Dodging sheet with deflection angle and preparation method and preparation mode thereof

Abstract

The invention discloses a dodging sheet with a deflection angle and a preparation method of the dodging sheet, and belongs to the technical field of optical microstructure manufacturing. The dodging sheet comprises a transparent base material and a deflection free-form surface microstructure array which is arranged on the transparent base material in an out-of-order mode, the related length of a microstructure is 30-60 micrometers, the height is 5-20 micrometers, and the deflection angle is 0-45 degrees and can be continuously adjusted. According to the preparation method, an integrated process of SLM phase shaping, laser-induced modification and selective chemical etching is adopted, composite phase design is carried out through a spatial light modulator, an inclined free-form surface modification domain is formed in a base material in combination with femtosecond / picosecond laser, and then a target microstructure is obtained through chemical etching. According to the invention, the high optical performance of improved dodging uniformity and high transmittance is realized, and meanwhile, the method has the advantages of simplified process, flexible design and low cost, and is suitable for a high-end optical system.

Description

Technical Field

[0001] This invention relates to the field of optical functional materials technology, specifically to a light-diffusing sheet with deflection function and its preparation method. Background Technology

[0002] As a key component in optical systems, beam homogenizers are mainly used to achieve uniform beam distribution and have wide applications in display technology, lighting systems, and optical inspection. Traditional beam homogenizers mainly achieve conventional or large-angle beam homogenization effects, but with the increasing complexity of optical system designs, the functional requirements for beam homogenizers are also becoming more demanding.

[0003] In modern optical systems, not only is uniform light distribution required, but the light beam also needs to have a specific deflection angle to meet special optical path design requirements. For example, in head-mounted displays, laser projection systems, and optical sensing devices, the light beam needs to be uniformly distributed while being deflected in a specific direction.

[0004] Currently, the mainstream technologies for achieving deflection include wet etching, dry etching, and laser direct writing, but these technologies all have obvious limitations: Due to the isotropic etching properties of chemical solutions, microstructures fabricated using wet etching techniques are typically symmetrical, making it difficult to achieve directional deflection. Even with specialized mask designs, it is challenging to precisely control the deflection angle, and deflection efficiency and uniformity cannot be simultaneously achieved.

[0005] While dry etching technology can achieve high etching precision, the anisotropy of plasma etching is limited, and fabricating asymmetric microstructures with deflection capabilities remains a significant challenge. Furthermore, process parameter control is complex, repeatability is poor, and costs are high.

[0006] Laser direct writing technology can create asymmetric structures through grayscale exposure, but it can only be done on photoresist and cannot be directly etched on glass. It also requires subsequent processes such as transferring to a hard mold for nanoimprinting, which results in high processing costs and complex processes.

[0007] Laser-induced depth etching (LIDE / SLE) technology, which has been developed in recent years, is mainly used for glass through-hole (TGV) processing. Although it can achieve high aspect ratio structures, it lacks the ability to process randomly arranged free-form surface microstructures. This technology is difficult to achieve precise control of complex surface morphology and cannot meet the special requirements of deflection homogenizers for microstructure morphology. Summary of the Invention

[0008] The purpose of this invention is to provide a light homogenizer with a deflection angle and its preparation method, so as to solve the problems mentioned in the background art.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a light-diffusing sheet with a deflection angle, comprising a transparent substrate and a randomly arranged array of deflected free-form microstructures disposed on the substrate, wherein the microstructure array has a relative length of 30-60μm, a height of 5-20μm, and a deflection angle that is continuously adjustable from 0-45°.

[0010] Preferably, the transparent substrate is quartz glass or borosilicate glass with a thickness of 1-3 mm and an optical transmittance of over 90%.

[0011] Preferably, the freeform surface microstructure array has a light uniformity of over 90% and an optical transmittance of over 90%.

[0012] Preferably, the microstructure array adopts a randomized, non-periodic arrangement to avoid diffraction effects and moiré patterns.

