Optical filtering micro-nano structure and filter array

Abstract

An optical filtering micro-nano structure (20) and a filter array. The optical filtering micro-nano structure (20) comprises: a first micro-nano modulation layer (21) arranged on a transparent substrate (10) of a filter, wherein the material of the first micro-nano modulation layer (21) is one of a transparent material and an optical loss material; a second micro-nano modulation layer (22) arranged on the side of the first micro-nano modulation layer (21) facing away from the transparent substrate (10), wherein the material of the second micro-nano modulation layer (22) is the other of the transparent material and the optical loss material; and a transparent protective layer (23) covering the first micro-nano modulation layer (21) and the second micro-nano modulation layer (22) and connected to the transparent substrate (10), wherein the refractive index of the transparent material is higher than the refractive index of the material of the transparent substrate (10) and the transparent protective layer (23). A filter array having the present optical filtering micro-nano structure (20) can be used for broadband filtering of color imaging with small-size pixels, and increases the transmittance of incident light, thereby realizing a color imaging function in low illumination.

Description

Light filtering micro-nanostructures and filter arrays Technical Field

[0001] The present application relates to the field of imaging technology, and in particular to a light filtering micro-nano structure and a filter array. Background Art

[0002] In the related art, a color image sensor forms a Bayer color filter array by adding dye-type three-primary color filters before the photosensitive unit array, and is implemented based on the mixing principle of the three primary colors.

[0003] Summary of the Invention

[0004] The main purpose of this application is to provide a light filtering micro-nano structure and a filter array, aiming to solve the technical problem of low imaging quality of the filter when facing low-light scenes at night.

[0005] To achieve the above-mentioned objectives, the present application proposes a light filtering micro-nano structure, comprising: a first micro-nano modulation layer, the first micro-nano modulation layer being used to be arranged on a transparent substrate of the filter, and the material of the first micro-nano modulation layer is one of a transparent material and a light loss material; the refractive index of the light loss material is higher than the refractive index of the transparent material; a second micro-nano modulation layer, the second micro-nano modulation layer being arranged on a side of the first micro-nano modulation layer away from the transparent substrate, and the material of the second micro-nano modulation layer is the other of a transparent material and a light loss material; and a transparent protective layer, the transparent protective layer covering the first micro-nano modulation layer and the second micro-nano modulation layer and being connected to the transparent substrate; wherein the refractive index of the transparent material is higher than the refractive index of the material of the transparent substrate and the transparent protective layer.

[0006] In an embodiment of the present application, the transparent material includes silicon nitride Si3N4 or titanium dioxide TiO2; and / or the light loss material includes polycrystalline silicon P-Si, amorphous silicon α-Si or germanium Ge.

[0007] In the embodiment of the present application, the first micro-nano modulation layer and the second micro-nano modulation layer are both constructed as columnar structures, and the cross-sectional shapes of the first micro-nano modulation layer and the second micro-nano modulation layer are both rotationally symmetrical figures with a rotation angle of 90°.

[0008] In the embodiment of the present application, the thickness of the transparent substrate is greater than 3.5 μm.

[0009] In the embodiment of the present application, the overall duty cycle of the first micro-nano modulation layer and the second micro-nano modulation layer is η, 0.2≤η≤0.8.

[0010] In the embodiment of the present application, in the first micro-nano modulation layer and the second micro-nano modulation layer, the thickness of the modulation layer made of the optical loss material is H2, and 10 nm ≤ H2 ≤ 100 nm.

[0011] In the second aspect, the present application also provides a filter array, comprising: an area array arranged in a position corresponding to the photosensitive unit array, and the area array includes multiple macro-pixel areas, each of the macro-pixel areas includes at least one first filter, at least one second filter and at least one third filter, the first filter allows light of a first color to pass through, the second filter allows light of a second color to pass through, and the third filter allows light of a third color to pass through; wherein, at least one of the first filter, the second filter and the third filter includes a first transparent substrate and a filtering micro-nano structure array arranged on one side of the first transparent substrate, the filtering micro-nano structure array includes multiple filtering micro-nano structures arranged in a rectangular array, and the filtering micro-nano structure is constructed as the filtering micro-nano structure provided in the first aspect.

[0012] In the embodiment of the present application, in the light filtering micro-nano structure, the thickness of the modulation layer made of transparent material is greater than 300 nm; and in the light filtering micro-nano structure array, the spacing between the central axes of adjacent light filtering micro-nano structures is P, 100 nm ≤ P ≤ 600 nm.

[0013] In an embodiment of the present application, the third filter is constructed as a visible light all-pass filter so that the light allowed to pass through is white light; the visible light all-pass filter includes a second transparent substrate and a second transparent protective layer, and the second transparent protective layer is arranged on the side of the second transparent substrate away from the photosensitive unit array.

[0014] In an embodiment of the present application, the filter array includes 1 first filter, 1 second filter and 2 third filters, and 1 first filter, 1 second filter and 2 third filters are arranged in a 2×2 array; wherein the first filter and the second filter have the filtering micro-nano structure provided by the first aspect.

