Phase difference detection method, phase difference detection apparatus, range finding apparatus and imaging apparatus

A phase difference detection apparatus comprising:

• a judgment unit for judging whether or not a predetermined compensation would be effective for compensating an image data row which is generated in response to outputs of a pair of optical sensor arrays on which images of an object are formed;
• a first phase difference detection unit for detecting a phase difference between the images formed on the pair of sensor arrays based upon the image data row when it is judged by the judgment unit that the predetermined compensation would not be effective;
• and
• a second phase difference detection unit for carrying out the predetermined compensation with respect to the image data row when it is judged by the judgment unit that the predetermined compensation would be effective and detecting a phase difference between the images formed on the pair of sensor arrays based upon the image data row after carrying out the predetermined compensation.

A range finding apparatus comprising:

• a pair of spaced-apart lenses for forming first and second images of an object spaced by a given distance from the respective lenses;
• a pair of optical sensor arrays respectively arranged behind the lenses relative to the object for producing first and second output signals corresponding to the images formed by the lenses;
• an A/D converter for converting the first and second output signals of the optical sensor arrays into corresponding first and second digital signals;
• a memory unit for storing the digital signals;
• a judgment unit for calculating a first difference in average values of the first and second digital signals and judging whether or not the first difference exceeds a first predetermined value;
• a compensation effectiveness unit for performing a compensation effectiveness determination if the first difference exceeds the first predetermined value by calculating a second difference between a maximum value of the first digital signal and a maximum value of the second digital signal and a third difference between a minimum value of the first digital signal and a minimum value of the second digital signal, judging whether or not a fourth difference between the second difference and the third difference exceeds a second predetermined value, and determining that compensation would be effective if the fourth difference exceeds the second predetermined value;
• a compensation unit for calculating a compensation value if the fourth difference exceeds the second predetermined value and compensating the stored digital signals stored in the memory based on the compensation value;
• a correlation calculation unit for performing correlation calculation by extracting partial image data groups from the first and second digital signals stored in the memory and determining a maximum correlation level therebetween;
• an interpolation calculation unit for compensating the maximum correlation level by performing an interpolation technique;
• and
• a phase difference detection unit for detecting a shift amount from a reference position of the compensated maximum correlation level.