the lens 20 the spherical surface 266 refracts the light see the beam a in fig3 about the optical axis i to emit out of the top surface of the lens 20 in which the light beam has a quite large light intensity in the direction of the axis y most of the light emitted from the led 10 is refracted out of the lens 20 and directed rightwards with an increase of the angle between light beam and the optical axis i the light intensity in the right side of the lens 20 firstly increases and then decreases from the optical axis i to positions a c e in sequence wherein the peak light intensity occurs at position a and the zero light intensity occurs at position e with the increase of the angle between light beam and the optical axis i the light intensity in the left side of the lens 20 keeps decreasing from the optical axis i to positions b d f wherein the zero light intensity occurs at position f also referring to fig4 in the direction of the axis x with the increase of the angle between light beam and the optical axis i the light intensity firstly increases and then rapidly decreases from the optical.