单幅图像估计离焦量的航空摄像机自动调焦系统

System of aerial camera auto-focus based on defocus estimate by single image

为了改进航空相机自动调焦的方法,解决传统对焦深度法自身不可避免的多峰值问题和实时性问题。本文提出一种新型自动调焦方法,建立了调焦模型,并通过实验装置验证了该方法,调焦时间相比传统方法短,实现了一次定位的调焦方法。首先,通过采集大量不同离焦程度的自然图像作为分析样本的总体,对总体中分类采样出小块样本进行运算分析,经过迭代运算获得所需模板;然后,在凸轮机构完成粗调焦以后采集当前图像,通过对当前图像采样,把采集的样本小块放入建立好的模板中计算,得到当前镜头的离焦量。最后,根据离焦量的结果,换算为调焦执行机构的位移量,驱动调焦电机移动相应位移完成调焦。实验结果表明：在目前实验条件下离焦量计算时间为0.4s,较传统方法的4～8s调焦时间有了大幅度提高。在保证调焦精度的前提下,实现了一种具有实时性的自动调焦方法。

In order to solve inevitably multimodal issues and real time problems of traditional focus depth method used in aerial camera, a new method for auto-focus is presented. A focus model is estab- lished, and the method is verified by modeling and experiments. Firstly, a large number of different defocus degree of natural images, which are used as the overall sample, are collected. The sample patch from the overall sample is analyzed, and the desire template is got by iteration. Secondly, after the cam completes the coarse focus, the current image is acquired. Then, the sample patches are put into the template through sampling the current image, and the current defocus level is got bycalculating defocus. Finally, according to the result of the defocus, the displacement of the actuator is converted. Then, the focus motor is driven to make the movement. The results show that the time to calculate defocus is 0.4 s, which has a great improvement compared with the traditional method whose focus time is 4～8 s. A real-time automatic focus method ensuring the focus accuracy is achieved.