JP2007271412A - Method and device for measuring lipid content - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and device for measuring lipid content capable of improving the accuracy of measurement of the lipid content contained in a measured object, such as foods. <P>SOLUTION: The method for measuring the lipid content comprises step S1 of irradiating electromagnetic waves, having the frequency of microwave to a sample (measured object), detecting the reflected waves, and measuring the amplitude and phase of the reflection coefficient with respect to the radiated electromagnetic wave of the detected electromagnetic wave, step S2 of calculating the real part and imaginary part of the reflection coefficient, based on the amplitude and phase of the measured reflective coefficient, step S3 of determining the relative dielectric constant of the sample, based on the calculated real part and the imaginary part of the reflective coefficient, and step S4 of determining the lipid content contained in the sample, based on the determined relative dielectric constant. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a lipid content measurement method and apparatus for measuring the lipid content contained in foods and the like.

  In recent years, lifestyle-related diseases such as diabetes and stroke have become serious. If this lifestyle-related disease is seen from the viewpoint of dietary habits, the background is overnutrition due to westernization of dietary habits, especially excess intake of lipids. According to a report from the Ministry of Health, Labor and Welfare, the total calorie intake in 1946 was 1903 kcal (16 g / day for fat), compared with 1930 kcal in 2002 (54.4 g / day for fat). Although the calorie intake has not changed much, it can be seen that the intake of lipid has increased significantly.

  In recent years, a remote nutrition management system for meal contents using a visual medium such as a digital camera or a mobile phone with a digital camera has attracted attention, but it is said that it is difficult to make a clear nutritional determination and the accuracy is low. In particular, it is difficult to accurately grasp the lipid content in food, and development of an instrument that can be easily measured is desired.

  Patent Document 1 discloses a technique for measuring the concentration of moisture and salt contained in food, but does not consider lipid at all.

Patent Document 2 discloses a technique for measuring the content of water contained in foods and the like, but lipids are not considered at all.
JP-A-8-105845 Japanese Patent Laid-Open No. 6-129999

  As described above, there is a conventional technique for measuring moisture and salt contained in foods and the like, but no technique for accurately measuring the lipid content is found.

  The present invention has been made to solve the above problems, and provides a lipid content measurement method and apparatus capable of improving the measurement accuracy of the lipid content contained in an object to be measured such as food. It is an object.

  In order to solve the above problems, the lipid content measurement method of the present invention irradiates an object to be measured with an electromagnetic wave having a microwave frequency, detects a reflected wave or a transmitted wave, and irradiates the detected electromagnetic wave with the detected electromagnetic wave. A first step of measuring an amplitude and a phase of a reflection coefficient or a transmission coefficient with respect to the light, and a relative dielectric constant of the object to be measured based on the amplitude and the phase of the reflection coefficient or the transmission coefficient measured by the first step And / or a second step for obtaining a dielectric loss tangent, and a third step for obtaining the content of lipid contained in the object to be measured based on the relative dielectric constant and / or the dielectric loss tangent obtained by the second step. And have.

  According to this method, the relative dielectric constant and / or dielectric loss tangent of the object to be measured is obtained based on the amplitude and phase of the measured reflection coefficient or transmission coefficient, and the measurement is performed based on the relative dielectric constant and / or dielectric loss tangent. By obtaining the content of lipid contained in the product, the measurement accuracy of the lipid content can be improved and accurate measurement can be performed.

  The second step calculates a real part and an imaginary part of the reflection coefficient or transmission coefficient based on the amplitude and phase of the reflection coefficient or transmission coefficient measured in the first step. And a fifth step of obtaining a relative permittivity and / or a dielectric loss tangent of the object to be measured based on the real part and the imaginary part of the reflection coefficient or transmission coefficient calculated in the fourth step. It may be.

  In this case, the fifth step theoretically has a complex plane with one of the real part and the imaginary part of the reflection coefficient or transmission coefficient as the vertical axis and the other as the horizontal axis with respect to the real part and the imaginary part. Corresponding to the real part and imaginary part of the reflection coefficient or transmission coefficient calculated by the fourth step using a chart prepared in advance with the calculated relative permittivity and / or scale of the dielectric loss tangent The relative dielectric constant and / or dielectric loss tangent of the object to be measured may be obtained by reading the scale of the relative dielectric constant and / or dielectric loss tangent.

  As described above, by using a chart prepared in advance, the relative dielectric constant and / or the dielectric loss tangent of the object to be measured can be easily obtained.

  In the first step, when measuring the amplitude and phase of the reflection coefficient, a reflector is disposed on the back surface of the object to be measured so that the electromagnetic wave is irradiated on the front surface of the object to be measured. Also good.

  The electromagnetic wave may have a microwave frequency of 8 GHz or more and 12 GHz or less.

  Further, the object to be measured may be food.

  Moreover, it is preferable that the shape of the object to be measured is a plate shape.

  The lipid content measurement apparatus of the present invention includes a transmitting antenna for irradiating a measurement object with electromagnetic waves, and a reflected wave reflected from the measurement object or a transmitted wave transmitted through the measurement object. Measured by the receiving antenna, a measuring unit that measures the amplitude and phase of a reflection coefficient or transmission coefficient indicating the ratio of the detected electromagnetic wave detected by the receiving antenna to the electromagnetic wave irradiated from the transmitting antenna, and measured by the measuring unit A first process for obtaining a relative dielectric constant and / or a dielectric loss tangent of the object to be measured based on an amplitude and a phase of the reflection coefficient or transmission coefficient, and the relative dielectric constant obtained by the first process and And / or a lipid content calculation unit that performs a second process for obtaining the content of the lipid contained in the object to be measured based on the dielectric loss tangent.