[0015] In an embodiment of the present application, the side length of the first transparent substrate is less than or equal to 3 μm; wherein, the cross-sectional width of the first micro-nano modulation layer and the second micro-nano modulation layer in the first filter is D1, D1 satisfies: 100<D1<140nm, and the spacing between the central axes of adjacent filtering micro-nano structures is P1, P1 satisfies 200<P1<300nm; the cross-sectional width of the first micro-nano modulation layer and the second micro-nano modulation layer in the second filter is D2, 160<D2<200nm, and the spacing between the central axes of adjacent filtering micro-nano structures is P2, 350nm<P2<450nm.

[0016] In an embodiment of the present application, in the first diagonal direction of the macropixel area, at least one first filter and at least one second filter are arranged alternately in sequence; in the second diagonal direction of the macropixel area, at least two third filters are arranged in sequence; wherein, the first diagonal direction and the second diagonal direction are parallel to or perpendicular to each other.

[0017] The filtering micro-nanostructure provided by the technical solution of the present application constructs a double-layer modulation structure in the protective layer and the transparent substrate. The single-layer modulation layer in the double-layer modulation structure is made of light-loss material and transparent material, respectively, so that the final filtering micro-nanostructure has the advantages of high transmittance and high color modulation of the above two materials. It not only improves the transmittance of the incident light, but also ensures that the filtering micro-nanostructure still has a strong broadband spectral modulation capability for reconstructing colors under the small-size pixel arrangement of several wavelengths, thereby realizing color imaging function under low illumination. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without any creative work.

[0019] FIG1 is a schematic structural diagram of an embodiment of a light filtering micro-nanostructure of the present application;

[0020] FIG2 is a schematic cross-sectional view of a second micro-nano modulation layer of an embodiment of the light filtering micro-nano structure of the present application;

[0021] FIG3 is a schematic cross-sectional view of a second micro-nano modulation layer of another embodiment of the light filtering micro-nano structure of the present application;

[0022] FIG4 is a schematic structural diagram of another embodiment of the light filtering micro-nano structure of the present application;

[0023] FIG5 is a schematic diagram of filter arrangement according to an embodiment of a filter array of the present application;

[0024] FIG6 is a schematic diagram of a light filtering micro-nanostructure array of a filter in the filter array of the present application;

[0025] FIG7 is a schematic diagram of high transmittance broadband modulation curves of Examples 1 and 2;

[0026] FIG8 is a schematic diagram of a color image reconstructed using two high-transmittance broadband modulation curves of Example 1 and Example 2;

[0027] FIG9 is a schematic diagram of high transmittance broadband modulation curves of Examples 3 and 4;

[0028] FIG10 is a schematic diagram of high-transmittance broadband modulation curves of Examples 5 and 6.

[0029] The realization of the objectives, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0030] The following will be combined with the drawings in the embodiments of this application to clearly and completely describe the technical solutions in the embodiments of this application. Obviously, the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of this application.

[0031] It should be noted that all directional indications in the embodiments of the present application (such as up, down, left, right, front, back, etc.) are only used to explain the relative position relationship, movement status, etc. between the various components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication will also change accordingly.

[0032] In this application, unless otherwise specified or limited, the terms "connection" and "fixation" should be understood in a broad sense. For example, "fixation" can mean fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two elements or interaction between two elements, unless otherwise specified. For those skilled in the art, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0033] In addition, if there are descriptions involving "first", "second", etc. in the embodiments of the present application, the descriptions of "first", "second", etc. are only for descriptive purposes and cannot be understood as indicating or suggesting their relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of such features. In addition, the meaning of "and / or" appearing throughout the text includes three parallel schemes. Taking "A and / or B" as an example, it includes scheme A, or scheme B, or a scheme in which A and B are satisfied at the same time. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the ability of ordinary technicians in this field to implement it. When the combination of technical solutions is mutually contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0034] In the related art, a color image sensor forms a Bayer color filter array by adding dye-type three-primary color filters before the photosensitive unit array, and is implemented based on the mixing principle of the three primary colors.

[0035] However, in low-light conditions at night, the luminous flux of a Bayer color filter array is only one-third of that in normal-light conditions. Most of the light energy is absorbed by the filter dye, resulting in low energy utilization. This significantly degrades image quality, especially when used in small-pixel imaging devices, with severe color distortion.

[0036] To this end, the present application provides a solution, by designing the filtering micro-nano structure into a double-layer modulation structure composed of modulation layers made of light-loss material and transparent material respectively, so that the double-layer modulation structure combines the high color modulation properties of the light-loss material, that is, the large difference in the transmittance spectrum peak and valley of the spectral modulation curve and the large modulation peak width, with the high transmittance characteristics of the transparent material. It not only improves the transmittance of the incident light, but also ensures that the filtering micro-nano structure still has strong broadband spectral modulation capabilities under the small-size pixel arrangement of several wavelengths, thereby realizing color imaging functions under low illumination, and still has strong color reconstruction capabilities under small-size pixels.

[0037] The inventive concept of the present application is further illustrated below with reference to some specific embodiments.

[0038] This embodiment provides a light filtering micro-nano structure 20. The light filtering micro-nano structure 20 is formed on a surface of the filter that is away from the photosensitive unit array, and is used to filter and modulate incident light.

[0039] In this embodiment, the light filtering micro-nano structure 20 includes a first micro-nano modulation layer 21 , a second micro-nano modulation layer 22 and a transparent protective layer 23 .

[0040] The first micro-nano modulation layer 21 is disposed on the transparent substrate 10 of the filter, and the material of the first micro-nano modulation layer 21 is one of a transparent material and an optical loss material; wherein the refractive index of the optical loss material is higher than the refractive index of the transparent material; the second micro-nano modulation layer 22 is disposed on the side of the first micro-nano modulation layer 21 away from the transparent substrate 10, and the material of the second micro-nano modulation layer 22 is the other of the transparent material and the optical loss material; the transparent protective layer 23 covers the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 and is connected to the transparent substrate 10. The refractive index of the transparent material in the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is higher than the refractive index of the material of the transparent substrate 10 and the transparent protective layer 23.

[0041] Specifically, referring to Figure 1, the transparent substrate 10 is the main body of the filter, which is made of a transparent material corresponding to the optical band, wherein the refractive index of the material of the transparent substrate 10 is c, c satisfies: 1.4<c<2, such as various glass materials used for filters or silicon dioxide SiO2, etc. It can be understood that the transparent substrate 10 allows all light in the visible light band to pass through. The transparent substrate 10 and the photosensitive unit array are arranged relative to each other so that the light signal filtered and modulated by the filter is received by the corresponding photosensitive unit array to output a detection signal. A first micro-nano modulation layer 21 is provided on the surface of the transparent substrate 10 on the side facing away from the photosensitive unit array, and a second micro-nano modulation layer 22 is provided on the surface of the first micro-nano modulation layer 21 on the side facing away from the transparent substrate 10.

[0042] Among them, the first micro-nano modulation layer 21 has a first orthographic projection on the transparent substrate 10, and the second micro-nano modulation layer 22 has a second orthographic projection on the transparent substrate 10. The first orthographic projection and the second orthographic projection coincide with each other, that is, in this embodiment, the outer peripheral surfaces of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 are coplanar and both perpendicular to the transparent substrate 10, so as to facilitate the incident light to pass through the double-layer modulation structure and enter the transparent substrate 10.

[0043] It is worth mentioning that the material of the first micro-nano modulation layer 21 is one of a transparent material and an optical loss material, and the material of the second micro-nano modulation layer 22 is the other of a transparent material and an optical loss material. That is, when the material of the first micro-nano modulation layer 21 is a transparent material, the material of the second micro-nano modulation layer 22 is an optical loss material. Alternatively, when the material of the second micro-nano modulation layer 22 is a transparent material, the material of the first micro-nano modulation layer 21 is an optical loss material. It can be understood that in this embodiment, the high refractive index and low refractive index of the material are for the visible light band. Specifically, the refractive index of the transparent material is a, and a satisfies: 2<a<3. At this time, the transparent material is a low refractive index transparent material in the visible light band. The refractive index of the optical loss material is b, and b satisfies: 3<b<5. At this time, the optical loss material is a high refractive index optical loss material in the visible light band.

[0044] The transparent protective layer 23 is arranged on the side of the transparent substrate 10 away from the photosensitive unit array, and covers the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22. Optionally, the transparent protective layer 23 is formed by filling the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 with a photoresist, and is used to protect the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22, and is used to flatten the filter surface, facilitating the preparation of other structural devices such as microlenses thereon. The refractive index of the material of the transparent protective layer 23 is d, and d satisfies: 1.4<d<2. In this way, the refractive index of the transparent material used in the modulation layer (the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22) is higher than the refractive index of the material of the transparent substrate 10 and the transparent protective layer 23.

[0045] In this embodiment, the modulation layer, made of a light-loss material with a relatively high refractive index, is used to increase the refractive index contrast between the micro-nanostructure as a whole and the surrounding medium, such as the photoresist (transparent protective layer 23) and the filter substrate (transparent substrate 10). This improves the coupling strength between the incident light field of the micro-nanostructure and the waveguide light field within the micro-nanostructure, enhancing the filtering and modulation capabilities of a small number of micro-nanostructures. Furthermore, the optical loss of the light-loss material reduces the quality factor (Q) of the resonance within the transparent substrate 10, thereby facilitating accurate color reconstruction after broadband modulation.

[0046] It is understandable that when light passes from one medium to another, if the difference in refractive index between the two media decreases, the energy of the reflected light decreases, while the energy of the transmitted light increases. In this embodiment, because the refractive index of the transparent material used in the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is higher than that of the transparent substrate 10 and the transparent protective layer 23, the refractive index difference between adjacent media from the incident end to the transmission end of the light filtering micro-nano structure is relatively small. This improves the transmittance of the incident light compared to a micro-nano spectral modulation structure with a high refractive index contrast created solely by using high-refractive-index materials.

[0047] In this embodiment, the light filtering micro-nano structure 20 is designed to be a double-layer modulation layer structure composed of modulation layers made of a light loss material with a higher refractive index and a transparent material with a lower refractive index. The double-layer modulation layer structure combines the high color modulation properties of the light loss material with a higher refractive index and the high transmittance characteristics of the transparent material with a lower refractive index. It not only improves the transmittance of the incident light, but also ensures that the light filtering micro-nano structure still has a strong broadband spectral modulation capability under a small-size pixel arrangement of several wavelengths, thereby realizing color imaging function under low illumination, and can improve the overall broadband spectral modulation capability of the filter when the spectral modulation capability is reduced due to the reduction in refractive index contrast after the small-size pixel and the transparent protective layer 23, thereby ensuring that the filter still has a strong broadband spectral modulation capability for color reconstruction.

