Human-machine interaction using the projection screen and light spots from multiple laser pointers

Multi-user laser pointers system, in which more than single people could use the laser pointers concurrently, has promising applications, such as group discussion, appliances control for several handicapped persons, controlling the large displays by a few users and the like. Conventional methods employed in the above-mentioned applications are common mouse, gesture control utilizing the Kinect sensor or leap motion, including the single laser pointer. Common mouse and single laser pointer could not meet the requirements, which let a few users operate simultaneously. And gesture control is limited to a far distance. Compared to multi-user laser pointers, the majority research focuses on single laser pointer. However, multiple users would suffer the dilemma in which each one is not able to point at the target on the screen any time, at far distance, just because the laser pointer is controlled by only one person. The paper proposes a novel way to make it possible that 3 laser pointers are pointing at the screen without intervening between each other. Firstly, the foreground with all the dynamic spots is extracted. On the foreground, these spots will be searched all the time by grasping the contours of them. Hence, various information of the spots like the coordinate, pixel value, area and so on is obtained. Secondly, a square image containing the whole spot is referred to as the input of the designing back propagation neural network. The BPNN output indicates the category to which the laser pointer belongs. An experiment verifies that it works well under certain light conditions (12-727lux) if green laser pointers are used.