Microjet, or inkjet, technology is used to fabricate lenslet arrays with packing densities greater than 15000/cm/sup 2/. Typical lens diameters range between 70 and 150 /spl mu/m, and focal lengths are between 50 and 150 /spl mu/m. Individual lenslets are characterized in the Fraunhofer plane. The full array is characterized in its far field. >

Microjet fabrication of microlens arrays

Polymeric microlens arrays, with a diameter of 36–96 μm, a radius of curvature of 20–60 μm and a pitch of 250 μm, were fabricated using micro-compression molding with electroformed mold inserts. We used the reflow method and the electroforming process to make the mother and the metallic mold inserts, respectively. Micro-compression molding with powder polymer was developed to replicate microlenses. The surface profiles, imaging qualities, and surface roughness of the microlenses were measured and analyzed.

https://iopscience.iop.org/article/10.1088/0960-1317/13/1/314/pdf

Fabrication of a microlens array using micro-compression molding with an electroformed mold insert

We report a novel process technology of hemispherical shaped microlenses, using isotropic wet etching of silicon in an acid solution to produce the microlenses molds Governed by process parameters such as temperature and etchant concentration, the isotropic wet etching is controlled to minimize various defects that appear during the molding creation From the molds, microlenses are fabricated in polymer by conventional replication techniques such as hot embossing and UV-molding The characterization of molds and measurements of replicated microlenses demonstrate high smoothness of the surfaces, excellent repeatability of mold fabrication and good optical properties Using the proposed method, a wide range of lens geometries and lens arrays can be achieved

Fabrication of spherical microlenses by a combination of isotropic wet etching of silicon and molding techniques.

Microlens arrays are the key component in the next generation of 3D imaging system, for it exhibits some good optical properties such as extremely large field of view angles, low aberration and distortion, high temporal resolution and infinite depth of field. Although many fabrication methods or processes are proposed for manufacturing such precision component, however, those methods still need to be improved. In this review, those fabrication methods are categorized into direct and indirect method and compared in detail. Two main challenges in manufacturing microlens array are identified: how to obtain a microlens array with good uniformity in a large area and how to produce the microlens array on a curved surface? In order to effectively achieve control of the geometry of a microlens, indirect methods involving the use of 3D molds and replication technologies are suggested. Further development of ultraprecision machining technology is needed to reduce the surface fluctuation by considering the dynamics of machine tool in tool path planning. Finally, the challenges and opportunities of manufacturing microlens array in industry and academic research are discussed and several principle conclusions are drawn.

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Fabrication of Microlens Array and Its Application: A Review

Polymeric microlenses play an important role in reducing the size, weight, and cost of optical data storage and optical communication systems. We fabricate polymeric microlenses using the microcompression molding process.The design and fabrication procedures for mold insertion is simplified using silicon instead of metal. PMMA powder is used as the molding material. Governed by process parameters such as temperature and pressure histories, the micromolding process is controlled to minimize various defects that develop during the molding process. The radius of curvature and magnification ratio of fabricated microlens are measured as 150 μm and over 3.0, respectively.

Fabrication of polymeric microlens of hemispherical shape using micromolding

A new laser-based method was developed for fabrication of microlenses on flat quartz plates. In this method, a CO(2) laser is used to heat a quartz surface and induce thermal reactions for source gases of SiH(4) and NO. Even as-grown silicon oxide deposits have the spherical thickness distribution required for a lens at the center and this useful area can be further increased by wet etching. Microlenses were checked on a Fizeau interferometer for surface accuracy and aberrations. As a demonstration, a 14-microm thick microlens was used for collimating light from an optical fiber.

Miyuki Kubo

Papers

Fabrication of microlenses by laser chemical vapor deposition