Spectroscopic device and wavelength correction method

Abstract

The invention relates to a spectroscopic device and a wavelength correction method. The present invention is provided with: a correction light source (3); an optical filter (6) that transmits light of a specific wavelength band among the light from the correction light source (3); an entrance slit (SL) into which the light to be measured (L1) and the correction light (L2) from the correction light source (3) that has passed through the optical filter (6) enter; a dispersion means (12) that disperses the light to be measured, which has passed through the entrance slit (SL), into a dispersion image for each wavelength when the light to be measured is measured, and disperses the correction light, which has passed through the entrance slit (SL), into a dispersion image for each wavelength when the wavelength is corrected; a light-receiving sensor (13) that receives the dispersed image; and a calculation control means (7) that, during wavelength correction, calculates the amount of shift from the initial position of the light receiving position in the light receiving sensor (13) on the basis of the dispersion image of the correction light, and performs wavelength correction.

Description

Technical Field

[0001] The present invention relates to a spectroscopic device and a wavelength correction method that can measure the spectral intensity distribution of light to be measured and correct wavelength shift. Background Art

[0002] Conventionally, as a dispersion method of a spectroscopic device for measuring the spectral intensity distribution of light to be measured, a polychromator that has no moving parts and has a high beam utilization efficiency because it simultaneously measures the entire measurement wavelength band is often used. The polychromator is configured to include an entrance slit into which the light to be measured enters, a diffraction grating that disperses the incident light according to the wavelength, a light receiving sensor array that receives each dispersed image and detects the beam intensity of the dispersed image, and the like. These constituent elements are supported by structural components, but changes in the relative positions of the constituent elements over time and heat are inevitable. In the case of a dispersive spectroscope such as a polychromator, the wavelength accuracy is sensitively affected by changes in the relative positions of the constituent elements. Therefore, in order to maintain high accuracy, it is necessary to check and correct the wavelength accuracy.

[0003] As such a wavelength correction method, the method shown in Patent Document 1 is proposed Figure 7 The method shown.

[0004] In Figure 7 One calibration monochromatic light is incident on the polychromator. The shift amounts from the initial positions of the first-order dispersion image (first-order diffraction image) of wavelength λ1 and the second-order dispersion image (second-order diffraction image) of wavelength λ2 are respectively set as d1 and d2.

[0005] The shift amount d1 includes the wavelength shift amount dx caused by changes in the polychromator over time and heat, and the shift amount dλ of the wavelength λ1 of the calibration monochromatic light. That is, d1 = dx + dλ.

[0006] Similarly, the shift amount d2 also includes the wavelength shift amount dx caused by changes in the polychromator over time and heat and the shift amount 2 * dλ of the wavelength λ2 of the calibration monochromatic light. That is, d2 = dx + 2 * dλ.

[0007] Then, based on the two equations d1 = dx + dλ and d2 = dx + 2 * dλ, the wavelength shift amount dx of the polychromator is obtained as dx = 2 * d1 - d2, and wavelength correction is performed based on this shift amount.

[0008] The shift amounts dλ and 2dλ of the wavelengths λ1 and λ2 of the calibration monochromatic light are the amounts of change caused by temperature or the like when a monochromatic LED is used as the calibration monochromatic light source. The wavelength changes of these light sources are noise. The premise of the wavelength calibration method described in Patent Document 1 is as follows: when the wavelength change of the calibration monochromatic light is dλ, the contribution to the shift amount d1 of the first-order dispersion image is the wavelength change dλ. In contrast, in principle, the contribution to the shift amount d2 of the second-order dispersion image is 2*dλ. Moreover, the wavelength calibration method described in Patent Document 1 obtains the wavelength shift amount dx of the remaining polychromator as described above.

[0009] In addition, in Patent Document 2, a calibration method using bright lines of a Ne lamp or the like is proposed. Specifically, this calibration method includes a wavelength shift calibration light source that emits wavelength shift calibration light including a plurality of bright lines for wavelength shift calibration. This calibration method also includes a spectrometer as a wavelength shift calibration spectrometer. The spectrometer includes a spectroscopic unit that receives the respective dispersed spectroscopic lights obtained by dispersing and spectroscopically analyzing incident light according to wavelength and passing them through a plurality of photoelectric conversion elements arranged along the dispersion direction, and outputs respective electrical signals corresponding to the respective light intensities of the respective dispersed spectroscopic lights. Moreover, when the wavelength shift calibration light is measured as incident light by the wavelength shift calibration spectrometer, the wavelength change amount is obtained based on the respective electrical signals output from a plurality of specific photoelectric conversion elements that receive a plurality of bright lines for wavelength shift calibration among the plurality of photoelectric conversion elements. At least one of the plurality of specific photoelectric conversion elements receives a plurality of the plurality of bright lines for wavelength shift calibration.

[0010] Patent Document 1: Japanese Patent No. 3702889 Gazette;

[0011] Patent Document 2: Japanese Patent No. 6992812 Gazette.

[0012] However, in the calibration method described in Patent Document 1, when the wavelength shift amount dx caused by the changes in the polychromator over time and heat is unified regardless of the wavelength, accurate calibration can be performed. However, when the shift amount dx of the polychromator varies depending on the wavelength, calibration residuals remain.

[0013] For example, when a diffraction grating as a dispersion element is formed of a material with a relatively large linear expansion coefficient such as resin, if the diffraction grating expands / contracts due to temperature changes, the groove pitch of the diffraction grating changes. In this case, the dispersion image on the light receiving sensor is magnified or reduced in the wavelength direction, so the wavelength shift amount is not unified. Therefore, in the method of Patent Document 1 described above, there is a problem that a good calibration effect may not be obtained.

[0014] In addition, the calibration method described in Patent Document 2 also focuses on specific bright lines to obtain the wavelength shift amount, and assigns a unified wavelength shift amount to all wavelengths. Therefore, similar to the calibration method described in Patent Document 1, there is a problem that a calibration effect with good accuracy cannot be obtained. In addition, with the recent decrease in the demand for gas discharge tube lamps such as Ne lamps, there is a risk of difficulty in obtaining a desired lamp in the future. Summary of the Invention

[0015] An object of the present invention is to provide a spectroscopic device and a wavelength calibration method that can perform wavelength calibration with good accuracy in the presence of both wavelength changes accompanying temperature changes of a light source for wavelength calibration and wavelength changes caused by changes in a multichromator over time and heat. Another object is to provide a spectroscopic device and a wavelength calibration method that do not require the use of a gas discharge tube lamp such as a Ne lamp as a calibration light source.

[0016] The above object is achieved by the following means.

[0017] (1) A spectroscopic device, comprising:

[0018] At least one calibration light source;

[0019] At least one optical filter that transmits light in a specific wavelength band from the light from the calibration light source;

[0020] At least one incident slit through which the light to be measured and the calibration light from the calibration light source that has passed through the optical filter are incident;

[0021] A dispersion unit that disperses the light to be measured that has passed through the incident slit into a dispersion image for each wavelength when measuring the light to be measured, and disperses the calibration light that has passed through the incident slit into a dispersion image for each wavelength during wavelength calibration;

[0022] A light receiving sensor that receives the dispersion image for each wavelength formed by the dispersion unit and outputs an electrical signal corresponding to the light receiving intensity; and

[0023] An arithmetic control unit that, during wavelength calibration, obtains the shift amount of the light receiving position in the light receiving sensor based on the dispersion image of the calibration light from the initial position, and performs wavelength calibration based on the shift amount.

[0024] (2) The spectroscopic device according to item 1 above, wherein the arithmetic control unit obtains the shift amount for other wavelengths based on the shift amount of each light receiving position in the light receiving sensor for a plurality of dispersion images of one or more calibration light sources from the initial position.

[0025] (3) The spectroscopic device according to item 1 above, wherein the operation control unit calculates the shift amount for other wavelengths based on the shift amount from the initial position of the light-receiving position in the light-receiving sensor of the first-order dispersion image of one or more calibration light sources and the shift amount from the initial position of the light-receiving position in the light-receiving sensor of the second-order dispersion image.

[0026] (4) The spectroscopic device according to any one of items 1 to 3 above, wherein the optical filter is a band-pass filter having at least one spectral transmission band.

[0027] (5) The spectroscopic device according to any one of items 1 to 3 above, wherein the optical filter is a sharp cut-off filter.

[0028] (6) The spectroscopic device according to item 4 above, wherein the operation control unit sets the light-receiving position of the dispersion image to the light-receiving position of any one of the peak wavelength, the center wavelength, and the centroid wavelength of the spectral transmission band.

[0029] (7) The spectroscopic device according to item 4 above, wherein the operation control unit sets the light-receiving position of the dispersion image to the light-receiving position of the cut-off wavelength of the spectral transmission band.

[0030] (8) The spectroscopic device according to item 5 above, wherein the operation control unit sets the light-receiving position of the dispersion image to the light-receiving position of the cut-off wavelength of the sharp cut-off filter.

[0031] (9) The spectroscopic device according to any one of items 1 to 3 above, wherein a switching unit is provided, and the switching unit makes the measurement light incident on the entrance slit when measuring the light to be measured, and makes the calibration light incident on the entrance slit during wavelength calibration.

[0032] (10) The spectroscopic device according to item 9 above, wherein a reflector is provided, and the reflector is configured to freely advance and retreat in the optical path of the measurement light incident on the entrance slit.

[0033] The switching unit withdraws the reflector from the optical path of the measurement light when measuring the light to be measured, and makes the reflector enter the optical path of the measurement light during wavelength calibration so that the calibration light is reflected by the reflector to the entrance slit.

[0034] (11) The spectroscopic device according to item 10 above, wherein the reflector is a diffuse reflector or a mirror.

[0035] (12) The spectroscopic device according to item 9 above, comprising: a light-receiving diffuser plate disposed in the optical path of the measurement light incident on the entrance slit, transmitting the measurement light and diffusely reflecting the calibration light; and a light-shielding plate disposed upstream of the light-receiving diffuser plate and configured to freely advance and retreat in the optical path of the measurement light incident on the entrance slit.

[0036] When measuring the light to be measured, the switching unit withdraws the light shielding plate from the optical path of the light to be measured, and when performing wavelength calibration, the light shielding plate enters the optical path of the light to be measured.

[0037] (13) A wavelength calibration method, comprising:

[0038] A transmission step of transmitting light in a specific wavelength band in the light from at least one calibration light source through at least one optical filter;

[0039] An incident step of making the light to be measured incident on at least one incident slit when measuring the light to be measured, and making the calibration light from the calibration light source after passing through the optical filter incident on the incident slit during wavelength calibration;

[0040] A dispersion step of dispersing the light to be measured or the calibration light passing through the incident slit into dispersion images for each wavelength;

[0041] A light receiving step of receiving the dispersion images for each wavelength formed by the dispersion step through a light receiving sensor and outputting an electrical signal corresponding to the light receiving intensity; and

[0042] An arithmetic control step of, during wavelength calibration, obtaining the shift amount of the light receiving position in the light receiving sensor based on the dispersion image of the calibration light from the initial position, and performing wavelength calibration based on the shift amount.

