Measuring device, measurement method, and program

Abstract

To efficiently measure spectra of reflection waves generated when electromagnetic waves are applied to an object while suppressing an influence of interference.SOLUTION: An optical system 2 emits electromagnetic waves W entering from an electromagnetic wave source 1 to a sample S held by a stage 3 that can be driven along a propagation direction of the electromagnetic waves W, and emits synthetic waves obtained by interference between reflection waves Ws and stray light Wr after the reflection waves Ws from the sample S enter. A detector 4 detects intensity of synthetic waves and outputs a detection signal DET showing a detection result. A control section 6 controls the electromagnetic wave source 1 so as to switch the frequencies of the electromagnetic waves W among multiple frequencies, and controls the stage 3 such that the stage 3 travels to multiple positions for each of the multiple frequencies. A signal processing section 5 measures spectra of synthetic waves according to the detection signal DET and acquires spectra of the reflection waves Ws by removing spectra of stray light Wr that is acquired in advance from spectra of synthetic waves.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a measurement device, a measurement method, and a program. [Background technology]

[0002] The technique of irradiating an object with electromagnetic waves and measuring the reflected or transmitted electromagnetic waves is a useful means of understanding the shape, composition, and corrosion state of buried objects inside a structure, which cannot be determined from information obtained from the surface of the object. This technique is used in a wide range of fields, such as assessing the lifespan of buildings and inspecting the quality of industrial products.

[0003] For example, Non-Patent Document 1 proposes a method for measuring the internal structure of a structure by irradiating electromagnetic waves in the megahertz to gigahertz range onto a structure made of concrete, and detecting the electromagnetic waves reflected from the incident surface and the back surface opposite the incident surface, as well as the waves reflected from an iron ball embedded in the concrete.

[0004] Furthermore, in order to achieve both straightness and high resolution, the use of millimeter waves to terahertz waves has been attracting attention in recent years, and applications are beginning to emerge in fields closely related to our daily lives where safety is essential, such as distance measurement technology in autonomous driving and airport security inspections.

[0005] For example, Non-Patent Document 2 introduces a method for inspecting the presence or absence of voids in a cable by irradiating the cable with terahertz waves and detecting the electromagnetic waves that have passed through the cable. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] JH Bungey, SG Millard, “Rader inspection of structures”, Proceedings of the Institution of Civil Engineers, Structures and Buildings, Volume 99, Issue 2, MAY 1993, pp. 173-186 [Non-patent document 2] Peter H. Siegel, “Terahertz Technology”, IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 50, NO. 3, MARCH 2002, pp. 910-928 [Non-patent document 3] Yukio Kono, "Highly Sensitive Terahertz Wave Detector - Application to Near-Field Imaging -", Journal of Optics, Optical Society of Japan, Vol. 38, No. 2, pp. 81-88, 2009 Summary of the Invention [Problem to be solved by the invention]

[0007] Common electromagnetic wave technology often uses single-wavelength measurements, which can identify materials or measure distances using radar technology by selecting a frequency that matches the transmission characteristics of the target medium, but it is difficult to determine whether the identified difference is due to a difference in the material or a change in its properties.

[0008] On the other hand, technology for estimating the state of an object is being actively researched in the field of light, and in the visible light and near-infrared regions, technology has been developed to estimate the surface state of an object by measuring its spectrum.

[0009] Therefore, it is conceivable to estimate the internal structure of an object by irradiating it with electromagnetic waves in the millimeter to terahertz wave range and measuring the spectrum. However, it is known that electromagnetic waves in the millimeter to terahertz wave range have relatively long wavelengths and, depending on the principle of electromagnetic wave generation, have a long coherence length, which results in a large effect of interference.

[0010] In the optical system used for the above-mentioned single-wavelength measurement, the effects of interference are suppressed by configuring the optical system to match the wavelength. In contrast, when performing spectrum measurement using electromagnetic waves of multiple wavelengths in the millimeter wave to terahertz wave bands, the optical system must be adjusted to reduce the effects of interference each time the electromagnetic wave wavelength is switched. This makes it difficult to irradiate an object with electromagnetic waves in the millimeter wave to terahertz wave bands and measure its spectrum within a feasible time and effort.

[0011] The present disclosure has been made in consideration of the above circumstances, and aims to efficiently measure the spectrum of reflected waves generated by irradiating an object with electromagnetic waves while suppressing the effects of interference. [Means for solving the problem]

[0012] a signal processing unit that measures the spectrum of the composite wave, the spectrum having an intensity dependent on the frequency of the electromagnetic wave and the position of the stage, in accordance with the detection signal; and a signal processing unit that measures the spectrum of the composite wave, the spectrum having an intensity dependent on the frequency of the electromagnetic wave and the position of the stage, in accordance with the detection signal; and a signal processing unit that measures the spectrum of the composite wave, the spectrum having an intensity dependent on the frequency of the electromagnetic wave and the position of the stage, in accordance with the detection signal;

[0013] A measurement method according to one aspect of the present disclosure includes emitting an electromagnetic wave, using an optical system to emit the electromagnetic wave toward a measurement object held by a stage that can be driven along the propagation direction of the electromagnetic wave, receiving a reflected wave of the electromagnetic wave from the measurement object, and emitting a composite wave resulting from interference between the reflected wave and stray light generated by the incidence of the electromagnetic wave from a path different from the propagation path of the electromagnetic wave, detecting the composite wave emitted from the optical system, outputting a detection signal indicating the detection result, switching the frequency of the electromagnetic wave among a plurality of frequencies, moving the stage to a plurality of positions for each of the plurality of frequencies, measuring the spectrum of the composite wave having an intensity that depends on the frequency of the electromagnetic wave and the position of the stage according to the detection signal, and removing the spectrum of the stray light that was measured in advance from the spectrum of the composite wave, thereby obtaining the spectrum of the reflected wave.

[0014] a stage for holding a measurement object to be irradiated with the electromagnetic waves and capable of being driven in a propagation direction of the electromagnetic waves; an optical system for emitting the electromagnetic waves emitted from the electromagnetic wave source to the measurement object, receiving a wave of the electromagnetic waves reflected by the measurement object and emitting a composite wave resulting from interference between the reflected wave and stray light generated by the incidence of the electromagnetic waves, from a path different from the propagation path of the electromagnetic waves; and a detector for detecting the intensity of the composite wave emitted from the optical system and outputting a detection signal indicating the detection result, the program causes a computer to control the electromagnetic wave source to switch the frequency of the electromagnetic waves among a plurality of frequencies; a stage-controlling process for controlling the stage to move to a plurality of positions for each of the plurality of frequencies; a process for measuring the spectrum of the composite wave, which has an intensity that depends on the frequency of the electromagnetic waves and the position of the stage in accordance with the detection signal; and a process for obtaining the spectrum of the reflected wave by removing the spectrum of the stray light that was previously obtained from the spectrum of the composite wave. [Effects of the Invention]

