Spectroscopic apparatus, Raman spectroscopy measuring apparatus, and spectroscopic method

Abstract

This spectroscopy device 5 receives light L1, on which wavelength resolution in a prescribed direction has been performed by a spectroscopy optical system 4 including a spectroscopy element, and outputs spectroscopic spectrum data for the light L1, the spectroscopy device 5 comprising: a pixel unit 11 which has a plurality of pixels 21 that receive the wavelength resolved light L1 and convert the light L1 into electrical signals and in which the plurality of pixels 21 are arrayed in a row direction along the wavelength resolution direction and in a column direction perpendicular to the row direction; a conversion unit 12 which converts the electrical signals from the plurality of pixels 21 into photon numbers; and a generation unit 13 which integrates the photon numbers of the plurality of pixels 21 belonging to the same column and generates spectroscopic spectrum data based on the integration results.

Description

Technical Field

[0001] The present disclosure relates to a spectroscopic device, a Raman spectroscopic measurement device, and a spectroscopic method.

Background Art

[0002] As a conventional spectroscopic device, for example, there is a spectroscopic device described in Patent Document 1. This conventional spectroscopic device is a so-called Raman spectroscopic device. The spectroscopic device includes means for linearly irradiating excitation light, a movable stage on which a sample is placed, an objective lens for condensing Raman light from the excitation light irradiation region, a slit provided at the imaging position of the Raman light, a spectroscope for dispersing the light passing through the slit, a CCD detector for detecting a Raman spectrum image, and a control device for controlling mapping measurement by synchronizing the movable stage and the CCD detector.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the field of spectroscopic measurement that requires high sensitivity and high precision such as Raman spectroscopy, fluorescence spectroscopy, and plasma spectroscopy, in order to improve the signal-to-noise ratio, vertical binning of a CCD image sensor is used for acquiring spectroscopic spectrum data. Vertical binning in a CCD image sensor adds the charges generated in each pixel for a plurality of stages. In a CCD image sensor, read noise occurs only at the amplifier in the final stage and does not increase during the process of vertical binning. Therefore, as the number of stages of vertical binning increases, the signal-to-noise ratio can be improved.

[0005] In addition to CCDs, CMOS image sensors are also known as image sensors. However, currently, the adoption of CMOS image sensors in the field of spectroscopic measurement, where high sensitivity and high accuracy are required, has not progressed. In CMOS image sensors, an amplifier is placed in each pixel, and charge is converted into voltage for each pixel. When vertical binning is performed with conventional CMOS image sensors, the readout noise is accumulated as the number of vertical binning stages increases, resulting in a problem where the signal-to-noise ratio (SNR) of the signal is lower than when using a CCD image sensor.

[0006] This disclosure was made to solve the above-mentioned problems and aims to provide a spectrometer, a Raman spectrometer, and a spectroscopic method that can acquire spectral data with an excellent signal-to-noise ratio. [Means for solving the problem]

[0007] The gist of the spectroscopic apparatus, Raman spectroscopic measuring apparatus, and spectroscopic method relating to one aspect of this disclosure is as follows [1] to

[12] .

[0008] [1] A spectroscopic device that receives wavelength-decomposed light in a predetermined direction by a spectroscopic optical system including a spectroscopic element and outputs spectral data of the said light, comprising: a pixel section having a plurality of pixels that receive wavelength-decomposed light and convert it into an electrical signal, wherein the plurality of pixels are arranged in a row direction along the wavelength-decomposition direction and in a column direction perpendicular to the row direction; a conversion section that converts the electrical signals from the plurality of pixels into the number of photons; and a generation section that integrates the number of photons of a plurality of pixels belonging to the same column and generates spectral data based on the integration result.

[0009] This spectrometer converts the electrical signals output from each pixel into photon counts based on the light received by each pixel constituting the pixel area. During the conversion from electrical signals to photon counts, for example, pixels that did not receive light will have a photon count of zero. Therefore, when integrating the photon counts of multiple pixels belonging to the same column after the conversion to photon counts, the influence of readout noise from each pixel can be sufficiently reduced. Consequently, this spectrometer can acquire spectral data with an excellent signal-to-noise ratio.

[0010] [2] The spectroscopic apparatus according to [1], further comprising a selection unit for identifying a pixel to be used for photon number integration from among multiple pixels belonging to the same row. In this case, by identifying a pixel suitable for photon number integration, the influence of readout noise of each pixel can be reduced even more effectively. By reducing the influence of readout noise of each pixel, the accuracy of the conversion from electrical signals to photon numbers is improved, and the signal-to-noise ratio of the spectral data is further improved.

[0011] [3] The spectroscopic apparatus described in [2], wherein the identification unit identifies pixels whose readout noise is below a threshold as pixels to be used for photon number integration. This further reduces the influence of readout noise on each pixel. By reducing the influence of readout noise on each pixel, the accuracy of the conversion from electrical signals to photon numbers is improved, and the signal-to-noise ratio of the spectral data is further improved.

[0012] [4] The threshold for readout noise is 0.3[e - The spectrometer described in [3] is set to [rms]. This makes it possible to reduce the error rate when converting electrical signals to photon numbers to less than 10%.

[0013] [5] The identification unit identifies the pixels used for photon number integration such that the number of pixels used for photon number integration is the same in each column. The spectroscopic apparatus according to any one of [2] to [4]. In this case, it is possible to align the integrated values ​​of the readout noise of the pixels in each column used for photon number integration in the row direction. Therefore, the signal-to-noise ratio of the spectral data can be stably improved.