[0043] (14) The wavelength calibration method according to item 13 above, wherein, in the arithmetic control step, based on the shift amounts of the respective light receiving positions in the light receiving sensor for the dispersion images of one or more calibration light sources from the initial position, the shift amount for other wavelengths is obtained.

[0044] (15) The wavelength calibration method according to item 13 above, wherein, in the arithmetic control step, based on the shift of the light receiving position in the light receiving sensor for the first-order dispersion image of one or more calibration light sources from the initial position and the shift of the light receiving position in the light receiving sensor for the second-order dispersion image from the initial position, the shift amount for other wavelengths is obtained.

[0045] (16) The wavelength calibration method according to any one of items 13 to 15 above, wherein the optical filter is a band-pass filter having at least one spectral transmission band.

[0046] (17) The wavelength calibration method according to any one of items 13 to 15 above, wherein the optical filter is a sharp cut-off filter.

[0047] (18) The wavelength correction method according to item 16 above, wherein in the above operation control step, the light receiving position of the above dispersion image is set to the light receiving position of any one of the peak wavelength, the center wavelength, and the centroid wavelength of the spectral transmission band.

[0048] (19) The wavelength correction method according to item 16 above, wherein in the above operation control step, the light receiving position of the above dispersion image is set to the light receiving position of the cut-off wavelength of the spectral transmission band.

[0049] (20) The wavelength correction method according to item 17 above, wherein in the above operation control step, the light receiving position of the above dispersion image is set to the light receiving position of the cut-off wavelength of the sharp cut-off filter.

[0050] (21) The wavelength correction method according to any one of items 13 to 15 above, further comprising a switching step of making the above measurement light incident on the entrance slit when measuring the light to be measured, and making the above correction light incident on the entrance slit during wavelength correction.

[0051] (22) The wavelength correction method according to item 21 above, wherein the above spectroscopic device includes a reflection plate, and the reflection plate is configured to freely advance and retreat in the optical path of the above measurement light incident on the above entrance slit.

[0052] In the above switching step, when measuring the light to be measured, the reflection plate is withdrawn from the optical path of the measurement light, and when performing wavelength correction, the reflection plate is inserted into the optical path of the measurement light so that the above correction light is reflected by the reflection plate to the above entrance slit.

[0053] (23) The wavelength correction method according to any one of item 22 above, wherein the above reflection plate is a diffuse reflection plate or a mirror.

[0054] (24) The wavelength correction method according to item 21 above, wherein the above spectroscopic device includes: a light receiving diffuser plate disposed in the optical path of the above measurement light incident on the above entrance slit, transmitting the measurement light and diffusely reflecting the correction light; and a light shielding plate disposed upstream of the above light receiving diffuser plate and configured to freely advance and retreat in the optical path of the measurement light incident on the above entrance slit.

[0055] In the above switching step, when measuring the light to be measured, the above light shielding plate is withdrawn from the optical path of the measurement light, and when performing wavelength correction, the above light shielding plate is inserted into the optical path of the measurement light.

[0056] In the inventions described in the preceding items (1) and (13), when measuring the light to be measured, the light to be measured is incident on at least one incident slit. During wavelength calibration, calibration light in a specific wavelength band after passing through at least one optical filter in the light from at least one calibration light source is incident on the incident slit. The light to be measured or the calibration light passing through the incident slit is dispersed into a dispersion image for each wavelength, and the dispersion image is received by a light-receiving sensor. Moreover, during wavelength calibration, the shift amount of the light-receiving position in the light-receiving sensor based on the dispersion image of the calibration light from the initial position is obtained, and wavelength calibration is performed based on the obtained shift amount.

[0057] That is, at least one optical filter that transmits only a specific wavelength band of the light from the wavelength calibration light source is arranged. During wavelength calibration, the light in the specific wavelength band after passing through this optical filter is incident on the incident slit. Therefore, even if a wavelength change occurs in the light from the calibration light source due to temperature changes or the like, the wavelength of the light passing through the optical filter will not be affected by the temperature change and remains fixed. Moreover, the shift amount of the light-receiving position in the light-receiving sensor based on the dispersion image of the calibration light from the initial position is obtained. In this shift amount, there is no influence of the wavelength change accompanying the temperature change, and only the shift amount caused by the changes over time and heat of the spectrograph is included. Therefore, a higher-precision calibration is performed.

[0058] And, since it is not necessary to use a gas discharge tube lamp such as a Ne lamp as the calibration light source, there is no concern about difficulty in obtaining the calibration light source.

[0059] According to the inventions described in the preceding items (2) and (14), there are the following effects: Based on the shift amounts of the light-receiving positions in the light-receiving sensor from the initial position for the multiple dispersion images of one or more calibration light sources, highly accurate shift amounts after eliminating the effects caused by the changes over time and heat of the spectrograph are obtained for multiple wavelengths. Furthermore, a highly accurate wavelength calibration is performed. Moreover, by using the obtained shift amounts for multiple wavelengths, for example, linear interpolation, polynomial interpolation, extrapolation processing, etc., the shift amounts for other wavelengths for which the wavelength shift amounts have not been obtained are estimated with better accuracy. Therefore, highly accurate wavelength calibration is also performed for other wavelengths.

[0060] According to the inventions described in the preceding items (3) and (15), there are the following effects: Based on the shift amount of the light-receiving position in the light-receiving sensor from the initial position for the first-order dispersion image of one or more calibration light sources and the shift amount of the light-receiving position in the light-receiving sensor from the initial position for the second-order dispersion image, wavelength calibration for other wavelengths is performed.

[0061] According to the inventions described in the preceding items (4) and (16), the optical filter is a band-pass filter having at least one spectral transmission band, and thus the optical filter can transmit light in a specific wavelength band of the light from the calibration light source.