[0013] A method for preparing a light homogenizer with a deflection angle includes the following steps: A composite phase distribution, including a basic homogenization phase and a deflection angle modulation phase, is designed using SLM phase shaping technology. Wavefront shaping of a laser beam is performed using a spatial light modulator and a 4f optical path system; Femtosecond or picosecond lasers are used to induce the formation of tilted freeform surface modification domains inside a transparent substrate; The target microstructure is formed by selectively removing the laser-modified areas through chemical etching.

[0014] Preferably, the laser parameters are: pulse width 100fs-10ps, repetition frequency 100kHz-2MHz, wavelength selected from 1030nm, 515nm or 800nm, and spot diameter 2-5μm.

[0015] Preferably, the chemical etching uses a fluorine-containing etching solution or a BOE system, with an etching rate of 0.02-0.30 μm / min, an etching time of 10-90 min, and a temperature control of 20-50℃.

[0016] Preferably, it also includes post-processing steps, including neutralization, cleaning, drying, and light etch-back or plasma passivation treatment.

[0017] Compared with the prior art, the beneficial effects of the present invention are: This invention achieves integrated light homogenization and deflection functions through an innovative randomized arrangement of freeform surface microstructures. Optical transmittance is increased to over 90%, light homogenization uniformity exceeds 90%, and the deflection angle is continuously adjustable from 0-45°. This integrated design overcomes the limitations of traditional technologies and significantly simplifies the optical system architecture.

[0018] Employing an integrated process chain of SLM phase shaping → laser-induced modification → chemical etching, the traditional 7-10 steps are simplified to a 3-step core process. This digital manufacturing method significantly improves design flexibility, allowing for rapid responses to different customized needs simply by modifying the phase distribution, without requiring hardware replacement.

[0019] Compared to traditional dry etching, production costs are reduced, primarily due to savings in mask manufacturing costs, reduced equipment investment, and lower energy consumption. Production cycles are shortened, yield rates are improved, and equipment utilization is increased.

[0020] This technology is applicable to various transparent materials such as quartz glass and borosilicate glass, and can meet the needs of high-end applications such as AR / VR displays, laser projection, and optical sensing. Digital phase design and closed-loop feedback control ensure precise control of process parameters. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the design of the disordered deflection free-form surface microstructure in this invention; Figure 2 This is a schematic diagram of the SLM combined with 4f laser pulse shaping optical path; Figure 3 This is a process flow diagram of the shaping laser-induced chemical etching process of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0023] This invention provides a technical solution: a light homogenizer with a deflection angle, comprising a transparent substrate and a randomly arranged array of freeform microstructures disposed on the substrate. The microstructure array has a relative length of 30-60 μm, a height of 5-20 μm, and a continuously adjustable deflection angle of 0-45°. The transparent substrate is quartz glass or borosilicate glass with a thickness of 1-3 mm and an optical transmittance exceeding 90%. The light homogenization uniformity of the freeform microstructure array exceeds 90%, and the optical transmittance exceeds 90%. The microstructure array adopts a random, non-periodic arrangement to avoid diffraction effects and moiré patterns.

[0024] The light homogenizer mainly consists of a transparent substrate and an array of randomly arranged, deflected free-form surface microstructures disposed on its surface. The substrate is made of optical-grade quartz glass or borosilicate glass, possessing excellent thermal stability and mechanical strength, with a thickness controlled between 1 and 3 millimeters to ensure structural stability while maintaining optical performance. The substrate's optical transmittance must reach over 90% to ensure efficient light transmission and reduce energy loss. Furthermore, the substrate surface should be free of obvious scratches, bubbles, impurities, and other defects to ensure image quality and optical uniformity. The microstructure array employs a freeform surface design, arranged non-periodicly and randomly on the substrate surface. Through multiple deflections and scattering of incident light, it achieves a uniform distribution of the outgoing light field. This structure effectively suppresses diffraction effects and light spot interference, making it suitable for high-quality uniform light requirements in fields such as laser lighting, projection displays, and precision optical sensing.

