Mask-Shifting-Based Projection Lithography for Microlens Array Fabrication

Abstract

Microlens arrays play a critical role in enhancing imaging systems due to their outstanding optical performance, compact size, and lightweight nature. However, traditional fabrication methods for microlens arrays suffer from low precision, inefficiency, high costs, and a lack of adequate surface figure control. In this paper, we present a novel approach for microlens array fabrication, using a projection lithography process with mask-shifting. The method employs a 0.2× projection objective lens to enhance linewidth resolution. By employing a projection-based mask-shift filtering technique, we achieve superior surface figure accuracy while reducing the complexity of mask preparation. The experimental results for four microlenses with different aperture sizes demonstrate surface figure accuracy in the submicron range and surface roughness at the nanometer level. In addition, 3D profilometer scanning equipment was employed to measure the surface roughness of these microlens arrays, and the measurement results of these microlens arrays processed using the proposed method for their surface roughness are 18.4 nm, 29.6 nm, 34.4 nm, and 56.1 nm. Our findings indicate that this method holds great potential in microlens array fabrication, offering the ability to achieve lower linewidths and higher surface figure accuracy compared to conventional methods.

Thin and Large Depth-Of-Field Compound-Eye Imaging for Close-Up Photography

“…Compound-eye imaging systems typically consist of multiple microlenses for imaging and a single photodetector for sensing [3,4]. Several methods have been employed to manufacture high-quality microlens arrays (MLAs), including laserinduced self-writing [5][6][7], two-photon polymerization [8], and projection lithography [9]. In addition, polymer swelling [10,11] and thermal reflow [12] have been used to fabricate MLAs with tunable surface profiles.…”

Mask-Moving-Lithography-Based High-Precision Surface Fabrication Method for Microlens Arrays

“…As the mainstream technology for fabrication of advanced-node micro/nanostructures, mask-based projection lithography technology offers advantages such as a large exposure area, high precision, and efficiency, making it suitable for high-precision fabrication of microlens arrays [27,28]. On this basis, we propose a moving-mask lithography method based on projection, which adopts a 0.2 times projection objective to improve the resolution of line width and reduce the difficulty of mask processing [29]. However, due to the continuous reduction in the size of the unit lens, it is difficult to control the surface shape error and surface roughness, resulting in the degradation of the optical performance of the microlens array composed of the unit lens.…”