JP2009115735A - Distance-measuring device, distance measurement method, distance measurement program, and recording medium - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely estimate a distance when using general speakers and microphones or even in a noisy environment that uses a distance measuring device. <P>SOLUTION: The distance-measuring device includes a signal generation section, a generation signal audible sound eliminating filter, a microphone signal audible sound elimination filter, an impulse response calculation section, and a peak detection section, thus measuring a distance by speakers and microphones. The generation signal audible sound eliminating filter eliminates audible sound components from signals generated from the signal-generating section for outputting. The microphone signal audible sound eliminating filter eliminates audible sound components from microphone signals. An impulse response calculating section obtains an impulse response from the output signal of the generated signal audible sound eliminating filter and that of the microphone signal audible sound eliminating filter. A peak detection section detects a peak from the output of the impulse response calculating section and obtains a times up to a peak after a signal is outputted from the generated signal audible sound eliminating filter for obtaining distance information. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a distance measuring device, a distance measuring method, a distance measuring program, and a recording medium that measure a distance using a speaker and a microphone.

  A distance measuring device using ultrasonic waves has been proposed in order to identify a speaker's position and realize realistic communication in a video conference system or the like (Non-Patent Document 1). FIG. 1 is a configuration example of a conventional distance measuring apparatus, and FIG. 2 is a diagram illustrating a state of a signal in each configuration unit. A conventional distance measuring apparatus 900 includes a 40 kHz transmission unit 910, a pulse generation unit 920, a switch unit 930, a rectification / smoothing unit 940, a threshold comparison unit 950, and a counter unit 960. The distance measuring device 900 is connected to an ultrasonic sensor transmitter 970 and an ultrasonic sensor receiver 980.

  The distance measuring device 900 measures the time until the ultrasonic wave output from the ultrasonic sensor transmitter 970 reaches the ultrasonic sensor receiver 980, and obtains the distance by multiplying the time by the speed of sound. The ultrasonic wave to be transmitted is obtained by outputting a single frequency such as 40 kHz in a pulse form for a very short time. When the level of the signal received by the ultrasonic sensor receiver exceeds a preset threshold, it is detected that an ultrasonic wave has been received. The time from the time when the ultrasonic wave is transmitted to the time when reception is detected is the propagation time of the ultrasonic wave, and the distance can be calculated by multiplying this time by the speed of sound.

  Next, a specific operation of the distance measuring apparatus 900 will be described. The 40 kHz transmission unit 910 continuously generates and outputs a 40 kHz sine wave or rectangular wave as shown in FIG. The pulse generation unit 920 generates a rectangular pulse for a short time (several tens to several hundreds of milliseconds) as shown in FIG. The switch unit 930 is turned on only while the pulse is generated by the pulse generation unit 920, passes the output of the 40 kHz transmission unit 910, and sends it to the ultrasonic sensor transmitter 970. When no pulse is generated, it is in the OFF state, and the output of the 40 kHz transmission unit 910 does not pass through. The ultrasonic sensor transmitter 970 emits the output (FIG. 2C) of the 40 kHz transmission unit 910 that has passed through the switch unit 930 to the space.

  The ultrasonic sensor receiver 980 receives an ultrasonic signal and outputs a signal as shown in FIG. The rectifying / smoothing unit 940 performs full-wave rectification on the output of the ultrasonic sensor receiver 980 and smoothes the time to obtain a signal as shown in FIG. The threshold comparison unit 950 compares a predetermined threshold with the output of the rectifying / smoothing unit 940, and when the output of the rectifying / smoothing unit 940 exceeds the threshold, a signal indicating that there is a received signal (for example, , The signal shown in FIG. 2 (F). The counter unit 960 starts counting of the counter at the rising edge of the pulse generated by the pulse generation unit 920, and stops counting when the threshold comparison unit 950 outputs a signal indicating that there is a received signal. The distance between the ultrasonic sensor transmitter 970 and the ultrasonic sensor receiver 980 is determined by multiplying the time obtained from the counter value by the speed of sound.