  According to this configuration, based on the amplitude and phase of the reflection coefficient or transmission coefficient measured by the measurement unit, the lipid content calculation unit obtains the relative permittivity and / or dielectric loss tangent of the object to be measured, and the relative dielectric constant thereof. By obtaining the lipid content contained in the object to be measured based on the rate and / or the dielectric loss tangent, the measurement accuracy of the lipid content can be improved and accurate measurement can be performed.

  In addition, the lipid content calculation unit may calculate the real part and the imaginary part of the reflection coefficient or transmission coefficient based on the amplitude and phase of the reflection coefficient or transmission coefficient measured by the measurement unit in the first process. Based on a third process to be calculated and a real part and an imaginary part of the reflection coefficient or transmission coefficient calculated by the third process, a fourth dielectric constant and / or a dielectric loss tangent of the object to be measured are obtained. And a processing unit.

  In this case, the lipid content calculation unit may be configured such that the fourth process is performed on a complex plane having one of the real part and the imaginary part of the reflection coefficient or transmission coefficient as a vertical axis and the other as a horizontal axis. The reflection coefficient or the transmission coefficient calculated by the third process is prepared using a chart prepared in advance with a scale of the relative permittivity and / or dielectric loss tangent calculated theoretically for the imaginary part. The relative permittivity and / or the dielectric loss tangent of the object to be measured may be obtained by reading the scale of the relative dielectric constant and / or the dielectric loss tangent corresponding to the real part and the imaginary part.

  As described above, in the lipid content calculation unit, by using a chart prepared in advance, the arithmetic processing for obtaining the relative dielectric constant and / or the dielectric loss tangent of the object to be measured is facilitated. Here, the chart should just be memorize | stored in the lipid content rate calculation part beforehand as data.

  The present invention has the configuration described above, and has the effect that it can provide a lipid content measurement method and apparatus capable of improving the measurement accuracy of the lipid content contained in a measurement object such as food. Play.

(Background to Invention)
In order to measure the lipid content in foods, the present inventor first considered the application of the impedance method used for measuring fat in the human body, but in the impedance method, a weak constant current was passed through the object to be measured. When measuring the voltage and determining the impedance according to Ohm's law, when the lipid content of the object to be measured becomes high, the voltage for flowing a constant current must be increased. Expected to be difficult to implement.

  Therefore, the present inventor has proposed that the impedance of microwaves (waves having a wavelength of several tens of centimeters or less) is high in a high resistance substance such as lipid compared to a low resistance substance such as highly conductive water. We considered that it would be possible to easily measure the lipid content over a wide range using microwaves by taking advantage of the opposite characteristics of the method.

-First consideration-
First, it was verified whether the lipid content could be measured using microwaves. Here, the reflection characteristics of the microwave with respect to the lipid content of the object to be measured when the object to be measured was irradiated with microwaves were considered.

  In order to investigate the characteristics of the reflected wave with respect to the lipid content (volume ratio) in the substance when the substance is irradiated with the microwave, the reflection coefficient (the microwave reflected to the irradiated microwave (incident wave)) The value representing the ratio of (reflected wave) was theoretically derived. Here, the case where the shape of the sample to be measured (the object to be measured) was made into a thin plate shape, and the two cases of the state where the back of the sample was an infinite line and the state where the back of the sample was short-circuited were studied.

[1. (When the back of the sample is an infinite line)
When a radio wave absorber is placed behind the sample, and the microwave that is incident from the front and passes through the sample is absorbed by the absorber and does not reflect (when the sample is behind an infinite line; the path through which the microwave propagates) (In the case of a state where the light spreads to infinity by the absorber). The propagation state of the microwave in this case is shown in FIG.

  When the rear side of the sample is an infinite length line, as shown in FIG. 1, the incident region (region from the antenna to the sample (air)) is the region 1, and the sample internal region (the thickness of the sample is d [m]) Is the region 2 and the region behind the sample (the region (air) in which the microwave transmitted through the sample travels in FIG. 1) is the region 3, and the traveling direction of the microwave irradiated from the antenna is taken on the z axis, and is perpendicular to the paper surface of FIG. The right direction is taken as the y-axis, and the direction perpendicular to the z-axis and the y-axis is taken as the x-axis.

  Assuming that the left side of region 1 and the right side of region 3 extend indefinitely, region 1 has an incident wave traveling from the antenna toward the sample and a reflected wave from the sample, and region 2 has a z-axis. There are a microwave propagating in the positive direction and a microwave propagating in the negative z-axis direction, and only the transmitted wave exists in the region 3. Assuming that the propagating microwave is a plane wave, the electric and magnetic fields in each region are expressed as follows.

First, the region 1 will be described. The electric field E _1i and the magnetic field H _1i of the incident wave propagating through the region 1 are expressed by the equations (1a) and (1b) of (Equation 1), and the electric field E _1r and the magnetic field H _1r of the reflected wave are expressed by the equation (2a), It is represented by (2b).

Here, ω is an angular frequency, ε ₀ is a vacuum dielectric constant, μ ₀ is a vacuum magnetic permeability, and k ₀ and η ₀ are expressed by equations (3) and (4) in (Equation 1). Further, i _x and i _y are unit vectors in the x direction and the y direction, respectively.

Next, the region 2 will be described. In region 2 (internal region of the sample), when the relative permittivity of the sample is ε _r and the dielectric loss tangent is tan δ, the electric field E _2i and the magnetic field H _2i of the wave propagating in the positive z-axis direction are expressed by the following equation (2). The electric field E _2r and the magnetic field H _2r of the wave propagating in the negative direction of the z axis are expressed by equations (6a) and (6b).

  Here, γ is a propagation constant, η is a characteristic impedance, and γ and η are expressed by equations (7) and (8) in (Equation 2).

Next, the region 3 will be described. In region 3, there is only a transmitted wave propagating in the positive direction of the z-axis that has passed through the sample, and the electric field E _3i and magnetic field H _3i of this transmitted wave are expressed by equations (9a) and (9b) It is represented by

  Next, at the boundary between the region 1 and the region 2 (Z = 0), from the boundary conditions of the electric field and the magnetic field, from the equations (1a), (2a), (5a), (6a) to the equation (10a) ) Is obtained, and equation (10b) is obtained from equations (1b), (2b), (5b), and (6b).

  Similarly, at the boundary between the region 2 and the region 3 (Z = d), the equation (11a) of (Expression 5) is obtained from the equations (5a), (6a), and (9a), and the equations (5b), (6b ), (9b) yields equation (11b).

Solving the above equations (10a), (10b), (11a), and (11b), the reflection coefficient Γ ₁ (= E _1r / E _1i ) when the back of the sample is an infinite line is 6) Equation (12a) where Γ = | Γ | e ^jargΓ is the absolute value of the reflection coefficient (hereinafter referred to as “reflection amplitude”) | Γ ₁ | and the phase of the reflection coefficient (hereinafter referred to as “reflection coefficient”). (Referred to as “reflection phase”), the equations (12b) and (12c) of argΓ ₁ are obtained.

  Here, A, α, a (a included in α), and Φ in formulas (12b) and (12c) are as shown in formulas (13) to (16) of (Equation 7), respectively.

[2. (When the back of the sample is short-circuited)
Consider a case where a metal plate is placed behind the sample and the microwave that has passed through the sample is completely reflected by the metal plate (in the case of a short circuit; the path through which the microwave propagates is shorted by the metal plate). To do. The propagation state of the microwave in this case is shown in FIG. In FIG. 2, the regions 1, 2, 3 and the x, y, and z axes are the same as in FIG.

  When the back surface of the sample is short-circuited, the wave propagating from the region 2 in the positive direction of the z-axis is completely reflected by the metal plate placed at the boundary between the region 2 and the region 3 as shown in FIG. Waves do not propagate. In addition, the electric field and magnetic field of the wave propagating to the region 1 and the region 2 are expressed by the equations (1a), (1b), (2a), (2b), (5a) as in the case of the infinite length line behind the sample. ), (5b), (6a), and (6b). At the boundary between the region 1 and the region 2 (Z = 0), the equations (10a) and (10b) are obtained from the boundary conditions of the electric and magnetic fields. Also, at the boundary between the region 2 and the region 3 (Z = d), the equation (5a), (6a) to the equation (17) is obtained from the boundary condition of the electric field.

Solving the above equations (10a), (10b), and (17), the reflection coefficient Γ ₂ (= E _1r / E _1i ) when the back surface of the sample is short-circuited becomes equation (18a) in (Equation 9). , Γ = | Γ | e ^jargΓ , Equations (18b) and (18c) of the reflection amplitude | Γ ₂ | and the reflection phase argΓ ₂ are obtained.

  However, ξ, ψ, and ζ in equations (18b) and (18c) are as shown in equations (19a), (19b), and (19c) in (Equation 10).

  Next, the reflection amplitude with respect to the volume ratio of lipid contained in the sample was obtained by simulation and by experiment for the case of the infinite line state and the case of the short circuit state, respectively.

Here, in the simulation, the sample was a mixture of lipid and red meat, and the thickness (d) of the sample was 2 mm. Moreover, the frequency of the microwave to be irradiated was set to 10 GHz. Further, the relative dielectric constant ε _r and the dielectric loss tangent tan δ of the sample were respectively expressed by the equations (20) and (21) in (Equation 11).

Here, P _fat indicates the volume ratio (%) of lipid in the sample. Ε _rfat is the relative dielectric constant of lipid, ε _rm is the relative dielectric constant of red meat, tan δ _fat is the dielectric loss tangent of lipid, and tan δ _m is the dielectric tangent of red meat. These ε _rfat , ε _rm , tan δ _fat , and tan δ _m are the relative permittivity of fat and muscle of the human body calculated by `` An Internet resource for the calculation of the Dielectric Properties of Body Tissues (ITALIAN NATIONAL RESERCH COUNCIL) ''. The values of dielectric loss tangent were used as the dielectric constant and dielectric loss tangent of lipid and red meat, respectively. In this case, ε _rfat = 4.602, ε _rm = 42.76, tan δ _fat = 0.2286, and tan δ _m = 0.4467. The vacuum dielectric constant ε ₀ is 8.854 × 10 ⁻¹² (F / m), and the vacuum magnetic permeability μ ₀ is 1.257 × 10 ⁻⁶ (H / m).

The above simulation conditions are the same for the infinite line state and the short circuit state. In the simulation in the case of an infinite line condition, the reflection amplitude (| Γ ₁ |) with respect to the volume fraction of lipid contained in the sample was obtained using the reflection amplitude equation (12b). The simulation result is shown in FIG. In the simulation in the case of a short circuit state, the reflection amplitude (| Γ ₂ |) with respect to the volume ratio of lipid contained in the sample was obtained using the reflection amplitude equation (12b). The simulation result is shown in FIG.

  Next, in the experiment, lard was used as the lipid, and chicken fillet meat, which is relatively easy to handle as lean meat and particularly low in fat, was used, and the volume ratio of lipid to the whole sample was 0, 10, 20, 40, 60, 80 , 100%, each having a thickness (d) of 2 mm. Specifically, after mixing lard and red meat uniformly with a food processor so that each of the above volume ratios, sandwiched between ethylene vinyl, thickness 2mm so that the thickness is uniform at 2mm A sample was prepared by flattening with a rolling pin from above using a frame.

  A schematic configuration of the experimental apparatus is shown in FIG. In this experimental apparatus, the microwave output from the microwave oscillator 21 is irradiated to the sample S on the sample stage 24 from the antenna 23 for both transmission and reception via the measuring device 22 which is a network analyzer. Then, the reflected wave from the sample S is input to the measuring device 22 via the antenna 23, and the measuring device 22 can output and display the reflected amplitude and the reflected phase as measured values. Specifically, the microwave oscillator 21 uses hp (Hewlett Packard) SYNTHESIZED SWEEPER (HP83630A), the measurement device 22 uses hp HP8510B vector network analyzer, and the antenna 23 uses SPC. The WR-90 X-band horn antenna (TYPE 14T007) from electronics was used.

  The experiment in the infinite line state was performed by placing a microwave absorber on the sample stage 24, placing a foamed polystyrene on it, and placing the sample S thereon. The experiment in the short-circuit state was performed by placing a foamed polystyrene on the sample stage 24, placing a metal plate thereon, and placing the sample S thereon. In both experiments, the antenna 23 was placed at a position 80 mm above the sample S so that the opening surface of the antenna 23 was horizontal, irradiated with 10 GHz microwaves, and the reflection amplitude was measured by the measuring device 22. This measurement was performed twice by preparing two samples each having a lipid volume ratio of 0, 10, 20, 40, 60, 80, and 100%. FIG. 3B shows the experimental result in the case of the infinite line state, and FIG. 4B shows the experimental result in the case of the short circuit state.

  As shown in FIG. 3 (a) and FIG. 3 (b), in both the simulation and the experiment, the reflection amplitude increases with an increase in the lipid content (lipid volume ratio) in the case of an infinite line state. After reaching the maximum, the results showed that it decreased with increasing lipid content. Also, as shown in FIGS. 4 (a) and 4 (b), in both the simulation and the experiment, in the case of a short circuit state, the reflection amplitude decreases exponentially with the increase in the lipid content, After minimizing, the results showed increasing with increasing lipid content.

  From the above, qualitatively good agreement was found between the simulation results (theoretical values) and the experimental results, indicating the validity of the theoretical study. It should be noted that the lipid content showing the maximum value of the reflection amplitude in the case of the infinite line state and the lipid content showing the minimum value of the reflection amplitude in the case of the short circuit state differed from the lipid used in the simulation and the experiment. This is probably because there was an error in the relative dielectric constant and dielectric loss tangent of each red meat. In addition, the experimental results are generally lower than the simulation results. The simulation shows that all reflected waves can be measured. This is thought to be due to the fact that all reflected waves could not be measured.

  On the other hand, in both the infinite line state and the short circuit state, the lipid content is not determined to be one for one reflection amplitude, and it is difficult to obtain the lipid content from only the reflection amplitude. Conceivable.

  In addition, the reflection amplitude when the back surface of the sample is short-circuited is larger than the reflection amplitude when the back surface of the sample is an infinite line. It is considered that it is more suitable to use the reflection amplitude at.

  Then, when the back surface of the sample was short-circuited, a method for deriving the lipid content from the reflection amplitude and the reflection phase was examined using the value of the reflection phase in addition to the reflection amplitude.

-Second examination content-
As a method for obtaining the lipid content from the measured values of the reflection amplitude and phase when the back surface of the sample is short-circuited, the relative permittivity ε _r and the dielectric loss tangent tan δ are derived from the reflection coefficient, and the volume fraction of the lipid is calculated from these values. We examined how to find it. Although the relative permittivity ε _r and the dielectric loss tangent tan δ may be derived from the measured values of the reflection amplitude and phase based on the expression of the reflection coefficient, in this case, the calculation becomes complicated. Therefore, a reflection complex plane chart with the real part and the imaginary part of the reflection coefficient as axes is created, and using this, the relative permittivity ε _r , dielectric loss tangent tan δ from the reflection coefficient (measurement value of reflection amplitude and phase) of the sample is used. It was decided to derive.

The reflection coefficient Γ _{2 when the} back surface of the sample is short-circuited is expressed by Equation (22) in (Equation 12).

Using this equation (22), when the relative dielectric constant ε _r is fixed to 1, 10, 20,..., 80 and the dielectric loss tangent tan δ is changed from 0 to 1.0, the dielectric loss tangent tan δ is set to 0, Simulation is performed for each of the sample thicknesses of 1 mm, 2 mm, and 4 mm when the relative dielectric constant ε _r is changed from 1 to 80 with 0.05, 0.1,. A complex plane chart was created by plotting on the complex plane with the real part of the coefficient on the horizontal axis and the imaginary part on the vertical axis. Theoretically, tan δ exists up to ∞, but the measurement object to be measured this time is not a high-loss object, so the graph of tan δ> 1 is omitted.

