{HEAD ~ A black area measurement section} measures {TAIL ~ a black area S} by obtaining ratio of the number of pixels satisfying Y≦Y0 in the screen 
{ HEAD ~ A black area measurement section } measures { TAIL ~ a black area S } by obtaining ratio of the number of pixels satisfying Y≦Y0 in the screen
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH