Multilayer array type micropore neutral density integrated optical filter

Abstract

The invention discloses a multilayer array type micropore neutral density integrated optical filter, which comprises a transparent conducting layer, an optical filtering layer, an optical substrate, a neutral attenuation layer, a light blocking layer and an anti-reflection absorption layer, and is characterized in that the optical filtering layer and the transparent conducting layer are sequentially plated on the upper surface of the optical substrate, and the neutral attenuation layer is plated on the lower surface of the optical substrate; a light blocking layer and an anti-reflection absorption layer are sequentially plated on the surface of the neutral attenuation layer; the light blocking layer and the anti-reflection absorption layer are provided with array micropore structures. The defects in the prior art are overcome, a traditional discrete structure is replaced by single-chip multifunctional integration, and the functions of electrostatic protection, filtering, light intensity attenuation and absorption and reflection reduction can be achieved at the same time.

Description

Technical Field

[0001] This invention relates to the field of optical thin film and photolithography technology, specifically to a multilayer array-type microporous neutral density integrated filter. Background Technology

[0002] Digital sun sensors are crucial components for spacecraft attitude control. By capturing the orientation of the sun's vector within a celestial coordinate system, they provide a high-precision attitude reference for the spacecraft. Their core technology is based on the pinhole imaging principle, combining photoelectric conversion and digital signal processing to achieve accurate measurement of the sun's angle. The optical path system located at the front of the detector needs to guide sunlight to the detector's field of view in accordance with the pinhole imaging principle, filtering out excessive space radiation, reducing multiple reflections, and improving the signal-to-noise ratio.

[0003] The existing optical path system mainly consists of a three-stage discrete structure of window, light inlet, and attenuator. It accounts for a large proportion of the mass and volume, and many components need to be assembled and calibrated independently, which is time-consuming, labor-intensive, and economically inefficient. Summary of the Invention

[0004] The purpose of this invention is to provide a multi-layer array-type microporous neutral density integrated filter. In view of the above-mentioned shortcomings, this invention replaces the traditional discrete structure with a single-piece multi-functional integrated filter, which can simultaneously provide electrostatic protection, filtering, light intensity attenuation and absorption anti-reflection functions.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is: a multilayer array-type microporous neutral density integrated filter, characterized in that: the multilayer array-type microporous neutral density integrated filter includes a transparent conductive layer, a filter layer, an optical substrate, a neutral attenuation layer, a light blocking layer, and an anti-reflection absorption layer; the filter layer and the transparent conductive layer are successively deposited on the upper surface of the optical substrate, the neutral attenuation layer is deposited on the lower surface of the optical substrate, and the light blocking layer and the anti-reflection absorption layer are successively deposited on the surface of the neutral attenuation layer; the light blocking layer and the anti-reflection absorption layer are provided with an array of microporous structures.

[0006] Furthermore, the array microporous structure corresponds to a fixed transmittance of the overall membrane system within the microporous region in the 400–760 nm wavelength range, an average transmittance of less than 1% in the 800–1800 nm wavelength range, and an array-type porous structure that meets the requirements of pinhole imaging. The array-type porous structure forms an array microporous structure.

[0007] Furthermore, the transparent conductive layer is plated with ITO material, in which the In2O3:SnO2 ratio is 7:3 or 8:2.

[0008] Furthermore, the filter layer's film system includes two modules, a and b. Module a consists of L / / M / / H / / M / / L and L / / M / / 2H / / M / / L.

[0009] Module b consists of a passband λ / 4 multi-layer structure, with the multi-level structure being 0.5L / / H / / 0.5L;

[0010] H, M, and L are three types of high, medium, and low refractive index coating materials that are transparent in the visible light band, with extinction coefficients below 0.01.

[0011] Furthermore, the optical substrate is made of a transparent material in the range of 400–760 nm.

[0012] Furthermore, the array microporous structure consists of a light-blocking layer and an anti-reflection absorption layer. Using metal deposition and photolithography, N-type nanoporous structures are formed around the center of the central attenuation layer by etching. 2 A symmetrical array of microporous structures, where N is a natural number.

[0013] Furthermore, both the neutral attenuation layer and the antireflection absorption layer are metal interference filter film structures. The overall film system outside the micropore region corresponding to the array micropore structure has a reflectivity of less than 1% in the 400–760 nm wavelength band. The metal interference filter film structure is A / / B / / A, where A is a metal material and B is a transparent material in the visible light band, with an extinction coefficient of less than 0.01.

[0014] A method for fabricating a multilayer array-type microporous neutral density integrated filter, characterized by comprising the following steps:

[0015] S1. On the upper surface of the optical substrate, four thin film materials are used to deposit the filter layer and transparent conductive layer layer by layer through vacuum deposition, using electron beam and anti-evaporation supplemented by ion beam and heating process.

[0016] S2. A neutral attenuation layer is formed on the lower surface of the optical substrate by alternating metal and dielectric coating materials.

[0017] S3. Using photolithography, photoresist is coated onto the outer surface of the neutral attenuation layer. Image exposure and development are then performed to form an N-type neutral attenuation layer on its surface. 2 A symmetrical photoresist array structure; then, a light-blocking layer and an anti-reflection absorption layer are successively deposited on the surface covering the photoresist array structure;

[0018] S4. In the photolithography area, the photoresist array is stripped to form an N×N array microporous structure.

[0019] Furthermore, in step S1, the membrane structure is as follows:

[0020] 0.5A / / 0.63 (AB 2C BA) 8 / / 0.52(AB 2C BA) 8 / / 0.43(AB 2C BA) 8 / / 1.15(0.5AC 0.5A) / / (0.5AC 0.5A) 5 / / 1.2(0.5AC 0.5A) / / 0.37D

[0021] In the above membrane system, A, B, C, and D are MgF2, Al2O3, TiO2, and ITO, respectively, and the design center wavelength of the membrane system is 860 nm.

[0022] In step S2, the membrane structure is as follows:

[0023] 19.98Ap / / 183.8Bp / / 18.35Ap / / 141.47Bp / / 19.82Ap / / 107.34Bp / / 13.62Ap / / 15.04Bp

[0024] In the film system, A and B are Cr and SiO2, respectively, and p represents the physical thickness in nanometers.

[0025] Furthermore, the light-blocking layer is a 100 nm thick Cr film, and the anti-reflection absorption layer is an 8-layer metal interference filter film;

[0026] In step S3, the membrane structure is as follows:

[0027] 100Ap / / 89.71Lp / / 3.19Ap / / 272.41Lp / / 16.04Ap / / 37.3Lp / / 50.73Lp / / 6.8Ap / / 81.93Lp

[0028] In the film system, A represents Cr, L represents SiO2, and p represents the physical thickness in nanometers.

[0029] In view of the above technical features, the present invention has the following beneficial effects:

[0030] 1. This invention discloses a multi-layer array-type micro-aperture neutral density integrated filter, the structure of which includes a transparent conductive layer, a filter layer, an optical substrate, a neutral attenuation layer, a light blocking layer, and an anti-reflection absorption layer. The design integrates the functions of a window, a light introducer, and an attenuator on the same optical substrate. This single-chip multi-functional integrated design replaces the traditional discrete structure, simultaneously meeting the requirements of pinhole imaging, light intensity attenuation, and stray light suppression. It features lightweight construction and a high degree of integration.

[0031] 2. The present invention discloses a multilayer array-type microporous neutral density integrated filter, wherein the transparent conductive layer is plated with ITO material to achieve electrostatic protection. The filter layer performs filtering function, the neutral attenuation layer performs light intensity attenuation function, and the anti-reflection absorption layer performs absorption and anti-reflection function.

[0032] 3. The multilayer array microporous neutral density integrated filter of the present invention has the advantages of high integration, high precision and low cost. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the structure of a multilayer array-type microporous neutral density integrated filter in specific embodiment 1;

[0034] Figure 2 This is a schematic diagram of the light-blocking layer and the anti-reflection absorption layer in specific embodiment 1;

[0035] Figure 3 The filter layer in Specific Implementation 1 is designed with a spectrum in the 400–1800 nm wavelength range;

[0036] Figure 4 The neutral attenuation layer in Specific Implementation Example 1 is designed with a spectrum in the 400–760 nm wavelength range;

[0037] Figure 5 The antireflection absorption layer in Specific Implementation 1 is designed with a spectrum in the 400–760 nm wavelength range.

[0038] In the figure: 1. Transparent conductive layer; 2. Filter layer; 3. Optical substrate; 4. Neutral attenuation layer; 5. Light blocking layer; 6. Anti-reflection absorption layer; 7. Array microporous structure. Detailed Implementation

[0039] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0040] See Figures 1 to 5 Specific embodiment 1: This embodiment 1 provides a multilayer array-type microporous neutral density integrated filter, characterized in that: the multilayer array-type microporous neutral density integrated filter includes a transparent conductive layer 1, a filter layer 2, an optical substrate 3, a neutral attenuation layer 4, a light blocking layer 5, and an anti-reflection absorption layer 6. The filter layer 2 and the transparent conductive layer 1 are successively deposited on the upper surface of the optical substrate 3, and the neutral attenuation layer 4 is deposited on the lower surface of the optical substrate 3. The light blocking layer 5 and the anti-reflection absorption layer 6 are successively deposited on the surface of the neutral attenuation layer 4. The light blocking layer 5 and the anti-reflection absorption layer 6 are provided with an array microporous structure 7.

[0041] The array microporous structure 7 corresponds to a fixed transmittance of the overall film system within the microporous region in the 400–760 nm wavelength range, an average transmittance of less than 1% in the 800–1800 nm wavelength range, and an array-type porous structure that meets the requirements of pinhole imaging. This array-type porous structure forms the array microporous structure 7. The fixed transmittance is generally determined based on the detector's response to the solar spectrum, such as 0.001, 0.01, 0.02, etc. Traditional neutral density filters are plated with NiCr alloy, which results in a slope and uneven transmittance in the visible light band. Therefore, a metal-dielectric composite is used to maintain a smooth transmittance even under very low transmittance requirements (see [reference]). Figure 4 ).

[0042] The transparent conductive layer 1 is plated with ITO material, where the ratio of In₂O₃ (indium oxide) to SnO₂ (tin dioxide) is 7:3 or 8:2. Electrostatic protection is achieved by depositing an ITO thin film of a certain thickness on the outer layer of the filter layer 2. To ensure conductivity and reliability, the thickness of the ITO thin film is generally greater than 100 nm and less than 500 nm.

[0043] To eliminate higher-order reflection bands and extended reflection regions, filter layer 2 is designed using three materials. The film system of filter layer 2 consists of two modules, a and b. Module a is composed of L / / M / / H / / M / / L and L / / M / / 2H / / M / / L, that is, a five-layer basic structure composed of three materials to achieve short-wavelength suppression.

[0044] Module b consists of a passband λ / 4 multilayer structure, with the multilayer structure being 0.5L / / H / / 0.5L, composed of two materials with high and low refractive indices, achieving high transmittance in the visible light band and near-infrared suppression.

[0045] H, M, and L are three types of high, medium, and low refractive index coating materials that are transparent in the visible light band, with extinction coefficients below 0.01.

[0046] The optical substrate 3 adopts a monolithic structure, which reduces the difficulty of assembly and calibration, improves accuracy, and saves debugging time and development costs. The optical substrate 3 uses transparent materials in the range of 400-760 nm, such as quartz, sapphire, BK7 glass, K9 glass and other optical glasses. Its processing generally needs to meet basic optical grade requirements, such as: surface accuracy N≤4, RMS≤1 / 10λ, and surface finish better than IV grade or 40 / 20.

[0047] Traditional methods require aligning, stacking, and fixing multiple substrates coated with different functional films one by one into a complex lens mount using metal frames, adhesives, etc. This is a three-dimensional and cumbersome mechanical assembly process. When these discrete substrates are installed into the lens mount, manual adjustment is required using washers, threads, etc., to ensure that the surfaces of each substrate are as parallel as possible. This adjustment process relies entirely on the skill of the machinist and the precision of the adjustment tools (such as dial indicators). The multi-layer array-type microporous neutral density integrated filter of Embodiment 1 integrates all optical functional areas (microporous array areas) on the same reference plane. This reference plane undergoes high-precision polishing during manufacturing, achieving a surface shape accuracy of λ / 10 or even higher. The "parallelism" between different functional areas is essentially determined by the flatness of the substrate itself. They are naturally parallel, and the parallelism error is directly improved from the "arcsecond" level of mechanical adjustment to the "wavelength" level (e.g., λ / 10, corresponding to approximately 0.2 arcseconds) of the substrate flatness, achieving the high precision advantage of this invention.

[0048] This embodiment 1 presents a multi-layer array-type microporous neutral density integrated filter, which saves on multiple independent lens frames, adhesives, and substrate materials, simplifying the "multiple coatings" process to "two coatings." Vacuum coating machines consume significant energy during evacuation, heating, and the coating process itself. Reducing the evacuation process from multiple times to two times directly saves over 90% of energy and time costs, achieving the low-cost advantage of this invention.

[0049] The array microporous structure 7 consists of a light-blocking layer 5 and an anti-reflection absorption layer 6. Using metal deposition and photolithography, N-type nanoporous structures are formed around the center of the central attenuation layer 4 by etching. 2 A symmetrical array of micropores, where N is a natural number. A light-blocking layer 5 is deposited on the lower surface of the optical substrate 3. The light-blocking layer is typically deposited using metallic materials such as Cr (chromium), Ni (nickel), Al (aluminum), Ag (silver), etc. Its thickness must meet the penetration depth requirements, and the visible light transmittance must be lower than OD 4, i.e., optical density ≥ 4.

[0050] Both the neutral attenuation layer 4 and the antireflection absorption layer 6 are metal interference filter film structures. The overall film system outside the micropore region corresponding to the array micropore structure 7 has a reflectivity of less than 1% in the 400-760 nm wavelength band. The metal interference filter film structure is A / / B / / A, which serves as the basic unit of the film system. A is a metal material, and B is a transparent material in the visible light band with an extinction coefficient of less than 0.01.

[0051] The neutral attenuation layer 4 is designed using the "potential transmission" theory to achieve neutral transmission in a specific wavelength band. This film structure exhibits significant absorption, the magnitude of which depends not only on the optical constants of the metallic material but also closely on the optical admittance of the adjacent medium. The film system design requires precise matching of the optical admittance of the film system with that of the load to achieve the overall transmission, reflection, and absorption requirements.

[0052] A metal interference filter structure is used to achieve a wide and deep cutoff in the antireflection absorption layer 6, with a designed reflectivity target of 0 in the 400–760 nm wavelength band. Here, "cutoff" means that "0" transmittance is achieved through this structure, that is, the transmittance is 0 or close to 0 at a certain wavelength.

[0053] A method for fabricating a multilayer array-type microporous neutral density integrated filter, characterized by comprising the following steps:

[0054] S1. On the upper surface of the optical substrate 3, four thin film materials are deposited layer by layer using vacuum deposition, employing electron beam and resistive evaporation supplemented by ion beam and heating processes to complete the deposition of the filter layer 2 and the transparent conductive layer 1. That is, the deposition is completed using an ion source and heating assistance. In step S1, the film structure is as follows:

[0055] 0.5A / / 0.63 (AB 2C BA) 8 / / 0.52(AB 2C BA) 8 / / 0.43(AB 2C BA) 8 / / 1.15(0.5AC 0.5A) / / (0.5AC 0.5A) 5 / / 1.2(0.5AC 0.5A) / / 0.37D

[0056] In the above membrane system, A, B, C, and D are MgF2 (magnesium fluoride), Al2O3 (alumina), TiO2 (titanium dioxide), and ITO materials, respectively. The designed center wavelength of the membrane system is 860 nm; the transmittance is shown in the appendix. Figure 3 This reduces the impact of energy transmitted in non-operating bands on the detector, thereby improving accuracy.

[0057] S2. A neutral attenuation layer 4 is formed on the lower surface of the optical substrate 3 by alternating deposition of metal and dielectric coating materials; in step S2, the film structure is as follows:

[0058] 19.98Ap / / 183.8Bp / / 18.35Ap / / 141.47Bp / / 19.82Ap / / 107.34Bp / / 13.62Ap / / 15.04Bp

[0059] In the film system, A and B represent Cr (chromium) and SiO2 (silicon dioxide), respectively, and p represents the physical thickness in nanometers. The transmittance of the neutral attenuation layer 4 is shown in the appendix. Figure 4 Compared with traditional attenuators, the neutral attenuation layer 4 in this embodiment 1 has a flat transmittance, which can also improve accuracy.

[0060] S3. Using photolithography, photoresist is coated onto the outer surface of the neutral attenuation layer 4. Image exposure and development are then performed to form an N-type layer on its surface. 2 A symmetrical photoresist array structure is formed; then, a light-blocking layer 5 and an anti-reflection absorption layer 6 are successively deposited on the surface covering the photoresist array structure; the light-blocking layer 5 is a 100 nm thick Cr film, and the anti-reflection absorption layer 6 is an 8-layer metal interference filter film.

[0061] In step S3, the membrane structure is as follows:

[0062] 100Ap / / 89.71Lp / / 3.19Ap / / 272.41Lp / / 16.04Ap / / 37.3Lp / / 50.73Lp / / 6.8Ap / / 81.93Lp

[0063] In the film system, A represents Cr, L represents SiO2, and p represents the physical thickness in nanometers. The reflectance spectrum of the antireflection absorption layer 6 is shown in the appendix. Figure 5 This reduces residual reflection between the film surface and the detector in the working band, thereby improving positioning accuracy.

[0064] S4. In the photolithography area, the photoresist array is peeled off to form an N×N array micropore structure 7.

[0065] The above description is merely a preferred embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A multilayer arrayed microwell neutral density integrated optical filter, characterized by: The multilayer array microporous neutral density integrated filter comprises a transparent conductive layer (1), a filter layer (2), an optical substrate (3), a neutral attenuation layer (4), a light blocking layer (5) and an anti-reflection absorption layer (6), the upper surface of the optical substrate (3) is coated with the filter layer (2) and the transparent conductive layer (1) in sequence, the lower surface of the optical substrate (3) is coated with the neutral attenuation layer (4), and the surface of the neutral attenuation layer (4) is coated with the light blocking layer (5) and the anti-reflection absorption layer (6) in sequence; the light blocking layer (5) and the anti-reflection absorption layer (6) are provided with an array microporous structure (7).

2. The multilayer arrayed microporous neutral density integrated optical filter according to claim 1, wherein: The array microporous structure (7) has a fixed transmittance in the 400-760 nm waveband, an average transmittance lower than 1% in the 800-1800 nm waveband, and an array microporous structure meeting the requirements of small hole imaging.

3. The multilayer arrayed microporous neutral density integrated optical filter of claim 1, wherein: The transparent conductive layer (1) is coated with ITO material, and the In2O3:SnO2 in the ITO material is 7:3 or 8:

2.

