| 摘要 |
PCT No. PCT/GB90/01768 Sec. 371 Date Jul. 17, 1992 Sec. 102(e) Date Jul. 17, 1992 PCT Filed Nov. 16, 1990 PCT Pub. No. WO91/11879 PCT Pub. Date Aug. 8, 1991.To avoid burn in a scanning cathode ray tube, the address of the scanning spot at each clock period is recorded in a memory. During each frame period, the logarithms of the number of occurrences of each address are fed to a peak detector. The peak value is used to determine a maximum allowable beam current for the next frame. In another embodiment, the number of occurrences of each address during a line period is monitored and if this number exceeds a given number the CRT is blanked. |
