A light guide pipe includes a first light guide section formed at a first end of the light guide pipe, wherein the first light guide section is straightly extended along a longitudinal axis of the light guide pipe a second light guide section formed at a second end of the light guide pipe, wherein an outer surface of the second light guide section is a convex curved surface, and an outer diameter of the second light guide section is gradually increased along a direction from the second to the first ends, a cavity is formed at a bottom of the second light guide section and a third light guide section formed between the first and second light guide sections, wherein an outer surface of the third light guide section is a concave curved surface, and an outer diameter of the third light guide section is gradually decreased along the direction.導光柱包含一第一導光段,形成於該導光柱的第一端,其中該第一導光段是沿該導光柱的軸向筆直延伸;一第二導光段,形成於該導光柱的第二端,其中該第二導光段的外表面是一外凸曲面,且該第二導光段的外徑是沿該導光柱的第二端往第一端的方向漸增,該第二導光段的底部形成有一凹陷區域;以及一第三導光段,形成於該第一導光段及該第二導光段之間,其中該第三導光段的外表面是一內凹曲面,且該第三導光段的外徑是沿該導光柱的第二端往第一端的方向漸減。110‧‧‧導光柱111‧‧‧第一導光段112‧‧‧第二導光段113‧‧‧第三導光段114‧‧‧第四導光段115‧‧‧凹陷區域116‧‧‧外凸聚光曲面