[0014] [6] A spectroscopic apparatus according to any one of [2] to [5], wherein the identification unit identifies a pixel to be used for integrating the number of photons and the integration ratio at the pixel based on the aberration information of light in the spectroscopic optical system, and the generation unit integrates the number of photons of multiple pixels using the integration ratio. With such a configuration, even if distortion due to aberration occurs in the wavelength-resolved image of light, the integration of the number of photons of multiple pixels can be suitably performed.

[0015] [7] A spectroscopic apparatus according to any one of [2] to [6], wherein the specific unit has in advance area information indicating areas in the pixel unit where there is no light input, and pixels corresponding to the area information are excluded from the integration of the number of photons. In this case, by excluding pixels for which the integration of the number of photons is unnecessary, the influence of readout noise of each pixel can be further reduced.

[0016] [8] The spectroscopic apparatus according to any one of [1] to [7], comprising a first conversion unit that converts an electrical signal into a digital value and a second conversion unit that converts the digital value into a number of photons based on pre-existing reference data. In this case, the number of photons of each pixel can be acquired while suppressing the effects of variations in the gain and offset of each pixel.

[0017] [9] A spectroscopic apparatus according to any one of [1] to [8], further comprising an analysis unit for analyzing the spectral data. In this case, the spectroscopic apparatus is equipped with a function for analyzing spectral data, thereby improving convenience.

[0018]

[10] A spectroscopic apparatus according to any one of [1] to [9], further comprising a spectroscopic optical system including a spectroscopic element that spectrally separates light in the wavelength-resolved direction. In this case, the spectroscopic apparatus is equipped with a wavelength-resolved function for light, improving convenience.

[0019] A Raman spectrometer comprising a spectrometer described in any of

[11] [1] to

[10] , a light source unit that generates light to be irradiated onto a sample, and a light guide optical system that guides the Raman scattered light generated by the irradiation of the sample to the spectrometer.

[0020] In this Raman spectroscopic measurement apparatus, based on the Raman scattered light received by each pixel constituting the pixel unit, an electrical signal output from each pixel is converted into the number of photons. When converting from the electrical signal to the number of photons, for example, the number of photons of a pixel that has not received Raman scattered light becomes zero. Therefore, when integrating the number of photons of a plurality of pixels belonging to the same column after conversion to the number of photons, the influence of the read noise of each pixel can be sufficiently reduced. Accordingly, with this Raman spectroscopic measurement apparatus, spectroscopic spectrum data of Raman scattered light can be acquired with an excellent signal-to-noise ratio.

[0021]

[12] A spectroscopic method for receiving light wavelength-dispersed in a predetermined direction and acquiring spectroscopic spectrum data of the light, the method comprising: a light receiving step of receiving the wavelength-dispersed light with a plurality of pixels arranged in a row direction along the wavelength dispersion direction and a column direction perpendicular to the row direction and converting the light into an electrical signal; a conversion step of converting the electrical signal from the plurality of pixels into the number of photons; and a generation step of integrating the number of photons of the plurality of pixels belonging to the same column and generating spectroscopic spectrum data based on the integration result.

[0022] In this spectroscopic method, based on the light received by each pixel, an electrical signal output from each pixel is converted into the number of photons. When converting from the electrical signal to the number of photons, for example, the number of photons of a pixel that has not received light becomes zero. Therefore, when integrating the number of photons of a plurality of pixels belonging to the same column after conversion to the number of photons, the influence of the read noise of each pixel can be sufficiently reduced. Accordingly, with this spectroscopic method, spectroscopic spectrum data can be acquired with an excellent signal-to-noise ratio.

Advantages of the Invention

[0023] According to the present disclosure, spectroscopic spectrum data can be acquired with an excellent signal-to-noise ratio.

Brief Description of the Drawings

[0024] [Figure 1] It is a block diagram showing the configuration of a Raman spectroscopic measurement apparatus according to an embodiment of the present disclosure. [Figure 2]This is a diagram showing the structure of an imaging sensor. [Figure 3] This graph shows the relationship between the number of electrons and the probability density. [Figure 4] (a) and (b) are graphs illustrating an example of the conversion from analog to digital values. [Figure 5] This is a schematic diagram illustrating the process of obtaining the offset value. [Figure 6] This is a schematic diagram illustrating the process of acquiring gain. [Figure 7] This is a schematic diagram showing the correspondence between gain and offset values ​​and threshold values. [Figure 8] This diagram schematically illustrates the process of converting the digital value of each pixel into the number of electrons. [Figure 9] This is a schematic diagram showing an example of a readout noise map in the pixel area. [Figure 10] This graph shows the relationship between readout noise and the error rate when converting electrical signals to photon counts. [Figure 11] (a) is a schematic diagram showing an example of a spectral image with aberrations, and (b) is a schematic diagram showing an example of spectral data obtained based on the spectral image shown in (a). [Figure 12] This is a schematic diagram showing an example of an integration ratio map in the pixel area. [Figure 13] This is a schematic graph showing spectral data obtained by vertical binning using an integrated ratio map. [Figure 14] This flowchart shows a spectroscopic method according to one embodiment of the present disclosure. [Modes for carrying out the invention]

[0025] Hereinafter, with reference to the drawings, preferred embodiments of a spectroscopic apparatus and a Raman spectrometer relating to one aspect of this disclosure will be described in detail.

