Digital focusing method and apparatus in image processing system

An image processing device having a processor and associated memory, comprising:

• means for dividing a defocused image into sub-images of a predetermined size;
• means for estimating an edge direction of each of the divided sub-images;
• means for calculating step responses for respective edge directions;
• and
• means for obtaining a mean step response by averaging a predetermined number of the step responses, obtaining Point Spread Function (PSF) coefficients using the mean step response, obtaining an image blur transfer function using the PSF coefficients, obtaining an image restoration transfer function using the image blur transfer function, and obtaining an in-focused image by multiplying the image restoration transfer function by the defocused image in a frequency domain.

An image focusing device comprising:

• a transfer function calculator for calculating PSF coefficients and calculating an image blur transfer function represented in a frequency domain;
• a first absolute value calculator for calculating the absolute value of the input image blur transfer function;
• a first squarer for squaring the absolute value of the blur transfer function;
• a complex conjugate calculator for calculating a complex conjugate of the image blur transfer function;
• a second absolute value calculator for calculating the absolute value of a predetermined input operator;
• a second squarer for squaring the absolute value of the predetermined operator;
• a first multiplier for multiplying the output of the second squarer by a Lagrange multiplier;
• an adder for adding the output of the first multiplier to the output of the first squarer;
• a divider for dividing the output of the adder by the complex conjugate and outputting an image restoration transfer function;
• and
• a second multiplier for multiplying the image restoration transfer function by an out-of-focus image represented in the frequency domain, and outputting the product as an in-focused image.