Spectrophotometer

Abstract

This spectrometry device comprises: a light incident part; a reflective diffraction grating; a photodetector; a lens; and an analysis unit. The photodetector receives a spectral image at a first light receiving region in a first exposure time so as to output first spectrum data of measured light, and receives a spectral image at a second light receiving region, arranged parallel to the first light receiving region, in a second exposure time which is longer than the first exposure time, so as to output second spectral data of measured light. The analysis unit generates spectral data on the basis of the first spectral data and the second spectral data. The photodetector is disposed so that a stray light region, where stray light is condensed, is located in the first light receiving region.

Description

[Technical Field]

[0001] The present disclosure relates to a spectroscopic measurement device. [Background technology]

[0002] There is known a spectroscopic measurement device that includes a light incident section that receives light to be measured, a reflective diffraction grating that separates the light to be measured incident from the light incident section, a photodetector that detects the light to be measured separated by the reflective diffraction grating, and a lens that guides the light to be measured incident from the light incident section to the reflective diffraction grating and forms a spectral image of the light to be measured separated by the reflective diffraction grating in a light receiving area of ​​the photodetector (see, for example, Patent Document 1). A spectroscopic measurement device that employs such an optical system (called a Dyson optical system) has the advantage of improving wavelength resolution in measuring the light to be measured.

[0003] On the other hand, spectroscopic measurement devices using Dyson optical systems have the disadvantage of being prone to stray light, and unless some countermeasures are taken, the detection accuracy of the light being measured is likely to decrease. For example, in spectroscopic measurement devices using Dyson optical systems, a portion of the light being measured is likely to be multiple-reflected within the lens, resulting in the appearance of a stray light region (a region where stray light gathers). One possible countermeasure is to increase the distance between the light incident part and the photodetector so that the stray light region is not located in the light receiving area of ​​the photodetector. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] US Patent Application Publication No. 2009 / 0237657 Summary of the Invention [Problem to be solved by the invention]

[0005] However, if the distance between the light incident portion and the photodetector is increased, the aberration caused by the lens increases, which may result in a decrease in wavelength resolution in measuring the light to be measured.

[0006] An object of the present disclosure is to provide a spectroscopic measurement device that can suppress both a decrease in wavelength resolution and a decrease in detection accuracy when measuring light to be measured. [Means for solving the problem]

[0007] A spectroscopic measurement device according to one aspect of the present disclosure includes: [1] a light incident unit that incidents light to be measured; a reflective diffraction grating that spectrally separates the light to be measured incident from the light incident unit; a photodetector that detects the light to be measured dispersed by the reflective diffraction grating; a lens that guides the light to be measured incident from the light incident unit to the reflective diffraction grating and forms a spectral image of the light to be measured dispersed by the reflective diffraction grating on a light receiving area of ​​the photodetector; and an analyzer that generates spectral data of the light to be measured, wherein the light receiving area includes a first light receiving area including a plurality of first photodetection channels arranged in a direction parallel to a wavelength axis of the spectral image; and an analyzer that is juxtaposed with the first light receiving area in a direction perpendicular to the wavelength axis and that is arranged in the direction parallel to the wavelength axis. and a second light-receiving region including a plurality of second light detection channels arranged in a manner similar to that of the first light-receiving region, wherein the photodetector outputs first spectral data of the light to be measured by receiving the spectral image in the first light-receiving region for a first exposure time, and outputs second spectral data of the light to be measured by receiving the spectral image in the second light-receiving region for a second exposure time longer than the first exposure time, the analysis unit generates the spectral data based on the first spectral data and the second spectral data output from the photodetector, and the photodetector is arranged so that a stray light region where stray light generated in the optical path from the light incident unit to the photodetector gathers is located in the first light-receiving region.

