Spectroscopic measurement device

Abstract

A spectrometric device according to an aspect of the present application includes: a light splitting section (2) including a diffraction grating; a detection section (2) that detects light wavelength-dispersed by the diffraction grating; a rotation section that rotates the diffraction grating; a light blocking section that blocks measured light introduced into the light splitting section; a measurement condition setting section (4, 5) that sets a plurality of measurement conditions including a wavelength of a measurement target and at least one parameter value among an integration time, a gain, or a number of data accumulations; and a control section (4) that acquires a dark field measurement value for each of the plurality of measurement conditions set by the measurement condition setting section, blocks the measured light using the light blocking section, and performs a dark field measurement at other parameter values included in each measurement condition after rotating the diffraction grating to a position corresponding to the measurement target wavelength included in the measurement condition using the rotation section. Thus, a dark field measurement value can be accurately obtained.

Description

Technical Field

[0001] This invention relates to a spectrophotometer. Background Technology

[0002] In a typical spectrophotometer, the light to be measured is guided into a spectrometer to disperse its wavelength, and the dispersed wavelength light is then guided into a detector for detection. For example, in a spectrophotometer using a Czerny-Turner type spectrometer as disclosed in Patent Document 1, by rotating the diffraction grating included in the spectrometer, the wavelength of the light reaching the detector can be varied in multiple stages or scanned within a specified range.

[0003] The detector used in this type of spectrophotometer can output a very small level of detection signal, also known as a dark current signal, even when no light is incident on it. Therefore, in order to perform accurate spectrophotometry, the influence of the dark current signal must be eliminated, and it is usually corrected based on the dark current signal measured when no light is incident on the detector.

[0004] In typical spectrophotometers, to prevent light from incident on the detector when measuring dark current, a shutter is usually installed on the light source emitting the light to be measured or on the optical path from the incident end of the light to the detector. Closing the shutter blocks the light being measured. Furthermore, in the following description, this measurement of the dark current signal is referred to as dark-field measurement, and the dark current signal value is referred to as the dark-field measurement value.

[0005] [Existing technical documents]

[0006] [Patent Literature]

[0007] Patent Document 1: Japanese Patent Application Publication No. 2001-141565

[0008] [Non-patent literature]

[0009] Non-Patent Document 1: "SPG-VS00 Laser Spectrometer", Shimadzu Corporation, [Online], [Searched February 15, 2021], Internet <URL:

[0010] https: / / www.shimadzu.co.jp / products / opt / spectro / sp9-v500.htmL Summary of the Invention

[0011] [The problem the invention aims to solve]

[0012] In the spectrophotometer disclosed in Non-Patent Document 1, multiple measurement conditions, such as the wavelength of the target object or the integration time in the detector, can be pre-programmed, and the spectrum with a predetermined wavelength width centered on the wavelength of the target object can be measured simultaneously. In this type of device, in order to improve the accuracy of the spectrum, the dark field measurement value must be obtained with high precision. The dark field measurement value varies not only with the light receiving characteristics of each detector but also with the integration time (charge accumulation time) or gain of the detector. Therefore, as described above, under different conditions such as integration time, it is necessary to perform a corresponding dark field measurement, and this function can also be incorporated into the spectrophotometer disclosed in Non-Patent Document 1.

[0013] However, the inventors' research has shown that the dark-field measurements under various conditions may not be sufficiently accurate, and there is room for further improvement. This invention was made to solve this problem, and its purpose is to provide a spectrophotometer that improves the accuracy of light intensity or spectral data by performing more accurate dark-field measurements.

[0014] [Technical means to solve the problem]

[0015] One embodiment of the spectrophotometer of the present invention, which was developed to solve the aforementioned problem, includes:

[0016] The beam-splitting section includes a diffraction grating;

[0017] The detection unit detects light whose wavelength is dispersed as it passes through the diffraction grating;

[0018] The rotating part causes the diffraction grating to rotate;

[0019] A light-shielding section blocks the light to be measured from entering the beam-splitting section.