In the case of a conventional distance measuring device, an ultrasonic sensor transmitter 970 or an ultrasonic sensor receiver 980 is placed around (or provided in) a microphone used by a speaker, and the ultrasonic sensor receiver 980 or By arranging the ultrasonic sensor transmitter 970, the distance and direction from the camera to the microphone are detected. These pieces of information are used for giving a sense of reality, camera orientation, zoom control, and the like.
Hideaki Oda, Kazunori Kobayashi, Haruhide Hokari, Masaharu Shimada, “Position Estimation Using Ultrasound”, Nihon Kogyo Publishing, Measurement Technology, December 1998, pp.50-54.

  The above-described conventional distance measuring apparatus is based on the premise that an ultrasonic transmitter and receiver are used, and thus a transmitter and receiver only for distance measurement are necessary. In this way, when a dedicated transmitter and receiver are used, measurement errors due to transient characteristics of ultrasonic elements and attenuation when propagating through space can be predicted to some extent, and measurement errors can be reduced. . On the other hand, when a general speaker and microphone are used instead of the transmitter and receiver for ultrasonic waves, it is impossible to predict how much measurement error will occur, so the measurement error cannot be reduced, resulting in a large measurement error. There was a problem.

In addition, since the conventional distance measuring device uses only the rising portion of the ultrasonic wave, if there is noise, the level of the rising portion changes due to the influence of the noise, resulting in a large error.
The object of the distance measuring apparatus of the present invention is to realize highly accurate distance estimation even when a general speaker and microphone are used or in a noisy environment.

  The distance measuring apparatus of the present invention includes a signal generation unit, a generated signal audible sound removal filter unit, a microphone signal audible sound removal filter unit, an impulse response calculation unit, and a peak detection unit, and measures a distance using a speaker and a microphone. The signal generation unit generates a signal including a band of 20 kHz or more. The generated signal audible sound removing filter unit removes an audible sound component from the signal generated by the signal generating unit, and outputs a signal to be supplied to the speaker. The microphone signal audible sound removal filter unit removes an audible sound component from the signal from the microphone. The impulse response calculation unit obtains an impulse response from the output signal of the generated signal audible sound removal filter unit and the output signal of the microphone signal audible sound removal filter unit. The peak detection unit detects a peak from the output of the impulse response calculation unit, obtains a time from when the signal is output from the generated signal audible sound removal filter unit to the peak, and obtains distance information.

  The audible sound mixing unit may be disposed between the generated signal audible sound removal filter unit and the speaker. The audible sound mixing unit adds the input audible sound signal to the output from the generated signal audible sound removal filter unit, and outputs a signal to be supplied to the speaker. Further, an audible sound passing filter unit that extracts only an audible sound component from the signal from the microphone may be provided.

  According to the distance measuring apparatus of the present invention, an impulse response is obtained from a transmission signal and a received signal, and the distance between the speaker and the microphone is obtained from the result, so that the distance can be measured with high accuracy even with a general speaker and microphone. Even in an environment with noise, the distance can be measured with high accuracy by increasing the signal emission time.

  In addition, it is possible to superimpose a person's speaking voice in the audible sound mixing unit and extract the sound from the sound received by the microphone with the audible sound passing filter unit, so a configuration unit for distance measurement is added around the speaker and microphone. Even without it, it is easy to grasp the distance from the speaker to the speaker. In particular, even when a microphone (speaker) moves during the conference, the change in distance can be recognized. In addition, since the conventional distance measuring apparatus uses an ultrasonic transmitter and receiver, the transmission signal is limited to one type, and a plurality of distances cannot be measured simultaneously. However, since the distance measuring device of the present invention uses a general speaker and microphone, a plurality of distances can be measured simultaneously by emitting uncorrelated signals from a plurality of speakers. If the distance from a plurality of speakers is known, the position of the microphone (speaker) can also be known. Therefore, even if the microphone (speaker) moves during the conference, it can follow.