[0008] In the spectroscopic measurement device described in [1] above, the light-receiving region of the photodetector has a first light-receiving region and a second light-receiving region arranged side by side in a direction perpendicular to the wavelength axis of the spectral image, and the photodetector is arranged so that a stray light region, where stray light generated in the optical path from the light incident unit to the photodetector gathers, is located in the first light-receiving region. This reduces aberrations caused by the lens and suppresses deterioration of wavelength resolution in measuring the light under measurement, compared to when the distance between the light incident unit and the photodetector is increased so that the stray light region is not located in the light-receiving region of the photodetector. Furthermore, in the spectroscopic measurement device described in [1] above, the photodetector receives a spectral image in the first light-receiving region for a first exposure time to output first spectral data of the light under measurement, and receives a spectral image in the second light-receiving region for a second exposure time longer than the first exposure time to output second spectral data of the light under measurement, and the analyzer generates spectral data of the light under measurement based on the first spectral data and the second spectral data. As a result, in generating spectral data of the light to be measured, the wavelength band corresponding to the stray light region is offset from the wavelength band with high light intensity, and the first spectral data is used for the wavelength band with high light intensity and the second spectral data is used for the wavelength band with low light intensity, thereby making it possible to suppress a decrease in detection accuracy in measuring the light to be measured.As described above, the spectroscopic measurement device described in [1] above makes it possible to suppress both a decrease in wavelength resolution and a decrease in detection accuracy in measuring the light to be measured.

[0009] A spectroscopic measurement device according to one aspect of the present disclosure may be the spectroscopic measurement device according to [2] above, wherein "the analyzer generates the spectral data based on data of the first spectral data in a wavelength band that does not include a wavelength band corresponding to the stray light region and data of the second spectral data in a wavelength band that includes the wavelength band corresponding to the stray light region." In the spectroscopic measurement device according to [2], stray light is detected in the wavelength band corresponding to the stray light region in the first spectral data. On the other hand, stray light is not detected in the wavelength band corresponding to the stray light region in the second spectral data. Therefore, the spectroscopic measurement device according to [2] can further suppress a decrease in detection accuracy in measuring the light to be measured by eliminating the influence of stray light from the first spectral data and supplementing the data of the excluded wavelength band with the second spectral data.

[0010] The spectroscopic measurement device according to one aspect of the present disclosure may be [3] "the spectroscopic measurement device according to the above [1] or [2], wherein the photodetector is offset to one side in the direction perpendicular to the wavelength axis with respect to the light incident portion." According to the spectroscopic measurement device according to [3], it is possible to easily and reliably realize the arrangement of the photodetector so as to position the stray light region in the first light receiving region.

[0011] The spectroscopic measurement device according to one aspect of the present disclosure may be [4] "the spectroscopic measurement device according to any one of [1] to [3] above, wherein the stray light is generated by multiple reflections of a portion of the light to be measured within the lens." The appearance of the stray light region is primarily caused by multiple reflections of a portion of the light to be measured within the lens. According to the spectroscopic measurement device according to [4], by eliminating the influence of the stray light region, it is possible to further suppress a decrease in detection accuracy in measuring the light to be measured.

[0012] The spectroscopic measurement device according to one aspect of the present disclosure may be [5] "the spectroscopic measurement device according to any one of [1] to [4] above, further including a mask member disposed between the lens and the photodetector to block the stray light." According to the spectroscopic measurement device according to [5], the influence of the stray light region can be eliminated by blocking the stray light from entering the photodetector. Therefore, it is possible to further suppress a decrease in detection accuracy in measuring the light to be measured.

[0013] The spectroscopic measurement device according to one aspect of the present disclosure may be [6] "the spectroscopic measurement device according to any one of the above [1] to [5], wherein the lens is a convex lens having a surface facing the light incident portion and the photodetector, and a convex surface facing the reflective diffraction grating." According to the spectroscopic measurement device described in [6], the light to be measured incident from the light incident portion can be guided to the reflective diffraction grating, and a spectral image of the light to be measured dispersed by the reflective diffraction grating can be formed in the light receiving region of the photodetector. [Effects of the Invention]

[0014] According to the present disclosure, it is possible to provide a spectroscopic measurement device that can suppress both a decrease in wavelength resolution and a decrease in detection accuracy in measuring light to be measured. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a diagram showing the configuration of a spectroscopic measurement device according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the configuration of the photodetector shown in FIG. [Figure 3] FIG. 3 is a diagram showing the first spectral data and the second spectral data. [Figure 4] FIG. 4 is a diagram showing the spectrum data of the light under measurement. [Figure 5] FIG. 5 is a diagram showing the configuration of a photodetector according to the first modified example. [Figure 6] FIG. 6 is a diagram showing the configuration of a photodetector according to the second modified example and the spectrum data of the light to be measured. DETAILED DESCRIPTION OF THE INVENTION

[0016] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. In each drawing, the same or corresponding parts are denoted by the same reference numerals, and duplicated explanations will be omitted. [Configuration of spectroscopic measurement equipment]

[0017] 1, the spectroscopic measurement device 1 includes a light incident unit 2, a reflective diffraction grating 3, a photodetector 4, a lens 5, and an analyzing unit 6. The spectroscopic measurement device 1 is a device that generates spectral data of the measured light L1 by dispersing the measured light L1.

[0018] The light incident section 2, the reflective diffraction grating 3, and the lens 5 constitute an optical system (a so-called Dyson optical system) that guides the light to be measured L1 to the light receiving area 40 of the photodetector 4 and forms a spectral image α of the light to be measured L1 on the light receiving area 40 of the photodetector 4 along the wavelength axis A. The light to be measured L1 is split by the reflective diffraction grating 3 in a direction perpendicular to the direction in which the light to be measured L1 is incident. Here, the direction in which the light to be measured L1 is split (i.e., the direction parallel to the wavelength axis A) is referred to as the X-axis direction, the direction perpendicular to the X-axis direction is referred to as the Y-axis direction, and the direction perpendicular to the X-axis and Y-axis directions is referred to as the Z-axis direction.

[0019] The light incident unit 2 is arranged to allow the measured light L1 to enter the spectroscopic measurement device 1. The light incident unit 2 adjusts the amount of incident light L1. The light incident unit 2 is, for example, a slit member. When viewed from the Y-axis direction, the slit formed in the slit member has a rectangular opening with its short side in the X-axis direction and its long side in the Z-axis direction. Increasing the width of the short side increases the amount of incident light L1, thereby obtaining spectral data with less noise but lower wavelength resolution in the analysis unit 6. On the other hand, narrowing the width of the short side reduces the amount of incident light L1, thereby improving wavelength resolution but obtaining spectral data with more noise in the analysis unit 6. The light incident unit 2 may be, for example, a slit member and an optical fiber that transmits the measured light L1 to the slit member. Alternatively, the light incident unit 2 may be, for example, a slit member and a lens that focuses the measured light L1 from outside the slit member.

[0020] The reflective diffraction grating 3 faces the light incident portion 2 in the Y-axis direction. The reflective diffraction grating 3 splits the light to be measured L1 in the direction opposite to the direction in which the light to be measured L1 is incident. The reflective diffraction grating 3 is composed of multiple grating grooves (not shown). The multiple grating grooves are aligned along the X-axis direction, which is perpendicular to the direction in which the light to be measured L1 is incident, and extend along the Z-axis direction, which is perpendicular to the alignment direction. The light to be measured L1 that is incident on the reflective diffraction grating 3 is split according to its wavelength along the X-axis direction, which is the direction in which the multiple grating grooves are aligned.

[0021] The photodetector 4 faces the reflective diffraction grating 3 in the Y-axis direction. In this embodiment, the photodetector 4 is positioned at the same position as the light incident unit 2 in the Y-axis direction. The photodetector 4 is positioned at a certain distance D from the light incident unit 2 in the Z-axis direction, on the side where the dispersed light to be measured L1 is incident. In other words, the photodetector 4 is offset from the light incident unit 2 in a direction perpendicular to the wavelength axis A (the Z-axis direction) toward the side where the dispersed light to be measured L1 is incident. The photodetector 4 detects the light to be measured L1 dispersed by the reflective diffraction grating 3. In this embodiment, the photodetector 4 is a CCD image sensor formed on a semiconductor substrate. The CCD image sensor may be any of an interline type, a frame transfer type, and a full frame transfer type.

[0022] The lens 5 is disposed between the light incident section 2 and the photodetector 4 and the reflective diffraction grating 3 in the Y-axis direction. The lens 5 guides the light to be measured L1 incident from the light incident section 2 to the reflective diffraction grating 3, and forms a spectral image α of the light to be measured L1 dispersed by the reflective diffraction grating 3 in the light-receiving region 40 of the photodetector 4. The lens 5 is a convex lens having a surface 5a and a convex surface 5b opposite to the surface 5a. The surface 5a faces the light incident section 2 and the photodetector 4. The surface 5a is a flat surface, a concave surface, or a convex surface. The convex surface 5b faces the reflective diffraction grating 3 and is a surface curved in a convex shape opposite to the surface 5a.