[0015] According to the present disclosure, it is possible to efficiently measure the spectrum of reflected waves generated by irradiating an object with electromagnetic waves while suppressing the influence of interference. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. 1 is a diagram schematically illustrating a configuration of a measurement device according to a first embodiment. [Figure 2] FIG. 2 is a diagram showing in more detail the configuration of the measurement device according to the first embodiment. [Figure 3] 5 is a diagram showing the relationship between the distance from the measurement device to the sample and the amplitude component of the detection signal according to the first embodiment. FIG. [Figure 4] FIG. 10 is a diagram showing an example of the spectrum of a measured composite wave. [Figure 5] FIG. 10 is a diagram showing an example of spectrum acquisition at a specific distance. [Figure 6] 10A and 10B are diagrams illustrating an example of obtaining distance dependency of electromagnetic wave interference at a specific frequency. [Figure 7] FIG. 10 is a diagram showing an example of measurement conditions expressed by a plane Px and a plane Pf. [Figure 8] 4 is a flowchart of spectrum measurement by the measurement device according to the first embodiment. [Figure 9] 4 is a flowchart of a spectrum separation process in the measurement device according to the first embodiment. [Figure 10] FIG. 1 shows the spectrum of a synthetic wave and the background spectrum measured for a sample made of a polyethylene plate by the method of Comparative Example 1. [Figure 11] FIG. 10 is a diagram showing the spectrum of a synthetic wave and the background spectrum measured for a sample made of a polyethylene plate by the method of Comparative Example 2. [Figure 12] FIG. 1 is a diagram showing a spectrum measured in Example 1. [Figure 13] FIG. 10 is a diagram showing a spectrum measured in Example 2. [Figure 14] FIG. 10 is a diagram showing the spectrum measured in Example 3. [Figure 15] FIG. 10 is a diagram schematically illustrating the configuration of a measurement device according to a second embodiment. [Figure 16] 10 is a flowchart of a spectrum separation process in the measurement device according to the second embodiment. [Figure 17] FIG. [Figure 18] FIG. 10 is a diagram showing the relationship between the distance to a sample and the response when a sample in which an object is buried is measured in the second embodiment. [Figure 19] FIG. 10 is a diagram showing the spectrum measured in Example 4. [Figure 20] FIG. 10 is a diagram showing the spectrum measured in Example 5. [Figure 21] 21 is a diagram showing the results of comparing the spectrum of the buried object in FIG. 19 with the spectrum of the buried object in FIG. 20. FIG. [Figure 22]FIG. 10 is a diagram showing the spectrum measured in Example 6. [Figure 23] FIG. 2 illustrates an example of a hardware configuration. DETAILED DESCRIPTION OF THE INVENTION

[0017] Specific embodiments will be described in detail below with reference to the drawings. However, the present invention is not limited to the following embodiments. For clarity of explanation, the following description and drawings have been simplified as appropriate. The same elements are given the same reference numerals, and duplicate explanations will be omitted.

[0018] Embodiment 1 A description will be given of a measurement device 100 according to the first embodiment. The measurement device 100 is configured as a device that measures the spectrum of a medium of a sample by irradiating the sample, which is an object to be measured, with electromagnetic waves while switching frequencies and receiving the reflected waves.

[0019] In a typical measurement device designed for single-wavelength measurements, as described above, it is necessary to eliminate changes in the interference state caused by the influence of the coherence length of the electromagnetic wave each time the frequency is switched, which requires adjustment of the measurement distance and the interference state within the optical system that guides the electromagnetic wave.

[0020] In contrast, the measurement device 100 can automatically and efficiently acquire the spectrum of the reflected wave from the sample even when the frequency of the electromagnetic wave is changed, without the need to adjust the measurement distance or the optical system.

[0021] 1 shows a schematic configuration of a measurement apparatus 100 according to the first embodiment. The measurement apparatus 100 includes an electromagnetic wave source 1, an optical system 2, a stage 3, a detector 4, a signal processing unit 5, and a control unit 6.

[0022] The electromagnetic wave source 1 is configured to emit electromagnetic waves of a predetermined frequency, for example, in the millimeter wave to terahertz wave range, to the optical system 2. The millimeter wave frequency is 30 GHz to 300 GHz (equivalent to approximately 1 mm to 10 mm in wavelength), and the terahertz wave frequency is, for example, 300 GHz to 3 THz (equivalent to approximately 100 μm to 1 mm in wavelength). The electromagnetic wave source 1 emits electromagnetic waves of a desired frequency within the millimeter wave band and terahertz wave band to the optical system 2. Hereinafter, the electromagnetic waves emitted by the electromagnetic wave source 1 will be referred to as electromagnetic waves W. Note that the frequency of the electromagnetic waves W is not limited thereto, and may be, for example, centimeter waves with frequencies of 3 GHz to 30 GHz (equivalent to approximately 1 cm to 10 cm in wavelength) or frequencies in the microwave range (frequency 300 MHz to 1 m, equivalent to approximately 1 mm to 1 m in wavelength) including the millimeter waves. The frequency of the electromagnetic waves W can be set appropriately depending on the object to be measured.

[0023] The optical system 2 emits an electromagnetic wave W incident from the electromagnetic wave source 1 to a sample S placed on a stage 3, and also emits a reflected wave W reflected by the sample S. s 2 shows a more detailed configuration of the measurement device 100 according to the first embodiment. The optical system 2 includes a lens 21, a beam splitter 22, lenses 23 and 24, and a housing 25.

[0024] The electromagnetic wave W emitted from the electromagnetic wave source 1 is collimated by a lens 21, and then a portion of the wave passes through a beam splitter 22. The electromagnetic wave W that passes through the beam splitter is converged by a lens 23 and enters a sample S placed on a stage 3.

[0025] A part or all of the electromagnetic wave W incident on the sample S is reflected by the surface of the sample S, resulting in a reflected wave W s The reflected wave W incident on the lens 23 is s is reflected by the beam splitter 22 and enters the lens 24. Then, the reflected wave W s is converged by the lens 24 and enters the detector 4.

[0026] In this configuration, the detector 4 receives the reflected wave W from the sample S. s In addition, stray light W caused by internal reflections of the optical system 2 r is incident on the beam splitter 22. A portion of the electromagnetic wave W incident on the beam splitter 22 is reflected by the beam splitter 22 in a direction different from that of the electromagnetic wave W that passed through the beam splitter 22. The electromagnetic wave W reflected by the beam splitter 22 is scattered by the housing 25 and the like, and becomes stray light inside the optical system 2. Note that the cause of stray light is not limited to this, and it can be caused by various factors such as reflection by parts other than the beam splitter 22 and scattering caused by other parts. Stray light Wr, which is a composite wave of stray light caused by these various factors, is converged by the lens 24 and enters the detector 4.

[0027] That is, the detector 4 receives a composite wave resulting from interference between the reflected wave Ws converged by the lens 24 and the stray light Wr.

[0028] The stage 3 is configured to be movable in both directions along the beam axis of the electromagnetic wave W. That is, the stage 3 can move along the beam axis of the electromagnetic wave W in a direction from a far position to a near position relative to the emission port of the electromagnetic wave W of the optical system 2, and in a direction from a near position to a far position.

[0029] As described above, the detector 4 receives the reflected wave W s and stray light W r Therefore, the detector 4 detects the reflected wave W s and stray light W rThe detector 4 detects a composite wave resulting from interference between the two and outputs a detection signal DET indicating the detection result to the signal processing unit 5. The detector 4 is configured as an electronic device detector using, for example, a Schottky barrier diode, and outputs a current signal indicating the optical intensity of the incident composite wave as the detection signal DET. The electromagnetic wave detector is not limited to the above example, and various detectors can be used. When the electromagnetic wave is a terahertz wave, various detectors such as thermal and quantum type detectors other than the above electronic device type detectors, for example, as described in Non-Patent Document 3, can be used. Note that the detection signal DET output by the detector 4 is not limited to a current signal, and may be a voltage signal depending on the detection method.

[0030] The signal processing unit 5, the details of which will be described later, monitors the detection signal DET to obtain the spectrum of the amplitude of the reflected wave Ws. However, even if the composite wave is observed as it is, the reflected wave Ws, which indicates information about the sample S, s In addition, the interference state of the stray light generated in the optical system 2 changes depending on the frequency of the electromagnetic wave, so the stray light W incident on the detector 4 r varies depending on the frequency. Therefore, the reflected wave W s To selectively observe the stray light W r Therefore, the signal processing unit 5 removes the influence of the reflected wave W included in the composite wave according to the following principle and procedure. s and stray light W r and are spectrally separated.

[0031] The control unit 6 controls the operations of the electromagnetic wave source 1, the stage 3 and the signal processing unit 5 by outputting control signals CON1 to CON3 to the electromagnetic wave source 1, the stage 3 and the signal processing unit 5, respectively.

[0032] Next, the principle of spectrum separation in the signal processing unit 5 will be explained. Here, it is assumed that there is no reflecting object in the medium that constitutes the sample S. In this case, when the frequency of the electromagnetic wave is f, the composite wave W incident on the detector 4 is c is expressed by the following formula:

number

[0033] The detection signal DET output by the detector 4 can be regarded as indicating the amplitude component of equation [1]. Hereinafter, the voltage of the voltage signal indicating the amplitude of the detection signal DET will also be referred to as a response voltage. When the detection signal DET is a current signal, the detection signal DET may be used as is as the response voltage. When the detection signal DET is a current signal, a voltage signal converted from the detection signal DET by the signal processing unit 5 may be used as the response voltage. The amplitude component I s (f, x) is expressed by the following formula. For simplicity, I s (f,x) is simply I s It can also be written as:

number

number

number

[0034] Here, when measurements are taken while changing the distance x, as can be seen from equation [2] and Figure 3, the amplitude component I s is the maximum value maxI s and the minimum value minI s The stray light W r The amplitude of C r and the reflected wave W s The amplitude of C s When the cases are divided according to the magnitude relationship between stray light W r The amplitude of C r and reflected wave W s The amplitude of C s is expressed as follows:

[0035] C r >C s In this case, the stray light W r The amplitude of C r and reflected wave W s The amplitude of C s is expressed as follows:

number

number

number

[0036] From the above, the stray light W r The amplitude of C r and the reflected wave W s The amplitude of C s If the magnitude relationship between r The amplitude of C r and the reflected wave W s The amplitude of C s It can be determined that:

[0037] In addition, stray light W r The amplitude of C r and the reflected wave W s The amplitude of C s The magnitude relationship between can be determined in advance by various methods. For example, by performing a preliminary measurement using an electromagnetic wave absorber as the sample S, the reflected wave W from the sample can be determined by s can be suppressed to zero or a negligibly small level. r The amplitude of C r Only the ion concentration can be measured.

[0038] This allows us to obtain the amplitude I of the composite wave when measured using the sample to be measured. s The reflected wave W contained in s The amplitude of C s is the stray light W measured in advance. r The amplitude of C r can be separated using

[0039] Based on the above principle, the signal processing unit 5 calculates the amplitude I s , stray light W r The amplitude of C r and the reflected wave W s The amplitude of C s and the reflected wave W s The amplitude of C s Only the following can be extracted.

[0040] Next, we will explain spectrum measurement by the measurement apparatus 100. The measurement apparatus 100 measures the spectrum while changing the frequency f of the radio waves output by the electromagnetic wave source 1 and also changing the distance between the measurement apparatus 100 and the stage.

[0041] The frequency switching of the electromagnetic wave W in spectrum measurement will be explained. The frequency of the electromagnetic wave W output from the electromagnetic wave source 1 is sequentially switched to one of a plurality of frequencies spaced apart by a predetermined interval in the band to be measured. For example, Nf frequencies are set within the frequency measurement range, and the lower limit frequency is f1 and the upper limit frequency is f2. Nf The interval between two adjacent frequencies is Δf. Here, Nf is an arbitrary integer equal to or greater than 2. If j is an integer equal to or greater than 1 and equal to or less than Nf, the jth frequency f counting from the low frequency side is j is f j =f1+(j-1)Δf.

[0042] Next, the movement of the stage 3 during spectrum measurement will be described. The stage 3 moves sequentially to one of a plurality of positions that are spaced apart by a predetermined distance within the driving range during measurement. For example, Nx positions are set within the driving range of the stage 3, and the farthest position from the measurement device 100 is designated as x1, the closest position is designated as x2, and so on. Nx The distance between two adjacent positions is Δx. Here, Nx is an arbitrary integer equal to or greater than 2. If k is an integer equal to or greater than 1 and equal to or less than Nx, the kth position x counting from the side farthest from the measuring device 100 is k is x k =x1+(k-1)Δx.

[0043] Then, by measuring the amplitude Is of the composite wave expressed by equation [2] for each of the Nf × Nx measurement conditions consisting of Nf frequencies and Nx positions, the spectrum of the composite wave can be measured as a function of frequency f and position x.

[0044] Needless to say, the control unit 6 controls the operations of the electromagnetic wave source 1, the stage 3, and the signal processing unit 5 using the control signals CON1 to CON3, thereby making it possible to perform measurements under Nf×Nx different measurement conditions.

[0045] Figure 4 shows an example of the spectrum of a measured composite wave. Here, the horizontal axis represents frequency f, and the vertical axis represents distance x. The vertical axis represents the response voltage V corresponding to amplitude Is. Unless otherwise specified, graphs showing the spectrum and distance dependence of interference display voltage V instead of amplitude Is. Using the above-described measurement method, the spectrum of the composite wave can be measured as a curved surface in three-dimensional space consisting of Nf × Nx observed values ​​of amplitude Is (or voltage V) of the composite wave. From these measurement results, it is possible to obtain the spectrum of the composite wave at a specific distance, or the distance dependence of electromagnetic wave interference at a specific frequency.

[0046] An example of obtaining a spectrum at a specific distance is shown in Figure 5. As shown in Figure 5, the spectrum at a specific distance can be obtained by slicing the spectrum of the composite wave measured on a plane Px parallel to the fV plane corresponding to the specific distance (250 mm in Figure 5).

[0047] An example of obtaining the distance dependency of electromagnetic wave interference at a specific frequency is shown in Figure 6. As shown in Figure 6, by slicing the spectrum of the composite wave measured on a plane Pf parallel to the xV plane corresponding to a specific frequency (15 GHz in Figure 6), it is possible to obtain the state of electromagnetic wave interference at a specific frequency.

[0048] Furthermore, the point where plane Px and plane Pf intersect represents one measurement condition. Figure 7 shows an example of measurement conditions represented by plane Px and plane Pf. As shown in Figure 7, the intersection of plane Px (250 mm) and plane Pf (15 GHz) corresponds to a single measurement value of amplitude Is.

[0049] 8 shows a flowchart of spectrum measurement by the measurement device 100 according to the first embodiment. The measurement device 100 executes the following steps ST1 to ST3 to measure the spectrum of a composite wave including a reflected wave from the sample S, and separates the spectrum of the reflected wave. Note that the storage unit 51 of the signal processing unit 5 has equations [5] to [7] stored in advance.

[0050] Step ST1 By placing a dummy sample such as a radio wave absorber that does not reflect radio waves on the stage 3, the spectrum in the measurement band is measured without the reflected wave returning to the measurement device 100. This allows the stray light W generated by the measurement device 100, which does not include the reflected wave component, to be measured. r The spectrum measured here is used as the stray light W r The spectrum is kept as a reference spectrum.

[0051] Stray light W r As mentioned above, the measurement of the reference spectrum of is assumed to be in a state where there is no reflected wave, and therefore is not considered to depend on the position of the stage 3. In other words, by switching the frequency of the electromagnetic wave W in Nf ways without moving the stage 3, the stray light W r It should be noted that, for example, when unwanted reflected waves from the stage 3 and its surrounding members and devices are incident on the measurement device 100, these unwanted reflected waves may cause stray light W r In this case, as described above, the stage 3 is moved to Nx positions for each of the Nf frequencies of the electromagnetic wave W, and the stray light W r By observing the maximum value of , the stray light W r A reference spectrum of may be measured.

[0052] Step ST2 Next, the sample S to be measured is placed on the stage 3, and the spectrum in the measurement band is measured. s and stray light W r The spectrum of the composite wave produced by the interference between the two is measured.

[0053] Step ST3 The signal processing unit 5 calculates the stray light W measured in advance in step ST1. r Using the reference spectrum of the reflected wave W s 9 shows a flowchart of the spectrum separation process in the measurement apparatus 100 according to the first embodiment.

[0054] Step S1 The initial value of the counter value j that specifies the frequency is set to 1 (j=1).

[0055] Step S2 Referring to the spectrum of the composite wave, the jth frequency f j Positions x1 to x Nx From the Nx measured values ​​at s and the minimum value minI s and asks for.

[0056] Step S3 The maximum value maxI s and minimum value minI s By substituting into the following equation, the jth frequency f i The reflected wave W s The amplitude of C s and stray light W r The amplitude of C r A first amplitude C1 and a second amplitude C2 are calculated as candidates.

number

[0057] Step S4 It is determined whether the first amplitude C1 is equal to the second amplitude C2 (C1=C2).

[0058] Step S5 If the first amplitude C1 is equal to the second amplitude C2 (step S4: YES), the amplitude I of the measured composite wave is calculated using equation [7]. s Reflected light W contained in s The amplitude of C s Then, the process proceeds to step S9.

[0059] Step S6 If the first amplitude C1 is different from the second amplitude C2 (step S4: NO), which of the first amplitude C1 and the second amplitude C2 is the stray light W r The jth frequency f derived from the reference spectrum of i Reference amplitude C at r_REF Determine whether it is close to

[0060] Step S7 The first amplitude C1 is greater than the second amplitude C2 in the stray light W r Reference amplitude C r_REF If it is close to (step S6: YES), the reflected light W s The amplitude of C s That is, the first amplitude C1 is calculated as the stray light W r The amplitude of C r , the second amplitude C2 is the reflected light W s The amplitude of C s Then, the process proceeds to step S9.

[0061] Step S8 The second amplitude C2 is smaller than the first amplitude C1 by the reference amplitude Cr_REF If it is close to (step S6: NO), the reflected light W s The amplitude of C s That is, the second amplitude C2 is calculated as the stray light W r The amplitude of C r , the first amplitude C1 is the reflected light W s The amplitude of C s Then, the process proceeds to step S9.

[0062] Step S9 It is determined whether the counter value j is the maximum value Nf (j=Nf).

[0063] Step S10 If the counter value j is not the maximum value Nf (step S9: NO), 1 is added to the counter value j, and the process returns to step S2.

[0064] Step S11 If the counter value j is the maximum value Nf (step S9: YES), the calculated frequencies f1 to f Nf Nf amplitudes C s Based on the reflected light W s Construct a spectrum of.

[0065] By following the above procedure, the measurement apparatus 100 can separate the spectrum of the reflected wave from the spectrum of the composite wave.

[0066] Next, an example of measuring the spectrum of a reflected wave using the measurement device 100 will be described. Here, measurements were performed using samples of three different materials in a frequency range of 7.5 to 24 GHz and a distance measurement range of 35 mm, 235 to 270 mm from the measurement device 100. When acquiring the interference state by varying the distance at a certain frequency, the period of the change in intensity of the response voltage is half the wavelength of the electromagnetic wave. Therefore, the period is approximately 20 mm at a frequency of 7.5 Hz and approximately 6.25 mm at a frequency of 24 Hz. Therefore, a measurement range of at least approximately 20 mm is required in the frequency range of 7.5 to 24 GHz. Furthermore, since the period is approximately 6.25 mm at a frequency of 24 Hz, the distance between two adjacent sampling points must be 3.125 mm or less. In the following examples, the distance step size was set to 0.5 mm to measure the phase shift described below.

[0067] Furthermore, to examine the effects of this method, spectra obtained by two different measurement methods were used as comparative examples. Comparative Example 1 is a spectrum measured by adjusting the distance to the sample so that the response was maximized at each frequency. Comparative Example 2 is a spectrum measured by fixing the distance from the measurement device to the sample at the focal position of the optical system. In Comparative Examples 1 and 2, a background was acquired in advance, and the spectrum of the composite wave was obtained by taking the difference between the measurement data and the background.

[0068] [Example 1] Spectral measurements were carried out under the above measurement conditions using a polyethylene plate as a sample.

[0069] FIG. 10 shows the spectrum of the composite wave and the background spectrum measured on a sample made of a polyethylene plate using the method of Comparative Example 1. FIG. 11 shows the spectrum of the composite wave and the background spectrum measured on a sample made of a polyethylene plate using the method of Comparative Example 2. As can be seen from FIGS. 10 and 11, these methods are significantly affected by electromagnetic wave interference, and the spectrum of the composite wave and the background spectrum are similar. Depending on the frequency, there are cases where the amplitude of the background is larger than the amplitude of the composite wave. Therefore, even if the difference between the spectrum of the composite wave and the spectrum of the background is taken, it is theoretically difficult to accurately obtain the spectrum of the reflected wave.

[0070] FIG. 12 shows a comparison of the spectrum measured by this method with the spectra obtained by Comparative Examples 1 and 2. In Comparative Example 1, the voltage value fluctuates greatly due to the influence of interference, and it is thought that the reliability of the measurement results is low. In Comparative Example 2, although an improvement over Comparative Example 1, the voltage value fluctuates greatly, and it is thought that the reliability of the measurement results is still low. In contrast, with this method, it is possible to suppress or eliminate the influence of interference, so that the fluctuations in the voltage value are small and it is clear that the reflected wave can be suitably extracted.

[0071] [Example 2] Next, spectrum measurement was performed using an aluminum plate as a sample under the above-mentioned measurement conditions. Note that the measurement conditions were the same as in Example 1 except for the sample. Fig. 13 shows the spectrum measured in Example 2. As can be seen from Fig. 13, even though the sample was different, the measurement device 100 was able to suppress or eliminate the influence of interference and preferably extract the reflected wave, just as in Example 1.

[0072] [Example 3] Next, a spectrum was measured using a plate made of ZEONEX (registered trademark) 480, a cycloolefin polymer manufactured by Zeon Corporation, as a sample. The measurement conditions were the same as in Examples 1 and 2, except for the different sample. Figure 14 shows the spectrum measured in Example 3. As can be seen from Figure 14, the measurement device 100 was able to suppress or eliminate the influence of interference and preferably extract the reflected wave, just as in Examples 1 and 2, even though the sample was different.

[0073] As described above, according to this configuration, even if the materials of the samples to be measured are different, by performing spectral separation, it is possible to obtain the spectrum of the reflected wave from the sample without the need to adjust the measurement distance, etc.

[0074] Embodiment 2 In the first embodiment, the stray light W r The amplitude of C r and reflected light W s The amplitude of C s Since the magnitude relationship between the reflected light W and the reflected light W is unknown, the condition determination shown in steps S4 and S6 of FIG. s The amplitude of C s In contrast, in the present embodiment, the equation used for separating the stray light W r The amplitude of C r and reflected light W s The amplitude of C s By pre-setting the magnitude relationship between the reflected light W s The amplitude of C s A measuring device for separating the above will be described.

[0075] 15 schematically shows the configuration of a measurement apparatus 200 according to the second embodiment. Compared to the measurement apparatus 100, the measurement apparatus 200 further includes a reflector 26 in the optical system 2. The other configuration of the measurement apparatus 200 is the same as that of the measurement apparatus 100, and therefore a description thereof will be omitted.

[0076] A part of the incident electromagnetic wave W is reflected by the beam splitter 22. Here, the electromagnetic wave reflected by the beam splitter 22 is referred to as the electromagnetic wave Wa The reflector 26 reflects, for example, electromagnetic waves W a is set in the direction in which the electromagnetic wave W a The electromagnetic wave W reflected by the reflector 26 is a A part of the light passes through the beam splitter 22 and reaches the detector 4 as stray light W r It is incident as

[0077] In this way, the reflector 26 is provided in the optical system 2 to prevent the stray light W incident on the detector 4. r By increasing the intensity of the stray light W r The amplitude of C r , reflected light W s The amplitude of C s Always be larger than (C r >C s ) can be done.

[0078] Next, a procedure for measuring a spectrum in the measurement apparatus 200 will be described. In the spectrum measurement in the measurement apparatus 200, step ST3 for performing spectrum separation in the measurement apparatus 100 is replaced with step ST4. In the measurement apparatus 200, stray light W included in the composite wave is r The amplitude of C r is the reflected light W s The amplitude of C s is always greater than (C r >C s ) and this fact can be utilized to simplify the processing in step ST4. Fig. 16 shows a flowchart of the spectrum separation processing in the measurement device according to the second embodiment.

[0079] Step ST4 The signal processing unit 5 calculates the stray light W measured in advance in step ST1. r Using the reference spectrum of the reflected wave W s16, steps S3 to S8 are removed from step ST3 in Fig. 9, and step S12 is inserted instead of step S3. Steps S1, S2, and S9 to S11 are the same as in Fig. 9.

[0080] Step S1 The initial value of the counter value j that specifies the frequency is set to 1 (j=1).

[0081] Step S2 Referring to the spectrum of the composite wave, the jth frequency f j Positions x1 to x Nx From the Nx measured values ​​at s and the minimum value minI s and asks for.

[0082] Step S12 The maximum value maxI s and minimum value minI s By substituting this into the above equation [5], the amplitude of the measured composite wave I s Reflected light W contained in s The amplitude of C s Calculate.

[0083] Step S9 It is determined whether the counter value j is the maximum value Nf (j=Nf).

[0084] Step S10 If the counter value j is not the maximum value Nf (step S9: NO), 1 is added to the counter value j, and the process returns to step S2.

[0085] Step S11 If the counter value j is the maximum value Nf (step S9: YES), the calculated frequencies f1 to f Nf Nf amplitudes C s Based on this, a spectrum of the reflected light is constructed.

[0086] Through the above procedure, the measurement device 200 can separate the spectrum of the reflected wave from the spectrum of the composite wave. Furthermore, the measurement device 200 can separate the spectrum of the reflected wave more easily than the measurement device 100, and is expected to achieve faster processing speeds.

[0087] Furthermore, compared to the first embodiment, the path of stray light is controlled by the reflector, so that it is possible to prevent or suppress stray light from entering the detector 4 via other paths when there is no reflector. This also makes it possible to reduce the burden on the design of the measurement device, which takes into account stray light from unexpected paths.

[0088] Embodiment 3 In the first and second embodiments, an example in which the sample is made of a single material has been described. However, the sample to be measured may contain objects of different compositions buried therein, such as rebar buried in a concrete pillar. In this case, it is preferable to be able to acquire not only the reflected wave from the sample surface but also the spectrum of the reflected wave from the buried object. If the spectrum of the reflected wave from the buried object can be acquired, it can be used as a non-destructive testing method for investigating the internal structure of the object to be measured, and is considered to be useful.

[0089] Therefore, in this embodiment, a method for detecting an object buried in a sample will be described by applying the spectral separation in the measurement device 100 described in Embodiment 1. Note that, hereinafter, an object buried in a sample and made of a material different from the medium constituting the sample will be simply referred to as an embedded object.