[0062] According to the inventions described in the preceding items (5) and (17), the optical filter is a sharp cut-off filter, and thus the optical filter can transmit light in a specific wavelength band of the light from the calibration light source.

[0063] According to the inventions described in the preceding items (6) and (18), the wavelength represented by any one of the peak wavelength, the center wavelength, and the centroid wavelength is corrected.

[0064] According to the inventions described in the preceding items (7) and (19), by setting the light-receiving position of the dispersion image to the light-receiving position of the cut-off wavelength of the spectral transmission band, the wavelength correction amount is obtained with better accuracy.

[0065] According to the inventions described in the preceding items (8) and (20), by setting the light-receiving position of the dispersion image to the light-receiving position of the cut-off wavelength of the sharp cut-off filter, the wavelength correction amount is obtained with better accuracy.

[0066] According to the inventions described in the preceding items (9) and (21), the incident light to the entrance slit is switched so that the light to be measured is incident on the entrance slit when measuring the light to be measured, and the calibration light is incident on the entrance slit during wavelength calibration.

[0067] According to the inventions described in the preceding items (10) and (22), when measuring the light to be measured, the reflector retreats from the optical path of the light to be measured, and when performing wavelength calibration, the reflector enters the optical path of the light to be measured so that the calibration light is reflected by the reflector to the entrance slit. Thus, the wavelength shift amount is reliably obtained during wavelength calibration.

[0068] According to the inventions described in the preceding items (11) and (23), the reflector is a diffuse reflector or a mirror, and thus during wavelength calibration, the calibration light is reliably reflected by the reflector to the entrance slit.

[0069] According to the inventions described in the preceding items (12) and (24), when measuring the light to be measured, the light-shielding plate retreats from the optical path of the light to be measured, and when performing wavelength calibration, the light-shielding plate enters the optical path of the light to be measured, so that the measurement of the light to be measured and the wavelength calibration are switched. BRIEF DESCRIPTION OF THE DRAWINGS

[0070] Figure 1 It is a diagram showing the structure of the spectroscopic device according to an embodiment of the present invention, where (A) is a diagram showing the state when measuring the light to be measured, and (B) is a diagram showing the state during wavelength calibration.

[0071] Figure 2It is a diagram showing examples of the emission spectrum of a calibration light source and the transmission spectrum of an optical filter.

[0072] Figure 3 (A) to (C) of are explanatory diagrams of wavelength calibration using a broadband band-pass filter as the optical filter.

[0073] Figure 4 (A) to (C) of are explanatory diagrams of wavelength calibration using a sharp cut-off filter as the optical filter.

[0074] Figure 5 It is a diagram showing the structure of a spectroscopic device according to another embodiment of the present invention. (A) thereof is a diagram showing the state when measuring the light to be measured, and (B) is a diagram showing the state during wavelength calibration.

[0075] Figure 6 It is a diagram showing the structure of a spectroscopic device according to still another embodiment of the present invention. (A) thereof is a diagram showing the state when measuring the light to be measured, and (B) is a diagram showing the state during wavelength calibration.

[0076] Figure 7 It is a diagram for explaining a conventional method of wavelength calibration. Detailed Embodiments

[0077] Hereinafter, embodiments of the present invention will be described based on the drawings.

[0078] (First Embodiment)

[0079] Figure 1 It is a diagram showing the structure of a spectro-brightness meter as an example of a spectroscopic device capable of performing wavelength calibration. Figure 1 The spectro-brightness meter 1 shown includes a light-receiving optical system 2 having a front light-receiving lens 21 and a rear light-receiving lens 22, a calibration light source 3, a reflector 4, a drive motor 5, an optical filter 6, an arithmetic control unit 7, and a polychromator 10 as a spectroscope.

[0080] The light-receiving lens optical system 2 is a component that guides the light to be measured L1 to the polychromator 10. The light to be measured L1 includes irradiation light irradiated from the light source to be measured 100 and reflected light from the object to be measured, etc.

[0081] The calibration light source 3 is a light source that is lit and used during wavelength calibration. In the present embodiment, it is composed of an LED and outputs monochromatic light with a wavelength change.

[0082] The reflector 4 is a diffuse reflector and is driven by the drive motor 5 to enter or exit the optical path of the light to be measured L1 at a position close to the front lens 21 between the front lens 21 and the rear lens 22 of the light-receiving optical system 2. As Figure 1As shown in (A), the reflector 4 withdraws from the optical path of the measured light L1 when measuring the measured light L1. In this state, the measured light L1 passes through the light receiving optical system 2 and enters the polychromator 10. On the other hand, as Figure 1 shown in (B), during wavelength calibration, the reflector 4 is driven into the optical path of the measured light L1. In this state, the optical path of the measured light L1 is blocked, and the calibration light L2 emitted from the calibration light source 3 and passing through the optical filter 6 is reflected and guided to the polychromator 10. In this way, the reflector 4 and the drive motor 5 function as a switching unit for switching whether to guide the measured light L1 or the calibration light L2 to the polychromator 10.

[0083] The optical filter 6 is arranged between the calibration light source 3 and the reflector 4. In the present embodiment, the optical filter 6 is a band-pass filter that only transmits a specific wavelength band and is formed of a dielectric multilayer film.

[0084] In Figure 2 an example of the LED emission spectrum of the calibration light source 3 and the transmission spectrum of the optical filter 6 is shown. The dashed line is the LED emission spectrum of the calibration light source 3, and the solid line is the transmission spectrum of the optical filter 6. By making the LED emission spectrum close to the center wavelength of the frequency band of the optical filter 6, light is used efficiently. The peak wavelength of the LED emission spectrum and the peak wavelength of the optical filter 6 can be matched within ±10 nm.

