Spectrometer, optical characteristics identification method, and program

Abstract

To provide a spectrometer, an optical characteristics identification method, and a program which employ a new method for determining spectrum information.SOLUTION: A spectrometer comprises: a light dispersion element for separating received light and emitting a plurality of light beams; a photoelectric conversion element for receiving light emitted from the light dispersion element and converting it into an electrical signal; a variable information conversion unit 35 for converting position variable information inputted as an electrical signal from the photoelectric conversion element into angle variable information; and a spectrum information acquisition unit 39 for Fourier converting the angle variable information obtained from the variable information conversion unit 35 and obtaining spectrum information. The optical characteristics identification method converts, into angle variable information, the position variable information outputted as an electrical signal from the photoelectric conversion element that receives light emitted from the light dispersion element and converts it into an electrical signal, and Fourier converts the angle variable information to obtain spectrum information. The program causes a computer to execute the optical characteristics identification method.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a spectrometer, a method for identifying optical characteristics, and a program. [Background technology]

[0002] Patent Document 1 discloses a spectroscope that includes a bottom wall portion on the surface of which a mirror with a concave mirror pattern and a spectroscopic portion with a grating pattern are provided, and a photodetector element that is arranged to face the surface of the bottom wall portion. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 7392090 Summary of the Invention [Problem to be solved by the invention]

[0004] In the spectrometer disclosed in Patent Document 1, a photodetector detects light split by a grating and outputs a spectrum. If the method for determining spectral information of light can be diversified, it is expected that the range of applications of spectrometers will expand.

[0005] In view of the above-mentioned problems, the present disclosure relates to providing a spectrometer, a method for identifying optical characteristics, and a program that employ a novel method for obtaining spectral information. [Means for solving the problem]

[0006] A spectrometer according to a first aspect of the present disclosure includes a light dispersion element that divides received light into multiple beams and outputs the beams; a photoelectric conversion element that receives the light emitted from the light dispersion element and converts it into an electrical signal; a variable information conversion unit that converts position variable information input as an electrical signal from the photoelectric conversion element into angle variable information; and a spectrum information acquisition unit that performs a Fourier transform on the angle variable information obtained by the variable information conversion unit to obtain spectrum information.

[0007] With this configuration, spectral information of the received light can be calculated using a relatively simple configuration.

[0008] Furthermore, a spectrometer according to a second aspect of the present disclosure is the spectrometer according to the first aspect of the present disclosure, further comprising: an AD conversion unit that converts the position variable information sent as an electrical signal from analog information to digital information before inputting the position variable information sent from the photoelectric conversion element to the variable information conversion unit; and a supplementary processing unit that performs at least one of resampling and interpolation on the digital information obtained by the AD conversion unit before inputting the digital information to the variable information conversion unit.

[0009] With this configuration, it is possible to perform calculations to obtain spectral information with high accuracy using digital information relatively easily.

[0010] Furthermore, a spectrometer according to a third aspect of the present disclosure is the spectrometer according to the first or second aspect of the present disclosure, further comprising an extraction unit that extracts a portion of information to be subjected to a Fourier transform from the angular variable information obtained by the variable information conversion unit before the angular variable information is processed by the spectrum information acquisition unit.

[0011] With this configuration, it becomes easier to grasp the desired spectrum from the spectrum information obtained by Fourier transform.

[0012] A light characteristic identification method according to a fourth aspect of the present disclosure includes a step of converting position variable information, which is output as an electrical signal from a photoelectric conversion element that receives light emitted from a light dispersion element that divides received light into multiple light beams and converts it into an electrical signal, into angle variable information, and a step of Fourier transforming the angle variable information to obtain spectral information.

[0013] With this configuration, the spectral information of the received light can be calculated relatively easily.

[0014] In addition, a light characteristics identification method according to a fifth aspect of the present disclosure is the light characteristics identification method according to the fourth aspect of the present disclosure, further comprising the steps of converting the position variable information from analog information to digital information before converting it into the angle variable information, and performing at least one of resampling and interpolation on the digital information before converting it into the angle variable information.

[0015] With this configuration, it is possible to perform calculations to obtain spectral information with high accuracy using digital information relatively easily.

[0016] Furthermore, a light characteristics identification method according to a sixth aspect of the present disclosure is the light characteristics identification method according to the fourth or fifth aspect of the present disclosure, further comprising a step of extracting a portion of information to be subjected to a Fourier transform from the angle variable information before performing a Fourier transform on the angle variable information.

[0017] With this configuration, it becomes easier to grasp the desired spectrum from the spectrum information obtained by Fourier transform.

[0018] A program according to a seventh aspect of the present disclosure causes a computer to execute the light characteristic identification method according to any one of the fourth to sixth aspects of the present disclosure.

[0019] With this configuration, it is possible to provide a program that can obtain spectral information of received light through calculation. [Effects of the Invention]

[0020] According to the present disclosure, spectral information of received light can be calculated using a relatively simple configuration. [Brief explanation of the drawings]

[0021] [Figure 1] 1 is a block diagram showing a schematic configuration of a spectroscope according to an embodiment; [Figure 2] FIG. 1 is a schematic diagram illustrating a schematic configuration of an optical unit according to an embodiment. [Figure 3] 1 is a schematic diagram illustrating a schematic configuration of a light dispersion element according to an embodiment. [Figure 4] FIG. 2 is a block diagram showing the functional configuration of a computing unit according to an embodiment. [Figure 5] 5A and 5B are conceptual diagrams illustrating an example of the operation of an optical unit according to an embodiment. [Figure 6] 10 is a flowchart showing a calculation procedure in a calculation unit according to an embodiment. [Figure 7] 10 is a graph showing an example of output from an extraction unit. [Figure 8] 10 is a graph showing an example of output from a spectrum information acquisition unit. [Figure 9] (A) to (J) are graphs showing the three graphs shown in each figure corresponding to the optical interference pattern in FIG. 5 and the graphs shown in FIGS. 7 and 8 for light of different wavelengths. [Figure 10] FIG. 10 is a schematic diagram illustrating a schematic configuration of a light dispersion element according to a modified example of the embodiment. [Figure 11] FIG. 2 is a block diagram illustrating an example of a hardware configuration of a computing unit according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0022] Hereinafter, an embodiment will be described with reference to the drawings. In the drawings, identical or similar reference numerals are used to designate identical or corresponding components, and redundant explanations will be omitted.

[0023] First, a spectrometer 1 according to one embodiment will be described with reference to FIG. 1. FIG. 1 is a block diagram showing a schematic configuration of the spectrometer 1. The spectrometer 1 receives light E to be analyzed and outputs an analysis result that allows the characteristics of the light E to be understood. Examples of the analysis result output by the spectrometer 1 include the wavenumber, frequency, and / or wavelength of the received light E. The spectrometer 1 includes an optical unit 10 and a calculation unit 30. The optical unit 10 outputs the light E received by the spectrometer 1 as an analyzable electrical signal. The calculation unit 30 receives the electrical signal output by the optical unit 10, performs calculations, and outputs a result that allows the characteristics of the light E received by the spectrometer 1 to be understood. In this embodiment, the spectrometer 1 includes the optical unit 10 and the calculation unit 30 packaged together. These elements will be described in more detail below.

[0024] As shown in FIG. 2, the optical unit 10 includes a light dispersing element 20, a photodiode array 15 (hereinafter referred to as "PD array 15"), and a housing 11 that houses these. The light dispersing element 20 separates received light E into a plurality of light beams and emits the separated light beams. In this specification, "light emitted" from the light dispersing element 20 collectively refers to light that has passed through the light dispersing element 20 and light that has been reflected by the light dispersing element 20. The PD array 15 receives the light emitted from the light dispersing element 20 and converts it into an electrical signal, and corresponds to a photoelectric conversion element.

[0025] The housing 11 is typically configured as a dark box. The housing 11 has an entrance slit 12 formed therein that receives light E. Therefore, the housing 11 corresponds to an entrance slit-forming member. The entrance slit 12 allows the housing 11 to block unnecessary light from entering the housing 11. Widening the entrance slit 12 increases the amount of light E transmitted, facilitating signal detection in the PD array 15. On the other hand, the entrance slit 12 should have a sufficiently narrow width within a range that allows light E to pass through, so that the light E entering the housing 11 functions as a point light source, thereby preventing the optical interference pattern from blurring due to a decrease in spatial coherence. In other words, the slit width of the entrance slit 12 should be set appropriately, taking into consideration both ease of signal detection in the PD array 15 and suppression of blurring of the optical interference pattern. Inside the housing 11, the light dispersing element 20 is disposed at a predetermined distance Z1 from the entrance slit 12, relatively close to the entrance slit 12, and the PD array 15 is disposed at a predetermined distance Z2 on the opposite side of the entrance slit 12 from the light dispersing element 20. The distance Z1 may be, for example, 5 μm to 500 μm (typically 10 μm), and the distance Z2 may be, for example, 4 mm to 6 mm (typically 5 mm). The housing 11 is formed to a size that allows the light dispersing element 20 and the PD array 15 to be disposed at predetermined positions. The housing 11 typically has a rectangular parallelepiped outer shape, but may have an outer shape other than a rectangular parallelepiped depending on the installation location of the optical unit 10, etc. The housing 11 is typically formed of black-painted aluminum, but is not limited to this and various materials suitable for the application may be used.

[0026] As shown in FIG. 3 , the light dispersing element 20 includes a scale body 21 and a film 23, and a slit 25 is formed on one surface of the scale body 21. In this embodiment, the scale body 21 is a plate-shaped scale made of a light-transmitting material such as quartz glass or a synthetic resin (e.g., polyethylene terephthalate). The scale body 21 may have a structure similar to that of an optical scale used in optical encoder products. In this embodiment, the scale body 21 has a flat front and back surfaces and is rectangular. The longitudinal length of the rectangle can be adjusted appropriately depending on the number of slits 25 to be formed. The light dispersing element 20 is disposed inside the housing 11 so that one of the rectangular surfaces of the scale body 21 faces the entrance slit 12 (see FIG. 2 ). In the following description of the scale body 21, the surface facing the entrance slit 12 is referred to as the “front surface,” and the surface behind the front surface is referred to as the “rear surface.” As shown in FIG. 2 , distance Z1 is the distance between the inner surface of the housing 11 and the rear surface of the scale body 21. When the thickness of the scale body 21 is equal to the distance Z1, the surface of the scale body 21 comes into close contact with the housing 11.

[0027] The film 23 is typically a thin metal layer provided on the back surface of the scale body 21. The metal constituting the film 23 can be chromium, aluminum, copper, nickel, or the like, and is configured to reflect and / or absorb light E entering through the entrance slit 12 (see FIG. 2). The film 23 serves to define a plurality of slits 25 on the back surface of the scale body 21. In this embodiment, the slits 25 are defined by forming areas on the back surface of the scale body 21 where the film 23 is not provided. Each of the plurality of slits 25 extends parallel to the short sides of the rectangle on the back surface of the scale body 21 and is arranged at appropriate intervals (equally spaced in this embodiment) in the direction of the long sides of the rectangle. For example, each slit 25 may have a width of 0.5 μm and an arrangement pitch of 10 μm (thus, the distance between adjacent slits 25 is 9.5 μm). The number of slits 25 formed on the back surface of the scale body 21 can be determined appropriately depending on the application, and may be, for example, 30 to 50, and is set to about 40 in this embodiment.

[0028] The light dispersing element 20 having the above-described configuration can be manufactured, for example, as follows. First, the scale body 21 is supplied to a location where the film 23 is to be installed. Supplying the scale body 21 is one form of providing the scale body 21. Next, a material (substance) constituting the film 23 is adhered to the entire back surface of the scale body 21. The material constituting the film 23 can be adhered to the back surface of the scale body 21 by vapor deposition, sputtering, electrolytic or electroless plating, or the like. As a result, a thin film 23 is formed over the entire back surface of the scale body 21. Next, the film 23 formed over the entire back surface of the scale body 21 is removed from the portion of the film 23 that will become the slits 25. This removal of the film 23 is typically performed by etching. However, when adhering the material constituting the film 23 to the back surface of the scale body 21, the portion that will become the slits 25 may be masked, or a pattern of the slits 25 may be formed with resist and the resist may be removed after the film 23 is formed. Typically, the light dispersing element 20 is manufactured in this manner. The light dispersing element 20 manufactured in this manner can be easily manufactured using techniques similar to the film formation, lithography, and / or etching processes used in IC chip manufacturing, and is therefore suitable for mass production. As shown in Fig. 2, the manufactured light dispersing element 20 is typically placed inside the housing 11 so that the center line (corresponding to the perpendicular line VL in Fig. 2) of the beam of light E entering through the entrance slit 12 passes through the centroid of the surface of the scale body 21 perpendicularly to the surface. Light transmitted through each slit 25 is emitted at various scattering angles θ1, θ2, ... (hereinafter, multiple scattering angles θ1, θ2, ... will be collectively referred to as "θn").

[0029] The PD array 15 will be described mainly with reference to FIG. 2 . As described above, the PD array 15 receives light emitted from the light dispersing element 20 and converts it into an electrical signal. As described above, the emitted light is a general term for light that has passed through the light dispersing element 20 and light that has been reflected by the light dispersing element 20. In this embodiment, based on the arrangement of the light dispersing element 20 and the PD array 15, the light received by the PD array 15 is light that has passed through the light dispersing element 20. The PD array 15 has a photodiode group 16 in which a plurality of photodiodes are arranged. Each photodiode constituting the photodiode group 16 is configured to receive light that has passed through the light dispersing element 20 and output it as a current. The photodiode group 16 is configured such that a plurality of photodiodes are arranged in a one-dimensional distribution. In the photodiode group 16, the photodiodes are arranged in the same direction as the slits 25 in the light dispersing element 20, typically at equal pitches. The length of the photodiode group 16 in the arrangement direction should be set to a length that allows the light that has passed through the light dispersing element 20 and been scattered to be received so that its characteristics can be analyzed, and may also be related to the distance between the light dispersing element 20 and the photodiode group 16. The length of the photodiode group 16 in the arrangement direction may be, for example, about 7 mm to 9 mm (typically 8 mm). The PD array 15 detects each of the multiple light beams emitted from the light dispersing element 20 at a specific scattering angle θn as position information x.

[0030] In addition to the photodiode group 16, the PD array 15 typically includes an IV conversion circuit (not shown), a pixel selector 18, and an output buffer 19. The IV conversion circuit is an electrical circuit that converts the current output by the photodiode into a voltage, and is implemented for each photodiode pixel. The pixel selector 18 transmits each voltage signal obtained by IV-converting the current for each pixel to the next stage in sequence according to a control signal from outside the PD array 15 or a predetermined sequence. The output buffer 19 temporarily stores the voltage signal output from the pixel selector 18 to the next stage. The PD array 15 is configured so that the photodiodes, the IV conversion circuit, the pixel selector 18, and the output buffer 19 work together to convert the interference pattern of light emitted from the light dispersing element 20 into an electrical signal having one-dimensional position information as a variable.

[0031] In the optical unit 10, which includes the above-described elements, light E to be analyzed enters the housing 11 through the entrance slit 12. The light E that entered the housing 11 is irradiated onto the light dispersing element 20. The light E that irradiates the light dispersing element 20 enters the scale body 21 from the front surface and transmits toward the rear surface. After passing through multiple slits 25 on the rear surface, the light E is emitted from the light dispersing element 20 toward the PD array 15. The light that exits the light dispersing element 20 is scattered and reaches the PD array 15, and an interference pattern of the scattered light is projected onto the PD array 15. This interference pattern of light reflects the wavelength dispersion characteristics of the light E that entered the housing 11 through the entrance slit 12. In the PD array 15, the interference pattern of the light irradiating the photodiode group 16 is converted into a current signal, and this current signal is converted into a voltage signal in an IV conversion circuit. This voltage signal is sent to the pixel selector 18 and transmitted to the output buffer 19 in an order that follows an external control signal or a predetermined sequence. The voltage signal transmitted to the output buffer 19 is output at the appropriate time and is output from the optical unit 10 as an optical-electrical conversion signal. The voltage signal output from the optical unit 10 is position variable information having one-dimensional position information as a variable. The voltage signal output from the optical unit 10 is input to the calculation unit 30.

[0032] As shown in the block diagram of FIG. 4 , the arithmetic unit 30 in this embodiment includes an AD conversion unit 31, a supplementary processing unit 33, a variable information conversion unit 35, an extraction unit 37, and a spectral information acquisition unit 39. The units 31, 33, 35, 37, and 39 shown in FIG. 4 are conceptually distinguished from the viewpoint of the functions of the arithmetic unit 30 for convenience, and are typically integrated into an actual hardware configuration. The hardware configuration of the arithmetic unit 30 typically includes a processor and memory. The processor may include a central processing unit (CPU), a graphics processing unit (GPU), or a microprocessor. The processor can execute programs and manipulate data to perform the operations of the arithmetic unit 30, including operations using any algorithms, methods, functions, processes, flows, and procedures described in this disclosure. The memory temporarily or permanently stores programs and / or data used for information processing in the arithmetic unit 30. The memory may include volatile memory such as RAM or cache, and non-volatile memory such as ROM.

[0033] The AD conversion unit 31 is a component that converts the position variable information output as a voltage signal from the PD array 15 of the optical unit 10 (see FIG. 2) from analog information to digital information. By converting the position variable information from analog information to digital information in the AD conversion unit 31, subsequent calculations become easier to process.

[0034] The supplementary processing unit 33 is a component that performs resampling and / or interpolation on the digital information obtained by the AD conversion unit. Because the analog information is converted to digital information in the AD conversion unit 31 first, resampling and interpolation can be easily performed in the supplementary processing unit 33. Resampling allows sampling to be performed using a different sampling point series from the digital information received from the AD conversion unit, and interpolation allows the number of measurement points to be artificially increased by filling in the information between adjacent sampling points. Furthermore, by performing resampling and / or interpolation in the supplementary processing unit 33, variables that were previously discrete in the digital information received from the AD conversion unit 31 can be treated as quasi-continuous variables.

[0035] The variable information conversion unit 35 is a component that converts position variable information input to the arithmetic unit 30 as a voltage signal from the PD array 15 (see FIG. 2) into digital information, which is then resampled and / or interpolated, and then converted into angular variable information in this embodiment. The angular variable (scattering angle θn) can be found, for example, by using the arctangent function (arctan(x / Z2)) of the ratio of the distance x between the target photodiode and the position where the normal VL to the back surface intersects with the photodiode group, to the distance Z2 between the back surface of the scale main body 21 and the photodiode group in the direction perpendicular to the back surface of the scale main body 21 in the optical unit 10 (see FIG. 2).

[0036] The extraction unit 37 is a component that extracts, from the angle variable information obtained by the variable information conversion unit, a portion of information to be used for calculation in the spectrum information acquisition unit 39. Typically, the extraction unit 37 extracts information to facilitate acquisition of desired components in the spectrum information acquisition unit 39. An example of information extraction by the extraction unit 37 is cutting out and / or filtering the angle variable information obtained by the variable information conversion unit.

[0037] The spectral information acquisition unit 39 is a component that performs a Fourier transform on the angle variable information to obtain spectral information. In this embodiment, the spectral information acquisition unit 39 performs a Fourier transform on the angle variable information extracted by the extraction unit 37. The spectral information acquisition unit 39 may perform a window function process (e.g., a Hanning window) before performing a Fourier transform on the angle variable information. The Fourier transform performed by the spectral information acquisition unit 39 may be a fast Fourier transform (FFT). The spectral information obtained by the spectral information acquisition unit 39 is typically transmitted to an external display device so that it can be displayed on the display device.

[0038] Next, the operation of the spectrometer 1 will be described mainly with reference to FIGS. 1 to 4. When light E to be split (light E to be analyzed) is irradiated toward the entrance slit 12 of the optical unit 10, the irradiated light E passes through the entrance slit 12 and enters the housing 11. As described above, part of the light E that enters the housing 11 passes through the slit 25 of the light dispersing element 20 and is scattered to reach the PD array 15, and an interference pattern of the scattered light is irradiated onto the PD array 15. FIG. 5 shows an image of an interference pattern P of light with a wavelength of 650 nm. In FIG. 5, an image of the light interference pattern P is shown above the PD array 15 for the convenience of visually grasping the intensity difference of the light interference pattern P, but it does not actually appear inside the housing 11. In the image of the light interference pattern P shown in FIG. 5, the vertical axis represents the light intensity, and the horizontal axis represents the position variable x. 5, the light interference pattern P on the PD array 15 has a peak intensity that is greater the closer to the intersection point of the light dispersion element 20 and the perpendicular line VL dropped from the back surface of the scale body 21, and a peak intensity that is smaller the farther from the intersection point. The light interference pattern P is also symmetrical with respect to the perpendicular line VL dropped from the back surface of the scale body 21. As described above, the light interference pattern P irradiated onto the PD array 15 is converted into a current signal by the photodiode group 16, and then converted into a voltage signal by an IV conversion circuit (not shown). The voltage signal transmitted to the output buffer 19 is output from the optical unit 10 to the calculation unit 30.

[0039] Next, the operation of the arithmetic unit 30 will be described in detail with reference to the flowchart in Figure 6. As described above, the arithmetic unit 30 determines the characteristics of light that has entered the spectrometer 1 by calculation, and the following description of the operation of the arithmetic unit 30 also illustrates one embodiment of a method for determining light characteristics. In the following description of the operation of the arithmetic unit 30, reference will be made to Figures 2, 3, and 5 as appropriate when referring to the configuration of the optical unit 10, and to Figure 4 as appropriate when referring to the configuration of the arithmetic unit 30. The light characteristics determination method according to this embodiment can be provided in the form of a program for causing a processor in the arithmetic unit 30 to execute predetermined operations, or in the form of a non-transitory computer-readable medium storing this program.

[0040] The calculation unit 30 receives the interference pattern P of light irradiated onto the PD array 15 from the optical unit 10 as a voltage signal of position variable information (S1). When the calculation unit 30 receives the voltage signal of position variable information, the AD conversion unit 31 converts the received voltage signal of position variable information from analog information to digital information (S2). Next, the supplementary processing unit 33 resamples and / or interpolates the digital position variable information converted by the AD conversion unit 31 (S3). This makes it possible to treat the discrete variables as quasi-continuous variables. Because the variables processed by the supplementary processing unit 33 are position variable information, the variable information conversion unit 35 converts this position variable information into angle variable information (S4).

[0041] Once the variable information conversion unit 35 obtains the angular variable information, the extraction unit 37 extracts a portion of the angular variable information by, in this embodiment, extracting the right half of the obtained angular variable information (S5). The right half is extracted here because, as described above, the interference pattern P of the light irradiated onto the PD array 15 is symmetrical with respect to the perpendicular line VL dropped from the rear surface of the scale body 21, and therefore, it is sufficient to analyze only one side of the symmetry axis. Extracting the right half of the angular variable information typically involves detecting the midpoint of the variable direction of the figure of the light interference pattern P (in other words, the position corresponding to the symmetry axis of the line symmetry), and then extracting the right half from there. The midpoint of the variable direction of the figure of the light interference pattern P may be obtained, for example, by pattern matching between specific left and right regions. An example of a pattern obtained by extracting the right half of the angular variable information is shown by the solid line L1 in FIG. 7. FIG. 7 illustrates the light interference pattern P image shown in FIG. 5, in which the horizontal position variable x is converted into the scattering angle θn. Instead of cutting out the right half of the angle variable information, the cut left half may be folded over and overlapped with the right half, which can improve the strength of the pattern being handled.

[0042] After the extraction unit 37 extracts the right half of the angle variable information, the spectrum information acquisition unit 39 performs window function processing on the extracted angle variable information in this embodiment (S6) and then performs a Fourier transform (S7). In this embodiment, a Hanning window is used for the window function processing (S6), but this is not limited to the Hanning window. Other appropriate window functions, such as a Hamming window, may also be used depending on the situation. An example of a pattern obtained by performing window function processing on the extracted angle variable information is shown by the dashed-dotted line L2 in Figure 7. As can be seen from the dashed-dotted line L2 in Figure 7, by performing window function processing, the magnitudes of both ends become approximately the same, thereby ensuring the periodicity of the signal.

[0043] 8 shows an example of spectral information obtained by Fourier transform (S7). In the graph shown in FIG. 8, the horizontal axis represents wavenumber k (in this embodiment, the wavenumber k multiplied by 20,000 represents the wavenumber per 1 μm), and the vertical axis represents a linear representation of light intensity. As can be seen from FIG. 8, the spectral information obtained by Fourier transform includes the desired optical spectrum G, a DC component F, and a harmonic component H. Here, the DC component F and the harmonic component H, other than the desired optical spectrum G, are unnecessary components. Therefore, in order to reduce their influence, filtering may be performed in extraction unit 37 after the step of cutting out the right half (S5) and before the step of performing window function processing (S6).

[0044] The filtering performed by the extraction unit 37 typically involves weighting the spatial frequency components of the optical interference pattern P using a digital filter with the spatial frequency as a variable. Weighting with the spatial frequency as a variable can cut DC components, cut harmonic components, and / or equalize the sensitivity characteristics of the spectrometer 1. Since the spectral sensitivity characteristics of a light dispersing element and the sensitivity characteristics of a typical photodiode differ depending on the wavelength of the received light, equalization can be achieved by adding an inverse function of the function that represents this difference as a transfer function to flatten the signal. Furthermore, filtering makes it possible to extract only the operating wavelength range. For filtering, a bandpass filter is preferably used, taking into consideration the need to cut DC components. Furthermore, using a bandpass filter can set the passband to a wavelength range less than an octave (e.g., 450 nm to 800 nm). If a wavelength range of an octave or more (for example, 400 nm to 800 nm) were used as the passband, the second harmonic of light with a wavelength of 800 nm would appear at 400 nm as the result of the FFT calculation, making it impossible to separate it from the true 400 nm component. However, by using a wavelength range of less than an octave as the passband, this inconvenience can be avoided.

[0045] In the flowchart shown in FIG. 6, if the characteristics of light can be identified even if any of the steps other than the step (S4) of converting position variable information into angle variable information and the step (S7) of performing a Fourier transform are omitted, those steps may be omitted. If omitting one or more of these steps results in unnecessary parts of the arithmetic unit 30, those parts may also be omitted. From the spectral information (see FIG. 8) obtained by the Fourier transform (S7) in the arithmetic unit 30, the wavenumber or frequency of the light entering the spectrometer 1 can be determined, and the characteristics of the light can be identified. This is because the interference pattern P (see FIG. 5) of the light irradiated on the PD array 15 and the spectral information (see FIG. 8) obtained by the Fourier transform (S7) differ depending on the wavenumber or frequency of the light entering the spectrometer 1.

[0046] For reference, Figures 9(A) to 9(J) show examples of graphs corresponding to Figures 5, 7, and 8 for light of various wavelengths. Figures 9(A) to 9(J) show the results of simulating light interference for light with a wavelength of 350 nm (Figure 9(A)) increasing in 50 nm increments up to 800 nm (Figure 9(J)). Each of Figures 9(A) to 9(J) contains three graphs, and in each figure, the graph on the left corresponds to the light interference pattern P shown in Figure 5, the graph in the center corresponds to Figure 7, and the graph on the right corresponds to Figure 8.

[0047] A cross-sectional examination of the left graphs in each of Figures 9(A) through 9(J) reveals that the overall shape of the pattern projected onto the PD array 15 varies depending on the wavelength. For example, the shape of each wave differs depending on the wavelength, and the overall pattern envelope can appear as a single peak or as two peaks. Furthermore, the right graphs in each of Figures 9(A) through 9(J) reveal that the shorter the wavelength (closer to Figure 9(A)), the higher the wavenumber k. Thus, the characteristics of the light can be determined by performing the necessary calculations and then performing a Fourier transform on the interference pattern P of the light irradiated onto the PD array 15. More specifically, the wavelength of the target light can be identified by determining the correlation between the shape, size, and other characteristics of the interference pattern P and light of such wavelengths.

[0048] As described above, the spectrometer 1 and the light characteristic identification method according to the present embodiment make it possible to obtain spectral information of received light relatively easily by calculation. Furthermore, the light dispersing element 20 according to the present embodiment, which is provided in the spectrometer 1 according to the present embodiment, has a configuration in which the film 23 is provided on the rear surface of the scale body 21 except for the slit 25, so that the configuration is simple and suitable for mass production.

