Focus detection apparatus for camera

In a focus detection apparatus for detecting an in-focus position of a photographing lens on the basis of a phase difference between image signals produced from at least two focusing portions of an image sensor for focusing an object image, said image sensor being scanned at least two times to produce first image signals corresponding to said object image from a first scanning cycle and second image signals corresponding to said object image from a second scanning cycle of said image sensor,

• the improvement comprising:
• detecting means for detecting maximum and minimum values of said first image signals produced from said at least two focusing portions obtained in a first scanning cycle of said image sensor;
• signal converting means for converting signal components of said second image signals falling within a range of the maximum and minimum values detected by said detecting means into digital signals, said second image signals and said signal components being obtained in a second scanning cycle of said image sensor;
• calculating means responsive to the digital signal output from said signal converting means for calculating the in-focus position of the photographing lens based on a phase difference between the image signals produced from said two focusing portions of said image sensor in said second scanning cycle;
• and
• means responsive to said calculating means for focusing said photographing lens to said in-focus position to thereby focus said object image.