Each of the layers 112 is separated by a second relatively thick layer 116 composed of a material having {HEAD ~ a relatively low index} of {TAIL ~ refraction} 
Each of the layers 112 is separated by a second relatively thick layer 116 composed of a material having { HEAD ~ a relatively low index } of { TAIL ~ refraction }
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL