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航空相机在执行对地观测任务时,需要精确地调焦控制系统实时调整镜头焦距以获得清晰的图像。本文以航空成像运行模式下的CCD拼接结构的特点,提出了一种智能的航空相机小波调焦方法。将图像处理的清晰度评价方法引入航空相机调焦系统,并考虑人类视觉系统(HVS)的特点设置权值,使评价效果更符合人类的主观感受。本文分析了小波基函数的性质,通过比较得出了采用symlet2小波进行三层分解构造的清晰度评价函数,对不同细节丰富程度的图像具有适应性,得到了灵敏度鲁棒性好的评价函数。并选取细节丰富的区域作为评价函数,详细地介绍了结合航空成像设备CCD拼接结构的特点,进行智能调焦的实现原理及方法。理论分析及仿真试验证实了该算法的可行性及有效性。相比传统评价方法具有较高的灵敏度,小波调焦方法的效率能够满足航空相机实时调焦的需求。
When performing aerial surveying missions, the aerial camera needs a precise focus control system to adjust the focal length of the lens in real time for clear images. In this paper, based on the characteristics of CCD mosaic structure in aerial imaging operation mode, an intelligent wavelet camera focusing method is proposed. The method of sharpness evaluation of image processing is introduced into the focusing system of aerial camera, and the weight is set according to the characteristics of human visual system (HVS) so that the evaluation effect is more in line with human subjective perception. In this paper, the properties of wavelet basis function are analyzed. The definition evaluation function of three-layer decomposition using symlet2 wavelet is constructed, which is adaptive to images with different detail levels. The evaluation function with good sensitivity and robustness is obtained. And the detail-rich region is selected as the evaluation function, and the principle and method of intelligent focusing are introduced in detail based on the characteristics of CCD stitching structure of aerial imaging equipment. Theoretical analysis and simulation results verify the feasibility and effectiveness of the proposed algorithm. Compared with the traditional evaluation method with high sensitivity, the efficiency of wavelet focusing method can meet the needs of real-time focusing of aerial camera.