first correlation value. The reference pattern is as follows Figure 7 The information illustrated in FIG. 1 is obtained by estimating in advance the relationship between the time variation of the main correlation value between the main lobe and the side lobe. In addition, in the following description, the second correlation value may be referred to as a secondary correlation value, and the correlation processing for obtaining the secondary correlation value may be referred to as a secondary correlation processing. For example, as in the main correlation processing, the secondary correlation processing may also be obtained based on a generally well-known correlation function, etc.

[0102] Figure 7 2 is an exemplary and schematic diagram illustrating an example of a reference type according to the second embodiment. Figure 7 In the example shown in FIG. , the solid line L700 corresponds to the reference pattern.

[0103] like Figure 7 As shown, the reference pattern indicated by the solid line L700 is Figure 6 Each of the solid line L610 and the dotted line L620 illustrated in FIG. 6 includes a first peak P701 and a second peak P702 in a similar manner, the second peak P702 being adjacent to the first peak P701 and smaller than the first peak P701 .

[0104] Therefore, when the reference pattern indicated by the solid line L700 and Figure 6 When performing (secondary) correlation processing on the combined pattern of the solid line L610 and the dotted line L620 shown in the figure, information on the pattern indicated by the solid line L610 and information on the pattern indicated by the dotted line L620 can be obtained from the combined pattern of the solid line L610 and the dotted line L620 based on the similarity between the two, which are separated from each other at a certain level. That is, according to the secondary correlation processing, information separated at a certain level for each mode can be obtained from the information (the above main correlation value) in which fragments of information on reflections in multiple modes coexist in a state in which they are indistinguishable from each other, as shown below Figure 8 shown.

[0105] Figure 8 2 is an exemplary and schematic diagram illustrating the result of the secondary correlation process according to the second embodiment. Figure 8 In the example shown in the figure, the solid line L801 and the Figure 6 The solid line L610 and Figure 7 The solid line L700 shown in the figure corresponds to the time variation of the secondary correlation value that appears as a result of the secondary correlation processing performed, and the dotted line L802 corresponds to the time variation of the secondary correlation value that appears as a result of the secondary correlation processing performed. Figure 6 The dashed line L620 and Figure 7 The solid line L700 shown in the figure corresponds to the pattern of time variation of the secondary correlation value that appears as a result of the secondary correlation processing performed.

[0106] In addition, Figure 8 In the example shown in FIG. 8 , for convenience of explanation, the time variation of the secondary correlation value is divided and shown by a solid line L801 and a dotted line L802. Figure 6 The relationship between the solid line L610 and the dotted line L602 shown in the figure is similar, and the time variation pattern of the secondary correlation value actually obtained in the secondary correlation processing is a combination of the solid line L801 and the dotted line L802.

[0107] However, the pattern of time variation of the secondary correlation value actually obtained in the secondary correlation processing is a form in which a plurality of (eg, two) patterns having peaks at different positions in the time series are separated from each other at a certain level. Figure 8 In the example illustrated in , the pattern of the time variation of the secondary correlation value is divided at a certain level into a pattern indicated by a solid line L801 and a pattern indicated by a dotted line L802.

[0108] Here, the pattern indicated by the solid line L801 is due to Figure 6 The solid line L610 and Figure 7 The solid lines L700 shown in the figure are similar to each other, and the dotted line L802 is due to the fact that Figure 6 The dashed line L620 and Figure 7 The pattern appears due to the fact that the solid lines L700 shown in the figure are similar to each other. Since the pattern indicated by the solid line L801 and the pattern indicated by the dotted line L802 reach peaks at different positions in the time series, it can be seen from Figure 8 Reflections in two different modes are detected in the quadratic correlation values ​​shown in FIG.

[0109] As described above, according to the secondary correlation processing, information about reflection in multiple modes separated at a certain level for each reflection mode can be obtained. Therefore, when an appropriate threshold value Th800 is set and the threshold value Th800 is compared with the secondary correlation value, information about reflection in each mode can be immediately and appropriately detected. In addition, the threshold value Th800 is an example of a "second threshold value".

