JP2013088138A - Refraction factor measuring device, concentration measuring device and method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a refraction factor measuring device which is capable of measuring a refraction factor of a measuring target with high precision while being small-sized.SOLUTION: A refraction factor measuring device 1 is adopted which comprises a light guide rod 10 and a light guide rod 20 which are disposed proximately with a predetermined interval therebetween for reflecting illumination light incident from an incidence end face 11 on an inner surface and guiding the illumination light to a reflection end face 12, a photodetector 27 which detects the intensity of evanescent light incident to the light guide rod 20 by making the illumination light incident to the light guide rod 10, and a CPU 30 which calculates a change in refraction factor of a sample S disposed between the light guide rod 10 and the light guide rod 20 from a change in the intensity of the evanescent light detected by the photodetector 27.

Description

  The present invention relates to a refractive index measuring device, a concentration measuring device including the same, and a method thereof.

  2. Description of the Related Art Conventionally, a refractive index measuring device that measures the refractive index of a measurement object such as a liquid is known (see, for example, Patent Documents 1 to 3).

Japanese Patent Laid-Open No. 11-51863 JP 2005-533242 A JP 2000-146836 A

In the refractive index measuring apparatus disclosed in Patent Document 1, a sensor is placed near the boundary surface between the prism and the sample from the sample side placed on the total reflection prism, and the intensity of the evanescent wave is measured. The refractive index of is measured.
However, this refractive index measuring device has a configuration in which the sensor is brought closer from the sample side placed on the sample stage, so that the device becomes large and a small measuring device cannot be realized.

In the refractive index measuring device disclosed in Patent Document 2, the difference in refractive index from the standard sample on the sample side placed on the total reflection prism is measured.
However, since this refractive index measuring device is configured to measure the refractive index of a sample placed on a sample stage, there is a disadvantage that the device becomes large and a small measuring device cannot be realized.

In the refractive index measuring device disclosed in Patent Document 3, a thin film B having a depth equal to or less than the depth at which an evanescent wave is transmitted is attached on a known substance A, and the intensity that leaks to the substance C side from the amount of change in reflected light intensity The refractive index of the substance B is obtained by detection.
However, this refractive index measuring device has the disadvantage that the refractive index measurement accuracy is low because the amount of change in reflected light intensity is small.

  The present invention has been made in view of the above-described circumstances, and is capable of measuring the refractive index of a measurement object with high accuracy while reducing the size of the apparatus, and the concentration measurement provided with the same. An object is to provide an apparatus and a method thereof.

In order to achieve the above object, the present invention provides the following means.
According to a first aspect of the present invention, a first light guide member and a second light guide which are arranged close to each other with a predetermined interval and reflect the illumination light incident from one end surface to the other end surface by internal reflection. A light detector for detecting the intensity of evanescent light entering the second light guide member by causing illumination light to enter the member, the first light guide member, and the light detector A refractive index measuring apparatus comprising: a calculating unit that calculates a change amount of a refractive index of a sample disposed between the first light guide member and the second light guide member from a change amount of the intensity of evanescent light. It is.

  According to the first aspect of the present invention, the illumination light incident on the first light guide member reflects the inner side surface of the first light guide member and is guided to the end surface. In this case, an evanescent field is generated between the first light guide member and the second light guide member, and the evanescent field is disposed between the first light guide member and the second light guide member by the evanescent field. Evanescent light is generated in the sample. The evanescent light is incident on the second light guide member, is reflected from the inner surface of the second light guide member, is guided to the end surface, is emitted from the end surface, and is detected by the photodetector.

  In this case, since the intensity of the evanescent light changes depending on the refractive index of the sample disposed between the first light guide member and the second light guide member, the intensity of the evanescent light detected by the photodetector. The amount of change in the refractive index of the sample can be calculated from the amount of change in.

  As described above, according to the first aspect of the present invention, the amount of change in the refractive index of the sample can be calculated by the two light guide members, the one photodetector, and the calculation unit, thereby reducing the size of the apparatus. Can be achieved. Further, by calculating the amount of change in the refractive index of the sample using evanescent light, the amount of change in the refractive index of the sample can be measured with higher accuracy than in a conventional Abbe refractometer.