Below, in order to avoid duplication of description, the same number is given to the structural part which has the same function, and the process step which performs the same process, and description is abbreviate | omitted.
[First Embodiment]
FIG. 3 shows an example of a functional configuration of the distance measuring apparatus according to the first embodiment, and FIG. 4 shows a processing flow of the distance measuring apparatus. FIG. 5 is a diagram illustrating a state of signals in each component of the distance measuring apparatus 100. The distance measuring apparatus 100 includes a signal generation unit 110, a generated signal audible sound removal filter unit 120, a microphone signal audible sound removal filter unit 130, an impulse response calculation unit 140, and a peak detection unit 150, and the speaker 10 and the microphone 20 are used. Measure distance.

  The signal generator 110 generates a signal having a component in a band of 20 kHz or higher, such as an M-sequence signal, a TSP signal, or white noise (S110). FIG. 5A is an image of an output signal from the signal generation unit 110. A constant signal is generated for a predetermined time. The frequency component of the generated signal ranges from the audible range (generally 20 kHz or less) to the ultrasonic range (generally 20 kHz or more). The generated signal audible sound removal filter unit 120 removes an audible sound component (20 kHz or less) from the signal generated by the signal generation unit 110, and outputs a signal to be supplied to the speaker 10 (S120). FIG. 5B is an image of the output signal of the generated signal audible sound removal filter unit 120. The audible sound component (20 kHz or less) is removed from the signal generated by the signal generator 110. The speaker 10 emits the supplied signal, and the microphone 20 receives the sound. FIG. 5C is an image of an output signal from the microphone 20. Since a human voice or the like is also input to the microphone, sound in the audible range is included as shown in FIG. 5C, and the intensity changes with time.

  The microphone signal audible sound removal filter unit 130 removes an audible sound component (20 kHz or less) from the signal from the microphone 20 (S130). FIG. 5D shows an image of an output signal from the microphone signal audible sound removal filter unit 130. By removing the audible sound component, the signal has a substantially constant intensity over time. The impulse response calculation unit 140 obtains an impulse response from the output signal of the generated signal audible sound removal filter unit 120 and the output signal of the microphone signal audible sound removal filter unit 130 (S140). FIG. 5E is an image of the output from the impulse response calculation unit 140. The calculation method of the impulse response is shown in non-patent literature (Toshiro Oga, Yoshio Yamazaki, Yutaka Kaneda, “Acoustic system and digital processing”, IEICE, 1995, pp.158-160.) As shown, a method is known in which frequency transmission characteristics are obtained from a power spectrum of a sound source and a cross power spectrum between the sound source and the sound receiving point, and are calculated by inverse Fourier transform.

For example, the impulse response calculation unit 140 may be configured as shown in FIG. In this example, the impulse response calculation unit 140 includes a generation signal frequency domain conversion unit 141, a microphone signal frequency domain conversion unit 142, a conjugate unit 143, a multiplication unit 144, and an inverse frequency domain conversion unit 145. When the output of the generated signal frequency domain converting means 141 is A, the output of the microphone signal frequency domain converting means 142 is B, and the impulse response between the speaker 10 and the microphone 20 is H, the relationship of B = HA is established. At this time, the output of the conjugating means 143 is A ^* (where “ ^* ” indicates conjugation). Therefore, the output of the multiplication means 144 is BA ^* . That is, HAA ^* . The inverse frequency domain transform unit 145 transforms the output of the multiplication unit 144 into the time domain. The AA ^* portion of the output of the multiplication means 144 is the power spectrum of the output A from the generated signal audible sound elimination filter unit 120. Therefore, in the time domain, H and HAA ^* differ only in amplitude but have the same peak position. It is. In the present invention, since the position of the peak only needs to be known, the configuration of FIG. 6 is sufficient even if it is not divided by AA ^* .

  The peak detection unit 150 detects a peak from the output of the impulse response calculation unit 140, obtains a time from when the signal is output from the generated signal audible sound removal filter unit 120 to the peak, and obtains distance information (S150). The time from time t = 0 to the peak in FIG. 5E is the sound propagation time from the speaker 10 to the microphone 20. The speed of sound v (m / s) is v = 331.5 + 0.61T using temperature (Celsius) T degrees. Assuming that the temperature of the conference room is about 20 degrees, the propagation time may be multiplied as the speed of sound 344 (m / s) to obtain the distance. Alternatively, a temperature sensor may be disposed between the speaker 10 and the microphone 20, the sound speed may be obtained from the temperature, and the propagation time may be multiplied.

