Focus control apparatus, image sensor, program and storage medium

Abstract

A digital camera has distance measurement zone setting means ( 12 ) for dividing distance to a subject into a plurality of distance measurement zones; distance measurement zone selection means ( 13 ) for selecting a distance measurement zone to be scanned; an autofocus evaluation calculation circuit ( 14 ) for acquiring an AF evaluation value by scanning the selected distance measurement zone; zone-update determination means ( 15 ) for determining, through use of the AF evaluation value, whether or not to update a distance measurement zone to be scanned; and in-focus position decision means ( 16 ) for appropriately updating the scanned distance measurement zone based upon the determination as to whether to update the distance measurement zone, and deciding an in-focus position based upon acquisition of AF evaluation value. A focusing lens ( 2 ) is driven to the in-focus position by a focusing-lens drive circuit ( 17 ).

1. A focus conrtol  control apparatus for detecting in-focus position of a focusing optical system by performing scanning for driving the focusing optical system in accordance with a predetermined range of an object distance, comprising:
 a scanning area selection unit adapted to divide the object distance into a plurality of distance measurement areas and select an  distance measurement area to be scanned; and  
 an in-focus state acquisition unit adapted to acquire in-focus state of the focusing optical system by scanning the selected distance measurement area;  
 wherein said scanning area selection unit changes a method of dividing the distance measurement area to be scanned in accordance with conditions of photography and number of distance measurement areas to be divided is changed in accordance with the focal length.  
 
     
     
       2. The apparatus according to  claim 1 , wherein the number of distance measurement scanning areas to be divided is changed in accordance with focal length at time of photography. 
     
     
       3. The apparatus according to  claim 2 , wherein the greater the focal length at the time of photography, the larger the number of scanning areas to be divided is made. 
     
     
       4. The apparatus according to  claim 1 , wherein the number of scanning  distance measurement areas to be divided is changed also in accordance with f-stop value at time of photography. 
     
     
       5. The apparatus according to  claim 4 , wherein the more an aperture is stopped down, the smaller number of scanning areas to be divided is made. 
     
     
       6. An image sensor having an in-focus control apparatus defined in  claim 1 . 
     
     
       7. An image sensing apparatus that performs scanning in a distance measurement area by driving a focusing optical unit so as to determine in- focus state to an object, comprising:      a driving unit adapted to output driving signal to the focusing optical unit; and        a control unit adapted to divide the distance measurement area into plural areas and changes a method of dividing the distance measurement area,        wherein the number of distance measurement areas to be divided is changed in accordance with focal length.     
     
     
       8. The apparatus according to  claim 7 , wherein the method of dividing the scanning area is changed in accordance with conditions of photography. 
     
     
       9. The apparatus according to  claim 7 , wherein number of the divided areas is changed in accordance with focal length at time of photography. 
     
     
       10. The apparatus according to  claim 9 , wherein the greater the focal length at the time of photography, the larger the number of the divided areas is made. 
     
     
       11. The apparatus according to  claim 7 , wherein number of distance measurement areas is changed also in accordance with f- stop value at time of photography.   
     
     
       12. The apparatus according to  claim 11 , wherein the more an aperture is stopped down, the smaller number of divided areas is made. 
     
     
       13. The apparatus according to  claim 7 , wherein order of scanning of the divided areas is changed in accordance with conditions of photography. 
     
     
       14. The apparatus according to  claim 7 , wherein order of scanning of the divided areas is changed in accordance with luminance level at time of photography. 
     
     
       15. The apparatus according to  claim 7 , wherein order of scanning of the divided areas is set in accordance with mode of photography. 
     
     
       16. The apparatus according to  claim 7 , wherein order of scanning of the divided area is set giving priority to short distances in a flash photography mode.