The output surface is only partially reflective, thereby allowing {HEAD ~ a portion} of {TAIL ~ the light} to escape the wedge and provide the line of light which illuminates the document 
The output surface is only partially reflective , thereby allowing { HEAD ~ a portion } of { TAIL ~ the light } to escape the wedge and provide the line of light which illuminates the document
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH