JP6091832B2 - Spectrophotometric analyzer and method - Google Patents

Description

  The present invention relates to a spectrophotometric analysis technique for analyzing a measurement sample.

  In the spectrophotometric analysis, the laser beam emitted from the oscillator is incident on the measurement sample, the wavelength is scanned, and the difference in the luminous intensity between the laser beam before the incident and the laser beam after passing through the measurement sample is measured for each wavelength. Can be analyzed.

Since the amount of laser light absorbed by the measurement sample is related to the density of the measurement sample and the absorption optical path length, if the measurement sample is dilute, increase the absorption optical path length using a multipath gas cell or resonator to increase the sensitivity. Can be secured.
In particular, a method using a resonator can secure an absorption optical path length that is several orders of magnitude larger than that of a multipath, and is therefore used for analyzing a very small amount of components (for example, Patent Document 1).

In a conventional spectrophotometric analyzer using a resonator, if a higher-order mode is included in the laser mode, unnecessary higher-order modes may resonate in the resonator. Cannot be done.
Therefore, a method is adopted in which a beam shaping optical system is used, the shape of the laser is shaped so as to approach a single transverse mode, and only the single transverse mode is resonated in the resonator.
As a prior art of the beam shaping optical system, there is a method using an anamorphic lens (for example, Patent Document 2) or a prism pair (for example, Patent Document 3).

JP 2011-220758 A Japanese Patent Laid-Open No. 10-268112 JP-A-3-39922

  The conventional spectrophotometric analyzer using a resonator has a problem that the beam shaping optical system is complicated and cannot cope with the case where the mode of the laser emitted from the oscillator is changed.

  The present invention has been made in consideration of such circumstances, and an object thereof is to provide an absorptiometric analysis technique that enables high-accuracy analysis by eliminating the detection of a high-order transverse mode with a simple configuration. .

The spectrophotometric analyzer of the present invention includes an oscillator that generates laser light with a variable wavelength, a single-mode fiber that makes the laser light emitted from the oscillator enter a single transverse mode, and a laser. A resonator that emits light after being internally reflected and then multiple-reflected, and a first luminous intensity detector that outputs a first luminous intensity detection value of a single transverse mode laser beam emitted through the resonator and the single mode fiber And a calculation unit for deriving an analysis value of the measurement sample arranged in the resonator based on the light intensity detection value of the laser light.

  The present invention provides an absorptiometric analysis technique that enables high-accuracy analysis by eliminating the detection of higher-order transverse modes with a simple configuration.

1 is a block diagram showing the entire spectrophotometric analyzer of a first embodiment of the present invention. The block diagram which shows the measurement part of the absorptiometric analyzer of 2nd Embodiment of this invention. The block diagram which attached the fiber end surface shape change means to the output end surface of the single mode fiber in the absorptiometry apparatus of 3rd Embodiment of this invention. The block diagram which shows the whole spectrophotometric analyzer of 4th Embodiment of this invention. The block diagram which performs a laser beam branching using a branch coupler in the absorptiometry apparatus of 5th Embodiment of this invention. The flowchart which shows the main routine of operation | movement of the absorptiometry apparatus which concerns on 5th Embodiment from 1st Embodiment. The flowchart which shows the subroutine of the laser irradiation measurement of operation | movement of the absorptiometry apparatus which concerns on 3rd Embodiment from 1st Embodiment. The flowchart which shows the subroutine of the laser irradiation measurement of operation | movement of the absorptiometry apparatus which concerns on 4th Embodiment and 5th Embodiment.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

(First embodiment)
As shown in FIG. 1, an absorptiometric analyzer according to the first embodiment includes an oscillator 1 that generates laser light with a variable wavelength, a laser beam emitted from the oscillator 1 and a single laser beam mode. A single mode fiber 2 that only has a transverse mode, a resonator 3 that emits laser light after being internally reflected and multiple-reflected inside, and a first of the laser light emitted through the resonator 3 and the single mode fiber 2 A first luminous intensity detector 4 for outputting a luminous intensity detection value; and an arithmetic unit 20 for deriving an analysis value of the measurement sample 5 arranged in the resonator 3 based on the first luminous intensity detection value of the laser beam. .
The oscillator 1, the single mode fiber 2, the resonator 3, and the first light intensity detector 4 are housed in one housing and constitute a measuring unit 11.

The oscillator 1 can continuously change the wavelength of the laser light, and for example, an oscillator such as an OPO laser or a diode laser can be used.
The oscillator 1 emits a laser beam having a wavelength variably designated by the condition determining unit 22.

The single mode fiber 2 is disposed between the oscillator 1 and the resonator 3 so that the component of the laser beam propagating through the inside is only a single transverse mode.
For example, a general-purpose single mode optical fiber, a dispersion shifted single mode optical fiber, a non-zero dispersion shifted single mode optical fiber, or the like is used.

The resonator 3 has a structure including a single transverse mode in its eigenmode. For example, a Fabry-Perot resonator can be used.
In order to satisfy the resonance condition, the wavelength λ of the laser light emitted from the oscillator 1 is used, and the optical path length L of the resonator 3 satisfies the relationship of the expression (1).
mλ = 2L (m: natural number) (1)

  By satisfying the relationship of the resonance conditions, the laser light incident on the resonator 3 is reflected multiple times inside the resonator 3 and then emitted to the outside.

A measurement sample 5 is arranged inside the resonator 3.
The measurement sample 5 is not particularly limited, and any sample that absorbs and transmits light can be appropriately selected regardless of the state of the substance.

  The laser beam that is multiple-reflected inside the resonator 3 has a specific wavelength absorbed by the measurement sample 5 corresponding to the component of the measurement sample 5 and its concentration, and is attenuated.

  In addition, in order to obtain the intrinsic attenuation characteristics of the multiple reflected laser beams by the resonator 3, the measurement is performed in a state (blank state) in which the measurement sample 5 is not disposed on the resonator 3.

  The first light intensity detector 4 receives laser light after propagating through the single mode fiber 2 and the resonator 3, and detects the light intensity of the incident laser light as a first light intensity detection value. For example, a photodiode or the like Can be used.

The calculation unit 20 includes a condition determination unit 22 that determines the condition of the wavelength of the laser emitted from the oscillator 1, and the first light intensity detection value detected by the first light intensity detector 4. The measurement sample 5 is disposed in the resonator 3. Luminosity measurement value storage unit 23 that stores data in a separate state (arrangement state) and a blank state, and data stored in the luminosity measurement value storage unit 23 is called for each wavelength, and the first light intensity detection of the arrangement state for each wavelength Information on the difference between the value and the first light intensity detection value in the blank state, and the difference in absorption amount for each wavelength specific to the substance necessary to specify the component of the measurement sample 5 or its concentration Is stored, and a sample analysis unit 26 that performs quantitative analysis and qualitative analysis of the measurement sample 5 based on the calculation results of the reference database 25 and the difference calculation unit 24.
The analysis result of the sample analysis unit 26 is output from the output unit 27.

  The condition determination unit 22 determines the wavelength of the laser light emitted from the oscillator 1 based on the wavelength step width Δλ, the minimum wavelength λmin, and the maximum wavelength λmax input from the input unit 21 as initial conditions.

  The photometric measurement value storage unit 23 scans the laser light from the minimum wavelength λmin to the maximum wavelength λmax in the blank state, and scans the laser light from the minimum wavelength λmin to the maximum wavelength λmax in the blank state. The first light intensity detection value acquired in this manner is stored as data.

The calculation of the difference in the difference calculation unit 24 is performed by the equation (2).
γ = (β−α) / β (2)
However, (gamma) represents the difference calculation value in each wavelength (lambda), (alpha) represents the 1st luminous intensity detection value at the time of an arrangement state, (beta) represents the 1st luminous intensity detection value at the time of a blank state, respectively.

The sample analysis unit 26 performs qualitative analysis and quantitative analysis of the measurement sample 5 based on the calculation result (equation (2)) of the difference calculation unit 24 based on the reference database 25.
As an example of the analysis, the distribution of the difference calculation value γ with respect to the incident light λ is graphed, and compared with the light absorption distribution by the wavelength of various substances prepared in advance, the component of the measurement sample 5 characterized by the absorption wavelength Qualitative analysis, such as identifying a specific component, or quantitative analysis, such as determining the concentration of a specific component by quantifying the amount of light absorbed at a specific wavelength in an already identified substance.

Next, the operation of the photoabsorption analyzer of the first embodiment will be described with reference to FIGS. 6 and 7 (refer to FIG. 1 as appropriate).
FIG. 7 shows a subroutine of the laser irradiation measurement (step S2, step S4) of FIG.
First, measurement in a blank state is performed.
As shown in the flowchart of the main routine of FIG. 6, numerical values of the wavelength step Δλ, the minimum wavelength λmin, and the maximum wavelength λmax are input from the input unit 21 to the condition determination unit 22 of the calculation unit 20 (step S1), and laser irradiation is performed. Measurement is started (step S2).

Next, laser irradiation measurement (step S2) in the blank state will be described based on a flowchart showing a subroutine of FIG.
The wavelength λ is set to the initial wavelength λmin (step S11), and laser light having the wavelength λ is emitted from the oscillator 1 (step S12).
The laser beam may include a high-order transverse mode.

The laser light emitted from the oscillator 1 first propagates through the single mode fiber 2 to become only a single transverse mode component.
And the laser beam which consists only of the single transverse mode component radiate | emitted from the end surface of the single mode fiber 2 injects into the resonator 3, and carries out multiple reflection inside the resonator 3 (step S13).

Further, the laser light emitted from the resonator 3 is detected by the first light intensity detector 4 to obtain a first light intensity detection value (step S14).
Since the measurement sample 5 is not inserted inside the resonator 3 (step S15, NO), the first light intensity detection value is stored as blank data in the light intensity measurement value storage unit 23 (step S16b). Adjustment is performed to increase the wavelength by Δλ (step S17), the measurement is repeated until the wavelength reaches the maximum wavelength λmax, and the blank data is stored (step S18, NO).
When the wavelength λ of the laser beam emitted from the oscillator 1 becomes equal to or larger than the maximum wavelength λmax (step S18, YES), the laser irradiation measurement in the blank state is finished and the process returns to the main routine (step S2).

Next, the measurement sample 5 is inserted into the resonator 3 so as to be placed (step S3), and laser irradiation measurement is started (step S4).
Even in the arrangement state, the measurement is performed in the same procedure (FIG. 7) as the laser irradiation measurement in the blank state (step S2), and therefore the description of the overlapping procedure is omitted.
However, in this case, since the measurement sample 5 is inserted into the resonator 3 (step S15, YES), the laser beam is absorbed by the measurement sample 5 when the laser beam is multiply reflected inside the resonator 3. Occurs.
Further, the light intensity detected by the first light intensity detector 4 is stored in the light intensity measurement value storage unit 23 as measurement sample data (step S16a).

  The blank data and measurement sample data stored in the photometric measurement value storage unit 23 are sent to the difference calculation unit 24, the difference is calculated (step S5), and sent to the sample analysis unit 26. The component of the measurement sample 5, its concentration, or both are analyzed using the database 25 (step S6), and the result is sent to the output unit 27 (step S7).

  According to the first embodiment, a single transverse mode can be made incident on the resonator 3 without depending on the state of the transverse mode of the laser with a simple optical system, and generation of higher order modes inside the resonator 3 is eliminated. Thus, it is possible to measure the spectrophotometry of the measurement sample 5 with high accuracy.