[0025] Microstructure array features: It adopts a randomized non-periodic arrangement to effectively avoid diffraction effects and moiré patterns; each microstructure is an inclined free-form surface with a correlation length of 30-60μm and a height of 5-20μm; the deflection angle is continuously adjustable from 0-45° to meet the needs of different application scenarios; the overall uniformity of light is >90% and the optical transmittance is >90%.

[0026] A method for preparing a light homogenizer with a deflection angle includes the following steps: A composite phase distribution is designed using SLM (spatial light modulator) phase shaping technology. This distribution simultaneously includes a basic homogenizing phase for achieving light intensity uniformity and a deflection modulation phase for controlling the processing angle. By using a spatial light modulator combined with a 4f optical path system to perform high-precision phase modulation on the wavefront of the incident laser beam, the shape and position of the laser focus can be controlled. Using femtosecond or picosecond lasers, modified regions with free-form surface morphology with tilt angles are induced by precise focusing inside a transparent substrate; The laser-modified areas are then selectively removed using a chemical etching process, ultimately forming the desired microstructure inside or on the surface of the substrate.

[0027] The laser processing parameters are as follows: pulse width 100 fs–10 ps, ​​repetition frequency 100 kHz–2 MHz, wavelength can be selected as 1030 nm, 515 nm or 800 nm, and the focused spot diameter is controlled between 2–5 μm.

[0028] The chemical etching process uses a fluorinated etching solution or a BOE (buffered oxide etchant) system, with an etching rate between 0.02 and 0.30 μm / min, an etching time of 10 to 90 minutes, and a temperature controlled within the range of 20 to 50°C.

[0029] The process also includes post-processing steps, which mainly include neutralizing residual etchant, rinsing with deionized water, nitrogen blowing or drying, and light back etching or plasma passivation as needed to improve surface properties.

[0030] The fabrication process of this invention mainly includes: Phase design and wavefront shaping are core aspects of optical engineering, involving the precise control of the light wave phase to achieve applications such as beam shaping, deflection, or homogenization. Composite phase design is performed using a SLM (spatial light modulator). Specifically, this involves mathematically superimposing a basic uniform phase distribution (used to generate a uniform light intensity distribution) with a deflection angle modulated phase distribution (used to achieve directional deflection of the beam) to generate a comprehensive phase pattern. To optimize this composite phase distribution and improve its efficiency and accuracy, the Gerchberg-Saxton algorithm (a phase retrieval method based on iterative Fourier transform) or freeform surface fitting methods (directly optimizing the wavefront by calculating the ideal shape of the optical surface) are often used. These methods facilitate high-precision phase modulation on the SLM and are applicable to fields such as laser processing, holographic displays, and adaptive optics systems.

[0031] Laser-induced modification is an advanced materials processing method. Its core lies in utilizing femtosecond or picosecond ultrafast lasers and spatially shaping the laser beam through a 4f optical path system to achieve highly localized and precisely controlled modification regions within transparent or translucent substrates. The key to this technology is the precise adjustment of laser parameters: pulse widths typically range from 100 femtoseconds to 10 picoseconds, repetition frequencies cover a range from 100 kHz to 2 MHz, and commonly used wavelengths include 1030 nm, 515 nm, and 800 nm. Through precise control of energy density, focusing position, and scanning path, functional structures such as refractive index changes, phase transformations, or microstructure generation can be achieved within materials, leading to its widespread applications in optical storage, microfluidic device fabrication, and integrated optics.

[0032] Chemical etching is a widely used process in microfabrication. It employs selective chemical etching technology to precisely form the desired microstructure by preferentially removing laser-modified areas. The etching solution typically uses fluorine-containing systems or BOE (Buffered Oxide Etchant), which effectively etch specific materials, ensuring selectivity and efficiency. By precisely controlling etching parameters such as temperature, concentration, time, and stirring speed, highly precise control over the etched morphology can be achieved, meeting the demands of high-precision microstructure manufacturing. This process not only improves processing efficiency but also ensures the consistency and reliability of the microstructure.

