WO2004095058A1 - Method for measuring distance and its system - Google Patents

Abstract

A distance measuring system for measuring the shape of a human body, or the like, in which a horn antenna is elevated/lowered along the human body, a microwave of about ten and several GHz is radiated while varying the frequency, reflected wave from the human body, a traveling wave and a standing wave are detected, and a signal from which the DC component is removed is subjected to Fourier transform, thus calculating the distance to the human body. In order to measure the distance with high accuracy, the detected standing wave is fed back to the source so that the intensity thereof becomes substantially constant.

Description

 Specification

 Distance measuring method and its device

 The present invention relates to distance measurement such as measurement of a human body shape. Background art

 Patent Document 1 Japanese Patent Application Laid-Open No. 2002-357656 (EP 1365256A1) Patent Document 1 discloses a distance measurement using a high frequency. The antenna emits directional high-frequency waves and measures the strength of the standing wave composed of the reflected wave and the traveling wave while changing the high-frequency frequency. When the intensity of the obtained standing wave is Fourier-transformed with respect to the frequency, the distance to the object is obtained.

 The inventors studied applying this technique to measurement of a human body shape, particularly to measurement of a human body shape suitable for apparel. In this process, the inventor has found that when measuring the shape of the human body, the standing wave is also weak because the reflected wave is weak, and the human body has a position where the reflected wave is particularly weak. In the case of the human body, high-frequency reflection occurs because the refractive index changes at the interface between the air inside the clothes and the human body. However, this reflection is weak, and generally there is a state in which a slight reflected wave exists in the traveling wave. Next, the intensity of the reflected wave from the human body surface varies depending on the place. This is because the reflected wave is strong when the radiation direction of the high frequency is perpendicular to the human body surface, but when it is not perpendicular, most of the reflected wave does not return to the receiving antenna. Summary of the Invention

Problems the invention is trying to solve

 An object of the present invention is to make the amplitude of a standing wave almost constant so that distance measurement can be performed with high accuracy. Structure of the invention

According to the distance measuring method of the present invention, a beam-like wave is sent from an oscillation source to a measurement object, Measuring the intensity of the standing wave based on the reflection of the wave while changing the frequency of the wave, and performing a Fourier transform to determine the distance to the object to be measured. The wave energy is changed by feeding back to the oscillation source so that the intensity becomes substantially constant.

 The distance measuring device of the present invention sends a beam-like wave from an oscillation source toward a measurement object, measures the intensity of a standing wave based on the reflection of the wave while changing the frequency of the wave, and performs Fourier transform. By this means, in a device for obtaining the distance to the object to be measured, means for detecting the intensity of the standing wave, and for feeding back to the oscillation source so that the detected intensity becomes substantially constant Means are provided.

 Preferably, the object to be measured is a human body, and the wave is a microphone mouth wave having a frequency of 5 GHz to 100 GHz. For example, the oscillation source is a microwave oscillation circuit having a frequency of 5 GHz to 100 GHz, particularly preferably 10 GHz to 50 GHz, and further scans the wave along the human body in the height direction and the circumferential direction. To determine the shape of the human body.

 Also preferably, the intensity of the wave obtained by removing the DC component after picking up and detecting the wave is defined as the intensity of the standing wave.

 For example, a pickup means for picking up the wave, a detection means for detecting the picked-up wave, and a removal means for removing and outputting a DC component from an output of the detection means are provided. Is input to the feed pack means. Functions and effects of the invention

 In the present invention, a feed pack is added to the oscillation source so that the amplitude of the standing wave becomes substantially constant. Therefore, when the reflection is weak, the output of the oscillation source increases, and the distance can be measured with high accuracy. To be substantially constant means, for example, to keep the amplitude within a range of 1 Z 2 to 2 times the reference value.

