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