Vibration damping for optical systems via mechanical metamaterials

Abstract

The innovative application of mechanical metamaterials introduced here revolutionizes the field of vibration reduction in optical material processing setups. Metamaterials, synthetic composites crafted with particular structures, possess unique properties not typically seen in natural materials, making them ideal for custom-built applications. Their customization potential extends beyond material selection and includes the engineering of unit cell geometries to amplify desired properties, such as vibration damping. Using manufacturing techniques like CNC machining and 3D printing, these metamaterials are designed for specific vibration-damping applications. They are strategically positioned in the system, including in compact spaces, to target areas most susceptible to or affected by vibrations. The careful design of the metamaterial blocks accommodates for different vibration frequencies, allowing for an adaptable vibration damping solution. This ingenious implementation of metamaterials marks a leap in ensuring steadiness and enhancing performance in optical systems by effectively mitigating noise and disruptions due to vibrations.

Description

[0001] VIBRATION DAMPING FOR OPTICAL SYSTEMS VIA MECHANICAL METAMATERIALS

[0002] FIELD OF THE INVENTION

[0003] The invention relates to a vibration damping for optical system using mechanical metamaterials.

[0004] DESCRIPTION OF THE RELATED ART

[0005] Vibration is an inherent byproduct of the majority of devices that are currently in use across the vast fields of science and industry. Despite being a seemingly unavoidable phenomenon, it poses detrimental effects on the optimal functioning of these devices, impacting their precision and reliability to varying degrees depending on their application.

[0006] Among the range of devices, optical material processing systems, such as 3D printers, laser CNC machines, and related technologies, are particularly vulnerable to the negative effects of vibration. These systems are intricate, and their operations rely heavily on precise and consistent movement. As such, even slight disturbances can significantly hamper their performance.

[0007] Vibrations within these systems are problematic because they can disrupt or distort the optical path within the optical chain. This disruption / distortion can lead to imprecision in the output, as the path of the light determines the quality and accuracy of the result. Moreover, vibrations can cause the sample being processed to shift position rapidly and unpredictably during operation. This erratic movement introduces a level of uncertainty and variability into the process, leading to potentially significant inaccuracies and inconsistencies in the end product.

[0008] Adding to the complexity of the issue, many sub-systems within optical material processing setups have a tendency to generate their own vibrations. These can originate from a variety of sources, including cooling fans or systems, the mechanical movement of translation or scanning elements, and more. This multitude of internal vibration sources compounds the difficulty in managing and mitigating the overall vibration within the system.

[0009] Complicating matters further, these systems are often compact in design and highly sensitive to packaging constraints. This means that they cannot easily accommodate some of the more common vibration-damping techniques that might be applied to larger, less sensitive machinery. As a result, finding effective solutions to control and eliminate vibrations in these systems can be both challenging and critical.

[0010] Thus, addressing the issue of vibration in optical material processing systems is of paramount importance, but it's also a considerable challenge. The task requires a deep understanding of the systems themselves, the sources of vibration, and the potential methods for damping these unwanted side-effects. Despite the complexity, achieving this goal is crucial for improving the precision and reliability of these technologies. The patent document EP4158424A1 (published on 5 April 2023) provides a compact damping arrangement for reducing vibrations in optical systems, specifically in microlithographic projection exposure apparatus. It effectively dampens vibrations, even at higher frequencies. The arrangement includes an element experiencing vibrations, a fluid-filled cavity, and at least one connected channel. When the element vibrates, the fluid partially displaces into the channel, dissipating vibration energy through friction. The arrangement eliminates the need for additional absorber masses, making it compact. It can damp resonant frequencies above 50 Hz, utilizing stable auxiliary masses or the fluid itself. The channel can serve as a cooling channel, and the invention is applicable to mirrors, actuator components, and supporting / measurement frames. The disclosure also mentions its use in EUV or VUV projection exposure apparatus. One major drawback of the vibration damping method involving liquids is its inefficiency, primarily attributed to factors such as complex implementation, high maintenance requirements, limited effectiveness in reducing vibrations, and the difficulty in tuning the system.

[0011] Patent document nr. CN111120572A (published on 8 May 2020), presents an invention for an ultra-low frequency torsional vibration-damping metamaterial. The proposed metamaterial consists of cells with positive and negative stiffness in parallel, creating an ultralow local resonance band gap. The cells include outer and inner ring tile- shaped permanent magnets, a flexible rod, a resonance mass, and a leaf spring group. By utilizing repelling magnetic pole pairs and parallel leaf springs, the metamaterial achieves an ultra-low stiffness state, resulting in a very low natural frequency and effective attenuation of low-frequency ultralow frequency torsional vibration. Due to the potential negative impact of magnets on sensitive electrical equipment, their use for vibration damping is not applicable in optical systems.