[0020] The measurement condition setting unit sets multiple sets of measurement conditions, including at least one parameter value from the wavelength of the measurement object and integration time, gain, or number of data accumulations; and

[0021] The control unit is used to acquire the dark field measurement value of each of the multiple measurement conditions set in the measurement condition setting unit, and to block the measured light by the light shielding unit. Under each measurement condition, the control unit rotates the diffraction grating to a position corresponding to the wavelength of the measurement object included in the measurement condition, and then performs dark field measurement under other parameter values ​​included in the measurement condition.

[0022] When acquiring the intensity or spectrum of light provided from the outside, the "light to be measured" is the light provided from the outside itself. Furthermore, when irradiating a sample with light emitted from a light source and performing spectroscopic measurements on transmitted or reflected light, scattered light, fluorescence, etc., from the sample, the "light to be measured" is the transmitted light, reflected light, scattered light, fluorescence, etc. Moreover, when irradiating a sample with light emitted from a light source after spectral dispersion and monochromaticization, and detecting transmitted or reflected light, the "light to be measured" is the light emitted from the light source itself.

[0023] [The effects of the invention]

[0024] In the described configuration of the spectrophotometer of the present invention, if the light to be measured is blocked by the light-shielding part, the light introduced into the spectrophotometer is approximately zero. Therefore, ideally, light will not be incident on the detection unit regardless of the rotational position of the diffraction grating. Thus, conventionally, when performing dark-field measurements under different measurement conditions, including varying integration times as parameters, the position of the diffraction grating is fixed regardless of the wavelength of the object being measured. However, the inventors have discovered that the dark-field measurement value is affected by the wavelength of the object being measured, i.e., the position of the diffraction grating. Figure 6 This is a graph showing the results obtained from measuring the relationship between the set wavelength and the dark field measurement value in a laser spectral analyzer, as disclosed in Non-Patent Document 1. As mentioned above, the reason why the dark field measurement value varies depending on the position of the diffraction grating is explained below, but this difference has not been considered previously.

[0025] In contrast, in the configuration of the spectrophotometer of the present invention, during dark-field measurement, the diffraction grating is also rotated to a position corresponding to the wavelength of the object being measured, as determined under each measurement condition. Therefore, it is possible to determine the wavelength of the object with high accuracy. Figure 6 The dark field measurement values ​​shown vary depending on the position of the diffraction grating. Thus, with the configuration of the spectrophotometer according to the present invention, not only parameters such as integration time can be obtained, but also high-precision dark field measurement values ​​corresponding to the wavelength of each measured object can be obtained. Therefore, dark field correction can be performed with good accuracy within any wavelength or wavelength range, and high-precision light intensity or spectrum can be obtained. Attached Figure Description

[0026] Figure 1 This is a block structure diagram of a spectrometer, which is one embodiment of the spectrophotometer of the present invention.

[0027] Figure 2 This is a schematic optical path structure diagram of the spectrophotometer detection unit in this embodiment.

[0028] Figure 3This is a flowchart illustrating the standard measurement procedure in the spectrometer of this embodiment.

[0029] Figure 4 This is a flowchart of the dark field measurement process in the spectrometer of this embodiment.

[0030] Figure 5 This is a diagram illustrating an example of the measurement conditions in the spectrometer of this embodiment.

[0031] Figure 6 This is a graph illustrating an example of the relationship between the set wavelength and the dark field measurement value in a conventional spectrometer. Detailed Implementation

[0032] Hereinafter, a spectrometer as an embodiment of the spectrophotometric apparatus of the present invention will be described in detail with reference to the accompanying drawings.

[0033] Figure 1 This is a block structure diagram of the spectrometer of this embodiment. Figure 2 This is an optical path structure diagram centered on the spectrophotometer detection unit in this embodiment.

[0034] The spectrometer is a device that has the same function as, for example, the laser spectrometer disclosed in Non-Patent Document 1, and measures the spectrum of the input light to be measured (usually a laser).

[0035] like Figure 1 As shown, this device includes an inlet optical system 1, a spectroscopic detection unit 2, a data processing unit 3, a control unit 4, an input unit 5, and a display unit 6.

[0036] like Figure 2 As shown, the input optical system 1 includes an optical input connector 10 for connecting to an optical fiber used to input the light to be measured, and a guiding optical system 11 for guiding the input light.

[0037] The spectrophotometer detection unit 2 includes a Cheney-Turner type spectrometer that disperses the wavelength of the introduced light to be measured, and a multi-channel detector 25 that detects the dispersed wavelength light. The detector 25 is a linear sensor with a large number of light-receiving elements arranged in the wavelength dispersion direction, which can simultaneously detect light with different wavelength widths according to its center wavelength.

[0038] like Figure 2 As shown, the beam splitter includes an entrance slit 20, a first concave mirror 21, a diffraction grating 22, a second concave mirror 24, and includes, as shown in the figure, an entrance slit 20, a first concave mirror 21, a diffraction grating 22, a second concave mirror 24, and other components. Figure 2 The diffraction grating rotation drive unit 27 of the motor that rotates the diffraction grating 22 as shown by the middle arrow A, the shutter 26 located at the entrance of the beam splitter to block the incoming light, and the shutter 26 at... Figure 2The shutter drive unit 28 moves between the position shown by the solid line and the position shown by the dashed line (26A). Although not shown, these beam-splitting detection units 2 are housed in a housing that is substantially completely light-blocking in a manner that prevents external light from entering except for the introduced light.

[0039] The data processing unit 3 includes a spectral data storage unit 30, a dark field measurement value storage unit 31, a calculation processing unit 32, and a display processing unit 33 as functional blocks. The control unit 4 includes a measurement condition storage unit 40. Furthermore, the data processing unit 3 and the control unit 4 use a computer (e.g., a personal computer) including a central processing unit (CPU) as hardware resources to execute software mounted on the computer, thereby enabling the implementation of each function.

[0040] Next, the procedure for measurement using the spectrometer of this embodiment and the operation of the spectrometer at this time will be explained. Figure 3 It is a flowchart representing the standard measurement procedure.

[0041] In the spectrometer, the diffraction grating 22 can rotate freely, but even when fixed in a certain position, spectral data of a specified wavelength width (which varies depending on the center wavelength) can be simultaneously measured by a multi-channel detector 25. The spectrometer is designed to measure a wide range of laser light, from the ultraviolet to the near-infrared region. Therefore, a predetermined number of measurement conditions (e.g., a maximum of 10) can be preset, and any one of these conditions can be selected to perform a high-resolution spectral measurement under the selected condition.

[0042] During the measurement, the user first performs the prescribed operation in the input section 5 to initially set the measurement conditions (step S1). As an initial setting, the number of measurement conditions to be set and the items to be set under each measurement condition are selected.

[0043] Figure 5 This is a diagram illustrating an example of measurement conditions. In this example, parameters such as set wavelength, integration time, gain, and number of accumulations can be set for each measurement condition, and the values ​​of the parameters for each parameter can be set. The set wavelength is the center wavelength of the wavelength width of the object being measured; in the case of laser spectral measurement, the oscillation wavelength of the laser is usually set as the set wavelength. The integration time is the charge accumulation time in the detector 25. The gain is the gain of the detector 25. The number of accumulations is the number of times a data point obtained by integrating over the "integration time" is accumulated. Furthermore, the measurement interval for multiple measurements during data accumulation can also be added to the measurement condition parameters.

[0044] Next, the user performs a prescribed operation in the input section 5, thereby inputting or selecting parameter values ​​for each item of the measurement conditions. Furthermore, for example, if default values ​​are preset, these default values ​​can be appropriately changed (step S2). Thus, the filling... Figure 5 The values ​​shown in the table represent the measurement conditions. The set parameter values ​​are associated with the identification codes (here [1], [2], ...) used to determine the measurement conditions and are registered in the measurement condition storage unit 40.

[0045] Furthermore, if the measurement is performed directly using the measurement conditions already registered in the measurement condition storage unit 40, steps S1 and S2 can of course be omitted.

[0046] Subsequently, when the user instructs the dark field measurement to begin in the input unit 5, the control unit 4 closes the shutter 26 via the shutter drive unit 28, thereby blocking the light incident on the beam splitter. Then, in the light-blocking state, a dark field measurement (step S3) is performed to obtain dark field measurement values ​​for each measurement condition.