[0026] Figure 1 is a block diagram showing the configuration of a Raman spectrometer according to one embodiment of the present disclosure. The Raman spectrometer 1 is a device for measuring the physical properties of a sample S using Raman scattered light Lr. In the Raman spectrometer 1, light L1 from the light source 2 is irradiated onto the sample S, and the Raman scattered light Lr generated by the interaction between the light L1 and the sample S is detected by the spectrometer 5 to acquire spectral data of the Raman scattered light Lr. By analyzing the spectral data acquired by the spectrometer 5 with the computer 6, various physical properties of the sample S, such as molecular structure, crystallinity, orientation, and strain, can be evaluated. Examples of samples S include semiconductor materials, polymers, cells, and pharmaceuticals.

[0027] As shown in Figure 1, the Raman spectroscopy apparatus 1 comprises a light source unit 2, a light guide optical system 3, a spectroscopic optical system 4, a spectrometer 5, a computer 6, and a display unit 7. For convenience, in the following description, the light incident on the spectrometer 5 via the spectroscopic optical system 4 may be referred to as light L1 to distinguish it from Raman scattered light Lr. In the spectrometer 5 incorporated into the Raman spectroscopy apparatus 1, light L1 refers to Raman scattered light Lr.

[0028] The light source unit 2 is the part that generates the light L0 that is irradiated onto the sample S. As the light source constituting the light source unit 2, for example, a light-emitting diode or an excitation light source for Raman spectroscopy can be used. The light guide optical system 3 is the part that guides the Raman scattered light Lr generated by the irradiation of the sample S with light L0 to the spectrometer 5. The light guide optical system 3 is configured with, for example, a collimating lens, one or more mirrors, a slit, and the like.

[0029] The spectroscopic optical system 4 is the part that wavelength-resolves the light L1 in a predetermined direction. The spectroscopic optical system 4 is composed of a spectroscopic element that spectrally separates the light L1 in a predetermined wavelength-resolving direction. As the spectroscopic element, for example, a prism, a diffraction grating such as a planar diffraction grating or a concave diffraction grating can be used. The Raman scattered light Lr is spectrally separated by the spectroscopic optical system 4 and input to the spectrometer 5.

[0030] In Figure 1, the spectroscopic optical system 4 is configured separately from the spectrometer 5, but the spectroscopic optical system 4 may be incorporated as a component of the spectrometer 5. That is, the spectrometer 5 may further include a spectroscopic optical system 4 that includes a spectroscopic element that spectrally separates light L1 in the wavelength-resolved direction. In this case, the wavelength-resolved function of light L1 in the spectrometer 5 improves convenience.

[0031] The spectrometer 5 is the part that receives wavelength-resolved light L1 in a predetermined direction and outputs spectral data of the light L1. In this embodiment, the spectrometer 5 receives Raman scattered light Lr dispersed in a predetermined wavelength-resolved direction by the spectroscopic optical system 4 and outputs spectral data of the Raman scattered light Lr to the computer 6.

[0032] Computer 6 physically includes memory devices such as RAM and ROM, a processor (arithmetic circuit) such as a CPU, and a communication interface. For example, a personal computer, a cloud server, or a smart device (smartphone, tablet terminal, etc.) can be used as Computer 6. Computer 6 is connected to the light source unit 2 and the spectrometer 5 of the Raman spectroscopy measuring apparatus 1 so as to be able to communicate with each other and comprehensively control these components. Computer 6 also functions as an analysis unit 8 that analyzes the physical properties of the sample S based on the spectral data received from the generation unit 13. Computer 6 outputs information showing the analysis results from the analysis unit 8 to the display unit 7.

[0033] As shown in Figure 1, the spectrometer 5 comprises a pixel unit 11, a conversion unit 12, a generation unit 13, and a identification unit 14. The pixel unit 11 has a plurality of pixels 21 that receive wavelength-decomposed light L1 and convert it into an electrical signal. In this embodiment, the pixel unit 11 and the first conversion unit 12A (described later) are composed of an imaging sensor 10. In this embodiment, the spectrometer 5 is configured as a camera comprising an imaging sensor 10, a second conversion unit 12B (described later), a generation unit 13, and a identification unit 14.

[0034] Here, the spectrometer 5 is separate from the computer 6, but the spectrometer 5 may be an integrated unit comprising a camera equipped with an imaging sensor 10, a second conversion unit 12B, a generation unit 13, and a specific unit 14, and a computer 6 (analysis unit 8) that is electrically or wirelessly connected to the camera for mutual information communication. In this case, the spectrometer is equipped with a function for analyzing spectral data, improving convenience. The spectrometer 5 may be an integrated unit comprising a camera equipped with an imaging sensor 10 and a second conversion unit 12B, and a computer 6 that functions as a generation unit 13, a specific unit 14, and an analysis unit 8.

[0035] Examples of the imaging sensor 10 include a qCMOS (quantitative Complementary Metal Oxide Semiconductor) image sensor (registered trademark), a SPAD (Single Photon Avalanche Diode) image sensor, and an MPPC (Multi-Pixel Photon Counter (registered trademark)) capable of identifying the number of photons or photoelectrons. In this embodiment, the imaging sensor 10 is composed of a qCMOS image sensor. In this embodiment, the number of photons refers to the number of photons incident on each pixel 21 of the imaging sensor 10, or the number of photoelectrons generated at each pixel 21 of the imaging sensor 10.

[0036] Figure 2 shows the structure of an imaging sensor. In Figure 2, the qCMOS image sensor is shown as an example among the sensors described above. As shown in Figure 2, in the pixel section 11 of the imaging sensor 10, multiple pixels 21 are arranged in the row direction and in the column direction perpendicular to the row direction. Here, the row direction is aligned with the wavelength resolution direction of the spectroscopic optical system 4, and the column direction is aligned with the vertical binning direction, which will be described later. In Figure 2, for the sake of explanation, a 3x3 arrangement of pixels 21 is shown as an example, but in the actual pixel section 11, n rows x m columns of pixels 21 are arranged (see Figure 9, etc.).

[0037] Each pixel 21 has a photodiode 22 and an amplifier 23. The photodiode 22 stores electrons (photoelectrons) generated by the input of light L1 as electric charge. The amplifier 23 converts the charge stored in the photodiode 22 into an electrical signal (for example, a signal indicating a voltage value) and amplifies it. The electrical signal amplified by the amplifier 23 is transferred to a vertical signal line 25 connecting the pixels 21 in the row direction by switching the selection switch 24 of each pixel 21. The electrical signal transferred to the vertical signal line 25 is sent to the A / D converter 27 after passing through a low-pass filter 26 for noise reduction. In addition, the image sensor 10 may be configured so that each pixel 21 has a low-pass filter 26 and an A / D converter 27.

[0038] When the electrical signal amplified by amplifier 23 is read out, random noise, or readout noise, is generated within amplifier 23. Figure 3 is a graph showing the relationship between the number of electrons and the probability density. In this figure, the horizontal axis shows the number of electrons, and the vertical axis shows the probability density. As shown in Figure 3, the number of electrons generated by the input photon follows a Poisson distribution.

[0039] Figure 3 shows the probability distribution of electrons for each readout noise level when an average of 2 photons are input to one pixel. Figure 3 shows seven examples of readout noise levels: 0.12 [e-rms], 0.15 [e-rms], 0.25 [e-rms], 0.35 [e-rms], 0.40 [e-rms], 0.45 [e-rms], and 1.0 [e-rms]. The results in Figure 3 show that the smaller the readout noise, the sharper the peak in the probability distribution waveform, and the clearer the distinction between the distributions for each electron number. Therefore, the magnitude of the readout noise required for distinguishing the electron number can be determined by whether or not the peaks in the probability distribution can be identified.

[0040] As shown in Figure 1, the conversion unit 12 is the part that converts electrical signals from multiple pixels 21 into the number of photons. The conversion unit 12 has a first conversion unit 12A that converts electrical signals into digital values ​​and a second conversion unit 12B that converts digital values ​​into the number of photons based on pre-held threshold data (reference data).

[0041] In this embodiment, the first conversion unit 12A is composed of the A / D converter 27 described above. The A / D converter 27 converts the analog values ​​indicated by the electrical signals output from each of the amplifiers 23 of the multiple pixels 21 into digital values. The converted digital values ​​are output to the second conversion unit 12B via the output unit 28. The digital values ​​output from the A / D converter 27 are shown by the following equation (1). Digital value [DN] = Gain [DN / e] × Number of electrons [e] + Offset value [DN] ... (1)

[0042] Figures 4(a) and 4(b) are graphs illustrating an example of conversion from analog to digital values. Figure 4(a) shows the probability distribution of electrons when an average of 2 photons are input to one pixel, given a readout noise of 0.15 [e-rms]. In Figure 4(a), thresholds are set to distinguish between electron counts, based on intermediate values ​​such as 0.5e, 1.5e, 2.5e, etc. (see dashed lines in Figure 4(a)). The data used to distinguish between these electron counts constitutes the threshold data mentioned above.

[0043] In Figure 4(b), the gain is 11 [DN / e] and the offset value is 100 [DN]. As shown in the figure, when the gain is 11 [DN / e], the distribution of digital values ​​can approximate the distribution of analog values. Also, because the gain is an odd number, the digital values ​​corresponding to the threshold are suppressed. With a large gain value, the output digital values ​​can more closely approximate the analog values. In this embodiment, the gain of the pixel unit 11 may be, for example, 10 [DN / e] or more.

[0044] Returning to Figure 1, the second conversion unit 12B, the generation unit 13 (described later), and the identification unit 14 are physically composed of a computer system equipped with a storage device such as RAM or ROM, a processor (arithmetic circuit) such as a CPU, a communication interface, etc. The second conversion unit 12B may be composed of a PLC (programmable logic controller) or an FPGA (Field-programmable gate array).

[0045] The second conversion unit 12B holds reference data for converting the digital value output from the first conversion unit 12A into the number of photons. For example, a lookup table is used as the reference data. The reference data is generated considering the variation in gain and offset values ​​among the pixels 21. For example, the reference data is generated based on the respective gain and offset values ​​of multiple pixels 21. The reference data is composed of, for example, threshold data for each pixel 21.

[0046] Threshold data is data used to classify the number of electrons. Figure 5 is a schematic diagram showing the process of acquiring the offset value. The digital value output from the A / D converter 27 is given by equation (1) described above. The offset value is given by the digital value output when no light L1 is input. In this embodiment, as shown in Figure 5, multiple digital values ​​are acquired from multiple dark images acquired by the pixel unit 11 when no light L1 is input. Then, the offset value is obtained by averaging the acquired digital values ​​for each pixel.

