复杂背景下低信噪比弱小目标的自动检测是当今目标自动探测研究尚未解决的一个难题。针对复杂天空背景条件下低信噪比的红外弱小目标检测问题，提出了一种基于中值滤波和多向梯度搜索相结合的目标检测算法。算法首先运用中值滤波器将目标从红外背景中分割出来，再结合多向梯度判决算法提取出真实目标点，最后辅以形态滤波填充目标内部空间，构成完整目标区域。实验及结果分析表明，基于中值滤波和多向梯度搜索目标检测算法能实时有效地检测出复杂天空背景下的红外弱小目标。

The automatic detection of dim infrared target with low Signal Noise Ratio (SNR) under complicated background is a difficult problem to be resolved. In study of the problem, we proposed a target detection algorithm based on median subtraction filter and multi-grad search algorithm. Firstly, the dim target was separated from infrared background by using median filter. Then, the real target was extracted by using multi-grad search algorithm. Finally, morphology-based algorithm was used to fill the inner space of target for constructing the entire area of target. The results of some physical experiments showed that this method can detect the weak and small infrared target under complex background effectively in real time.