Shape measuring device and shape measuring method

Abstract

To provide a shape measurement apparatus and a shape measurement method which can measure the shape of an object with the high resolution with a simpler configuration than before.SOLUTION: A shape measurement apparatus 1 generates an azimuth signal for each azimuth angle θ of an arrival direction of a microwave from an object 10 to a reception antenna 5 on the basis of a plurality of mixed signals, performs Hilbert transformation of each of the plurality of obtained azimuth signals and generates a complex signal for each azimuth angle θ. The shape measurement apparatus 1 calculates a distance phase φ(t) corresponding to a distance D to the object 10 for each azimuth angle θ on the basis of the plurality of complex signals generated for each azimuth angle θ, calculates the distance D to the object 10 for each azimuth angle θ on the basis of the plurality of obtained distance phases φ(t), and measures the shape of the object 10 on the basis of the relation between the azimuth angle θ and the distance D.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a shape measuring apparatus and a shape measuring method.

Background Art

[0002] Microwaves have the characteristic of being excellent in permeability to particles such as dust and mist, and are used for distance measurement and the like in the iron-making process, which is a high-temperature dust environment. However, it has also been studied to measure the shape of an object by using the measurement results of the distance and direction to the object. As distance measurement methods using microwaves, methods using FMCW (Frequency Modulated Continuous Wave) and pulses are known. However, in these methods, the distance resolution is limited by the frequency bandwidth.

[0003] For example, when the frequency bandwidth is 1 GHz, the distance resolution is 150 mm. In order to achieve a high distance resolution of less than mm, it is necessary to use a very wide frequency bandwidth. However, when using microwaves having a wide frequency bandwidth, problems such as interference with devices using other radio waves may occur, so it is difficult to realize.

[0004] Therefore, as shown in Patent Documents 1 and 2, a method of obtaining the displacement (distance to the object) of the object from the change in the phase difference (hereinafter also referred to as distance phase) generated between the transmission signal and the reception signal from the object has been considered. In Patent Documents 1 and 2, it is proposed to use a 6-port circuit having two input ports and four output ports to observe the reception signal from the object as a complex signal, and to simultaneously obtain the amplitude and phase from the complex signal to measure the distance phase.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

[0006] However, as shown in Patent Documents 1 and 2, when using one 6-port circuit for one receiving antenna, four channels in the AD conversion circuit are required for each receiving antenna, corresponding to the four output ports of the 6-port circuit. Therefore, when attempting to measure the shape of an object using multiple receiving antennas, the number of channels in the AD conversion circuit becomes four times the number of receiving antennas, resulting in a problem of increased hardware complexity.

[0007] Therefore, the present invention has been made in view of the above-mentioned problems, and aims to provide a shape measuring device and a shape measuring method that can measure the shape of an object with high resolution using a simpler configuration than conventional methods. [Means for solving the problem]

[0008] The present invention provides a shape measuring device for measuring the shape of an object using microwaves, comprising: an antenna array provided with a transmitting antenna that transmits microwaves toward the object while changing the frequency, and a plurality of receiving antennas that receive microwaves reflected by the object; a plurality of mixers that generate a mixed signal for each receiving antenna by multiplying the transmitted microwave signal transmitted from the transmitting antenna and the received microwave signal received by the receiving antenna; and a calculation processing unit that measures the shape of the object based on the mixed signal, wherein the calculation processing unit generates an azimuth signal for each azimuth angle of the direction of arrival of the microwaves from the object to the receiving antenna based on the mixed signal, performs a Hilbert transform on the azimuth signal to generate a complex signal for each azimuth angle, calculates a distance phase corresponding to the distance to the object for each azimuth angle based on the complex signal, calculates the distance to the object for each azimuth angle based on the distance phase, and measures the shape of the object based on the relationship between the azimuth angle and the distance.

[0009] The present invention provides a shape measurement method for measuring the shape of an object using microwaves, comprising: a transmission step of transmitting and receiving microwaves using an antenna array provided with a transmitting antenna that transmits microwaves toward the object while changing the frequency, and a plurality of receiving antennas that receive microwaves reflected by the object; a mixed signal generation step of generating a mixed signal for each receiving antenna by a mixer by multiplying the transmitted microwave signal transmitted from the transmitting antenna and the received microwave signal received by the receiving antenna; and a calculation processing step of measuring the shape of the object based on the mixed signal by a calculation processing unit, wherein the calculation processing step generates an azimuth signal for each azimuth angle of the direction of arrival of the microwaves from the object to the receiving antenna based on the mixed signal, performs a Hilbert transform on the azimuth signal to generate a complex signal for each azimuth angle, calculates a distance phase corresponding to the distance to the object for each azimuth angle based on the complex signal, calculates the distance to the object for each azimuth angle based on the distance phase, and measures the shape of the object based on the relationship between the azimuth angle and the distance. [Effects of the Invention]

[0010] According to the present invention, distance can be accurately measured for each azimuth angle by calculation processing without using a 6-port circuit. Therefore, the number of output ports is reduced compared to a conventional configuration using a 6-port circuit, resulting in a simpler configuration and enabling measurement of the shape of the object with high resolution. [Brief explanation of the drawing]

[0011] [Figure 1] This is a schematic diagram showing the configuration of the shape measuring device according to this embodiment. [Figure 2] This is a block diagram showing the circuit configuration of the arithmetic processing unit. [Figure 3]3A is a graph showing the mixed signal obtained for each receiving antenna, 3B is a graph showing the azimuth signal obtained for each azimuth angle, 3C is a graph showing the real part of the complex signal obtained for each azimuth angle, and 3D is a graph showing the imaginary part of the complex signal obtained for each azimuth angle. [Figure 4] 4A is a graph showing distance-phase data obtained for each azimuth angle, 4B is a graph showing the results of performing phase unwrapping and tilt calculation processing on the distance-phase data, and 4C is a graph showing the relationship between azimuth angle and distance. [Figure 5] This is a flowchart showing the shape measurement processing procedure. [Figure 6] This is a schematic diagram showing the placement of the antenna array relative to the target object during the verification test. [Figure 7] 7A is a graph showing the shape measurement results of Comparative Example 1 obtained from the verification test, and 7B is a graph showing the shape measurement results of Example 1 obtained from the verification test. [Modes for carrying out the invention]

[0012] (1) <Configuration of the shape measuring device according to this embodiment> Figure 1 is a schematic diagram showing the configuration of the shape measuring device 1 according to this embodiment. The shape measuring device 1 measures the shape of an object 10 using microwaves, and comprises an oscillator 2, an antenna array 3 consisting of a transmitting antenna 4 and a plurality of receiving antennas 5a, 5b, 5c, ..., 5n, a plurality of mixers 6a, 6b, 6c, ..., 6n provided for each receiving antenna 5a, 5b, 5c, ..., 5n, an arithmetic processing unit 11, a storage unit 12, and a display unit 13. The shape measuring device 1 measures the distance D from the antenna array 3 to the object 10 for each azimuth angle θ, and measures the shape of the object 10 from the relationship between these distances D and azimuth angles θ. The receiving antennas 5a, 5b, 5c, ..., 5n and the mixers 6a, 6b, 6c, ..., 6n will be described simply as receiving antenna 5 and mixer 6 unless there is a need to distinguish between them.

[0013] In this embodiment, for example, a case where the raw material layer such as iron ore in a sintering machine is taken as the object 10 and the surface shape of the raw material layer is measured by the shape measuring device 1 will be described below as an example. However, the present invention is not limited to this, and as the object, for example, raw material surfaces such as coke and iron ore in a blast furnace, bath surfaces such as slag and molten steel in a converter, rail tracks, sections, and various other objects can be used. Further, in the shape measuring device 1 of the present embodiment, when measuring the distance D, the reference position O serving as a reference is set on the receiving surface that receives the microwave of the antenna array 3, and the case of measuring the distance D from the antenna array 3 (specifically, the receiving antenna 5) to the object 10 will be described below.

[0014] The antenna array 3 according to the present embodiment is a transceiver antenna provided with a transmitting antenna 4 that transmits microwaves while changing the frequency toward the object 10 and a plurality of receiving antennas 5a, 5b, 5c,..., 5n that receive the microwaves reflected by the object 10. Here, an example is shown in which the transmitting antenna 4 and the plurality of receiving antennas 5a, 5b, 5c,..., 5n are arranged in a row as the antenna array 3. These transmitting antenna 4 and receiving antennas 5 are made of, for example, conical horn antennas or flat patch antennas, and the tip surfaces with the enlarged diameters of the transmitting antenna 4 and the receiving antennas 5 are arranged along a plane. In this case, the tip surface of the receiving antenna 5 becomes the receiving surface for receiving the microwaves from the object 10.

[0015] The shape measuring device 1 sends the transmission signal sent from the oscillator 2 to the transmitting antenna 4, and irradiates microwaves from the transmitting antenna 4 toward the object 10 while changing the frequency. Further, the shape measuring device 1 also sends the transmission signal sent from the oscillator 2 to the mixers 6a, 6b, 6c,..., 6n. The frequency modulation width of the microwaves (hereinafter also referred to as transmission waves) irradiated to the object 10 and the sweep period of the microwaves are set in advance to predetermined values. The frequency of the microwaves irradiated from the transmitting antenna 4 toward the object 10 changes continuously and linearly with the passage of time.

[0016] When the shape measurement device 1 receives microwaves (hereinafter also referred to as received waves) from the object 10 with a plurality of receiving antennas 5a, 5b, 5c, …, 5n, each received wave is sent as a received signal to the corresponding mixers 6a, 6b, 6c, …, 6n. The mixers 6a, 6b, 6c, …, 6n generate a mixed signal obtained by multiplying and mixing the transmission signal of the transmitted wave and the received signal of the received wave for each of the receiving antennas 5a, 5b, 5c, …, 5n, and send the plurality of obtained mixed signals to the arithmetic processing unit 11.

[0017] Here, the reflected microwaves (received waves) reflected by the object 10 and received by the respective receiving antennas 5a, 5b, 5c, …, 5n will produce a delay Δt [seconds] proportional to the distance D from the receiving antennas 5a, 5b, 5c, …, 5n to the object 10. As a result, a frequency difference Δf [Hz] corresponding to the distance D will occur between the transmitted wave and the received wave at a certain moment. When such a transmitted wave and received wave are mixed by the mixers 6a, 6b, 6c, …, 6n, it becomes a difference frequency signal (mixed signal) of a sine wave having a frequency component corresponding to Δf.

[0018] The arithmetic processing unit 11 measures the shape of the object 10 based on the mixed signal. The arithmetic processing unit 11 appropriately reads out and expands a shape measurement processing program and the like previously stored in the storage unit 12, executes the shape measurement processing described later according to the shape measurement processing program, and calculates the distance D from the reference position O to the object 10 for each azimuth angle θ based on the plurality of mixed signals generated for each of the receiving antennas 5a, 5b, 5c, …, 5n. Then, the arithmetic processing unit 11 measures the shape of the object 10 based on the relationship between the obtained distance D and azimuth angle θ.

[0019] The memory unit 12 stores mixed signals generated for each receiving antenna 5a, 5b, 5c, ..., 5n, various calculation results obtained by the arithmetic processing unit 11, and various programs. The arithmetic processing unit 11 can read the various calculation results stored in the memory unit 12 as needed and use them for new calculation processing. The display unit 13 displays various calculation results from the arithmetic processing unit 11, the distance D and azimuth angle to the object 10, and the shape measurement results of the object 10, presenting various information to the operator.

[0020] (2) <Measurement principle of distance D according to this embodiment> In this embodiment, as described above, the shape measuring device 1 can measure the distance D to the object 10 for each azimuth angle θ. First, the principle of measuring the distance D will be explained below.

[0021] In this embodiment, as shown in Figure 1, the phase difference Δφ between adjacent receiving antennas 5a, 5b, 5c, ..., 5n θ Based on this, the azimuth angle θ of the direction of arrival of microwaves from the object 10 is determined. The AD conversion unit (described later) in the arithmetic processing unit 11 is provided with a number of channels corresponding to these multiple receiving antennas 5a, 5b, 5c, ..., 5n.

[0022] Generally, in such cases, the calculation of the imaginary component Q of the complex signal corresponding to the microwave received signal (hereinafter simply referred to as the imaginary part or Q component) is omitted to reduce the number of channels in the AD converter, and therefore, distance phase cannot be obtained. In this embodiment, a Hilbert transform is performed on the mixed signal obtained for each receiving antenna 5a, 5b, 5c, ..., 5n, and a signal with a phase delay of 90° is created by signal processing, and this is taken as the imaginary component Q.

[0023] Here, if the mixed signal is the real signal x(t), the imaginary component Q(t) can be found by equation (1) below. Note that the asterisk (*) below indicates convolution.

[0024]

number

[0025] In practical terms, to reduce computational complexity, the complex signal z(t) is obtained as an analytical signal using the Fourier transform and inverse Fourier transform. If X(f) is the Fourier transform of the real signal x(t) and Z(f) is the Fourier transform of the complex signal z(t), then it can be expressed as shown in equation (2) below, where f is the frequency [Hz] of the transmitted signal (microwave).

[0026]

number

[0027] From the above, the real signal x(t) is Fourier transformed, and based on the resulting Fourier transform X(f) of the real signal, the Fourier transform Z(f) of the analytical signal is obtained from equation (2) above. By performing the inverse Fourier transform of the Fourier transform Z(f) of the analytical signal, the complex signal z(t) shown in equation (3) below can be obtained as the analytical signal.

[0028] z(t) = I(t) + jQ(t) …(3)

[0029] Note that j represents the imaginary unit. Furthermore, based on equation (3) above, the distance phase φ(t) can be obtained from equation (4) below.

[0030]

number

[0031] In this way, by performing the Fourier transform and inverse Fourier transform described above while changing the frequency of the microwaves transmitted toward the object 10, a complex signal z(t) can be obtained, and the frequency-dependent distance phase φ(t) can be calculated without using a conventional 6-port circuit.

[0032] In Patent Document 2, it is proposed that, because the phase delay amount given in the 6-port circuit changes with frequency, a method is proposed to eliminate the uncertainty of the distance phase by using frequency sweep and expand the dynamic range of displacement measurement. However, in order to eliminate the uncertainty of the distance phase by using frequency sweep, a calibration procedure is required in which the phase delay amount for each frequency given in the 6-port circuit is measured (calibrated) in advance.

[0033] In contrast, this embodiment has the advantage that it does not require a phase delay to be applied circuit-wise, and the amount of phase delay does not change with frequency, thus eliminating the need for prior calibration work as shown in Patent Document 2.

[0034] However, since the Fourier transform of the real signal x(t) distorts both ends of the signal waveform and reduces the effective frequency bandwidth, it is desirable to widen the frequency sweep width, for example, to 1 GHz or more.

[0035] (3) Shape measurement processing in the calculation processing unit Next, we will explain the shape measurement process for measuring the shape of the object 10 using the distance measurement principle described above. Figure 2 is a block diagram showing the circuit configuration of the arithmetic processing unit 11 that performs the shape measurement process. The arithmetic processing unit 11 is configured as a computer device having a CPU (Central Processing Unit), RAM (Random Access Memory), ROM (Read Only Memory), etc., and includes an AD conversion unit 19, an arrival direction estimation unit 21, a Hilbert conversion unit 22, a phase calculation unit 23, a phase unwrapping processing unit 24, a slope calculation unit 25, a rough distance calculation unit 26, a phase uncertainty resolution unit 27, and a shape measurement unit 28.

[0036] Here, Figure 3A is a graph showing an example of the waveform of the mixed signal generated by mixers 6a, 6b, 6c, ..., 6n for each receiving antenna 5a, 5b, 5c, ..., 5n. The receiving antennas 5a, 5b, 5c, ..., 5n are shown on the horizontal axis, and time (∝ frequency) is shown on the vertical axis. The horizontal axis also shows the signal strength of the mixed signal for each receiving antenna 5a, 5b, 5c, ..., 5n. For example, "1", which represents the first receiving antenna 5a, shows a waveform in which the mixed signal oscillates sinusoidally.

[0037] When the arithmetic processing unit 11 receives mixed signals from each mixer 6a, 6b, 6c, ..., 6n, it performs analog-to-digital conversion on each mixed signal in the AD conversion unit 19 and sends the converted mixed signal to the direction of arrival estimation unit 21.

[0038] Here, as shown in Figure 1, if the direction of arrival of the received wave from the object 10 to the receiving antenna 5 is defined with respect to the surface normal y of the tip surface of the receiving antenna 5 that receives the received wave, then for example, there is a phase difference Δφ between adjacent receiving antennas 5a and 5b. θ Therefore, the azimuth angle θ of the direction of arrival of the received wave to each receiving antenna 5a, 5b, 5c, ..., 5n is the phase difference Δφ between adjacent receiving antennas 5a, 5b, 5c, ..., 5n. θ Each can be defined accordingly.

[0039] In this case, the direction of arrival estimation unit 21 determines, for example, the phase difference Δφ for each azimuth angle θ tilted at predetermined intervals (e.g., 1° intervals) within an angular range of ±90° with respect to the surface normal y of the receiving antenna 5. θ This is predetermined.

[0040] The direction of arrival estimation unit 21 receives the mixed signal obtained from each receiving antenna 5a, 5b, 5c, ..., 5n from the AD conversion unit 19, and for each of these mixed signals, it calculates a phase difference Δφ corresponding to each azimuth angle θ of the direction of arrival of the received wave at receiving antennas 5a, 5b, 5c, ..., 5n. θGiven these parameters, for each receiving antenna 5a, 5b, 5c, ..., 5n, individual azimuth signals are generated from the mixed signal for each azimuth angle θ at intervals of, for example, 1°, within an angular range of ±90° with respect to the surface normal y.

[0041] The direction of arrival estimation unit 21 then takes the individual direction signals obtained for each azimuth angle θ from each receiving antenna 5a, 5b, 5c, ..., 5n, and adds up the individual direction signals at the same time along the time axis for each azimuth angle θ, generating a direction signal for each azimuth angle θ as shown in 3B of Figure 3. Once the direction of arrival estimation unit 21 has generated a direction signal for each azimuth angle θ of the direction of arrival, it sends these direction signals to the Hilbert transform unit 22.

[0042] Figure 3B is a graph showing an example of the waveform of an azimuth signal generated at azimuth angles θ in 1° increments within an angular range of ±90° relative to the surface normal y of the receiving antenna 5. The horizontal axis shows the azimuth angle θ of the direction of arrival, and the vertical axis shows time (∝ frequency). The horizontal axis also shows the signal strength of the azimuth signal for each azimuth angle θ. For example, the azimuth signal at an azimuth angle of -90° has a sinusoidal oscillating waveform.

[0043] The Hilbert transform unit 22 takes each azimuth signal as a real signal x(t) and performs a Hilbert transform on each azimuth signal in the time axis direction, generating a complex signal z(t) as an analysis signal for each azimuth angle θ, which consists of a real component I and an imaginary component Q that is 90° out of phase from the real component I, as shown in equation (3) above. The Hilbert transform unit 22 sends the complex signal z(t) generated for each azimuth angle θ to the phase calculation unit 23.

[0044] Here, Figure 3C is a graph showing the signal waveform of the real component I (indicated as "real part (component I)") of the complex signal z(t), and Figure 3D is a graph showing the signal waveform of the imaginary component Q (indicated as "imaginary part (component Q)") of the complex signal z(t). In Figures 3C and 3D, the azimuth angle θ of the direction of arrival is shown on the horizontal axis, and time (∝ frequency) is shown on the vertical axis. The horizontal axis also shows the signal intensity for each azimuth angle θ; for example, the signal with an azimuth angle θ of -90° has a sinusoidal oscillating waveform.

[0045] Furthermore, in order to reduce the computational complexity, it is desirable for the Hilbert transform unit 22 to generate a complex signal z(t) by performing a Fourier transform and an inverse Fourier transform on each azimuth signal, which is a real signal x(t). In this case, the Hilbert transform unit 22 performs a Fourier transform on each azimuth signal, obtains the Fourier transform Z(f) of the analyzed signal from equation (2) above using the obtained calculation results, and then performs an inverse Fourier transform on each to obtain a complex signal z(t) as shown in equation (3) above.

[0046] The phase calculation unit 23 calculates the distance phase φ(t) for each azimuth angle θ from a plurality of complex signals z(t) obtained for each azimuth angle θ, according to equation (4) above. Here, 4A in Figure 4 is a graph showing an example of the waveform of the distance phase φ(t) obtained for each azimuth angle θ, with the azimuth angle θ of the direction of arrival shown on the horizontal axis and time (∝ frequency) shown on the vertical axis. The horizontal axis also shows the amount of phase change of the distance phase φ(t) for each azimuth angle θ, for example, the distance phase φ(t) for an azimuth angle θ of -90° has a sawtooth waveform.

[0047] The phase calculation unit 23 calculates the distance phase φ(t) for each azimuth angle θ and sends the distance phase φ(t) as distance phase data for each azimuth angle θ to the phase unwrapping processing unit 24. The phase calculation unit 23 also sends the distance phase data obtained for each azimuth angle θ to the phase uncertainty resolution unit 27 in order for the phase uncertainty resolution unit 27 to calculate an integer n (described later) that removes the uncertainty of 2π.

[0048] The phase unwrapping processing unit 24 performs phase unwrapping on the distance phase data obtained for each azimuth angle θ, and as shown in 4B of Figure 4, it connects the discontinuities in the distance phase φ(t) along the frequency f for each azimuth angle θ, thereby generating phase unwrapping data that continuously represents the distance phase φ(t).

[0049] For example, the phase unwrapping data at -90° shown in 4B of Figure 4 represents the phase unwrapping data obtained by continuously connecting the positively increasing signals from the sawtooth-shaped signal at -90° shown in 4A of Figure 4, thereby representing the distance phase φ(t) continuously.

[0050] The phase unwrapping processing unit 24 sends multiple phase unwrapping data obtained for each azimuth angle θ to the slope calculation unit 25. The slope calculation unit 25 calculates an approximate straight line for each azimuth angle θ from the phase unwrapping data which continuously represents the distance phase φ(t) along frequency f, and calculates the slope dφ(t) / df of this approximate straight line. Once the slope dφ(t) / df of the distance phase φ(t) with respect to frequency f is calculated for each azimuth angle θ, the slope calculation unit 25 sends these to the rough distance calculation unit 26.

[0051] Here, the relationship between the distance D [m] from the receiving antenna 5 to the object 10 and the distance phase φ(t) [rad] can be expressed by the following equation (5).

number

[0052] Therefore, the distance D can be expressed by the following equation (6).

number

[0053] However, if the distance D to the object 10 changes by more than half the wavelength, an indetermination of 2π occurs in the phase characteristics, where it is impossible to distinguish between the distance phase φ(t) and the distance phase (φ(t) + 2πn) (where n is an integer). For this reason, the actual distance D is given by equation (7) below.

number

[0054] Therefore, when measuring a distance D where the distance phase φ(t) exceeds 2π, it is necessary to uniquely determine the integer n.

[0055] In equation (7) above, we multiply both sides by f, which represents the frequency, and then differentiate both sides with respect to f. At this point, only the distance phase φ(t) depends on the frequency f, so we obtain equation (8) below.

number

[0056] Therefore, by sweeping the frequency f and finding the slope dφ(t) / df of the distance phase φ(t) with respect to frequency f, we can determine the distance without uncertainty of 2π (hereinafter referred to as the rough distance D') from equation (8). Then, after finding the rough distance D' from equation (8) above, we use this rough distance D', the frequency f, and the distance phase φ(t) to determine the integer n from equation (7) above.

[0057] Furthermore, by measuring the distance phase φ(t) itself at the center frequency (the center frequency f of the sweep frequency range; for example, if the sweep frequency range is 38-42 [GHz], the center frequency is 40 [GHz]), and substituting it into the above equation (7) where an integer n has been determined, the distance D below the wavelength can be determined. In this way, it is possible to eliminate the uncertainty of 2π and measure the distance phase φ(t) at the same time, enabling the measurement of the distance D with a dynamic range greater than the wavelength and high resolution below the wavelength.

[0058] In order to perform the above calculation process for each azimuth angle θ, the rough distance calculation unit 26 uses the slope dφ(t) / df of the distance phase φ(t) for each azimuth angle θ obtained during frequency sweep to calculate the rough distance D' for each azimuth angle θ from equation (8) above (here, it is calculated from the equation obtained by replacing D with D' in equation (8)), and sends the obtained calculation results to the phase uncertainty resolution unit 27.

[0059] The phase uncertainty resolution unit 27, based on the distance phase data received from the phase calculation unit 23, which shows the distance phase φ(t) at each frequency f calculated for each azimuth angle θ, first determines the distance phase φ(t) at the center frequency of the sweep frequency range for each azimuth angle θ, and then calculates the absolute value of these distance phases φ(t). Then, using these center frequencies, the absolute value of the distance phases φ(t), and the rough distance D', the phase uncertainty resolution unit 27 calculates an integer n for each azimuth angle θ from the above equation (7) to remove the uncertainty of 2π.

[0060] The phase uncertainty elimination unit 27 sends information of integer n calculated for each azimuth angle θ to the shape measurement unit 28. The shape measurement unit 28 uses each integer n received from the phase uncertainty elimination unit 27 to define the integer n in equation (7) above for each azimuth angle θ, thereby eliminating the uncertainty of 2π. The shape measurement unit 28 also obtains the distance phase φ(t) at the center frequency of the sweep frequency range for each azimuth angle θ from the distance phase data for each azimuth angle θ received from the phase calculation unit 23, and then calculates the absolute value of these distance phases φ(t).

[0061] The shape measuring unit 28 uses each absolute value obtained for each azimuth angle θ as the distance phase φ(t) of the above equation (7), which removes the uncertainty of 2π for each azimuth angle θ, and calculates the distance D for each azimuth angle θ based on the said equation (7), as shown in 4C of Figure 4.

[0062] Figure 4C is a graph showing the distance D obtained for each azimuth angle θ, with the azimuth angle θ of the direction of arrival shown on the horizontal axis and the distance D on the vertical axis. In this case, the shape measuring unit 28 calculates the distance D at each azimuth angle θ at 1° intervals within an angular range from -90° to +90°, for example.