[0047] Figure 6 is a schematic diagram showing the process of acquiring gain. To acquire the gain of each pixel 21, first, multiple frame images are acquired by the pixel unit 11 with sufficient light. Then, the average optical signal value S [DN] and the standard deviation N [DN] of the digital values ​​at each pixel 21 are acquired. In this case, the gain is N 2 Since it is expressed as / S, the gain can be derived from the average optical signal value S and the standard deviation N.

[0048] For example, if the threshold value is an intermediate value for the number of electrons, the lower limit threshold for each number of electrons is given by equation (2) below. Similarly, the upper limit threshold for each number of electrons is given by equation (3) below. The range represented by the lower and upper thresholds is the range of the threshold corresponding to that number of electrons. Threshold (lower limit) = (number of electrons - 0.5) × gain + offset value ... (2) Threshold (upper limit) = (number of electrons + 0.5) × gain + offset value ... (3)

[0049] Figure 7 schematically shows the correspondence between gain, offset values, and thresholds. In this figure, the threshold value for each pixel when the number of electrons is determined to be 5 is shown. For example, when the gain is 10.9 [DN / e] and the offset value is 97.7 [DN], the lower threshold is 146.8 [DN] and the upper threshold is 157.7 [DN].

[0050] Figure 8 schematically illustrates the process of converting the digital value of each pixel into the number of electrons. As shown in the figure, the second conversion unit 12B can derive the number of electrons corresponding to the digital value by referring to threshold data. For example, the number of electrons for pixel 21 with a digital value of 162 [DN] is derived to be 5 electrons. The second conversion unit 12B can obtain the average number of photons for each pixel by dividing the average number of electrons by the quantum efficiency. If the quantum efficiency is 100%, the number of electrons and the number of photons will be the same. The second conversion unit 12B outputs the number of photons derived for each pixel 21 to the generation unit 13. In addition, when outputting the number of photons to the generation unit 13, the second conversion unit 12B outputs instruction information to the specific unit 14 to instruct it to start processing.

[0051] Returning to Figure 1, the generation unit 13 is the part that integrates the number of photons of multiple pixels 21 belonging to the same column and generates spectral data based on the integration result. The integration of the number of photons of multiple pixels 21 belonging to the same column is a process equivalent to so-called vertical binning. Here, vertical binning is performed not on the electrical signal from each pixel 21, but on the number of photons converted from the electrical signal. The spectral data may be a two-dimensional image representing the number of photons in each pixel 21, or it may be a histogram plotting the number of pixels against the number of photons. The generation unit 13 outputs the generated spectral data to the computer 6.

[0052] The identification unit 14 is the part that identifies the pixel 21 to be used for photon number integration from among multiple pixels 21 belonging to the same column. In other words, the identification unit 14 is the part that identifies the pixel 21 to be used for vertical binning in the generation unit 13. For example, the identification unit 14 identifies the pixel 21 whose readout noise is below a threshold as the pixel 21 to be used for photon number integration. When the identification unit 14 receives instruction information from the second conversion unit 12B, it generates identification information indicating the identified pixel 21 and outputs it to the generation unit 13. The generation unit 13 uses only the pixel 21 indicated by the identification information to integrate the photon numbers of multiple pixels 21 belonging to the same column and generates spectral data based on the integration result.

[0053] The specific unit 14 may have a readout noise map M1 for the pixel unit 11, for example, as shown in Figure 9. The readout noise map M1 is created, for example, by measuring the readout noise of each pixel 21 before incorporating the pixel unit 11 into the spectrometer 5. In the example in Figure 9, a readout noise map for a horizontally elongated pixel unit 11, where the number of pixels in the row direction is greater than the number of pixels in the column direction, is shown. In the readout noise map M1, the readout noise threshold is 0.3[e - It is set to rms. The specific unit 14 determines that the readout noise is 0.3[e based on the readout noise map M1. - Pixels 21 with a readout noise of 0.3[e- Pixel 21 (pixel 21Fa in Figure 9) exceeding [rms] is excluded from the pixels used for photon number integration.

[0054] The threshold in the readout noise map M11 is set based on the relationship between readout noise and the error rate when converting an electrical signal to the number of photons. Figure 10 is a graph showing the relationship between readout noise and the error rate when converting an electrical signal to the number of photons. As shown in the figure, the readout noise threshold is set to 0.3[e - When set to [rms], the error rate when converting electrical signals to photon counts can be reduced to 10% or less.

[0055] The identification unit 14 may identify the pixels 21 used for photon number integration so that the number of pixels 21 used for photon number integration is the same in each column. In this case, the identification unit 14 may identify the number of integrated pixels in the other columns to match the number of integrated pixels in the column with the most pixels excluded from the pixels used for photon number integration. For example, if each column has 1024 pixels and the column with the most pixels excluded from the pixels used for photon number integration has 1020 integrated pixels (4 pixels excluded), then any 4 pixels in the other columns may be set as dummy pixels not used for photon number integration, so that the number of integrated pixels in all columns is set to 1020.