[0023] The analysis unit 6 generates spectral data S3 of the measured light L1 based on the data acquired from the photodetector 4. The details of the analysis by the analysis unit 6 will be described later. The analysis unit 6 includes a storage unit that stores the data acquired from the photodetector 4, the analysis results, etc. The analysis unit 6 may also control the photodetector 4. The analysis unit 6 may be a computer or tablet terminal equipped with a processor such as a CPU (Central Processing Unit) and a storage medium such as a RAM (Random Access Memory) or a ROM (Read Only Memory). The analysis unit 6 may also be configured with a microcomputer or FPGA (Field Programmable Gate Array).

[0024] In the spectroscopic measurement device 1 configured as described above, the light to be measured L1 incident from the light incident unit 2 is incident on the surface 5a at a certain angle of incidence. The light to be measured L1 incident on the surface 5a is refracted at the surface 5a in accordance with the difference between the refractive index of air and the refractive index of the lens 5, travels inside the lens 5, and emerges from the convex surface 5b. The light to be measured L1 emerging from the convex surface 5b is refracted at the convex surface 5b in accordance with the difference between the refractive index of the lens 5 and the refractive index of air, and is guided to the reflective diffraction grating 3 in the subsequent stage.

[0025] The light to be measured L1 dispersed by the reflective diffraction grating 3 is incident on the lens 5 again. The dispersed light to be measured L1 is incident on the convex surface 5b of the lens 5 at a fixed angle of incidence. The dispersed light to be measured L1 incident on the convex surface 5b is refracted by the convex surface 5b in accordance with the difference between the refractive index of air and the refractive index of the lens 5, travels inside the lens 5, and emerges from the surface 5a. The dispersed light to be measured L1 emerging from the surface 5a is refracted by the surface 5a in accordance with the difference between the refractive index of the lens 5 and the refractive index of air, and is imaged on the downstream photodetector 4, forming a spectral image α on the light-receiving area 40.

[0026] Here, stray light may occur along the optical path from the light incident unit 2 to the photodetector 4. For example, stray light L2 may be generated by multiple reflections of a portion of the measured light L1 within the lens 5. For example, a portion of the measured light L1 incident from the light incident unit 2 or a portion of the measured light L1 dispersed by the reflective diffraction grating 3 may be multiple-reflected between the surface 5a and the convex surface 5b and emitted from the surface 5a as stray light L2. The stray light L2 may appear as an unnatural peak in the spectral data. Increasing the distance D of the photodetector 4 can prevent the stray light L2 from entering the photodetector 4. However, increasing the distance D increases the shift in the imaging position due to differences in wavelength, resulting in a decrease in wavelength resolution. In this embodiment, the distance D is set so that the region where the stray light L2 gathers (stray light region β) is located in the first light-receiving region 41 of the light-receiving region 40 of the photodetector 4. [Photodetector configuration]

[0027] As shown in FIG. 2, the light-receiving region 40 of the photodetector 4 is divided into a first light-receiving region 41 and a second light-receiving region 42. The first light-receiving region 41 and the second light-receiving region 42 are arranged side by side along the Z-axis direction, which is perpendicular to the wavelength axis A. In the first light-receiving region 41, the photodetector 4 has a plurality of first light-detecting channels 41a arranged along the X-axis direction, which is parallel to the wavelength axis A. Similarly, in the second light-receiving region 42, the photodetector 4 has a plurality of second light-detecting channels 42a arranged along the X-axis direction, which is parallel to the wavelength axis A. Each of the light-detecting channels 42a and 42b is composed of a plurality of pixels arranged along the Z-axis direction. The photodetector 4 receives a spectral image α in the first light-receiving region 41 during a first exposure time, and outputs first spectral data S1 of the measured light L1 for each of the plurality of first light-detecting channels 41a. At the same time, the photodetector 4 receives the spectral image α in the second light-receiving area 42 for a second exposure time, thereby outputting second spectral data S2 of the measured light L1 for each of the multiple second light detection channels 42a. The second exposure time is longer than the first exposure time. The spectral image α formed on the light-receiving area 40 has a wavelength axis A extending in the X-axis direction, and an image for each wavelength extending in the Z-axis direction. The spectral image α has a shape that is symmetrical up and down with the boundary line between the first light-receiving area 41 and the second light-receiving area 42 as the axis of symmetry.

[0028] The output of the first spectral data S1 will be described in more detail. In the first light-receiving region 41, the charges generated and accumulated in the multiple pixels included in each first photodetection channel 41a are transferred to a first horizontal shift register (not shown). The accumulated charges are then summed for each first photodetection channel 41a in the first horizontal shift register (hereinafter, this operation will be referred to as "vertical transfer"). The charges summed for each first photodetection channel 41a in the first horizontal shift register are then sequentially read out from the first horizontal shift register (hereinafter, this operation will be referred to as "horizontal transfer"). A voltage value corresponding to the amount of charge read out from the first horizontal shift register is output from a first amplifier (not shown), and the voltage value is AD-converted by an AD converter to a digital value. In this manner, the first spectral data S1 is output.

