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�������պ����ѧѧ�� 2008, Vol. 34 Issue (09) :1032-1036    DOI:
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1. �������պ����ѧ ��е���̼��Զ���ѧԺ, ���� 100191;
2. ������������������, ���� 100039
Performance analysis and improvement on acutely defocused scenes
Sun Minglei1, Shi Jingxin1, Dong Dai2, Zong Guanghua1*
1. School of Mechanical Engineering and Automation, Beijing University of Aeronautics and Astronautics, Beijing 100191, China;
2. Beijing Aerospace Control Device Institute, Beijing 100039, China

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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.
Keywords�� vision   focus   image   Fourier transform   micro-manipulation     
Received 2007-08-27;
Fund:

����863�ƻ�������Ŀ(2004AA404260);����"ʮ��""211"ѧ�ƽ���������Ŀ

About author: ������(1974��),��,�����差��,��ʿ��,sunminglei@gmail.com.
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������,ʯ����,����,�ڹ⻪.Զ�����۽����ܷ��������[J]  �������պ����ѧѧ��, 2008,V34(09): 1032-1036
Sun Minglei, Shi Jingxin, Dong Dai, Zong Guanghua.Performance analysis and improvement on acutely defocused scenes[J]  JOURNAL OF BEIJING UNIVERSITY OF AERONAUTICS AND A, 2008,V34(09): 1032-1036
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