Recent Paper
August 1998 IEEE Consumers Electronics
 " Simultaneous out-of-focus blur estimation and restoration for digital auto-focusing system "

Disadvantage of current auto-focusing algorithm
Requires electrically powered movement of focusing lens -- mechanical parts for the motor-driven control module.

Proposed method
Requires only ONE frame of the defocused image and digital image processing techniques .

Idea

  • Divide input image into multiple sub-images or blocks

  • Determine the set of blocks which contain linear edge

  • Estimate step response across the edge for each block

  • Compute the 1D step response by averaging

  • Estimate 2D point spread function from the averaged step response

  • Based on the estimated PSF, design an image restoration filter to produce the in-focus image

    • Some results from the paper
    1) Illustrations of the various steps for the experiment.

    a) Original image
    b) Image is defocused
    c) Detecting the linear edges
    d) Average one step response
    e) Estimated 2D point spread function
    f) Restored image


    2) Another example

    a) Defocused image
    b) 2D point spread function
    c) Restored image

    Pay attention to the sharpness of the edges as well as the numbers in c)



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