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