[0029] The output of the second spectral data S2 will be described in more detail. In the second light-receiving region 42, the charges generated and accumulated in the multiple pixels included in each second photodetection channel 42a are transferred to a second horizontal shift register (not shown). The accumulated charges are then added together for each second photodetection channel 42a in the second horizontal shift register (vertical transfer). The charges added together for each second photodetection channel 42a in the second horizontal shift register are then sequentially read out from the second horizontal shift register (horizontal transfer). A voltage value corresponding to the amount of charge read out from the second horizontal shift register is then output from a second amplifier (not shown), and the voltage value is AD-converted by an AD converter to a digital value. In this manner, the second spectral data S2 is output.

[0030] In the photodetector 4, the second exposure time in the second light-receiving region 42 is longer than the first exposure time in the first light-receiving region 41. The exposure time of each region can be set, for example, by an electronic shutter. The electronic shutter can be realized by using an anti-blooming gate (ABG).

[0031] A stray light region β formed by the stray light L2 is located in the first light-receiving region 41. Specifically, the distance D between the light incident unit 2 and the photodetector 4 in the Z-axis direction is set so that the stray light region β is located in the first light-receiving region 41. Here, the distance D is set so that the stray light region β is not located in the second light-receiving region 42. In other words, the photodetector 4 is positioned so that the stray light region β, where the stray light L2 generated in the lens 5 is located, is located in the first light-receiving region 41 but not in the second light-receiving region 42. Furthermore, because the stray light L2 is generated within the lens 5, the position of the stray light region β is adjusted by also adjusting the positional relationship between the lens 5 and the photodetector 4. Therefore, in the first spectral data S1, stray light L2 is detected in the wavelength band Δλ corresponding to the stray light region β. On the other hand, in the second spectral data S2, stray light L2 is not detected in the wavelength band Δλ corresponding to the stray light region β. 2, the stray light region β is an ellipse having a minor axis in the Z-axis direction and a major axis in the X-axis direction, and the length of the minor axis is longer than the length of the first light receiving region 41 in the Z-axis direction. Therefore, a part of the stray light region β is located in the first light receiving region 41. [Method for generating spectral data of measured light]

[0032] As shown in FIG. 3( a), the first spectral data S1 was acquired in the first light-receiving region 41 with a short exposure time. The analysis unit 6 was able to acquire light intensities in all wavelength bands without saturating each pixel in any wavelength band. In contrast, as shown in FIG. 3( b), the second spectral data S2 was acquired in the second light-receiving region 42 with a long exposure time. The second spectral data S2 includes wavelength bands in which each pixel is saturated. Therefore, the analysis unit 6 was unable to accurately acquire light intensities in wavelength bands in which each pixel is saturated. On the other hand, the first spectral data S1 contains noise in wavelength bands with low light intensity, resulting in a poor S / N ratio. The second spectral data S2 does not contain noise even in wavelength bands with low light intensity, allowing for highly accurate data to be acquired.

[0033] In the first spectral data S1, stray light L2 is detected in a wavelength band Δλ corresponding to the stray light region β. The stray light L2 is detected as bump-like data in the first spectral data S1. In the first spectral data S1, the wavelength band Δλ corresponding to the stray light region β is offset from the wavelength band with high light intensity. In other words, the wavelength band Δλ corresponding to the stray light region β is adjusted so as not to overlap with the wavelength band with high light intensity. As an adjustment means, for example, the position of the stray light region β on the first light receiving region 41 is moved along the wavelength axis A.

[0034] The analysis unit 6 sets a threshold Th1 in the first spectral data S1, the threshold Th1 being a light intensity higher than the light intensity of the stray light L2. The analysis unit 6 classifies the portion of the first spectral data S1 that is equal to or greater than the threshold Th1 as data S11, and classifies the portion below the threshold Th1 as data S12. In other words, the data S11 is data in the first spectral data S1 for a wavelength band that does not include the wavelength band Δλ corresponding to the stray light region β. The data S12 is data in the first spectral data S1 for a wavelength band that includes the wavelength band Δλ corresponding to the stray light region β. Therefore, data in which the stray light L2 is detected is included in the data S12. Furthermore, data in wavelength bands with low light intensity is included in the data S12. Meanwhile, the analysis unit 6 sets a threshold Th2 in the second spectral data S2, the threshold Th2 being a light intensity higher than the light intensity of the stray light L2. The analysis unit 6 classifies the portion of the second spectral data S2 that is equal to or greater than the threshold Th2 as data S21, and classifies the portion below the threshold Th2 as data S22. In other words, data S21 is data on a wavelength band of the second spectral data S2 that does not include the wavelength band Δλ corresponding to the stray light region β. Data S22 is data on a wavelength band of the second spectral data S2 that includes the wavelength band Δλ corresponding to the stray light region β. Data on the wavelength band in which each pixel is saturated is included in data S21. Note that the analyzer 6 may set the portion of the first spectral data S1 that exceeds a threshold Th1 as data S11 and the portion equal to or less than the threshold Th1 as data S12. Alternatively, the analyzer 6 may set the portion of the second spectral data S2 that exceeds a threshold Th2 as data S21 and the portion equal to or less than the threshold Th2 as data S22.

[0035] 4, the analysis unit 6 generates third spectral data (spectral data of the measured light L1) S3 based on the first spectral data S1 and the second spectral data S2. Specifically, the analysis unit 6 generates the third spectral data S3 by splicing together data S11 and S22. The analysis unit 6 first excludes data S12 from the first spectral data S1. Then, the analysis unit 6 extracts data S22 from the second spectral data S1 and splices it into data S11 so as to complement the excluded data S12 with the data S22. In generating the third spectral data S3, the analysis unit 6 does not use data S12 including data in which stray light L2 is detected. Therefore, data in which stray light L2 is detected is excluded from the third spectral data S3. Furthermore, the analysis unit 6 does not use data S21 in generating the third spectral data S3. Therefore, in the third spectral data S3, the pixels are not saturated in all wavelength bands, and the light intensity can be acquired in all wavelength bands. [Action and effect]

[0036] In the spectroscopic measurement device 1, the light-receiving region 40 of the photodetector 4 has a first light-receiving region 41 and a second light-receiving region 42 arranged side by side in a direction perpendicular to the wavelength axis A of the spectral image α, and the photodetector 4 is arranged so that a stray light region β, where stray light L2 generated in the lens 5 gathers, is located in the first light-receiving region 41 but not in the second light-receiving region 42. This reduces the aberration caused by the lens 5 and suppresses a decrease in wavelength resolution in measuring the measured light L1, compared to when the distance D between the light incident unit 2 and the photodetector 4 is increased so that the stray light region β is not located in the light-receiving region 40 of the photodetector 4. Furthermore, in the spectroscopic measurement device 1, the photodetector 4 receives the spectral image α in the first light-receiving region 41 for a first exposure time to output first spectral data S1 of the measured light L1, and receives the spectral image α in the second light-receiving region 42 for a second exposure time longer than the first exposure time to output second spectral data S2 of the measured light L1. The analyzer 6 generates spectral data S3 of the measured light L1 based on the first spectral data S1 and the second spectral data S2. In this way, in generating the spectral data S3 of the measured light L1, the first spectral data S1 is used for the wavelength band with high light intensity and the second spectral data S2 is used for the wavelength band with low light intensity, while offsetting the wavelength band with high light intensity by the wavelength band Δλ corresponding to the stray light region β. This makes it possible to suppress a decrease in detection accuracy in measuring the measured light L1. As described above, the spectroscopic measurement device 1 can suppress a decrease in both wavelength resolution and detection accuracy in measuring the measured light L1.

[0037] In the spectroscopic measurement device 1, the analyzer 6 generates spectral data S3 based on data S11 of the first spectral data S1 for a wavelength band that does not include the wavelength band Δλ corresponding to the stray light region β, and data S22 of the second spectral data S2 for a wavelength band that includes the wavelength band Δλ corresponding to the stray light region β. In the spectroscopic measurement device 1, stray light L2 is detected in the wavelength band Δλ corresponding to the stray light region β in the first spectral data S1. On the other hand, stray light L2 is not detected in the wavelength band Δλ corresponding to the stray light region β in the second spectral data S2. Therefore, the spectroscopic measurement device 1 can eliminate the influence of stray light L2 from the first spectral data S1 while complementing the data of the excluded wavelength band with data S22 of the second spectral data S2, thereby further suppressing a decrease in detection accuracy in measuring the measured light L1.