[0047] As is well known, in dark-field measurements, light is typically blocked to prevent light from incident on the photodetector (and sometimes the light source is turned off in spectrophotometers with a built-in light source), and the output signal of the photodetector is obtained. Of course, the output signal is affected by the integration time or gain of the photodetector, so under different integration times or gains, dark-field measurements must be performed for each integration time and gain to obtain the dark-field measurement value. The operation is the same when using the spectrometer of this embodiment. Since there is a possibility that the cumulative value or gain may differ under different measurement conditions (or the same situation may exist), it is necessary to determine the dark-field measurement value for each measurement condition.

[0048] On the other hand, regarding the set wavelength included in the measurement conditions, since the light entering the spectrometer is already blocked to prevent light from reaching the detector, the original set wavelength should not affect the dark-field measurement value. Therefore, in the past, when performing dark-field measurements corresponding to each measurement condition, the position of the diffraction grating was fixed at the state before the dark-field measurement. However, as mentioned earlier... Figure 6 As shown, the inventors conducted experiments and found that the dark field measurement value is significantly affected by the set wavelength, i.e., the rotation position of the diffraction grating 22. According to... Figure 6 If the set wavelength is increased, the dark field measurement value increases significantly. The reason is presumed to be as follows.

[0049] The spectrophotometer detection unit 2 includes a drive mechanism that rotates the diffraction grating 22. As is well known, such drive mechanisms utilize various optical sensors, such as optical position sensors or rotary encoders. These optical sensors include light sources such as light-emitting diodes (LEDs), and even when housed within a casing, it is difficult to completely eliminate light leaking from the casing. If light from such optical sensors leaks into the casing of the spectrophotometer detection unit 2, it may be reflected by various surfaces of the diffraction grating 22, including the grating surface, and ultimately reach the detector 25 as stray light. In this case, the intensity of the stray light reaching the detector 25 varies depending on the rotational position of the diffraction grating 22, i.e., the set wavelength at that moment.

[0050] Since the effects of light leakage from the optical sensor, as described above, are not significant, they are generally not a problem in most cases. However, in measurements requiring high precision, it is desirable to reflect the differences in dark-field measurement values, which depend on the set wavelength, as strictly as possible in the spectrum. Therefore, in the aforementioned spectrometer, the characteristic controls described below are implemented during dark-field measurements. Figure 4 This is a flowchart of the dark field measurement process in the spectrometer of this embodiment.

[0051] In the spectrometer of this embodiment, when the control unit 4 starts dark-field measurement, it first controls the shutter drive unit 28 to close the shutter 26 (step S30). This blocks the introduction of external light into the spectrophotometer 2. Next, the control unit 4 initially sets the measurement condition number (identification code) n to 1 (step S31) and retrieves the parameter value corresponding to the measurement condition [n], i.e., measurement condition [1], from the measurement condition storage unit 40 (step S32).

[0052] The control unit 4 controls the diffraction grating rotation drive unit 27 to rotate the diffraction grating 22 to a rotation position corresponding to the set wavelength a in the measurement conditions [1] (step S33). Then, the control unit 4 performs dark-field measurement under parameter values ​​other than the set wavelength in the measurement conditions [1], and the detector 25 acquires the dark-field measurement value (step S34). The dark-field measurement value at this time is a dark spectrum with a specified wavelength width corresponding to the set wavelength. The data processing unit 3 establishes a correspondence between the acquired dark-field measurement value and the measurement conditions [1] and saves it in the dark-field measurement value storage unit 31 (step S35).

[0053] Next, the control unit 4 increments the value of n (step S36) and determines whether the measurement condition [n] is registered in the measurement condition storage unit 40 (step S37). First, when performing the processing of steps S36 and S37, n is updated from 1 to 2, and it is determined whether the measurement condition [2] is registered in the measurement condition storage unit 40. Here, if the measurement condition is registered, the process returns from step S37 to step S32, and the parameter values ​​of each item in the measurement condition [2] are obtained from the measurement condition storage unit 40. Then, the processing of steps S33 to S37 is performed in the manner described above, thereby saving the dark field measurement value corresponding to the measurement condition [2] in the dark field measurement value storage unit 31.