According to the distance measuring apparatus 100, an impulse response (or a signal whose peak position matches the impulse response) is obtained from the transmission signal and the reception signal, and the distance between the speaker and the microphone is obtained from the result. But distance can be measured with high accuracy. Even in an environment with noise, the distance can be measured with high accuracy by increasing the signal emission time.
Further, a plurality of signal generators 110, a generated signal audible sound removal filter unit 120, a speaker 10, an impulse response calculator 140, and a peak detector 150 are provided, and one microphone can be obtained by emitting uncorrelated signals from a plurality of speakers. Can measure multiple distances simultaneously. Since the distance between one microphone and a plurality of speakers is known, the position of the microphone can be detected when the position of the speaker is known (for example, when the speaker is fixed).

[Modification]
The conjugate means 143 in FIG. 6 determines the conjugate of the output A of the generated signal frequency domain transform means 141, but may include a conjugate means 143 ′ instead of the conjugate means 143. In this case, since the conjugate of the output B of the microphone signal frequency domain conversion unit 142 is obtained, the output of the multiplication unit 144 is B ^* A. That is, H ^* A ^* A. Also in this case, the peak position of the output signal from the inverse frequency domain converting means 145 is the same as the peak position of the impulse response. Therefore, the same effect as the first embodiment can be obtained.

[Second Embodiment]
FIG. 7 shows an example of a functional configuration of the distance measuring apparatus according to the second embodiment, and FIG. 8 shows a processing flow of the distance measuring apparatus. The distance measuring device 200 is different from the distance measuring device 100 in that an audible sound mixing unit 160 and an audible sound passing filter unit 170 are also provided. The audible sound mixing unit 160 adds a signal of the input audible sound (such as a human voice) to the output from the generated signal audible sound removal filter unit 120, and outputs a signal to be supplied to the speaker 10 (S160). In addition, the audible sound passing filter unit 170 extracts only an audible sound component (such as an audio signal) from the signal from the microphone (S170).

  The distance measuring device 200 can superimpose a person's speaking voice by the audible sound mixing unit 160 and can extract the sound from the sound received by the microphone 20 by the audible sound passing filter unit 170. Even without adding a distance measurement component, the distance from the speaker 10 to the microphone 20 (the speaker is generally near the microphone 20) can be grasped. In particular, even when the speaker moves during the conference, the microphone usually moves together, so the distance to the speaker can be known by grasping the position of the microphone. Furthermore, in the case of the present invention, as shown as the effect of the first embodiment, if a non-correlated signal is emitted from a plurality of speakers, a plurality of distances can be measured simultaneously by a single microphone. The position of the person).

[Third Embodiment]
In this embodiment, a configuration example in the case of performing oversampling is shown. In order to perform oversampling, the impulse response calculation unit 140 of the distance measurement device 100 (FIG. 3) or the distance measurement device 200 (FIG. 7) may be replaced with an impulse response calculation unit 140 ′ shown in FIG. The impulse response calculation unit 140 ′ is different from the impulse response calculation unit 140 (FIG. 6) in that an oversampling unit 146 is provided between the multiplication unit 144 and the inverse frequency domain transform unit 145. Other components are the same as those of the distance measuring device 100 and the distance measuring device 200. The oversampling unit 146 adds 0 to the signal output from the multiplication unit 144 for the frequency to be oversampled. For example, when performing N times oversampling, assuming that the frequency half the sampling frequency of the signal output from the multiplier 144 is F, a frequency region greater than F and less than or equal to NF is added, and all of the values are set to 0. And output. When the inverse frequency domain transforming means 145 transforms this signal into the time domain, an impulse response with an increased sampling frequency is obtained. Such processing increases the distance resolution and enables more accurate distance measurement.

[Fourth Embodiment]
In this embodiment, a configuration example in the case of performing downsampling is shown. FIG. 10 shows an example of the functional configuration of the distance measuring apparatus according to this embodiment. The distance measuring apparatus 300 includes a generation signal downsampling unit 180 between the generation signal audible sound removal filter unit 120 and the impulse response calculation unit 140, and a microphone signal audible sound removal filter unit 130 and an impulse response calculation unit 140. Is different from the distance measuring device 100 (FIG. 3) or the distance measuring device 200 (FIG. 7). The generation signal downsampling unit 180 extracts one sample from the output signal of the generation signal audible sound removal filter unit 120 every M samples and outputs the sample. The microphone signal downsampling unit 190 extracts and outputs one sample every M samples from the output signal of the microphone signal audible sound removal filter unit 130. The period M can be obtained by the ratio of the total bandwidth and the bandwidth of the ultrasonic region. For example, it can be calculated by (sampling frequency) / (bandwidth of ultrasonic region × 2). By down-sampling in this way, the number of signal samples is reduced, so that the amount of calculation of the impulse response calculation unit can be reduced.

[Experimental example]
11 and 12 show the results of an experiment using the distance measuring device 100 (FIG. 3). As the speaker, a general speaker having a diameter of about 5 cm and a depth (difference between the outer peripheral portion and the central portion of the speaker) of about 1 cm is used. FIG. 11A is a diagram showing an output signal from the impulse response calculation unit 140 when the microphone is placed at a position of about 20 cm from the speaker, with the horizontal axis converted into a distance. FIG. 11B is a diagram showing an output signal from the impulse response calculation unit 140 when the microphone is placed at a position of about 5 m from the speaker, with the horizontal axis converted into a distance. From these figures, it can be seen that the distance between the speaker and the microphone can be measured.

  FIG. 12 shows the average and variance of measurement errors as a result of 10 measurements at each measurement point while changing the distance between the speaker and the microphone. The horizontal axis indicates the distance between the speaker and the microphone at the measurement point, and the vertical axis indicates the error. The point at each measurement point indicates the average value of the error, and the bar indicates the standard deviation of the error. It can be seen that both the average error and the standard deviation of the error are about 5 mm, which is sufficiently smaller than the diameter of the speaker (about 5 cm). Therefore, it can be seen that the measurement can be performed with sufficiently high accuracy.

  FIG. 13 shows a functional configuration example of a computer. Note that the distance measuring apparatus of the present invention causes the recording unit 2020 of the computer 2000 to read a program for operating the computer 2000 as each component of the present invention and operate the control unit 2010, the input unit 2030, the output unit 2040, and the like. Therefore, it can be executed by a computer. In addition, as a method of causing the computer to read, the program is recorded on a computer-readable recording medium, and the program recorded on the server or the like is read into the computer through a telecommunication line or the like. There is a method to make it.

The figure which shows the structural example of the conventional distance measuring device. The figure which shows the mode of the signal in each structure part of the conventional distance measuring device. The figure which shows the function structural example of the distance measuring device of 1st Embodiment. The figure which shows the processing flow of the distance measuring device of 1st Embodiment. The figure which shows the mode of the signal in each structure part of the distance measuring device of 1st Embodiment. The figure which shows the function structural example of an impulse response calculation part. The figure which shows the function structural example of the distance measuring device of 2nd Embodiment. The figure which shows the processing flow of the distance measuring device of 2nd Embodiment. The figure which shows the function structural example of the impulse response calculation part of 3rd Embodiment. The figure which shows the function structural example of the distance measuring device of 4th Embodiment. The figure which converted the horizontal axis into the distance, and showed the output signal from the impulse response calculation part when a microphone was put in the predetermined position from the speaker. The figure which shows the average and dispersion | variation of a measurement error as a result of having measured 10 times for every measurement point, changing the distance of a speaker and a microphone. The figure which shows the function structural example of a computer.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Speaker 20 Microphone 100 Distance measuring device 110 Signal generation part 120 Generated signal audible sound removal filter part 130 Microphone signal audible sound removal filter part 140 Impulse response calculation part 141 Generation | occurrence | production signal frequency domain conversion means 142 Microphone signal frequency domain conversion means 143 Conjugation means 144 Multiplying means 145 Inverse frequency domain converting means 146 Oversampling means 150 Peak detecting unit 160 Audible sound mixing unit 170 Audible sound passing filter unit 180 Generated signal downsampling unit 190 Microphone signal downsampling unit 200 Distance measuring device 300 Distance measuring device

