精密微玻璃光學元件之開發及製作

機構典藏 > College of Engineering > Graduate Institute & Department of Mechanical and Electro-Mechanical Engineering > Thesis > Item 987654321/105751

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Title:	精密微玻璃光學元件之開發及製作
Other Titles:	Research on fabrication processes for precision micro glass optical components
Authors:	張家榮;Chang, Chia-Jung
Contributors:	淡江大學機械與機電工程學系博士班趙崇禮;Chao, Choung-Lii
Keywords:	超精密磨削;超精密銑削;微陣列透鏡;Ultra-precision grinding;Ultra-precision milling;Micro-lens array
Date:	2015
Issue Date:	2016-01-22 15:04:20 (UTC+8)
Abstract:	為因應人們對影像品質及相關光學系統持續翻新的”苛刻”要求，對小尺寸且形狀/結構複雜之光學鏡片/鏡頭模組的需求也隨之快速成長；其中，微米~次毫米尺度，具有優越表面粗糙度與高形狀精度之微非球面透鏡及自由曲面透鏡更是需求日益殷切的光學元件。通常為了能獲得較佳的光學性能表現，光學透鏡/鏡頭模組必須具有高且穩定之折射率、高穿透率、優越的耐蝕性及耐刮削、衝擊性與優良的環境耐久性等高品質光學元件之基本需求。相較於塑膠鏡片，光學玻璃鏡片雖然成本較高且較不易生產，但卻比塑膠材料更能滿足上述之各項需求。本研究致力於研發可行且有效率生產次毫米尺寸非球面玻璃透鏡/陣列式玻璃透鏡之製程，本研究致力於研發可行且有效率生產次毫米尺寸非球面玻璃透鏡/陣列式玻璃透鏡之製程，研究中除研製UV光固化樹脂鑽石砂輪(直徑0.4mm、磨粒粒徑2~4μm / 30~40μm) 並搭配開發線上磨耗監控系統運用於超精密磨削加工以成功產出表面粗糙度優於8nm(Ra)且形狀精度優於0.2μm之碳化鎢模具，並以此模具模造成形出表面粗糙度優於10nm且形狀精度優於0.5μm而直徑為0.5mm之玻璃非球面透鏡。由於小尺寸砂輪因磨耗導致的加工形狀誤差，通常需經由多次的誤差補償計算及反覆加工，才可滿足嚴謹的形狀精度需求。因此，若使用磨削加工方式加工陣列式透鏡模具必定需要極其冗長的加工時間，難於被業界所接受，本研究開發出另一種模具製作方式，即為單點鑽石微銑削加工電漿離子滲氮處理過之不銹鋼材料，可大幅縮短製作模具之時間，首先將鋼材STAVAX與SKD61做粗創加工後進行離子滲氮表面處理，再使用精密鑽石微銑削加工得到最終形狀，本研究中以加工製作一4*4非球面微陣列模具為驗證，每顆透鏡直徑為1.5mm，最大矢高量(Sag)為24.4μm，微銑削加工所模具之每顆透鏡表面粗糙度均優於10nm且形狀精度優於1μm；而利用此不銹鋼模具進行熱壓成形之玻璃透鏡，透鏡表面粗糙度可控制於10nm以下且形狀精度在3μm以下，各項結果證實本研究開發之製程可精確且有效率的製作出次毫米尺寸非球面玻璃透鏡與陣列式非球面透鏡。 Owing to the fast growing demands for smaller and more complex optical systems, micrometer to sub-millimeter lenses and free-formed optics with superb surface finish and high profile accuracy are attracting more and more attention. To pursue better performance, higher and more stable refraction index, higher transmissivity, better chemical/mechanical resistance and better environmental durability are normally the basic requirements of a high quality optical lens/lens module. In comparison to plastic lenses, glass lenses, though relatively more expensive and difficult to produce, have the advantages of better meeting most of the above mentioned requirements. This research aims to develop an effective process to fabricate sub-millimeter glass lenses and glass lens arrays. UV-cured resin bond diamond grinding wheels of 2~4 µm /30~40 µm in grit size and 0.4 mm in diameter together with in-process optical wear monitoring system were developed and adopted in the precision slant grinding process to successfully generate tungsten carbide (WC) molds of surface finish and profile accuracy better than 8 nm (Ra) and 0.2 µm (P-V) respectively. Glass lenses of 0.5 mm in diameter were subsequently molded by the machined WC molds to a surface finish and profile accuracy better than 10 nm (Ra) and 0.5 µm (P-V) respectively. Due to the small dimension of grinding wheel, it generally takes many grinding cycles to compensate the form error induced by wheel wear and to meet the stringent profile accuracy requirements. This means that the machining time for a micro lens array will be too long to be industrially viable. An alternative mold producing process namely plasma nitrided stainless steels in conjunction with single point diamond mcro-milling technique was developed to shorten the mold fabrication time. STAVAX and SKD61 were rough machined and plasma-nitrided before the final profile was generated by precision diamond micro-milling process. A 4X4 aspheric micro-lens array with lens size of 1.5mm and maximum sag of 24.4 μm was successfully produced with all aspheric lenses machined to a surface finish and profile accuracy better than 10 nm (Ra) and 1 µm (P-V) respectively. The molded glass aspheric micro-lens array generated using this mold has a surface finish (Ra)/profile accuracy (P-V) better than 10 nm/3 µm. The results obtained in this study demonstrate that sub-millimeter glass aspheric lenses and glass aspheric lens arrays can be accurately and effectively produced by the developed processes.
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