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A New Auto-focusing Method Based on the Center Blocking DCT

A New Auto-focusing Method Based on the Center Blocking DCT. Quan Feng, Ke Han, Xiu-chang Zhu College of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China Presenter ：梁正勳 Number:97662003 Teacher: 吳宗益. Outline.

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A New Auto-focusing Method Based on the Center Blocking DCT

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  1. A New Auto-focusing Method Based on the Center Blocking DCT Quan Feng, Ke Han, Xiu-chang Zhu College of Telecommunications and Information Engineering, Nanjing University of Posts and Telecommunications, Nanjing 210003, China Presenter：梁正勳 Number:97662003 Teacher:吳宗益

  2. Outline • Introduction • Imaging in different object distances • The method based on the center blocking DCT • Experimental Results • Conclusions

  3. Introduction • This paper analyses the imaging relations of the lens system and the properties of image clarity evaluation function under the condition where the object distances of many objects are different. • A center window method is employed to stand out the interesting objects. • The image clarity evaluation function based on the center blocking DCT method is proposed for evaluating the image clarity in this paper.

  4. Imaging in different object distances • Imaging in long-object-distance situation • Imaging in the long-short-object-distance situation

  5. Center window method • We often put the interesting objects in the center of the camera aperture. • How to select the proper size of the center window plays a very important part in auto focusing system. • First, the rows and columns of two-dimensional original image are divided into three equal parts,respectively. • Thus, nine image blocks are acquired from original image. • Its area is 1/9 of the whole image area. • The size of window can be adaptively adjusted with the resolution of image.

  6. The image clarity evaluation function based on the center blocking DCT method Figure 2. Blocking method

  7. Experimental Results • Background is far away from the object

  8. Long-short-object-distance situation • Background is closed to the object

  9. Long-object-distance situation

  10. the proposed method VS the traditionalhigh frequency method The first group of test images

  11. the proposed method VS the traditionalhigh frequency method The second group of test images

  12. the proposed method VS the traditionalhigh frequency method The third group of test images

  13. Conclusions • A center window method is proposed in this paper. • It will spare computational time. • The image clarity evaluation function based on the center blocking DCT method. • The proposed methods can effectively focus the images under the different object distance conditions.

  14. The End Thank you for your attentions !

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