Wang Tianyi, Huang Lei, Vescovi Matthew, Kuhne Dennis, Zhu Yi, Negi Vipender S, Zhang Zili, Wang Chunjin, Ke Xiaolong, Choi Heejoo, Pullen Weslin C, Kim Daewook, Kemao Qian, Nakhoda Kashmira, Bouet Nathalie, Idir Mourad
Opt Express. 2021 Nov 8;29(23):38737-38757. doi: 10.1364/OE.443346.
Computer-Controlled Optical Surfacing (CCOS) has been greatly developed and widely used for precision optical fabrication in the past three decades. It relies on robust dwell time solutions to determine how long the polishing tools must dwell at certain points over the surfaces to achieve the expected forms. However, as dwell time calculations are modeled as ill-posed deconvolution, it is always non-trivial to reach a reliable solution that 1) is non-negative, since CCOS systems are not capable of adding materials, 2) minimizes the residual in the clear aperture 3) minimizes the total dwell time to guarantee the stability and efficiency of CCOS processes, 4) can be flexibly adapted to different tool paths, 5) the parameter tuning of the algorithm is simple, and 6) the computational cost is reasonable. In this study, we propose a novel Universal Dwell time Optimization (UDO) model that universally satisfies these criteria. First, the matrix-based discretization of the convolutional polishing model is employed so that dwell time can be flexibly calculated for arbitrary dwell points. Second, UDO simplifies the inverse deconvolution as a forward scalar optimization for the first time, which drastically increases the solution stability and the computational efficiency. Finally, the dwell time solution is improved by a robust iterative refinement and a total dwell time reduction scheme. The superiority and general applicability of the proposed algorithm are verified on the simulations of different CCOS processes. A real application of UDO in improving a synchrotron X-ray mirror using Ion Beam Figuring (IBF) is then demonstrated. The simulation indicates that the estimated residual in the 92.3 mm × 15.7 mm CA can be reduced from 6.32 nm Root Mean Square (RMS) to 0.20 nm RMS in 3.37 min. After one IBF process, the measured residual in the CA converges to 0.19 nm RMS, which coincides with the simulation.
在过去三十年中，计算机控制光学表面成形（CCOS）技术得到了极大的发展，并广泛应用于精密光学制造领域。它依靠强大的驻留时间解决方案来确定抛光工具在表面特定点上必须驻留多长时间，以实现预期的形状。然而，由于驻留时间计算被建模为不适定反卷积，要获得一个可靠的解决方案并非易事，该解决方案需满足以下条件：1）非负，因为CCOS系统无法添加材料；2）最小化通光孔径中的残余量；3）最小化总驻留时间以保证CCOS工艺的稳定性和效率；4）能够灵活适应不同的刀具路径；5）算法的参数调整简单；6）计算成本合理。在本研究中，我们提出了一种新颖的通用驻留时间优化（UDO）模型，该模型普遍满足这些标准。首先，采用基于矩阵的卷积抛光模型离散化方法，以便能为任意驻留点灵活计算驻留时间。其次，UDO首次将反卷积简化为前向标量优化，这极大地提高了解的稳定性和计算效率。最后，通过稳健的迭代细化和总驻留时间减少方案来改进驻留时间解。在不同CCOS工艺的模拟中验证了所提算法的优越性和普遍适用性。随后展示了UDO在使用离子束修形（IBF）改进同步辐射X射线镜方面的实际应用。模拟表明，在92.3毫米×15.7毫米的通光孔径中，估计残余量可在3.37分钟内从6.32纳米均方根（RMS）降至0.20纳米RMS。经过一次IBF工艺后，通光孔径中测量到的残余量收敛至0.19纳米RMS，与模拟结果相符。