4. The multilayer arrayed microporous neutral density integrated optical filter of claim 1, wherein: The film system of the filter layer (2) comprises two modules a and b, the module a is composed of L / / M / / H / / M / / L and L / / M / / 2H / / M / / L; The module b is composed of a passband λ / 4 multilayer structure, and the multilayer structure is 0.5L / / H / / 0.5L; H, M and L are three kinds of high, medium and low refractive index coating materials transparent in the visible light waveband, and the extinction coefficient is lower than 0.

01.

5. The multilayer arrayed microporous neutral density integrated optical filter of claim 1, wherein: The optical substrate (3) is made of a material transparent in the range of 400-760 nm.

6. The multilayer arrayed microporous neutral density integrated optical filter of claim 1, wherein: The array micro-hole structure (7) is composed of the light-blocking layer (5) and the anti-reflection absorption layer (6), and N 2 symmetrical array micro-hole structures are formed on the surface of the central attenuation layer (4) by using metal plating and photoetching process, and N is a natural number.

7. The multilayer arrayed microporous neutral density integrated optical filter of claim 1, wherein: The film systems of the neutral attenuation layer (4) and the anti-reflection absorption layer (6) are both metal interference filter film structures, the overall film system outside the array microporous structure (7) corresponding to the microporous region has a reflectivity lower than 1% in the 400-760 nm waveband, the metal interference filter film structure is A / / B / / A, A is a metal material, B is a visible light waveband transparent material, and the extinction coefficient is lower than 0.

01.

8. A method of fabricating the multilayer arrayed microwell neutral density integrated optical filter according to any one of claims 1 to 7, characterized in that, The method comprises the following steps: S1, on the upper surface of the optical substrate (3), using four kinds of thin film materials, through vacuum coating, using electron beam and resistance evaporation assisted by ion beam and heating process to complete the coating of the filter layer (2) and the transparent conductive layer (1) layer by layer; S2, on the lower surface of the optical substrate (3), using metal and dielectric coating materials to coat alternately as the neutral attenuation layer (4); S3, using photolithography process, coating photoresist on the outer surface of neutral attenuation layer (4), image exposure and development, forming N 2 symmetrical photoresist array structure on its surface; then plating light-blocking layer (5) and anti-reflection absorption layer (6) on the surface covered with photoresist array structure; S4, in the lithography area, stripping the photoresist array to form an N×N array microporous structure (7).

9. The preparation method of the multilayer array microporous neutral density integrated filter according to claim 8, wherein: In step S1, the film system structure is: 0.5A / / 0.63 (A B 2C B A) 8 / / 0.52 (A B 2C B A) 8 / / 0.43 (A B 2C B A) 8 / / 1.15 (0.5A C 0.5A) / / (0.5A C 0.5A) 5 / / 1.2 (0.5A C 0.5A) / / 0.37D In the above film system, A, B, C and D are MgF2, Al2O3, TiO2 and ITO respectively, and the design center wavelength of the film system is 860 nm; In step S2, the film system structure is: 19.98Ap / / 183.8Bp / / 18.35Ap / / 141.47Bp / / 19.82Ap / / 107.34Bp / / 13.62Ap / / 15.04Bp In the film system, A and B are Cr and SiO2 respectively, and p represents the physical thickness, which is in nanometers.

10. The method for preparing a multilayer array-type microporous neutral density integrated filter according to claim 9, characterized in that: The light-blocking layer (5) is a 100 nm thick Cr film, and the anti-reflection and absorption layer (6) is an 8-layer metal interference filter film; In step S3, the film system structure is: 100Ap / / 89.71Lp / / 3.19Ap / / 272.41Lp / / 16.04Ap / / 37.3Lp / / 50.73Lp / / 6.8Ap / / 81.93Lp In the film system, A is Cr, L is SiO2, and p represents the physical thickness, in nanometers.

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