A centimeter-level large-size voltage-driven tuning infrared filter based on piezoelectric ceramics and a preparation process and application thereof

Abstract

The application discloses a centimeter-level large-size voltage-driven tuning infrared filter based on a piezoelectric ceramic and a preparation process and application thereof, and belongs to the technical field of dynamic filters. The centimeter-level large-size voltage-driven tuning infrared filter adopts a piezoelectric ceramic as a supporting column, the piezoelectric ceramic is arranged between a static mirror and a dynamic mirror, and an F-P resonant cavity is formed between the static mirror and the dynamic mirror. The static mirror and the dynamic mirror are independently processed, are supported by the piezoelectric ceramic and are bonded into an integrated whole, and therefore, the traditional MEMS sacrificial layer process is not needed, and problems such as a release area of a sacrificial layer, residual stress and structure collapse are not limited.

Description

Technical Field

[0001] This invention belongs to the field of dynamic filter technology, and particularly relates to a large-size, centimeter-scale voltage-driven tuned infrared filter based on piezoelectric ceramics, its fabrication process, and its application. Background Technology

[0002] Traditional infrared detection chips employ a single intensity detection mode, providing only two-dimensional spatial imaging (x, y) of the target. This has several drawbacks: they cannot avoid interference bands in complex environments and cannot meet the requirements for clear target identification in camouflage and concealment scenarios. The new generation of infrared spectral integrated detection chips fully utilizes the "fingerprint recognition" characteristics of the infrared spectrum, integrating infrared spectral information with intensity detection to achieve multi-dimensional spectral detection technology (x, y, λ), which is an effective way to improve target identification capabilities and resistance to environmental interference. The core of high-performance spectral integrated detection technology research is the dynamically tuned filter.

[0003] Currently, the main technical approach focuses on suspended microbridge filtering schemes based on the Fabry-Perot (FP) principle. Under the bias of the upper and lower electrodes, the voltage-driven deformation and expansion of the piezoelectric ceramic changes the suspension height, thereby adjusting the filter cavity length and achieving active selection of the filter. The integrated fabrication approach based on existing microsurface sacrificial layer technology has the following drawbacks: Firstly, due to the special nature of the suspended structure, the upper bridge surface is prone to tilting and bending under the influence of external environmental factors such as temperature and pressure. Especially in vacuum and low-temperature environments, stress mismatch issues exist on the bridge surface, making it difficult to integrate and effectively use in cooled infrared detectors. Secondly, due to the integrated fabrication of microsurface devices, the area generally does not exceed the millimeter scale, making it impossible to cover the entire infrared focal plane array chip.

[0004] Therefore, the following technical problems exist in the prior art:

[0005] 1. Traditional microFP filters (miniature Fabry-Perot filters) made based on MEMS (microelectromechanical systems) technology have limited effective filtering area, which cannot reach the centimeter level, thus limiting their use as infrared lenses;

[0006] 2. Traditional tunable filters use mechanical force for tuning, and the tuning speed is on the order of seconds, which cannot achieve high-speed scanning applications. Summary of the Invention

[0007] To increase the light-transmitting area of ​​the filter and meet the requirements of applications such as high-speed scanning, this invention provides a centimeter-scale large-size voltage-driven tunable infrared filter based on piezoelectric ceramics and its fabrication process. This voltage-driven tunable infrared filter uses piezoelectric ceramics as support pillars, fully utilizing their high-speed displacement adjustment characteristics under voltage drive to achieve adjustment of the resonant cavity length.

[0008] A further technical problem to be solved by the present invention is to provide an application of a large-size, voltage-driven tuned infrared filter based on piezoelectric ceramics.

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A large-size, voltage-driven tuned infrared filter based on piezoelectric ceramics is disclosed. The filter uses piezoelectric ceramics as support pillars and is placed between a stationary mirror and a moving mirror to form an FP resonant cavity between the two mirrors.

[0011] The fabrication process of the aforementioned centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics includes the following steps:

[0012] S1: Prepare moving and still shots;

[0013] S2: Apply adhesive to the corresponding position on the stationary mirror and vertically attach the piezoelectric ceramic to the surface of the stationary mirror;

[0014] S3: After the adhesive has cured, apply adhesive again to the upper surface of the piezoelectric ceramic, align the moving mirror with the upper surface of the piezoelectric ceramic to connect the moving mirror and the piezoelectric ceramic into a single structure, and obtain a centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramic.

[0015] The beneficial effects of this invention are as follows:

[0016] (1) The centimeter-scale voltage-driven tunable infrared filter based on piezoelectric ceramics of the present invention has a large-area tunable filtering range of centimeter size. The present invention uses independently fabricated stationary and moving mirrors, which are supported and bonded together by piezoelectric ceramics. It does not require the use of traditional MEMS sacrificial layer technology, and is therefore not limited by problems such as sacrificial layer release area, residual stress and structural collapse. Experiments show that the effective light transmission area of ​​the filter of the present invention can reach the centimeter level (e.g., 1cm×1cm or more), which can completely cover the photosensitive surface of infrared focal plane detector chips or infrared camera lenses, realizing true "lens-level" large-size dynamic filtering. In contrast, the effective filtering area of ​​existing suspended microbridge structures based on surface micromachining is usually limited to the millimeter level, which is difficult to meet the requirements of aerospace remote sensing, high-sensitivity infrared imaging and other applications for large-area uniform filtering.

[0017] (2) The centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics of the present invention has high-speed tuning characteristics. The present invention uses piezoelectric ceramics as the driving element, and utilizes its inverse piezoelectric effect to generate fast and precise displacement under voltage driving, thereby changing the length of the FP resonant cavity. The response frequency of piezoelectric ceramics can reach the kilohertz (kHz) level, and the cavity length adjustment time can be shortened to the millisecond (ms) or even sub-millisecond level. In contrast, the tuning speed of traditional tuned filters based on mechanical force or thermal drive is usually on the order of seconds, which cannot meet the needs of fast spectral scanning or dynamic target recognition. The present invention can achieve high-speed filter switching on the order of milliseconds, providing real-time, high-frame-rate dynamic filtering capabilities for infrared spectral imaging systems, and significantly improving target recognition and environmental adaptability. Attached Figure Description

[0018] Figure 1 This is a three-dimensional structural schematic diagram of the centimeter-scale voltage-driven tuned infrared filter based on piezoelectric ceramics according to the present invention.

[0019] Figure 2 This is a side view of the centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramics according to the present invention.

[0020] Figure 3 This is a top view of the centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramics according to the present invention.

[0021] Figure 4 Test results of a large-scale, voltage-driven tuned infrared filter based on piezoelectric ceramics, prepared according to Example 1 of the present invention.

[0022] The attached figures are labeled as follows: 1-substrate; 2-antireflective coating; 3-piezoelectric ceramic; 4-stationary mirror; 5-moving mirror. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0024] See Figure 1 and Figure 2This invention provides a centimeter-scale, voltage-driven tunable infrared filter based on piezoelectric ceramics. It employs a piezoelectric ceramic 3 as a support pillar, with a stationary mirror 4 and a moving mirror 5 interconnected and bonded together using the piezoelectric ceramic 3 as the support pillar structure. A uniform cavity gap is formed between the stationary mirror 4 and the moving mirror 5, which constitutes the FP resonant cavity, thereby enabling the filter to achieve dynamic tunability. This invention utilizes the expansion and contraction displacement of the piezoelectric ceramic under voltage to change the interference cavity length, thus achieving the filtering and tuning function.

[0025] Preferably, the height of the FP resonant cavity is 2~5μm, corresponding to the initial center wavelength of the mid-wave infrared filter.

[0026] Preferred, see Figure 3 There are three support columns, which are evenly arranged between the stationary mirror 4 and the moving mirror 5. The stationary mirror 4 and the piezoelectric ceramic 3 are rigidly connected, and the moving mirror 5 and the piezoelectric ceramic 3 are also rigidly connected.

[0027] In this design, the top and bottom walls of the FP resonant cavity are both antireflective coatings 2, and both ends of the support pillars are in contact with the substrate 1. That is, antireflective coatings 2 are grown on the substrate 1 of both the stationary mirror 4 and the moving mirror 5. Before connection, the antireflective coating on one side is etched, retaining the central region (preferably a circular region), while the remaining portion is etched away, thus forming an effective light-transmitting area in the central region; the area of ​​substrate 1 exposed after the remaining portion is etched is named the flat annular zone. The support pillars are in contact with the flat annular zone.

[0028] According to the analytical formula for FP interferometric transmittance: Where R is reflectivity, The phase difference between adjacent transmitted light; the antireflection film in this invention is a multilayer thin film structure composed of multiple high and low refractive index cut-offs to form a high reflectance structure. The higher the reflectance R, the higher the overall filter transmittance T effect, and finally achieve the overall antireflection film effect.

[0029] The effective light-passing area of ​​the centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramics is not less than 1cm×1cm, preferably not less than 2cm×2cm.