[0056] The specific unit 14 may pre-store area information indicating areas in the pixel unit 11 where there is no input of light L1, and exclude pixels 21 corresponding to the area information from the photon count integration. The area information is generated in advance, for example, based on the specifications or arrangement of the spectroscopic elements in the spectroscopic optical system 4. The area information may be superimposed on the readout noise map M1. In the example in Figure 9, pixels 21 located at both ends of each column belong to area R where there is no input of light L1. Pixels 21 belonging to area R (pixels 21Fb in Figure 9) are excluded from the photon count integration in each column.

[0057] As described above, the spectroscopic optical system 4 is configured to include a spectroscopic element that spectrally separates light L1 in the wavelength-resolved direction. However, the spectral image actually formed on the pixel section 11 via the spectroscopic optical system 4 may not be linear due to the effects of optical system aberrations, as is typical in the case of Czernitana-type spectroscopy.

[0058] For example, in Figure 11(a), five wavelength-resolved spectral images (31A to 31E from the shortest wavelength side) are imaged with respect to the pixel 11, spaced apart from each other in the row direction (wavelength resolution direction). In the example in Figure 11(a), spectral image 31C, located in the center of the pixel 11, is linear in the column direction (vertical binning direction), but spectral images 31A, 31B and spectral images 31D, 31E all exhibit a so-called pincushion distortion, where the image curves toward the center of the pixel 11.

[0059] The amount of distortion in the spectral image increases with increasing distance from the center of the pixel 11. The amount of distortion in spectral images 31A and 31E is greater than the amount of distortion in spectral images 31B and 31D. If vertical binning of the number of photons in each row's pixels 21 is performed with such distortion, as shown in Figure 11(b), the wavelength resolution in the row direction may decrease in the spectral data 32A to 32E based on spectral images 31A to 31E, excluding spectral image 31C, in the spectral data 32A, 32B, 32D, and 32E based on spectral images 31A, 31B, 31D, and 31E, depending on the degree of distortion. In addition, a decrease in the peak value of spectral data 32A, 32B, 32D, and 32E may occur, resulting in a decrease in the signal-to-noise ratio.

[0060] To address this problem, the identification unit 14 may identify the pixels 21 to be used for photon number integration and the integration ratio at those pixels 21 based on the aberration information of the light L1 in the spectroscopic optical system 4, and the generation unit 13 may integrate the photon numbers of multiple pixels 21 using the integration ratio. Specifically, the identification unit 14 may have an integration ratio map M2 for the pixel unit 11, as shown in Figure 12. The aberration information used to generate the integration ratio map M2 can be obtained in advance from simulation data or measured data when light L1 is guided into the spectroscopic optical system 4. When using measured data, aberration information can be obtained based on the spectral data of multiple light images, assuming there is no local distortion.

[0061] The specific unit 14 may refer to the integration ratio map M2 and perform sub-pixel processing based on the integration ratio of multiple adjacent pixels 21 in the row direction during vertical binning of photons. Figure 12 shows extracted integration ratios of some pixels 21 corresponding to spectral images 31B and 31E from the overall integration ratio map M of the pixel unit 11. As described above, the distortion of spectral image 31E is greater than the distortion of spectral image 31B. Therefore, in the example in Figure 12, in the vertical binning of pixels 21 corresponding to spectral image 31B, sub-pixel processing is performed based on the integration ratio of two adjacent pixels 21 in the row direction. In the vertical binning of pixels 21 corresponding to spectral image 31E, sub-pixel processing is performed based on the integration ratio of three adjacent pixels 21 in the row direction.

[0062] In the example in Figure 12, the number of photons in pixel 21 with coordinates (x,y) is denoted as P(x,y). If the x-coordinate reference for pixel 21 corresponding to spectral image 31B is 300 and the y-coordinate is between -512 and +512, then the vertical binning of pixel 21 corresponding to spectral image 31B is given by equation (4) below. If the x-coordinate reference for pixel 21 corresponding to spectral image 31E is 700 and the y-coordinate is between -512 and +512, then the vertical binning of pixel 21 corresponding to spectral image 31E is given by equation (5) below.

number

number

[0063] Figure 12 shows four pixels, coordinates (300,-500), (301,-500), (300,-501), and (301,-501), as part of pixel 21 corresponding to the spectral image 31B. For these four pixels, the integration ratio of P(300,-500) is 80%, the integration ratio of P(301,-500) is 20%, the integration ratio of P(300,-501) is 90%, and the integration ratio of P(301,-501) is 10%. Therefore, in equation (4), α(300,-500) is obtained by equation (6) below, and α(300,-501) is obtained by equation (7) below. α(300,-500)=(80×P(300,-500)+20×P(301,-500)) / 100…(6) α(300,-501)=(90×P(300,-501)+10×P(301,-501)) / 100…(7)

[0064] Furthermore, Figure 12 shows nine pixels as part of the pixel 21 corresponding to the spectral image 31E, with coordinates (699,350), (700,350), (701,350), (699,349), (700,349), (701,349), (699,348), (700,348), and (701,348). For these nine pixels, the integration ratios are as follows: P(699,350) is 15%, P(700,350) is 70%, P(701,350) is 15%, P(699,349) is 20%, P(700,349) is 70%, P(701,349) is 10%, P(699,348) is 25%, P(700,348) is 70%, and P(701,348) is 5%.