Claims (10)

A distance measuring device for measuring a distance using a speaker and a microphone,
A signal generator for generating a signal including a band of 20 kHz or more;
An audible sound component that removes an audible sound component from the signal generated by the signal generation unit and outputs a signal to be supplied to the speaker; and
A microphone signal audible sound removal filter unit that removes an audible sound component from the signal from the microphone;
An impulse response calculation unit for obtaining an impulse response from the output signal of the generated signal audible sound removal filter unit and the output signal of the microphone signal audible sound removal filter unit;
A distance measuring device comprising: a peak detecting unit that detects a peak from the output of the impulse response calculating unit, obtains a time from when the signal is output from the generated signal audible sound removing filter unit to the peak, and obtains distance information. The distance measuring device according to claim 1,
Arranged between the generated signal audible sound removal filter unit and the speaker, adds an input audible sound signal to the output from the generated signal audible sound removal filter unit, and outputs a signal to be supplied to the speaker A distance measuring device comprising an audible sound mixing unit. The distance measuring device according to claim 1 or 2,
An audible sound passing filter unit that extracts only an audible sound component from a signal from the microphone is also provided. The distance measuring device according to any one of claims 1 to 3,
The impulse response calculator is
Generated signal frequency domain conversion means for converting the output signal of the generated signal audible sound removal filter unit into the frequency domain;
Microphone signal frequency domain conversion means for converting the output signal of the microphone signal audible sound removal filter unit into a frequency domain;
Conjugate means for obtaining a conjugate of either the output of the generated signal frequency domain transforming means or the output of the microphone signal frequency domain transforming means;
Find the product of the conjugate of the output of the generated signal frequency domain transforming means and the output of the microphone signal frequency domain transforming means, or the product of the conjugate of the output of the generated signal frequency domain transforming means and the output of the microphone signal frequency domain transforming means Multiplication means;
A distance measuring apparatus comprising: an inverse frequency domain converting unit that converts an output of the multiplying unit into a time domain. The distance measuring device according to claim 4,
The impulse response calculator is
An oversampling unit disposed between the multiplying unit and the inverse frequency domain transforming unit and adding 0 to the output from the multiplying unit to oversample;
The inverse frequency domain transforming unit transforms the output of the oversampling unit into a time domain. The distance measuring device according to any one of claims 1 to 4,
A generated signal downsampling unit that is arranged between the generated signal audible sound removing filter unit and the impulse response calculating unit and extracts and outputs one sample every M samples from the output signal of the generated signal audible sound removing filter unit When,
A microphone signal downsampling unit that is arranged between the microphone signal audible sound removal filter unit and the impulse response calculation unit and extracts and outputs one sample every M samples from the output signal of the microphone signal audible sound removal filter unit With
The impulse response calculation unit obtains an impulse response from the output signal of the generation signal downsampling unit and the output signal of the microphone signal downsampling unit. A distance measuring method for measuring a distance using a speaker and a microphone,
A signal generating step for generating a signal including a band of 20 kHz or more;
An audible sound removal filter step of removing an audible sound component from the signal generated in the signal generating step and outputting a signal to be supplied to the speaker;
A microphone signal audible sound removal filter step for removing an audible sound component from the signal from the microphone;
An impulse response calculation step for obtaining an impulse response from the output signal of the generated signal audible sound removal filter step and the output signal of the microphone signal audible sound removal filter step;
A distance measuring method comprising: a peak detecting step of detecting a peak from an output of the impulse response calculating step, obtaining a time from the output of the signal of the generated signal audible sound removing filter step to the peak, and obtaining distance information. The distance measuring method according to claim 7,
An audible sound mixing step of adding an input audible sound signal to the output from the generated signal audible sound removal filter step and outputting a signal to be supplied to the speaker;
An audible sound passing filter step for extracting only an audible sound component from the signal from the microphone is also provided.   A distance measurement program for operating a computer as the distance measurement device according to claim 1.   A computer-readable recording medium on which the distance measurement program according to claim 9 is recorded.

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