Enhanced Schlieren System for In Situ Observation of Dynamic Light–Resin Interactions in Projection-Based Stereolithography Process
Enhanced Schlieren System for In Situ Observation of Dynamic Light–Resin Interactions in Projection-Based Stereolithography Process
复制标题
用于在基于投影的立体光刻工艺中对动态光与树脂相互作用进行原位观察的增强型纹影系统
DOI：
10.1115/1.4062218
复制
发表时间：
2023
期刊：
影响因子：
--
通讯作者：
Zhou, Chi
中科院分区：
文献类型：
--
作者：
Chivate, Aditya;Zhou, Chi
数字无掩模光刻由于其独特的能力，快速制造高分辨率的零件，而不使用物理掩模，越来越受欢迎。通过实施受控的灰度和曝光控制，它有可能完全取代传统的光刻。然而，尽管存在光聚合的理论基础，原位观察体素生长过程是一个重大的挑战。这种困难可以归因于几个因素，包括部件的微观尺寸，固化和未固化树脂之间的低折射率差异，以及一旦超过一定阈值，光聚合的快速速率。因此，迫切需要一个能够解决这些问题的系统。为了解决这些挑战，本文提出了一种改进的基于纹影的观察系统，该系统利用共焦放大光学器件在相机的焦平面上创建一个虚拟屏幕。该系统允许通过使用纹影光学器件使折射率的微小变化可视化，特别是通过改变密度诱导的折射率梯度使光偏转。聚焦光学器件的使用为系统提供了定位虚拟屏幕和实现光学放大所需的灵活性。研究人员使用具有不同像素数的单次拍摄二进制图像来制造体素，并检查影响体素形状的各种因素，包括化学成分和能量输入。然后将观察到的结果与基于Beer-Lambert定律、光聚合曲线和高斯光束传播理论的模拟结果进行比较。物理实验结果验证了该观测系统的有效性。本文还简要讨论了该系统在微透镜制造中的应用及其相对于基于理论模型的轮廓预测的优势。
Digital maskless lithography is gaining popularity due to its unique ability to quickly fabricate high-resolution parts without the use of physical masks. By implementing controlled grayscaling and exposure control, it has the potential to replace conventional lithography altogether. However, despite the existence of a theoretical foundation for photopolymerization, observing the voxel growth process in situ is a significant challenge. This difficulty can be attributed to several factors, including the microscopic size of the parts, the low refractive index difference between cured and uncured resin, and the rapid rate of photopolymerization once it crosses a certain threshold. As such, there is a pressing need for a system that can address these issues. To tackle these challenges, the paper proposes a modified Schlieren-based observation system that utilizes confocal magnifying optics to create a virtual screen at the camera's focal plane. This system allows for the visualization of the minute changes in refractive indices made visible by the use of Schlieren optics, specifically the deflection of light by the changing density-induced refractive index gradient. The use of focusing optics provides the system with the flexibility needed to position the virtual screen and implement optical magnification. The researchers employed single-shot binary images with different pixel numbers to fabricate voxels and examine the various factors affecting voxel shape, including chemical composition and energy input. The observed results were then compared against simulations based on Beer–Lambert's law, photopolymerization curve, and Gaussian beam propagation theory. The physical experimental results validated the effectiveness of the proposed observation system. The paper also briefly discusses the application of this system in fabricating microlenses and its advantages over theoretical model-based profile predictions.