Design and Fabrication of Micro-Lens Arrays by Two-Photon Polymerization

本文研究以雙光子聚合製作之光場相機微透鏡陣列之設計及製程。光場相機之微透鏡陣列由大量排成陣列的微透鏡組成，陣列中每個微透鏡直徑為100微米，焦距500微米。在大範圍加工中，每個微透鏡的加工時間都頗重要。因此，需要對透鏡的設計和製程進行簡化；選用菲涅耳透鏡是因為其具有比球面透鏡較簡單的加工路徑，所以製程能夠加快。檢查及比較不同壓電平台之間的實際位移反應，同樣也檢查了不同移動速度反應。PI P-611壓電平台表現較PI P-615好，一個較輕的試片載台對所加工的形狀影響較少。雙光子聚合製造系統選用低成本的130kHz高頻率Nd:YAG雷射，高分子材料ORMOCOMP以及放大倍率為100倍、數值孔徑為1.3的物鏡。使用1.2%光起始劑之新配方ORMOCOMP被採用來改善體素大小，讓本實驗室的加工速度比以往經驗更快。透過製造不同體素、不同製造參數的直線來研究此配方之ORMOCOMP的性質。由高解析度掃描式電子顯微鏡所量測得之影像，可取得直線之側向及縱向解析度。由線製造結果所取得的雙光子聚合製程特性，可與PSF Lab軟體的模擬結果比較。根據線製造實驗經驗和結果所提供的資訊，成功製造出數個微型產品。用新配方之ORMOCOMP所製成的菲涅耳微透鏡陣列，具有將光線聚焦及物體成像的功能。四階菲涅耳透鏡、球面透鏡、微齒輪也由此材料製成並具有好的品質。This thesis studies the design and fabrication of micro-lens arrays for light-field cameras by two-photon polymerization (TPP). A micro-lens array for light-field cameras consist of large number of lenses arranged in array, each micro-lens in the array having diameter of 100 micrometers, and focal length of 500 micrometers. For fabrication over large area, time for fabricating each lens would be important. Therefore, simplifying the design and fabrication for a lens is carried out; Fresnel lens is chosen because it has a fabrication path more simple than spherical lens, and hence faster fabrication. The displacement responses of different piezo stages are checked and compared, as well as those with different speed. The piezo stage PI P-611 preforms better than PI P-615, a lightened adaptor has less effects to the shape fabricated. The TPP fabrication system uses a 130kHz high repetition rate and low-cost Nd:YAG laser. ORMOCOMP and objective lenses with 100x and numerical aperture (NA) of 1.3 are used in TPP production. A new preparation of ORMOCOMP with 1.2% photoinitiator is used to improve voxel size from previous work of our lab so that the fabrication time can be faster. The properties of this preparation of ORMOCOMP are studied by fabricating a series of lines with various voxel distance and fabrication parameters. By the use of high resolution scanning electronic microscope (SEM), the width and height of lines can be obtained. The characterization of TPP fabricating process from line fabrication is compared with simulation result by PSF Lab software. Based on the experience and results from the experiment of line fabrication, several micro products are fabricated successfully. Fresnel micro-lens arrays fabricated with ORMOCOMP are able to focus light and produce object image. Binary and four-level Fresnel zone plate (FZP), spherical micro-lens array and micro-gear are also fabricated with good quality by this preparation of ORMOCOMP