Minimum parallax stylus detection subsystem for a display device

摘要

A minimum parallax stylus detection subsystem is disclosed for use with a graphic input grid overlay which is positioned on the viewing surface of a display device. The invention has a three phase operation wherein, during the first phase, the stylus is at a remote distance from the viewing surface of the display and therefore no representation of the stylus position is displayed. During a second phase, the stylus is brought within a first threshold distance from the viewing surface of the display, during which a cursor image is generated which is precisely positioned on the display corresponding to the detected position of the stylus. During a third phase of operation of the invention, the stylus is brought within a close proximity of the viewing surface of the display, during which the cursor image is removed from the display and an actual trace of the path of the stylus with respect to the graphic input grid overlay is shown. In this manner, the operator can focus attention on the displayed location of the cursor instead of on the physical location of the stylus, thereby minimizing the parallax error in the location of the stylus with respect to the displayed image.