[论文解读] Holographic Volumetric Additive Manufacturing

Maria Isabel Álvarez-Castaño, Andreas Gejl Madsen+4 more|arXiv (Cornell University)|Jan 24, 2024

Advanced Optical Imaging Technologies被引用 7

一句话总结

本文展示了用于体积增材制造的全息相位调制，实现至少10倍的投影效率提升、衍射极限分辨率，以及使用基于 DMD 的全息系统、Lee 编码与镶拼以降低散斑，迅速制造毫米级三维对象。

ABSTRACT

3D printing has revolutionized the manufacturing of volumetric components and structures in many areas. Different technologies have been developed including light-induced techniques based on the photopolymerization of liquid resins. In particular, a recently introduced method, so-called Tomographic Volumetric AM (VAM), allows the fabrication of mesoscale objects within tens of seconds without the need for support structures. This method works by projecting thousands of amplitude patterns, computed via a reverse tomography algorithm, into a resin from different angles to produce the desired three-dimensional shape when the resin reaches the polymerization threshold. To date, only amplitude modulation of the patterns has been reported. Here, we show that holographic phase modulation unlocks new capabilities for VAM printing. Specifically, the effective light projection efficiency is improved by at least a factor of 10 over amplitude coding; the resolution can reach the light diffraction limit; and phase encoding allows to control ballistic photons in scattering media, which potentially increases the volume of 3D objects that can be printed in opaque and non-absorbing resins. The approach uses CGH to convert phase, encoded on a 2D modulator to the desired intensity projections by light propagation in a photosensitive resin container. We demonstrate the potential of holographic phase coding using simulations and experiments, the latter by implementing a volumetric printer using a DMD, as the 2D phase modulator in a Fourier configuration. Specifically, we use Lee holograms to encode phase onto a binary DMD. Combining tiled holograms with PSF shaping mitigates the speckle noise typically associated with computer-generated holograms and speed-up their computation. We use these holographic projections to fabricate millimetric 3D objects in less than a minute with a resolution down to 164 um.

研究动机与目标

• 促使使用全息相位编码来提升体积增材制造。
• 证明相位调制能够实现比仅振幅方法更高的光效和更细的分辨率。
• 展示使用空间光调制器和全息编码技术的实际实现。
• 评估在图像质量改进的前提下，在不到一分钟内打印毫米级三维对象的能力。

提出的方法

• 使用计算机生成全息（CGH）将叠加在二维调制器上的相位编码转换为在感光树脂中的期望强度投影。
• 采用 Lee 全息图将相位编码到在傅里叶配置中的二值 DMD 上。
• 将镶嵌全息图与点扩散函数（PSF）整形相结合，以减小散斑噪声并加速计算。
• 从多个角投影数千个全息投影，以通过层析式体积增材制造原理创建目标三维形状。
• 展示包括基于 DMD 的体积打印机在内的仿真和实验，分辨率低至 164 μm，且在不到一分钟内打印毫米级对象。

实验结果

研究问题

• RQ1 全息相位调制是否能在体积增材制造中提升光投影效率，相对于仅振幅的方法？
• RQ2 在散射或不透明树脂中，使用相位编码的全息 VAM 能达到何种分辨率与打印速度？
• RQ3 镶嵌全息图与 PSF 整形如何影响散斑噪声和全息 VAM 的计算吞吐量？
• RQ4 使用傅里叶配置的 DMD 与 Lee 编码实现一个实用的全息 VAM 打印机是否可行？

主要发现

• 相位调制将有效光投影效率至少提高一个数量级以上，与振幅编码相比。
• 在所示系统中，分辨率可以达到光的衍射极限。
• 相位编码有望在散射介质中控制弹道光子，扩展可打印体积。
• 在傅里叶配置下，使用 Lee 全息图的基于 DMD 的全息 VAM 打印机可以在不到一分钟内制造毫米级三维对象。
• 镶嵌全息图结合 PSF 整形可减轻散斑噪声并加速全息图计算。