[0048] In addition, compared to the complementary color filter array, the filter micro-nano structure 20 provided in this embodiment does not require the additional preparation of a multi-layer coating filter, thereby reducing the manufacturing cost.

[0049] In the embodiment of the present application, the transparent material used in the modulation layer includes silicon nitride Si3N4 or titanium dioxide TiO2. It can be understood that the refractive index of Si3N4 or TiO2 is higher than the refractive index of various glass materials or silicon dioxide SiO2 used in filters.

[0050] In the embodiment of the present application, the optical loss material used in the modulation layer includes polycrystalline silicon (P-Si), amorphous silicon (α-Si), or germanium (Ge). In this case, the thickness of the modulation layer made of the optical loss material in the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is H2, where 10nm≤H2≤100nm. This ensures that the micro-nano structure has a high light flux, such as greater than 60%, and enhances the filter's broadband modulation capability when a small number of micro-nano structures are arranged, thereby preventing a decrease in broadband modulation capability.

[0051] In the embodiment of the present application, the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 are both constructed as columnar structures, and the cross-sectional shapes of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 are both rotationally symmetrical figures with a rotation angle of 90°.

[0052] Specifically, the double-layer modulation structure composed of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is constructed as a columnar structure protruding from the transparent substrate 10. The central axis of the columnar structure is perpendicular to the surface of the transparent substrate 10. The cross-section of any modulation layer in the double-layer modulation structure is the intersection area of ​​the plane parallel to the plane where the transparent substrate 10 is located and the modulation layer. In this embodiment, the cross-sectional shape of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 are both rotationally symmetric figures with a rotation angle of 90° to ensure the polarization-independent characteristics of the spectral modulation, thereby maintaining the high transmittance of the micro-nano structure. For example, referring to Figures 2 and 3, the rotationally symmetric image with a rotation angle of 90° can be a circle, a square, an annular ring, etc.

[0053] In the embodiment of the present application, referring to FIG1 , the thickness of the transparent substrate 10 is H1, where H1>5λ. λ is the average wavelength of visible light. In this case, the broadband modulation interference caused by the Fabry-Peror resonance in the transparent substrate 10 can be reduced.

[0054] In the embodiment of the present application, the overall duty cycle of the double-layer modulation structure composed of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is η, 0.2≤η≤0.8, to ensure that the double-layer modulation structure is easy to etch using ICP (inductively coupled plasma) etching technology. The overall duty cycle is the ratio of the cross-sectional width of the columnar structure to the total layer height of the double-layer modulation structure.

[0055] Specifically, if the cross-sectional width of the columnar structure is D, then η = D / (H2 + H3). H3 is the thickness of the modulation layer made of a transparent material. When the cross-sectional shape of the first and second micro-nano modulation layers is circular, the cross-sectional width D is the cross-sectional diameter of the columnar structure, as shown in Figure 2. When the cross-sectional shape of the first and second micro-nano modulation layers is square, the cross-sectional width D is the cross-sectional side length of the columnar structure, as shown in Figure 3.

[0056] In the second aspect, please refer to Figure 5. The present application provides a filter array, which includes a regional array arranged in a position corresponding to the photosensitive unit array, and the regional array includes multiple macro-pixel areas, each macro-pixel area includes at least one first filter 100, at least one second filter 200 and at least one third filter 300, the first filter 100 allows light of a first color to pass through, the second filter 200 allows light of a second color to pass through, and the third filter 300 allows light of a third color to pass through.

[0057] Among them, at least one of the first filter 100, the second filter 200 and the third filter 300 includes a first transparent substrate and a filtering micro-nanostructure array arranged on one side of the first transparent substrate. Each filtering micro-nanostructure array includes a plurality of filtering micro-nanostructures 20 arranged in a rectangular array, and each filtering micro-nanostructure 20 is constructed as the filtering micro-nanostructure 20 provided in the aforementioned embodiment.

[0058] The specific structure of the light filtering micro-nano structure 20 refers to the above embodiment. Since the filter array adopts the technical solution of the above embodiment, it has at least all the beneficial effects brought by the technical solution of the above embodiment, which will not be described one by one here.

[0059] In addition, in this embodiment, the filter array is configured as a regional array that is positioned correspondingly to the photosensitive unit array. In this case, each sub-region in the regional array corresponds one-to-one to a single pixel. In a regional array, the sub-regions within the regional array are combined to form a macro-pixel region. During color reconstruction, the macro-pixel region is used as the object, and the color of the macro-pixel region can be reconstructed based on the light energy output by the photosensitive units corresponding to each sub-region within the macro-pixel region. The macro-pixel region includes at least four sub-regions arranged in a square array, that is, the macro-pixel can be a 2×2, 3×3, or 4×4 sub-region square array.

[0060] As can be understood, referring to FIG5 , the filter array includes a transparent medium layer facing all the photosensitive units, and the transparent medium layer is divided into a plurality of block-shaped transparent substrates 10 by a sub-region array. At this time, each transparent substrate 10 forms a filter in combination with the plurality of filter structures arranged thereon.

[0061] Among them, multiple filtering structures can be constructed as a filtering micro-nano structure array, and each filtering micro-nano structure 20 in the filtering micro-nano structure array is constructed as the filtering micro-nano structure 20 provided in the aforementioned embodiment, or the filtering micro-nano structure can also be a commonly used filtering structure. This embodiment is not limited to this, as long as the filter corresponding to at least one color has the filtering micro-nano structure 20 provided in the aforementioned embodiment.

[0062] Of course, the space on one side of the transparent substrate 10 away from the photosensitive unit may not be provided with the filtering micro-nano structure 20, so that this part of the filter substantially allows all light in the visible light band to pass through, that is, allows white light to pass through, to form a visible light all-pass filter.

[0063] For filters whose filtering structures can be constructed as the filtering micro-nanostructures 20 provided in the aforementioned embodiments, multiple identical filtering micro-nanostructures 20 are arranged in a rectangular array with intervals between them on a single transparent substrate 10, as shown in FIG6 , thereby forming a filter micro-nanostructure array. In this case, the filter micro-nanostructure array has a corresponding spectral modulation capability, that is, it allows light of certain wavelengths to pass through while not allowing light of other wavelengths to pass through. In other words, it allows light of a single color to pass through.

[0064] In the embodiment of the present application, the modulation layer made of a transparent material in the light filtering micro-nano structure 20 has a thickness H3, where H3>300 mm. In the light filtering micro-nano structure array, the spacing between the central axes of adjacent light filtering micro-nano structures 20 is P, where 100 nm ≤ P ≤ 600 nm.

[0065] The pitch, P, is the periodicity of the arrangement of the filtering micro-nanostructures within the filtering micro-nanostructure array. In this case, H3 > 300 mm ensures that the optical waveguide structure equivalent to the filtering micro-nanostructure array can provide several intrinsic waveguide modes. Combined with the fact that 100 nm ≤ P ≤ 600 nm, incident light passes through the periodic structure's wavevector matching principle, exciting these intrinsic waveguide modes and achieving spectral modulation.

[0066] In the embodiment of the present application, the third filter 300 is configured as a visible light all-pass filter so that the light allowed to pass through is white light.

[0067] Specifically, the visible light all-pass filter includes only a second transparent substrate and a second transparent protective layer, the second transparent protective layer being disposed on a side of the second transparent substrate facing away from the photosensitive unit array. The second transparent substrate is the transparent substrate 10 in the transparent dielectric layer corresponding to the subregion of the filter array without micro-nanostructures.

[0068] As will be appreciated, at least one sub-region within the macropixel region is free of any micro-nanostructures on the transparent substrate 10, thereby allowing all visible light to pass through. In this case, the filter provided within at least one sub-region within the macropixel region is the third filter 300. As will be appreciated, the visible light all-pass filter approximates full light energy, further increasing the overall light throughput of the filter array.

[0069] In an embodiment of the present application, the macro-pixel area includes one first filter 100, one second filter 200 and two third filters 300, and one first filter 100, one second filter 200 and two third filters 300 are arranged in a 2×2 array; wherein the first filter 100 and the second filter 200 have the filtering micro-nano structure provided by the aforementioned embodiment.

[0070] At this time, the first filter 100 and the second filter 200 allow light of different colors to pass through, that is, the first filter 100 and the second filter 200 have different filtering micro-nano structures. The two filters with different filtering micro-nano structures are combined with two third filters to form a 2×2 array of macro pixels.

[0071] In the embodiment of the present application, the side length of the first transparent substrate is e, and e satisfies: e ≤ 3 μm. Specifically, the side length of the first transparent substrate is less than or equal to 3 μm, so that the filter micro-nanostructure array is distributed within a 3 μm × 3 μm area. That is, in this embodiment, the side length of each filter corresponds to the side length of the small-sized pixel.

[0072] In some embodiments, in the first filter 100, the cross-sectional width of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is D1, where D1 satisfies: 100 nm < D1 < 140 nm. The spacing between the central axes of adjacent filtering micro-nano structures is P1, where P1 satisfies: 200 nm < P1 < 300 nm.

[0073] Specifically, because the dual-layer modulation structure composed of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is a columnar structure, and its cross-sectional shape is a rotationally symmetrical figure with a rotation angle of 90°, when the cross-sectional shape of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 in the first filter 100 is circular, the cross-sectional width D1 is the cross-sectional diameter of the columnar structure. When the cross-sectional shape of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 in the first filter 100 is square, the cross-sectional width D1 is the cross-sectional side length of the columnar structure. The pitch P1 is the arrangement period of the filtering micro-nano structures in the filtering micro-nano structure array.

[0074] In some embodiments, in the second filter 200 , the cross-sectional width of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is D2, 160<D2<200nm, and the spacing between the central axes of adjacent filtering micro-nano structures is P2, 350nm<P2<450nm.

[0075] That is, when the cross-section of the first and second micro-nano modulation layers 21, 22 in the second filter 200 is circular, the cross-sectional width D2 is the cross-sectional diameter of the columnar structure. When the cross-sectional shape of the first and second micro-nano modulation layers 21, 22 is square, the cross-sectional width D2 is the side length of the cross-sectional dimension of the columnar structure. The pitch P2 is the arrangement period of the filtering micro-nano structures in the filtering micro-nano structure array.

[0076] The combination of the arrangement period and shape size parameters provided in this embodiment has a better effect, which can enable the filter array to still have the broadband modulation function of accurately reconstructing colors under low illumination with small-sized pixels.

[0077] In an embodiment of the present application, in the first diagonal direction of the macro-pixel area, at least one first filter 100 and at least one second filter 200 are arranged alternately in sequence; in the second diagonal direction of the macro-pixel area, at least two third filters 300 are arranged in sequence.

[0078] The first diagonal direction and the second diagonal direction are parallel to or perpendicular to each other.

[0079] Referring to Figure 5 , for a 2×2 macropixel region in the upper left corner of an area array, the first filter 100 is located within the upper left subregion, the second filter 200 is located within the lower right subregion, and two third filters 300 are located within the upper right and lower left subregions, respectively. In this case, the first diagonal direction runs from the upper left to the lower right, and the second diagonal direction runs from the upper right to the lower left, both being perpendicular to each other. Of course, either or both of the first filter 100 and the second filter 200 include the light-filtering micro-nanostructure 20 provided in the aforementioned embodiments.

[0080] Next, let's take the example of a first filter 100 and a second filter 200 both having the filtering micro-nanostructures 20 provided in the aforementioned embodiment, and a third filter 300 being a visible light all-pass filter. In this case, the high-transmittance broadband modulation curve of the first filter 100 is M1, the high-transmittance broadband modulation curve of the second filter 200 is M2, and the energy value received by the third filter 300 is approximately the same across all spectral bands, which can be expressed as C. All filtering micro-nanostructures 20 in the first filter 100 and the second filter 200 provide a total of n spectral modulation channels. In this case, the energy values ​​of the three colors of light I1, I2, and I3 received by the macropixel area are expressed as:

[0081] Equation 1:

[0082] Where A is the modulation matrix composed of broadband modulation curves M1, M2 and C, φ(λ n ) is the incident spectrum of the nth spectral modulation channel. Using the compressed sensing algorithm, we can solve equation 1 to obtain the incident spectrum corresponding to the macro pixel. The RGB value of the incident light at the macro pixel position is as follows:

[0083] It can be understood that the compressed sensing algorithm requires that the correlation between the high transmittance broadband modulation curve M1 and the high transmittance broadband modulation curve M2 is small, and as close as possible to the linear combination of the R, G, and B curves. That is, at this time, M1 and M2 satisfy: min||M i -(a·R+b·G+c·B)||2, i=1,2. Here, a, b, and c are constants. The minimum normalized singular value of the modulation matrix A composed of M1, M2, and C, i.e., α=min[SVD(A)] / sum[SVD(A)], should generally be greater than 0.05. SVD(A) is the singular value decomposition (SVD) of the modulation matrix A.

[0084] It can be understood that the first filter 100 and the second filter 200 allow different colors of light to pass through, that is, the specific structures of the filtering micro-nanostructure arrays in the first filter 100 and the second filter 200 are different, which may specifically include at least one of the following: the shape of a single micro-nanostructure is different, the spacing between adjacent micro-nanostructures is different, or the number of micro-nanostructures is different.

[0085] To help those skilled in the art better understand the scope of protection of the claims of this application, the following describes the technical solutions described in the claims of this application through specific implementation examples. It should be understood that the following examples are only used to explain this application and are not used to limit the scope of protection of the claims of this application. In the following examples, the combination of the structural height, arrangement period, and shape and size parameters of the modulation layer has a better effect, which enables the filter array to still have a broadband modulation function that accurately reconstructs colors under low illumination with small-sized pixels.

[0086] Structure 1: Referring to Figure 1 , the transparent substrate 10 is made of silicon dioxide (SiO2). The first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 are both cylindrical structures with circular cross-sections. The first micro-nano modulation layer 21 is made of amorphous Si (α-Si), a light-loss material, while the second micro-nano modulation layer 22 is made of titanium dioxide (TiO2), a transparent material. As will be appreciated, TiO2 has a higher refractive index than SiO2.

[0087] The height of the second micro-nano modulation layer 22 ranges from 200 to 1000 nm, and the spacing between the central axes of adjacent filtering micro-nano structures 20 is between 200 and 500 nm to ensure that there are multiple waveguide modes for modulation within the double-layer modulation structure. The spacing varies depending on the specific structure and material of the filtering micro-nano structure. To ensure a large light flux and enhance broadband modulation capability with a small number of micro-nano structures, the height of the first micro-nano modulation layer 21 is between 20 and 100 nm. The overall duty cycle of the first micro-nano modulation layer 21 and the second micro-nano modulation layer 22 is between 0.2 and 0.8 to ensure that the structure is easy to etch and prepare.

[0088] Based on the above structure 1, two specific examples are provided:

[0089] Example 1: The height of the first micro-nano modulation layer 21 (α-Si) is 62.8 nm, the height of the second micro-nano modulation layer 22 (TiO2) is 465.4 nm, the spacing is 265.2 nm, and the duty cycle is 0.31;

[0090] Example 2: The height of the first micro-nano modulation layer 21 (α-Si) is 62.8 nm, the height of the second micro-nano modulation layer 22 (TiO2) is 465.4 nm, the spacing is 377.3 nm, and the duty cycle is 0.57.

[0091] The first filter 100 is formed using the light-filtering micro-nanostructure 20 provided in Example 1, and the second filter 200 is formed using the light-filtering micro-nanostructure 20 provided in Example 2. In a 2×2 macro-pixel area, the first filter 100 is located in the upper-left sub-area, the second filter 200 is located in the lower-right sub-area, and two third filters 300 that allow white light to pass are located in the upper-right and lower-left sub-areas, respectively.

[0092] Please refer to Figure 7, which shows the high-transmittance broadband modulation curves of Examples 1 and 2. It can be seen that the average transmittance of the broadband modulation curves of Examples 1 and 2 reaches 75.4% and 68.6%, respectively. Please refer to Figure 8. The image on the left of Figure 8 is the reference image, which is the true image; the image on the right of Figure 8 is the color image reconstructed using the high-transmittance broadband modulation curves of Examples 1 and 2. The color accuracy of the color image is measured using the color difference quantification indicator ΔE (delta-E) in the CIELAB color space. The average color deviation ΔE of the color image is as low as 0.87, indicating that the filter arrays of Examples 1 and 2 accurately reconstruct the image color.

[0093] Structure 2: See Figure 4 . The transparent substrate 10 is made of SiO2. The first and second micro-nano modulation layers 21 and 22 are both cylindrical structures with circular cross-sections. The first micro-nano modulation layer 21 is made of the transparent material silicon nitride Si3N4, while the second micro-nano modulation layer 22 is made of polycrystalline Si (p-Si), a light-loss material.

[0094] The height of the first micro-nano modulation layer 21 is between 200-1500 nm, with a spacing P between 200-500 nm to ensure multiple waveguide modes within the dual-layer modulation structure for modulation. To ensure maximum light flux and modulation capability, the height of the second micro-nano modulation layer 22 is between 30-200 nm. The overall duty cycle of the first and second micro-nano modulation layers 21, 22 is between 0.2-0.8, ensuring easy etching and fabrication of the structure.

[0095] Based on the above structure 2, two specific examples are provided:

[0096] Example 3: The height of the first micro-nano modulation layer 21 (Si3N4) is 431.3 nm, the height of the second micro-nano modulation layer 22 (p-Si) is 76.5 nm, the spacing is 269.2 nm, and the duty cycle is 0.44;

[0097] Example 4: The height of the first micro-nano modulation layer 21 (Si3N4) is 431.3 nm, the height of the second micro-nano modulation layer 22 (p-Si) is 76.5 nm, the spacing is 347.9 nm, and the duty cycle is 0.54.

[0098] The first filter 100 is formed using the light-filtering micro-nanostructure 20 provided in Example 3, and the second filter 200 is formed using the light-filtering micro-nanostructure 20 provided in Example 4. In a 2×2 macro-pixel area, the first filter 100 is located in the upper-left sub-area, the second filter 200 is located in the lower-right sub-area, and two third filters 300 that allow white light to pass are located in the upper-right and lower-left sub-areas, respectively.

[0099] Please refer to Figure 9, which shows the high-transmittance broadband modulation curves for Examples 3 and 4. As can be seen, the average transmittance of the broadband modulation curves for Examples 3 and 4 reached 65.7% and 72.7%, respectively. The average color deviation ΔE of the reconstructed color image was as low as 1.13, demonstrating that the filter arrays of Examples 3 and 4 accurately reconstructed the image colors.

[0100] Structure 3: See Figure 3. The transparent substrate 10 is made of SiO2. The first and second micro-nano modulation layers 21 and 22 are both constructed as columnar structures with square cross-sections. The first micro-nano modulation layer 21 is made of polycrystalline Si (p-Si), a light-loss material, while the second micro-nano modulation layer 22 is made of titanium dioxide (TiO2), a transparent material.

[0101] The height of the first micro-nano modulation layer 21 is between 20-100 nm, with a spacing P between 200-500 nm to ensure that the dual-layer modulation structure has multiple waveguide modes for modulation. To ensure maximum light flux and modulation capability, the height of the second micro-nano modulation layer 22 is between 200-1000 nm. The overall duty cycle of the first and second micro-nano modulation layers 21, 22 is between 0.2-0.8, ensuring easy etching and fabrication of the structure.

[0102] Based on the above structure 3, two specific examples are provided:

[0103] Example 5: The height of the first micro-nano modulation layer 21 (p-Si) is 83.6 nm, the height of the second micro-nano modulation layer 22 (TiO2) is 313.2 nm, the spacing is 379.7 nm, and the duty cycle is 0.41;

[0104] Example 6: The height of the first micro-nano modulation layer 21 (p-Si) is 83.6 nm, the height of the second micro-nano modulation layer 22 (TiO2) is 313.2 nm, the spacing is 271.6 nm, and the duty cycle is 0.62.

[0105] The first filter 100 is formed using the light-filtering micro-nanostructure 20 provided in Example 5, and the second filter 200 is formed using the light-filtering micro-nanostructure 20 provided in Example 6. In a 2×2 macropixel, the first filter 100 is located in the upper-left subregion, the second filter 200 is located in the lower-right subregion, and two third filters 300 that allow white light to pass are located in the upper-right and lower-left subregions, respectively.

[0106] Please refer to Figure 10, which shows the high-transmittance broadband modulation curves for Examples 5 and 6. As can be seen, the average transmittances of the broadband modulation curves for Examples 5 and 6 reach 77.9% and 63.8%, respectively. The average color deviation ΔE of the reconstructed color image is as low as 1.21, demonstrating that the filter arrays of Examples 5 and 6 accurately reconstruct image colors.

[0107] The above descriptions are some embodiments of the present application and are not intended to limit the patent scope of the present application. All equivalent structural transformations made using the contents of the present application specification and drawings under the inventive concept of the present application, or direct / indirect application in other related technical fields are included in the patent protection scope of the present application.

Claims

1. A light filtering micro-nano structure, comprising: A first micro-nano modulation layer, wherein the first micro-nano modulation layer is disposed on a transparent substrate of the filter, and a material of the first micro-nano modulation layer is one of a transparent material and an optical loss material, and a refractive index of the optical loss material is higher than a refractive index of the transparent material; A second micro-nano modulation layer, wherein the second micro-nano modulation layer is disposed on a side of the first micro-nano modulation layer away from the transparent substrate, and the material of the second micro-nano modulation layer is the other of the transparent material and the light loss material; A transparent protective layer, the transparent protective layer covers the first micro-nano modulation layer and the second micro-nano modulation layer and is connected to the transparent substrate; The refractive index of the transparent material is higher than the refractive index of the material of the transparent substrate and the transparent protective layer.

2. The light filtering micro-nanostructure according to claim 1, wherein: The transparent material comprises silicon nitride Si3N4 or titanium dioxide TiO2; and / or The optical loss material includes polycrystalline silicon P-Si, amorphous silicon α-Si or germanium Ge.

3. The light filtering micro-nanostructure according to claim 1, wherein: The first micro-nano modulation layer and the second micro-nano modulation layer are both constructed as columnar structures, and the cross-sectional shapes of the first micro-nano modulation layer and the second micro-nano modulation layer are both rotationally symmetrical figures with a rotation angle of 90°.

4. The light filtering micro-nanostructure according to claim 1, wherein: The thickness of the transparent substrate is greater than 3.5 μm.

5. The light filtering micro-nanostructure according to claim 1, wherein: The overall duty cycle of the first micro-nano modulation layer and the second micro-nano modulation layer is η, 0.2≤η≤0.

8.

6. The light filtering micro-nanostructure according to claim 1, wherein: In the first micro-nano modulation layer and the second micro-nano modulation layer, the thickness of the modulation layer made of the optical loss material is H2, and 10nm≤H2≤100nm.

7. A filter array comprising: A regional array arranged correspondingly in position to the photosensitive unit array, wherein the regional array includes a plurality of macro-pixel regions, each of the macro-pixel regions includes at least one first filter, at least one second filter, and at least one third filter, wherein the first filter allows light of a first color to pass through, the second filter allows light of a second color to pass through, and the third filter allows light of a third color to pass through; Wherein, at least one of the first filter, the second filter and the third filter includes a first transparent substrate and a light filtering micro-nano structure array arranged on one side of the first transparent substrate, the light filtering micro-nano structure array includes a plurality of light filtering micro-nano structures arranged in a rectangular array, and the light filtering micro-nano structure is constructed as the light filtering micro-nano structure as described in any one of claims 1 to 6.

8. The filter array according to claim 7, wherein: In the light filtering micro-nano structure, the thickness of the modulation layer made of transparent material is greater than 300 mm; and in the light filtering micro-nano structure array, the spacing between the central axes of adjacent light filtering micro-nano structures is P, 100 nm≤P≤600 nm.

9. The filter array according to claim 8, wherein: The third filter is configured as a visible light all-pass filter so that the light allowed to pass is white light; The visible light all-pass filter comprises a second transparent substrate and a second transparent protective layer, wherein the second transparent protective layer is arranged on a side of the second transparent substrate away from the photosensitive unit array.

10. The filter array according to claim 9, wherein: The macro pixel area includes one first filter, one second filter and two third filters, and one first filter, one second filter and two third filters are arranged in a 2×2 array; Wherein, both the first filter and the second filter have the light filtering micro-nano structure as described in any one of claims 1 to 6.

11. The filter array according to claim 10, wherein: The side length of the first transparent substrate is less than or equal to 3 μm; Among them, the cross-sectional width of the first micro-nano modulation layer and the second micro-nano modulation layer in the first filter is D1, D1 satisfies: 100<D1<140nm, the spacing between the central axes of adjacent filtering micro-nano structures is P1, P1 satisfies 200<P1<300nm; the cross-sectional width of the first micro-nano modulation layer and the second micro-nano modulation layer in the second filter is D2, 160<D2<200nm, the spacing between the central axes of adjacent filtering micro-nano structures is P2, 350nm<P2<450nm.

12. The filter array according to claim 9, wherein: In a first diagonal direction of the macro pixel area, at least one of the first filters and at least one of the second filters are alternately arranged in sequence; In the second diagonal direction of the macro pixel area, at least two of the third filters are arranged in sequence; The first diagonal direction and the second diagonal direction are parallel to each other or perpendicular to each other.

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