[0054] When the dark field measurement values ​​related to all the pre-registered measurement conditions [n] are obtained through repeated implementation of steps S32 to S37, a "No" condition is determined in step S37, and the dark field measurement ends. Thus, for all the pre-registered measurement conditions, dark field measurement values ​​reflecting the rotational position of the diffraction grating 22 corresponding to each set wavelength can be obtained. That is, values ​​such as... Figure 6 The values ​​shown are high-precision dark-field measurements that vary depending on the set wavelength.

[0055] When the dark field measurement is completed and the dark field measurement value is saved in the dark field measurement value storage unit 31, the measurement of the target light, i.e., the formal measurement, is then performed (step S4). During the formal measurement, the optical fiber used to input the target light is equipped with the optical input connector 10. When the formal measurement begins, the control unit 4 obtains the parameter values ​​of the selected measurement conditions from the measurement condition storage unit 40. Then, the diffraction grating rotation drive unit 27 is operated to rotate the diffraction grating 22 to a position corresponding to the set wavelength included in the measurement conditions. As a result, the diffraction surface of the diffraction grating 22 is at a predetermined angle relative to the first concave mirror 21. When the target light, such as laser light, passes through the optical fiber and is introduced into the device, the target light is focused by the guiding optical system 11, passes through the entrance slit 20, and is introduced into the spectrophotometer detection unit 2.

[0056] In the spectrophotometer 2, the light to be measured reaches the first concave mirror 21 and is reflected, traveling towards the diffraction surface of the diffraction grating 22. At this time, the light to be measured is approximately parallel. The light to be measured reaching the diffraction surface of the diffraction grating 22 is wavelength-dispersed and sent to the second concave mirror 24. The wavelength-dispersed light reaching the second concave mirror 24 converges and is reflected, reaching each light-receiving element of the detector 25. Light with different wavelengths within a specified wavelength width reaches each light-receiving element of the detector 25. Each light-receiving element outputs a detection signal corresponding to the intensity of the incident light. The detection signal corresponds to the spectrum of light within the specified wavelength width.

[0057] In the data processing unit 3, the spectral data storage unit 30 sequentially stores the acquired spectral data. Furthermore, the arithmetic processing unit 32 performs correction processing on each wavelength based on the acquired spectral data, using the dark-field measurement values ​​stored in the dark-field measurement value storage unit 31, thereby calculating the dark-field corrected spectral data. The display processing unit 33 generates a spectrum based on the dark-field corrected spectral data and displays it on the screen of the display unit 6 via the control unit 4. Thus, the spectrum of the incident measured light can be displayed on the screen of the display unit 6 in real time.

[0058] Furthermore, when performing spectroscopic measurements sequentially according to different measurement conditions, the diffraction grating 22 is rotated in a stepped manner corresponding to the set wavelength included in the measurement conditions. At the position where the diffraction grating 22 is temporarily stopped, the detector 25 acquires spectral data of a specified wavelength width, and the above operation can be repeated.

[0059] The apparatus described in this embodiment can be modified appropriately. For example, Figure 5 The measurement conditions shown include at least the set wavelength, and may include any one of the integration time, gain, or number of accumulations.

[0060] The beam splitter is not limited to the Cheney-Turner type; any beam splitter with a structure that can change the measurement wavelength by rotating the diffraction grating is acceptable. Furthermore, the position of shutter 26 is not limited to... Figure 2 The position shown is ideally designed to minimize the amount of external light entering the beam-splitting detection unit 2 when the light is blocked. Furthermore, an optical or electronic shutter that achieves the same light-blocking effect can be used instead of a mechanically operated shutter.

[0061] Furthermore, while the apparatus described in the above embodiment assumes a structure that uses a spectrometer to disperse and detect the wavelength of light (the light to be measured) introduced via an optical fiber, the present invention can also be applied to spectrophotometers used to obtain the absorption or reflection spectrum, or fluorescence spectrum, of a sample. In other words, the present invention can be applied to any apparatus that includes a spectrometer with a structure that rotates a diffraction grating to change the wavelength or wavelength range of the object being measured.

[0062] Furthermore, the embodiments or their variations are merely examples of the present invention. For aspects other than the variations, it is understood that even appropriate modifications, alterations, or additions made within the scope of the spirit of the present invention are included within the scope of the claims of this application.

[0063] [Various forms]

[0064] Those skilled in the art will understand that the exemplary embodiments described are specific examples of the following forms.

[0065] (First item) One aspect of the spectrophotometer of the present invention includes:

[0066] The beam-splitting section includes a diffraction grating;

[0067] The detection unit detects light whose wavelength is dispersed as it passes through the diffraction grating;

[0068] The rotating part causes the diffraction grating to rotate;

[0069] A light-shielding section blocks the light to be measured from entering the beam-splitting section.

[0070] The measurement condition setting unit sets multiple sets of measurement conditions, including at least one parameter value from the wavelength of the measurement object and integration time, gain, or number of data accumulations; and

[0071] The control unit is used to acquire the dark field measurement value of each of the multiple measurement conditions set in the measurement condition setting unit, and to block the measured light by the light shielding unit. Under each measurement condition, the control unit rotates the diffraction grating to a position corresponding to the wavelength of the measurement object included in the measurement condition, and then performs dark field measurement under other parameter values ​​included in the measurement condition.

[0072] Using the spectrophotometer described in the first item, it is possible to determine with good accuracy, such as... Figure 6 The dark field measurement values ​​shown vary depending on the set wavelength, i.e., the position of the diffraction grating. Therefore, not only parameters such as integration time can be obtained, but also high-precision dark field measurement values ​​corresponding to the wavelength of each measured object can be obtained. Using these measurement values, dark field correction can be performed with good accuracy within any wavelength or wavelength range, thereby obtaining high-precision light intensity or spectrum.

[0073] (Second item) In the spectrophotometer described in the first item, the detection unit may be a multi-channel type detection unit with multiple light receiving elements arranged in the wavelength dispersion direction, and may be able to simultaneously acquire the light intensity distribution of the wavelength width corresponding to the wavelength of the object being measured.

[0074] In the spectrophotometer described in the second item, with the diffraction grating fixed at a certain rotational position, the intensity distribution of light across a specified wavelength width, i.e., the spectrum, can be obtained immediately. Thus, the spectrum of the light being measured can be observed in real time.

[0075] [Explanation of Symbols]

[0076] 1: Importing the optical system

[0077] 10: Optical input connector

[0078] 11: Guiding Optical System

[0079] 2: Spectrophotometer

[0080] 20: Entrance slit

[0081] 21: First concave mirror

[0082] 22: Diffraction grating

[0083] 24: Second concave mirror

[0084] 25: Detector

[0085] 26: Shutter

[0086] 27: Diffraction grating rotation drive unit

[0087] 28: Shutter drive unit

[0088] 3: Data Processing Department

[0089] 30: Spectral Data Storage Department

[0090] 31: Dark Field Measurement Value Storage Unit

[0091] 32: Computation and Processing Unit

[0092] 33: Display Processing Unit

[0093] 4: Control Department

[0094] 40: Measurement Conditions Storage Section

[0095] 5: Input Section

[0096] 6: Display section.

Claims

1. A spectrophotometer, comprising: The beam-splitting section includes a diffraction grating; The detection unit detects light whose wavelength is dispersed as it passes through the diffraction grating; The rotating part causes the diffraction grating to rotate; A light-shielding section blocks the light to be measured from entering the beam-splitting section. The measurement condition storage unit stores multiple measurement conditions, each of which includes setting at least one parameter value from a set of parameters, including the wavelength and integration time of the measurement object, gain, or number of data accumulations; and The control unit is used to acquire dark field measurement values ​​for each of the plurality of measurement conditions, and to block the measured light by means of the light-shielding unit. Under each measurement condition, the control unit rotates the diffraction grating to a position corresponding to the wavelength of the measurement object included in the measurement condition, and then performs dark field measurement under other parameter values ​​included in the measurement condition.

2. The spectrophotometer according to claim 1, wherein, The detection unit is a multi-channel type detection unit with multiple light receiving elements arranged in the wavelength dispersion direction, and it can simultaneously acquire the light intensity distribution of the wavelength width corresponding to the wavelength of the object being measured.

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