[0110] For example, in Figure 8 In the example illustrated in FIG, two patterns can be detected as patterns having peaks with a level equal to or greater than the threshold value Th800, including a pattern indicated by a solid line L801 and a pattern indicated by a dotted line L802. Figure 8 In the example illustrated in FIG. 1 , a transmitted signal that is reflected in two different modes and returned as two different types of received signals can be detected.

[0111] Then, by considering the time when the transmission signal is transmitted and the time when each of the two different types of reception signals is received, information about each object that causes reflection in the above two types of modes can be detected. That is, when the difference between the time when the transmission signal is transmitted and the time when the first reception signal is received is considered, the distance to the object that causes reflection in the first mode can be detected, and when the difference between the time when the transmission signal is transmitted and the time when the second reception signal is received is considered, the distance to the object that causes reflection in the second mode can be detected.

[0112] As described above, according to the second embodiment, even in a case where temporal changes in a plurality of primary correlation values ​​corresponding to reflections in a plurality of different modes appear in a partially overlapping manner, information about each object causing reflection in each mode can be accurately detected based on the secondary correlation values.

[0113] That is, in the second embodiment, after obtaining the primary correlation value, the correlation processing unit 1123 obtains a secondary correlation value corresponding to the similarity between the first pattern and at least a portion of the second pattern preset as a reference pattern, the first pattern corresponding to the time change of the primary correlation value. Then, the distance measurement unit 1124 detects information about the object (the distance to the object) based on the comparison result between the secondary correlation value and the second threshold value.

[0114] More specifically, after acquiring the primary correlation value, the correlation processing unit 1123 acquires the secondary correlation value, and based on the comparison result between the secondary correlation value and the second threshold value, determines whether a plurality of signals have been received as received signals to which identification information having a predetermined level or higher similarity with identification information of the transmitted signal is assigned. Then, when it is determined that a plurality of signals are received, the distance measurement unit 1124 detects information about a plurality of objects that respectively provide reflections of the plurality of signals (the distance from each of the plurality of objects) as information about the object.

[0115] Incidentally, as described above, from immediately after the transmission of the transmission signal is completed (e.g., immediately after Figure 3 Focusing on the vibrator 111a from the time t1 in the reverberation time (after the time t1 in the reverberation time) until the end of the reverberation time, it is easy to detect a vibration (see the dotted line L12) larger than the residual vibration due to inertia (see the solid line L11), but it is difficult to detect a vibration smaller than the residual vibration due to inertia (see the solid line L11). Therefore, because it is not always possible to accurately detect all the time changes in the signal level of the received signal within the reverberation time, the main correlation value in the reverberation time may not be said to include all the main lobe and the side lobe as usual (i.e., in a manner similar to the entire reference pattern).

[0116] Thus, in the second embodiment, the correlation processing unit 1123 changes a portion of the reference pattern used to obtain the secondary correlation value according to the time that has elapsed after the transmission of the transmission signal is completed. For example, when the time that has elapsed after the transmission of the transmission signal is completed is equal to or longer than the reverberation time, the main correlation value is expected to show a pattern similar to the entire reference pattern because the entire time variation of the signal level of the received signal can be expected to be detected. On the other hand, when the time that has elapsed after the transmission of the transmission signal is completed is less than the reverberation time, the main correlation value is expected to show a pattern similar to only the terminal side portion of the reference pattern in the time series because only the terminal side portion after the end of the reverberation time can be expected to be detected among the time variation of the signal level of the received signal. Thus, in the second embodiment, as Figure 7 As shown, in the former case, the correlation processing unit 1123 uses the entire part W700 of the reference pattern indicated by the solid line L700 to obtain the secondary correlation value, and in the latter case, the correlation processing unit 1123 uses the terminal side part W701 as a part of the reference pattern indicated by the solid line L700 to obtain the secondary correlation value.

[0117] That is, in the second embodiment, when the time elapsed after the transmission of the transmission signal is completed is short, the correlation processing unit 1123 uses the terminal side portion of the reference pattern to obtain the secondary correlation value, and when the time elapsed is equal to or longer than the predetermined time, the entire reference pattern is used to obtain the secondary correlation value. In addition, the predetermined time can be set to coincide with the reverberation time from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator 111a due to inertia subsides. By setting in this manner, an appropriate secondary correlation value can be obtained using an appropriate reference pattern according to the time elapsed after the transmission of the transmission signal is completed.

[0118] Fig. 9 is an exemplary and schematic flowchart illustrating a series of processes performed by the object detection device 1100 according to the second embodiment for detecting an object.

[0119] exist Fig. 9 In the processing flow illustrated in FIG. 1 , first, at S901 , the object detection device 1100 (eg, the transducer 111 ) transmits a transmission signal. The transmission signal is encoded to include identification information of a predetermined code length as in the first embodiment described above.

[0120] Then, at S902, the object detection device 1100 (eg, the transducer 111) receives a reception signal. Since the reception signal is a transmission signal reflected and returned by an object, the reception signal can be encoded into identification information including a predetermined code length in the same manner as the transmission signal.

[0121] Then, at S903 , the object detection device 1100 (eg, the correlation processing unit 1123 ) acquires a main correlation value corresponding to the similarity between the identification information of the transmission signal transmitted at S901 and the identification information of the reception signal received at S902 .

[0122] Then, in S904 , the object detection device 1100 (eg, the correlation processing unit 1123 ) obtains a secondary correlation value corresponding to the similarity between the time variation pattern of the primary correlation value obtained in S903 and a preset reference pattern.

[0123] Then, at S905, the object detection device 1100 (e.g., the correlation processing unit 1123) performs threshold processing of comparing the secondary correlation value acquired at S904 with the above-mentioned predetermined second threshold value. In the threshold processing, based on the comparison result between the secondary correlation value and the second threshold value, it is determined whether a plurality of signals have been received as reception signals to which information on reflections in a plurality of modes, more specifically, information having a predetermined level or higher of similarity with identification information of the transmission signal, has been given.

[0124] Then, at S906, the object detection device 1100 (e.g., the distance measurement unit 1124) acquires the distance to the object based on the result of the threshold processing at S905. More specifically, when it is determined that a plurality of signals have been received in the threshold processing at S905, the object detection device 1100 acquires information about a plurality of objects that respectively provide reflections of a plurality of signals (the distance to each of the plurality of objects) as information about the object. Then, the processing ends.

[0125] As described above, the object detection device 1100 according to the second embodiment includes a correlation processing unit 1123 and a distance measurement unit 1124. After the transmission of the transmission signal is completed, the correlation processing unit 1123 obtains a primary correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal, and obtains a secondary correlation value corresponding to the similarity between at least a part of the first pattern and a reference pattern, the first pattern corresponding to the time change of the primary correlation value, and the reference pattern as a second pattern preset to include a first peak and a second peak, the second peak being adjacent to the first peak and smaller than the first peak. The distance measurement unit 1124 detects information about the object (the distance to the object) based on the comparison result between the secondary correlation value and the second threshold.

[0126] More specifically, in the second embodiment, after obtaining the main correlation value, the correlation processing unit 1123 obtains a first pattern corresponding to the time variation of the main correlation value (see Figure 6 ) and the reference type as the default second type (see Figure 7 ) corresponds to the secondary correlation value (see Figure 8 ), and determines whether a plurality of signals have been received as received signals to which identification information having a similarity equal to or greater than a predetermined level with the identification information of the transmitted signal has been assigned. Then, when it is determined that a plurality of signals have been received, the distance measurement unit 1124 detects information about a plurality of objects that respectively provide reflections of the plurality of signals (distances from each of the plurality of objects) as information about the object.

[0127] According to the above construction, by performing two correlation processes, detection of objects existing at a shorter distance can be achieved, and information about reflections in multiple modes can be accurately detected. The two correlation processes include correlation processing for obtaining a first correlation value and correlation processing for obtaining a second correlation value after the transmission of the transmission signal is completed.

[0128] Here, in the second embodiment, the correlation processing unit 1123 changes a part of the reference pattern used to obtain the secondary correlation value according to the time elapsed after the transmission of the transmission signal is completed. According to this configuration, an appropriate part of the reference pattern can be used to obtain an appropriate secondary correlation value according to the time elapsed after the transmission of the transmission signal is completed.

[0129] In addition, in the second embodiment, when the time elapsed after the transmission of the transmission signal is completed is short, the correlation processing unit 1123 uses the terminal side part of the reference pattern to obtain the secondary correlation value, and when the elapsed time is equal to or longer than the predetermined time, the entire reference pattern is used to obtain the secondary correlation value. According to this configuration, the part of the reference pattern used to obtain the secondary correlation value can be appropriately set according to the relationship between the time elapsed after the transmission of the transmission signal is completed and the predetermined time.

[0130] In the second embodiment, for example, the predetermined time is the reverberation time from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides. According to this configuration, the part of the reference pattern for acquiring the secondary correlation value can be appropriately set in consideration of the reverberation time.

[0131] <Modification of Second Embodiment>

[0132] It goes without saying that the same modification as that of the first embodiment described above can be applied to the second embodiment. That is, the technology of the second embodiment can also be applied to a configuration in which information about an object is detected by transmission and reception of sound waves, millimeter waves, electromagnetic waves, etc. In addition, the various processes in the second embodiment can be implemented in such a manner that the object detection device performs the various processes under its control, or the object detection device performs the various processes under the control of the parking assist controller connected thereto.

[0133] Although the embodiments and modifications disclosed herein have been illustrated above, the above embodiments and modifications thereof are given by way of example only and are not intended to limit the scope of the present disclosure. Such novel embodiments and modifications may be implemented in various other modes, and various omissions, substitutions, combinations, and changes may be made without departing from the gist of the present disclosure. In addition, the embodiments and modifications may be included in the scope and gist of the present disclosure, and are included in the disclosure described in the claims and their equivalents.

[0134] The principles, preferred embodiments and modes of operation of the present invention have been described in the foregoing description. However, the invention, which is intended to be protected, should not be construed as being limited to the specific embodiments disclosed. Further, the embodiments described herein should be considered illustrative rather than restrictive. Modifications and variations may be made by other means and equivalents employed without departing from the spirit of the present invention. Thus, it is expressly intended to cover all such modifications, variations and equivalents that fall within the spirit and scope of the present invention as defined in the claims.

Claims

1. An object detection device (100, 100a, 101, 102, 103, 104), characterized in that: Include: a transducer (110) having a vibrator (111a) capable of transmitting and receiving ultrasonic waves, and configured to transmit, through the vibrator, a transmission signal to which identification information has been encoded so as to have a predetermined code length, and to receive, as a reception signal, the transmission signal reflected by an object (X1) existing in the periphery; a correlation processing unit (123) configured to, starting from immediately after the transmission of the transmission signal is completed, acquire a first correlation value, and determine whether the reception signal to which the identification information having a predetermined level or higher similarity with the identification information of the transmission signal has been received based on a comparison result between the first correlation value and a first threshold value, the first correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal; as well as a detection unit (124) configured to detect information about the object when determining that the received signal to which the identification information having the predetermined level or higher similarity with the identification information of the transmitted signal has been received, wherein the correlation processing unit acquires the first correlation value during a reverberation time (T2) from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides, and determines whether the received signal to which the identification information having a predetermined level or higher similarity with the identification information of the transmission signal has been received based on a comparison result between the first correlation value and the first threshold, the first correlation value corresponding to the similarity between at least a part of the identification information of the transmission signal and at least a part of the identification information of the reception signal.

2. The object detection device according to claim 1, characterized in that in, The correlation processing unit sets a first first threshold as the first threshold to be compared with the first correlation value after the reverberation time ends, and sets a second first threshold as the first threshold to be compared with the first correlation value during a time from immediately after the transmission of the transmission signal is completed until the reverberation time ends, so as to be different from each other.

3. The object detection device according to claim 2, characterized in that in, The second first threshold value is set to become smaller as time passes.

4. The object detection device according to claim 1, characterized in that in, After acquiring the first correlation value, the correlation processing unit acquires a second correlation value, and determines whether a plurality of signals have been received as the received signals to which the identification information having the predetermined level or higher similarity with the identification information of the transmitted signal is assigned, based on a comparison result between the second correlation value and a second threshold value, the second correlation value corresponding to the similarity between a first pattern and at least a part of a second pattern, the first pattern corresponding to a time change of the first correlation value, the second pattern being preset to include a first peak and a second peak adjacent to the first peak and smaller than the first peak, and When it is determined that a plurality of signals have been received, the detection unit detects information on a plurality of objects that respectively provide reflections of the plurality of signals as the information on the object.

