1. A display apparatus comprising: a signal processor which processes a plurality of image frames; a display unit which displays the plurality of image frames processed by the signal processor; and a controller configured to control the signal processor to interleave a plurality of pattern frames between the plurality of image frames and to display the plurality of images frames which are interleaved with the plurality of pattern frames, wherein the plurality of pattern frames are pieces of pattern information, and wherein the pattern information is used by an external apparatus to identify the display apparatus.