INVESTIGATION OF AN ANALOG TECHNIQUE TO DECREASE PEN-TRACKING TIME IN COMPUTER DISPLAYS

摘要

Many modern digital computer systems contain cathode-ray-tube display equipment to facilitate man-machine communications. Through the use of a display and a light-sensitive pen, graphical material can be directly inserted into the computer by using the pen to control the position of the electron beam at the face of the CRT--a process called pen tracking. Beam position is continually sampled by the computer, permitting continuous display of the material being sketched. In present digital pen-tracking techniques, a tracking pattern (usually a cross) with a substantial number of points is generated on the face of the CRT and the binary response of the pen to the individual points of the pattern is employed to calculate pen position. The large number of pattern points, and the phosphor decay time associated with each, yield a typical tracking cycle of 500 to 1000 micro¬seconds. Since the cycle must be repeated about 100 times per second, 5 to 10 percent of display time is consumed.