Shu Yang, Zhou Wenchen, Zhou Zhixiong, Yi Allen Y
Appl Opt. 2021 Jan 10;60(2):351-357. doi: 10.1364/AO.412763.
Fresnel lens arrays are widely employed in concentrator photovoltaics, photonic devices, and integral imaging systems. In this study, a rapid non-isothermal imprinting process for Fresnel lens arrays was proposed. In this process, a heated mold with microstructures was momentarily pressed onto a thermoplastic polymer surface that was initially kept at room temperature. The microstructures of the mold can be copied completely to the polymer substrate by imprinting consecutively until a continuous surface Fresnel lens array is obtained. Different from more traditional molding processes, the substrate does not need to be heated and cooled repeatedly in the replicating process. In addition, the imprinting process is carried out at room temperature, which can greatly reduce the thermal cycle time and energy consumption. Generally speaking, the material flow and stress distribution of the substrate need to be monitored so that the microlenses with a high precision surface finish can be produced in the non-isothermal imprinting process. To verify this, the finite element method (FEM) model for the non-isothermal process was established, and the feasibility of this process was analyzed. A hexagonal continuous surface Fresnel lens array was then fabricated, and its geometrical contour and imaging performance were tested. The experimental results showed this new process could be an effective and low-cost optical fabrication technology for high-quality production of Fresnel lens arrays.
菲涅耳透镜阵列广泛应用于聚光光伏、光子器件和积分成像系统中。在本研究中，提出了一种用于菲涅耳透镜阵列的快速非等温压印工艺。在该工艺中，将具有微结构的加热模具瞬间压在初始保持在室温的热塑性聚合物表面上。通过连续压印，模具的微结构可以完全复制到聚合物基板上，直到获得连续表面的菲涅耳透镜阵列。与更传统的成型工艺不同，在复制过程中基板不需要反复加热和冷却。此外，压印过程在室温下进行，这可以大大减少热循环时间和能耗。一般来说，需要监测基板的材料流动和应力分布，以便在非等温压印过程中生产出具有高精度表面光洁度的微透镜。为了验证这一点，建立了非等温过程的有限元方法（FEM）模型，并分析了该工艺的可行性。然后制造了六边形连续表面菲涅耳透镜阵列，并测试了其几何轮廓和成像性能。实验结果表明，这种新工艺可能是一种有效且低成本的光学制造技术，可用于高质量生产菲涅耳透镜阵列。