When measuring the shape of the human body, the arc division function is required on the order of cm, so the wave is preferably a microphone mouth wave with a frequency of 5 to 100 GHz, and the human body generally has low reflectivity and has irregularities on the surface. The reflected waves are directed in different directions. 'For these reasons, the amplitude of the standing wave is likely to be small and the amplitude of the force is also likely to fluctuate.However, by adding a feed pack to the oscillation source to make the amplitude of the standing wave almost constant, the human body shape with high precision Can be measured. When a standing wave is picked up, a traveling wave is generally picked up in addition to the standing wave, and the amplitude of the traveling wave is often larger than that of the standing wave. If the DC component is removed from the detection signal, the traveling wave can be removed, and the distance can be measured accurately. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a front view of the human body shape measuring device according to the embodiment.

FIG. 2 is a side view of the horn antenna used in the example.

FIG. 3 is a block diagram of a signal processing system of the human body shape measuring device according to the embodiment.

FIG. 4 is a flowchart showing a tracking algorithm in the human body shape measuring method according to the embodiment.

FIG. 5 is a diagram schematically illustrating removal of a background signal from a Fourier transform signal in the embodiment.

FIG. 6 is a diagram illustrating a Fourier transform signal and a human body shape signal along the height direction when tracking is not performed.

FIG. 7 is a diagram showing a Fourier transform signal and a human body shape signal along the height direction when tracking is performed.

FIG. 8 is a diagram showing a human body shape signal in the height direction when tracking is not performed. FIG. 9 is a diagram showing a human body shape signal in the height direction when tracking is performed. Example

 1 to 9 show an example and characteristics of the embodiment, taking measurement of a human body shape as an example. However, the distance can be measured arbitrarily, and may be used, for example, to detect the distance between the vehicle ahead and the distance to an obstacle. FIG. 1 shows the external shape of the human body shape measuring device 2. Reference numeral 4 denotes a stand on which a person stands, and reference numeral 6 denotes a frame that surrounds the periphery thereof, and includes a column 8. The elevating table 9 is moved up and down along the column 8, and one or more horn antennas 10 are provided. The horn antenna 10 is a high-frequency antenna with little diffraction loss, and the type of the antenna is arbitrary.

1 2 is a high-frequency circuit that supplies a high frequency to the horn antenna 10 and picks up and detects a standing wave of the traveling wave in the horn antenna 10 and a reflected wave from the human body. After removing the components, the signal is output to the signal processing unit 14. When a plurality of horn antennas 10 are provided, it is preferable to make the high-frequency frequency different for each antenna. The signal processing unit 14 is composed of a digital signal processor の a signal processing circuit of a personal computer level. The signal processing unit 14 outputs the obtained human body shape to the monitor 16 and the like, and receives an operation from the keyboard 18.

 The structure of the horn antenna 10 is shown in FIG. 2. Reference numeral 21 denotes a waveguide, which receives a high frequency from a high-frequency oscillation circuit and radiates a high frequency from a horn 22 whose tip is expanded. A pickup 23 is inserted into the waveguide 21 and detected by a detection circuit 2 such as a GaAs Schottky diode, and a DC component is removed by a DC eliminator 25 using a capacitor or the like. Output. The DC eliminator 25 need not be provided. The pickup 23 for standing wave detection may be provided in an antenna separate from the horn antenna 10, but the high-frequency waveguide and antenna are expensive and must be installed in the horn antenna 10 for transmission. Preferably, a pickup 23 is provided.

 FIG. 3 shows the used signal processing system. The high-frequency output from the high-frequency oscillation circuit 29 is radiated toward the human body 20 via the horn antenna 10. The high frequency used is, for example, about 10 to 15 GHz, and a relatively inexpensive high frequency element for satellite communication or the like can be used.The beam diameter in a plane perpendicular to the traveling direction is, for example, about 2 cm. . A high-frequency traveling wave and a reflected wave are present in the horn antenna 10, and a standing wave is formed by these. The energy of the traveling wave is overwhelmingly large. Then, the high frequency in the horn antenna is picked up by a pickup 23, detected by a detection circuit 24 using a GaAs Schottky diode, for example, equivalent to a half wave, and a DC component is removed by a DC eliminator 25. I do. Most of the DC component is caused by traveling waves. Instead of removing the DC component with a capacitor, the signal after AD conversion may be subtracted or differentiated to remove the DC component.