[0033] Example 1: Microstructure parameter design and optical performance verification Microstructure design principles The random arrangement deflection freeform surface microstructure design in this invention deeply integrates wave optics and geometric optics theories. Through high-precision phase calculation and optimization, it achieves precise modulation of the wavefront phase of light, thereby efficiently controlling the propagation direction, energy distribution and wavefront shape of the light field, and improving the performance and application range of optical devices.

[0034] Phase superposition is a core concept in wavefront modulation technology, used to design complex wavefront distributions. The composite phase distribution is formed by the linear superposition of the basic homogenizing phase φ_homogen and the deflection modulation phase φ_tilt, and its mathematical expression is: φ_total = φ_homogen + φ_tilt.

[0035] The basic uniform phase is obtained through optimization using the GS algorithm (Gerchberg-Saxton algorithm). This algorithm optimizes the phase distribution through iterative Fourier transform and inverse transform to ensure that the output light field achieves a uniform intensity distribution on the target plane. The deflection modulation phase is designed according to the target deflection angle θ required by the system, and the specific formula is as follows: φ_tilt = (2π / λ) · sinθ · x, Here, λ represents the operating wavelength, and x is a spatial coordinate variable, typically corresponding to the lateral position along the beam propagation direction. This superposition method not only simplifies the phase design process but also allows for independent control of the beam's uniformity and deflection direction, making it widely applicable in fields such as optical manipulation, laser processing, and holographic displays.

[0036] Randomized array design aims to avoid diffraction effects caused by periodic structures, which often lead to unnecessary interference and performance degradation in optical systems. To address this, a Poisson disk sampling algorithm is employed. This algorithm generates a random but uniformly distributed array of points, ensuring that the minimum distance between points always meets preset optical performance requirements, thereby effectively improving the reliability and efficiency of the design. This method is particularly suitable for optical devices requiring high resolution and diffraction-free applications, such as display technologies and imaging systems.

[0037] Parameter optimization experiment Experimental materials: The substrate is made of high borosilicate glass (2.0 mm thick, with a visible light transmittance of more than 91%). This material has excellent thermal stability, chemical resistance and high mechanical strength, and is suitable for precision micromachining and optical applications.

[0038] The laser processing system uses a femtosecond laser source with a center wavelength of 515 nm and a pulse width of 300 fs. It has high peak power and high precision processing capabilities and is suitable for the modification of transparent materials.

[0039] The etching solution is prepared by mixing hydrofluoric acid (HF), ammonium fluoride (NH4F) and deionized water (H2O) in a volume ratio of 1:2:4. This formula can achieve controllable chemical etching of the laser-modified area to form a microstructure with a certain aspect ratio and smooth sidewalls.

[0040] In terms of parameter combination design, this study systematically designed nine different combinations of processing parameters to systematically investigate the effects of two key morphological parameters—related lengths (30 μm, 45 μm, 60 μm) and structural heights (5 μm, 12.5 μm, 20 μm)—on the final microstructure optical properties (such as diffraction efficiency, transmittance, and scattering behavior). Each parameter combination underwent repeated experiments to ensure the reliability of the results.

[0041] Test method: Morphology characterization: Atomic force microscopy (AFM) was used for high-resolution surface morphology analysis, which can detect nanoscale topological structures; at the same time, white light interferometer was used for non-contact surface profile measurement, providing macroscopic morphology information.

[0042] Optical performance: The total transmittance of the sample is tested by integrating sphere to evaluate the light transmission efficiency in the material; the uniformity of light distribution is tested by imaging luminance meter to ensure the consistency of light output of optical components.

[0043] Deflection characteristics: An angle-resolved scattering system is used to measure the angular distribution of scattered light, thereby analyzing the deflection behavior and scattering characteristics of materials or surfaces.

