在成像型全向激光告警系统中，大视场探测与精确定向构成一对矛盾。为提高全向激光告警的定向精度，需要对激光光斑进行亚像素级的精确定位。在分析了鱼眼镜头大视场聚焦探测像差引起的光斑非对称性，并且信息量不足，不易于实现亚像素激光中心定位的基础上，提出通过镜头离焦的成像方式探测激光，使得激光在成像面上形成一定大小的弥散圆形光斑。在面阵探测器获取光斑采样像素点的基础上，通过双三次B样条插值曲面重建圆形光斑。并提取一定灰度值的光斑圆周插值点，作为圆形光斑边缘。通过快速Hough算法计算圆心，从而实现光斑中心的亚像素精度定位。通过实验对比验证，说明该方法可有效地提高激光光斑中心定位精度。

In omni-directional laser warning system, the contradiction between wide Field of View (FOV) and the precise directionality is expounded. In order to realize precise directionality, laser spot should be located precisely in sub-pixel. Based on analyzing the asymmetry of the spot in focused detecting mode caused by optical aberration, and the fact that the information is not enough for locating the center of the spot, a new method is put forward. The fish-eye lens works in defocused mode, so a defocusing circular laser spot with more sampling pixels and gray information is acquired. The gray value of the laser spot is interpolated by bicubic B-spline surface interpolation. The circular laser spot is rebuilt. The circular interpolated points with given gray-value are extracted as the verge of the spot. The center of the circular points is calculated out by Hough transform. The algorithm is verified by experiment, and it shows that it is effective for precise locating in laser spots.