{TAIL ~ an acquisition unit} adapted to acquire a brightness of the image displayed on the display surface by {HEAD ~ said display unit}; and 
{ TAIL ~ an acquisition unit } adapted to acquire a brightness of the image displayed on the display surface by { HEAD ~ said display unit } ; and
TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH