| 摘要 |
An anti-blister circuit comprises a first detector for detecting amplitude excursions of a signal with luminance information beyond a white level threshold during each horizontal scan. This enables the circuit to be more sensitive by responding to excursions occurring during each horizontal scanning line. A first timer, responsive to the first detector, provides a first control signal related to a minimum duration of each amplitude excursion of the signal beyond the threshold. This enables the circuit to avoid controlling beam current, for example by reducing contrast, responsive to signal peaks which are too short to cause blistering or warping. Finally, a switch and second timer, responsive to the first control signal, provide a second control signal which falls at a first rate to reduce beam current, for example by reducing contrast, during each minimum duration amplitude excursion; and, which rises at a second rate to permit the beam current to increase after termination of the amplitude excursion, until the next minimum duration excursion. The time constant for the second rate is much greater than the time constant of the first rate.
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