Led lens and light source device using the same

An LED lens, applied for an LED assembly including an LED and the LED lens disposed on an emitting surface of the LED;

• the LED lens comprising a light incident surface, a light emitting surface, and a bottom surface extending from the light incident surface and connected to the light emitting surface;
• wherein the light emitting surface is an aspheric surface being symmetrical to an optical axis of the LED assembly, and includes a recession portion disposed at the center of the light emitting surface and a convex portion connected to the outer periphery of the recession portion;
• wherein the light incident surface is a concave surface being symmetrical to the optical axis, and includes a first optically active area and a second optically active area;
• the first optically active area being disposed at the center of the light incident surface, the second optically active area being connected with the first optically active area and the bottom surface;
• wherein an optical path inversion point is disposed at the junction between the first optically active area and the second optically active area;
• wherein θ0 is an included angle between the optical axis and a connecting line from the optical path inversion point to the center of the emitting surface of the LED;
• the LED lens satisfying the following condition:
• 0.71≧cos θ0≧0.51
• when θ<θ0, a distance from the center of the emitting surface of the LED to the light incident surface decreases as the angle θ increases;
• as θ≦θ0, the distance from the center of the emitting surface of the LED to the light incident surface increases or maintains a certain value as the angle θ increases;
• wherein θ is an included angle between the optical axis and a connecting line from the center of the emitting surface of the LED to the arbitrary point on the light incident surface.