[0030] This invention also provides a centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics and its fabrication process, which includes the following steps:

[0031] S1: Prepare moving camera 5 and still camera 4.

[0032] The fabrication steps for the moving mirror 5 and the stationary mirror 4 are as follows: A double-sided polished, 500 μm thick, round sapphire substrate 1 is selected as the base to ensure good transmittance in the mid-infrared band. An antireflection film 2 is grown on one side of the cleaned substrate 1 using electron beam evaporation or magnetron sputtering. The antireflection film 2 can be a multilayer dielectric film structure, such as alternating stacks of ZnS and YbF3, with a center wavelength of 4 μm, so that the transmittance of the stationary mirror 4 and the moving mirror 5 in the 3~5 μm mid-infrared range is greater than 95%, thereby reducing non-interference losses. The antireflection film 2 is etched to form an effective light-transmitting area and a flat ring band.

[0033] S2: Apply adhesive to the corresponding position of the flat ring of the stationary mirror 4, and vertically attach the piezoelectric ceramic 3 to the surface of the substrate 1 of the stationary mirror 4. Specifically, use the piezoelectric ceramic 3 as the column support structure, and clean the surface of the piezoelectric ceramic 3 as follows: Figure 2 As shown, low-release, high-strength UV-curable adhesive or epoxy resin is applied to three symmetrical positions (e.g., equilateral triangle arrangement) on the flat ring of the stationary mirror 4. Three piezoelectric ceramics 3 are then vertically bonded to the surface of the stationary mirror 4, ensuring that the three pieces are at the same height. Preferably, each piezoelectric ceramic 3 is formed by multiple ceramic stacks, i.e., the piezoelectric ceramic 3 is preferably a piezoelectric stacked ceramic.

[0034] S3: After the adhesive has cured, apply adhesive again to the upper surface of the piezoelectric ceramic 3. Align the flat ring of the moving mirror 5 with the upper surface of the piezoelectric ceramic 3 to connect the moving mirror 5 and the piezoelectric ceramic 3 into a single structure, thus obtaining a centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramics. The specific operation is as follows: After curing, apply the same adhesive evenly again to the upper surface of the piezoelectric ceramic 3; use a reverse bonding machine to align the flat ring of the moving mirror 5 with the upper surface of the piezoelectric ceramic 3; adjust the horizontal position and tilt angle under a microscope to ensure the parallelism between the moving mirror 5 and the stationary mirror 4; apply appropriate bonding pressure and use a thermosetting process to completely cure the adhesive, thereby rigidly connecting the moving mirror 5 and the piezoelectric ceramic 3 into a single structure.

[0035] After bonding, a uniform cavity gap is formed between the stationary mirror 4 and the moving mirror 5. This cavity gap is the resonant cavity of the FP filter, i.e., the FP resonant cavity. The initial height of this cavity gap is determined by the height of the piezoelectric ceramic 3 and the thickness of the adhesive layer, and is usually set between 2 and 5 μm, corresponding to the initial center wavelength of the mid-wave infrared filter.

[0036] Example 1:

[0037] This embodiment provides a large-area tunable infrared filter with a circular aperture and a diameter of 2 cm. It uses three piezoelectric ceramics as support and driving columns to achieve high-speed, wide-range filtering and tuning.

[0038] S1: Prepare moving camera 5 and still camera 4.

[0039] (1) Selection of substrate 1: A round sapphire wafer with double-sided polishing and a thickness of 500 μm was selected as substrate 1 for the stationary mirror 4 and the moving mirror 5, respectively. Sapphire has good light transmittance in the mid-wave infrared (3~5 μm) range and excellent thermal stability.

[0040] (2) Antireflection film deposition: An antireflection film 2 is grown on the surface of substrate 1 using electron beam evaporation. In this embodiment, the antireflection film 2 has a three-layer structure: a bottom layer of YbF3, a middle layer of ZnS, and a top layer of YbF3, with a center wavelength designed to be 4 μm. The double-sided transmittance of the sample with the antireflection film 2 is greater than 96% to reduce non-interference loss.

[0041] (3) Etching: Definition of circular light-transmitting area: On the antireflection film 2 on one side of the substrate 1, a circular area with a diameter of 2 cm is protected by photoresist, and the antireflection film in the remaining area is etched away; in this way, the circular area in the middle forms an effective light-transmitting area (circular light-transmitting area), and the substrate 1 exposed after etching is a flat ring.

