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, an outer diameter of the second light guide section is gradually increased along a direction from the second to the first ends, and 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.