As a result of the simulation, when the sample thickness is 1 mm or 2 mm, the curve of ε _r and tan δ does not cross each other within the range of 1 ≦ ε _r ≦ 80 and 0 ≦ tan δ ≦ 1, and 1 mm at 4 mm. It was a graph in which curves intersect within the range of ≦ ε _r ≦ 80. FIG. 6 shows a reflection complex plane chart in the case where the thickness of the sample prepared by the simulation is 2 mm.

From this, the reflection amplitude and the reflection phase measured with the sample being thinned are converted into the real part (ReΓ) and the imaginary part (ImΓ) of the reflection coefficient by the equations (23) and (24) of (Equation 13). When plotted on the reflection complex plane chart in the short-circuit state, it is possible to read the relative dielectric constant ε _r and the dielectric loss tangent tan δ. In addition, the results showed that the thinner the sample thickness, the larger the change width at the higher relative dielectric constant, and the thicker the sample thickness, the larger the change width at the lower relative dielectric constant.

  However, since the created reflection complex plane chart is based on the (pure theoretical) simulation result when the measurement was ideally performed, the measurement value should be ideal when plotting the measurement value on this chart. It is necessary to correct to the value when it can be done automatically.

Next, an experiment was conducted to confirm the validity of the theoretical examination. In this experiment, a metal plate is placed at a position 80 mm from the antenna (the back of the sample is short-circuited), and after measuring the reflection amplitude and phase without the sample, the volume fraction of lipid on the metal plate The reflection amplitude and reflection phase are measured by placing a sample with a thickness of 2 mm of 0, 10, 20, 40, 60, 80, 100%, and the relative permittivity ε _r and the dielectric loss tangent are measured from the measurement result using a reflection complex plane chart. tanδ was determined.

  In this experiment, as in the previous experiment, lard was used as the lipid, and chicken breast fillet, which is relatively easy to handle as lean meat, and especially low in fat, was used, and the volume ratio of lipid to the whole sample was 0, 10, 20, Samples of 40, 60, 80, and 100% and a thickness (d) of 2 mm were prepared.

  The same experimental apparatus (FIG. 5) as the previous experiment was used as the experimental apparatus.

  First, a metal plate is placed on the sample table 24, and the antenna 23 is set so that the opening surface of the antenna 23 is horizontal at a position 80 mm above the surface of the metal plate. And the reflection amplitude and the reflection phase were measured by the measuring device 22. Next, the sample was placed on a metal plate and irradiated with 10 GHz microwave, and the reflection amplitude and the reflection phase were measured by the measuring device 22. This measurement was performed three times by preparing three samples each having a lipid volume ratio of 0, 10, 20, 40, 60, 80, and 100%.

Here, the reflection coefficient when ideal measurement can be performed is Γ (amplitude | Γ |, phase argΓ), and the reflection coefficient when a metal plate is placed on the sample surface (reference surface) is Γ _air (amplitude | Γ _air). |, Phase argΓ _air ), and if the actual measurement value is Γ _m (amplitude | Γ _m |, phase argΓ _m ), if the ideal measurement can be performed, the total squared of the absolute value of the reflection coefficient is | Γ | ² = 1, but the square of the absolute value of the reflection coefficient Γ _air received by the antenna when actually measured by placing a metal plate on the sample surface is less than 1 (| Γ _air | ² <1) Become. Therefore, the square of the absolute value of the actually measured value Γ _m | Γ _m | ² is the reflected power when the measurement is ideally performed (the true reflected power, that is, the square of the absolute value of the reflection coefficient Γ | Γ | ² ). Roh | gamma _air | ^doubled, represented by the formula (25) (equation 14). From this equation (25), equation (26) is obtained.

  In the case of complete reflection, the phase is π on the reflection surface (metal plate in this experiment). Therefore, the phase argΓ on the reference surface when this surface is used as the reference surface is expressed by Equation (27) in (Equation 15).

  As a result of correcting the reflection amplitude measured in this experiment by the equation (26), the values shown in the experimental values 1, 2, and 3 in FIG. 7 are obtained, and there is some error, but quantitative agreement with the theoretical value. It was observed.

  Regarding the reflection phase, the upper surface of the sample is used as a reference in the theoretical examination, but the thickness of the sample (dmm) is used in the experiment because the lower surface of the sample (position of 80 mm from the antenna) is used as a reference for convenience. It is necessary to add a correction for minutes. Therefore, Expression (27) becomes Expression (28) of (Equation 16). Here, λ is the wavelength of the microwave.

今回の実験において試料の厚みは2mmなので、式(28)のｄに２(mm)を代入して測定した反射位相の補正を行った結果、図８の実験値１，２，３で示される値となり、理論値との定量的な一致が見られた。

Since the thickness of the sample in this experiment is 2 mm, the result of correcting the reflection phase measured by substituting 2 (mm) for d in the equation (28) is shown by the experimental values 1, 2 and 3 in FIG. The value was quantitatively consistent with the theoretical value.

  Next, the real part and imaginary part of the reflection coefficient were calculated based on the equations (23) and (24) using the corrected reflection amplitude and reflection phase, and plotted on the reflection complex plane chart. This is shown in FIG. In FIG. 9, for example, experimental values 1, 2, and 3 plotted in the vicinity of the letters “fat 100%” indicate experimental values when the volume ratio of lipid is 100%. The same applies to other experimental values.

The values of the relative permittivity ε _r and the dielectric loss tangent tan δ are read from the positions of the experimental values 1, 2, and 3 plotted on the reflection complex plane chart, and each is plotted against the volume ratio of the lipid. The graph which shows the dielectric constant with respect to the volume ratio of the lipid of FIG. 11, and the graph which shows the dielectric loss tangent with respect to the volume ratio of the lipid of FIG. FIGS. 10 and 11 also show the theoretical values for the lipid volume ratios of ε _{r and} tan δ shown in the equations (20) and (21) of (Formula 11) together with the experimental results.

  In the theoretical values and the experimental results, as shown in FIG. 10, the relative permittivity was quantitatively in good agreement when the volume ratio of lipid was 20% to 100%. The closer it was, the larger the difference between the experimental value and the theoretical value. Further, as shown in FIG. 11, the dielectric loss tangent was also quantitatively matched although there was an error.

  Although there is a quantitative agreement between the theoretical values and the experimental results for both the dielectric constant and the dielectric loss tangent, the causes of error in the theoretical values and the experimental results are as follows: (1) The proportion of lipid was not accurate at the time of sample preparation (2) It is conceivable that there was an error in the relative dielectric constant and dielectric loss tangent of the lipid and red meat used in the simulation and experiment. In addition, the relative permittivity increases as the volume ratio of lipid decreases, but the greater the relative permittivity of the sample, the greater the difference in permittivity at the interface with air, so reflection at the surface is the main. For this reason, it is considered that the error in the surface position of the sample has a greater effect as the lipid ratio is smaller, which is the reason why the error from the theoretical value increases when the lipid ratio is less than 20%. With respect to the dielectric loss tangent, the influence of the error increases because the change width with respect to the change in the lipid ratio is small. Therefore, in order to further improve the measurement accuracy of relative permittivity and dielectric loss tangent, there is no error in the causes shown in the above (1) and (2), the thickness of the sample, the position of the antenna, etc., and a highly reproducible method. You can measure with.

  In the simulation performed in the “second examination content”, the same conditions as those in the previous “first examination content” were used for the conditions that were not particularly described.

  In the above, the relative permittivity and dielectric loss tangent of the sample changed in a system in which a plate-like sample was placed at a fixed distance from the antenna for transmitting and receiving microwaves, and a metal plate was applied to the back of the sample to make a short circuit. In this case, the variation of the reflection coefficient is theoretically derived as a reflection complex plane chart, and a method for obtaining the relative dielectric constant and dielectric loss tangent of the object to be measured is derived from the reflection coefficient measured using this chart. As a result of experiments to confirm the properties, the theoretical values and the experimental values showed a quantitative agreement. The method using the reflection complex plane chart is useful as a simple method capable of simultaneously measuring and analyzing the relative dielectric constant and the dielectric loss tangent. Therefore, if the relative permittivity and dielectric loss tangent of each component alone are known in a mixture composed of lipid and components other than lipid, the volume ratio of lipid is obtained from the reflection coefficient of the mixture by a method using this reflection complex plane chart. It is possible.

(Embodiment)
Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 12 is a flowchart showing a lipid content measurement method according to the embodiment of the present invention.

  First, in step S1, the sample (measurement object) is irradiated with microwaves (electromagnetic waves having a frequency of microwaves), the reflected waves are detected, and the amplitude and phase of the reflection coefficient are measured. In this case, it is preferable to perform measurement by placing a metal plate (reflecting plate) on the back of the sample and short-circuiting. Moreover, it is preferable that the sample has a thin plate shape with a predetermined thickness (for example, a predetermined value of 1 mm or more and less than 4 mm). The frequency of the microwave to irradiate is about 8-12 GHz, for example.

  Next, in step S2, the real part and imaginary part of the reflection coefficient are calculated based on the amplitude and phase of the reflection coefficient measured in step S1. This calculation method is as described in the above-mentioned “second examination content”.

  Next, in step S3, the relative dielectric constant of the sample is obtained based on the real part and imaginary part of the reflection coefficient calculated in step S2. Here, the relative permittivity may be obtained by calculation from the real part and the imaginary part of the reflection coefficient. Alternatively, a reflection complex plane chart as shown in FIG. 6 is prepared in advance, and the relative permittivity scale at the position where the real part and the imaginary part of the reflection coefficient calculated in step S2 are plotted on the reflection complex plane chart. The relative dielectric constant value may be obtained by reading In this case, it is only necessary that the relative permittivity scale is described in the reflection complex plane chart, and there is no need for the dielectric loss tangent scale.

  Next, in step S4, the volume ratio (lipid content ratio) of lipid contained in the sample is obtained based on the relative dielectric constant obtained in step S3. Here, for example, as in the case of calculating the theoretical value of FIG. 10, the volume ratio of the lipid may be obtained by using the above equation (20) (20).

  If the measurement error of the dielectric loss tangent of the sample can be reduced, the dielectric loss tangent is obtained instead of the relative dielectric constant in step S3, and the volume fraction of lipid is obtained based on the dielectric loss tangent in step S4. May be. Alternatively, the relative permittivity and the dielectric loss tangent may be obtained in step S3, and the lipid volume ratio may be obtained based on the relative dielectric constant and the dielectric loss tangent in step S4. In this case, an average value of the volume ratio of the lipid determined based on the relative dielectric constant and the volume ratio of the lipid determined based on the dielectric loss tangent may be set as the volume ratio of the lipid to be determined. In any case, when the dielectric loss tangent is obtained, it may be obtained by calculation from the real part and the imaginary part of the reflection coefficient as in the case of obtaining the above-mentioned relative dielectric constant, or as shown in FIG. A value of the dielectric loss tangent may be obtained by preparing a reflection complex plane chart and reading the scale of the dielectric loss tangent at the position where the real part and the imaginary part of the reflection coefficient are plotted. The reflection complex plane chart only needs to describe the scale of the target to be obtained among the relative permittivity and the dielectric loss tangent. Further, when the volume ratio of the lipid contained in the sample is obtained based on the dielectric loss tangent, for example, as in the case of calculating the theoretical value of FIG. What is necessary is just to obtain | require a volume ratio.

