The optical device 11, wherein {HEAD ~ the surface area} of the used part is {TAIL ~ no more than one third} of the total surface area of the spatial light modulating element 
The optical device 11 , wherein { HEAD ~ the surface area } of the used part is { TAIL ~ no more than one third } of the total surface area of the spatial light modulating element
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH