Calibration device for spectrometer and calibration method

Abstract

To provide a calibration device and calibration method for a spectrometer that make it possible to prevent unevenness in spectroscopic characteristics between different spectrometers from occurring for the same measurement object.SOLUTION: The calibration device comprises: a reference light source 2 for irradiating a spectrometer 10 being calibrated with reference light of prescribed light intensity; a dimming unit 3 located between the reference light source 2 and the spectrometer 10 being calibrated, and capable of attenuating light entering the spectrometer 10 being calibrated from the reference light source 2 and changing transmissivity; a power meter 4 for measuring the light intensity of the specific wavelength of light attenuated by the dimming unit 3; and a calibration unit 6 for calibrating the light reception sensitivity of each element of the spectrometer 10 being calibrated. When the transmissivity of the dimming unit 3 is changed, the calibration unit 6 acquires, for each different transmissivity, the count value per wavelength measured by the spectrometer 10 being calibrated with respect to the reference light, thereby establishing a relational expression representing the relationship between the transmissivity and the count value and calibrating the light reception sensitivity of each element of the spectrometer 10 being calibrated on the basis of the relational expression.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a calibration device and a calibration method for a spectrometer. [Background technology]

[0002] Patent Document 1 discloses a spectroscopic measurement device that includes a light irradiation unit that irradiates a mounting surface on which an object to be measured is placed with broadband light from a light source via a light guide, and a light detection unit that detects the light that has passed through the object to be measured and is incident on a spectroscope via an optical fiber, and measures the spectroscopic characteristics using the spectroscope. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7270582 Summary of the Invention [Problem to be solved by the invention]

[0004] However, it is known that there are individual differences among spectroscopes such as those included in the spectroscopic measurement device described in Patent Document 1, and that variations occur in the light-receiving sensitivity of each element between the spectroscopes used. If there is variation in the light-receiving sensitivity of each element between different spectroscopes, variations occur in the spectral characteristics measured for the same measurement object between those different spectroscopes.

[0005] The present invention has been made in consideration of the above-mentioned circumstances, and aims to provide a spectrometer calibration device and calibration method that can prevent variations in the spectroscopic characteristics measured for the same measurement target between different spectrometers. [Means for solving the problem]

[0006] The spectrometer calibration device of the present invention is a spectrometer calibration device that measures light intensity, which is the intensity of incident light, for each wavelength, and includes: a reference light source that irradiates a spectrometer to be calibrated with reference light of a predetermined light intensity; an attenuation unit that is provided between the reference light source and the spectrometer to be calibrated and is capable of attenuating light incident from the reference light source to the spectrometer to be calibrated and changing transmittance; a light intensity detection unit that measures the light intensity of a specific wavelength of light attenuated by the attenuation unit; and a calibration unit that calibrates the light receiving sensitivity of each element of the spectrometer to be calibrated.The calibration unit is configured to, when the transmittance of the attenuation unit is changed, obtain count values ​​for each wavelength measured by the spectrometer to be calibrated for the reference light for each different transmittance, thereby determining a relational equation that represents the relationship between the transmittance and the count value, and calibrate the light receiving sensitivity of each element of the spectrometer to be calibrated based on the relational equation.

[0007] With this configuration, when the transmittance of the attenuation section is changed, the spectrometer calibration device of the present invention obtains the count value for each wavelength measured by the spectrometer to be calibrated for the reference light for each different transmittance, thereby determining a relational equation that represents the relationship between the transmittance and the count value, and calibrates the light receiving sensitivity of each element of the spectrometer to be calibrated based on this relational equation, thereby preventing variations in the spectral characteristics measured for the same measurement object between different spectrometers.

[0008] In the spectrometer calibration device according to the present invention, it is preferable that the calibration unit obtains, for each different transmittance, an average value of count values ​​for each wavelength measured a predetermined number of times by the spectrometer to be calibrated with respect to the reference light, as the count value for each wavelength.

[0009] With this configuration, the spectrometer calibration device of the present invention obtains, for each different transmittance, the average value of the count values ​​for each wavelength measured a predetermined number of times by the spectrometer to be calibrated against the reference light, as the count value for each wavelength, thereby suppressing the influence of errors on the measured count values.

[0010] In the spectrometer calibration device according to the present invention, it is preferable that the attenuation section has a plurality of ND filters each having a different optical density, and the transmittance of the attenuation section is changed by changing the combination of the plurality of ND filters.

[0011] With this configuration, the spectrometer calibration device according to the present invention is configured such that the attenuation section has a plurality of ND filters each having a different optical density, and the transmittance of the attenuation section is changed by changing the combination of the plurality of ND filters, so that light incident from the reference light source to the spectrometer to be calibrated can be attenuated at different transmittances with a simple configuration.Furthermore, by changing the transmittance of the attenuation section while keeping the light intensity of the reference light source fixed, the light intensity of the light incident on the spectrometer to be calibrated can be physically changed, so that variation in the light intensity of the light incident on the spectrometer to be calibrated can be prevented.

[0012] In the spectrometer calibration device according to the present invention, it is preferable that the relational expression is stored in a storage unit of the spectrometer to be calibrated.

[0013] With this configuration, the spectrometer calibration device according to the present invention stores the relational equation in a memory unit of the spectrometer to be calibrated, and therefore can output calibrated values ​​in the spectrometer to be calibrated.

[0014] The method for calibrating a spectrometer according to the present invention is a method for calibrating a spectrometer in a calibration device that includes: a reference light source that irradiates a spectrometer to be calibrated with reference light of a predetermined light intensity; an attenuation unit that is arranged between the reference light source and the spectrometer to be calibrated and that is capable of attenuating light incident from the reference light source to the spectrometer to be calibrated and changing the transmittance; a light intensity detection unit that measures the light intensity of a specific wavelength of light attenuated by the attenuation unit; and a calibration unit that calibrates the light receiving sensitivity of each element of the spectrometer to be calibrated, wherein when the transmittance of the attenuation unit is changed, the calibration unit obtains count values ​​for each wavelength measured by the spectrometer to be calibrated for the reference light for each different transmittance, thereby determining a relational equation that represents the relationship between the transmittance and the count value, and calibrates the light receiving sensitivity of each element of the spectrometer to be calibrated based on the relational equation.

[0015] According to the spectrometer calibration method of the present invention, when the transmittance of the attenuation section is changed, the count value for each wavelength measured by the spectrometer to be calibrated for the reference light is obtained for each different transmittance, thereby obtaining a relational equation that expresses the relationship between the transmittance and the count value, and the light receiving sensitivity of each element of the spectrometer to be calibrated is calibrated based on this relational equation, thereby preventing variations in the spectral characteristics measured for the same measurement object between different spectrometers. [Effects of the Invention]

[0016] According to the present invention, it is possible to provide a spectrometer calibration device and calibration method that can prevent variations in the spectroscopic characteristics measured for the same measurement object between different spectrometers. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a schematic diagram of a spectrometer calibration device according to one embodiment of the present invention. [Figure 2] FIG. 2 is an example of a graph showing the relationship between the count value measured by a spectrometer to be calibrated and the transmittance according to one embodiment of the present invention. [Figure 3] FIG. 3 is a diagram showing an example of a case where calibration is performed between different spectrometers. [Figure 4] FIG. 4 is an example of a graph showing the relationship between the count value measured by the calibrated spectrometer and the corrected value. DETAILED DESCRIPTION OF THE INVENTION

[0018] Hereinafter, a spectrometer calibration device according to one embodiment of the present invention will be described with reference to the drawings.

[0019] (Configuration of calibration equipment) As shown in FIG. 1, the spectrometer calibration device 1 according to this embodiment includes a reference light source 2, an attenuation unit 3, a power meter 4 as a light intensity detection unit, a bandpass filter 5, and a data acquisition PC 6 as a calibration unit.

[0020] The reference light source 2 is configured by a light source capable of emitting light including a wide band of wavelengths, such as a white light source, and is configured to irradiate the spectrometer 10 to be calibrated with reference light of a predetermined light intensity.

[0021] The predetermined light intensity is preferably a relatively large light intensity, for example, the maximum light intensity, taking into consideration that the light will be attenuated by the attenuation unit 3 described below. If the light intensity of the reference light source 2 is adjusted by a dial, the predetermined light intensity can be reproduced by simply returning the dial to the maximum position even if the position is shifted. Note that the predetermined light intensity does not have to be the maximum light intensity, as long as the reference light source 2 is capable of fixing the light intensity and is capable of reproducing that light intensity.

[0022] The light attenuating section 3 is provided between the reference light source 2 and the spectroscope 10 to be calibrated, and is configured to attenuate the light incident from the reference light source 2 to the spectroscope 10 to be calibrated.

[0023] The light attenuation unit 3 has a plurality of ND filters 31 each having a different optical density (OD value), and by changing the combination, or overlapping, of these plurality of ND filters 31, it is possible to change the optical density (OD value) of the combined ND filters 31. This makes it possible for the light attenuation unit 3 to change the transmittance in the light attenuation unit 3.

[0024] The light attenuation unit 3 may have, for example, two disks on which a plurality of ND filters 31 with different optical densities (OD values) are arranged in a circle, and a mechanism that can change the combination of ND filters 31 by rotating these two disks. Note that the configuration that can change the combination of ND filters 31 is not limited to the case where adjustment is made in two stages like the two disks described above, but may also be a configuration that adjusts in three or more stages.

[0025] The reference light emitted from the reference light source 2 is attenuated according to the transmittance of the light attenuating unit 3. The light attenuating unit 3 can change the light intensity of the reference light by changing the transmittance.

[0026] The power meter 4 measures the light intensity of a specific wavelength of light attenuated by the light attenuation unit 3. In this embodiment, a power meter for light of a single wavelength is used as the power meter 4.

[0027] The bandpass filter 5 is provided between the attenuation unit 3 and the power meter 4, and limits the wavelength band of light traveling from the attenuation unit 3 to the power meter 4. Specifically, the bandpass filter 5 transmits light of a specific wavelength that can be measured by the power meter 4, and cuts out other light.

[0028] Here, an optical system (not shown) is provided between the attenuation unit 3 and the bandpass filter 5 to split the light that has passed through the attenuation unit 3 to the bandpass filter 5 side and the spectrometer 10 side that is the object of calibration.

[0029] The spectrometer 10 to be calibrated is connected between the attenuation unit 3 and the data acquisition PC 6. As a result, light attenuated by the attenuation unit 3 is incident on the spectrometer 10 to be calibrated.

[0030] The data acquisition PC 6 is connected to the spectrometer 10 to be calibrated, and is configured to input a count value corresponding to the light intensity measured from the spectrometer 10 to be calibrated.

[0031] When the transmittance of the attenuation unit 3 is changed, the data acquisition PC 6 acquires count values ​​for each wavelength measured by the spectrometer 10 to be calibrated with respect to the reference light for each different transmittance, thereby determining a relational expression that expresses the relationship between the transmittance and the count values, and calibrates the light receiving sensitivity of each element of the spectrometer 10 to be calibrated based on this relational expression. This will be specifically described in the calibration procedure below.

[0032] (Calibration procedure) First, the transmittance in the light-reducing unit 3 is set to 100%, that is, the optical density (OD value) in combination with the ND filter 31 is set to 0.0 (no ND filter).

[0033] Second, the power supply of the reference light source 2 is turned on and the light intensity is set to maximum. After this, the light intensity of the reference light source 2 is not adjusted.

[0034] Third, the light intensity measured by the power meter 4 for an optical density (OD value) of 0.0 is recorded as P0 in the data acquisition PC 6. This recording may be performed, for example, by connecting the power meter 4 and the data acquisition PC 6 and inputting the data from the power meter 4 to the data acquisition PC 6.

[0035] Fourth, for an optical density (OD value) of 0.0, measurements are performed a predetermined number of times (for example, 100 times) using the spectrometer 10 to be calibrated, and the data acquisition PC 6 calculates the average value of the count values ​​for each wavelength measured the predetermined number of times. The average value of the count values ​​calculated at this time for each wavelength is defined as C0(λ).

[0036] Fifth, the transmittance in the light attenuation unit 3 is changed, that is, the optical density (OD value) resulting from the combination of the ND filters 31 is changed to another value. In other words, the combination of the ND filters 31 in the light attenuation unit 3 is changed.

[0037] Sixth, the third and fourth steps are repeated for the changed optical density (OD value). At this time, the light intensity measured by the power meter 4 for the changed optical density (OD value) is expressed as P ODThe average value of the count values ​​for each wavelength measured a predetermined number of times by the spectrometer 10 to be calibrated for the changed optical density (OD value) is recorded in the data acquisition PC 6 as C OD Let (λ).

