Position Detection on Static Displays
Original Publication Date: 1983-Aug-01
Included in the Prior Art Database: 2005-Feb-07
So-called light pens (hand-held photo receptors) have long been in wide use with respect to CRT displays. The usual method of operation is by time coincidence between instantaneous illumination of a spot on the CRT screen by the flying CRT beam and the position of data in a regeneration buffer which drives the display. This method cannot be used directly with static displays, such as liquid crystal or plasma panel displays. Described here is a system which overcomes this problem. The system has three key parts. The first part is the probe. The probe is similar to the one used for CRTs, except the optics and light sensor are matched to the display. The second is the image backup RAM (random-access memory). The last part is the unique circuitry that controls the scan.