[0044] Experimental Results and Analysis Optimal parameter combination: In the optimized design of optical components, the light homogenizer exhibits optimal overall performance when the relevant length is set to 45 μm and the height to 12.5 μm. Specific performance indicators include: a light homogenization uniformity of 92.3%, ensuring highly consistent light distribution; an optical transmittance of 91.8%, achieving excellent light transmission efficiency; a deflection angle control accuracy of ±0.5°, guaranteeing precise light path guidance; and a deflection efficiency of 89.5%, demonstrating high energy utilization. These data fully demonstrate the excellent balance of uniformity, transmittance, control accuracy, and efficiency achieved by the light homogenizer under these parameters.

[0045] Parameter Influence Patterns: When the correlation length is too small (less than 30 μm), the diffraction effect becomes significant because the structure size is close to the wavelength of light, causing unnecessary scattering and interference of light, thereby reducing the uniformity of the homogenizing system and affecting the consistency of the illumination distribution.

[0046] When the correlation length is too large (greater than 60 μm), the periodic or random characteristics of the microstructure become more prominent, the visibility of the structure is enhanced, and obvious patterns or textures may be generated in the human eye or sensor, which in turn has a negative impact on visual experience or imaging quality.

[0047] When the height is too small (less than 5μm), the structure's ability to modulate the phase of light waves is insufficient, and it cannot effectively control the deflection angle and direction of the light, resulting in a weakening or insignificant deflection effect, which affects the performance of the optical components.

[0048] When the height is too large (greater than 20μm), the material absorbs and reflects light more, resulting in a significant decrease in transmittance. At the same time, the manufacturing process involves deeper etching or molding, which increases the difficulty of the process and may introduce defects or reduce the yield.

[0049] Example 2: Preparation process optimization and mass production feasibility verification Detailed Process Flow S1: Target Design and Phase Generation A phase design process based on an iterative optimization algorithm is adopted. This algorithm iteratively optimizes the phase distribution through multiple iterations to ensure the target optical performance is achieved. The process includes the following steps: First, the microstructure geometric parameters are determined according to the target optical performance (such as spot shape and uniformity), as these parameters directly affect the phase modulation effect. Second, the Gerchberg-Saxton algorithm is used to calculate the basic homogenized phase. This algorithm is an efficient iterative phase retrieval method that can infer phase information from the intensity distribution. Next, the deflection modulation phase is superimposed to further optimize the phase distribution, achieve directional deflection and energy homogenization of the beam, and reduce aberrations through algorithmic adjustments. Finally, the optimized phase information is loaded onto the laser wavefront through a 4f optical path system. The 4f system is based on Fourier optics principles to ensure accurate phase transmission and wavefront modulation, thus completing the entire design process.

[0050] S2: Laser-induced modification process Laser parameter precision control system: Energy density control: The working range is 0.5-2.0J / cm², which can be finely adjusted according to the reflectivity, absorption characteristics and thermal conductivity of different substrates to ensure that each type of material can achieve the best modification effect, while avoiding processing defects caused by overheating or insufficient energy. Scanning strategy: A high-precision variable-spacing scanning path is adopted, with the overlap rate strictly controlled between 30% and 70%. The scanning spacing and speed are adjusted in real time through an adaptive algorithm to distribute energy evenly and reduce the heat-affected zone, thereby improving the uniformity and repeatability of the processing area. Focusing control: An integrated dynamic focusing system compensates for focal length deviations on different processing planes in real time, ensuring that the laser beam maintains a stable spot size and power density throughout the modification area, thereby achieving consistent modification results; Environmental control: The entire process is carried out in a Class 1000 clean environment, equipped with a high-precision temperature control device. The ambient temperature fluctuation is controlled within ±1℃, which effectively reduces the impact of external particulate contamination and thermal fluctuations on processing quality and ensures process stability and repeatability.

