Autofocus method

A image acquisition device that automatically focuses on a scene, comprising:

• (a) a focusing means and image capture component for acquiring multiple images each having the focusing means focused at a different focus distance;
• (b) a processor
• programmed to perform an autofocus method, including the steps of:
• (i) determining a sharpest image among the multiple images;
• (ii) computing horizontal, vertical or diagonal integral projection vectors, or combinations thereof, for each of the multiple images;
• (iii) convoluting one or more integral projection vectors of the sharpest image with multiple filters of different lengths to generate one or more filtered integral projection vectors for the sharpest image;
• (iv) computing differences between the one or more filtered integral projection vectors of the sharpest image and one or more integral projection vectors of at least one of the other images of the multiple images;
• (v) estimating at least one blur width between the sharpest image and the at least one of the other images of the multiple images as a minimum value among the computed differences over a selected range;
• (vi) repeating steps (i)-(v) one or more times to obtain a sequence of estimated blur width values;
• and
• (vii) adjusting a focus position based on the sequence of estimated blur width values.

One or more non-transitory, processor-readable devices having code embedded therein for programming a processor to perform a method of automatically focusing an image acquisition device on a scene, the method comprising the steps of:

• (a) acquiring multiple images each having a focusing means of an image acquisition device focused at a different focus distance;
• (b) determining a sharpest image among the multiple images;
• (c) computing horizontal, vertical or diagonal integral projection vectors, or combinations thereof, for each of the multiple images;
• (d) convoluting one or more integral projection vectors of the sharpest image with multiple filters of different lengths to generate one or more filtered integral projection vectors for the sharpest image;
• (e) computing differences between the one or more filtered integral projection vectors of the sharpest image and one or more integral projection vectors of at least one of the other images of the multiple images;
• (f) estimating at least one blur width between the sharpest image and the at least one of the other images of the multiple images as a minimum value among the computed differences over a selected range;
• (g) repeating steps (b)-(f) one or more times to obtain a sequence of estimated blur width values;
• and
• (h) adjusting a focus position based on the sequence of estimated blur width values.