[0063] In this way, the shape measuring device 1 can obtain data showing the relationship between the azimuth angle θ and the distance D calculated for each azimuth angle θ, and the shape of the object 10 can be measured from these relationships between the azimuth angle θ and the distance D at each azimuth angle θ.

[0064] For example, as shown in Figure 7B later, a vertical axis is taken from the receiving antenna 5 in the vertical direction, and a horizontal axis is taken horizontally along the extension lines of each azimuth angle θ from the receiving antenna 5. Then, the position that corresponds to the horizontal axis when extension lines are drawn horizontally from the receiving antenna 5 at each azimuth angle θ is defined as the horizontal position, and the shape of the object 10 can be measured by plotting the distance D for each azimuth angle θ at the horizontal position defined from the azimuth angle θ.

[0065] Furthermore, the shape measuring device 1 eliminates the uncertainty of the distance phase φ(t) by 2π, allowing the distance D to be measured for each azimuth angle θ. This expands the dynamic range during measurement and enables the measurement of the distance D for each azimuth angle θ with high resolution below the wavelength.

[0066] Next, using the flowchart in Figure 5, the time-series flow of the shape measurement process described above will be briefly explained below. The shape measuring device 1 transmits microwaves with frequency f varying over time from the transmitting antenna 4 to the object 10. The reflected microwaves from the object 10 are received by the receiving antennas 5a, 5b, 5c, ..., 5n. As a result, when the arithmetic processing unit 11 acquires the multiple mixed signals generated by the mixers 6a, 6b, 6c, ..., 6n for each receiving antenna 5a, 5b, 5c, ..., 5n, the shape measuring device 1 starts the shape measurement process and moves from the start step to step S12.

[0067] In step S12, the arithmetic processing unit 11 performs analog-to-digital conversion processing on the multiple mixed signals obtained for each receiving antenna 5a, 5b, 5c, ..., 5n using the AD conversion unit 19, and then proceeds to the next step S13.

[0068] In step S13, the arithmetic processing unit 11 performs an arrival direction estimation process using the arrival direction estimation unit 21, and for each mixed signal obtained for each receiving antenna 5a, 5b, 5c, ..., 5n, it determines the phase difference Δφ corresponding to each azimuth angle θ within a predetermined angular range in which the received wave arrives at the receiving antenna 5. θ By providing these values, individual azimuth signals are generated for each azimuth angle θ for each receiving antenna 5a, 5b, 5c, ..., 5n. Here, each azimuth angle θ is defined at 1° intervals within the angular range of -90° to +90°, and the phase difference Δφ corresponds to each azimuth angle θ. θ These signals are applied to the mixed signal, and individual azimuth signals for each azimuth angle θ are generated for each mixed signal.

[0069] Furthermore, in step S13, the direction of arrival estimation unit 21, as part of the direction of arrival estimation process, takes the individual direction signals obtained for each direction of arrival from each receiving antenna 5a, 5b, 5c, ..., 5n, and adds up the individual direction signals at the same time along the time axis for each direction of arrival θ. As shown in 3B of Figure 3, it generates a direction signal for each direction of arrival θ and then moves on to the next step S14.

[0070] In step S14, the arithmetic processing unit 11 performs a Hilbert transform on each azimuth signal using the Hilbert transform unit 22, generating a complex signal for each azimuth angle θ as shown in equation (3) above, and then proceeds to the next step S15.

[0071] In step S15, the arithmetic processing unit 11 uses the complex signal obtained for each azimuth angle θ by the phase calculation unit 23 to determine the distance phase φ(t) at the given frequency f from equation (4) above, generates distance phase data showing the relationship between frequency f and distance phase φ(t) for each azimuth angle θ, and then proceeds to step S16.

[0072] In step S16, the arithmetic processing unit 11 performs a phase unwrapping process on the distance-phase data, which shows the relationship between frequency f and distance-phase φ(t) for each azimuth angle θ, as shown in 4A of Figure 4, using the phase unwrapping processing unit 24. As shown in 4B of Figure 4, the unit generates phase unwrapping data in which the distance-phase φ(t) is continuously connected along the frequency f for each azimuth angle θ, and then proceeds to the next step S17.

[0073] In step S17, the arithmetic processing unit 11 uses the slope calculation unit 25 to calculate the slope dφ(t) / df of the distance phase φ(t) with respect to the sweeping frequency f from each phase unwrapping data, and then proceeds to the next step S18. In step S18, the arithmetic processing unit 11 uses the rough distance calculation unit 26 to calculate the rough distance D' for each azimuth angle θ from the above equation (8) using the slope dφ(t) / df calculated for each azimuth angle θ, and then proceeds to the next step S19.

[0074] In step S19, the arithmetic processing unit 11 uses the phase uncertainty resolution unit 27 to calculate an integer n for each azimuth angle θ that removes the uncertainty of 2π from equation (7) above, using the rough distance D', the center frequency in the sweep frequency range, and the absolute value of the distance phase φ(t) at the center frequency, and then proceeds to the next step S20.

[0075] In step S20, the arithmetic processing unit 11 uses the center frequency in the sweep frequency range and the absolute value of the distance phase φ(t) at the center frequency, obtained by the shape measuring unit 28, to calculate the distance D for each azimuth angle θ from the above equation (7) obtained by defining the above integer n and removing the uncertainty of 2π, and then proceeds to the next step S21.

