Indication position estimation by the homography of planes

To get a rapid estimation of the user's indication position in computer vision based noncontact human-computer interaction (HCI) system, an indication position estimation method without explicitly calculating the cameras' parameters. The homography matrix is calculated using the known points on the target plane and their corresponding points imaged by the cameras. By this homography relationship, the two lines which intersect at the indication point on the target plane are related with their corresponding lines on the image plane, thus the position of the indication point is estimated by detecting specific lines from images. Experimental results show that the average error of the homographic mapping is 0.726 mm at the distance of 2.5 m; meanwhile, the amplitude of errors rises by 2.6% from the center to the fringe of the screen (size of the screen is 2500 mm ×1800 mm). The precision and consistency of this method can satisfy the requirement of most applications in human-computer interaction.