[0090] First, we will explain the reflected wave from the buried object. A part of the electromagnetic wave W incident on the sample S is reflected by the surface of the sample S, and the reflected wave W s The electromagnetic wave W incident on the sample S returns to the optical system 2 as a reflected beam. The part of the electromagnetic wave W that is not reflected by the surface of the sample S propagates through the medium of the sample S and reaches the buried object M.

[0091] The electromagnetic wave W that reaches the buried object M is reflected by the surface of the buried object M, and the reflected wave W m Then, return to optical system 2.

[0092] In this case, the composite wave W c is expressed by the following formula:

number

[0093] As in the case of equation [2], the amplitude component I of the detection signal when an object M is buried in the sample S is m is expressed by the following equation from equation [9].

number

[10] . Figure 17 shows the positional deviation φ. Here, the sample without the buried object M (the reference sample S described later) REF) In the spectrum of the composite wave when measuring j The periodic pattern formed by the curve CV showing the relationship between the amplitude Im of the composite wave at stage 3 and the position x of stage 3 is called P. m In addition, a sample without buried object M (a reference sample S described later) REF) In the spectrum of the composite wave when measuring j Amplitude of the composite wave at Is The periodic pattern formed by the curve CV showing the relationship between the position x of stage 3 and the s In this case, the periodic pattern P m and the periodic pattern P s means that the same frequency f j Since the measurements were taken at , it can be seen that the pattern oscillates at the same period in the x direction. However, due to differences in the measurement objects, the periodic pattern P m and the periodic pattern P s When these are overlapped, a misalignment occurs in the x direction. φ in Equation

[10] is the periodic pattern P m and the periodic pattern P s In the diagram on the right side of Fig. 17, x is converted to Θ based on equation [3].

[0094] reflected wave W s and W m The amplitude D(f) of the composite wave is given by the following equation:

number

number

number

[0095] In this state, the spectrum of the composite wave is measured and spectral separation is performed in the same manner as in the first embodiment, so that the stray light W r The spectrum of the reflected wave W s and W m The spectrum of the amplitude D of the composite wave can be obtained.

[0096] In this embodiment, the amplitude of the composite wave D is converted into the reflected wave W m The amplitude of C m In order to extract the reflected wave W s The amplitude of C s Here, the reflected wave W s The amplitude of C s is a reference sample S made of the same material as sample S, but without buried object M. REF is assumed to be acquired in advance by performing the same measurement as described in the first embodiment. Here, the memory unit 51 of the signal processing unit 5 stores the measured reflected wave W s The amplitude of C s is stored in advance.

[0097] FIG. 18 shows the relationship between the distance x to the sample S and the response when measuring the sample S in which the buried object M is buried. As shown in FIG. 18, the amplitude component I m is the origin (0,0) and the point (C r , 0) on a circle of radius D. As shown in Figure 18, point P moves on the circle according to changes in Θ, just as in Figure 3.

[0098] As mentioned above, the displacement φ is a function of a single frequency f j The curve PL when buried object M is present, measured at m and the curve PL when there is no buried object s This can be easily determined by comparing

[0099] The reflected wave W from the surface of the sample S s The amplitude of C s When the positional deviation φ is given in advance, the amplitude D of the measured composite wave is used to calculate the reflected wave W by the buried object M. m The amplitude of C m is expressed by the following equation: Here, the positional deviation φ is stored in advance in the storage unit 51 of the signal processing unit 5.

number

[0100] As explained above, according to this method, even if the depth d of the buried object and the relative dielectric constant ε of the sample S are unknown, the reflected wave W m The amplitude of C m can be measured and its spectrum can be obtained.

[0101] Next, a description will be given of an example of measuring the spectrum of a reflected wave in embodiment 2. Here, measurements were carried out using three different types of samples.

[0102] [Example 4] Spectral measurements were performed on a sample in which an aluminum plate was embedded in a polyethylene plate under the same measurement conditions as in Examples 1 to 3. In this example, the aluminum plate was embedded at a depth of 21 mm from the surface of the polyethylene plate on the side where the electromagnetic waves were incident. Figure 19 shows the spectrum measured in Example 4. Figure 19 also shows the spectrum of a reference sample made of a polyethylene plate as a comparative example.

[0103] As shown in FIG. 19, the measurement device 100 measures the reflected wave W m The amplitude of C m is the reflected wave W from the polyethylene plate, which is the reference sample. s The amplitude of C s It can be seen that it is possible to measure it separately.

[0104] [Example 5] Spectral measurements were performed on a sample in which an aluminum plate was embedded in a plate made of ZEONEX 480 under the same measurement conditions as in Examples 1 to 3. In this example, the aluminum plate was embedded at a depth of 2 mm from the surface of the plate made of ZEONEX 480 on the side where the electromagnetic waves were incident. Figure 20 shows the spectrum measured in Example 5. As a comparative example, Figure 20 also shows the spectrum measured using a plate made of ZEONEX 480 as a reference sample.

[0105] As shown in FIG. 20, the measurement device 100 can measure the reflected wave W from the aluminum plate, which is the embedded object, even if the medium in which the aluminum plate is embedded is changed. m The amplitude of C m is the reflected wave W from the reference sample ZEONEX 408 plate. s The amplitude of C s It can be seen that it is possible to measure it separately.

[0106] 21 shows the comparison result between the spectrum SP4 of the buried object in FIG. 19 and the spectrum SP5 of the buried object in FIG. 20. As shown in FIG. 21, even if the medium in which the aluminum plate is buried changes, the reflected wave W m The amplitude of C m shows an approximate spectrum. This shows that the measurement device 100 can acquire the spectrum of the reflected wave from the buried object while suppressing the dependency on the medium in which the buried object is buried.

[0107] [Example 6] Spectral measurements were performed on a sample in which an aluminum plate was embedded in concrete under the same measurement conditions as in Examples 1 to 3. In this example, the aluminum plate was embedded at a depth of 10 mm from the surface of the concrete plate on the side where the electromagnetic waves were incident. FIG. 22 shows the spectrum measured in Example 6. As a comparative example, FIG. 22 also shows the spectrum of a reference sample consisting only of an aluminum plate, along with the measurement results of a sample measured using a general method. The measurement results of the sample measured using the general method used as the comparative example were obtained by subtracting the measurement results of the sample consisting only of concrete using the method of Comparative Example 1 from the measurement results of the sample in which aluminum was embedded using the method of Comparative Example 1 described above.

[0108] In Figure 22, the sample measurement results obtained using a conventional method exhibited spectra that were far removed from reality, such as negative values, making the results unreliable. In contrast, while the spectral measurement using this method did not eliminate the effects of absorption by concrete and internal interference, the measurement results obtained using this method were close to those of the reference sample. This demonstrates that this configuration can effectively separate the spectra of reflected waves from a sample even when the sample is buried in a medium of different composition.

[0109] As described above, the measuring device 100 can acquire the spectrum of the reflected wave from an embedded object even when the embedded object has a different composition from the medium on the sample surface.

