the diffuser elements have an average space therebetween of {HEAD ~ 50 μm} to {TAIL ~ 300 μm}, 
the diffuser elements have an average space therebetween of { HEAD ~ 50 μm } to { TAIL ~ 300 μm } ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH