Ultrasensitive spectrometer

Abstract

An ultra-sensitive spectrometer is disclosed. The disclosed ultra-sensitive spectrometer includes a scattering medium, a light receiving sensor disposed downstream of the scattering medium, a storage unit that stores wavelength-specific pre-speckle pattern information for the scattering medium, and a signal processing unit that processes the sensing signal of the light receiving sensor. The scattering medium scatters incident light to be analyzed to form a random speckle pattern, and the light receiving sensor senses the speckle pattern formed by the scattering medium. The signal processing unit recovers spectral information of the light to be analyzed from the sensing information of the speckle pattern formed by the scattering medium.

Description

Technology Field

[0001] A supersensitive light spectrometer is disclosed.

[0002] This research was conducted with support from the Samsung Future Technology Development Program (Project No.: SRFC-IT2002-03). Background Technology

[0003] A spectrometer is one of the optical instruments that measures the spectral distribution of light absorbed or emitted by a target material by decomposing it according to wavelength. To separate light by wavelength, the spectrometer uses optical elements such as diffraction gratings, prisms, interferometers, and optical filters. Such a spectrometer requires a free distance between the optical elements and the light receiving sensor (11) that senses the spectra, and the size of the spectrometer increases as the required resolution increases. The problem to be solved

[0004] We provide an ultra-sensitive spectrometer capable of realizing an ultra-small form factor. means of solving the problem

[0005] A super-sensitive spectrometer according to the type of work comprises: a scattering medium that scatters incident light to be analyzed and forms a random speckle pattern that changes sensitively according to wavelength change; a light receiving sensor disposed downstream of the scattering medium and sensing the speckle pattern formed by the scattering medium; a storage unit that stores wavelength-specific prior speckle pattern information for the scattering medium; and a signal processing unit that processes the sensing signal of the light receiving sensor to restore spectral information of the light to be analyzed from the sensing information of the speckle pattern formed by the scattering medium.

[0006] At least one of the scattering characteristics of the scattering medium and the separation distance between the scattering medium and the light receiving sensor may be determined such that at least some speckle size of the speckle pattern formed on the sensing surface of the light receiving sensor is larger than the pixel size of the light receiving sensor.

[0007] The above condition may be set so that the average speckle size of the speckle pattern exceeds the pixel size of the light receiving sensor.

[0008] The signal processing unit can restore spectrum information by applying a compression sensing algorithm to the sensing information of the speckle pattern.

[0009] The signal processing unit can restore the spectral information of the light to be analyzed through an inverse operation process in which the sensing information of the speckle pattern is represented by a compressed sensing response matrix using prior speckle pattern information stored in the storage unit and a matrix operation of the input spectrum.

[0010] In the above scattering medium, nanoparticles can be dispersed disorderly in a transparent medium.

[0011] The above nanoparticles include a plurality of nanoparticles of different sizes, and the size range of the nanoparticles can be determined to obtain spectroscopic characteristics in a set spectral range.

[0012] The above transparent medium may be transparent to visible light.

[0013] The above transparent medium includes PDMS, and the nanoparticles may include ZnO.

[0014] The scattering medium may consist of a single layer or be composed of a stack of multiple scattering medium layers.

[0015] The thickness and scattering coefficient of the scattering medium above may be limited to obtain a set wavelength resolution.

[0016] The thickness and scattering coefficient of the scattering medium may be limited to obtain a wavelength resolution of 0.1 nm or less.

[0017] The scattering medium may be composed of a stacked structure of multiple metasurfaces having an arrangement of meta atoms that are spaced apart from each other.

[0018] At least one of the above plurality of meta surfaces may be a random meta surface.

[0019] The above random metasurface allows meta atoms to be arranged in a disordered size distribution.

[0020] The meta atoms of the above random meta surface are formed at the same height, and the size of the meta atoms may be irregular.

[0021] The meta atoms of the above random meta surface can be positioned regularly.

[0022] The meta atoms of the above random meta surface are regularly positioned and may have irregular sizes.

[0023] The spacing between the plurality of metasurfaces may be limited to obtain a wavelength resolution of 0.1 nm or less.

[0024] At least one of the number of meta surfaces and the spacing distance between the meta surfaces may be determined such that at least some speckle size of the speckle pattern formed is larger than the pixel size of the light receiving sensor.

[0025] The disorder of the above metasurface may be constrained so that the average speckle size of the speckle pattern exceeds the pixel size of the light receiving sensor. Effects of the invention

[0026] According to the ultra-sensitive spectrometer of the embodiment, by applying a scattering medium, a short optical propagation distance is required, so an ultra-small form factor can be realized. Brief explanation of the drawing

[0027] FIGS. 1 and 2 schematically show an ultra-sensitive spectrometer according to an embodiment. Figure 3 is a block diagram schematically showing the configuration of the light receiving sensors of Figures 1 and 2. Figure 4 exemplarily shows the arrangement relationship between the scattering medium and the light receiving sensor of an ultra-sensitive spectrometer according to an embodiment. Figures 5 and 6 are graphs showing the wavelength response characteristics of the scattering medium according to the number of stacked thin scattering medium layers. Figures 7a and 7b show the change in speckle pattern according to wavelength in a single thin scattering medium layer when the thickness and scattering coefficient of the thin scattering medium layer are varied by controlling the concentration and amount of the mixed solution in which ZnO nanoparticles are dispersed. FIGS. 8 and 9 illustrate the arrangement relationship between the scattering medium and the light receiving sensor of an ultra-sensitive spectrometer according to an embodiment, showing an example in which the scattering medium is composed of a stacked structure of a plurality of metasurfaces having an arrangement of meta atoms. Figure 10 schematically shows a plan view of a random metasurface. FIG. 11 is a perspective view showing an example of a meta-atom applied to the meta-surface of FIG. 8 to FIG. 10. FIGS. 12a to 12h are plan views showing exemplary shapes of meta atoms that can be employed on a meta surface. Figure 13 is a graph showing the relationship between the width of the meta-atom and the phase delay of light passing through the meta-atom. Figure 14 schematically shows a method for designing a random metasurface with limited disorder for controlling speckle pattern size. Figure 15 shows the process of constructing a random metasurface from a designed random phase map. Figure 16a is a graph showing the change in spectral resolution according to the number of stacked metasurfaces. Figure 16b is a graph showing the change in spectral resolution according to the anisotropy coefficient (g) of the metasurface. Figure 17 shows the results of comparing speckle pattern measurements and simulation values ​​for a single random metasurface. Figure 18 shows the change in speckle size according to the spacing between the final metasurface and the light receiving sensor. Figure 19 is a graph showing the wavelength response characteristics of a scattering medium composed of two random metasurfaces, showing the difference in wavelength response characteristics according to the spacing between the two random metasurfaces. FIG. 20 shows the principle of spectral information recovery in an ultra-sensitive spectrometer according to an embodiment. Figure 21 shows an example in which spectral information is restored from an overlapping speckle pattern by applying a compression sensing algorithm. FIGS. 22a, FIGS. 22b, and FIGS. 22c are diagrams illustrating the performance of spectrum reconstruction based on superimposed speckle patterns. Specific details for implementing the invention

[0028] Hereinafter, exemplary embodiments will be described in detail with reference to the attached drawings. In the drawings below, the same reference numerals denote the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of explanation. Meanwhile, the embodiments described below are merely illustrative, and various modifications are possible from these embodiments.

[0029] In the following, terms designated as "upper" or "upper" may include not only those located directly above, below, to the left, or to the right in contact, but also those located above, below, to the left, or to the right without contact. Singular expressions include plural expressions unless the context clearly indicates otherwise. Furthermore, when a part is described as "comprising" a certain component, this means that, unless specifically stated otherwise, it does not exclude other components but may include additional components.

[0030] The use of the term “for the above” and similar descriptive terms may be in both singular and plural. Unless there is an explicit description of the order of the steps constituting the method, these steps may be performed in a suitable order and are not necessarily limited to the described order.

[0031] Additionally, terms such as “...part,” “module,” etc., as described in the specification refer to a unit that processes at least one function or operation, and this may be implemented in hardware or software, or as a combination of hardware and software.

[0032] The connections of lines or connecting members between the components shown in the drawings are exemplary representations of functional connections and / or physical or circuit connections, and may be replaced or additionally represented as various functional connections, physical connections, or circuit connections in the actual device.

[0033] All examples or the use of exemplary terms are merely for the purpose of describing the technical concept in detail, and unless limited by the claims, the scope is not limited by such examples or exemplary terms.

[0034] The ultra-sensitive spectrometer according to the embodiment is configured such that light to be analyzed is scattered by a scattering medium to form a speckle pattern on the sensing surface of a light receiving sensor, and the sensing signal of the light receiving sensor is processed to restore spectral information of the light to be analyzed. At this time, the scattering characteristics of the scattering medium may be constrained such that at least some speckle size of the speckle pattern formed on the sensing surface of the light receiving sensor is larger than the pixel size of the light receiving sensor. For example, the scattering characteristics of the scattering medium may be constrained such that the average speckle size of the speckle pattern exceeds the pixel size of the light receiving sensor. Here, as is well known, a speckle pattern is a distribution of bright regions (speckle grains) with random positions, brightness, and size on a dark background. Speckle size may represent the average size of the bright regions (speckle grains) of the speckle pattern. Speckle size can be calculated, for example, by taking the autocorrelation of the speckle pattern image and the full width half maximum (FWHM) of the peak. The average speckle size of the speckle pattern may be the average size of the bright area of ​​the entire speckle pattern.

[0035] FIGS. 1 and 2 schematically show an ultra-sensitive spectrometer (10) according to an embodiment. FIG. 2 further includes a first and second openings (3)(5) that limit the area where light is incident on the scattering medium (20) and the area where light passing through the scattering medium (20) is emitted, at the front and rear ends of the scattering medium (20) of FIG. 1. FIG. 3 is a block diagram schematically showing the configuration of the light receiving sensor (11) of FIGS. 1 and 2.

[0036] Referring to FIGS. 1 and 2, the ultra-sensitive spectrometer (10) includes a light receiving sensor (11), a scattering medium (20) disposed in front of the light receiving sensor (11), a storage unit (30) that stores prior speckle pattern information of the scattering medium (20), and a signal processing unit (50) that processes the sensing signal of the light receiving sensor (11) to restore spectral information of the light to be analyzed (1). The scattering medium (20) scatters the incident light to be analyzed (1) to form a random speckle pattern that changes sensitively according to changes in wavelength. The light receiving sensor (11) senses the speckle pattern formed by the scattering medium (20). As illustrated in FIG. 2, the ultra-sensitive spectrometer (10) according to the embodiment may further include a first opening (3) on the side where the light to be analyzed (1) is incident on the scattering medium (20), and a second opening (5) on the side where the light passing through the scattering medium (20) is emitted. The first opening (3) may limit the area where the light to be analyzed (1) is incident on the scattering medium (20). FIG. 2 shows the first opening (3) and the second opening (5) separated from the scattering medium (20), but this is not limited thereto. For example, at least one of the first opening (3) and the second opening (5) may be positioned without a separation distance from the scattering medium (20).

[0037] Meanwhile, the light to be analyzed (1) may have a wavelength within a predetermined range. For example, the light to be analyzed (1) may have a wavelength within the range of 400 nm to 700 nm. The light to be analyzed (1) may have a wavelength within a different range. The wavelength range of the light to be analyzed (1) may vary depending on the target of analysis. The ultra-sensitive spectrometer (10) according to the embodiment may have specifications determined according to the analysis wavelength band. The scattering medium (20) may be set according to the analysis wavelength band, and other specifications of the ultra-sensitive spectrometer (10) may be determined accordingly. The ultra-sensitive spectrometer (10) according to the embodiment may further be equipped with a filter member (not shown) that limits light outside the analysis target wavelength range upstream of the scattering medium (20) to reduce noise caused by light outside the analysis wavelength band.

[0038] Referring to FIG. 3, the light receiving sensor (11) may be pixelated and may have a pixel array (13) in which a plurality of pixels are arranged in two dimensions on a sensing surface (11a). The light receiving sensor (11) may further include a timing controller (16), a row decoder (14), and an output circuit (15).

[0039] A speckle pattern may be formed on the sensing surface (11a) of the light receiving sensor (11) by light scattered by a scattering medium (20). The pixels of the light receiving sensor (11) may have a size smaller than at least some speckle size of the speckle pattern formed on the sensing surface (11a). The pixels may be in the micro or sub-micro range. However, they are not limited thereto.

[0040] As described below, the super-sensitive spectrometer (10) according to the embodiment may be constrained such that at least some speckle size of the speckle pattern formed on the sensing surface (11a) of the light receiving sensor (11) is larger than the pixel size. Additionally, the average speckle size of the speckle pattern may be constrained such that it exceeds the pixel size of the light receiving sensor (11). Furthermore, the super-sensitive spectrometer (10) according to the embodiment may be configured to form a speckle pattern with a speckle size at least twice the pixel size on the sensing surface (11a) of the light receiving sensor (11) to satisfy, for example, Nyquist conditions. To satisfy these conditions, the scattering characteristics of the scattering medium (20) and the separation distance between the scattering medium (20) and the sensing surface (11a) of the light receiving sensor (11) may be determined.

[0041] The row decoder (14) can select one or more of the rows of the pixel array (13) of the light receiving sensor (11) in response to a row address signal output from the timing controller (16). The output circuit (15) can output a light detection signal in column units from a plurality of pixels arranged along the selected row. To this end, the output circuit (15) may include a column decoder and an analog-to-digital converter (ADC), etc. For example, the output circuit (15) may include a plurality of ADCs each placed column by column between the column decoder and the light receiving sensor (11), or a single ADC placed at the output terminal of the column decoder. The timing controller (16), the row decoder (14), and the output circuit (15) may be implemented as a single chip or as separate chips. A signal processing unit (50) for processing a sensing signal output through an output circuit (15) may be implemented as a single chip together with a timing controller (16), a row decoder (14), and an output circuit (15).

[0042] Referring again to FIGS. 1 and FIGS. 2, the scattering medium (20) may be configured to scatter incident light (1) to be analyzed, thereby forming a random speckle pattern that changes sensitively according to wavelength change. The speckle pattern formed by the scattering medium (20) may be received on the sensing surface (11a) of the light receiving sensor (11). The scattering medium (20) may be separated from the sensing surface (11a) of the light receiving sensor (11) by a distance (D1). The scattering characteristics determined by the scattering coefficient and thickness, etc., of the scattering medium (20), and / or the distance (D1) from the sensing surface (11a) may be determined such that at least some speckle size of the speckle pattern formed on the sensing surface (11a) of the light receiving sensor (11) is larger than the pixel size of the light receiving sensor (11). Additionally, scattering characteristics determined by the scattering coefficient and thickness of the scattering medium (20), and / or the separation distance (D1) from the sensing surface (11a), etc., may be determined such that the average speckle size of the speckle pattern formed on the sensing surface (11a) of the light receiving sensor (11) exceeds the pixel size of the light receiving sensor (11).

[0043] The scattering medium (20) may be formed such that, for example, nanoparticles (25) that are scattering bodies are randomly dispersed in a transparent medium (21), as exemplarily shown in FIG. 4, and the thickness of the scattering medium (20) may correspond to the thickness of the transparent medium (21). As another example, the scattering medium (20) may be formed as a stacked structure of a plurality of metasurfaces (100) having an arrangement of meta atoms (105), as exemplarily shown in FIG. 8 and FIG. 9. When the scattering medium (20) is formed as a stacked structure of a plurality of metasurfaces (100), there may be a spacing between the metasurfaces, and the thickness of the scattering medium (20) may correspond approximately to the sum of the spacing between the metasurfaces. For example, when the scattering medium (20) is formed of two metasurfaces, the thickness of the scattering medium (20) may correspond approximately to the spacing between the two metasurfaces.

[0044] The scattering medium (20) may be configured to obtain a set wavelength resolution. The wavelength resolution of the ultra-sensitive spectrometer (10) according to the embodiment may be determined by the thickness and scattering coefficient of the scattering medium (20). The scattering medium (20) may have its scattering coefficient and thickness limited, for example, to obtain a wavelength resolution of approximately 0.1 nm or less, for example, approximately 0.001 nm.

[0045] The storage unit (30) can store characteristic information of the scattering medium (20). The characteristic information of the scattering medium (20) may include prior information on speckle patterns formed by the scattering medium (20) according to wavelength. The characteristic information for each wavelength, which varies according to the scattering coefficient and thickness of the scattering medium (20), can be converted into a lookup table, and the data converted into this lookup table can be stored in the storage unit (30).

[0046] The signal processing unit (50) can process the sensing signal of the light receiving sensor (11) to restore the spectrum information of the light to be analyzed (1) from the speckle pattern formed by the scattering medium (20) and the characteristic information of the scattering medium (20) stored in the storage unit (30), such as prior speckle pattern information. The signal processing unit (50) may be configured to restore the spectrum information of the light to be analyzed (1) using a compression sensing algorithm technique. That is, since the speckle pattern formed by scattering the light to be analyzed (1) by the scattering medium (20) forms a different speckle pattern depending on the wavelength, an overlapping speckle pattern is formed on the sensing surface (11a) of the light receiving sensor (11), and the sensing information of the light receiving sensor (11) may be for the overlapping speckle pattern. Therefore, the spectral information of the light to be analyzed (1) can be restored by applying a compressed sensing algorithm using the pre-speckle pattern information stored in the storage unit (30) to the sensing information of the superimposed speckle pattern. For example, as shown in the measurement model exemplarily illustrated in FIG. 20 described later, the spectral information of the light to be analyzed (1) can be restored by performing an inverse operation process in which the sensing information of the superimposed speckle pattern is represented as a matrix operation of the input spectrum and a compressed sensing response matrix using the pre-speckle pattern information stored in the storage unit (30). To increase the accuracy of spectrum restoration, the response matrix may be pre-calibrated.

[0047] FIG. 4 illustrates an exemplary arrangement relationship between a scattering medium (20) and a light receiving sensor (11) of a supersensitive spectrometer (10) according to an embodiment, showing an example in which the scattering medium (20) includes a transparent medium (21) and nanoparticles (25) randomly dispersed in the transparent medium (21). As illustrated in FIG. 4, a first opening (3) and a second opening (5) may be provided before and after the scattering medium (20), and the light to be analyzed (1) may be focused by, for example, a focusing lens (2) and incident on the scattering medium (20) through the first opening (3), but is not limited thereto and various modifications are possible.

[0048] Referring to FIG. 4, the size (diameter), material, dispersion density, thickness of the scattering medium (20), etc. of the nanoparticles (25) dispersed in the transparent medium (21) of the scattering medium (20) can be limited so as to obtain a set wavelength resolution.

[0049] In the case of a scattering medium (20) in which nanoparticles (25) are dispersed in a disorderly manner, the wavelength sensitivity, i.e., the wavelength resolution (△λ), is approximately the average free transport distance (l) as shown in Equation 1 below. t It is proportional to ) and can be inversely proportional to the square of the thickness (L) of the scattering medium (20).

[0050]

[0051] In mathematical equation 1, λ c is the central scattering wavelength of the scattering medium (20). The average free transport distance (l) of the scattering medium (20). t ) corresponds to the scattering coefficient.

[0052] For example, the scattering medium (20) l t When formed such that = 30μm and L = 1mm, the central scattering wavelength (λ c When ) is approximately 500 nm, the wavelength resolution (△λ) becomes approximately 0.015 nm, and the central scattering wavelength (λ cWhen the wavelength is about 1 μm, the wavelength resolution (△λ) is approximately 0.06 nm. In this way, when the light to be analyzed is in the visible light region, the infrared region, or a longer wavelength band, a scattering medium (20) can be formed to obtain a wavelength resolution of approximately 0.1 nm or less.

[0053] According to the embodiment, the transparent medium (21) forming the scattering medium (20) may include various materials capable of dispersing nanoparticles (25). For example, to be transparent to visible light, the transparent medium (21) may be made of PDMS and the nanoparticles (25) may include ZnO nanoparticles, but are not limited thereto.

[0054] The scattering medium (20) can be formed, for example, by stacking two or more thin scattering medium layers to achieve a wavelength resolution, for example, of approximately 0.1 nm or less, with a set wavelength sensitivity. For example, a thin scattering medium layer in which ZnO nanoparticles are dispersed in a PDMS transparent medium can be formed with a thickness of about tens of μm to hundreds of μm, and a scattering medium (20) having a set target wavelength sensitivity can be formed by stacking several thin scattering medium layers formed in this way.

[0055] Meanwhile, the size of the nanoparticles (25) dispersed in the scattering medium (20) may be two or more. As is well known, the spectrum of scattered light varies depending on the size of the nanoparticles (25). The size range of the nanoparticles (25) can be determined to obtain spectroscopic characteristics within a set spectrum range. FIG. 4 shows an example in which the nanoparticles (25) are composed of approximately three sizes, but this is not limited thereto, and nanoparticles (25) of a wider variety of sizes may be applied.

[0056] Meanwhile, FIG. 4 illustrates that the scattering medium (20) has a single layer of a desired thickness, but this is merely for convenience and does not limit the scattering medium (20) to being composed of a single layer. For example, the scattering coefficient (ls) and thickness (L) of the scattering medium (20) can be determined so that an L / ls value satisfying a set wavelength resolution is obtained. For example, as described above, the scattering medium (20) can be prepared by stacking two or more thin scattering medium layers so that an L / ls value satisfying a set wavelength resolution is obtained. At this time, since the multiple stacked thin scattering medium layers correspond to a stack of transparent media in which nanoparticles are dispersed, the boundary between the thin scattering medium layers is also transparent, so the structure in which multiple thin scattering medium layers are stacked can be considered as a single layer scattering medium (20) in which nanoparticles (25) are dispersed in a transparent medium (21). As another example, the scattering medium (20) may be formed as a single layer having a scattering coefficient and thickness such that an L / ls value satisfying a set wavelength resolution is obtained.

[0057] To obtain a scattering medium (20) in which nanoparticles (25) are dispersed in a transparent medium (21), a thin scattering medium layer in which ZnO nanoparticles are dispersed in a PDMS medium can be formed, for example, as follows. The PDMS curable resin may consist of a main material and a curing agent, and the main material and the curing agent may be mixed in a predetermined ratio, for example, about 10:1. To produce a thin scattering medium layer, first, a small amount of ZnO nanoparticle powder may be mixed into a PDMS solution. The ZnO nanoparticles may have a size of about 100 nm or less, and the size may be two or more. For example, a mixed solution may be made by mixing about 1.5 g of ZnO nanoparticle powder into about 100 ml of PDMS solution. A thin scattering medium layer in which ZnO is dispersed in a PDMS medium may be formed by spin-coating a predetermined amount of this mixed solution onto a plate and baking. Baking can be performed at a relatively low temperature, for example, at a temperature of about 100 degrees or lower, for example, at about 80 degrees or lower, but is not limited thereto. Baking may also be performed at a temperature of 100 degrees or higher. Depending on conditions such as the concentration of the mixed solution, the amount of mixed solution used in a single spin coating, and the rotation speed for spin coating, the scattering coefficient and thickness of the thin scattering medium layer may vary. For example, about 3 ml of a mixed solution in which about 1.5 g of ZnO nanoparticle powder is mixed with about 100 ml of PDMS solution can be placed on a circular plate with a diameter of about 14 cm, spin-coated at about 100 ORPM until the mixed solution spreads over the entire circular plate, and baked at about 80 degrees for about 1 hour. Through this, a thin scattering medium layer having, for example, a thickness (L) of about 131 μm and a scattering coefficient (ls) of about 46.8 μm can be formed.

[0058] By stacking multiple thin scattering medium layers formed in this manner, a scattering medium (20) with a structure in which nanoparticles (25) are dispersed in a transparent medium (21) can be formed.

[0059] FIGS. 5 and 6 are graphs showing the wavelength response characteristics of a scattering medium (20) according to the number of stacked thin scattering medium layers. The response characteristics of FIGS. 5 and 6 show the wavelength response characteristics according to the number of stacked layers when a thin scattering medium layer is formed with a thickness (L) of 131 μm and a scattering coefficient (ls) of approximately 46.8 μm, such that L / ls = 2.8. The scattering coefficient indicates that scattering occurs once when light entering the scattering medium (20) passes through the scattering medium (20) and travels an average distance of ls, and the aforementioned average free travel distance (l t () corresponds to. In FIG. 5, the horizontal axis represents the wavelength, and the vertical axis represents the degree of correlation between the speckle pattern at each wavelength and the speckle pattern at a wavelength of 560 nm. Additionally, in FIG. 5 and FIG. 6, x1 represents an example in which the scattering medium (20) consists of a single thin scattering medium layer, and x2, x3, and x4 represent examples in which the scattering medium (20) consists of two, three, and four thin scattering medium layers stacked, respectively.

