JP2006125919A - Spectral analyzer and spectral analysis method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spectral analyzer and a spectral analysis method for performing high-sensitivity measurement by using a slight amount of samples. <P>SOLUTION: This spectral analyzer 10 is equipped with photonic crystal fiber 20 for housing a gas which is a measuring object, a laser light source 12 for supplying laser light of a plurality of wavelengths toward the gas housed in the crystal fiber 20, a light detection means 13 for detecting the intensity of laser light having passed through the gas housed in the crystal fiber 20, a gas generator 15 for supplying the gas to the crystal fiber 20, and a vacuum pump unit 16 for controlling gas pressure in the crystal fiber 20. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a spectroscopic analysis apparatus and a spectroscopic analysis method, and more particularly to a spectroscopic analysis apparatus and a spectroscopic analysis method capable of performing a high-accuracy analysis of a component, concentration and molecular structure of a substance with a small amount of sample.

2. Description of the Related Art Conventionally, absorption spectroscopy for identifying a component or composition of a substance by measuring the absorption spectrum of the substance is known. As this absorption spectroscopy, there is laser spectroscopy using laser light as a light source, and a gas measurement device disclosed in Patent Document 1 is known as a measurement device using this laser spectroscopy. The gas measuring device includes a laser light source that emits laser light of a plurality of wavelengths, a hollow fiber that has a space through which the laser light from the laser light source passes, and a gas to be measured is supplied to the space. And a photodetector for receiving the laser beam that has passed through the fiber.
JP 2002-107299 A

  However, the gas measuring device is a device intended to identify a component or composition of a gas having a relatively low molecular weight such as ammonia gas, and measures a polymer, particularly a component such as a protein or a cluster component of a molecule. Insufficient for structural analysis. That is, the hollow fiber used in the gas measuring device is of a multimode type having an inner diameter of about several millimeters, and has a property of propagating light in which a plurality of different modes are mixed. For this reason, dispersion of light propagating in the fiber occurs, distortion occurs in the optical signal, the transmission distance is shortened, and a measurement requiring a long action length to obtain high sensitivity, that is, a polymer or the like There is a problem that the absorption spectrum cannot be measured satisfactorily. Moreover, since the inner diameter of the hollow fiber is on the order of several millimeters, if the optical path length is several hundred meters, a large amount of sample gas must be put into the hollow fiber. Has a problem that it cannot be measured.

  The present invention has been devised by paying attention to such a problem, and an object of the present invention is to provide a spectroscopic analysis apparatus and a spectroscopic analysis method that enable high-sensitivity measurement with a small amount of sample.

  (1) In order to achieve the above object, the present invention provides a photonic crystal fiber having a hollow core portion in which a gas to be measured is accommodated, a laser light source for irradiating the core portion with laser light having a plurality of wavelengths, And a light detecting means for detecting the intensity of the laser light that has passed through the core portion.

(2) The light detecting means receives a polarization beam splitting element that splits the laser beam that has passed through the core portion into two orthogonal polarizations, and each polarization beam separated by the polarization beam splitting element. A light receiving element,
It is preferable to adopt a configuration in which the intensity of the laser light is calculated in accordance with the magnitude of each polarization.

(3) Furthermore, a laser light source and a light detection means are provided on one end side of the photonic crystal fiber, while a laser light reflecting means is provided on the other end side of the photonic crystal fiber.
The laser light may be introduced from the one end side, reflected by the reflecting means on the other end side, and received by the light detecting means on the one end side.

  (4) Further, it is preferable to adopt a configuration in which a light refraction means made of a photonic crystal fiber is provided between the end of the photonic crystal fiber and the laser light source and / or the light detection means.

(5) Furthermore, the present invention is a spectroscopic analysis method using a photonic crystal fiber having a hollow core portion,
After the gas to be measured is accommodated in the core portion, a technique is employed in which the core portion is irradiated with laser light having a plurality of wavelengths, and the intensity of the laser light propagated through the core portion is measured for each wavelength. .

  (6) Here, the gas accommodated in the core portion may be decompressed to less than atmospheric pressure.

According to the configuration (1), since a single mode fiber including a hollow core portion is used, single mode light propagates in the fiber, and light that can be seen in a multimode fiber. Can be obtained, a long action length can be obtained, and the absorption spectrum of the substance can be measured with high sensitivity.
In addition, since the inner diameter of the core portion in which the gas is accommodated is so small that light of a single mode propagates (for example, about 10 μm), the consumption of the gas to be measured is significantly reduced. In general, accurate measurement is possible even when the amount of sample is small, such as measurement of biomedical substances.
In addition, since a fine photonic crystal fiber is used, the fiber portion can be easily deformed, can be used for various installation conditions in general, and can promote downsizing of the entire apparatus. It can be used for various measurements such as plant, medical, and environment.

  By configuring as in (2) above, even if the polarization plane of the laser beam is disturbed when passing through the fiber, the measurement error due to the polarization dependence of the sensitivity of the light detection means is reduced, and the intensity of the laser beam is reduced. Can be measured more accurately.

  According to the configuration of (3), the light action length can be doubled compared to the case where light is propagated only in one direction in the fiber, and measurement with higher sensitivity is possible.

  With the configuration (4), the separation distance between the fiber end portion and the laser light source and / or the light detection means can be shortened, and the miniaturization of the entire apparatus can be further promoted.

  The method (5) enables high-sensitivity measurement with a very small amount of sample as in the case (1).

  According to the method (6), it is possible to suppress the pressure spread of the absorption spectrum, and it is possible to identify a substance with extremely high sensitivity.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows a schematic configuration diagram of a spectroscopic analyzer according to the present embodiment. In this figure, a spectroscopic analyzer 10 includes a fiber cell 11 in which a gas to be measured is accommodated, a laser light source 12 that supplies laser light of a plurality of wavelengths toward the gas accommodated in the fiber cell 11, Photodetection means 13 for detecting the intensity of the laser light that has passed through the gas accommodated in the fiber cell 11, a gas generator 15 for supplying the gas to the fiber cell 11, and a vacuum pump unit for controlling the atmospheric pressure in the fiber cell 11. 16.

  As shown in FIGS. 1 and 2, the fiber cell 11 includes a gas introduction unit 18 connected to the gas pipe P from the gas generator 15, and a gas discharge unit 19 connected to the gas pipe P to the vacuum pump unit 16. The photonic crystal fiber 20 is provided so as to span between the gas introduction part 18 and the gas discharge part 19.

  The gas introduction unit 18 includes a block-shaped base 22 serving as an installation surface, and a main body 23 erected on the base 22. The main body 23 has a pipe 25 connected to the gas pipe P on its upper end side, a gas flow path 26 extending downward from the lower end side of the pipe 25, a gas flow path 26 and a photonic crystal fiber 20. An internal space 28 facing the end, the internal space 28 is closed from the left side in FIG. 1, a fiber holder 29 for holding the photonic crystal fiber 20, and a translucent member from the right side of the internal space 28 in FIG. And a translucent window 32 that opens to the outside with 31 interposed therebetween. The translucent member 31 allows only light transmission between the internal space 28 and the outside, while preventing gas from flowing out from the internal space 28 to the outside.

  The gas discharge part 19 has a configuration that is substantially symmetrical with the gas introduction part 18, and the same or equivalent components are denoted by the same reference numerals, and the description thereof is omitted.

  The photonic crystal fiber 20 employs a known structure in which a core portion is hollow among single mode fibers having a photonic crystal structure having a periodic refractive index structure, and detailed description thereof is omitted here. To do.

  The laser light source 12 employs a wavelength tunable laser that can selectively irradiate laser beams of various wavelengths, and the irradiation unit is disposed so as to face the light transmitting window 32 of the gas introduction unit 18. Yes. Here, the laser light emitted from the laser light source 12 is collected by the light refracting means B constituted by a lens, and then the core of the photonic crystal fiber 20 facing the inner space 28 from the light transmitting window 32. It is introduced into the part and propagates toward the gas discharge part 19.

  The light detection means 13 receives a polarized light separating element 36 that separates laser light that has passed through the core portion into vertically and horizontally polarized waves, and each polarized light separated by the polarized light separating element 36. Two light receiving elements 38, 38 and a detector 40 for detecting the intensity of the laser beam by adding the magnitudes of the respective polarizations received by the light receiving elements 38, 38 are provided.

  The polarization separation element 36 is disposed such that the light receiving portion thereof faces the light transmission window 32 of the gas discharge unit 19. For this reason, the laser beam propagating through the photonic crystal fiber 20 toward the gas discharge unit 19 is emitted from the internal space 28 of the gas discharge unit 19 to the outside through the translucent window 32 and is emitted to the outside. The laser light is split by the light refracting means B constituted by a lens, and then received by the polarization separation element 36 and separated into two directions of polarization.

  Preferably, a plurality of light detection means 13 are provided, and an error due to laser fluctuation is removed by taking a difference between the respective data.

  The gas generator 15 generates a sample gas to be measured, and supplies the sample gas to the internal space 28 of the gas introduction unit 18. The sample gas supplied to the internal space 28 passes through the core portion of the photonic crystal fiber 20, flows toward the gas discharge unit 19, and is discharged from the internal space 28 of the gas discharge unit 19 toward the vacuum pump unit 16. Is done.

  The vacuum pump unit 16 is provided so that the pressure of the sample gas passing through the photonic crystal fiber 20 can be adjusted. Here, the pressure of the sample gas is appropriately selected according to the type of the substance to be measured, but generally, it is below atmospheric pressure, and the spread of the peak of the absorption spectrum at each wavelength is within a predetermined range. It is adjusted to become.

  Next, a spectroscopic analysis method using the spectroscopic analyzer 10 will be described.

  The sample gas generated from the gas generator 15 is introduced into the gas introduction unit 18, passes through the hollow core portion of the photonic crystal fiber 20, is exhausted from the gas exhaust unit 19, and is sucked into the vacuum pump unit 16. At this time, the pressure of the sample gas is adjusted to a predetermined pressure equal to or lower than the atmospheric pressure by the operation of the vacuum pump unit 16. In this state, laser light is irradiated from the laser light source 12 toward the gas introduction unit 18, and the laser light propagates toward the gas discharge unit 19 through the core portion of the photonic crystal fiber 20 containing the sample gas. . The laser light that has passed through the photonic crystal fiber 20 is emitted from the light transmission window 32 of the gas discharge unit 19, and its intensity is detected by the light detection means 13. The above procedure is performed for each wavelength of the laser light that is changed stepwise by the laser light source 12, and the data is collected to obtain an absorption spectrum of the laser light that has passed through the sample gas.

  Therefore, according to such an embodiment, since the single-mode photonic crystal fiber 20 is used, the transmission loss of light is suppressed, a long action length is obtained, and high-sensitivity measurement is possible.

  Further, since the sample gas can be measured by accommodating the sample gas in the core portion having an inner diameter of about 10 μm, even if the length of the fiber 20 is increased to several hundred meters, the amount of the sample gas can be reduced as compared with the conventional case. In addition, accurate measurement is possible even for a substance having a small sample amount, such as biomedical.

  Next, a modification of the above embodiment will be described. In the following description, the same reference numerals are used for the same or equivalent components as in the above embodiment, and the description is omitted or simplified.

  As shown in FIG. 3, the present modification totally reflects the laser beam in place of the translucent member 31 (see FIG. 1) in the translucent window 32 of the gas discharge unit 19 in the modification. A feature is that a reflecting means 42 such as a mirror is provided, and the light detecting means 13 is disposed on the gas introduction unit 18 side.

  In the present modification, a beam splitter 44 is provided outside the light refracting means B disposed relative to the light transmission window 32 of the gas introduction unit 18. The beam splitter 44 splits the input / output light so that the laser light from the laser light source 12 propagates to the gas introduction unit 18 and the laser light from the gas introduction unit 18 propagates to the light detection means 13.

  In the above configuration, the laser light emitted from the laser light source 12 is introduced into the gas introduction unit 18 through the beam splitter 44 and the light refracting means B. The laser light propagates through the core portion in the photonic crystal fiber 20 toward the gas discharge portion 19, is reflected by the reflecting means 42, travels in the reverse direction, and returns to the gas introduction portion 18. Then, this laser light is emitted to the outside from the light transmission window 32 of the gas introduction unit 18, and is received by the polarization separation element 36 through the light refracting means B and the beam splitter 44. And the absorption spectrum of the laser beam with respect to sample gas is calculated | required similarly to the said Example.

  According to this modification, the working length of the laser beam is doubled compared to the above-described embodiment, and higher-precision measurement is possible with the same length of the fiber 20.

  In the above-described embodiments and modifications, a lens is used as the light refracting means B that condenses and separates the laser light. However, a photonic crystal fiber 20 that is shortened may be used. According to this, the separation distance between the end portion of the photonic crystal fiber 20 and the light refraction means B can be made shorter than in the case of a lens, and the downsizing of the apparatus can be further promoted.

  In the embodiment, the polarization detecting element 36 and the plurality of light receiving elements 38, 38 are provided as the light detecting means 13. However, the present invention is not limited to this, and the photonic crystal is used. If a fiber having the property of maintaining the polarization plane is used, the polarization separation element 36 can be omitted and the light receiving element 38 can be integrated.

  In addition, the configuration of each part of the apparatus in the present invention is not limited to the illustrated configuration example, and various modifications are possible as long as substantially the same operation is achieved.

The schematic block diagram of the spectroscopic analyzer which concerns on a present Example. The schematic perspective view of a fiber cell. The schematic block diagram of the spectroscopic analyzer which concerns on a modification.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Spectroanalyzer 12 Laser light source 13 Photodetection means 20 Photonic crystal fiber 36 Polarization separation element 38 Light receiving element 42 Reflection means B Photorefractive means

Claims (6)

A photonic crystal fiber having a hollow core part in which a gas to be measured is accommodated, a laser light source for irradiating the core part with laser light having a plurality of wavelengths, and light for detecting the intensity of the laser light that has passed through the core part A spectroscopic analysis device comprising a detection means. The light detection means includes a polarization separation element that separates laser light that has passed through the core portion into two orthogonal polarizations, and a light receiving element that receives each polarization separated by the polarization separation element. ,
2. The spectroscopic analyzer according to claim 1, wherein the intensity of the laser beam is calculated by combining the magnitudes of the polarized waves. On one end side of the photonic crystal fiber, a laser light source and light detection means are provided, and on the other end side of the photonic crystal fiber, laser light reflecting means is provided,
3. The spectroscopic analysis according to claim 1, wherein the laser light is introduced from the one end side, reflected by the reflecting means on the other end side, and received by the light detecting means on the one end side. apparatus. 4. A light refraction means comprising a photonic crystal fiber is provided between an end of the photonic crystal fiber and a laser light source and / or a light detection means. Spectroscopic analyzer. A spectroscopic analysis method using a photonic crystal fiber having a hollow core portion,
A spectroscopic analysis characterized in that after the gas to be measured is accommodated in the core part, laser light of a plurality of wavelengths is irradiated onto the core part, and the intensity of the laser light propagated through the core part is measured for each wavelength. Method. 6. The spectroscopic analysis method according to claim 5, wherein the gas contained in the core portion is depressurized to less than atmospheric pressure.

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