[0049] In the above explanation, the light dispersing element 20 is described as a transmissive light dispersing element that irradiates the PD array 15 with light that has passed through the slit 25, but it may also be configured as a reflective light dispersing element that irradiates the PD array 15 with light that has been reflected by a film.

[0050] FIG. 10 shows a configuration example of a reflective light dispersing element 20A. The reflective light dispersing element 20A has a plurality of strip-shaped (elongated) films 23A provided on the surface of the scale body 21, and these films 23A define a strip-shaped reflective surface. The reflective light dispersing element 20A differs from the aforementioned light dispersing element 20 (see FIG. 3), which uses slits 25 (see FIG. 3) formed on the back surface of the scale body 21, in that the interference pattern of light irradiated onto the PD array 15 is created by the films 23A formed on the surface of the scale body 21 that define the strip-shaped reflective surface. To manufacture the reflective light dispersing element 20A, for example, a mask or resist coating may be applied to areas other than the areas that will become the strip-shaped reflective surface, and then the film 23A may be provided on the surface of the scale body 21 in the same manner as in the manufacture of the light dispersing element 20 (see FIG. 3), and the mask or resist may then be removed. Furthermore, a light absorbing material 27 that absorbs light may be provided on the back surface of the scale body 21. The light absorbing material 27 may be a film. In such a reflective light dispersing element, typically, light that is not desired to be irradiated onto the PD array 15, in other words, light that is not desired to be reflected by the reflective light dispersing element, is transmitted through the scale body 21 and absorbed by the light absorbing material 27 provided on the back surface of the scale body 21. Alternatively, in the reflective light dispersing element, the scale body 21 itself may be formed from a light absorbing material instead of a light-transmitting material.

[0051] In the above description, the light dispersing elements 20, 20A are formed by forming the films 23, 23A on the rear surface or front surface of the scale body 21, but they may also be gratings (diffraction gratings).

[0052] In the above description, in the light characteristic identification method in the calculation unit 30, the extraction unit 37 cuts out the right half of the converted angle variable information or folds back the cut left half and overlaps it with the right half, but instead of using the right half, the left half may be used instead. In this case, the left half of the converted angle variable information is cut out, or the cut right half is folded back and overlaps it with the left half.

[0053] In the above description, the spectrometer 1 is described as including the calculation unit 30. However, all or part of the functions of the calculation unit 30 may be provided in a device external to the spectrometer 1. The external device is typically a device remotely located from the optical unit 10. Examples of a device remotely located from the optical unit 10 include a device that is not housed in the same housing as the optical unit 10 or that is not permanently installed in the same space as the optical unit 10. An example of using an external device is inputting electrical signals output from the PD array 15 of the optical unit to an external computer (such as a personal computer, smartphone, tablet device, or server) and using the external computer as a calculation device to perform the calculations previously performed by the calculation unit 30. In this case, a spectroscopic system including the optical unit 10 and the external calculation device is constructed, and the external calculation device performs the functions of the calculation unit 30. Therefore, the functional configuration of the external calculation device can also be applied to the external calculation device as shown in the block diagram of FIG. 4. 4 can be regarded as showing not only the arithmetic unit 30 but also the functional configuration of the external arithmetic device. That is, the external arithmetic device can be regarded as including an AD conversion unit 31, a supplementary processing unit 33, a variable information conversion unit 35, an extraction unit 37, and a spectrum information acquisition unit 39.

[0054] Here, the hardware configuration of the external computing device 50 (hereinafter referred to as "external computing device 50") will be described with reference to the block diagram shown in FIG. 11. The block diagram shown in FIG. 11 shows a conceptual physical configuration of the external computing device 50. In the following description of the hardware configuration of the external computing device 50, when referring to the configuration of the spectroscopic system, reference will be made to FIGS. 1 to 4 as appropriate. The external computing device has a processor 55, a memory 56, a storage 57, and a communication interface 58. The external computing device may be a computer.

[0055] The processor 55 processes various types of information in the external computing device 50. The various types of information processed by the processor 55 include conversion from analog information to digital information in the AD conversion unit 31, resampling and / or interpolation in the supplementary processing unit 33, conversion from position variable information to angle variable information in the variable information conversion unit 35, extraction of information in the extraction unit 37, and window function processing and Fourier transform in the spectrum information acquisition unit 39. The processor 55 may be a single processor or two or more processors. The processor 55 may include a central processing unit (CPU), a graphics processing unit (GPU), a microprocessor, a circuit board, or other electrical circuitry. The processor 55 can execute programs and manipulate data to perform operations of the external computing device, including operations using any algorithms, methods, functions, processes, flows, and procedures described in this disclosure.

[0056] The memory 56 temporarily or permanently stores programs and / or data used for information processing in the external computing device 50. The memory 56 may store programs used by the external computing device 50 to make various judgments and decisions. These programs can be added or changed later (i.e., after the external computing device 50 is manufactured). The memory 56 may be a single memory or two or more memories. The memory 56 may include volatile memory such as RAM or cache, and non-volatile memory such as ROM.