[0060] Looking at FIG. 5, it can be seen that when the scattering medium (20) consists of a single thin scattering medium layer, the change in the speckle pattern according to wavelength is not significant. On the other hand, when the scattering medium (20) consists of two or more thin scattering medium layers, it can be seen that the change in the speckle pattern according to wavelength is significant. Accordingly, as can be seen in FIG. 6, it can be seen that the wavelength resolution (△λ) improves as the thickness of the scattering medium (20) increases, and the change in wavelength resolution (△λ) occurs rapidly up to a certain thickness range, for example, approximately 200 μm to 300 μm, and the degree of change in wavelength resolution (△λ) is not significant at thicknesses greater than that. As shown in FIG. 6, the graph of the relationship between the thickness (L) of the scattering medium (20) and the wavelength resolution (△λ) is approximately 1.5 x 10 -3 / L 5.086 It can be fitted.

[0061] Figures 7a and 7b show the change in speckle pattern according to wavelength in a single thin scattering medium layer when the thickness and scattering coefficient of the thin scattering medium layer are varied by controlling the concentration and amount of the mixed solution in which ZnO nanoparticles are dispersed.

[0062] The thin scattering medium layer showing the speckle pattern change of Fig. 7a was formed using 3 ml of a mixed solution in which about 1.5 g of ZnO nanoparticle powder was mixed with about 100 ml of PDMS solution, so as to have a thickness (L) of about 131 μm and a scattering coefficient (ls) of about 46.8 μm (i.e., L / ls ~ 2.8).

[0063] The thin scattering medium layer showing the speckle pattern change of Fig. 7b was formed using 0.75 ml of a mixed solution of about 12 g of ZnO nanoparticle powder mixed with about 100 ml of PDMS solution, having a thickness (L) of about 39 μm and a scattering coefficient (ls) of about 4.9 μm (i.e., L / ls ~ 7.9).

[0064] Comparing FIG. 7a and FIG. 7b, it can be seen that even when a thin scattering medium layer is formed with reduced thickness and scattering coefficient, the speckle pattern changes at a wavelength (λ) interval of about 1 nm. From this, it can be seen that a thin scattering medium layer produced by controlling the thickness and scattering coefficient can be applied as a scattering medium (20).

[0065] FIGS. 8 and 9 illustrate an exemplary arrangement relationship between a scattering medium (20) and a light receiving sensor (11) of a supersensitive spectrometer (10) according to an embodiment, showing an example in which the scattering medium (20) is composed of a stacked structure of a plurality of metasurfaces (100) having an arrangement of meta atoms (105). When the scattering medium (20) is composed of a stacked structure of a plurality of metasurfaces (100), there may be a spacing distance between the metasurfaces. Additionally, at least one of the plurality of metasurfaces (100) forming the scattering medium (20) may have a random metasurface as exemplarily shown in FIG. 10. FIG. 10 schematically shows a plan view of one random metasurface (101).

[0066] Referring to FIGS. 8 and 9, the scattering medium (20) may include a plurality of meta surfaces (100) that form a speckle pattern on the sensing surface (11a) of the light receiving sensor (11), and at least one of the plurality of meta surfaces (100) may be a random meta surface (101) as exemplarily shown in FIG. 10.

[0067] For example, a plurality of meta surfaces (100) may include first and second meta surfaces (110) (120) spaced apart from each other in a stacking direction at the front of the light receiving sensor (11), as shown in FIG. 8. Each of the first and second meta surfaces (110) (120) may have an arrangement of meta atoms (105).

[0068] The first meta surface (110) can form a separation distance of D1 between the sensing surface (11a) of the light receiving sensor (11). The second meta surface (120) can form a separation distance of D2 between the first meta surface (110). Each of the first and second meta surfaces (110) (120) may be a random meta surface (101), for example, as exemplarily shown in FIG. 10. Either the first meta surface (110) or the second meta surface (120) may be a random meta surface (101).

[0069] As another example, the plurality of meta surfaces (100) may include three or more meta surfaces spaced apart from each other in the stacking direction. For example, the plurality of meta surfaces (100) may further include a third meta surface (130) in addition to the first and second meta surfaces (110) (120) spaced apart from each other in the stacking direction, as shown in FIG. 9, in front of the light receiving sensor (11). Each of the first to third meta surfaces (110) (120) (130) may have an arrangement of meta atoms (105). The first meta surface (110) may be spaced D1 apart from the sensing surface (11a) of the light receiving sensor (11). The second meta surface (120) may be spaced D2 apart from the first meta surface (110). The third meta surface (130) may be separated from the second meta surface (120) by a distance of D3. Each of the first to third meta surfaces (110)(120)(130) may be a random meta surface (101), for example, as exemplarily shown in FIG. 10. Any one or only two of the first to third meta surfaces (110)(120)(130) may be a random meta surface (101).

[0070] FIGS. 8 and 9 show an example in which the scattering medium (20) of the supersensitive spectrometer (10) according to the embodiment is composed of two metasurfaces and three metasurfaces, but this is exemplary and the embodiment is not limited thereto, and various modifications are possible. The number of metasurfaces constituting the scattering medium (20), the spacing between metasurfaces, the number of random metasurfaces (101) applied, the disordered size distribution of meta atoms (105), etc., may vary depending on the wavelength sensitivity to be implemented and the set spectral range.

[0071] As exemplarily shown in FIGS. 8 and 9, a plurality of metasurfaces (100) constituting the scattering medium (20) are spaced apart from each other in a stacking direction (z-axis or -z-axis direction), and each may have an arrangement of meta atoms (105). At least one of the plurality of metasurfaces (100) may be a random metasurface (101) in which meta atoms (105) are arranged in a disordered size distribution as exemplarily shown in FIG. 10, and a speckle pattern may be formed on the sensing surface (11a) of the light receiving sensor (11) by the plurality of metasurfaces (100). The random metasurface (101) may have meta atoms (105) arranged in a disordered size distribution to represent random phase map information for incident plane light, for example. For example, each of the plurality of meta surfaces (100) may be a random meta surface (101) in which meta atoms (105) may be arranged in a disordered size distribution to represent random phase map information for incident plane light. In this case, the random phase map may be defined as a phase delay value according to coordinates in a spatial domain. Additionally, each of the plurality of meta surfaces (100) may have random meta surfaces in which the disordered size distribution of meta atoms (105) is different.

[0072] In this way, when the scattering medium (20) is composed of a stacked structure of a plurality of meta surfaces (100) having an arrangement of meta atoms (105), the prior speckle pattern information of the scattering medium (20) may be phase map information for a random meta surface (101) of the plurality of meta surfaces (100), i.e., random phase map information, and the storage unit (30) may store the random phase map information. The random phase map information of the random meta surface (101) may be defined as a phase delay value according to coordinates, and such a phase delay value according to coordinates may be stored in the storage unit (30). Here, if the plurality of meta surfaces (100) include at least one regular meta surface in which meta atoms (105) are regularly distributed, the phase map information for the regular meta surface may also be stored in the storage unit (30). In this way, the storage unit (30) may store phase map information for the plurality of meta surfaces (100) constituting the scattering medium (20).

[0073] Meanwhile, on each of the plurality of meta surfaces (100), meta atoms (105) may be formed at the same height and / or regularly positioned, and the size of the meta atoms (105) may be irregular. This may form a disordered arrangement of meta atoms (105) exhibiting a disordered phase delay distribution.

[0074] For example, as exemplarily shown in FIGS. 8 and 9, meta atoms (105) may be formed at the same height and regularly positioned on each of the plurality of meta surfaces (100), and only the size distribution of the meta atoms (105) may be irregular. This may form a disordered arrangement of meta atoms (105) exhibiting a disordered phase delay distribution. The change in size of the meta atoms (105) may be obtained, for example, by a change in width and / or height. The meta atoms (105) may have a rectangular column shape, for example, and may also be columns having various cross-sectional shapes.

[0075] Meanwhile, the meta atoms (105) of the plurality of meta surfaces (100) may be positioned periodically. At this time, the period of the meta atoms (105) of the plurality of meta surfaces (100) may be the same across all meta surfaces, different across some meta surfaces, or different for each meta surface. Additionally, the meta atoms (105) of the plurality of meta surfaces (100) may be formed at the same height, the height of the meta atoms (105) of some meta surfaces may differ, or the height of the meta atoms (105) may differ for each meta surface. Furthermore, the height of the meta atoms (105) may differ even within the meta surfaces.

[0076] In this way, the meta atoms (105) of the plurality of meta surfaces (100) are positioned periodically and have irregular sizes corresponding to the random phase map to be implemented, thereby forming a disordered arrangement. For example, while arranging the meta atoms (105) periodically, the height of the meta atoms (105) is fixed, and only the width (or diameter) is changed to form a disordered arrangement of meta atoms (105) that exhibits a disordered phase delay distribution. If the width of the meta atoms (105) is different, the effective refractive index changes according to the width, so the degree of phase delay may differ. The width of the meta atoms (105) may vary in the range of, for example, about 60 nm to about 300 nm, but is not limited thereto. The phase is modulated by this disordered arrangement of meta atoms (105), and a speckle pattern may be formed by the resulting interference.

[0077] Meanwhile, multiple meta surfaces (100) can be spaced apart from each other by a spacer layer (not shown).

[0078] When a plurality of meta surfaces (100) include first and second meta surfaces (110) (120) as exemplarily shown in FIG. 8, one of the first and second meta surfaces (110) (120) is formed on a substrate (not shown), and the first and second meta surfaces (110) (120) may be spaced apart by a spacer layer. For example, the first meta surface (110) may be formed on a substrate, and a spacer layer may be formed between the first meta surface (110) and the second meta surface (120). The first meta surface (110) may have a configuration in which meta atoms (105) are formed in a disordered arrangement on the substrate. A spacer layer may be formed on the first meta surface (110), and the second meta surface (120) may be formed on the spacer layer. The second meta surface (120) may have a configuration in which meta atoms (105) are formed in a disordered arrangement on a spacer layer. When the spacer layer is formed, the spaces between the meta atoms (105) of the first meta surface (110) may be filled with a spacer layer material. In the case of the outermost meta surface, e.g., the second meta surface (120), the spaces between the meta atoms (105) may or may not be filled with a spacer layer material.

[0079] Additionally, when a plurality of meta surfaces (100) further include a third meta surface (130) as exemplarily shown in FIG. 9, a spacer layer may be further formed on the second meta surface (120), and the third meta surface (130) may be formed on the spacer layer. The third meta surface (130) may have a configuration in which meta atoms (105) are formed in a disordered arrangement on the spacer layer. In this case, when forming the spacer layer, the space between the meta atoms (105) of the first meta surface (110) and the second meta surface (120) may be filled with a spacer layer material. In the case of the outermost meta surface, such as the third meta surface (130), the space between the meta atoms (105) may or may not be filled with a spacer layer material.

[0080] As another example, the space between the meta atoms (105) may be filled with a material different from the spacer layer material or left as an empty space. Here, the spacer layer material or other material filling the space between the meta atoms (105) may be a material having a refractive index different from that of the meta atoms (105).

[0081] The substrate and the spacer layer may be formed from a transparent material. At least one of the substrate and the spacer layer may be made of, for example, amorphous silicon oxide, i.e., fused silica, but is not limited thereto and may be made of various transparent materials. Here, meta surfaces may each be formed on the substrate and the meta surfaces may be joined so as to be spaced apart from each other. The spatial arrangement structure and material of the meta surfaces may also be applied even when the plurality of meta surfaces (100) include a different number of meta surfaces.

[0082] In this way, when the scattering medium (20) is composed of a stacked structure of a plurality of meta surfaces (100) having an arrangement of meta atoms (105), the prior speckle pattern information of the scattering medium (20) may be phase map information for the plurality of meta surfaces (100), i.e., random phase map information, and the storage unit (30) may store the random phase map information.

[0083] In this way, a plurality of meta surfaces (100) are provided that are spaced apart from each other by a scattering medium (20), and at least one of the plurality of meta surfaces (100) may be a random meta surface. The number of meta surfaces, the spacing between meta surfaces, and the spacing distance (D1) between the final meta surface, e.g., the first meta surface (110), and the sensing surface (11a) of the light receiving sensor (11) may be determined to form a random speckle pattern capable of achieving a set wavelength resolution. For example, the number of meta surfaces, the spacing between meta surfaces, the spacing between the final meta surface and the sensing surface (11a) of the light receiving sensor (11), and the disorder of the meta surfaces may be determined to form a random speckle pattern that is distinguished by wavelength in nm units or sub-nm units, e.g., about 0.1 nm units, within a wavelength range of interest, e.g., about 400 nm to about 700 nm.

[0084] To this end, a plurality of meta surfaces (100) may be arranged to form a speckle pattern on the sensing surface (11a) of the light receiving sensor (11), and at least one of the number of meta surfaces, the spacing distance between meta surfaces, and the spacing distance (D1) between the final meta surface, e.g., the first meta surface (110) and the sensing surface (11a) of the light receiving sensor (11), may be determined such that at least some speckle size of the speckle pattern formed on the sensing surface (11a) of the light receiving sensor (11) is larger than the pixel size of the light receiving sensor (11). Additionally, the disorder of the plurality of meta surfaces (100) may be constrained so that the average speckle size of the speckle pattern exceeds the pixel size of the light receiving sensor (11). For example, the disorder of the plurality of meta surfaces (100) may be constrained so that the average speckle size of the speckle pattern exceeds twice the pixel size of the light receiving sensor (11).

[0085] For example, a plurality of meta surfaces (100) may include at least 2 and no more than 10 meta surfaces spaced apart from each other. Additionally, the meta surfaces may be spaced apart at intervals ranging from μm to mm. Furthermore, among the plurality of meta surfaces (100), the first meta surface (110) adjacent to the light receiving sensor (11) and the sensing surface (11a) of the light receiving sensor (11) may be spaced apart at a distance greater than the spacing between the meta surfaces. The spacing between the adjacent first meta surface (110) and the sensing surface (11a) of the light receiving sensor (11) among the plurality of meta surfaces (100) may be, for example, about 1 μm or more and about 10 cm or less, such as 100 μm.

[0086] FIG. 11 is a perspective view showing an example of a meta-atom (105) applied to the meta-surfaces (101)(110)(120)(130) of FIG. 8 to 10.

[0087] Referring to FIG. 11, meta-atoms (105) can be formed in a square column shape on a base layer (105a). The base layer (105a) may correspond to either the substrate and spacer layer described above. The base layer (105a) may be, for example, made of amorphous silicon oxide, i.e., fused silica. In addition, the material of the base layer (105a) may be made of various transparent materials.

[0088] At least one of the width (W) and height (H) of the meta-atom (105) may be a sub-wavelength. Additionally, the arrangement period (P1, P2) of the meta-atom (105) may be a sub-wavelength or not a sub-wavelength. In FIG. 11, P1 represents the arrangement period of the meta-atom (105) in the horizontal direction (x-axis direction), and P2 represents the arrangement period of the meta-atom (105) in the vertical direction (y-axis direction). The arrangement period of the meta-atom (105) may be constant in both the horizontal and vertical directions. That is, P1 may equal P2. As another example, the arrangement period of the meta-atom (105) may differ from each other in the horizontal and vertical directions.

[0089] The width (W) of the meta-atom (105) may vary depending on the position in which it is placed. The meta-atom (105) may be made of a material in which the effective refractive index changes according to the width (W). The meta-atom (105) may be formed of silicon nitride, for example, such as Si3N4. In addition, the material of the meta-atom (105) may be formed of various materials in which the effective refractive index changes according to the width (W).

[0090] Meta atoms (105) of a plurality of meta surfaces (100) forming a scattering medium (20) may be formed, for example, of silicon nitride material, on a base layer (105a) comprising amorphous silicon oxide, with a period (P1=P2) of about 350 nm in the horizontal and vertical directions, a height (H) of about 900 nm, and a width (W) that varies to form a disordered size arrangement. Here, the period (P1, P2), height (H), and material of the meta atoms (105) are exemplary and the embodiments are not limited thereto, and may vary depending on design conditions.

[0091] The meta-atom (105) applied to the plurality of meta-surfaces (100) forming the scattering medium (20) can be formed as a column having various cross-sectional shapes in addition to a square column shape, for example, a circular, elliptical, rectangular shape, a square ring, a circular ring, or a cross shape.

[0092] FIGS. 12a to 12h are plan views showing exemplary shapes of meta atoms (105) that can be employed on a meta surface (100).