[0110] The reflected wave W from the buried object M obtained by this method m The amplitude of C m is affected by interference due to reflection between the surface of the buried object M and the surface of the sample S. In addition, the reflected wave W m The spectrum of the reflected wave W by the buried object M m The ideal spectrum is the product of the absorption spectrum of the medium of the sample S. Therefore, the reflected wave W m The spectrum of the reflected wave is different from the spectrum of the reflected wave observed when the electromagnetic wave W is incident directly on the buried object M without passing through the medium of the sample S.

[0111] However, the reflected wave W from the buried object M m The amplitude of C m Whether or not the reflected wave W due to the buried object M is measured can be easily determined by measuring the spectrum of the composite wave. m By monitoring whether or not the spectrum can be acquired, it is possible to investigate whether or not there is an object buried in the sample, even if the internal structure of the sample is unknown.

[0112] As a result, the measuring device 100 can also detect buried objects in the sample.

[0113] Other embodiments The present invention is not limited to the above-described embodiments, and can be modified as appropriate without departing from the spirit of the present invention. For example, in the third embodiment, the buried object M is detected by applying the spectral separation in the measurement device 100 according to the first embodiment, but the present invention is not limited to this. Similarly, the measurement device 200 according to the second embodiment may also detect the buried object M by applying the spectral separation.

[0114] In the above-described embodiment, the present invention has been described primarily as a hardware configuration. However, this is not limiting. For example, any processing in one or both of the signal processing unit 5 and the control unit 6 can be realized by having a central processing unit (CPU) execute a computer program. In this case, the computer program can be stored and supplied to a computer using various types of non-transitory computer-readable media. Non-transitory computer-readable media include various types of tangible storage media. Examples of non-transitory computer-readable media include magnetic recording media (e.g., flexible disks, magnetic tapes, hard disk drives), magneto-optical recording media (e.g., magneto-optical disks), CD-ROMs (Read Only Memory), CD-Rs, CD-R / Ws, and semiconductor memories (e.g., mask ROMs, programmable ROMs (PROMs), erasable PROMs (EPROMs), flash ROMs, and random access memories (RAMs)). The program may also be supplied to a computer using various types of transitory computer-readable media. Examples of the temporary computer-readable medium include an electric signal, an optical signal, and an electromagnetic wave. The temporary computer-readable medium can provide the program to the computer via a wired communication path such as an electric wire or an optical fiber, or via a wireless communication path.

[0115] Next, an example of a hardware configuration for realizing one or both of the signal processing unit 5 and the control unit 6 is shown. FIG. 23 shows an example of the hardware configuration. One or both of the signal processing unit 5 and the control unit 6 can be realized by a computer 1000 such as a dedicated computer or a personal computer (PC). However, the computer does not need to be physically single, and may be multiple when performing distributed processing. As shown in FIG. 23, the computer 1000 has a CPU (Central Processing Unit) 1001, a ROM (Read Only Memory) 1002, and a RAM (Random Access Memory) 1003, which are interconnected via a bus 1004. Note that although explanation of OS software for operating the computer is omitted, it is assumed that the computer that constitutes this information processing device also has such software.

[0116] An input / output interface 1005 is also connected to the bus 1004. To the input / output interface 1005, for example, an input unit 1006 including a keyboard, mouse, sensor, etc., a display including a CRT, LCD, etc., an output unit 1007 including headphones, speakers, etc., a storage unit 1008 including a hard disk, etc., and a communication unit 1009 including a modem, terminal adapter, etc. are connected.

[0117] The CPU 1001 executes various processes in accordance with various programs stored in the ROM 1002 or various programs loaded from the storage unit 1008 to the RAM 1003. In this embodiment, the CPU 1001 executes various processes, for example, the processes of the various units of the information processing device described below. A graphics processing unit (GPU) may be provided to execute various processes, for example, the processes of the various units of the information processing device described below, in accordance with various programs stored in the ROM 1002 or various programs loaded from the storage unit 1008 to the RAM 1003, similar to the CPU 1001. The GPU is suitable for performing routine processing in parallel, and by applying it to neural network processing described below, the processing speed can be improved compared to the CPU 1001. The RAM 1003 also stores data necessary for the CPU 1001 and the GPU to execute various processes.

[0118] The communication unit 1009 performs communication processing via the Internet (not shown), for example, transmits data provided by the CPU 1001, and outputs data received from a communication partner to the CPU 1001, RAM 1003, and storage unit 1008. The storage unit 1008 exchanges data with the CPU 1001 and stores and erases information. The communication unit 1009 also performs communication processing of analog or digital signals with other devices.

[0119] The input / output interface 1005 is also connected to a drive 1010 as needed, and, for example, a magnetic disk 1011, an optical disk 1012, a flexible disk 1013, or a semiconductor memory 1014 is appropriately attached, and computer programs read from these are installed in the memory unit 1008 as needed.

[0120] An information processing system according to embodiment 1 will be described. The information processing system according to this embodiment is configured to include a plurality of local stations that perform supervised learning of local models using images as input data, and a central station that constructs an integrated model based on the learning results at each distributed learning station. [Explanation of symbols]

[0121] 1. Electromagnetic wave source 2 Optical system 3 Stages 4. Detector 5. Signal Processing Section 6 Control Unit 21, 23, 24 lenses 22 Beam Splitter 25 cabinets 26 Reflector 100 Measuring Device 1000 computers 1001 CPU 1002 ROM 1003 RAM 1004 Bus 1005 Input / Output Interface 1006 Input section 1007 Output section 1008 Storage section 1009 Communications Department 1010 Drive 1011 Magnetic Disk 1012 Optical disc 1013 Flexible Disk 1014 Semiconductor Memory S Sample M Buried object DET detection signal W, Wa electromagnetic wave W m , W s reflected wave W r stray light

Claims

1. an electromagnetic wave source that emits electromagnetic waves; a stage that holds a measurement object to be irradiated with the electromagnetic wave and that can be driven along the propagation direction of the electromagnetic wave; an optical system that emits the electromagnetic wave emitted from the electromagnetic wave source to the measurement object, receives a reflected wave of the electromagnetic wave from the measurement object, and emits a composite wave resulting from interference between the reflected wave and stray light generated by the incidence of the electromagnetic wave from a path different from the propagation path of the electromagnetic wave; a detector that detects the composite wave emitted from the optical system and outputs a detection signal indicative of the detection result; a control unit that controls the electromagnetic wave source to switch the frequency of the electromagnetic wave among a plurality of frequencies and controls the stage to move to a plurality of positions for each of the plurality of frequencies; a signal processing unit that measures the spectrum of the composite wave, the spectrum having an intensity depending on the frequency of the electromagnetic wave and the position of the stage, in response to the detection signal, and obtains the spectrum of the reflected wave by removing the spectrum of the stray light obtained in advance from the spectrum of the composite wave. Measuring equipment.

