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电视系统中的干扰大体上可以分为三类:交流干扰、周期性脉冲干扰和随机起伏杂波.前二种是从外部电路感应得来,如果电路装配良好,完全可以消除.起伏杂波则是由电路元件本身如摄象管、电子管、电阻等的固有的特性所引起,因此这种干扰原则上不能消除,只能尽量使其降低到最小的程度.电视中杂波对图象质量的损害主要在于降低了图象的清晰度和灰度级数,同时在视觉上引起令人厌恶的闪烁感觉.在杂波电平高于信号电平的极端情况下,甚至使图象变得无法辨认.因此,如何评定与测量电视系统中的信杂比,便成为电视测量技术中的一个
Interference in TV systems can be roughly divided into three categories: AC interference, periodic pulse interference and random fluctuations. The first two are induced from an external circuit and can be completely eliminated if the circuit is properly assembled. Is caused by the inherent characteristics of the circuit elements themselves, such as video tubes, tubes, resistors and the like, so that such interference can not be eliminated in principle and can only be minimized to the minimum extent. The damage mainly consists in reducing the sharpness and gray scale of the picture while visually causing a disgusting flicker feeling that even at the extreme of the clutter level above the signal level makes the picture impossible Therefore, how to measure and measure the signal to noise ratio in a television system has become one of the television measurement techniques