  When the reflection complex plane chart is not used, all of steps S2 to S4 are performed by calculation, and based on the amplitude and phase of the reflection coefficient measured in step S1, the relative permittivity and / or the dielectric loss tangent of the sample. Is determined, followed by the volume fraction of lipid.

  In the above description, the amplitude and phase of the reflection coefficient are measured, and the relative permittivity and / or dielectric loss tangent of the sample are obtained based on the measured values. Similarly, the transmission coefficient (irradiated microwave (incident The relative dielectric constant and / or dielectric loss tangent of the sample may be obtained based on the measured value.

  As described above, the relative permittivity and / or dielectric loss tangent of the sample is obtained based on the amplitude and phase of the reflection coefficient or transmission coefficient measured by irradiating the sample (measurement object) with microwaves, and the relative permittivity thereof In addition, by determining the lipid content contained in the sample based on the dielectric loss tangent, the measurement accuracy of the lipid content can be improved, and accurate measurement can be performed.

  Next, FIG. 13 is a block diagram showing the configuration of the lipid content measurement apparatus according to the embodiment of the present invention.

  The lipid content measurement apparatus includes a microwave generation unit 11, a transmission antenna 12a, a reception antenna 12b, a measurement unit 13, a lipid content calculation unit 14, and a display unit 15. The microwave generating unit 11 generates a microwave having a desired frequency, and the generated microwave is transmitted from the transmitting antenna 12a via the measuring unit 13 and irradiated to a sample (not shown). The reflected wave from the sample or the transmitted wave that has passed through the sample is detected by the receiving antenna 12b and input to the measuring unit 13.

  In the case of detecting the reflected wave, it is more compact to have a configuration in which the transmitting antenna 12a and the receiving antenna 12b are combined with one antenna as in the experimental apparatus of FIG. When transmitting a transmitted wave, the transmitting antenna 12a and the receiving antenna 12b are arranged facing each other, a sample is placed between them, and a microwave is transmitted from the transmitting antenna 12a toward the sample. The transmitted wave that has passed through the sample may be received by the receiving antenna 12b.

  The measurement unit 13 has a function of a network analyzer, and based on the electromagnetic wave (microwave) transmitted from the antenna 12a and the electromagnetic wave received by the antenna 12b, the amplitude and phase of the reflection coefficient or transmission coefficient are determined. The measured value is obtained and output to the lipid content calculation unit 14.

  The lipid content calculation unit 14 is configured by an arithmetic device such as a microcomputer, and is programmed to perform, for example, the above-described steps S2 to S4 and output the volume ratio of the lipid determined thereby to the display unit 15. Yes. Therefore, the lipid content calculation unit 14 performs processing for obtaining the relative dielectric constant and / or dielectric loss tangent of the sample based on the amplitude and phase of the reflection coefficient or transmission coefficient measured by the measurement unit 13, and subsequently, Based on the obtained relative dielectric constant and / or dielectric loss tangent, processing for obtaining a volume ratio of lipid contained in the sample is performed. Here, when using the above-described reflection complex plane chart, the data of the reflection complex plane chart is stored as a table in a memory in the arithmetic unit, for example, and reflected based on the amplitude and phase of the reflection coefficient or transmission coefficient. The real part and imaginary part of the coefficient or transmission coefficient are calculated, and the relative permittivity and / or dielectric loss tangent of the sample are read by reading the scale of the dielectric constant and / or dielectric loss tangent corresponding to the calculated real part and imaginary part from the table. You can program it to ask for.

  The display unit 15 is configured by a liquid crystal display, for example, and displays the lipid volume ratio obtained by the lipid content calculation unit 14.

  According to this configuration, the positional relationship between the sample and the antenna is determined at a predetermined position (when the reflected wave is detected and the reflection coefficient is measured as described above, and when the transmission wave is detected and the transmission coefficient is measured). If the start button (not shown) is pressed, for example, the microwave generated by the microwave generation unit 11 is transmitted from the transmission antenna 12a via the measurement unit 13 and reflected by the measurement unit 13. The amplitude or phase of the coefficient or permeability coefficient is measured, and the lipid content calculation unit 14 calculates the lipid content (lipid volume ratio) contained in the sample based on the measured values, and the calculated lipid content The rate is displayed on the display unit 15. Therefore, the lipid content measurement method described above can be automatically performed, and the lipid content can be easily measured.

  The present invention is useful as a lipid content measurement method and apparatus for measuring the lipid content contained in foods and the like.