[0038] In the spectroscopic measurement device 1, the photodetector 4 is offset to one side (the side onto which the dispersed measured light L1 is incident) in a direction perpendicular to the wavelength axis A with respect to the light incident part 2. This makes it possible to easily and reliably realize the arrangement of the photodetector 4 so as to position the stray light region β in the first light receiving region 41.

[0039] In the spectroscopic measurement device 1, the stray light L2 is generated in the lens 5, for example, when a part of the light to be measured L1 is multiple-reflected within the lens 5. The main cause of the appearance of the stray light region β is the multiple reflection of a part of the light to be measured L1 within the lens 5. This makes it possible to further suppress a decrease in detection accuracy in measuring the light to be measured L1 by eliminating the influence of the stray light region β.

[0040] In the spectroscopic measurement device 1, the lens 5 is a convex lens having a surface 5a facing the light incident part 2 and the photodetector 4, and a convex surface 5b facing the reflective diffraction grating 3. This allows the measured light L1 incident from the light incident part 2 to be guided to the reflective diffraction grating 3, and also allows a spectral image α of the measured light L1 dispersed by the reflective diffraction grating 3 to be formed in the light-receiving region 40 of the photodetector 4. [Variations]

[0041] The present disclosure is not limited to the above-described embodiment. As shown in FIG. 5 , a mask member 7 may be disposed between the lens 5 and the photodetector 4. In this case, the photodetector 4 is also disposed so that the stray light region β is located in the first light-receiving region 41 but not in the second light-receiving region 42. However, since the mask member 7 prevents the stray light L2 from entering the first light-receiving region 41, the stray light region β is not directly located in the first light-receiving region 41. By disposing the mask member 7, the stray light L2 is not detected in the first spectral data S1. This prevents the stray light L2 from entering the photodetector 4, thereby eliminating the influence of the stray light L2. Therefore, the decrease in detection accuracy in measuring the measured light L1 can be further suppressed. The mask member 7 is, for example, a light-shielding film. The size of the outer edge of the mask member 7 when viewed from the Y-axis direction is only required to be larger than the size of the outer edge of the stray light region β. The shape of the mask member 7 when viewed from the Y-axis direction is not limited to a rectangular shape, but may also be a circular, elliptical, or triangular shape.

[0042] As shown in FIG. 6, the mask member 7 may be used to correct the spectral sensitivity of the photodetector 4 in addition to masking the stray light L2. FIG. 6(a) shows a mask member 7a arranged on a light-receiving region 40a that is not divided into a first light-receiving region 41 and a second light-receiving region 42, for the purpose of correcting the spectral sensitivity. The mask member 7a is designed based on the characteristics of the spectral data shown in FIG. 6(b). The spectral data shown in FIG. 6(b) is data of the measured light L1 generated by the analysis unit 6 when the mask member 7a is not arranged on the light-receiving region 40a. The spectral data in FIG. 6(b) shows high light intensity in the central wavelength band (near 500 nm) of the measured light L1 and low light intensity in the low wavelength band (near 200 nm to 300 nm) and the high wavelength band (near 700 nm to 800 nm). The design concept of the mask member 7a is specifically as follows. The mask member 7a is designed not to be disposed in the low wavelength band (near 200 nm to 300 nm). The area of ​​the mask member 7a gradually increases from the wavelength band of 300 nm onwards, and is designed to be largest in the central wavelength band (near 500 nm). Furthermore, the mask member 7a is designed to gradually decrease in area from the central wavelength band (near 500 nm) in the high wavelength band (near 700 nm to 800 nm). In addition, the mask member 7a is designed to match the position of the stray light region β.

[0043] FIG. 6(c) shows the spectral data of the measured light L1 generated by the analyzer 6 when the mask member 7a is placed in the light-receiving region 40a. The spectral data in FIG. 6(c) exhibits the same characteristics as the spectral data in FIG. 6(b) in the low wavelength band (approximately 200 nm to 300 nm). However, the light intensity becomes constant in the wavelength band above 300 nm. This is due to the spectral sensitivity correction performed by the mask member 7a in FIG. 6(a). Furthermore, the mask member 7a prevents stray light L2 from entering the light-receiving region 40a. As a result, the stray light L2 is not detected in the spectral data after sensitivity correction. Therefore, by blocking the stray light L2 from entering the photodetector 4, the influence of the stray light L2 can be eliminated. Note that while the mask member 7a in FIG. 6(a) is divided into two parts, it may be a single piece or divided into three or more parts as long as it complies with the design concept described above.