[0042] S2: Apply adhesive to the corresponding positions on the flat ring of the stationary mirror 4 (at this time, the antireflective film at the adhesive application position is etched away), and vertically attach the piezoelectric ceramic 3 to the surface of the substrate 1 of the stationary mirror 4. Specifically, select three piezoelectric ceramics 3 and apply low-release, high-strength epoxy resin adhesive to three corresponding positions on the surface of the flat ring of the stationary mirror 4. Vertically attach the three piezoelectric ceramics 3 to the surface of the stationary mirror 4, and use a high-precision alignment fixture to ensure that the upper surfaces of the three cylinders are on the same horizontal plane.

[0043] S3: After the adhesive has cured, apply adhesive again to the upper surface of the piezoelectric ceramic 3, and align the flat ring of the moving mirror 5 with the upper surface of the piezoelectric ceramic 3 to connect the moving mirror 5 and the piezoelectric ceramic 3 into a single structure. Specifically, uniformly apply the same epoxy resin adhesive to the upper surface of the piezoelectric ceramic 3 for subsequent bonding and stress buffering. Using a reverse bonding machine, flip the substrate 1 of the moving mirror 5 so that the flat ring of the moving mirror 5 contacts and aligns with the upper surface of the piezoelectric ceramic 3.

[0044] S4: Electrode Lead-out and Packaging. The upper and lower electrodes of the three piezoelectric ceramics 3 are led out to the pins of the ceramic tube shell by gold wire ball bonding. The stationary mirror 4 and the moving mirror 5 are also led to ground and control voltage terminals respectively.

[0045] Device performance testing: Spectral response testing was performed on the packaged device. A control voltage (e.g., 0-160V) was applied to the piezoelectric ceramic 3, and the change in the center wavelength of its transmission spectrum was measured. The test results are as follows: Figure 4 As shown. Figure 4Experimental results show that the centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramics prepared in this embodiment has an effective light-passing area diameter of 2 cm, a tuning range covering the 3~5 μm mid-wave infrared range, and a cavity length adjustment rate under piezoelectric ceramic drive that can reach the millisecond level.

[0046] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A large-size, voltage-driven tuned infrared filter based on piezoelectric ceramics, characterized in that, This centimeter-scale large-size voltage-driven tuned infrared filter uses piezoelectric ceramics as support pillars, which are placed between the stationary and moving mirrors to form an FP resonant cavity.

2. The centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics according to claim 1, characterized in that, The height of the FP resonant cavity is 2~5μm.

3. The centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics according to claim 1, characterized in that, There are three support columns, which are evenly distributed between the stationary mirror and the moving mirror.

4. The centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics according to claim 1, characterized in that, The top and bottom walls of the FP resonant cavity are both antireflective coatings; Both ends of the support column are in contact with the base.

5. The centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics according to claim 1, characterized in that, The effective light-transmitting area of ​​the centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramics is not less than 1cm × 1cm.

6. The fabrication process of the centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1: Prepare moving and still shots; S2: Apply adhesive to the corresponding position on the stationary mirror and vertically attach the piezoelectric ceramic to the surface of the stationary mirror; S3: After the adhesive has cured, apply adhesive again to the upper surface of the piezoelectric ceramic, align the moving mirror with the upper surface of the piezoelectric ceramic to connect the moving mirror and the piezoelectric ceramic into a single structure, and obtain a centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramic.

7. The fabrication process of the centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics according to claim 6, characterized in that, The adhesive used in steps S2 and S3 is a UV-curable adhesive or an epoxy resin adhesive. In step S3, a reverse bonding machine is used to complete the connection between the moving mirror and the piezoelectric ceramic.

8. The fabrication process of the centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics according to claim 6, characterized in that, Step S1 specifically includes the following steps: Sapphire is selected as the substrate material. An antireflection film is grown on the surface of the cleaned sapphire substrate using electron beam evaporation or magnetron sputtering. The antireflection film is then etched to form an effective light-transmitting area and a smooth ring.

9. The fabrication process of the centimeter-scale large-size voltage-driven tuned infrared filter based on piezoelectric ceramics according to claim 8, characterized in that, In step S2, the corresponding position of the stationary mirror coated with adhesive is the surface of the flat ring formed by the etching process of the stationary mirror, and in step S3, the corresponding position of the moving mirror in contact with the piezoelectric ceramic is the flat ring formed by the etching process of the moving mirror.

10. The application of the centimeter-sized voltage-driven tuned infrared filter based on piezoelectric ceramics as described in any one of claims 1 to 5 in the fields of aerospace remote sensing and high-sensitivity infrared imaging.

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