[0012] An alternative technology of vibration damping is described in patent document Nr. NL2031134A (published on 02 March 2023) whereby the invention aims to address the lack of effective vibration reduction in existing subway track beds. It introduces a phononic-like crystal concrete metamaterial, consisting of multiple primitive cells with different sizes arranged in a periodic structure. The metamaterial is prepared by coating stones with epoxy resin and mixing them with cement mortar as the matrix. This allows for the creation of a track bed that can open low-frequency band gaps below 100 Hz, thereby enhancing vibration reduction in subways. The phononic-like crystal concrete metamaterial offers improved performance and has practical applications for subway systems. Thus, this vibration damping technology is not optimized for photonics.

[0013] In CN112519330A (published on 19 March 2021), the vibration damping metamaterial damping plate is an innovative solution that addresses the limitations of traditional damping plates. It combines the unique properties of metamaterials, including a negative Poisson's ratio, with a compressed honeycomb core structure, a rigid plate, and a damping layer. The honeycomb core undergoes lateral shrinkage upon impact, causing the rigid plate to move laterally and generate shear deformation with the damping layer. This design not only improves impact resistance and damping performance but also leverages the negative Poisson's ratio of the metamaterials, resulting in enhanced shear damping capabilities. This makes the damping plate particularly suitable for aerospace applications where the damping performance of traditional materials is limited by temperature and frequency effects. The lightweight and adjustable nature of the damping plate further enhances its practicality and effectiveness in vibration control and structural design. The problem is that the negative poisson ratio metamaterials can exhibit non-linear stress-strain relationships and hysteresis, which could make the damping performance less predictable and harder to control.

[0014] A technique of vibration damping by using metamaterials has been discussed and investigated in patent document Nr. CN202110183633A (published on 8 February 2021). The invention proposes an elastic wave metamaterial vibration isolation device that combines the characteristics of phononic crystals and particle dampers. Phononic crystals attenuate elastic waves within specific frequency ranges, while particle dampers dissipate energy through collisions and friction. The device integrates a phononic crystal, scattered particle group, and buffer material into a vibration isolation device. It combines the advantages of phononic crystal vibration isolation and particle dampers, providing enhanced attenuation within the phononic crystal's band gap frequency range. The use of a particle group with different-sized particles improves energy consumption efficiency and reduces noise. The device offers a simple structure, flexibility in size, and affordability, making it suitable for various environments. But there is a drawback. The device incorporates a scattered particle group as a particle damper, which may introduce additional unwanted scattering or interference to optical signals, affecting the performance of the optical system.

[0015] Accordingly, it is desired to provide a vibration damping system for optical devices.

[0016] This description provides a concept of mechanical metamaterials for vibration damping in optical material processing systems. Metamaterials are synthetic composites with structures that exhibit unusual properties, making them customizable for specific applications. Their inherent vibration-damping property is leveraged in this invention to suppress vibrations within an optical system. This is achieved by fitting metamaterial blocks in strategic positions prone to or sensitive to vibrations, including the device legs, holding frame, optical chain base, and internal optical elements. These metamaterials are designed to target specific vibrationdamping regimes and are produced using manufacturing processes such as CNC machining and 3D printing. Multiple lattices within the metamaterial block can be configured to dampen different frequency vibrations. This approach has the potential to greatly improve the stability and performance of optical systems, reducing noise and interference caused by internal or external vibrations, thereby enhancing the accuracy and reliability of optical measurements and processes.

[0017] SUMMARY OF THE INVENTION

[0018] This invention introduces a new class of substances called metamaterials, specifically mechanical metamaterials, used for vibration damping in optical material processing systems. Metamaterials are synthetic composite materials engineered to have properties not found in natural materials. These properties can be pre-designed for specific applications, in this case, for vibration isolation in optical systems. Metamaterial blocks can be positioned strategically throughout the optical system to eliminate or reduce vibrations from sub-systems that are more prone to causing vibrations or sensitive to them.

[0019] These metamaterials are produced with a specific design that targets certain vibrationdamping regimes and can be made from standard materials like polymers or metals using manufacturing processes like CNC machining or 3D printing. The functionality of these mechanical metamaterials stems from unit cells, periodically placed structural elements that together form and amplify the desired property. Multiple unit cell geometries like arrowhead, re-entrant, curved beam bistable, and divergent star-shaped can be used and arranged in 2D, 2.5D or 3D lattices.

[0020] The properties of the mechanical metamaterials, like the lattice configuration, size, and direction, can be tailored for different parts of the system to effectively dampen all the vibrations within the system. Furthermore, the same metamaterial block can be modulated with different lattice parameters to dampen different frequency vibrations. The exact design is guided by the vibrations to be dampened and the most rational configuration according to application, manufacturing, and packaging requirements.