2. a process of measuring the spectrum of the composite wave by moving the stage to a plurality of positions for one frequency among the plurality of frequencies, is performed for each of the plurality of frequencies, thereby measuring the spectrum of the composite wave; In the above process, the control unit instructs the electromagnetic wave source to select the one frequency, causing the electromagnetic wave source to emit the electromagnetic wave of the one frequency to the optical system; the control unit moves the stage to the plurality of positions while the signal processing unit monitors the detection signal; When the stage has been moved to all of the plurality of positions, the control unit determines whether each of the plurality of frequencies has been selected as the one frequency; When each of the plurality of frequencies is selected as the one frequency, measurement of the spectrum of the composite wave is terminated; If none of the plurality of frequencies has been selected as the one frequency, the one frequency is updated to a frequency that has not yet been selected among the plurality of frequencies, and the process is repeated. The measuring device according to claim 1 .

3. The frequency of the electromagnetic wave is f, and the composite wave W appearing in the detection signal is ｃ is expressed by the following formula: [Equation 1] However, c ０ is the speed of light in a vacuum, C ｒ (f) is the amplitude of the stray light, C ｓ is the amplitude of the reflected wave from the surface of the measurement object, x is the distance from the optical system to the surface of the measurement object, θ is the phase shift of the stray light relative to the electromagnetic wave emitted from the electromagnetic wave source, C ｒｓ (f, x) is the amplitude of the composite wave, θ ｓ (f, x) is the phase shift due to interference, The amplitude of the composite wave I ｓ is expressed by the following formula: [Equation 2] Θ is expressed by the following formula: [Equation 3] The amplitude of the composite wave I ｓ The maximum value maxI ｓ and the minimum value minI ｓ The amplitude C of the reflected wave ｒ and the amplitude C of the stray light ｓ teeth, C ｒ >C ｓ in the case of, [Equation 4] is expressed as C ｒ <C ｓ in the case of, [Equation 5] [Equation 6] is expressed as The signal processing unit The amplitude C of the stray light ｒ The spectrum of The spectrum of the composite wave and the amplitude C of the stray light given in advance ｒ and for each of the plurality of frequencies, either Equation [4] or Equation [5] is applied to calculate the amplitude C of the reflected wave. ｓ to obtain the spectrum of the reflected wave. The measuring device according to claim 2 .

4. the measurement object is made of a single material, The reflected wave is the electromagnetic wave irradiated onto the surface of the measurement object and reflected by the surface, the signal processing unit acquires a spectrum of the reflected wave from the surface of the measurement object; The measuring device according to claim 3 .

5. the measurement object is made of a first material, and an embedded object made of a second material different from the first material is embedded therein; The frequency of the electromagnetic wave is f, and the composite wave W appearing in the detection signal is ｃ is expressed by the following formula: [Equation 7] However, c ０ is the speed of light in a vacuum, C ｒ (f) is the amplitude of the stray light, C ｓ is the amplitude of the reflected wave from the surface of the measurement object, C ｍ is the amplitude of the reflected wave from the surface of the buried object, x is the distance from the optical system to the surface of the object to be measured, θ is the phase shift of the stray light relative to the electromagnetic wave emitted from the electromagnetic wave source, C ｒｍ (f, x) is the amplitude of the composite wave, θ ｍ (f, x) is the phase shift due to interference, The amplitude of the composite wave I ｍ is expressed by the following formula: [Equation 8] D(f) is expressed by the following formula: [Equation 9] Θ is expressed by the following formula: [Equation 10] cosφ is expressed by the following formula: [0011] sinφ is expressed by the following formula: [0012] Amplitude C of the reflected wave from the surface of the buried object ｍ (f) is calculated by the following formula: [0013] The signal processing unit The phase shift θ due to the interference ｍ (f, x) and the amplitude C of the reflected wave from the surface of the measurement object obtained based on the formulas [1] to [6]. ｓ and are stored in advance, The signal processing unit detects the phase shift θ due to interference, which is stored in advance. ｍ (f, x) and the amplitude C of the reflected wave from the surface of the measurement object ｓ and extracting the amplitude of the reflected wave from the buried object for each of the plurality of frequencies using equation [13] based on the above equation, thereby obtaining a spectrum of the amplitude of the reflected wave from the buried object. The measuring device according to claim 3 .

6. The amplitude C of the reflected wave from the surface of the measurement object ｓ is determined in advance by measuring the amplitude of a reflected wave from the surface of the measurement object made of the first material based on the formulas [1] to [6]. The measuring device according to claim 5 .

7. The optical system comprises: a branching means inserted in a propagation path of the electromagnetic wave, for branching the reflected wave incident on the measurement object via an outlet for emitting the electromagnetic wave to a path different from the propagation path of the electromagnetic wave; the branching means branches the electromagnetic wave into a path toward the emission port and another path different from the path toward the emission port, the stray light is generated in the optical system by the electromagnetic wave branched to the other path, The branched reflected waves interfere with the stray light, thereby outputting the composite wave.

3. The measuring device according to claim 1 or 2.

8. the optical system further includes a reflecting means for reflecting the electromagnetic wave reflected to the other path; 8. The measuring device according to claim 7.

9. Emits electromagnetic waves, an optical system that emits the electromagnetic wave to a measurement object held by a stage that can be driven along a propagation direction of the electromagnetic wave, and a wave of the electromagnetic wave reflected by the measurement object is incident on the measurement object, and a composite wave resulting from interference between the reflected wave and stray light generated by the incidence of the electromagnetic wave is emitted from a path different from the propagation path of the electromagnetic wave; Detecting the composite wave emitted from the optical system and outputting a detection signal indicating the detection result; switching the frequency of the electromagnetic wave among a plurality of frequencies, and moving the stage to a plurality of positions for each of the plurality of frequencies; measuring a spectrum of the composite wave having an intensity that depends on the frequency of the electromagnetic wave and the position of the stage in response to the detection signal, and removing the spectrum of the stray light that has been measured in advance from the spectrum of the composite wave to obtain the spectrum of the reflected wave. Measurement method.

10. a stage that can be driven along the propagation direction of the electromagnetic waves and that holds a measurement object to be irradiated with the electromagnetic waves; an optical system that emits the electromagnetic waves emitted from the electromagnetic wave source to the measurement object, receives a reflected wave of the electromagnetic wave from the measurement object, and emits a composite wave resulting from interference between the reflected wave and stray light generated by the incidence of the electromagnetic wave from a path different from the propagation path of the electromagnetic waves; and a detector that detects the intensity of the composite wave emitted from the optical system and outputs a detection signal indicative of the detection result. controlling the electromagnetic wave source to switch the frequency of the electromagnetic waves among a plurality of frequencies; controlling the stage to move to a plurality of positions for each of the plurality of frequencies; a process of measuring a spectrum of the composite wave having an intensity that depends on the frequency of the electromagnetic wave and the position of the stage in response to the detection signal; and executing a process of obtaining the spectrum of the reflected wave by removing the spectrum of the stray light obtained in advance from the spectrum of the composite wave. program.

Images