[0051] S3: Chemical Etching Process Optimization of etching process parameters: For the etching solution formulation, an HF:NH4F:H2O ratio of 1:2:4 was used. This ratio helps maintain a good balance between surface uniformity and etching rate during the etching process. The temperature was controlled at 35±2℃, which effectively promotes the reaction while avoiding over-etching. The etching time was controlled at 45 minutes to ensure that the target etching depth was achieved and the clarity of the pattern outline was maintained. Magnetic stirring was used, with the speed maintained at a stable 200 rpm to ensure uniform distribution of the etching solution components, reduce local concentration differences, and improve the consistency and repeatability of the etching process.

[0052] S4: Post-processing technology Post-processing steps include: Neutralization treatment: Use 5% NaOH solution to neutralize the residual acid to ensure complete removal of acidic substances and prevent corrosion problems in subsequent processes; Cleaning process: Ultrasonic cleaning is performed using three stages of ultrapure water. Each stage of cleaning gradually removes impurities and ion residues to ensure surface cleanliness. Drying process: First, remove most of the moisture using a centrifugal dryer, then blow dry with high-purity nitrogen to avoid oxidation and moisture residue; Surface passivation: The surface is modified by plasma treatment technology, which effectively reduces surface defects and enhances the stability and durability of materials.

[0053] Mass production feasibility analysis Production equipment configuration: Laser processing station: femtosecond laser + SLM + 4f optical path + precision platform; Etching production line: multi-tank etching system + automatic transfer device; Testing equipment: Online optical inspection + morphology characterization system; Production efficiency assessment: Single-station processing cycle: 15 min / piece; Daily production capacity: 96 pieces / station; Yield: >95%; Cost analysis: Compared to traditional dry etching, the cost is reduced by approximately 60%, mainly due to: Cost savings in mask manufacturing; The simplification of process steps leads to a reduction in equipment investment; Energy consumption is reduced by approximately 40%; Material consumption was reduced by approximately 35%.

[0054] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative and not exhaustive. All modifications within the scope of this invention or its equivalents are included in this invention.

Claims

1. A light uniformizing sheet with a deflection angle, characterized by: The application relates to a transparent substrate and a disordered deflection free-form microstructure array arranged on the substrate, the microstructure array has a correlation length of 30-60 mu m, a height of 5-20 mu m and a continuously adjustable deflection angle of 0-45 degrees.

2. The light uniformity sheet with a deflection angle according to claim 1, characterized in that: The transparent substrate is quartz glass or borosilicate glass, and the thickness is 1-3 mm, and the optical transmittance is more than 90%.

3. The light uniformity sheet with deflection angle according to claim 1, characterized in that: The homogenization uniformity of the free-form microstructure array is more than 90%, and the optical transmittance is more than 90%.

4. The light uniformity sheet with deflection angle according to claim 1, characterized in that: The microstructure array adopts a disordered non-periodic arrangement mode, and diffraction effect and moire are avoided.

5. A method of manufacturing a light uniformizing sheet with a deflection angle, characterized by: The application also discloses a preparation method of the microstructure array. The application discloses a preparation method of the microstructure array. The application discloses a preparation method of the microstructure array. The application discloses a preparation method of the microstructure array. The laser parameters are as follows: pulse width 100 fs-10 ps, repetition frequency 100 kHz-2 MHz, wavelength selected from 1030 nm, 515 nm or 800 nm, and spot diameter 2-5 mu m.

6. The method of claim 5, wherein the deflection angle is 0.5 to 5 degrees. The chemical etching adopts a fluorine-containing etching liquid or a BOE system, the etching rate is 0.02-0.30 mu m / min, the etching time is 10-90 min, and the temperature is controlled to be 20-50 DEG C.

7. The method of claim 5, wherein the deflection angle is 0.5 to 5 degrees. The application further discloses a post-processing step, including neutralization, cleaning, drying and light etching or plasma passivation treatment.

8. The method of claim 5, wherein the deflection angle is 0.5 to 5 degrees. ​

Images