the manufacturing method as shown in fig9 in addition as for the light pipe since the circumferential wall of the light pipe can reflect excited light such as blue laser beams and transmit excited light such as yellow light beams the light pipe will not affect the function of the reflector but the wall thickness of the light pipe will affect the light efficiency of the illuminating device 10 fig1 is a schematic diagram of light deviation caused by wall thickness of the light pipe as shown in fig1 when light beams reflected from the phosphor are incident upon an inner wall of the light pipe the light beams will be deviated to a certain degree when emerging from an outer wall of the light pipe due to influence of refraction as shown in fig1 the bigger the incident angle is the more the deviation is and a relation between deviation u03b4 wall thickness d of the light pipe and angles u03b8 1 and u03b8 2 is u03b4 d x 1 u2212 tg u03b8 2 tg u03b8 1 according to which it can be obtained that a maximum deviation u03b4 equals the wall thickness d of the light pipe such light deviation will cause the phosphor to appear bigger for instance as shown by the broken lines to the left of the phosphor in fig1 thus a bigger equivalent light spot will be generated at the focus f2 resulting a reduced light collecting efficiency of the.