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