[0044] The photodetector 4 may be a CMOS image sensor. In the case of a CMOS image sensor, each pixel has a photodiode (photoelectric conversion element) and an amplifier. The photodiode accumulates electrons (photoelectrons) generated by input photons as electric charges. The amplifier converts the electric charges accumulated in the photodiode into voltages and amplifies them. The amplified voltages are transferred to AD converters for each of the first and second photodetection channels 41a and 42a by switching the selection switches of each pixel. The amplified voltages are converted into digital values ​​by the AD converters and output as first and second spectral data S1 and S2.

[0045] The photodetector 4 may be a CCD-CMOS image sensor. In the case of a CCD-CMOS image sensor, the photodetector 4 has multiple signal readout circuits corresponding to the first photodetection channels 41a and the second photodetection channels 42a. Each signal readout circuit has a transistor and a signal output bonding pad. A voltage corresponding to the amount of charge transferred from each of the first photodetection channels 41a and the second photodetection channels 42a is applied to the control terminal of the transistor. A current having a magnitude corresponding to the voltage level is output from the output terminal of the transistor and extracted via the signal output bonding pad. The extracted current is converted into a digital value by an AD converter and output as the first spectral data S1 and the second spectral data S2.

[0046] Stray light L2 is not limited to being generated in the lens 5, but can be generated along the optical path from the light incident unit 2 to the photodetector 4. For example, stray light L2 can be generated between the light incident unit 2 and the lens 5, between the lens 5 and the reflective diffraction grating 3, or between the lens 5 and the photodetector 4. [Explanation of symbols]

[0047] 1...spectrometry device, 2...light incident section, 3...reflective diffraction grating, 4...photodetector, 5...lens, 5a...surface, 5b...convex surface, 6...analysis section, 7, 7a...mask member, 40...light receiving area, 41...first light receiving area, 41a...first light detection channel, 42...second light receiving area, 42a...second light detection channel, A...wavelength axis, L1...measured light, L2...stray light, S1...first spectral data, S2...second spectral data, S3...spectral data, α...spectral image, β...stray light area.

Claims

1. a light incident portion for incidenting light to be measured; a reflective diffraction grating that separates the light to be measured incident from the light incident portion; a photodetector that detects the measured light dispersed by the reflective diffraction grating; a lens that guides the light to be measured incident from the light incident portion to the reflective diffraction grating and forms a spectral image of the light to be measured dispersed by the reflective diffraction grating in a light receiving region of the photodetector; an analysis unit that generates spectral data of the light to be measured, The light receiving region is a first light receiving region including a plurality of first light detection channels arranged in a direction parallel to the wavelength axis of the spectral image; a second light receiving region that is juxtaposed with the first light receiving region in a direction perpendicular to the wavelength axis and includes a plurality of second photodetection channels that are arranged in the direction parallel to the wavelength axis; the photodetector receives the spectral image in the first light-receiving region for a first exposure time to output first spectral data of the light under measurement, and receives the spectral image in the second light-receiving region for a second exposure time longer than the first exposure time to output second spectral data of the light under measurement, the analyzer generates the spectral data based on the first spectral data and the second spectral data output from the photodetector; The photodetector is disposed so that a stray light region where stray light generated on the optical path from the light incident portion to the photodetector gathers is located in the first light receiving region.

2. 2. The spectroscopic measurement device according to claim 1, wherein the analysis unit generates the spectral data based on data of a wavelength band of the first spectral data that does not include a wavelength band corresponding to the stray light region, and data of a wavelength band of the second spectral data that includes the wavelength band corresponding to the stray light region.

3. The spectroscopic measurement device according to claim 1 , wherein the photodetector is offset to one side in the direction perpendicular to the wavelength axis with respect to the light incident portion.

4. The spectroscopic measurement device according to claim 1 , wherein the stray light is generated by multiple reflections of part of the light to be measured within the lens.

5. The spectroscopic measurement device according to claim 1 , further comprising a mask member disposed between the lens and the photodetector to block the stray light.

6. 3. The spectroscopic measurement device according to claim 1, wherein the lens is a convex lens having a surface facing the light incident portion and the photodetector, and a convex surface facing the reflective diffraction grating.

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