Trajectory detection and feedback system for tennis

A non-transitory computer readable medium configured to store a computer program used by a computer, the computer readable medium comprising:

• computer code configured to receive image data from one or more sensors worn on a user's head wherein the image data includes images of a real tennis ball being hit towards the user on a real tennis court;
• based upon the image data, computer code configured to determine a position of the real tennis ball as a first function of time;
• computer code configured to control generation of images of a virtual tennis ball as a second function of time which are output to a display worn on the user's head which projects images into at least one of a user's eyes to mimic a position of the real tennis ball as the function of time approaching the user from a perspective of the real tennis ball on the tennis court as viewed through the user's eyes on the real tennis court wherein the images of the virtual tennis ball approaching the user are generated based upon the image data received by the one or more sensors;
• when the virtual tennis ball is determined to be hit, computer code configured to trigger a haptic sensation generator in a hand-held device wherein the haptic sensation generator transmits one or more haptic sensations to the user which mimic a feel of the real tennis ball being hit;
• and
• based upon a position and an orientation of a hand-held device as the second function of time and a virtual position of the virtual tennis ball as the second function of time, computer code configured to control generation of second images of the virtual tennis ball which are output to the display worn on the user's head and which show the virtual position of the virtual tennis ball as the second function of time after the virtual tennis ball is determined to be hit moving away from the user from the perspective of the real tennis ball as viewed through the user's eyes on the real tennis court.