针对传统检焦法复杂度高、稳定性差等问题,提出一种基于图像处理的自准直检焦方法。通过自准直法与图像处理相结合的方法来提高检焦系统的适应性与检焦精度;利用系统离焦距离增大引起成像分辨率降低特性,设计空间频率连续变化的辐射状靶标,避免靶标在系统离焦后对比度变化小的问题。仿真实验选用清晰度评价函数算子计算不同靶标离焦序列图的特征值曲线,结果表明辐射状靶标特征值曲线的灵敏度、无偏性、单峰性均优于Lena图和光栅靶标,且本文检焦法比传统自准直检焦法的检焦精度提高了约19.6%,满足光学系统对离焦量允许值的要求。

Traditional inspection and focusing methods have high complexity and poor stability. This paper presents a self-collimation inspection and focusing method based on image processing. The combination of the self-collimation focusing method and image processing method can improve system applicability and inspection and focusing accuracy. An increase in system defocusing distance leads to a decrease in imaging resolution. Radial targets continuously changing in three-dimensional space are designed to avoid the problem of a small change in contrast after defocusing. In the simulation, the evaluation function operator is selected to calculate the characteristic value curves of defocusing sequence graphs of different targets. The results show that the sensitivity, unbiasedness, and unimodality of the characteristic value curves of radial targets are better than those of Lena graphs and raster targets. The self-collimation inspection and focusing method based on image processing improves the precision of the original self-collimation inspection and focusing method by approximately 19.6%, and the required amount of the tolerant defocus is satisfied.