Visual tracking is essential for many applications such as vision-based control of intelligent robots, surveillance, agriculture
automation, medical image processing, and so on. Especially, a fast and reliable visual tracking is important since the performance
of visual tracking determines the reliability and real-time characteristics of overall system. It is not easy in visual tracking,
however, to estimate the configuration of a target object in real-time when the three-dimensional pose of the target object
is changing. On the contrary, a human being is able to track an object without the estimation of three-dimensional pose of
the object even though three-dimensional rotations and /or occlusion by other objects change the original image of the object.
This paper proposes a fast and reliable SSD-based visual tracker insensitive to three-dimensional rotation of an object as
well as translation, two-dimensional rotation, scaling, and shear of an object by proposing a performance measure for distortion
of current image with respect to an original reference image. The performance measure is a combination of aspect ratio of
a rectangle, variations of four internal angles of the rectangle from ninety degrees, the direction of rotation and the angular
velocity of the rectangle. So, the reference image for visual tracking is updated whenever the performance measure is greater
than an initialized distortion rate without the estimation of three-dimensional pose of an object. The algorithm is experimented
in real-time successfully at a personal computer adopted with a general-purpose frame grabber.