FOCUS DETECTOR

PROBLEM TO BE SOLVED: To provide a focus detector for determining whether a focus detection can be performed with high reliability even in the case of the exceedingly defocused state, and also, when the contrast of an object is low. SOLUTION: Signals of a 1st image and a 2nd image formed with a base length are outputted by an AF sensor 25. The combination of high coincidence is obtained by a controller 35 while changing the relative distance between a block cut out of the 1st image and a block cut out of the 2nd image based on the output of the AF sensor 25, and the correlation value of the combination with the highest coincidence is calculated. Besides, whether the 1st or the 2nd image is a low-frequency image or not is determined. When the image is the low-frequency image, a determination value requiring the reliability higher than that when the image is not the low-frequency one is set, and then, whether the focus detection is enabled or not is determined by comparing the determination value with the correlation value, and only when the focus detection is enabled, the deviation of a photographing lens from the focal position is detected. COPYRIGHT: (C)2006,JPO&NCIPI