At least one characteristic of an object is captured at a first instant and the at least one characteristic of the object is then captured at a second instant. A moving direction and a moving speed of the object are calculated according to the at least one characteristic of the object captured respectively at the first instant and the second instant. A left view image and a right view image are projected to the object and if the moving speed of the object is greater than a threshold, a center point of the left view image and the right view image deviates from a center line of the object.