5. The object detection device according to claim 4, characterized in that in, The correlation processing unit changes a part of the second pattern for acquiring the second correlation value according to a time elapsed after the transmission of the transmission signal is completed, when the time elapsed after the transmission of the transmission signal is completed is short, the correlation processing unit uses the terminal side part of the second pattern to obtain the second correlation value, and when the time elapsed after the transmission of the transmission signal is completed is equal to or longer than a predetermined time, the correlation processing unit uses the entire second pattern to obtain the second correlation value, The predetermined time is a reverberation time from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides, and The detection unit includes a distance measurement unit configured to calculate a distance to the object as information on the object based on a difference between a time at which the transmission signal is transmitted and a time at which the reception signal is received.

6. An object detection device (1100), characterized in that: Include: a transducer (110) having a vibrator (111a) capable of transmitting and receiving ultrasonic waves, and configured to transmit, through the vibrator, a transmission signal to which identification information has been encoded so as to have a predetermined code length, and to receive, as a reception signal, the transmission signal reflected by an object (X1) existing in the periphery; a correlation processing unit (1123), the correlation processing unit being configured to obtain a first correlation value after the transmission of the transmission signal is completed, and to obtain a second correlation value, the first correlation value corresponding to the similarity between the identification information of the transmission signal and the identification information of the reception signal, the second correlation value corresponding to the similarity between a first pattern and at least a part of a second pattern, the first pattern corresponding to a time variation of the first correlation value, the second pattern being preset to include a first peak value and a second peak value adjacent to the first peak value and smaller than the first peak value; as well as a detection unit configured to detect information about the object based on a comparison result between the second correlation value and a threshold value, wherein the correlation processing unit acquires the first correlation value during a reverberation time (T2) from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides, and determines whether the received signal to which the identification information having a predetermined level or higher similarity with the identification information of the transmission signal has been received based on a comparison result between the first correlation value and a first threshold value, the first correlation value corresponding to the similarity between at least a part of the identification information of the transmission signal and at least a part of the identification information of the reception signal.

7. A parking assistance device (500), characterized in that: Include: An object detection device (100, 100a, 101, 102, 103, 104) is installed on a vehicle (1) and comprises: a transducer (110) having a vibrator (111a) capable of transmitting and receiving ultrasonic waves and configured to transmit, through the vibrator, a transmission signal to which identification information having been encoded to be given a predetermined code length and to receive, as a received signal, the transmission signal reflected by an object (X1) existing in the surroundings; and a correlation processing unit (123) configured to obtain, from immediately after the transmission of the transmission signal is completed, a first correlation signal; value, and based on a comparison result between the first correlation value and a first threshold value, determining whether the received signal assigned with the identification information having a predetermined level or higher similarity with the identification information of the transmitted signal has been received, the first correlation value corresponding to the similarity between the identification information of the transmitted signal and the identification information of the received signal; and a detection unit (124), the detection unit being configured to detect information about the object when it is determined that the received signal assigned with the identification information having the predetermined level or higher similarity with the identification information of the transmitted signal has been received; and a parking assistance processing unit (501) installed in the vehicle to perform parking assistance of the vehicle based on the information on the object detected by the detection unit of the object detection device, wherein the correlation processing unit acquires the first correlation value during a reverberation time (T2) from immediately after the transmission of the transmission signal is completed until the vibration of the vibrator due to inertia subsides, and determines whether the received signal to which the identification information having a predetermined level or higher similarity with the identification information of the transmission signal has been received based on a comparison result between the first correlation value and the first threshold, the first correlation value corresponding to the similarity between at least a part of the identification information of the transmission signal and at least a part of the identification information of the reception signal.

8. The parking assist device according to claim 7, characterized in that: in, The object detection device comprises a plurality of object detection devices, and The plurality of object detection devices simultaneously detect the information about the object using different segments of the identification information.

Images