Method for correction of position location indicator for a large area

Abstract

In a large area display system, multiple persons may work together with multiple input devices for supplying and receiving information in an interactive system with a single large area display. The large area display system comprises a screen wherein computer generated information is projected upon one side of the screen, and users interact with the computer from the opposite side of the the screen. Data coordinates for an input device corresponding to a pseudo image sensed by the receiving subsystem electronics are provided to the controlling computer. The input data coordinates from the pseudo image are normalized for variations due to frequency dependence and electronic drift. The normalized data coordinates are looked up in a calibration table to account for distortion in the pseudo image detection electronics. Screen coordinates corresponding to pixel locations on the large area screen are found by interpolation from the data From the calibration table. The calibration table is prepared off-line, based on a bicubic spline interpolating function which is then compressed using a delta compression scheme. During on-line operation of the system, screen coordinates are looked-up directly from the compressed table. The screen coordinates are then jitter smoothed to provide a smooth path of response closely conforming to original input locations. The jitter smoothing method uses an exponential function based on the magnitude of the change in the position of the input.