Abstract
The design and manufacture of cost-effective miniaturized optics at wafer level, usingadvanced semiconductor-like techniques, enables the production of reduced form-factor cameramodules for optical devices. However, suppressing the Fresnel reflection of wafer-level microlensesis a major challenge. Moth-eye nanostructures not only satisfy the antireflection requirementof microlens arrays, but also overcome the problem of coating fracture. This novel fabricationprocess, based on a precision wafer-level microlens array mold, is designed to meet the demandfor small form factors, high resolution, and cost effectiveness. In this study, three different kinds ofaluminum material, namely 6061-T6 aluminum alloy, high-purity polycrystalline aluminum, and purenanocrystalline aluminum were used to fabricate microlens array molds with uniform nanostructures.Of these three materials, the pure nanocrystalline aluminum microlens array mold exhibited auniform nanostructure and met the optical requirements. This study lays a solid foundation for theindustrial acceptation of novel and functional multiscale-structure wafer-level microlens arrays andprovides a practical method for the low-cost manufacture of large, high-quality wafer-level molds.
Highlights
Microlens arrays (MLA) are fundamental micro-optical elements composed of a series of lenslets, with diameters ranging from several micrometers to several millimeters, that are arranged in a certain configuration
After the trials with different materials, a 6061-T6 substrate, electroplated with pure aluminum consisting of nanosized grains (US proprietary), was identified to satisfy the requirements of both lens mold quality and uniform nanostructure
We demonstrated the fabrication of a high-quality, multiscale-structure wafer-level MLA mold using ultraprecision machining and self-assembling aluminum oxidation (AAO) processes, which produced hundreds of accurate aspherical microlens cavities and a uniform layer of AR nanostructures on the mold surface
Summary
Microlens arrays (MLA) are fundamental micro-optical elements composed of a series of lenslets, with diameters ranging from several micrometers to several millimeters, that are arranged in a certain configuration. They are used in diverse applications, such as micro-optical collimation, diffusion lighting, three-dimensional (3D) imaging, light homogenization, and wavefront sensing [1,2,3,4,5,6]. Fresnel surface reflection loss is still an issue in wafer-level MLA applications. Dielectric coatings are currently used in wafer-level MLAs; 4−8”
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