[0085] The LED emission spectrum of the calibration light source 3 shifts by several nm according to temperature changes. However, the temperature change of the transmission spectrum of the dielectric multilayer film filter as the optical filter 6 is small enough and stable, so the robustness as a light source can be improved. In addition, by setting the transmission bandwidth of the optical filter 6 to be sufficiently narrow with respect to the half-value width of the LED emission spectrum, the influence (such as the change in the center of gravity position) of the shift of the LED emission spectrum on the light transmitted through the filter can be minimized.

[0086] Returning to Figure 1 , the polychromator 10 includes a slit plate 11, a diffraction grating 12, a light receiving sensor array 13, etc.

[0087] An incident slit SL is formed in the slit plate 11. The incident slit SL can be one or more than two.

[0088] The diffraction grating 12 functions as a dispersion unit. The diffraction grating 12 reflects and disperses the measured light L1 that has passed through the incident slit SL, or the calibration light L2 emitted from the calibration light source 3, passing through the optical filter 6, and reflected by the reflector 4, into a dispersion image corresponding to the wavelength, and forms an image on the light receiving sensor array 13.

[0089] The light-receiving sensor array 13 is composed of a plurality of photoelectric conversion elements (hereinafter also referred to as sensors) arranged at a prescribed interval, for example, at an interval corresponding to about 10 nm of the wavelength of the dispersed light. The electric signals corresponding to the received light intensity output from each sensor are processed by the arithmetic control unit 7.

[0090] The arithmetic control unit 7 is composed of, for example, a CPU (Central Processing Unit) and an EEPROM (electrically erasable storage device), etc. When performing wavelength correction, the arithmetic control unit 7 causes the correction light L2 to be incident on the slit SL, and obtains the amount of change in the light-receiving position in the light-receiving sensor array 13 of the dispersed image for each wavelength dispersed by the diffraction grating 12 from the initial position as the image shift amount (wavelength shift amount). Regarding the obtained wavelength shift amount, as will be described later, the influence of the wavelength change of the correction light L2 is removed. In addition, the arithmetic control unit 7 performs various arithmetic processes for wavelength correction, lighting control of the correction light source 3, driving control of the driving motor 5, and the like.

[0091] During Figure 1 the measurement of the measurement object light L1 shown in (A) of

[0092] During Figure 1 the wavelength correction shown in (B) of

[0093] The so-called first-order dispersion image refers to any one of the images generated by the ±1st order diffracted light of the diffraction grating 12. The wavelength of the first-order dispersion image can be defined by any one of various known methods such as the centroid wavelength, the Gaussian approximation peak wavelength, the central wavelength, etc. The same applies to other embodiments described later, and also to the second-order dispersion image described later. The light-receiving position of the first-order dispersion image on the light-receiving sensor array 13 at the time of factory shipment is stored as the initial position in a storage unit (not shown). The arithmetic control unit 7 obtains the difference between the initial position and the light-receiving position of the first-order dispersion image obtained during wavelength calibration after shipment as the wavelength shift amount, and corrects the wavelength based on this shift amount. For example, it can be considered to directly set the shift amount as the correction amount.

[0094] Even if the wavelength of the light from the calibration light source 3 shifts due to temperature or the like, the transmission bandwidth of the optical filter 6 is fixed, and the wavelength of the calibration light L2 transmitted through the optical filter 6 is not affected by temperature or the like and is fixed. Therefore, in the wavelength shift amount obtained by the arithmetic control unit 7, the wavelength shift accompanying temperature change is excluded, and only the shift caused by changes in the relative positions of the respective optical elements in the monochromator 10 over time and heat is included. Therefore, a wavelength shift amount with higher accuracy can be obtained, and furthermore, high-precision wavelength calibration can be performed.

[0095] Here, by preparing multiple combinations of the LED as the calibration light source 3 and the optical filter 6 while changing the wavelength, the shift amount can be obtained for multiple wavelengths. For wavelengths other than the multiple wavelengths for which the shift amount has been obtained, the wavelength shift amount can be estimated by linear interpolation, polynomial interpolation, extrapolation processing, etc. using the obtained wavelength shift amount. Since the shift amount for multiple wavelengths is obtained with high precision, the wavelength shift amount for other wavelength bands is estimated by using these shift amounts, thereby achieving high-precision wavelength calibration over the entire measurement wavelength range.

[0096] In addition, not only the first-order dispersion image of the calibration light L2 but also the second-order dispersion image can be used. For example, when the central wavelength of the transmitted light of the optical filter 6 is 375 nm, the first-order dispersion image is imaged at the 375 nm position, but the second-order dispersion image is imaged at the 750 nm position. When the wavelength of the second-order dispersion image is 375 nm, but the dispersion unit of the monochromator 10 is composed of a reflective optical system such as a reflective diffraction grating and a concave mirror, the change in the second-order dispersion image of the 375 nm light accompanying the change in the dispersion unit is the same as the change in the first-order dispersion image of the 750 nm light. Therefore, the wavelength shift amounts of two wavelengths can be obtained by one combination of the calibration light source 3 and the optical filter 6.

[0097] In addition, an optical filter 6 having multiple transmission bands can be used. In this case, the wavelength shift amount for multiple first-order dispersion images can be obtained by one optical filter 6.

[0098] (Second Embodiment)

[0099] In this embodiment, a broadband light source such as a halogen lamp or a white LED is used as the calibration light source 3. In addition, a broadband band-pass filter that transmits only wavelengths in a specific range, as shown by the solid line in (A) of Figure 3 , is used as the optical filter 6. In these aspects, this second embodiment is different from the first embodiment. Furthermore, in Figure 3 , the emission spectrum of the calibration light source 3 is represented by the dashed line in (A).

[0100] As Figure 3 shown in (B), the spectrum of the calibration light L2 that has passed through the broadband band-pass filter serving as the optical filter 6 is obtained by the light-receiving sensor array 13 of the multichromator 10. Then, as Figure 3 shown in (C), the filter cut-off wavelength is obtained by performing differential processing or the like on the obtained spectrum, and this is set as the light-receiving position of the dispersion image. Moreover, in the same manner as in the first embodiment, the difference between the light-receiving position when the cut-off wavelength position at the time of factory shipment is the initial position and the initial position is set as the wavelength shift amount.

[0101] By combining one calibration light source 3 and the optical filter 6, the wavelength shift amounts for two wavelengths corresponding to the filter cut-off wavelength can be obtained. If second-order dispersion images are also used for each wavelength, the wavelength correction amounts for four wavelengths can be obtained, and more calibration information can be obtained. In addition, a plurality of calibration light sources 3 and the optical filter 6 can be combined to obtain the wavelength shift amounts for two wavelengths corresponding to the filter cut-off wavelength of each optical filter 6. Additionally, second-order dispersion images can also be used for each wavelength.

[0102] (Third Embodiment)

[0103] In this embodiment, it is different from the second embodiment in that a sharp cut-off filter having a characteristic of truncating wavelengths below a certain wavelength (cut-off wavelength), as shown in (A) of Figure 4 , is used as the optical filter 6. Furthermore, in Figure 4 , the emission spectrum of the calibration light source 3 is represented by the dashed line in (A).

[0104] The central wavelength of the LED serving as the calibration light source 3 is made close to the cut-off wavelength. As Figure 4 shown in (B), the spectrum of the calibration light L2 that has passed through the sharp cut-off filter serving as the optical filter 6 is obtained by the light-receiving sensor array 13 of the multichromator 10. Next, as Figure 4As shown in (C), the obtained spectrum is differentiated or the like to obtain the cut-off wavelength, and the light-receiving position of the dispersion image is set. Moreover, in the same manner as in the first embodiment, the difference between the light-receiving position when the cut-off wavelength position at the time of factory shipment is set as the initial position and the initial position is set as the wavelength shift amount.

[0105] In this case as well, by preparing a plurality of combinations of the LED serving as the calibration light source 3 and the optical filter 6 while changing the cut-off wavelength, the wavelength shift amount can be obtained for a plurality of wavelengths. In addition, if not only the first-order dispersion image but also the second-order dispersion image can be used, the number of combinations of the calibration light source 3 and the optical filter 6 can be reduced.

[0106] (Fourth Embodiment)

[0107] Figure 5 FIG. is a diagram showing the structure of a spectro-emission illuminometer 1' which is another example of a spectroscopic device capable of wavelength calibration.

[0108] This spectro-emission illuminometer 1' includes a light-receiving diffuser plate 31 that receives and diffuses the measurement light L1 from the light source 100 to be measured. The measurement light L1 that has passed through the light-receiving diffuser plate 31 passes through a lens 32 and enters the slit SL of the polychromator 10.

[0109] In addition, there is no Figure 1 The reflecting plate 4 and the front lens 21 that freely advance and retreat in the optical path of the measurement light L1 provided in the first embodiment shown. It is configured to be able to irradiate the light-receiving diffuser plate 31 with the calibration light L2 emitted from the calibration light source 3 and transmitted through the optical filter 6.

[0110] In this embodiment, a light-shielding member 33 is also provided. This light-shielding member 33 is driven by a drive motor 5 at a position upstream of the light-receiving diffuser plate 31 to enter or exit the optical path of the measurement light L1. As Figure 5 shown in (A), when measuring the measurement light L1, the light-shielding member 33 exits from the optical path of the measurement light L1, and the measurement light L1 passes through the light-receiving diffuser plate 31 and enters the slit SL of the polychromator 10. On the other hand, as Figure 5 shown in (B), during wavelength calibration, the light-shielding member 33 enters the optical path of the measurement light L1. In this state, the optical path of the measurement light L1 is blocked, so that the measurement light L1 cannot enter the light-receiving diffuser plate 31. The calibration light L2 emitted from the calibration light source 3 and transmitted through the optical filter 6 is diffusely reflected by the light-receiving diffuser plate 31 and guided to the slit SL of the polychromator 10. That is, between when measuring the measurement light L1 and during wavelength calibration, the measurement light L1 and the calibration light L2 are alternately guided to the slit SL of the polychromator 10.

[0111] In addition, the structures of the calibration light source 3, the drive motor 5, the optical filter 6, the arithmetic control unit 7, and the spectrograph 10 are the same as those in Figure 1 the embodiment shown. Additionally, the calculation operation of the wavelength correction amount by the arithmetic control unit 7 is also the same as that in the first embodiment.

[0112] (Fifth Embodiment)

[0113] As Figure 6 shown, this embodiment has the same structure as the first embodiment except that the reflector (diffuse reflector) 4 in the first embodiment is replaced by a reflecting mirror 41, and the positions of the calibration light source 3 and the entrance slit SL are conjugate.

[0114] When Figure 6 measuring the measurement target light L1 shown in (A), the drive motor 5 moves the reflecting mirror 41 away from the optical axis of the measurement target light L1. When Figure 6 performing wavelength calibration shown in (B), the drive motor 5 moves the reflecting mirror 41 onto the optical axis of the measurement target light L1. As a result, the calibration light L2 is specularly reflected by the reflecting mirror surface and enters the spectrograph 10. That is, between the measurement of the measurement target light L1 and the wavelength calibration, the measurement target light L1 and the calibration light L2 are alternately guided to the slit SL of the spectrograph 10.