[0076] In step S21, the arithmetic processing unit 11 outputs a shape measurement result that identifies the shape of the object 10 based on the relationship between the azimuth angle θ and the distance D obtained for each azimuth angle θ, and then terminates the shape measurement process described above.

[0077] (4) <Mechanism of Action and Effects> In the above configuration, the shape measuring device 1 transmits microwaves from the transmitting antenna 4 towards the object 10 while changing the frequency, and receives the microwaves reflected by the object 10 with multiple receiving antennas 5. The shape measuring device 1 generates a mixed signal for each receiving antenna 5 by a mixer 6, which is obtained by multiplying the transmitted microwave signal from the transmitting antenna 4 with the received microwave signal received by each receiving antenna 5, and the arithmetic processing unit 11 measures the shape of the object 10 based on the multiple mixed signals.

[0078] In this case, the arithmetic processing unit 11 generates an azimuth signal for each azimuth angle θ of the direction of arrival of microwaves from the object 10 to the receiving antenna 5 based on a plurality of mixed signals, and performs a Hilbert transform on each of the obtained azimuth signals to generate a complex signal for each azimuth angle θ. Furthermore, based on the plurality of complex signals generated for each azimuth angle θ, the arithmetic processing unit 11 calculates a distance phase φ(t) corresponding to the distance D to the object 10 for each azimuth angle θ, and calculates the distance D to the object 10 for each azimuth angle θ based on the obtained distance phase φ(t), and measures the shape of the object 10 based on the relationship between the azimuth angle θ and the distance D.

[0079] As a result, the shape measuring device 1 can measure the distance D for each azimuth angle θ through calculation processing without using a 6-port circuit. This reduces the number of output ports compared to a conventional configuration using a 6-port circuit, resulting in a simpler configuration and enabling measurement of the shape of the object 10 with high resolution. Furthermore, this shape measuring device 1 eliminates the need for calibration work, such as pre-measuring (calibrating) the phase delay amount for each frequency, which is required when using a 6-port circuit, thus reducing the workload on the operator.

[0080] Furthermore, the arithmetic processing unit 11 adds a phase difference Δφ corresponding to the azimuth angle θ to the mixed signal generated for each receiving antenna 5. θThe device generates individual azimuth signals for each azimuth angle θ for each receiving antenna 5, and then adds the obtained individual azimuth signals along the time axis for each azimuth angle θ to generate individual azimuth signals. As a result, the shape measuring device 1 generates azimuth signals for each azimuth angle θ from multiple individual azimuth signals obtained from multiple receiving antennas 5, and uses these azimuth signals to calculate the distance D, thereby enabling the calculation of the distance D with greater accuracy for each azimuth angle θ.

[0081] Furthermore, since the shape measuring device 1 can eliminate the uncertainty of the phase by 2π, it can accurately measure the distance D, which is larger than the wavelength, and measure the shape of the object 10 with high resolution.

[0082] (5) <Other Embodiments> It should be noted that the present invention is not limited to this embodiment, and various modifications can be made within the scope of the gist of the invention. For example, the distance D may be directly calculated from the above equation (8) for each azimuth angle θ without performing a process to remove the uncertainty of 2π.

[0083] Furthermore, in the embodiments described above, when calculating the integer n and distance D that eliminate the uncertainty of 2π from equation (7), the absolute value of the distance phase φ(t) at the center frequency was applied to φ(t) in equation (7). However, the present invention is not limited to this. For example, the integer n and distance D may be calculated from equation (7) using any frequency f within the sweep frequency range and the distance phase φ(t) at that time.

[0084] (6) <Verification Test> Next, the verification test will be described. Here, a verification test was conducted to confirm that the shape measurement method according to the present embodiment described above can obtain high-resolution measurement results. In this verification test, the surface shape of the raw material layer charged into the sintering machine was measured using Comparative Example 1 and Example 1, which will be described later.

[0085] In Comparative Example 1, the distance to the object 10 was measured using the FMCW method, a common distance measurement method. Then, the azimuth angle was determined for each distance, and the surface shape of the raw material layer loaded into the sintering machine was measured from the distance and azimuth angle. In Example 1, the surface shape of the raw material layer loaded into the sintering machine was measured using the shape measuring device 1 according to the present embodiment described above.

[0086] In the verification test, an antenna array 3 was prepared, which consisted of two transmitting antennas 4 and sixteen receiving antennas 5. As shown in Figure 6, the antenna array 3 was positioned diagonally above the raw material layer (object 10) loaded into the sintering machine. In Figure 6, the direction from the back of the page to the front of the page is the direction of transport of the raw material layer, and the left-right direction of the page is the machine width direction.

[0087] In Comparative Example 1 and Example 1, an antenna array 3 was installed to overlook the surface of the raw material layer from an oblique angle above. Microwaves were transmitted from the antenna array 3 along the width direction of the object 10 in the range of 23 to 25 GHz, and the microwaves reflected from the object 10 were received by the antenna array 3. In Figure 6, L1 indicates the microwave transmission and reception area of ​​the antenna array 3, and verification tests were conducted within a transmission and reception area of ​​±45°. Specifically, in Example 1, an azimuth signal was generated for each azimuth angle θ at 0.1° intervals within the angle range of ±45°, and a Hilbert transform was performed on the azimuth signal obtained for each azimuth angle θ.

[0088] Figure 7A shows the shape measurement results of Comparative Example 1, in which distance was measured using the FMCW method, a common distance measurement method, based on multiple received signals obtained from the antenna array 3, and then the azimuth angle was identified for each distance, and the shape of the object 10 was measured from the relationship between distance and azimuth angle.

[0089] Figure 7B shows the shape measurement results of Example 1, in which, based on multiple received signals obtained from the antenna array 3, the shape measuring device 1 generates an azimuth signal for each azimuth angle θ, then performs processes such as calculating the distance phase φ(t) using the Hilbert transform and resolving the uncertainty of 2π to determine the distance D, and the shape of the object 10 is measured from the relationship between the azimuth angle θ and the distance D.

[0090] Figures 7A and 7B show the horizontal position of the object 10 on the horizontal axis and the vertical position relative to the object 10 on the vertical axis. Furthermore, in Figures 7A and 7B, the antenna array 3 is positioned at an angle above the object 10 and has a field of view of ±45°. The shape of the object 10 is output in Cartesian coordinates based on this antenna array 3. As a result, in Figures 7A and 7B, the surface of the raw material layer, which is the object 10, is plotted with the data tilted from the upper right to the lower left, centered on the origin of the horizontal axis.

[0091] In Figures 7A and 7B, the plots in the horizontal range of -1.5 to 0.5 m represent the surface shape of the object 10 (raw material layer). From Figure 7A, it can be seen that in Comparative Example 1, which is the conventional method, the data becomes clustered and discrete as the distance from the antenna array 3 increases, resulting in a step-like structure.

[0092] On the other hand, from Figure 7B, it can be seen that in Embodiment 1 according to this embodiment, the data is plotted almost continuously even when the distance from the antenna array 3 is large, and a relatively smooth shape is observed, confirming that shape measurement can be performed with high resolution. [Explanation of Symbols]

[0093] 1 Shape measuring device 3 Antenna Array 4 Transmitting antenna 5, 5a, 5b, 5c, ..., 5n Receiving antenna 6, 6a, 6b, 6c, ..., 6n Mixer 11. Arithmetic Processing Unit

Claims

1. A shape measuring device that measures the shape of an object using microwaves, An antenna array provided with a transmitting antenna that transmits microwaves toward the object while changing the frequency, and a plurality of receiving antennas that receive microwaves reflected by the object, Multiple mixers generate a mixed signal for each receiving antenna by multiplying the microwave transmission signal transmitted from the transmitting antenna and the microwave reception signal received by the receiving antenna, A calculation processing unit that measures the shape of the object based on the mixed signal, It has, The aforementioned arithmetic processing unit is A phase difference corresponding to the azimuth angle is applied to the mixed signal, and individual azimuth signals are generated for each azimuth angle of the direction of arrival of the microwave from the object to the receiving antenna. The individual azimuth signals are added together along the time axis for each azimuth angle to generate a azimuth signal for each azimuth angle. A Hilbert transform is performed on the aforementioned multiple azimuth signals to generate a complex signal for each azimuth signal, having a real component I and an imaginary component Q that is 90° out of phase with the real component I. Based on the complex signal, the distance phase corresponding to the distance to the object is calculated for each azimuth angle. Based on the slope of the distance phase with respect to the frequency, the rough distance to the object is calculated for each azimuth angle. Using the aforementioned rough distance and distance phase, an integer n is calculated to resolve the uncertainty of the phase characteristic 2π for each azimuth angle. Using a predetermined calculation formula that eliminates the uncertainty of 2π by defining the integer n, the distance to the object is calculated for each azimuth angle using the distance phase. A shape measuring device that measures the shape of an object based on the relationship between the azimuth angle and the distance.

2. A shape measurement method that uses microwaves to measure the shape of an object, A transmitting and receiving step of transmitting and receiving microwaves using an antenna array provided with a transmitting antenna that transmits microwaves toward the object while changing the frequency, and a plurality of receiving antennas that receive microwaves reflected by the object, A mixed signal generation step in which a mixer generates a mixed signal for each receiving antenna by multiplying the microwave transmission signal transmitted from the transmitting antenna and the microwave reception signal received by the receiving antenna, A calculation processing step in which the calculation processing unit measures the shape of the object based on the mixed signal, It has, The aforementioned calculation processing step is: A phase difference corresponding to the azimuth angle is applied to the mixed signal, and individual azimuth signals are generated for each azimuth angle of the direction of arrival of the microwave from the object to the receiving antenna. The individual azimuth signals are added together along the time axis for each azimuth angle to generate a azimuth signal for each azimuth angle. A Hilbert transform is performed on the aforementioned multiple azimuth signals to generate a complex signal for each azimuth angle, having a real component I and an imaginary component Q that is 90° out of phase with the real component I. Based on the complex signal, the distance phase corresponding to the distance to the object is calculated for each azimuth angle. Based on the slope of the distance phase with respect to the frequency, the rough distance to the object is calculated for each azimuth angle. Using the aforementioned rough distance and distance phase, an integer n is calculated to resolve the uncertainty of the phase characteristic 2π for each azimuth angle. Using a predetermined calculation formula that eliminates the uncertainty of 2π by defining the integer n, the distance to the object is calculated for each azimuth angle using the distance phase. A method for measuring the shape of an object based on the relationship between the azimuth angle and the distance.

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