Simultaneous out-of-focus blur estimation and restoration for digital auto-focusing system

  • Authors:

  • Sang Ku Kim;Sang Rae Park;Joon Ki Paik

  • Affiliations:

  • Dept. of Electron. Eng., Chung-Ang Univ., Seoul;-;-

  • Venue:
  • IEEE Transactions on Consumer Electronics
  • Year:
  • 1998

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Abstract

We propose a simultaneous out-of-focus blur estimation and restoration technique for a fully digital auto-focusing system. The proposed auto-focusing system can make in-focused images by using only digital image processing techniques, and it requires neither infrared light or ultrasound nor a focusing lens assembly operated by a motor. As a result, it can provide savings in the volume and cost of the imaging system, which contains the proposed auto-focusing system. The proposed system first divides the input image into multiple sub-images or blocks, determines the set of blocks which contain linear edges, estimates the step response across the edge for each block in the selected set, computes the one-dimensional step response by averaging the step responses, estimates the two-dimensional point spread function (PSF) from the averaged step response, and finally provides in-focused image by an image restoration filter based on the estimated PSF. There is a limit on the amount of out-of-focus, which can be recovered by the proposed auto-focusing system. The proposed system operates under the assumption that an input image contains at least one piece-wise linear boundary between an object and the background. In spite of the above mentioned limitations, the proposed system can make an acceptable quality of focused image by using only digital signal processing