The height of the convex parts and {HEAD ~ the pitch} between {TAIL ~ adjoining concave and convex parts} are selected so that projections produced by adjoining secondary light source images are displaced from each other by a half phase 
The height of the convex parts and { HEAD ~ the pitch } between { TAIL ~ adjoining concave and convex parts } are selected so that projections produced by adjoining secondary light source images are displaced from each other by a half phase
OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH