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