Forest Craig R, Saez Miguel A, Hunter Ian W
Department of Mechanical Engineering, BioInstrumentation Laboratory, MIT, Cambridge, MA 02139, USA.
Appl Opt. 2007 Dec 20;46(36):8668-73. doi: 10.1364/ao.46.008668.
Interest in micro-optical components for applications ranging from telecommunications to life sciences has driven the need for accessible, low-cost fabrication techniques. Many microlens fabrication processes are unsuitable for applications requiring 100% fill factor, apertures approximately 1000 microm with high numerical aperture, and scalability to large areas (e.g., tens of centimeters to meters) with millions of lenses. We report on a flexible, low-cost mold fabrication technique that utilizes a combination of milling and microforging. The technique involves first performing a rough cut with a ball-end mill. Final shape and sag height are then achieved by pressing a sphere of equal diameter into the milled divot. Using this process, we have fabricated molds for rectangular arrays of 1-10,000 lenses with apertures of 25-1600 microm, sag heights of 3-130 microm, interlens spacings of 250-2000 microm, and fill factors up to 100%. Mold profiles have a roughness and figure error of 68 nm and 354 nm, respectively, for 100% fill factor, 1000 microm aperture lenses. The required forging force was modeled as a modified open-die forging process and experimentally verified to increase nearly linearly with surface area. The optical performance of lens arrays injection molded from microforged molds was characterized by imaging the point spread function and was found to be in the range of theoretical values. The process can be easily adapted to lenticular arrays as well. Limitations include milling machine range and accuracy.
从电信到生命科学等各种应用对微光学元件的兴趣推动了对可及、低成本制造技术的需求。许多微透镜制造工艺不适用于需要100%填充因子、孔径约1000微米且具有高数值孔径以及可扩展到包含数百万个透镜的大面积（例如数十厘米到数米）的应用。我们报告了一种灵活、低成本的模具制造技术，该技术结合了铣削和微锻造。该技术首先使用球头铣刀进行粗加工。然后通过将等直径的球体压入铣削的凹坑中来实现最终形状和垂度高度。使用此工艺，我们制造了用于1 - 10,000个透镜的矩形阵列的模具，其孔径为25 - 1600微米，垂度高度为3 - 130微米，透镜间距为250 - 2000微米，填充因子高达100%。对于100%填充因子、1000微米孔径的透镜，模具轮廓的粗糙度和形状误差分别为68纳米和354纳米。所需的锻造力被建模为改进的开式模锻工艺，并通过实验验证其随表面积几乎呈线性增加。由微锻造模具注塑成型的透镜阵列的光学性能通过对点扩散函数成像进行表征，发现其在理论值范围内。该工艺也可轻松适用于柱面透镜阵列。局限性包括铣床的加工范围和精度。
