Synchronization of cameras in camera-based touch system to enhance position determination of fast moving objects

In a camera-based touch system including at least one pair of cameras having overlapping fields of view and a touch surface encompassed within said overlapping fields of view across which a pointer is moved, wherein the cameras of said at least one pair acquire images at intervals asynchronously, a method of estimating the position of said pointer relative to said touch surface from image data acquired by said at least one pair of cameras, said method comprising the step of:

• for each camera in said pair:
• processing each acquired image to determine the position of said pointer therein and recording the position together with a timestamp representing the time elapsed between a reference point common to said cameras and the time the image was acquired;
• and
• interpolating between successive pairs of recorded positions to generate interpolated positions and recording said interpolated positions together with synchronization times representing times the images would have been acquired had said cameras been synchronized;
• and
• determining interpolated positions generated by said cameras having equivalent associated synchronization times and triangulating the interpolated positions to estimate the position of the said pointer relative to said touch surface.

A camera-based touch system comprising:

• at least one pair of cameras associated with a touch surface and having overlapping fields of view encompassing said touch surface, said at least one pair of cameras acquiring images of said touch surface from different locations and generating image data;
• a processor receiving and processing the image data generated by said at least one pair of cameras to determine the location of an object relative to the touch surface by triangulation when the object is captured in images acquired by the at least one pair of cameras;
• and a synchronization mechanism to synchronize image data generated by said at least one pair of cameras;
• wherein each camera processes each image acquired thereby to determine the position of the object therein and records the position together with a timestamp representing the time elapsed between a reference point common to said cameras and the time the image was acquired, and wherein said synchronization mechanism interpolates between successive pairs of recorded positions to generate interpolated positions, the interpolated positions being recorded together with synchronization times representing times the images would have been acquired had said cameras been synchronized, said processor using interpolated positions generated by the cameras having equivalent associated synchronization times to determine the location of the object using triangulation.