[0093] As shown in FIG. 12a, the cross-sectional shape of the meta-atom (105) may be circular with a diameter D. The diameter D of the cylinder may be a sub-wavelength. As shown in FIG. 12b and FIG. 12c, the cross-sectional shape of the meta-atom (105) may be a circular ring or a square ring shape with an outer diameter D and an inner diameter Di. The width (W1) of the ring may be a sub-wavelength. As shown in FIG. 12d, the cross-sectional shape of the meta-atom (105) may be an elliptical shape in which the major and minor axis lengths in the first direction (e.g., X-axis direction) and the second direction (e.g., Y-axis direction) are different, Dx and Dy. As shown in FIG. 12e, the cross-sectional shape of the meta-atom (105) may be a cross shape. As illustrated in FIG. 12f and FIG. 12g, the cross-sectional shape of the meta-atom (105) may be a rectangular shape or a cross shape in which the lengths of the first direction (e.g., X-axis direction) and the second direction (e.g., Y-axis direction) are different as Dx and Dy. Additionally, as illustrated in FIG. 12h, the cross-sectional shape of the meta-atom (105) may be a shape having a plurality of concave arcs.

[0094] In this way, the meta-atoms (105) applied to the plurality of meta-surfaces (100) forming the scattering medium (20) may be columns having various cross-sectional shapes in addition to square column shapes.

[0095] FIG. 13 is a graph showing the relationship between the width of a meta-atom (105) and the phase delay of light passing through the meta-atom (105). FIG. 13 shows the relationship between the width of the meta-atom (105) and the phase delay when the meta-atom (105) is designed as a rectangular column of Si3N4 material with a height of approximately 900 nm and a period of approximately 350 nm.

[0096] As can be seen in FIG. 13, since the degree of phase delay varies depending on the width of the meta-atom (105) and the wavelength of light, the relationship between the width of the meta-atom (105) and the phase delay can be made into a lookup table, and the data made into a lookup table can be stored in the storage unit (30). In addition, based on this relationship, a two-dimensional random phase map can be replaced with a two-dimensional meta-atom (105) width map (process design diagram) to produce a meta-surface (101, 110, 120, 130).

[0097] Figure 14 schematically shows a method for designing a random metasurface with limited disorder for controlling speckle pattern size.

[0098] Referring to Fig. 14, the phase change experienced by incident plane light by a random metasurface can be defined by a random phase map of the random metasurface, which is a function defined by a phase delay value according to coordinates in a spatial domain.

[0099] For an initial random phase (φ0) map, an optimization algorithm can be performed by alternately applying strength constraints to the spatial domain and the Fourier domain. The optimization algorithm, alternating between the spatial and Fourier domains, can be repeated N times. For example, the Gerchberg-Saxton algorithm can be used as an algorithm for this iterative optimization method.

[0100] The Fourier Transform (FT) is performed from the spatial domain to the Fourier domain, and the Inverse Fourier Transform (FT) is performed from the Fourier domain to the spatial domain. -1...can be performed. Additionally, for example, the spatial domain amplitude (u0) is not restricted, while the frequency domain amplitude (U0) can be restricted, thereby restricting the Fourier domain components of the random phase map. The restricted Fourier domain components can be expressed as numerical aperture (NA). By restricting these Fourier domain components (NA) of the random phase map, the speckle size can be controlled. That is, a tailored phase (φ) with numerical aperture (NA) is used to implement a metasurface having the desired restricted disorder. n A random phase map having ) can be obtained.

[0101] By performing an iterative optimization algorithm that imposes intensity constraints as described above, a two-dimensional random phase map corresponding to a meta-surface with limited disorder can be obtained, and each meta-surface can be fabricated by replacing this two-dimensional random phase map with a two-dimensional meta-atom width map (process design). By the stacked structure of a plurality of meta-surfaces (100) fabricated in this manner, a random speckle pattern is formed that can achieve a wavelength resolution set in the wavelength range to be analyzed, and an optimization algorithm for designing each meta-surface can be performed so that the average speckle size of the speckle pattern has a limited disorder such that it exceeds the pixel size of the light receiving sensor (11), for example, exceeds twice the pixel size.

[0102] Figure 15 shows the process of constructing a random metasurface from a designed random phase map.

[0103] As shown in FIG. 15, the designed random phase map can be converted into a width map of meta atoms (105) based on a lookup table representing the width and phase delay relationship of meta atoms (105), and using this width map, a metasurface pattern having an array of meta atoms (105) with limited disorder can be produced.

[0104] Meanwhile, according to the coherence relation theory, the wavelength resolution (△λ) of the scattering medium is proportional to the free scattering distance within the scattering medium and inversely proportional to the square of the thickness of the scattering medium.

[0105] When the scattering medium (20) is formed by a stacked structure of a plurality of metasurfaces (100), the free scattering distance within the scattering medium (20) corresponds to the spacing between metasurfaces (△L), and since the thickness of the scattering medium (20) corresponds approximately to the product of the spacing between metasurfaces (△L) and (number of metasurfaces - 1), the wavelength resolution (△λ) may be approximately inversely proportional to the spacing between metasurfaces and approximately inversely proportional to the square of the number of metasurfaces. Here, △L may correspond, for example, to D2, D3, etc. in FIG. 8 and FIG. 9.

[0106] For example, when the scattering medium (20) is formed by a stacked structure of a plurality of spaced-apart metasurfaces (100), △λ = △f × λ c 2 / c and, △f 2c / (N 2 XL t It can be. Here, λ c is the center wavelength, and N is the number of metasurfaces. l tε is the transport mean free path, which corresponds to the spacing between metasurfaces. That is, as the spacing between metasurfaces increases and the number of metasurfaces increases, the wavelength resolution can be improved, and there may be a threshold for the spacing between metasurfaces and / or the number of metasurfaces to achieve a specific wavelength resolution. Ideally, a wavelength resolution of ~0.1 nm can be achieved by placing two metasurfaces at a spacing of approximately 200 μm.

[0107] Accordingly, the wavelength resolution of the stacked structure of multiple metasurfaces (100) can be controlled using the number of stacked metasurfaces and the stacking interval. Accordingly, the number of metasurfaces and the stacking interval can be determined according to the wavelength resolution to be implemented.

[0108] FIG. 16a is a graph showing the change in spectral resolution according to the number of stacked metasurfaces when the spacing between metasurfaces (△L) is approximately 200 μm and the anisotropy coefficient (g) of the metasurface is approximately zero (△L = 200 μm, g~0). FIG. 16b is a graph showing the change in wavelength resolution (spectral resolution) according to the number of stacked metasurfaces when five metasurfaces are stacked at a spacing (△L) of approximately 200 μm (N meta = 5, △L~200μm), and this is a graph showing the change in wavelength resolution (spectral resolution) according to the anisotropy coefficient (g) of the metasurface.

[0109] As can be seen from FIGS. 16a and 16b, the number of stacked metasurfaces (N meta Spectral resolution can be improved as ) increases and the anisotropy coefficient (g) of the metasurface decreases. Additionally, spectral resolution can be improved as the spacing (△L) between stacked metasurfaces increases. However, the number of stacked metasurfaces (N metaAs the speckle size can be reduced as the anisotropy coefficient (g) of the metasurface increases and decreases, the number of stacked metasurfaces and the anisotropy coefficient (g) of the metasurface can be selected in consideration of the speckle size. That is, the number of stacked metasurfaces, the spacing between metasurfaces (△L), and the anisotropy coefficient (g) of the metasurface can be selected to form a speckle pattern in which the average speckle size is larger than the pixel size of the light receiving sensor (11) while having a desired wavelength resolution (spectral resolution), for example, a speckle pattern in which the average speckle size exceeds twice the pixel size of the light receiving sensor (11).

[0110] Meanwhile, speckle patterns can be predicted through the design of random metasurfaces and subsequent simulations, and speckle patterns can be measured through nanoprocessing and optical holography techniques. Therefore, the reliability of the design and fabrication of random metasurfaces can be evaluated by comparing the measured speckle patterns with the simulated speckle patterns.

[0111] FIG. 17 shows the results of comparing the measured and simulated speckle pattern values ​​for a single random metasurface. As can be seen in FIG. 17, the measured intensity distribution and the simulated intensity distribution of the speckle pattern show a high correlation of at least 0.5 and at most 0.8, although there are differences depending on the wavelength. From this, it can be seen that the speckle pattern generated by the stacked structure of multiple metasurfaces (100) can be predicted without a calibration process.

[0112] FIG. 18 shows the change in speckle size according to the distance between the final metasurface and the light receiving sensor (11). FIG. 18 shows the speckle size simulation results according to the conditions of the tailored NA of the metasurface, the number of metasurfaces (N), the distance between metasurfaces (D), and the distance (D1) between the final metasurface and the light receiving sensor (11) in a system including a metasurface of approximately 200 μm in size and a light receiving sensor (11) having a pixel size of approximately 1.67 μm.

[0113] As can be seen in FIG. 18, the speckle size of the speckle pattern formed on the sensing surface (11a) of the light receiving sensor (11) may vary depending on the distance (D1) between the final meta surface, i.e., the first meta surface (110) and the sensing surface (11a) of the light receiving sensor (11), and is approximately proportional to that distance.

[0114] The supersensitive spectrometer (10) according to the embodiment may be configured to form a speckle pattern with a speckle size greater than twice the pixel size of the light receiving sensor (11) to satisfy the Nyquist condition, for example. For example, when the supersensitive spectrometer (10) according to the embodiment is equipped with a light receiving sensor (11) having a pixel size of about 1.67 μm, considering the simulation results shown in FIG. 18, the distance (D1) between the final metasurface and the sensing surface (11a) of the light receiving sensor (11) may be set to about 1 μm or more and about 10 cm or less, for example, 100 μm, to satisfy the Nyquist condition, i.e., speckle size = 2 × 1.67 μm.

[0115] FIG. 19 is a graph showing the wavelength response characteristics of a scattering medium (20) composed of two random metasurfaces, showing the difference in wavelength response characteristics when the spacing between the two random metasurfaces is 100 μm and 250 μm. In FIG. 19, the horizontal axis represents wavelength, and the vertical axis represents the degree of correlation between the speckle pattern at each wavelength and the speckle pattern at a wavelength of 560 nm.

[0116] Looking at FIG. 19, it can be seen that when the distance between random metasurfaces changes from 100 μm to 250 μm, a greater change in the speckle pattern occurs. From this, it can be seen that as the spacing between random metasurfaces increases, the wavelength resolution (△λ) improves. For example, when the distance between random metasurfaces changes from 100 μm to 250 μm, the wavelength resolution can be improved by more than four times. As can be seen in FIG. 19, a scattering medium (20) capable of achieving a specific wavelength resolution and an ultra-sensitive spectrometer (10) applying the same can be implemented by utilizing the distance between random metasurfaces.

[0117] FIG. 20 illustrates the principle of spectrum information restoration in an ultra-sensitive spectrometer (10) according to an embodiment. According to the ultra-sensitive spectrometer (10) according to an embodiment, a signal processing unit (50) restores spectrum information of the light to be analyzed (1) by applying a compression sensing algorithm to the sensing information of the superimposed speckle pattern obtained from the light receiving sensor (11). In FIG. 20, I represents the sensing information obtained from the light receiving sensor (11), T is the compression sensing response matrix, and x is the spectrum information restored by the signal processing unit (50), corresponding to the spectrum of the light to be analyzed (1) input to the ultra-sensitive spectrometer (10). As shown in the measurement model exemplarily illustrated in FIG. 20, the spectrum information of the light to be analyzed (1) can be restored by performing an inverse operation process in which the sensing information of the superimposed speckle pattern is represented as a matrix operation between the compression sensing response matrix and the input spectrum using the prior speckle pattern information stored in the storage unit (30). To increase the accuracy of spectrum reconstruction, the response matrix T may be pre-calibrated. FIG. 20 illustrates only one example of a measurement model, and the embodiments are not limited thereto. Spectral analysis of an analysis target light (1) having various spectral information can be performed in the same manner as in FIG. 20.

[0118] FIG. 21 shows an example in which spectral information is recovered from an overlapping speckle pattern by applying a compression sensing algorithm. FIG. 21 is an example in which the ultra-sensitive spectrometer (10) according to the example is configured to form 25 independent color channels in the wavelength range of 551 nm to 651 nm, with approximately 50 speckles (N speckle This shows an example of recovering spectral information mixed with 2 to 25 wavelengths under sensing conditions of 50). The wavelength range and number of recovered color channels (N) shown in Fig. 21. λ ), number of sensed speckles (N speckle ), compression ratio (Compression ratio, R c The above examples are shown as examples to explain the process of recovering spectral information from superimposed speckle patterns by applying the supersensitive spectrometer (10) according to the embodiment, but the embodiment is not limited thereto and various examples are possible.

[0119] Referring to FIG. 21, the compression ratio of the overlapping speckle pattern is the number of speckles being sensed (N speckle Number of restored color channels (N) for ) λ The ratio of ) that is, N λ / N speckle It may correspond to. The compressed speckle pattern may correspond to the superposition (∑) of speckle pattern images (W1,…) corresponding to the color channel to be restored.

[0120] For example, as exemplarily shown in FIG. 21, N speckle It is 50, and the number of restored color channels is N. λ If α is 25, the compression ratio is 0.5, i.e., N λ / N speckle = It could be 0.5.

[0121] Here, N speckle N is determined by the ratio of the pixel area of ​​the light receiving sensor (11) sensing the speckle pattern to the average speckle size. For example, if the light receiving sensor (11) senses the speckle pattern in a 25 x 25 pixel area and the sensed average speckle size is approximately 3 to 4 x 3 to 4 pixels, then N speckle is approximately 50. As another example, if the light receiving sensor (11) senses a speckle pattern in, for example, a 100 x 100 pixel area, and the average speckle size sensed is approximately 5 x 5 pixels, then N speckle It becomes approximately 20 x 20 = 400.

[0122] N λ When = 25, it can be considered that 25 spectrally specific speckle pattern images are superimposed. The number of reconstructed color channels can be determined by △λ for the spectral target wavelength range. For example, when the spectral target wavelength range is 500 nm to 600 nm, the spectral width is 100 nm, and △λ = 10 nm, the wavelengths of each color channel for which spectral information is reconstructed can be, for example, 500 nm, 510 nm, ..., 590 nm. Therefore, the number of channels can be 10, i.e., (spectral width / △λ = 100 nm / 10 nm = 10).

[0123] The speckle pattern received by the light receiving sensor (11) is, for example, N λ It can be considered as superimposed speckle pattern images of several spectra. Figure 21 (a) is N λ = 25 spectrally specific speckle pattern images (W1,…, W 25 It shows the superposition of ). Fig. 21 (b) shows a wavelength-mixed speckle pattern. Nnz represents the number of wavelengths, and Fig. 21 (c) is a graph showing the reconstructed spectrum and ground truth values ​​matched.

[0124] Referring to FIGS. 21 (a) and (c), the number of reconstructed color channels in the spectral target wavelength range of 551 nm to 651 nm is N λ When = 25, spectral information can be restored at intervals of △λ=4nm.

[0125] In Fig. 21 (b), the speckle pattern of Nnz=2 represents a superposition of speckle patterns of two wavelengths, the speckle pattern of Nnz=5 represents a superposition of speckle patterns of five wavelengths, the speckle pattern of Nnz=12 represents a superposition of speckle patterns of twelve wavelengths, and the speckle pattern of Nnz=25 represents a superposition of speckle patterns of 25 wavelengths.

[0126] In Fig. 21 (c), when examining the measured values ​​and reconstructed spectrum graphs for the speckle pattern of two wavelengths (Nnz=2), it can be confirmed that values ​​(expressed as Weights) exist at the two wavelength positions. When examining the measured values ​​and reconstructed spectrum graphs for the speckle pattern of Nnz=5, it can be confirmed that values ​​exist at five or fewer wavelength positions, including the two wavelength positions for the speckle pattern of Nnz=2. When examining the measured values ​​and reconstructed spectrum graphs for the speckle pattern of Nnz=12, it can be confirmed that values ​​exist at 12 or fewer wavelength positions, including the wavelength positions where values ​​exist for the speckle pattern of Nnz=5. When examining the measured values ​​and reconstructed spectrum graphs for the speckle pattern of Nnz=25, it can be confirmed that values ​​exist at 25 or fewer wavelength positions, including the wavelength positions where values ​​exist for the speckle pattern of Nnz=12.

[0127] FIG. 21 exemplarily shows that a supersensitive spectrometer (10) having 2, 5, 12, or 25 independent color channels can be implemented, but the embodiment is not limited thereto. A supersensitive spectrometer (10) having various desired number of independent color channels can be implemented. Meanwhile, FIG. 21 shows approximately 50 speckles (N speckle An example is shown of recovering spectral information mixed with 2 to 25 wavelengths under the condition of sensing 50), and from this, it can be confirmed that more color information can be recovered even in situations where the number of speckles being sensed is small, that is, when the number of pixels of the light receiving sensor (11) is small. That is, according to the ultra-sensitive spectrometer (10) according to the embodiment, since spectral information is recovered from an overlapping speckle pattern by applying a compression sensing algorithm, the number of recovered colors can be greater than the number of measured pixels (number of sensed speckles).

[0128] FIGS. 22a, 22b, and 22c are figures illustrating the spectrum reconstruction performance based on superimposed speckle patterns. FIG. 22a shows a compression ratio of R c = 1, R c = 1.3, R c Figure 22b shows the change in the measured speckle pattern as it increases to 2.6. Figure 22b shows the change in the speckle pattern as SNR decreases to 28.22, 5.68, and 2.95 as the shot noise increases. As the signal becomes smaller, the shot noise ratio increases, so the SNR (Signal-to-Noise Ratio) decreases. Figure 22c is a table showing the relationship between shot noise, compression ratio, and reconstruction accuracy. In Figure 22c, inf, 54.03, 27.00, 5.44, and 2.83 at the top of the table represent the SNR (Signal-to-Noise Ratio), where 'inf' signifies infinity, and 0.1, 0.5, 1, 1.3, and 2.6 at the left of the table represent the compression ratio (R cIt represents ). As can be seen in Fig. 22c, the restoration accuracy can be maintained even when the SNR is low (less than 3) and compressed by more than 2 times.

[0129] The ultra-sensitive spectrometer (10) according to the embodiment described above can be used in various optical devices, sensors, electronic devices equipped with such sensors, etc. For example, it can be applied to gas sensors, chemical sensors, skin sensors, food sensors, etc. Such sensors can identify the types of various molecules present in the air and detect their concentrations using the ultra-sensitive spectrometer (10), and at this time, the fact that transmittance varies by wavelength depending on the type and concentration of the components can be utilized. In addition, the ultra-sensitive spectrometer (10) can be used as an inspection device for an object. For example, it can be used as a device to analyze the location and shape of an object, or to analyze the components, physical properties, and freshness of food of an object according to Raman spectroscopy.

[0130] The electronic device in which the ultra-sensitive spectrometer (10) according to the embodiment is applied as a sensor may be, for example, a smartphone, a mobile phone, a mobile phone, a PDA (personal digital assistant), a laptop, a PC, various portable devices, home appliances, security cameras, medical cameras, automobiles, Internet of Things (IoT) devices, other mobile or non-mobile computing devices, but is not limited thereto.

[0131] In addition to the ultra-sensitive spectrometer (10), the electronic device may further include a processor that controls it, for example, an application processor (AP), and can control multiple hardware or software components and perform various data processing and calculations by running an operating system or application through the processor.

[0132] According to the ultra-sensitive spectrometer (10) according to the embodiment described above, spectral information of the light to be analyzed can be restored from the sensing information of the superimposed speckle pattern.

[0133] For the above, an example of designing a scattering medium for restoring spectral information of an optical object to a set wavelength resolution has been described with reference to the embodiments illustrated in the drawings; however, this is merely illustrative, and those skilled in the art will understand that various modifications and equivalent alternative embodiments are possible therefrom. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of rights is defined in the claims, not in the foregoing description, and all variations within the scope of equivalence should be interpreted as being included within the scope of rights. Explanation of the symbols

[0134] 1: Light to be analyzed 10: Ultra-sensitive spectrometer 11: Light receiving sensor 11a: Sensing surface 13: Pixel array 20: Scattering medium 21: Transparent medium 25: Nanoparticle 30: Storage unit 50: Signal processing unit 100, 110, 120, 130: Meta surface 101: Random meta surface 105: Meta atom

Claims

Claim 1 A supersensitive spectrometer comprising: a scattering medium that scatters incident light to be analyzed to form a random speckle pattern that changes sensitively according to wavelength changes; a light receiving sensor disposed downstream of the scattering medium and sensing the speckle pattern formed by the scattering medium; a storage unit that stores wavelength-specific prior speckle pattern information for the scattering medium; and a signal processing unit that processes the sensing signal of the light receiving sensor to restore spectral information of the light to be analyzed from the sensing information of the speckle pattern formed by the scattering medium; wherein the scattering medium comprises nanoparticles randomly dispersed in a transparent medium, and the signal processing unit restores spectral information by applying a compression sensing algorithm to the sensing information of the speckle pattern, and restores spectral information of the light to be analyzed through an inverse operation process in which the sensing information of the speckle pattern is represented by a compression sensing response matrix using prior speckle pattern information stored in the storage unit and an input spectrum. Claim 2 A scattering medium that scatters incident light to be analyzed and forms a random speckle pattern that changes sensitively according to wavelength changes; a light receiving sensor disposed downstream of the scattering medium and sensing the speckle pattern formed by the scattering medium; and a storage unit that stores wavelength-specific pre-speckle pattern information for the scattering medium; A supersensitive spectrometer comprising: a signal processing unit that processes the sensing signal of the light receiving sensor and restores the spectral information of the light to be analyzed from the sensing information of a speckle pattern formed by the scattering medium; wherein the scattering medium is composed of a stacked structure of a plurality of metasurfaces having an arrangement of meta-atoms that are spaced apart from each other, and at least one of the plurality of metasurfaces is a random metasurface; and wherein the signal processing unit restores the spectral information by applying a compression sensing algorithm to the sensing information of the speckle pattern, and restores the spectral information of the light to be analyzed through an inverse operation process in which the sensing information of the speckle pattern is represented by a compression sensing response matrix using prior speckle pattern information stored in the storage unit and an input spectrum. Claim 3 A supersensitive spectrometer according to claim 1 or 2, wherein at least one of the scattering characteristics of the scattering medium and the separation distance between the scattering medium and the light receiving sensor is determined such that at least some speckle size of the speckle pattern formed on the sensing surface of the light receiving sensor is larger than the pixel size of the light receiving sensor. Claim 4 In paragraph 3, the above condition is a supersensitive spectrometer in which the average speckle size of the speckle pattern is set to exceed the pixel size of the light receiving sensor. Claim 5 delete Claim 6 delete Claim 7 In claim 1, the nanoparticle comprises a plurality of nanoparticles of different sizes, and the size range of the nanoparticles is determined to obtain spectroscopic characteristics in a set spectral range, in a supersensitive spectrometer. Claim 8 In claim 1, the transparent medium is a supersensitive spectrometer having transmittance to visible light. Claim 9 In claim 1, the transparent medium comprises PDMS, and the nanoparticles comprise ZnO, forming a supersensitive spectrometer. Claim 10 In claim 1, the scattering medium is composed of a single layer or a supersensitive spectrometer composed of a stack of multiple scattering medium layers. Claim 11 In claim 1, the thickness and scattering coefficient of the scattering medium are limited to obtain a set wavelength resolution in a super-sensitive spectrometer. Claim 12 In claim 11, the thickness and scattering coefficient of the scattering medium are limited to obtain a wavelength resolution of 0.1 nm or less for a supersensitive spectrometer. Claim 13 delete Claim 14 In paragraph 2, the random metasurface is a supersensitive spectrometer in which meta atoms are arranged in a disordered size distribution. Claim 15 In claim 14, the meta atoms of the random meta surface are formed at the same height, and the size of the meta atoms is irregular in the supersensitive spectrometer. Claim 16 In paragraph 15, the meta atoms of the random meta surface are regularly positioned in a supersensitive spectrometer. Claim 17 In paragraph 14, the meta atoms of the random meta surface are regularly positioned and are irregular in size in a supersensitive spectrometer. Claim 18 In paragraph 2, the spacing between the plurality of metasurfaces is limited to obtain a wavelength resolution of 0.1 nm or less in a supersensitive spectrometer. Claim 19 A supersensitive spectrometer according to any one of claims 2, 14 to 18, wherein at least one of the number of meta surfaces and the spacing distance between the meta surfaces is determined such that at least some speckle size of the speckle pattern formed is larger than the pixel size of the light receiving sensor. Claim 20 In claim 19, the degree of disorder of the metasurface is constrained such that the average speckle size of the speckle pattern exceeds the pixel size of the light receiving sensor in a supersensitive spectrometer.

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