Injection Compression Molded Microlens Arrays for Hyperspectral Imaging

Abstract

In this work, a polymer microlens array (MLA) for a hyperspectral imaging (HSI) system is produced by means of ultraprecision milling (UP-milling) and injection compression molding. Due to the large number of over 12,000 microlenses on less than 2 cm², the fabrication process is challenging and requires full process control. The study evaluates the process chain and optimizes the single process steps to achieve high quality polymer MLAs. Furthermore, design elements like mounting features are included to facilitate the integration into the final HSI system. The mold insert was produced using ultraprecision milling with a diamond cutting tool. The machining time was optimized to avoid temperature drifts and enable high accuracy. Therefore, single immersions of the diamond tool at a defined angle was used to fabricate each microlens. The MLAs were replicated using injection compression molding. For this process, an injection compression molding tool with moveable frame plate was designed and fabricated. The structured mold insert was used to generate the compression movement, resulting in a homogeneous pressure distribution. The characterization of the MLAs showed high form accuracy of the microlenses and the mounting features. The functionality of the molded optical part could be demonstrated in an HIS system by focusing light spectrums onto a CCD image sensor.

Suppression of Surface Waviness Error of Fresnel Micro-Structured Mold by Using Non-Integer Rotation Speed Ratio in Parallel Grinding Process

“…(1) when RSR RN is integer and the wave-shift value Tθ= 0, the circular waviness profile on the edge of the i-th circle surface of Fresnel micro-structured mold is: As for the Fresnel micro-structured mold with several circle surfaces, the circular waviness profiles on the edge of each circle surface can be used to characterize its surface waviness distribution condition. When an RSR is integer, the circular waviness profiles can be mathematically described by Equation (11), whose period and amplitude can be calculated by Equations (12) and (13). When RSR is non-integer and the wave-shift value T θ = 1 q , the circular waviness profiles can be mathematically described by Equation 14, whose period and amplitude can be calculated by Equations (15) and (16).…”

“…Fresnel lenses are widely used in projection display [5], photography [6], lighting optics [7], and solar energy [8]. In order to achieve large-scale and low-cost production, it is currently vigorously developing replication processing technologies such as glass molding [9][10][11][12], whose key component is Fresnel micro-structured mold. The mold material used for glass molding is mainly hard-brittle material such as silicon carbide (SiC) and tungsten carbide (WC) [13][14][15].…”

A Facile and Rapid Approach to Lotus‐Seedpod‐Structured Electronic Skin for Monitoring Diverse Physical Stimuli

“…Despite these advances, methods for fabricating pressure sensors with hierarchical sensing micro‐structures, such as template‐printing, coating, photolithography, and 3D printing, have recently come under scrutiny due to the increasing demand for efficient green manufacturing. [ 11 ] Thus, low‐cost, high‐throughput conventional polymer processing technologies have been investigated for the preparation of sensors with inner multi‐tier structures. Zhai et al.…”

The Interface Thermal Resistance Evolution between Carbide-Bonded Graphene Coating and Polymer in Rapid Molding for Microlens Array

“…Loaldi et al [ 9 ] used injection compression molding (ICM) to produce enhanced optical performances of molded polymer optics in terms of birefringence and transmission of light. Roeder et al [ 10 ] fabricated a large number of over 12,000 microlenses on surfaces less than 2 cm 2 by means of ultraprecision milling (UP-milling) and injection compression molding. In addition, they adopted this approach to produce a complicated curved diffractive optical element (DOE) in their another work [ 11 ].…”