The signal from the DC eliminator 25 is fed back to the amplitude detector 26, input to the ALC (automatic level control device) 27, and the difference between the amplitude and the reference value is output. The output control section 28 drives the high-frequency oscillation circuit 29 with a gain according to the difference. The output of the high-frequency oscillation circuit 29 changes, for example, in a range of about 1/3 to 3 times the reference output. As a result, the frequency of the output signal from DC eliminator 25 becomes A feed pack is applied to the output of the oscillating circuit 29. If the power of the standing wave (the output from the DC eliminator 25) is small, the power (energy) of the traveling wave is increased, and the output of the oscillating circuit 29 is fixed by the detection circuit 24. To enable detection of existing waves without being buried in noise. In other words, it is difficult to detect a standing wave with a small amplitude in the presence of a traveling wave with a large amplitude, but it becomes easier to detect when the amplitude of the standing wave is increased. When the output from the DC eliminator 25 is large, the power of the traveling wave is reduced to keep the signal intensity from the DC eliminator substantially constant, thereby preventing saturation of the detector 24 and the like.

 The high-frequency circuit 12 changes the frequency to a plurality of, for example, 256, for one measurement point, and for example, for a center frequency of 12 GHz, a frequency of 10 to 14 GHz, or 11 to 13 GHz or the like. To enable a Fourier transform with respect to frequency. Next, the ALC 27 is activated at the first frequency for one measurement point, and the output of the ALC 27 is kept constant at the same measurement point. Alternatively, the ALC 27 is operated independently for each frequency, and the used gain (the output of the ALC 27 output control unit 28) is input to the FFT 38, which will be described later, and the ratio between the AD conversion signal and the gain is Fourier. It may be converted.

 The AD converter 36 AD-converts the output signal of the DC eliminator 25, and the DC component in the AD-converted signal is meaningless because it appears at the position of the distance zero, and this is digitally converted by the DC eliminator 37. To process. For example, after level-down the AD-converted signal by a predetermined value corresponding to the DC component, Fourier transform is performed to obtain distance information.

 The FFT 38 performs a Fourier transform on the signal from which the DC component has been removed by performing an AD conversion using a fast Fourier transform or the like. This Fourier transform is a Fourier transform related to frequency. As described in Patent Document 1, the peak of the Fourier transform signal corresponds to the distance from the antenna 10 to the human body. The signal obtained by AD conversion may be processed by a differential filter or the like to remove a DC component, and may be input to the amplitude detection unit 26. Further, the signal obtained by AD conversion by the AD converter 36 may be Fourier-transformed by the FFT 38, and then the DC component may be removed by the DC eliminator 37.

The Fourier transform signal includes signals for reflection in the antenna and reflection in a background other than the human body. Therefore, the Fourier transform signal in the case where there is no human body is stored in the background signal storage unit 39, and the difference from the Fourier transform signal in the case where there is a human body is obtained in the difference unit 40. You. In this way, the effective part of the signal is extracted from the Fourier transform by removing the signal caused by the background.

 Figure 5 schematically illustrates the removal of the background signal. The solid line is the Fourier transform signal input from FFT 38, which is obtained by performing a Fourier transform after level shift corresponding to the DC component. From the Fourier transform signal, the signal of the dashed line stored as the background signal is subtracted to extract the peak of the Fourier transform signal due to the human body. Instead of subtracting the background, the approximate distance to the human body is known, so a window function that picks up only signals in this range may be used. However, the use of such a window function is a process similar to the tracking described later, and there is a limit to improving the accuracy.

 In addition, the human body is measured using, for example, a pair of cameras 30 and 31 to create a stereoscopic image of the human body, and the outline extraction unit 32 extracts the outline shape of the human body. Since the cameras 30 and 31 photographed the human body shape of the clothes, the actual human body surface should exist inside the human body shape extracted by the art line extraction unit 32. Alternatively, before measurement, a person's body weight, height, body fat percentage, etc. are measured, and a rough body shape is estimated in consideration of age, etc., and used instead of the signal of the end line extraction unit 32. Good. Further, the cameras 30 and 31 bit line extraction units 32 and the like need not be provided.

 On the other hand, the elevating table 9 is moved up and down by the elevating drive unit 34 to scan the surface shape of the human body within a predetermined height range. Further, the left / right movement drive unit 35 moves the horn antenna 10 to the left and right, for example, or shifts the position to the left and right, so that a large signal from the human body can be obtained so that scanning is started. I do. The configuration of the lifting / lowering drive unit 34 and the left / right movement drive unit 35 is optional, and the left / right movement drive unit 35 need not be provided.

 At the start of scanning, the comparison unit 41 checks whether a signal having a predetermined threshold or more is obtained, and operates the left / right movement driving unit 35 so that a signal with a predetermined threshold or more is obtained. Now, change the direction of the horn antenna 10. The tracking unit 42 measures the distance between the horn antenna and the human body at each height in the process of moving the horn antenna 10 up and down to scan the human body shape, as well as the previous measurement point or a plurality of previous points. Determine the reasonable range of the distance from the body surface expected from the measurement point, and extract signals within this range.

'I do. A reasonable range is that the continuity of the human body surface is maintained, or It means the range of irregularities on the human body surface. Fig. 4 shows the details of the processing of the comparison unit 41 and the tracking unit 42.

 At the start of the measurement in FIG. 4, the horn antenna is at the upper or lower end of the scan range, detects the maximum value of the Fourier transform signal input to the comparison unit 41, and checks whether the maximum value is greater than or equal to the threshold value. If the maximum value is small and equal to or less than the threshold value, a process such as searching for a position where a stronger signal can be obtained is performed by changing the direction of the horn antenna by the left and right motion driver 35.

 Tracking is started when the maximum value that is equal to or greater than the threshold is obtained at the upper or lower end of the scan range. When tracking is started, the distance from the human body is updated and maintained as a variable "tracking position" .For example, the position of the horn antenna is changed by 5 mm, and the measurement point is moved up and down to find the next maximum value . This maximum value is the maximum value in the output of the difference unit 40 and corresponds to the distance to the human body. The range in which the maximum value is detected is limited as a search range, and the distance from the human body at the previous measurement point is, for example, within ± 1 cm or ± 5 mm. When using not only the previous measurement point but also multiple previous measurement points, limit the search range to about ± 5 mm for points obtained by extrapolating these measurement points. Then, the maximum value of the Fourier transform signal within the search range is detected.

 The threshold value is determined for the obtained maximum value, and if the maximum value that is equal to or higher than the threshold value is obtained, the measurement is valid and the distance to the human body at the new measurement point is obtained. If the maximum value that is higher than the threshold value is not obtained, the threshold value in the next threshold value judgment is reduced by, for example, about 5 to 10%, or the range of searching for the maximum value is determined assuming that the unevenness of the human body is severe. For example, increase from soil 5 mm to ± 7 mm. The maximum value measured this time is arbitrary, but for example, assuming that a valid maximum value has not been obtained, the detected maximum value is invalidated. By repeating the above process up to the final measurement point, the shape of the human body along one scan line can be obtained.