[0115] In this embodiment, the calculation operation of the wavelength shift amount by the arithmetic control unit 7 is the same as that in the first embodiment.

[0116] In Figure 5 the embodiment, the required precision for the position and posture of the reflecting mirror 41 is relatively high, but by inserting a diffuser plate between the optical filter 6 and the reflecting mirror 41, the required precision can be alleviated.

[0117] The above describes one embodiment of the present invention, but the present invention is not limited to the above embodiment. For example, the optical filter 6 is disposed between the calibration light source 3 and the reflector 4 or the light-receiving diffuser plate 31 or the reflecting mirror 41. However, the optical filter 6 can also be disposed at a position between the reflector 4 or the light-receiving diffuser plate 31 or the reflecting mirror 41 and the lens 22 or the lens 32, or at a position between the lens 22 or the lens 32 and the spectrograph 10. When the optical filter 6 is disposed at these positions, it is necessary to drive the optical filter 6 together with the drive of the reflector 4 or the like so that the optical filter 6 exits from the optical path of the measurement target light L1 during the measurement of the measurement target light L1 and enters the optical path of the measurement target light L1 during the wavelength calibration, so as not to affect the measurement of the measurement target light L1.

[0118] As described above, in the present embodiment, even if wavelength shifts occur due to changes over time and heat in the relative positions of the respective optical elements in the polychromator 10, it is possible to correct them and maintain the wavelength accuracy at the time of initial wavelength correction.

[0119] As described above, one embodiment of the present invention has been described, but the present invention is not limited to the above-described embodiment. For example, the following structure has been shown: a switching unit is driven by a motor or the like to switch so that the measurement light L1 is incident on the entrance slit SL when measuring the measurement light L1, and the calibration light L2 passes through the optical filter 6 and is incident on the entrance slit SL during wavelength calibration. However, the switching may be performed manually, or the optical filter 6 may be moved manually. Further, during wavelength calibration, the entrance hole for allowing the measurement light L1 to enter the spectroscopic device may be blocked by an external cover or the like so that the measurement light L1 does not enter the spectroscopic device 1. Further, the calibration light source 3 may be arranged outside, and during wavelength calibration, the light from the calibration light source 3 is incident on the spectroscopic device, passes through the optical filter 6 arranged inside the spectroscopic device 1, and is guided to the entrance slit SL. Further, the calibration light source 3 and the optical filter 6 may be arranged outside the spectroscopic device 1, and during wavelength calibration, the calibration light L2 emitted from the calibration light source 3 and passing through the optical filter 6 is incident on the spectroscopic device 1 and is guided to the entrance slit SL.

[0120] This application claims the priority of Japanese Patent Application No. 2022-178276 filed on November 7, 2022, the disclosure of which is directly incorporated herein by reference.

[0121] The present invention can be used as a spectroscopic device or the like that can measure the spectral intensity distribution of the measurement light and correct wavelength shifts. And it is not necessary to use a gas discharge tube lamp such as a Ne lamp as the calibration light source.

[0122] Description of reference numerals

[0123] 1 Spectroscopic luminance meter (spectroscopic device)

[0124] 1' Spectroscopic emission illuminance meter (spectroscopic device)

[0125] 2 Light receiving lens system

[0126] 3 Calibration light source

[0127] 4 Reflector

[0128] 5 Driving motor

[0129] 6 Optical filter

[0130] 7 Arithmetic control unit

[0131] 10 Polychromator

[0132] 11 Slit plate

[0133] 12 Diffraction grating

[0134] 13 Light-receiving sensor array

[0135] 31 Light-receiving diffuser plate

[0136] 33 Light-shielding member

[0137] 41 Reflector

[0138] SL Slit

Claims

1. A spectroscopic device, wherein, it comprises: at least one calibration light source; at least one optical filter that transmits light in a specific wavelength band among the light from the above-mentioned calibration light source; at least one entrance slit through which the light to be measured and the calibration light from the calibration light source that has passed through the above-mentioned optical filter enter; a dispersion unit that disperses the light to be measured that has passed through the above-mentioned entrance slit into a dispersion image for each wavelength when measuring the light to be measured, and disperses the calibration light that has passed through the above-mentioned entrance slit into a dispersion image for each wavelength during wavelength calibration; a light receiving sensor that receives the dispersion image for each wavelength formed by the above-mentioned dispersion unit and outputs an electrical signal corresponding to the light receiving intensity; and an arithmetic control unit that, during wavelength calibration, obtains the shift amount of the light receiving position in the above-mentioned light receiving sensor based on the dispersion image of the above-mentioned calibration light from the initial position, and performs wavelength calibration based on the shift amount.

2. The spectroscopic device according to claim 1, wherein, the above-mentioned arithmetic control unit obtains the shift amount for other wavelengths based on the shift amounts of the respective light receiving positions in the above-mentioned light receiving sensor for a plurality of dispersion images of one or more calibration light sources from the initial position.

3. The spectroscopic device according to claim 1, wherein, the above-mentioned arithmetic control unit obtains the shift amount for other wavelengths based on the shift amount of the light receiving position in the light receiving sensor for the first-order dispersion image of one or more calibration light sources from the initial position and the shift amount of the light receiving position in the light receiving sensor for the second-order dispersion image from the initial position.

4. The spectroscopic device according to any one of claims 1 to 3, wherein, the above-mentioned optical filter is a band-pass filter having at least one spectral transmission band.

5. The spectroscopic device according to any one of claims 1 to 3, wherein, the above-mentioned optical filter is a sharp cut-off filter.

6. The spectroscopic device according to claim 4, wherein, the above-mentioned arithmetic control unit sets the light receiving position of the above-mentioned dispersion image to the light receiving position of any one of the peak wavelength, center wavelength, and centroid wavelength of the spectral transmission band.