[0021] BRIEF DESRCIPTION OF DRAWINGS

[0022] FIG. 1: Arrowhead unit cells and lattices that could be used for vibration damping mechanical metamaterials.

[0023] FIG. 2: Re-entrant unit cells and lattices that could be used for vibration damping mechanical metamaterials.

[0024] FIG. 3: Curved beam bistable unit cells and lattices that could be used for vibration damping mechanical metamaterials.

[0025] FIG. 4: Divergent star-shaped unit cells and lattices that could be used for vibration damping mechanical metamaterials.

[0026] FIG. 5: Schematics of gradually changing lattice size L to modulate properties of vibration damping mechanical metamaterial properties.

[0027] FIG. 6: Schematics of changing lattice size L block-by-block to modulate properties of vibration damping mechanical metamaterial properties.

[0028] FIG. 7: Schematics of changing lattice type within the structure to modulate properties of vibration damping mechanical metamaterial properties.

[0029] FIG. 8: Mechanical vibration absorbing metamaterials are placed between legs and frame.

[0030] FIG. 9: Mechanical vibration absorbing metamaterials are placed between the frame and optical chain base.

[0031] FIG. 10: Mechanical vibration absorbing metamaterials are placed between the optical chain base and vibrations causing the device.

[0032] FIG. 11: Mechanical vibration absorbing metamaterials are placed between each optical element and optical chain base.

[0033] FIG. 12: Mechanical vibration absorbing metamaterials are placed between frame and optical chain base and optical chain base and vibrations causing internal device. DETAILED DESCRIPTION OF THE INVENTION

[0034] The present invention pertains to the innovative design, fabrication, and application of mechanical metamaterials for vibration damping in optical material processing systems. Mechanical metamaterials, the artificially engineered composite materials, offer unique structural properties which are typically absent in naturally occurring substances. Their inherent property of being able to suppress vibrations makes them particularly suitable for applications in optical material processing systems.

[0035] The use of standard manufacturing materials, notably polymers and metals known for their mechanical properties, is revolutionized through the creation of these metamaterials. The materials are structured in a smart way to achieve the desired structural properties via a carefully planned internal design. This implies a shift from conventional material design, focusing more on the arrangement of the constituent elements rather than the elements themselves.

[0036] The crux of the functionality of these mechanical metamaterials is rooted in the periodic arrangement of micro- structured elements, which are placed periodically to form lattice. These unit cells are specifically engineered to enhance the desired property, with their design significantly influencing the production methodology. Various geometrical configurations such as arrowhead (FIG. 1), re-entrant (FIG. 2), curved beam bistable (FIG. 3), and divergent star-shaped (FIG. 4) are particularly suitable for the purpose of vibration damping, but this is not an exhaustive list. With the aid of advanced computational techniques, other geometrical configurations can be designed and utilized according to specific requirements.

[0037] The arrangement of these unit cells can be in 2D, 2.5D (for instance, a 2D structure mapped on a cylindrical surface), or 3D, which, despite being the most challenging to produce, is often the preferred configuration owing to its superior performance characteristics. These metamaterials can have auxetic properties, but these are not required. The single lattice cell size L, defined as the smallest size in one of the projections, can vary from 10 pm to 20 mm, allowing for a wide range of applications. The overall structure size H, defined as the largest single dimension of the structure, can be anywhere from 50 pm to 10 cm, offering a vast range for practical implementations. The orientation of the lattice a, or the angle between the cartesian coordinate system and the axis of symmetry of the metamaterial lattice, can be freely chosen if the lattice has anisotropic mechanical properties, preferable fixation, manufacturing conditions.

[0038] The production methodologies for these metamaterials can be subtractive, such as Computer Numerical Control (CNC) machining, or additive, such as 3D printing. Both of these techniques offer the precision and flexibility required for creating complex unit cell arrangements.

[0039] The working principle of these mechanical metamaterials lies in their ability to absorb and mitigate vibrations caused by internal devices within the optical chain. These devices can include cooling systems, translation stages, scanners, and other similar components, which can cause disturbances in the overall system performance. Mechanical vibration absorbing metamaterial structures (6) can be strategically placed in various locations within the system to effectively dampen vibrations. For instance, mechanical metamaterials, when fitted between the device's legs (5) and frame (4) (FIG. 8), provide a solid foundation for the system. This placement helps counteract any floor-based vibrations that could disrupt the operation of the system, thereby enhancing stability. Inserted between the frame (4) and the optical chain base (3) (FIG. 9), metamaterials act as a protective buffer, mitigating the transmission of vibrations between these core components and preserving the integrity of the optical chain.

[0040] The positioning of metamaterials between the optical chain base (3) and vibrationcausing devices (2) (FIG. 10) is crucial in isolating and controlling internal system vibrations. These could stem from cooling systems, translation stages, scanners, and similar components within the system. By strategically placing metamaterials between each optical element (1) and the optical chain base (3) (FIG. 11), each optical element (1) is safeguarded from any vibrational disturbances that could affect its functionality or performance.