It is a figure which shows the propagation state of the microwave which injects from the front of a sample when the back of a sample is an infinite length line state. It is a figure which shows the propagation state of the microwave which injects from the front of a sample, when the back surface of a sample is a short circuit state. (A) is a figure which shows the reflection amplitude with respect to the volume ratio of the lipid contained in the sample in the case of the infinite length line state calculated | required by simulation, (b) is the case of the infinite length line state calculated | required by experiment It is a figure which shows the reflection amplitude with respect to the volume ratio of the lipid contained in the sample of. (A) is a figure which shows the reflection amplitude with respect to the volume ratio of the lipid contained in the sample in the case of the short circuit state calculated | required by simulation, (b) is contained in the sample in the case of the short circuit state calculated | required by experiment. It is a figure which shows the reflection amplitude with respect to the volume ratio of the lipid to be. It is a figure which shows the structure of an experimental apparatus. 6 is a reflection complex plane chart showing the relationship between the real part and imaginary part of the reflection coefficient when the thickness of the sample is 2 mm and the relative dielectric constant and dielectric loss tangent of the sample. It is a figure which shows the reflection amplitude (experimental value and theoretical value) with respect to the volume ratio of the lipid contained in a sample. It is a figure which shows the reflection phase (experimental value and theoretical value) with respect to the volume ratio of the lipid contained in a sample. It is the figure which plotted the experimental value and the theoretical value on the reflective complex plane chart of FIG. It is a figure which shows the dielectric constant (experimental value and theoretical value) with respect to the volume ratio of the lipid contained in a sample. It is a figure which shows the dielectric loss tangent (experimental value and theoretical value) with respect to the volume ratio of the lipid contained in a sample. It is a flowchart which shows the lipid content rate measuring method in embodiment of this invention. It is a block diagram which shows the structure of the lipid content rate measuring apparatus in embodiment of this invention.

Explanation of symbols

11 Microwave generator 12a Transmitting antenna 12b Receiving antenna 13 Measuring unit 14 Lipid content calculating unit 15 Display unit

Claims (10)

A first step of irradiating an object to be measured with an electromagnetic wave having a microwave frequency, detecting a reflected wave or a transmitted wave, and measuring an amplitude and a phase of a reflection coefficient or a transmission coefficient of the detected electromagnetic wave with respect to the irradiated electromagnetic wave; ,
A second step of determining a relative permittivity and / or a dielectric loss tangent of the object to be measured based on the amplitude and phase of the reflection coefficient or transmission coefficient measured in the first step;
A lipid content measurement method comprising: a third step of obtaining a content rate of lipid contained in the object to be measured based on the relative dielectric constant and / or dielectric loss tangent obtained in the second step. The second step includes
A fourth step of calculating a real part and an imaginary part of the reflection coefficient or transmission coefficient based on the amplitude and phase of the reflection coefficient or transmission coefficient measured in the first step;
5. A fifth step of obtaining a relative dielectric constant and / or a dielectric loss tangent of the object to be measured based on a real part and an imaginary part of the reflection coefficient or transmission coefficient calculated in the fourth step. The method for measuring lipid content according to claim 1. The fifth step includes
The relative permittivity and / or dielectric calculated theoretically for the real part and the imaginary part on a complex plane with one of the real part and imaginary part of the reflection coefficient or transmission coefficient as the vertical axis and the other as the horizontal axis The relative permittivity and / or the dielectric tangent corresponding to the real part and the imaginary part of the reflection coefficient or transmission coefficient calculated by the fourth step using a chart prepared in advance with a tangent scale. The lipid content measurement method according to claim 2, wherein the relative permittivity and / or the dielectric loss tangent of the object to be measured is obtained by reading the scale.   The said 1st step WHEREIN: When measuring the amplitude and phase of the said reflection coefficient, a reflector is arrange | positioned to the back surface of the said to-be-measured object, The said electromagnetic wave is irradiated to the front surface of the to-be-measured object. Method for measuring lipid content of   The lipid content measurement method according to claim 1, wherein the electromagnetic wave has a microwave frequency of 8 GHz or more and 12 GHz or less.   The lipid content measurement method according to claim 1, wherein the object to be measured is food.   The lipid content measurement method according to claim 1, wherein the object to be measured has a plate shape. A transmitting antenna for irradiating the object to be measured with electromagnetic waves;
A receiving antenna for detecting a reflected wave reflected from the device under test or a transmitted wave transmitted through the device under test;
A measuring unit for measuring the amplitude and phase of a reflection coefficient or a transmission coefficient indicating a ratio of a detected electromagnetic wave detected by the receiving antenna to an electromagnetic wave irradiated from the transmitting antenna;
A first process for determining a relative permittivity and / or a dielectric loss tangent of the object to be measured based on the amplitude and phase of the reflection coefficient or transmission coefficient measured by the measurement unit, and the first process. A lipid content measurement apparatus comprising: a lipid content calculation unit that performs a second process for obtaining a lipid content contained in the measurement object based on the relative dielectric constant and / or dielectric loss tangent. In the lipid content calculation unit, the first process is:
A third process for calculating a real part and an imaginary part of the reflection coefficient or transmission coefficient based on the amplitude and phase of the reflection coefficient or transmission coefficient measured by the measurement unit;
And a fourth process for determining a relative permittivity and / or a dielectric tangent of the object to be measured based on the real part and the imaginary part of the reflection coefficient or transmission coefficient calculated by the third process. The lipid content measurement apparatus according to claim 8. In the lipid content calculation unit, the fourth process is:
The relative permittivity and / or dielectric calculated theoretically for the real part and the imaginary part on a complex plane with one of the real part and imaginary part of the reflection coefficient or transmission coefficient as the vertical axis and the other as the horizontal axis The specific permittivity and / or the dielectric tangent corresponding to the real part and the imaginary part of the reflection coefficient or transmission coefficient calculated by the third process using a chart prepared in advance with a tangent scale. The lipid content measurement apparatus according to claim 9, configured to obtain a relative dielectric constant and / or a dielectric loss tangent of the object to be measured by reading a scale.

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