基于单目视觉边缘频谱的散焦图像测距算法研究  

An improved algorithm for monocular camera edge spectrum based ranging by defocused images

作　　者：介邓飞 王浩 吕惠芳 田波涛 张展翔 JIE Deng-fei;WANG Hao;LV Hui-fang;TIAN Bo-tao;ZHANG Zhan-xiang(College of Mechanical and Electrical Engineering,Fujian Agriculture and Forestry University,Fuzhou 350002,China;Fujian Key Laboratory of Agricultural Information Sensoring Technology,Fuzhou 350002,China)

机构地区：[1]福建农林大学机电工程学院,福建福州350002 [2]福建省农业信息感知技术重点实验室,福建福州350002

出　　处：《中国光学（中英文）》2023年第3期627-636,共10页Chinese Optics

基　　金：福建省自然科学基金面上项目(No.2020J01577);福建省农业信息感知技术重点实验室项目(No.2021ZDSYS0101)。

摘　　要：为了实现基于单目相机的弱或无表面纹理特征目标精确测距,提出了一种基于保留边缘频谱信息的改进散焦图像测距算法。通过对比以傅立叶变换和拉普拉斯变换为计算核心的两种经典散焦测距理论,构建相应的清晰度评价函数,根据灵敏度更好的频谱清晰度函数选择基于频谱的散焦测距法,并根据频谱清晰度函数在保留目标边缘信息的基础上选择频域计算范围,从而进行测距。为验证算法的可行性,本文采用6组不同的鸭蛋样本,获取不同光圈、不同距离的散焦图像,利用该改进算法求解鸭蛋到相机镜头的距离。实验结果表明,基于边缘频谱保留的散焦图像测距改进算法具有良好的测距效果,相关系数为0.986,均方根误差为11.39 mm,并发现对于斜放拍摄的鸭蛋图像进行图像旋转处理后,可有效地提升测距能力,均方根误差从11.39 mm下降至8.76 mm,平均相对误差从2.85%下降至2.28%,相关系数提升至0.99。基本满足了弱或无表面纹理特征目标测距的稳定、精度等要求。In order to achieve accurate target ranging of weak or non surface texture features using a monocular camera,an improved defocused image ranging algorithm based on preserving edge spectral information is presented.By comparing two classical defocal ranging theories with Fourier transform and Laplace transform as the foundational principals of calculation,a corresponding definition evaluation function is constructed.We select the method based on the spectrum definition function with better sensitivity,and select the calculation range of the frequency domain by retaining the information on the target edge.To verify the feasibility of the algorithm,6 sets of different duck egg samples are used to obtain scattered focus images of different apertures and distances,and the improved algorithm was used to solve the distance of the duck eggs from the camera lens.The experimental results show that the improved algorithm based on the edge spectrum preservation has a good ranging effect with a correlation coefficient of 0.986 and Root Mean Square Error(RMSE)of 11.39 mm.It is found that the range ability can be effectively improved after the image rotation processing of the duck egg image taken at an oblique angle,with the RMSE is reduced from 11.39 mm to 8.76 mm,the average relative error is reduced from 2.85%to 2.28%and the correlation coefficient reaches 0.99.The proposed algorithm fundamentally meets the requirements of stability and high accuracy in ranging targets with weak or non surface texture features.

关 键 词：机器视觉 散焦测距 边缘频谱 图像处理 弱或无纹理特征 

分 类 号：TP39[自动化与计算机技术—计算机应用技术] S24[自动化与计算机技术—计算机科学与技术]