[0041] Finally, the strategic placement of mechanical vibration absorbing metamaterial structures (6) between the frame (4) and the optical chain base (3), as well as between the optical chain base (3) and vibration-causing internal devices (2) (FIG. 12), offers a holistic approach to vibration control. This not only dampens vibrations from individual components but also intercepts vibrational pathways within the system, ensuring that the overall system operates smoothly and efficiently. This flexibility allows for bespoke vibration control depending on the specific needs of the system and its components. Overall, this versatile application allows for effective vibration suppression without requiring extensive modifications to the existing system architecture.

[0042] Another significant advantage of these mechanical metamaterials is their compatibility with packaging requirements of the system. Despite their excellent vibration damping properties, they maintain a low volume, ensuring that they do not disrupt the system's overall form factor.

[0043] The properties of a mechanical metamaterial are primarily determined by its lattice configuration, size, and orientation. A single type of lattice or metamaterial might not sufficiently dampen all vibrations within the system. Therefore, the use of different metamaterials, based on varying lattices or lattice parameters, can be employed in different parts of the system to achieve a comprehensive vibration damping solution. Within the same metamaterial block, various lattice parameters can be applied to create a modulated metamaterial. This enables the damping of different frequency vibrations within a single metamaterial block, offering a compact yet highly effective solution. The modulation of mechanical metamaterials can be achieved through various methods. One approach involves gradually changing the lattice size L (FIG. 5). In this configuration, the dimensions of the lattice unit cells are progressively adjusted, influencing the properties of the metamaterial over a continuous range. This allows for a smooth transition in vibration-dampening capabilities across the metamaterial block, making it possible to address varying vibration frequencies within a single structure. A second approach to modulation is changing the lattice size L block- by-block (FIG. 6). Here, different blocks of the metamaterial have varying lattice sizes, allowing for discrete zones of specific vibration-dampening properties. This approach is particularly useful when different areas within the system experience distinct vibrational frequencies, allowing for tailored vibration suppression within each block. Lastly, modulation can be achieved by changing the lattice type within the structure (FIG. 7). Different lattice geometries, such as arrowhead, re-entrant, curved beam bistable, or divergent star-shaped, can be employed within the same metamaterial block. This variability not only introduces different mechanical properties to address a broader range of vibration frequencies but also provides flexibility in the manufacturing process depending on the complexity of the chosen lattice types. This method offers a highly versatile vibration-dampening solution that can be customized according to the specific needs of the system.

[0044] The exact design of the unit cell arrangement is dictated by the types of vibrations that need to be dampened, and the most rational configuration is chosen according to the specific application, manufacturing constraints, and packaging requirements.

[0045] In conclusion, the invention as described herein provides a significant advancement in the field of mechanical metamaterials for effective vibration damping in optical material processing systems. Its flexible design and customizability make it a versatile solution for a wide array of applications, offering a robust answer to the challenges faced in the field of optical material processing.

Claims

CLAIMS1. A system of metamaterial-based vibration damping system for optical material processing devices, which characterized in that it comprises: mechanical metamaterials comprise structural elements, unit cells, placed periodically to form lattice; wherein said metamaterial are positioned in areas within the optical material processing device prone to or sensitive to vibrations.

2. The system of claim 1, wherein the mechanical metamaterial unit cell geometry design selected of the group depending on implementation, for example: arrowhead; re-entrant; curved beam bistable; divergent star- shaped.

3. The system of claim 1, wherein the size of the single lattice cell L, ranges from 10 pm to 20 mm, and the overall structure size H can range from 50 pm to 10 cm.

4. The system of claim 1, wherein the metamaterials are made from polymers or metals with known mechanical properties.

5. The system of claim 1, wherein the mechanical metamaterials are manufactured using subtractive processes such as CNC machining, or additive processes such as 3D printing.

6. The system of claim 1, wherein multiple unit cells be arranged in 2D, 2.5D, or 3D manner.

7. The system of claim 1, wherein the orientation of the lattice a, or the angle between the cartesian coordinate system and the axis of symmetry of the metamaterial lattice, can be freely chosen if the lattice has anisotropic mechanical properties, preferable fixation, manufacturing conditions.

8. The system of claim 1, wherein the vibration damping mechanical metamaterial properties can be modulated by ways selected of the group comprising: gradually changing lattice size L; changing lattice size L block-by-block; changing lattice type within the structure.

9. The system of claim 1, wherein the mechanical vibration absorbing metamaterials can be placed anywhere in the optical material processing device between different components or isolating individual optical elements on demand.

10. The system of claim 1, wherein the metamaterials can have auxetic properties.

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