[0038] The fifth and sixth steps described above are performed by changing the optical density (OD value) of the ND filter 31 combination to, for example, "0.3," "0.4," "0.5," "0.6," "0.7," "0.8," "0.9," "1.0," "1.3," "1.4," "1.5," and "2.0." The optical densities (OD values) to be changed are merely examples and are not intended to be limiting.

[0039] Seventh, the data acquisition PC 6 acquires the light intensities P OD and the light intensity P0 obtained in the third step, the transmittance T OD is calculated using the following equation (1).

[0040]

number

[0041] In this embodiment, the transmittance T OD The light intensity P used to calculate OD and light intensity P0 is the light intensity of a specific wavelength that can be measured by the power meter 4. Here, in this embodiment, by using the ND filter 31 with constant transmittance characteristics, it can be estimated that wavelength bands other than the specific wavelength also have approximately the same transmittance.

[0042] Eighth, the data acquisition PC 6 uses the data obtained in the fourth to seventh steps to plot the transmittance T OD , the vertical axis is the count value C OD The graph shown in Figure 2 is created by dividing the transmittance T OD and count value C ODThe relationship between the wavelength and the optical fiber (λ) is graphed. The graph shown in Fig. 2 is created for each wavelength. Note that the graph in Fig. 2 is an example and is not intended to be limiting.

[0043] Ninth, the data acquisition PC 6 performs polynomial approximation on the graph created in the eighth step above, and calculates the coefficient "A n In this case, n should be a value that can adequately approximate the target graph, for example, a value between 2 and 4.

[0044]

number

[0045] In the ninth step, the coefficient "A n (λ)” is calculated, and the count value C OD (λ) and transmittance T OD It was possible to obtain a correspondence between the polynomials. The polynomial obtained in the ninth step is stored as a correction formula in the storage unit of the data acquisition PC 6. In this case, the data acquisition PC 6 is used as a dedicated computer connected to a spectroscopic measurement device that uses the spectrometer 10 to be calibrated. Note that the polynomial may also be stored as a correction formula in a dedicated computer, different from the data acquisition PC 6, that is connected to a spectroscopic measurement device that uses the spectrometer 10 to be calibrated.

[0046] Next, the spectrometer 10 to be calibrated is replaced with another spectrometer, and the above-described steps 1 to 9 are performed on the replaced spectrometer. The coefficient "B" of the polynomial obtained by polynomial approximation is also used for the replaced spectrometer. n (λ)" and calculate the count value C for each wavelength. OD (λ) and transmittance T OD We will respond with the following.

[0047] This gives the coefficient of the polynomial "A n (λ) and the coefficient B nThe two spectrometers that have calculated "λ (λ)" can measure the same value for the same input. If there are other spectrometers in question, replace the spectrometers in turn and repeat steps 1 to 9 above for the replaced spectrometers.

[0048] (Proofreading example) Next, with reference to FIGS. 3 and 4, calibration by the calibration device 1 of this embodiment will be described taking as an example a case where calibration is performed between spectroscope A and spectroscope B. FIG.

[0049] It is assumed that the calibration of spectrometer A and spectrometer B has been completed by the above-mentioned steps 1 to 9, that is, the correction formulas have been obtained.

[0050] 3, it is assumed that light with optical power, that is, light intensity P(λ), is incident from a light source on each of spectrometers A and B. Here, the light intensity of a specific wavelength will be described as an example.

[0051] In spectrometer A, the count value C is calculated for the light intensity P(λ). A In the spectrometer B, the count value C is obtained for the light intensity P(λ). B (λ) is obtained.

[0052] Spectrometer A count value C A (λ) and the count value C of spectrometer B B (λ) is substituted into each correction formula. As a result, the same corrected values ​​can be obtained for both spectrometer A and spectrometer B, as shown in Figure 4.

[0053] Examples of the corrected value include values ​​that can be converted into each other, such as transmittance, light intensity, or corrected count value.

[0054] (Action and effect) As described above, when the transmittance of the attenuation unit 3 is changed, the spectrometer calibration device of this embodiment creates a graph showing the relationship between transmittance and count value by obtaining the count value for each wavelength measured by the spectrometer 10 to be calibrated for the reference light for each different transmittance, performs polynomial approximation on the graph to obtain a polynomial as a relational equation, and calibrates the light receiving sensitivity of each element of the spectrometer 10 to be calibrated based on this polynomial as a correction equation, thereby preventing variations in the spectral characteristics measured for the same measurement object between different spectrometers.

[0055] Furthermore, the spectrometer calibration device of this embodiment obtains the average count value for each wavelength measured a predetermined number of times by the spectrometer 10 to be calibrated against the reference light for each different transmittance, thereby reducing the influence of errors on the measured count value.

[0056] Furthermore, in the spectrometer calibration device according to this embodiment, the attenuation unit 3 has a plurality of ND filters 31 each having a different optical density, and the transmittance of the attenuation unit 3 is changed by changing the combination of the plurality of ND filters 31, so that with a simple configuration, it is possible to attenuate light incident from the reference light source 2 to the spectrometer 10 to be calibrated at different transmittances. Furthermore, by changing the transmittance of the attenuation unit 3 while keeping the light intensity of the reference light source 2 fixed, it is possible to physically change the light intensity of the light incident on the spectrometer 10 to be calibrated, thereby preventing variations in the light intensity of the light incident on the spectrometer 10 to be calibrated.

[0057] (Variation) In the present embodiment, an example has been described in which the polynomial obtained in the ninth step is stored as a correction formula in the storage unit of the data acquisition PC 6, but this is not limiting, and for example, the correction formula may be stored in a storage unit included in the spectrometer 10 to be calibrated. In this case, the spectrometer 10 in which the correction formula is stored can output a calibrated count value.

[0058] While an embodiment of the present invention has been disclosed, it will be apparent to one skilled in the art that modifications may be made thereto without departing from the scope of the present invention, and it is intended that all such modifications and equivalents be included in the following claims. [Explanation of symbols]

[0059] 1 Calibration device 2 Reference light source 3 Dimming section 4 Power meter (light intensity detector) 5 Bandpass Filter 6 Data acquisition PC (calibration section) 31 ND filters

Claims

1. A spectrometer calibration device that measures the light intensity of incident light for each wavelength, comprising: a reference light source (2) that irradiates a spectroscope (10) to be calibrated with reference light of a predetermined light intensity; an attenuation unit (3) provided between the reference light source and the spectroscope to be calibrated, the attenuation unit being capable of attenuating light incident from the reference light source to the spectroscope to be calibrated and changing transmittance; a light intensity detection unit (4) for measuring the light intensity of a specific wavelength of light attenuated by the light attenuation unit; a calibration unit (6) that calibrates the light-receiving sensitivity of each element of the spectrometer to be calibrated, The calibration unit obtains a relational expression that expresses the relationship between the transmittance and the count value by acquiring, for each different transmittance, count values ​​for each wavelength measured by the spectrometer to be calibrated with respect to the reference light when the transmittance of the attenuation unit is changed, and calibrates the light receiving sensitivity of each element of the spectrometer to be calibrated based on the relational expression.

2. 2. The spectrometer calibration device according to claim 1, wherein the calibration unit acquires, for each different transmittance, an average value of count values ​​for each wavelength measured a predetermined number of times by the spectrometer to be calibrated with respect to the reference light, as the count value for each wavelength.

3. 3. The spectrometer calibration device according to claim 1, wherein the attenuation section has a plurality of ND filters (31) each having a different optical density, and the transmittance of the attenuation section is changed by changing the combination of the plurality of ND filters.

4. 3. The spectrometer calibration device according to claim 1, wherein the relational expression is stored in a memory unit of the spectrometer to be calibrated.

5. a reference light source (2) that irradiates a spectroscope (10) to be calibrated with reference light of a predetermined light intensity; an attenuation unit (3) provided between the reference light source and the spectroscope to be calibrated, the attenuation unit being capable of attenuating light incident from the reference light source to the spectroscope to be calibrated and changing transmittance; a light intensity detection unit (4) for measuring the light intensity of a specific wavelength of light attenuated by the light attenuation unit; A calibration method for a spectrometer in a calibration device including a calibration unit (6) that calibrates the light-receiving sensitivity of each element of the spectrometer to be calibrated, a calibration unit that, when changing the transmittance of the attenuation unit, obtains count values ​​for each wavelength measured by the spectrometer to be calibrated with respect to the reference light for each different transmittance, thereby determining a relational expression that expresses the relationship between the transmittance and the count values, and calibrates the light receiving sensitivity of each element of the spectrometer to be calibrated based on the relational expression.

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