(Second Embodiment)
As shown in FIG. 2, the spectrophotometric analyzer of the second embodiment includes a resonator 3 instead of the single mode fiber 2 arranged between the oscillator 1 and the resonator 3 in the first embodiment of FIG. 1. A single mode fiber 6 is disposed between the first light intensity detectors 4.

2, parts having the same configuration or function as those in FIG. 1 are denoted by the same reference numerals, and redundant description is omitted.
Moreover, since the calculating part 20, the input part 21, and the output part 27 of FIG. 1 have the same structure or function, in the 2nd Embodiment, only the measurement part 11 is described and description is abbreviate | omitted.

The operation of the spectrophotometric analyzer in the second embodiment is the same as in the first embodiment, and the procedure shown in FIGS.
However, in the second embodiment, the component of the laser beam incident on the inside of the resonator 3 in step S13 of FIG. 7 includes a higher-order mode in addition to the single transverse mode.
Therefore, the higher order mode may resonate inside the resonator 3.
When the higher-order mode resonates inside the resonator 3, the laser light emitted from the resonator 3 cannot propagate through the single mode fiber 6, and therefore is not detected by the first light intensity detector 4.
Therefore, by adjusting the resonator 3 until the first light intensity detector 4 detects the laser light, the laser light incident on the resonator 3 can be narrowed down to the single transverse mode, and only the single transverse mode is used. Spectrophotometric analysis.

  As described above, according to the second embodiment, it is possible to detect only the laser beam in the single transverse mode with the first light intensity detector 4 with a simple optical system, and to perform the high-accuracy spectrophotometric measurement of the measurement sample 5. Become.

(Third embodiment)
As shown in FIG. 3, the spectrophotometric analyzer according to the third embodiment changes the shape of the end face of the single-mode fiber 2 on the emission side in addition to the configuration of the spectrophotometric analyzer according to the first embodiment of FIG. Fiber end face shape changing means 7 is provided.
The fiber end face shape changing means 7 includes, for example, a vise that can change the tightening force between the side faces of the fiber.
1 has the same configuration or function, only the measurement unit 11 of FIG. 1 is shown in FIG. 3, and these are omitted.

If the shape of the single mode fiber 2 is a perfect cylinder and the conditions such as the refractive index and temperature are completely uniform, the laser beam that propagates and exits should be in a perfect circle single mode.
However, in reality, an ideal single transverse mode may not be obtained due to irregularities in manufacturing processes, non-uniformity such as external force, or the shape of the emission end face.

  In such a case, as shown by the measurement unit 11 of Embodiment 3 of the present invention, the fiber end face shape changing means 7 is provided on the exit end face of the single mode fiber 2 to emit laser light in a more ideal state. Measurement accuracy can be improved.

The operation of the spectrophotometric analyzer of the third embodiment is the same as that of the first embodiment, and the procedure shown in FIGS.
However, compared with the first embodiment, in the third embodiment, even if the laser light propagated through the single mode fiber 2 is distorted, the shape of the laser light cross section is shaped by the fiber end face shape changing means 7. However, there is a difference in that the laser light is incident on the resonator 3 in a state close to a more perfect single transverse mode.

(Fourth embodiment)
As shown in FIG. 4, the absorptiometric analyzer according to the fourth embodiment uses the absorptiometric analyzer of FIG. 1 to obtain the second photometric detection value of the branched laser beam 12 branched from the laser beam incident on the resonator 3. A second light intensity detector 9 to be detected is provided in the measurement unit 11, and a division calculation value is obtained based on the first light intensity detection value obtained by the first light intensity detector 4 and the second light intensity detection value obtained by the second light intensity detector 9. A division calculation unit 28 for deriving.

  The beam splitter 8 branches the laser light incident on the resonator 3 and is, for example, a semi-transmissive mirror, and the branched laser light 12 is branched from the laser light emitted from the oscillator 1.

