Light guide element and light source device using the light guide element

A light source device, comprising:

• a light guide element comprising a main body having a light-emitting surface, a bottom surface, and a side surface, wherein the side surface is located between the bottom surface and the light-emitting surface, and the bottom surface is opposite to the light-emitting surface, and the main body has a cone-shaped hollow portion used to receive exterior light, and the cone-shaped hollow portion comprises:
• a bottom portion located at the bottom surface, and having a first hollow cross-sectional area;
• and
• a top portion opposite to the bottom portion, and having a second hollow cross-sectional area, wherein the second hollow cross-sectional area is smaller than the first hollow cross-sectional area;
• and
• a light source disposed adjacent to the bottom portion of the light guide element to emit light into the main body of the light guide element through the cone-shaped hollow portion.