ここで、
Ｅ：エバネッセント光の強度
θ_１：前記第１の導光部材内における照明光の試料への入射角
ｎ_１：前記第１の導光部材および前記第２の導光部材の屈折率
ｎ_２：前記試料の屈折率
λ_０：照明光の波長
ｚ：前記第１の導光部材と前記試料との界面からの距離
ω：角振動数
ｔ：時間
Ａ，σ：所定の定数 In the above aspect, the calculation unit may calculate the amount of change in the refractive index of the sample based on the following equation from the amount of change in the intensity of the evanescent light detected by the photodetector.

here,
E: Intensity of evanescent light θ ₁ : Angle of incidence of illumination light on the sample in the first light guide member n ₁ : Refractive index of the first light guide member and the second light guide member n ₂ : Refractive index of the sample λ ₀ : wavelength of illumination light z: distance from the interface between the first light guide member and the sample ω: angular frequency t: time A, σ: predetermined constant

By doing in this way, incident angle (theta) ₁ to the sample of the illumination light in a 1st light guide member, refractive index n1 of a _1st light guide member and a 2nd light guide member, and the wavelength of illumination light When λ ₀ is known, the amount of change in the refractive index n ₂ of the sample can be calculated by measuring the amount of change in the intensity E of the evanescent light.

In the above aspect, the calculation unit may calculate the refractive index of the sample from a preset reference value of the refractive index of the sample and an amount of change in the intensity of the evanescent light detected by the photodetector. Good.
In this way, by adding or subtracting the amount of change in the refractive index of the sample calculated from the amount of change in the intensity of the evanescent light detected by the photodetector to the reference value of the refractive index of the sample set in advance. The refractive index of the sample can be calculated.

In the above aspect, an incident angle adjusting unit that adjusts an incident angle of illumination light to the first light guide member is provided, and the incident angle adjusting unit causes total reflection in the first light guide member. It is good also as adjusting the incident angle of the illumination light to a said 1st light guide member, and the said calculation part calculating the refractive index of the said sample based on the following formula | equation.
θc = arcsin (n ₂ / n ₁ )
here,
θc: Angle of incidence on the sample causing total reflection in the first light guide member n ₁ : Refractive index of the first light guide member and the second light guide member n ₂ : Refractive index of the sample

  By doing in this way, the incident angle of the illumination light to the first light guide member is adjusted so as to cause total reflection in the first light guide member, and the sample in the first light guide member at that time The refractive index of the sample can be easily calculated from the angle of incidence on and the refractive indexes of the first light guide member and the second light guide member.

In the above aspect, the other end surface may totally reflect the illumination light incident from the one end surface.
With this configuration, the illumination light incident from one end surface is repeatedly reflected by the inner surface of the first light guide member and guided to the other end surface, and reflected by the other end surface to be guided again to the one end surface. it can. By doing so, the number of total reflections at the interface between the first light guide member and the sample can be increased, and evanescent generated between the first light guide member and the second light guide member. The field strength can be increased. Thereby, the intensity of the evanescent light detected by the photodetector can be increased, and the measurement accuracy of the amount of change in the refractive index of the sample can be improved.

The said aspect WHEREIN: It is good also as providing the wavelength adjustment part which adjusts the wavelength of the illumination light entered into the said one end surface.
With this configuration, it is possible to calculate the amount of change in the refractive index of the sample for each wavelength while adjusting the wavelength of the illumination light incident on the first light guide member by the wavelength adjusting unit. The measurement accuracy of the rate change amount can be improved.

  According to a second aspect of the present invention, there is provided the above refractive index measurement device, a spectrum measurement unit that measures a wavelength spectrum of illumination light from the first light guide member, a wavelength spectrum measured by the spectrum measurement unit, and A concentration measuring apparatus comprising: an arithmetic unit that calculates the amount of change in the concentration of the sample by multivariate analysis from the amount of change in the refractive index of the sample calculated by the calculation unit.

  According to the second aspect of the present invention, the refractive index change device calculates the amount of change in the refractive index of the sample, and the spectrum measurement unit measures the wavelength spectrum of the illumination light from the first light guide member. it can. From the thus calculated wavelength spectrum and the amount of change in the refractive index of the sample, the amount of change in the concentration of the sample can be calculated by multivariate analysis by the calculation unit. By calculating the amount of change in the concentration of the sample in this way, the measurement accuracy can be improved compared to the case where the concentration is simply calculated from the refractive index of the sample.

  According to a third aspect of the present invention, illumination light is applied to one end surface of the first light guide member among the first light guide member and the second light guide member that are arranged close to each other with a predetermined interval. Is guided to the other end surface, a light detection step for detecting the intensity of evanescent light generated in the second light guide member by the light guide step, and an evanescent detected by the light detection step A refractive index measurement method comprising: calculating a change amount of a refractive index of a sample disposed between the first light guide member and the second light guide member from a change amount of light intensity. is there.

  According to a fourth aspect of the present invention, there is provided the refractive index measurement method, a spectrum measurement step of measuring a wavelength spectrum of illumination light from the first light guide member, a wavelength spectrum measured by the spectrum measurement step, and And a calculation step of calculating a change amount of the concentration of the sample by multivariate analysis from the change amount of the refractive index of the sample calculated by the calculation step.

  According to the present invention, there is an effect that the refractive index of a measurement object can be measured with high accuracy while downsizing the apparatus.

1 is an overall configuration diagram of a refractive index measuring apparatus according to a first embodiment of the present invention. It is a perspective view of the light guide rod of FIG. It is a figure explaining the propagation state of the illumination light and evanescent light in the light guide rod of FIG. It is a figure explaining the measurement principle of a refractive index. It is a figure explaining the generation principle of evanescent light. It is a list chart of each parameter and measured value in a specific example. It is a whole block diagram of the density | concentration measuring apparatus which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the process performed by CPU of FIG. It is a perspective view of the light guide rod of the density | concentration measuring apparatus which concerns on a 1st modification. It is a perspective view of the light guide rod of the density | concentration measuring apparatus which concerns on a 2nd modification. It is the elements on larger scale of the principal part of the refractive index measuring apparatus which concerns on a 3rd modification.

[First Embodiment]
Hereinafter, a refractive index measuring apparatus 1 according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 6.
As shown in FIG. 1, the refractive index measuring device 1 according to the present embodiment includes a light source 25, a wavelength adjusting device (wavelength adjusting unit) 35, a lens L 1, a mirror 15, and a light guide rod (a first rod). A light guide member 10, a light guide rod (second light guide member) 20, a lens L 2, a photodetector 27, a CPU (calculation unit) 30, a monitor 31, and a control device 38. .

  The light source 25 emits illumination light having a broadband wavelength component toward the mirror 15. On the emission optical axis of the light source 25, a wavelength adjusting device 35 to be described later, a lens L1 for condensing the illumination light from the wavelength adjusting device 35, and a part of the illumination light collected by the lens L1 are passed. A diaphragm 16 is arranged.

  The wavelength adjusting device 35 includes a filter wheel 36 disposed on the emission optical axis of the light source 25, and a rotation unit 37 that rotates the filter wheel 36 about a rotation axis along the emission optical axis of the light source 25. The filter wheel 36 includes a plurality of band pass filters (not shown) that transmit light in different wavelength bands in the circumferential direction.

  By having such a configuration, the wavelength adjusting device 35 rotates the filter wheel 36 by the rotating unit 37 based on a command from the control device 38 to be described later, so that a predetermined wavelength of the illumination light from the light source 25 is obtained. The band light is emitted toward the mirror 15.

  The diaphragm 16 is configured to pass only illumination light incident on the incident end face 11 of the light guide rod 10 at a predetermined incident angle or less out of the illumination light collected by the lens L1. More specifically, the diaphragm 16 is the illumination light that is totally reflected on the inner surface of the light guide rod 10 out of the illumination light collected by the lens L1 (that is, is guided at a critical angle or more in the light guide rod 10). Only the illumination light incident on the inner surface of the rod 10 is incident on the incident end surface 11 of the light guide rod 10.

The mirror 15 reflects the illumination light that has passed through the diaphragm 16 toward the incident end face (one end face) 11 of the light guide rod 10.
As shown in FIG. 2, the light guide rod 10 and the light guide rod 20 are arranged close to each other with a predetermined distance d therebetween.

  The light guide rod 10 is a rod-shaped rod made of, for example, glass or the like, and the illumination light incident from the incident end surface 11 is reflected on the inner surface by the inner surface, and is a reflection disposed on the other end side from the incident end surface 11. It leads to the end face (other end face) 12. The reflection end face 12 totally reflects the illumination light guided through the light guide rod 10.

  By having such a structure, the light guide rod 10 repeatedly reflects the illumination light incident from the incident end surface 11 by the inner surface of the light guide rod 10 to the reflection end surface 12 and totally reflects by the reflection end surface 12. Then, it is guided again to the incident end face 11.

  The light guide rod 20 is, for example, a rod-shaped rod made of glass or the like. As will be described later, the evanescent light generated by the evanescent field is internally reflected by the inner surface and guided to the reflection end surface 22. . The reflection end face 22 totally reflects the evanescent light guided through the light guide rod 20. The generation principle of evanescent light will be described later.

  By having such a configuration, the light guide rod 20 guides the evanescent light generated by the evanescent field to the reflection end surface 22 by repeatedly reflecting the inner surface of the light guide rod 20, as shown in FIG. The light is totally reflected by the reflection end face 22 and led to the emission end face 21.

  Further, between the light guide rod 10 and the light guide rod 20, a sample S that is a refractive index measurement target is disposed. Specifically, for example, when a biological sample is adopted as the sample S, the light guide rod 10 and the light guide rod 20 are placed in the living body in a state where the light guide rod 10 and the light guide rod 20 are spaced apart from each other. And the light incident end surface 11 of the light guide rod 10 and the light output end surface 21 of the light guide rod 20 are exposed outside the living body.

The light detector 27 is disposed on the exit optical axis of the light guide rod 20 and detects the intensity of the evanescent light from the exit end face 21 of the light guide rod 20.
In addition, a lens L <b> 2 that collects evanescent light from the light guide rod 20 is provided between the light guide rod 20 and the photodetector 27.

  The CPU 30 calculates the amount of change in the refractive index of the sample S disposed between the light guide rod 10 and the light guide rod 20 from the amount of change in the intensity of the evanescent light detected by the photodetector 27. ing.

The monitor 31 displays information such as the amount of change in the refractive index of the sample S calculated by the CPU 30 and the wavelength of illumination light that is selectively transmitted by the wavelength adjusting device 35.
The control device 38 operates the rotating unit 37 based on a command from the CPU 30 to control the wavelength of illumination light emitted from the wavelength adjusting device 35.

Here, the measurement principle of the refractive index by the refractive index measuring apparatus 1 according to the present embodiment will be described below.
As shown in FIG. 4, reflection occurs at the interface where materials having different refractive indexes are in contact. When the refractive indexes of the substances A and B are n ₁ and n ₂ , respectively, it is known that total reflection occurs at an incident angle θc of a certain angle or more when n ₁ > n ₂ . This total reflection angle is given by the following equation.
θc = arcsin (n ₂ / n ₁ )

  If the incident angle θc is equal to or greater than this angle, the reflection at the interface between the substance A and the substance B is total reflection, and the reflectance is 1. In this state, an energy flow from the substance A to the substance B does not occur, but as shown in FIG. 5, an electric field E called an evanescent field is generated on the substance B side. The electric field E attenuates exponentially with respect to the distance z from the interface between the substance A and the substance B. This electric field E is given by the following equation (see, for example, Optical Engineering Handbook p33 Asakura Shoten Kose et al.).

Here, each character in the above expression represents the following.
E: Intensity of evanescent light θ ₁ : Angle of incidence of illumination light into substance B (sample S) in substance A (light guide rod 10) n ₁ : Substance A (light guide rod 10) and substance C (light guide rod) 20) Refractive index n ₂ : Refractive index of the substance B (sample S) λ ₀ : Wavelength of illumination light z: Distance from the interface between the substance A (light guide rod 10) and the substance B (sample S) ω: Angle Frequency t: Time x: Value of x coordinate of measurement point in FIG. 4 A, σ ₀ : Predetermined constant

In the above equation, the term exp represents the attenuation of the electric field amplitude, and when the intensity at the interface is 1, it attenuates to 1 / e in the z direction at approximately the wavelength of light.
Macroscopically, there is no flow of energy, but if there is, for example, a fluorescent material in this evanescent field, the fluorescent material is excited to generate fluorescence. In addition, when the substance C having a high refractive index is placed in the evanescent field, the substance has an incident angle not less than the total reflection angle determined by the substances A and B and not more than the total reflection angle determined by the substances A and C. Energy flows again in C.

  FIG. 5 shows the above state. The interface between the substance B and the substance C is arranged at a position separated from the interface between the substance A and the substance B by a minute distance d. The arrow in the substance C simply indicates the direction of energy flow.

When the ratio of the amount of energy that flows into the substance C with respect to the amount of energy of incident light is the transmittance T, the transmittance T is determined by the refractive indexes n ₁ , n ₂ , n ₃ of the substances A, B, and C, and the substance A This is a function of the distance d from the substance C and the incident angle θ ₁ . That is, if the refractive indexes n ₁ and n _{3 of} the materials A and C, the distance d, and the incident angle θ ₁ are known, the transmittance T is a function of only n ₂ .

ただし、δは所定の定数である。 When the above principle is applied to the refractive index measuring apparatus 1 according to the present embodiment, the light guide rod 10 and the light guide rod 20 whose refractive index is known in a medium (sample S) whose refractive index is unknown are set to a predetermined wavelength or less. When the light is incident on the light guide rod 10 at a predetermined angle, the light leaking to the light guide rod 20 (evanescent light) appears as described above. By detecting the amount of change in the intensity of the evanescent light, the amount of change in the refractive index of the sample S can be known. In this embodiment, since it is not necessary to consider the change in the light intensity in the x-axis direction, δ = − (2πn ₁ x / λ ₀ ) sinθ ₁ + δ ₀ may be used. The intensity of the detected evanescent light is as follows. Can be represented.

Where δ is a predetermined constant.

Further, according to the refractive index measuring apparatus 1 according to the present embodiment, the amount of change in the refractive index of the sample S can be detected with extremely high sensitivity. The reason will be described below.
As described above, the transmittance T is a function of the refractive indexes n ₁ , n ₂ , n ₃ , the distance d, and the incident angle θ ₁ , but the value of the refractive index n ₂ is known and the fluctuation range is also When it can be assumed, each parameter n ₁ , n ₃ , d, θ ₁ that greatly changes the transmittance T due to a minute change in the refractive index n ₂ is set as a measurement condition, thereby measuring the sensitivity of the refractive index measurement. Can be high. In this case, it is necessary to satisfy n ₁ <n ₂ +0.1 and d <λ.

The above reason will be described below with specific examples.
According to the numerical calculation, when the wavelength used is 1 micron, the refractive index n ₂ of the sample S = 1.33322, and the variation width of the refractive index Δn ₂ = 0.00001, the result shown in FIG. 6 is obtained. Note that n ₂ = 1.33332 is the refractive index of the interstitial fluid (sample S), and Δn ₂ = 0.00001 is the fluctuation range of the refractive index corresponding to the change in the glucose concentration of 6 mg / dL.

The light quantity change rate ΔT / T is 0.19% and 0.04%, respectively, and is a value that can be detected by a highly accurate photodetector. The total light amount of the evanescent light can be changed by changing the area of the boundary portion of each substance, the intensity of incident light, and the like.
When this principle is applied to the present invention, the absolute value of the refractive index is not measured but the degree of change in the refractive index is measured in consideration of the error of the light guide rod spacing, the spread of the incident light beam, etc. Use as a device.

Since the Abbe refractometer, which is a commercially available general-purpose refractive index measuring instrument, has a measurement accuracy of about 0.0002, it can be seen that the sensitivity of the refractive index measuring apparatus 1 according to the present embodiment is very high.
Note that n ₁ = 1.38 is the refractive index of magnesium fluoride (MgF 2), and the development of a low refractive index material for optical devices having a refractive index of 1.3 to 1.4, which is given as a specific example, is carried out in various places. It has been broken.

  As described above, according to the refractive index measuring apparatus 1 according to the present embodiment, the illumination light incident on the light guide rod 10 reflects the inner side surface of the light guide rod 10 and is guided to the end surface. In this case, an evanescent field is generated between the light guide rod 10 and the light guide rod 20, and evanescent light is generated from the sample S disposed between the light guide rod 10 and the light guide rod 20 by the evanescent field. . The evanescent light is incident on the light guide rod 20, is reflected from the inner surface of the light guide rod 20, is guided to the end surface, and is detected by the photodetector 27.

  In this case, since the intensity of the evanescent light changes depending on the refractive index of the sample S arranged between the light guide rod 10 and the light guide rod 20, the change in the intensity of the evanescent light detected by the photodetector 27 is changed. The amount of change in the refractive index of the sample S can be calculated by the CPU 30 from the amount.

  As described above, according to the refractive index measuring apparatus 1 according to the present embodiment, the amount of change in the refractive index of the sample S can be calculated by the two light guide members, the one photodetector 27, and the CPU 30. The size of the apparatus can be reduced. In addition, by calculating the amount of change in the refractive index of the sample S using evanescent light, the amount of change in the refractive index of the sample S can be measured with higher accuracy than in a conventional Abbe refractometer.

  Further, since the light guide rod 10 includes the reflection end surface 12, the illumination light incident from the incident end surface 11 is repeatedly reflected by the inner side surface of the light guide rod 10 and guided to the reflection end surface 12, and is reflected by the reflection end surface 12. Thus, the light can be guided to the incident end face 11 again. By doing so, the number of total reflections at the interface between the light guide rod 10 and the sample S can be increased, and the intensity of the evanescent field generated between the light guide rod 10 and the light guide rod 20 can be increased. can do. Thereby, the intensity of the evanescent light detected by the photodetector 27 can be increased, and the measurement accuracy of the amount of change in the refractive index of the sample S can be improved.

  In addition, by providing the wavelength adjusting device 35 that adjusts the wavelength of the illumination light incident on the incident end face 11, the wavelength adjusting device 35 adjusts the wavelength of the illumination light incident on the light guide rod 10, and the sample S for each wavelength. The change amount of the refractive index of the sample S can be calculated, and the measurement accuracy of the change amount of the refractive index of the sample S can be improved.

  In the refractive index measuring apparatus 1 according to the present embodiment, a memory (not shown) is provided, and the CPU 30 sets the reference value of the refractive index of the sample S preset in the memory and the evanescent light detected by the photodetector 27. The refractive index of the sample S may be calculated from the amount of change in intensity.

  By doing this, the change amount of the refractive index of the sample S calculated from the change amount of the intensity of the evanescent light detected by the photodetector 27 is added to or subtracted from a preset reference value of the refractive index of the sample S. By doing so, the refractive index of the sample S can be calculated.

In addition, the refractive index measuring apparatus 1 according to the present embodiment includes an incident angle adjusting unit (not shown) that adjusts the incident angle of the illumination light to the light guide rod 10, and the incident angle adjusting unit is provided with the light guide rod 10. The incident angle of the illumination light to the light guide rod 10 may be adjusted so as to cause total internal reflection, and the CPU 30 may calculate the refractive index of the sample S based on the following equation.
θc = arcsin (n ₂ / n ₁ )
here,
θc: angle of incidence on sample S causing total reflection in light guide rod 10 n ₁ : refractive index of light guide rod 10 and light guide rod 20 n ₂ : refractive index of sample S

  By doing so, the incident angle adjusting unit adjusts the incident angle of the illumination light to the light guide rod 10 so as to cause total reflection in the light guide rod 10, and the sample in the light guide rod 10 at that time The refractive index of the sample S can be easily calculated from the incident angle to S and the refractive indexes of the light guide rod 10 and the light guide rod 20.

[Second Embodiment]
Next, a second embodiment of the present invention will be described with reference to FIGS. In the present embodiment, an example in which the refractive index measurement device 1 according to the first embodiment described above is applied to a concentration measurement device that measures, for example, a blood glucose level will be described. Hereinafter, with respect to the concentration measuring apparatus 2 of the present embodiment, description of points that are common to the refractive index measuring apparatus 1 according to the first embodiment will be omitted, and different points will be mainly described.

  As shown in FIG. 7, the concentration measuring apparatus 2 according to the present embodiment replaces the mirror 15 (see FIG. 1) in the refractive index measuring apparatus 1 according to the first embodiment with illumination light from the light guide rod 10. The half mirror 18 which permeate | transmits one part is provided. In addition to the configuration of the refractive index measurement device 1 according to the first embodiment (see FIG. 1), the concentration measurement device 2 according to the present embodiment illuminates from the light guide rod 10 that has passed through the half mirror 18. The lens L3 which condenses light, and the photodetector (spectrum measurement part) 17 which detects the illumination light condensed with the lens L3 are provided.

  The light detector 17 detects the intensity of light from the light guide rod 10 for each wavelength of illumination light selectively transmitted by the wavelength adjusting device 35. As a result, the photodetector 17 measures the wavelength spectrum of the light emitted from the incident end face 11 after being internally reflected in the light guide rod 10.

  Here, in the phenomenon of total reflection in the light guide rod 10, the total reflected light enters the outer medium side a little and is reflected, so that if the outer medium is absorbed, the influence of this influence decreases the energy of the reflected light. To do. Therefore, the spectrum of the outer medium can be obtained by variously changing the wavelength of the illumination light or by spectroscopically analyzing the reflected light. This is a spectral measurement method called attenuated total reflection (ATR).

  In the concentration measurement apparatus 2 according to the present embodiment, the CPU (calculation unit, calculation unit) 30 is calculated from the wavelength spectrum measured by the photodetector 17 and the intensity of the evanescent light measured by the photodetector 27. From the amount of change in the refractive index of the sample S, the amount of change in the concentration of the sample S is calculated by multivariate analysis.

  The flow of information processing in the above calculation is as shown in FIG. According to the concentration measuring apparatus 2 according to the present embodiment, concentration measurement of a wide range of solutes such as alcohols, saccharides, fatty acids, and polymers is possible, but here, blood glucose level measurement will be described as an example. The spectrum measurement value and the refractive index measurement value obtained by the attenuated total reflection method are finally subjected to arithmetic processing including a regression analysis method such as the PLS method to obtain a final value as a blood glucose level.

  As described above, according to the concentration measuring device 2 according to the present embodiment, the refractive index measuring device 1 according to the above-described embodiment calculates the amount of change in the refractive index of the sample S and guides it with the photodetector 17. The wavelength spectrum of the illumination light from the rod 10 can be measured. Then, from the thus calculated wavelength spectrum and the change amount of the refractive index of the sample S, the change amount of the concentration of the sample S can be calculated by the CPU 30 by multivariate analysis. By calculating the concentration of the sample S in this way, the measurement accuracy can be improved compared to the case where the concentration is simply calculated from the refractive index of the sample S.

In addition, since the concentration measuring device 2 according to the present embodiment has no movable part other than the wavelength control device 35, stable concentration measurement is possible.
In addition, since the sensitivity does not decrease even if the diameters of the light guide rod 10 and the light guide rod 20 are reduced, the light guide rod 10 and the light guide rod 20 having a small diameter are installed in the living body to reduce the substance concentration in the living body. It is possible to measure. Thereby, invasion at the time of blood glucose level measurement can be reduced.

  In the concentration measuring apparatus 2 according to this embodiment, the amount of change in the concentration of the sample S is measured from the wavelength spectrum and the amount of change in the refractive index of the sample S. By calculating the refractive index of the sample S itself, The concentration of the sample S can also be measured from the spectrum and the refractive index of the sample S.

[First Modification]
As a first modification of the concentration measuring apparatus 2 according to the second embodiment, as shown in FIG. 9, instead of the rod-shaped light guide rod 10 and the light guide rod 20, a light guide plate 10 ′ on a flat plate is used. Alternatively, the light guide plate 20 ′ may be employed. In this case, the light guide plate 10 ′ and the light guide plate 20 ′ on the flat plate are arranged to face each other with a predetermined interval.

  According to the concentration measuring apparatus of this modification having the light guide plate 10 ′ and the light guide plate 20 ′, the detection area of the evanescent light can be increased, and the measurement accuracy of the refractive index and the concentration of the sample S can be improved. Can do.

Further, in the concentration measuring apparatus of the present modification, a groove (not shown) extending in the flow direction of the interstitial fluid (sample S) is provided on at least one of the opposing surfaces of the light guide plate 10 ′ and the light guide plate 20 ′ on the flat plate. It is good also as providing.
By doing in this way, obstruction | occlusion of the interstitial liquid (sample S) between light-guide plate 10 'and light-guide plate 20' on a flat plate can be prevented, and the refractive index and density | concentration of sample S in real time can be prevented. Measurement can be performed reliably.

[Second Modification]
As a second modification of the concentration measuring apparatus 2 according to the second embodiment, a semi-columnar light guide rod is used instead of the rod-like light guide rod 10 and the light guide rod 20 as shown in FIG. 10 ″ and light guide rod 20 ″ may be employed.

  The semi-cylindrical light guide rod 10 ″ and the light guide rod 20 ″ are arranged to face each other with a predetermined interval, and the concave and convex portions formed so as to be fitted to each other on the respective facing surfaces. have. In FIG. 10, reference numeral 13 denotes a light incident spot where illumination light enters the light guide rod 10 ″, and reference numeral 23 denotes a light emission spot from which evanescent light is emitted from the light guide rod 20 ″. Yes.

  According to the concentration measuring apparatus of the present modification having the light guide rod 10 ″ and the light guide rod 20 ″, the detection area of the evanescent light is ensured while ensuring the size of the light incident spot 13 and the light exit spot 23. And the measurement accuracy of the refractive index and concentration of the sample S can be improved. In addition, the diameter of the light guide rod 10 "and the light guide rod 20" can be reduced, and the invasion during blood glucose level measurement can be reduced.

[Third Modification]
Further, as a third modification of the refractive index measuring apparatus 1 according to the first embodiment, as shown in FIG. 11, the light guide rod 10 and the light guide rod 20 are arranged so as to be shifted in the axial direction and guided. A lens L4 that condenses the evanescent light from the light guide rod 20 and a pinhole 28 that allows only the evanescent light collected by the lens L4 to pass through may be provided on the emission optical axis of the optical rod 20.

  According to the concentration measuring apparatus 2 according to the above-described embodiment, since the light guide rod 10 and the light guide rod 20 are disposed close to each other, the evanescent light from the light guide rod 20 and the illumination from the light guide rod 10 are used. It is difficult to separate light (reflected light). Therefore, the photodetector 27 may detect not only the evanescent light from the light guide rod 20 but also the illumination light from the light guide rod 10. In this case, since the illumination light from the light guide rod 10 is noise, the measurement accuracy of the refractive index of the sample S may be reduced.

  On the other hand, according to the concentration measuring apparatus according to this modification, the illumination light from the light guide rod 10 is blocked by the pinhole 28 and only the evanescent light from the light guide rod 20 is detected by the photodetector 27. Therefore, the measurement accuracy of the refractive index of the sample S can be improved.

  As mentioned above, although each embodiment of the present invention has been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment, and includes design changes and the like without departing from the gist of the present invention. . For example, you may apply this invention to embodiment which combined each said embodiment and each modification suitably.

L1, L2, L3, L4 Lens S Sample 1 Refractive index measuring device 2 Concentration measuring device 10 Light guide rod (first light guide member)
11 Incident end face (one end face)
12 Reflective end face (other end face)
15 Mirror 16 Aperture 17 Photodetector (Spectrum Measurement Unit)
18 Half mirror 20 Light guide rod (second light guide member)
21 emission end surface 22 reflection end surface 25 light source 27 photodetector 30 CPU (calculation unit, calculation unit)
31 Monitor 35 Wavelength tuning device (wavelength tuning unit)
38 Control device

Claims (9)

A first light guide member and a second light guide member, which are arranged close to each other with a predetermined interval and reflect the illumination light incident from one end surface to the other end surface by internal reflection;
A photodetector for detecting the intensity of evanescent light entering the second light guide member by causing illumination light to enter the first light guide member;
Calculation for calculating the amount of change in the refractive index of the sample disposed between the first light guide member and the second light guide member from the amount of change in the intensity of the evanescent light detected by the photodetector. And a refractive index measuring device. The refractive index measurement apparatus according to claim 1, wherein the calculation unit calculates the amount of change in the refractive index of the sample based on the following equation from the amount of change in the intensity of the evanescent light detected by the photodetector.

here,
E: Intensity of evanescent light θ ₁ : Angle of incidence of illumination light on the sample in the first light guide member n ₁ : Refractive index of the first light guide member and the second light guide member n ₂ : Refractive index of the sample λ ₀ : wavelength of illumination light z: distance from the interface between the first light guide member and the sample ω: angular frequency t: time A, σ: predetermined constant   The calculation unit calculates the refractive index of the sample from a preset reference value of the refractive index of the sample and an amount of change in the intensity of the evanescent light detected by the photodetector. The refractive index measuring apparatus as described in 2. An incident angle adjusting unit that adjusts an incident angle of illumination light to the first light guide member;
The incident angle adjusting unit adjusts the incident angle of the illumination light to the first light guide member so as to cause total reflection in the first light guide member;
The refractive index measurement apparatus according to claim 1, wherein the calculation unit calculates a refractive index of the sample based on the following expression.
θc = arcsin (n ₂ / n ₁ )
here,
θc: Angle of incidence on the sample causing total reflection in the first light guide member n ₁ : Refractive index of the first light guide member and the second light guide member n ₂ : Refractive index of the sample   The refractive index measuring device according to any one of claims 1 to 4, wherein the other end surface totally reflects illumination light incident from the one end surface.   The refractive index measuring apparatus according to any one of claims 1 to 5, further comprising a wavelength adjusting unit that adjusts a wavelength of illumination light incident on the one end surface. Refractive index measuring device according to claim 6,
A spectrum measuring unit for measuring a wavelength spectrum of illumination light from the first light guide member;
A concentration measuring apparatus comprising: an arithmetic unit that calculates a change amount of the concentration of the sample by multivariate analysis from the wavelength spectrum measured by the spectrum measuring unit and the change amount of the refractive index of the sample calculated by the calculating unit. . Of the first light guide member and the second light guide member that are arranged close to each other with a predetermined interval, the light guide is introduced to one end surface of the first light guide member and guided to the other end surface. Light step,
A light detection step of detecting the intensity of evanescent light generated in the second light guide member by the light guide step;
Calculation for calculating the amount of change in the refractive index of the sample disposed between the first light guide member and the second light guide member from the amount of change in the intensity of the evanescent light detected in the light detection step. And a refractive index measurement method. Refractive index measurement method according to claim 8,
A spectrum measuring step for measuring a wavelength spectrum of illumination light from the first light guide member;
A concentration measurement method comprising: calculating a change amount of the concentration of the sample by multivariate analysis from the wavelength spectrum measured by the spectrum measurement step and the change amount of the refractive index of the sample calculated by the calculation step. .

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