The diffuser plate 4 has {HEAD ~ the function} of emitting light source light diffusingly in {TAIL ~ a predetermined angular range} 
The diffuser plate 4 has { HEAD ~ the function } of emitting light source light diffusingly in { TAIL ~ a predetermined angular range }
OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL