基于图像功率谱的航空光电平台自动检焦设计  

Power Spectra-Based Auto-Focusing Method for Airborne Optoelectronic Platform

作　　者：赵志彬[1,2] 刘晶红[1] 

机构地区：[1]中国科学院长春光学精密机械与物理研究所,吉林长春130033 [2]中国科学院研究生院,北京100049

出　　处：《光学学报》2010年第12期3495-3500,共6页Acta Optica Sinica

基　　金：国家973计划(2009CB72400105)资助课题

摘　　要：针对航空光电平台中可见光摄像机在高空中由于温度、气压等环境参数的变化所引起的光学系统离焦现象,对基于图像功率谱的清晰度评价算法和检焦搜索算法进行了研究。分析了不同场景的航拍图像的功率谱具有一定的不变性。根据离焦会引起功率谱高频分量的损失,提出了两种对功率谱和对焦评价算子(PSS)的改进。针对航拍易受到环境干扰的问题,提出了变步长的全局搜索算法(FS)。使用1mm的搜索步长,调焦误差为0.3 mm,满足系统对误差的要求。所提出的两种基于图像功率谱的清晰度评价算法能够有效反映出实际航拍图像的离焦状态,并分别使对焦评价函数的饱和区特性和灵敏度得到改善。调焦实验的结果表明,小于镜头焦深的检焦步长才能保证检焦结果的正确。In order to retrieve the defocus in the optical system of airborne camera caused by the changes of temperature,pressure and other environment parameters in high altitude,focus measure algorithm based on power spectra and auto-focus search strategy are represented.Firstly,it is introduced that the power spectra of images taken from different region has the characteristic of invariance.Two betterments over the power spectra sum（PSS） focus measure function are proposed based on the main attenuation of power spectra in the high frequency.Then,full search（FS） strategy using changed steps is proposed in order to reduce the focus error caused by noise from environment.The results show that the FS strategy can locate the optimal focus position accurately when using search step length of 1 mm.The focus error is 0.3 mm which fulfills the requirement of system.The PSS proposed algorithms can indicate the defocus state of images taken by airborne camera,and it can also improve the properfies of saturation region and sensitiveness of the focus measure curve respectively.Search steps shorter than focus-depth can guarantee the validity of the result.

关 键 词：成像系统 航空光电平台 自动调焦 图像功率谱 对焦评价函数 搜索策略 

分 类 号：TP391[自动化与计算机技术—计算机应用技术] TN386.5[自动化与计算机技术—计算机科学与技术]