本論文為指紋辨識之光學成像系統設計。研究流程為：（1）幾何光學理論初階計算；（2）以Zemax光學軟體來進行優化，找尋系統最佳參數；（3）於光機模擬商用軟體建構系統模型，模擬指紋特徵光源間距大小為0.1mm，觀察聚焦成像於感測器上之能量分佈；（4）進行公差分析，以找出公差上下限。 在直角稜鏡式指紋辨識系統中，以直角稜鏡提供指紋按觸，會使得影像在斜面的維度會壓縮除以1.414因子，且在有限共軛成像的條件下，如何縮短成像距離且兼顧成像品質是個難題。傳統式模擬出來的結果，在22.63mm範圍的最外兩側之影像對比度低於0.2以下，不符合系統之影像對比度0.4以上要求，而改良式提升效果均在0.5以上。 提出新型稜鏡式架構以改善直角稜鏡式架構其影像會有壓縮之缺點，採用離軸光路設計，增加一全反射光學面，以減少雜散光，並提升系統的訊雜比。新型式1在16mm範圍內之離軸負4mm外，低於影像對比度0.6之要求，而新型式2整體均在0.65上。 在實際生產製造上，設計者必須訂出合理的公差範圍，能讓製程人員有所依循。藉由Zemax光學軟體的公差靈敏度分析，來求得公差範圍，可以知道哪個參數對於系統影像對比度較具有高靈敏度。 In this paper, we research on optical imaging system of fingerprint identification. We follow these design process: (1) We use geometrical optics theories to calculate first-order structure. (2) We use Zemax optical software to optimization. (3) It builds point source that simulate fingerprint feature into ASAP to trace ray. Then, it estimate the energy distribution on sensor. (4) We analysis the simulation model’s tolerance. It provides a reference data for manufacturer. On Right-angle prism type fingerprint identification, it restricts to right-angle prism. It causes object distances fixed. The short imaging distance lets tilted axis angle could be bigger. Then, distortion aberration also could be influence seriously. Traditional type’s fingerprint range is 22.63mm . We discuss fingerprint size is 0.1mm. It’s two outside image contrast lower 0.2. It can not satisfy image quality specification. However, Innovation type’s image contrast raise higher to 0.5. We provide new prism type fingerprint identification. It designs off-axis optical system. In order to prevent image compressed, it adds a reflective optical surface. It’s advantages is reducing stray light and improving S/N ratio of system performance. New type 1’s fingerprint range is 16mm. Outside negative 4mm, the image contrast lower 0.6. But, New type 2’s image contrast raise higher to 0.65.
