鏡頭光機公差分析之研究

Abstract

傳統光學系統的公差分析對於實際的製程能力考慮不盡周全，而且由機械誤差產生的組裝變異也未考慮；如欲達到“爲製造設計(Design for Manufacturing)” 的目的，機械工程師有必要提供系統組裝合成公差的資訊，作為光學工程師公差分析的輸入值，讓真實的製程能力反應在光學性能之上，本研究的目的是建構一個鏡頭系統的光機公差分析模型，以計算鏡片在鏡筒內的累積偏心角度公差與偏心距離公差；具曲面特性的球面鏡片與非球面鏡片的光機公差模型與組裝方法在本研究中發展完成，該模型由點幾何構成，以VSA-3D□軟體編輯，並以蒙地卡羅(Monte Carlo)方法模擬，模擬結果以敘述統計呈現；最後以兩個 “投入式(drop-in)” 組立設計的鏡群組為案例，計算鏡片在鏡筒內的累積偏心角度公差、偏心距離公差及鏡片光學軸的累計偏移量，其結果顯示該模型可模擬一個鏡頭系統的關鍵品質參數；所以，鏡頭系統的性能在大量生產之前可藉本光機公差模擬模型預測其品質與良率。

The traditional tolerance analysis of optical systems does not consider the capability of the real manufacturing process, and the variation occurs in the assembly process caused by the tolerances of optical and mechanical components. In order to have a “Design for Manufacturing” optical system, the mechanical engineer has to provide the resultant system assembly variation as an input to the optical design and analysis to anticipate the performance of the optical system. The purpose of this study is to develop an opto-mechanical tolerance model to calculate the element tilt, decenter and despace stack-up within a cell. A surface based opto-mechanical tolerance models of sphere lens, aspheric lens, and assembly algorithm have been developed in this study. The model is represented as point geometry, implemented by VSA-3D□ software, and simulated by Monte Carlo method. The simulation results are conducted by descriptive statistics. Two “drop-in” assembly design lens groups were studied to calculate the stack-up element tilt and decenter within a cell and the resultant deviations of the optical axes away from the mechanical datum axis. The results indicate that the opto-mechanical tolerance model can analyze the critical to quality parameters of a lens system. As a result, the performance of the lens system can be anticipated by the opto-mechanical tolerance model before mass production.