Here, returning to FIG. 1, a plurality of horn antennas 10 are provided, and scanning is performed simultaneously along a plurality of lines while changing a high-frequency frequency or the like to prevent interference between antennas. If the number of antennas is small, the scanning is repeated by rotating the frame 6. By repeating such a scan, a three-dimensional shape of the human body surface can be obtained. Figure 6 shows an example in which tracking is not performed, and the maximum value of the Fourier transform signal during the scanning process is simply used as a distance signal to the human body. The solid line shows the Fourier transform signal. There are two peaks around 700 mm and around 90 mm, and the peak around 900 mm is large, so this is the distance signal. The human body shape signal obtained along the height direction by simply using the peak of the Fourier transform signal as a distance signal is indicated by dots. The position of the horizontal axis is changed between the Fourier transform signal and the human body shape signal. Without tracking as shown in Fig. 6, the human body shape signal jumps discontinuously.

 On the other hand, FIG. 7 shows the result when only the maximum value within a predetermined range is extracted from the distance signal at the previous measurement point for the same Fourier transform signal. The peak of the Fourier transform signal is split into two. The human body shape signal is obtained as a continuous line. FIG. 8 shows a human body shape signal when the measurement of FIG. 6 is performed for one scan line. FIG. 9 shows a human body shape signal when the measurement of FIG. 7 is performed for one scan line. When tracking is not performed, the human body shape signal fluctuates unnaturally around 800 to 900 mm in height. On the other hand, tracking can eliminate such noise.

 When tracking is not performed, unnatural results such as those shown in Figs. 6 and 8 can be obtained because reflections from the human body at points other than the measurement point at a position that is straight ahead from the horn antenna have an effect. It seems to be. Such reflections can be reduced by increasing the frequency of the high frequency and reducing the beam diameter. For example, if the frequency is doubled, the beam diameter will be about 1-2, and the signal near the distance of 900 mm in Fig. 6 should have reduced intensity. However, when the frequency is increased, high-frequency devices for consumer use cannot be used, and the circuit cost increases rapidly. By performing tracking, it is possible to measure the shape of the human body using consumer-use high-frequency elements used for satellite communication and the like.

In the embodiment, since the radiated high frequency power (energy) is increased at the measurement point where the amplitude of the standing wave is small, the standing wave is not buried in noise and cannot be detected. At the measurement point where the amplitude of the standing wave is large, the high-frequency power is reduced, so that the saturation of the detection circuit can be prevented. For this reason, a standing wave with almost constant amplitude can be generated regardless of the amplitude of the standing wave, and distance can be measured with high accuracy. In the embodiment, a high frequency such as a microwave was used. Ultrasound of about kHz to 100 kHz may be used.

Claims

The scope of the claims 1. A beam wave is sent from the oscillation source to the object to be measured, and the intensity of the standing wave based on the reflection of the wave is measured while changing the frequency of the wave, and the Fourier transform is performed to measure the intensity of the standing wave. In the method of finding the distance to  A distance measuring method, comprising detecting the intensity of the standing wave, feeding the oscillation to the oscillation source such that the intensity becomes substantially constant, and changing the energy of the wave.  2. The distance measuring method according to claim 1, wherein an object to be measured is a human body, and said wave is a microwave having a frequency of 5 GHz to: L 00 GHz.  3. The distance measuring method according to claim 1, wherein, after picking up and detecting the wave, an intensity of a component obtained by removing a DC component is set as an intensity of the standing wave.  4. A beam-like wave is sent from the oscillation source toward the object to be measured, and the intensity of the standing wave based on the reflection of the wave is measured while changing the frequency of the wave, and the Fourier transform is performed to measure the intensity of the standing wave. In a device that seeks the distance to  A means for detecting the intensity of the standing wave; and a means for feeding back the oscillation source so that the detected intensity becomes substantially constant. 5. The measurement target is a human body, the oscillation source is a microwave oscillation circuit with a frequency of 5 GHz to 100 GHz, and the waves are scanned along the human body to obtain the shape of the human body. The distance measuring device according to claim 4, characterized in that: .  6. A pickup means for picking up the wave, a detection means for detecting the picked-up wave, and a removal means for removing and outputting a DC component from the output of the detection means, and 5. The distance measuring apparatus according to claim 4, wherein an output of said means is inputted to said feedback means.