[0065] Therefore, in equation (5), β(700,350) can be found using equation (8) below, and β(700,349) can be found using equation (9) below. Also, β(700,348) can be found using equation (10) below. β(700,350)=(15×P(699,350)+70×P(700,350)+15×P(701,350))…(8) β(700,349)=(20×P(699,349)+70×P(700,349)+10×P(701,349))…(9) β(700,348)=(25×P(699,348)+70×P(700,348)+5×P(701,348))…(10)

[0066] Figure 13 is a schematic graph showing spectral data obtained by vertical binning using an integration ratio map. As shown in the figure, by integrating the number of photons of multiple pixels 21 using an integration ratio based on the aberration information of light L1, even if distortion occurs in the spectral images 31A to 31E, the decrease in wavelength resolution in the row direction can be suppressed in each of the spectral data 32A to 32E based on the spectral images 31A to 31E. Furthermore, the decrease in peak value is also suppressed, and the signal-to-noise ratio is improved.

[0067] In the example shown in Figure 12, only the integration ratio map M2 of the pixel section 11 is shown, but the readout noise map M1 shown in Figure 9 may be superimposed on the integration ratio map M2. Alternatively, the area information shown in Figure 9 may be further superimposed on the integration ratio map M2. In this case, the generation unit 13 excludes the pixels 21 identified by the readout noise map M1 and the area information from the pixels used for photon number integration, and then performs vertical binning by subpixel processing using the integration ratio map M2.

[0068] Figure 14 is a flowchart of a spectroscopic method according to one embodiment of the present disclosure. This spectroscopic method is a method for receiving wavelength-resolved light in a predetermined direction and acquiring spectral data of said light. The spectroscopic method according to this embodiment is carried out using the spectroscopic apparatus 5 described above. As shown in Figure 14, the arc spectroscopic method comprises a light receiving step (step S01), a conversion step (step S02), a generation step (step S03), and an analysis step (step S4).

[0069] In the light receiving step S01, wavelength-decomposed light L1 or Raman scattered light Lr is received and converted into an electrical signal by a plurality of pixels 21 arranged in rows along the wavelength-decomposition direction and in columns perpendicular to the row direction. In the conversion step S02, the electrical signals from the plurality of pixels 21 are converted into the number of photons. In this embodiment, the electrical signals are converted into digital values ​​by the first conversion unit 12A, and then the digital values ​​are converted into the number of photons by threshold data held by the second conversion unit 12B.

[0070] In generation step S03, the number of photons of multiple pixels 21 belonging to the same column is integrated, and spectral data based on the integration result is generated. In this embodiment, when integrating the number of photons, pixels 21 whose readout noise is below a threshold are identified as pixels 21 to be used for photon number integration, and only pixels 21 whose readout noise is below a threshold are identified as pixels 21 to be used for photon number integration.

[0071] In analysis step S04, the sample S is analyzed based on the spectral data generated in generation step S03. For example, the waveform, peak position, peak intensity, and full width at half maximum of the spectral data are analyzed to evaluate various physical properties of the sample S, such as molecular structure, crystallinity, orientation, and strain.

[0072] As explained above, the spectrometer 5 converts the electrical signals output from each pixel 21 into photon counts based on the light received by each pixel 21 constituting the pixel section 11. During the conversion from electrical signals to photon counts, for example, the photon count of a pixel 21 that did not receive light becomes zero. Therefore, when integrating the photon counts of multiple pixels 21 belonging to the same column after conversion to photon counts, the influence of readout noise from each pixel 21 can be sufficiently reduced. Consequently, the spectrometer 5 can acquire spectral data with an excellent signal-to-noise ratio.

[0073] The spectrometer 5 is provided with a selection unit 14 that identifies the pixel 21 to be used for photon number integration from among multiple pixels 21 belonging to the same row. By identifying the pixel 21 suitable for photon number integration using the selection unit 14, the influence of readout noise from each pixel 21 can be further reduced. By reducing the influence of readout noise from each pixel 21, the accuracy of the conversion from electrical signals to photon numbers is improved, and the signal-to-noise ratio of the spectral data is further improved.

[0074] In the spectrometer 5, the identification unit 14 identifies pixels 21 whose readout noise is below a threshold as pixels 21 to be used for photon number integration. This further reduces the influence of readout noise on each pixel 21. By reducing the influence of readout noise on each pixel 21, the accuracy of the conversion from electrical signals to photon numbers is improved, and the signal-to-noise ratio of the spectral data is further improved.

[0075] In the spectrometer 5, the readout noise threshold is 0.3[e - It is set to [rms]. This allows the error rate when converting electrical signals to photon counts to be kept below 10%.

[0076] In the spectrometer 5, the identification unit 14 identifies the pixels to be used for photon number integration so that the number of pixels 21 used for photon number integration is the same in each column. This makes it possible to align the integrated value of the readout noise of the pixels 21 in each column used for photon number integration in the row direction. Therefore, the signal-to-noise ratio of the spectral data can be stably improved.

[0077] In the spectrometer 5, the identification unit 14 identifies the pixels 21 to be used for photon number integration and the integration ratio at those pixels 21 based on the aberration information of the light in the spectroscopic optical system 4, and the generation unit 13 integrates the photon numbers of multiple pixels 21 using the integration ratio. With this configuration, even if distortion due to aberration occurs in the image of the wavelength-resolved light L1, the integration of the photon numbers of multiple pixels 21 can be suitably performed.