[0057] The storage 57 may store data during calculations in the external computing device 50, as necessary. The storage 57 may store programs used by the external computing device 50 to make various judgments and decisions. The storage 57 may hold other programs, including an operating system, that can be executed by the external computing device 50 or other devices. The storage 57 may include a hard disk drive (HDD), a solid state drive (SSD), and / or a flash memory, etc.

[0058] The communication interface 58 communicates with the optical unit 10. The communication interface 58 can receive a voltage signal from the optical unit 10. Furthermore, the communication interface 58 communicates with an external display device, particularly when the external computing device 50 does not have a display device such as a monitor. The communication interface 58 can transmit information about the spectrum to the external display device.

[0059] The components of the external computing device 50 (including the processor 55, memory 56, storage 57, and communication interface 58) are connected to one another by a bus such as a system bus or a control bus, and can communicate with one another. The external computing device 50 may also have a power supply 59. The power supply 59 typically includes a power plug that draws in power from a commercial power source or other power source. The power supply 59 may include a replaceable or non-replaceable battery, and the battery may be capable of being charged by receiving power from the commercial power source or other power source.

[0060] The external computing device 50 described above includes a memory 56 and a processor 55 connected to the memory 56. The processor 55 is configured to convert position variable information output as an electrical signal from the photoelectric conversion element 15, which receives light emitted from the light dispersing element 20 and converts the received light into a plurality of light beams, into angular variable information, and to obtain spectral information by performing a Fourier transform on the angular variable information. The light dispersing element 20 may divide the received light into a plurality of light beams according to wavelengths. The processor 55 typically acquires spectral information by executing a program.

[0061] In the above description of the hardware configuration of the external computing device 50, the programs and / or data stored in the memory 56 and / or storage 57 may be stored on a non-transitory computer-readable medium. The non-transitory computer-readable medium stores computer-readable instructions for executing a computer-implemented method and / or data used therein. Computer-readable media may include magneto-optical disks and optical memory devices, as well as digital video disks (DVDs), CD-ROMs, DVD+ / -Rs, DVD-RAMs, DVD-ROMs, HD-DVDs, and Bluray® media. Computer-readable media may also include magnetic devices such as tapes, cartridges, cassettes, and removable disks. Each program may include one or more modules of computer program instructions encoded on a tangible, non-transitory computer-readable medium for execution by or to control the operation of an information processing device, including a computer (external computing device 50). The programs and / or data may also be downloaded from an external device via a network.

[0062] In addition, the present disclosure can be implemented with various modifications within the scope of the gist thereof, and all such modifications are included in the technical concept of the present disclosure. [Explanation of symbols]

[0063] 1 spectrometer 10 Optical unit 11 Housing (entrance slit forming member) 12 Entrance slit 15 PD array (photoelectric conversion element) 20 Light dispersing element 21 Scale body 23 membrane 23A Film (Strip-shaped Reflective Surface) 25 slit 30 computing units 31 AD conversion section 33 Supplementary Processing Section 35 Variable information conversion section 37 Extraction part 39 Spectral information acquisition unit 50 External calculation device (calculation device) E light P Light interference pattern

Claims

1. a light dispersion element that splits received light into a plurality of beams and outputs the beams; a photoelectric conversion element that receives the light emitted from the light dispersion element and converts it into an electrical signal; a variable information conversion unit that converts position variable information input as an electrical signal from the photoelectric conversion element into angle variable information; a spectrum information acquisition unit that performs a Fourier transform on the angle variable information obtained by the variable information conversion unit to obtain spectrum information, Spectrometer.

2. an AD conversion unit that converts the position variable information sent as an electrical signal from the photoelectric conversion element from analog information to digital information before inputting the position variable information to the variable information conversion unit; a supplementary processing unit that performs at least one of resampling and interpolation on the digital information obtained by the AD conversion unit before inputting the digital information to the variable information conversion unit, 10. The spectrometer of claim 1.

3. an extraction unit that extracts, from the angle variable information obtained by the variable information conversion unit, a portion of information to be subjected to a Fourier transform before the angle variable information obtained by the variable information conversion unit is processed by the spectrum information acquisition unit; 3. The spectrometer according to claim 1 or 2.

4. a step of converting position variable information output as an electrical signal from a photoelectric conversion element that receives light emitted from a light dispersion element that divides the received light into a plurality of light beams and converts the light into an electrical signal into angle variable information; and Fourier transforming the angle variable information to obtain spectral information. Optical property identification method.

5. converting said position variable information from analog to digital information before converting said position variable information to said angle variable information; and performing at least one of resampling and interpolation on the digital information before converting it into the angle variable information.

5. The method of claim 4.

6. a step of extracting, from the angle variable information, a portion of information to be subjected to the Fourier transform, before the angle variable information is Fourier transformed; 5. The method of claim 4.

7. A method for identifying light characteristics according to any one of claims 4 to 6, program.

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