The calculation unit 20 according to the fourth embodiment is similar to the calculation unit 20 shown in FIG. 1 and includes a condition determination unit 22, a light intensity measurement value storage unit 23, a difference calculation unit 24, a reference database 25, and a sample analysis unit 26. A duplicate description is omitted.
However, the measurement unit 20 of the fourth embodiment shown in FIG. 4 is provided with a division calculation unit 28 connected to the first luminous intensity detector 4 and the second luminous intensity detector 9, and the calculation result in the division calculation unit 28 is obtained. In the point which is preserve | saved at the photometric analyzer storage part 23, it differs from the case of 1st Embodiment.

  The division operation unit 28 performs a division operation on each of the first light intensity detection value and the second light intensity detection value detected by the first light intensity detector 4 and the second light intensity detector 9 in each of the arrangement state and the blank state.

This division operation is performed by equation (3). Δ = ln (η / ζ) (3)
Here, δ represents a logarithmic division calculation value at each wavelength λ, η represents a first light intensity detection value, and ζ represents a second light intensity detection value.

  The light intensity measurement value storage unit 23 stores the calculation value δ of the division calculation unit 28 as data by distinguishing between the arrangement state and the blank state.

In the difference calculation unit 24, δ calculated in each of the arrangement state and the blank state is substituted for α and β in the above-described equation (1).
By performing the correction based on the expression (3), it is possible to eliminate the influence due to the fluctuation of the emitted laser light intensity of the oscillator 1 being measured.

Next, the operation of the absorption photometric analyzer will be described with reference to FIG. 4, FIG. 6, and FIG.
The main routine is as shown in FIG. 6 as in the first embodiment.
FIG. 8 shows a subroutine for laser irradiation in steps S2 and S4 in FIG.
8, parts having the same operations (steps S11 to S14) as those in FIG. 7 are denoted by the same reference numerals, and description thereof is omitted.

Hereinafter, the difference will be mainly described.
When the laser light emitted from the oscillator 1 passes through the single mode fiber 2 (6) and the resonator 3, a part of the laser light incident on the resonator 3 is branched by the beam splitter 8 immediately before the resonator 3, The light enters the second light intensity detector 9 (step S25).

The first light intensity detection value detected by the first light intensity detector 4 and the second light intensity detection value detected by the second light intensity detector 9 are sent to the division operation unit 28 and subjected to a division operation (step S26).
Since the measurement sample 5 is not inserted into the resonator 3 (step S27, NO), the first light intensity detection value is stored as blank data in the light intensity measurement value storage unit 23 (step S28b). Adjustment is made to increase by Δλ (step S29), the wavelength is increased until the wavelength reaches the maximum wavelength λmax, the measurement is repeated, and blank data is stored (step S30, NO).
When the wavelength λ of the laser beam emitted from the oscillator 1 becomes equal to or greater than the maximum wavelength λmax (step S30, YES), the laser irradiation measurement in the blank state is finished and the process returns to the main routine (step S2).

Next, the measurement sample 5 is inserted into the resonator 3 (step S3), and laser irradiation measurement (step S4) is started.
Since the measurement method is the same as the laser irradiation measurement in the blank state (step S2), a duplicate description is omitted.
However, in this case, since the measurement sample 5 is inserted into the resonator 3 (step S27, YES), the laser beam is absorbed by the measurement sample 5 when the laser beam is multiply reflected inside the resonator 3. This is different from step S2 in that.
Further, the light intensity detected by the first light intensity detector 4 is stored in the light intensity measurement value storage unit 23 as data of the measurement sample 5 (step S28a).

  The blank data and measurement sample data stored in the photometric measurement value storage unit 23 are sent to the difference calculation unit 24, the difference is calculated (step S5), and sent to the sample analysis unit 26. The component of the measurement sample 5, its concentration, or both are analyzed using the database 25 (step S6), and the result is sent to the output unit 27 (step S7).

(Fifth embodiment)
As shown in FIG. 5, in the absorptiometry apparatus according to the fifth embodiment, the beam splitter 8 (FIG. 4) is such that the branched laser beam 12 is branched by the branch coupler 10 attached to the single mode fiber 2. This is different from the fourth embodiment branched at.

  The branch coupler 10 is attached to the single mode fiber 2 and branches the laser light propagating through the single mode fiber 2.

  The operation in the fifth embodiment is the same as that in the fourth embodiment shown in FIG. 4, and the procedure shown in FIGS.

  According to the fifth embodiment, it is possible to perform a high-accuracy spectrophotometric measurement of the measurement sample 5 by eliminating the detection of the high-order transverse mode with a simple configuration.

  In addition, in the fourth embodiment and the fifth embodiment, the laser light incident on the resonator 3 is branched to correct the time-dependent change in the light intensity of the laser light emitted from the oscillator 1 being measured. Thus, it is possible to measure the spectrophotometer of the measurement sample 5 with high accuracy.

  According to the absorptiometry apparatus of at least one embodiment described above, the single mode fiber 2 prevents the first light intensity detector 4 from detecting unnecessary high-order mode laser light with a simple configuration. Only the laser beam in the single transverse mode is detected by the first photometric detector 4, and a more advanced analysis is possible.

Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention.
These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the scope of the invention.
These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Oscillator, 2 ... Single mode fiber, 3 ... Resonator, 4 ... 1st light intensity detector, 5 ... Measurement sample, 6 ... Single mode fiber, 7 ... End surface shape change means, 8 ... Beam splitter, 9 ... 2nd Photometric detector, 10 ... branch coupler, 11 ... measurement unit, 12 ... branched laser beam, 20 ... calculation unit, 21 ... input unit, 22 ... condition determination unit, 23 ... luminance measurement value storage unit, 24 ... difference calculation unit, 25 ... Reference database, 26 ... Sample analysis section, 27 ... Output section, 28 ... Division calculation section.

Claims (6)

An oscillator that generates laser light with a variable wavelength;
A resonator that emits the laser light after being reflected and internally reflected multiple times; and
A single mode fiber that is connected to the resonator and that transmits laser light in a single transverse mode;
A first luminous intensity detector that outputs a first luminous intensity detection value of a single transverse mode laser beam emitted through the resonator and the single mode fiber;
An absorptiometry apparatus comprising: an arithmetic unit that derives an analysis value of a measurement sample disposed in the resonator based on the first light intensity detection value. 2. The absorption spectrophotometer according to claim 1, wherein the single mode fiber is disposed between the oscillator and the resonator, or between the resonator and the first photometric detector. Photometric analyzer. The absorptiometric analyzer according to claim 1 or 2,
An absorptiometry apparatus comprising end face shape changing means for changing a shape of an end face of the single mode fiber and adjusting a cross-sectional shape of laser light output from the end face. The absorptiometric analyzer according to any one of claims 1 to 3,
A second luminous intensity detector for outputting a second luminous intensity detection value of a branched laser beam obtained by branching the laser beam incident on the resonator;
The absorptiometry apparatus, wherein the calculation unit derives the analysis value based on the first light intensity detection value and the second light intensity detection value. The spectrophotometric analyzer according to claim 4,
The absorptiometry apparatus characterized in that the branched laser light is branched by a beam splitter or a branch coupler. Generating a laser beam with a variable wavelength in an oscillator;
Emitting the laser beam after being incident and multiple reflected inside the resonator; and
And outputting a first light intensity detection value of the laser beam of a single transverse mode which has passed through the single mode fiber and the resonator for the laser beam to be transmitted to a single transverse mode,
And a step of calculating an analysis value of a measurement sample arranged in the resonator based on the first light intensity detection value.

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