以往的背景杂波度量存在取固定经验性的权重值或忽略人眼视觉响应(HVS)等问题，无法准确度量背景杂波。提出一种新的杂波度量方法，这种方法引入最佳响应阈值模拟人眼对杂波响应的适应性，并利用该阈值研究背景的相似性对目标获取性能的影响，进而完成对杂波的度量。利用Search_2数据库验证该杂波度量方法的合理性。实验结果表明，基于该度量的目标获取性能预测与主观数据一致。目标探测概率的均方根误差为0.0835，相关系数分别为0.7124和0.7444；目标虚警概率的均方根误差为0.0691，相关系数分别为0.7874和0.6753；目标搜索时间的均方根误差为3.2321，相关系数分别为0.7630和0.7710。

As the previous clutter metrics have such problems as extracting the weight value from the fixed experience and taking no consideration of the human visual response, they cannot measure the background clutter accurately. We propose a new clutter metric, in which the optimal response threshold is introduced to simulate the adaptability of the human eye to the clutter response. The optimal response threshold is also used to evaluate the effect of the background similarity on the target acquisition performance so as to measure the clutter. The proposed metric is tested by the Search_2 database. The testing results demonstrate that the target acquisition performance prediction based on the clutter metric is in accordance with the subjective data. The mean square error of the target detection probability is 0.0835, and the correlation coefficients are 0.7124 and 0.7444; the square mean error of the target false alarm rate is 0.0691, and the correlation coefficients are 0.7874 and 0.6753; the square mean error of the target search time is 3.2321, and the correlation coefficients are 0.7630 and 0.7710.