[0078] In the spectrometer 5, the specific unit 14 pre-stores area information indicating areas in the pixel unit 11 where there is no light input, and excludes pixels 21 belonging to area R indicated by the area information from the integration of photons. This allows for the exclusion of pixels for which photon integration is unnecessary, further reducing the influence of readout noise on each pixel 21.

[0079] In the spectrometer 5, the conversion unit 12 is composed of a first conversion unit 12A that converts electrical signals into digital values ​​and a second conversion unit 12B that converts digital values ​​into photon counts based on pre-existing reference data. This makes it possible to acquire the photon count of each pixel 21 while suppressing the effects of variations in the gain and offset of each pixel 21.

[0080] In the Raman spectroscopy measurement device 1, which incorporates the spectrometer 5 described above, the electrical signals output from each pixel 21 constituting the pixel section 11 are converted into photon counts based on the Raman scattered light Lr received by each pixel 21. During the conversion from electrical signals to photon counts, for example, the photon count of a pixel 21 that did not receive Raman scattered light Lr becomes zero. Therefore, when integrating the photon counts of multiple pixels 21 belonging to the same column after conversion to photon counts, the influence of readout noise from each pixel 21 can be sufficiently reduced. Consequently, the Raman spectroscopy measurement device 1 can acquire spectral data of Raman scattered light Lr with an excellent signal-to-noise ratio.

[0081] Furthermore, the spectrometer 5 is not limited to application to the Raman spectroscopy measuring device 1, but may also be applied to other spectroscopic measuring devices such as fluorescence spectroscopy measuring devices, plasma spectroscopy measuring devices, and emission spectroscopy measuring devices. In addition, the spectrometer 5 may also be applied to other spectroscopic measuring devices such as film thickness measuring devices, optical density measuring devices, LIBS (Laser-Induced Breakdown Spectroscopy) measuring devices, and DOAS (Differential Optical Absorption Spectroscopy) measuring devices. [Explanation of Symbols]

[0082] 1...Raman spectroscopy measuring device, 2...Light source unit, 3...Light guide optical system, 4...Spectroscopic optical system, 5...Spectrometer, 8...Analysis unit, 11...Pixel unit, 12...Conversion unit, 12A...First conversion unit, 12B...Second conversion unit, 13...Generation unit, 14...Specification unit, 21...Pixel, L1...Light, Lr...Raman scattered light.

Claims

1. A spectroscopic device that receives light wavelength-resolved in a predetermined direction by a spectroscopic optical system including a spectroscopic element, and outputs spectral data of the said light, The system has multiple pixels that receive the wavelength-decomposed light and convert it into an electrical signal. A pixel section in which the plurality of pixels are arranged in a row direction along the wavelength resolution direction and in a column direction perpendicular to the row direction, A conversion unit that converts the electrical signals from the plurality of pixels into the number of photons, A spectroscopic apparatus comprising: a generation unit that integrates the number of photons of multiple pixels belonging to the same row and generates spectral data based on the integration result.

2. The spectroscopic apparatus according to claim 1, further comprising a identifying unit that identifies a pixel to be used for integrating the number of photons from among a plurality of pixels belonging to the same row.

3. The spectroscopic apparatus according to claim 2, wherein the identifying unit identifies pixels whose readout noise is below a threshold as pixels to be used for the integration of the number of photons.

4. The threshold for the readout noise is 0.3 [e － The spectroscopic apparatus according to claim 3, set to [rms].

5. The spectroscopic apparatus according to any one of claims 2 to 4, wherein the identifying unit identifies the pixels used for integrating the number of photons such that the number of pixels used for integrating the number of photons is the same in each row.

6. The specified unit identifies the pixels used for integrating the number of photons and the integration ratio at those pixels based on the aberration information of the light in the spectroscopic optical system. The spectroscopic apparatus according to any one of claims 2 to 4, wherein the generation unit integrates the number of photons of the plurality of pixels using the integration ratio.

7. The spectroscopic apparatus according to any one of claims 2 to 4, wherein the specified unit pre-stores area information indicating areas in the pixel unit where there is no light input, and excludes pixels corresponding to the area information from the integration of the number of photons.

8. The spectroscopic apparatus according to any one of claims 1 to 4, wherein the conversion unit comprises a first conversion unit that converts the electrical signal into a digital value, and a second conversion unit that converts the digital value into a number of photons based on pre-held reference data.

9. The spectroscopic apparatus according to any one of claims 1 to 4, further comprising an analysis unit for analyzing the aforementioned spectral data.

10. The spectroscopic apparatus according to any one of claims 1 to 4, further comprising a spectroscopic optical system including a spectroscopic element that spectrally separates the light in the wavelength resolution direction.

11. A spectroscopic apparatus according to any one of claims 1 to 4, A light source unit that generates light to irradiate the sample, A Raman spectrometer comprising a light guide optical system for guiding Raman scattered light generated by the irradiation of the sample with the light to the spectrometer.

12. A spectroscopic method for receiving wavelength-decomposed light in a predetermined direction and acquiring spectral data of said light, A light receiving step involves receiving the wavelength-decomposed light with a plurality of pixels arranged in a row direction along the wavelength-decomposition direction and in a column direction perpendicular to the row direction, and converting it into an electrical signal. A conversion step of converting the electrical signals from the plurality of pixels into the number of photons, A spectroscopic method comprising: a generation step of integrating the number of photons of multiple pixels belonging to the same column and generating spectral data based on the integration result.

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