Performance analysis and improvement on acutely defocused scenes
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摘要: 传统聚焦测度函数在远焦区对图像高频能量解析性能较差;表现为聚焦曲线在远焦区呈现非单调性.利用傅里叶变换方法对图像频谱进行分析:在远焦区,聚焦图像序列的直流分量表现出强烈的波动性,并且直流分量在图像频谱中占据绝对比例,再加上传统聚焦函数滤除图像直流分量的能力较弱,导致误聚焦概率高.考虑到频域聚焦函数计算量大,提出基于时域的两个聚焦函数.实验结果表明:此二函数具有强的直流分量滤除能力,能有效改善聚焦曲线在远焦区的表现,同时具有高的聚焦分辨率.远焦区聚焦性能的改善对于提高显微视觉操作自动化的可靠性尤为重要.Abstract: Some classic focusing measures such as gradient function, Brenner function and entropy function, et al, show poor performance in computing high frequency energy in acutely defocused images. Their focusing curves away from the focus show serious nonmonotonicity. The Fourier transform method for image series spectrum analysis was conducted. Three reasons for poor performance in far away focus region were proposed. Firstly, defocused image sequences show strong volatility in power of DC(direct current) component. Secondly, DC component of the image spectrum occupies an overwhelming proportion. Thirdly, the traditional measures have weak ability in filtering DC component of image. According to this, two spatial focusing measures were presented. Experiment results show that performance of focusing curves of acutely defocused images was significantly improved, and high focus resolution can be achieved. This method is particularly important in enhancing reliability of automatic micromanipulation based on microscopic vision.
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Key words:
- vision /
- focus /
- image /
- Fourier transform /
- micro-manipulation
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[1] Geusebroek J M,Cornelissen F,Smeulders A W M,et al．Robust autofocusing in microscopy[J]．Cytometry,2000,39:1-9 [2] Santos A,Solorzano C O D,Vaquero J J,et al．Evaluation of autofocus functions in molecular cytogenetic analysis[J]．Journal of Microscopy,1997,188(3):264-272 [3] Yeo T,Ong S,Sinniah R．Autofocusing for tissue microscopy[J]．Image Vision Comput,1993,11:629-639 [4] Groen F,Young I T,Ligthart G．A comparision of different focus functions for use in autofocus algorighms[J]．Cytometry,1985,12:81-91 [5] Vollath D．The influence of the secne parameters and of noise on the behaviour of automatic focusing algorithms[J]．J Microsc,1988,151:133-146 [6] Allegro S,Chanel C,Jacot J．Autofocus for automated microassembly under a microscope[J]．Image Processing,1996,2:677-680 [7] Brenner J F,Dew B S, Horton J B,et al．An automated microscope for cytologic research[J]．Cytometry,1971,24:100-111 [8] Sun Minglei,Zong Guanghua,Bi Shusheng,et al． Research on wavelet based autofocus evaluation in micro-vision[J]．Chinese Journal of Aeronautics, 2006, 19(3): 239-246 [9] Tamura H,Mori S,Yamawaki T．Texture features corresponding to visual perception[J]．IEEE Trans on System,Man and Cybernetics,1978,8(6):460-473 [10] Yang G,Nelson B J．Wavelet-based autofocusing and unsupervised segmentation of microscopic images Proceedings of the 2003 IEEE/RSJ International Conference on Intelligent Robotics and Systems. Piscataway,NJ:IEEE,2003,3:2143-2148 -
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