7. The spectroscopic device according to claim 4, wherein, the above-mentioned arithmetic control unit sets the light receiving position of the above-mentioned dispersion image to the light receiving position of the cut-off wavelength of the spectral transmission band.

8. The spectroscopic device according to claim 5, wherein, the above-mentioned arithmetic control unit sets the light receiving position of the above-mentioned dispersion image to the light receiving position of the cut-off wavelength of the sharp cut-off filter.

9. The spectroscopic device according to any one of claims 1 to 3, wherein, the above-mentioned spectroscopic device is provided with a switching unit, and the switching unit makes the above-mentioned light to be measured enter the entrance slit when measuring the light to be measured, and makes the above-mentioned calibration light enter the entrance slit during wavelength calibration.

10. The spectroscopic device according to claim 9, wherein, the above-mentioned spectroscopic device is provided with a reflector, and the reflector is configured to move freely in and out of the optical path of the above-mentioned light to be measured incident on the above-mentioned entrance slit, the above-mentioned switching unit makes the reflector withdraw from the optical path of the light to be measured when measuring the light to be measured, and makes the reflector enter the optical path of the light to be measured during wavelength calibration so that the above-mentioned calibration light is reflected by the reflector to the above-mentioned entrance slit.

11. The spectroscopic device according to claim 10, wherein, the reflection plate is a diffuse reflection plate or a mirror.

12. The spectroscopic device according to claim 9, wherein, the spectroscopic device includes: a light-receiving diffuser plate disposed in the optical path of the measurement light incident on the incident slit, transmitting the measurement light and diffusely reflecting the calibration light; and a light-shielding plate disposed upstream of the light-receiving diffuser plate so as to be able to freely advance and retreat in the optical path of the measurement light incident on the incident slit, the switching unit withdraws the light-shielding plate from the optical path of the measurement light during measurement of the measurement light, and inserts the light-shielding plate into the optical path of the measurement light during wavelength calibration.

13. A wavelength calibration method, wherein, it includes: a transmission step of transmitting light in a specific wavelength band in the light from at least one calibration light source through at least one optical filter; an incidence step of causing the measurement light to be incident on at least one incident slit during measurement of the measurement light, and causing the calibration light from the calibration light source that has passed through the optical filter to be incident on the incident slit during wavelength calibration; a dispersion step of dispersing the measurement light or the calibration light that has passed through the incident slit into a dispersion image for each wavelength; a light-receiving step of receiving the dispersion image for each wavelength formed by the dispersion step through a light-receiving sensor and outputting an electrical signal corresponding to the light-receiving intensity; and an arithmetic control step of, during wavelength calibration, obtaining the shift amount of the light-receiving position in the light-receiving sensor based on the dispersion image of the calibration light from the initial position, and performing wavelength calibration based on the shift amount.

14. The wavelength calibration method according to claim 13, wherein, in the arithmetic control step, based on the shift amounts of the respective light-receiving positions in the light-receiving sensor for a plurality of dispersion images of one or more calibration light sources from the initial position, the shift amounts for other wavelengths are obtained.

15. The wavelength calibration method according to claim 13, wherein, in the arithmetic control step, based on the shift of the light-receiving position in the light-receiving sensor for the first-order dispersion image of one or more calibration light sources from the initial position and the shift of the light-receiving position in the light-receiving sensor for the second-order dispersion image from the initial position, the shift amounts for other wavelengths are obtained.

16. The wavelength calibration method according to any one of claims 13 to 15, wherein, the optical filter is a band-pass filter having at least one spectral transmission band.

17. The wavelength calibration method according to any one of claims 13 to 15, wherein, the optical filter is a sharp cut-off filter.

18. The wavelength calibration method according to claim 16, wherein, in the arithmetic control step, the light-receiving position of the dispersion image is set to the light-receiving position of any one of the peak wavelength, the center wavelength, and the centroid wavelength of the spectral transmission band.

19. The wavelength calibration method according to claim 16, wherein, in the arithmetic control step, the light-receiving position of the dispersion image is set to the light-receiving position of the cut-off wavelength of the spectral transmission band.

20. The wavelength calibration method according to claim 17, wherein, In the above operation control step, the light-receiving position of the above chromatic dispersion image is set to the light-receiving position of the cut-off wavelength of the sharp cut-off filter.

21. The wavelength correction method according to any one of claims 13 to 15, wherein, the above wavelength correction method further includes a switching step, in which the above measured light is incident on the incident slit when measuring the measured light, and the above correction light is incident on the incident slit during wavelength correction.

22. The wavelength correction method according to claim 21, wherein, the above spectroscopic device includes a reflector, and the reflector is configured to freely advance and retreat in the optical path of the above measured light incident on the above incident slit, in the above switching step, the reflector is withdrawn from the optical path of the measured light when measuring the measured light, and the reflector enters the optical path of the measured light during wavelength correction so that the above correction light is reflected by the reflector to the above incident slit.

23. The wavelength correction method according to claim 22, wherein, the above reflector is a diffuse reflector or a mirror.

24. The wavelength correction method according to claim 21, wherein, the above spectroscopic device includes: a light-receiving diffuser plate, disposed in the optical path of the above measured light incident on the above incident slit, transmitting the measured light and diffusely reflecting the correction light; and a light-shielding plate, disposed upstream of the above light-receiving diffuser plate and configured to freely advance and retreat in the optical path of the measured light incident on the above incident slit, in the above switching step, the light-shielding plate is withdrawn from the optical path of the measured light when measuring the measured light, and the light-shielding plate enters the optical path of the measured light during wavelength correction.

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