Method and apparatus for applying multi-autofocusing (af) using contrast af

Abstract

A method applies fast and accurate autofocusing (AF) by using a contrast AF method in a digital photographing apparatus. In the digital photographing apparatus, when AF peaks of a subject of a central multi-point and a subject of a nearest multi-point are detected, further scanning is not performed. In addition, scanning is not performed on a region from which it is difficult to detect a peak, so that fast and accurate AF may be performed.

What is claimed is: 
     
         1 . A digital photographing apparatus which applies multi-point AF via contrast AF, the digital photographing apparatus comprising:
 taking lenses;   an imaging device, which generates image signals by converting image light from an object incident via the taking lenses into electric signals;   a driving unit, which drives a focusing lens of the taking lenses;   a calculating unit, which calculates AF evaluation values by performing AF detection with respect to the image signals;   a multi-point AF detecting unit, which divides a photographed image formed of the image signals into a plurality of focal point detecting areas and detecting the peak of AF evaluation values of each of the focal point detecting areas; and   a main object determining unit, which, if the peak value at a center of the image and a peak location of a closest object are detected by the multi-point AF detecting unit, stops detection of other peaks, selects one from among a plurality of peaks detected by the searching unit based on a pre-set multi-point AF reference, determines an object corresponding to the selected peak value as the main object, and detects contrast AF thereof.   
     
     
         2 . A digital photographing apparatus which applies multi-point AF via contrast AF, the digital photographing apparatus comprising:
 taking lenses;   an imaging device, which generates image signals by converting image light from an object incident via the taking lenses into electric signals;   a driving unit, which drives a focusing lens of the taking lenses;   a calculating unit, which calculates AF evaluation values by performing AF detection with respect to the image signals;   a multi-point AF detecting unit, which divides a photographed image formed of the image signals into a plurality of focal point detecting areas and detecting the peak of AF evaluation values of each of the focal point detecting areas;   a searching unit, which continues detection of other peak values, even if a particular peak value is obtained; and   a main object determining unit, which selects one from among a plurality of peaks detected by the searching unit based on a pre-set multi-point AF reference, determines an object corresponding to the selected peak value as the main object, and detects contrast AF thereof.   
     
     
         3 . A contrast AF detecting device comprising:
 taking lenses;   an imaging device, which receives object light via the taking lenses;   a driving unit, which drives a focusing lens of the taking lenses in the light-axis direction;   a multi-point focal point detecting unit, which divides a portion of an image captured by the imaging device into a plurality of focal point detecting areas, determines AF evaluation values in each of the focal point detecting areas, and determines peak values of the AF evaluation values;   a searching unit, which determines AF evaluation values while driving the focusing lens;   a main object detecting unit, which comprises an algorithm for prioritizing an object in the focal point detecting area at a center of the captured image from among a plurality of objects corresponding to the peak values of the AF evaluation values of the respective focal point detecting areas; and   a control unit, which focuses the focusing lens based on a result of the detection by the main object detecting unit,   wherein, even if the peak value corresponding to the object in the focal point detecting area at the center of the captured image is detected, if the peak value corresponding to a closest object is not yet detected, the searching unit is operated to determine the peak value corresponding to the closest object.   
     
     
         4 . A contrast AF detecting device comprising:
 taking lenses;   an imaging device, which receives object light via the taking lenses;   a driving unit, which drives a focusing lens of the taking lenses in the light-axis direction;   a multi-point focal point detecting unit, which divides a portion of an image captured by the imaging device into a plurality of focal point detecting areas, determines AF evaluation values in each of the focal point detecting areas, and determines peak values of the AF evaluation values;   a searching unit, which determines AF evaluation values while driving the focusing lens;   a main object detecting unit, which comprises an algorithm for prioritizing an object in the focal point detecting area at the main object from among a plurality of objects corresponding to the peak values of the AF evaluation values of the respective focal point detecting areas; and   a control unit, which focuses the focusing lens based on a result of the detection by the main object detecting unit,   wherein, even if the peak value corresponding to the object in the focal point detecting area at a closest object is detected, if the peak value corresponding to a center of the captured image is not yet detected, the searching unit is operated to determine the peak value corresponding to the center of the captured image.