本研究主要是針對自行車LED 車頭燈的反射鏡,探討其投射後之均勻度,並提出一種改善投射均勻度的變焦拋物面。再利用歪斜光線追蹤法對其作光學建模,進而利用最佳化設計理論,獲得最佳化的變焦拋物面參數,而達到投射均勻度之提升。最後利用ZEMAX光學分析軟體與實體模型,加以比較驗證。 以軸對稱曲面的一次反射面為主,提出一種改善投射均勻度的變焦拋物面。由於光線到達成像面目標區時,部分為一次反射後再到達,部分為直接到達,因此在數學建模上有一定的困難度。而本研究乃是以純解析的歪斜光線追蹤法,對此變焦拋物面的集光器進行數學建模。再套用最佳化設計理論,獲得一組最佳化的變焦拋物面參數。
A LED projection system is proposed comprising a LED chip and a variable-focus-parabolic (VFP) reflector in which the focal length varies as a function of the vertical displacement of the incidence point relative to the horizontal centerline of the LED chip. The light ray paths within the projection system are analyzed using a skew-ray tracing approach. A method is then proposed for optimizing the geometry of the projector in such a way as to optimize the uniformity of the illuminance distribution on the target region of image plane, and simultaneously avoid the glare effect. The validity of the proposed optimization method is demonstrated by means of ZEMAX simulation. It is shown that the optimized VFP projector yields a significant improvement the illuminance uniformity and avoids the glare effect compared to conventional spherical and parabolic projectors.