Automatic focusing device using phase difference detection

Abstract

In a still video camera or the like which employs a solid-state image sensor, such as a CCD, a first calculation of the amount of correlation in an AF sensor is executed by using a smaller number of pixels and a larger amount of shifting, and second and subsequent calculations of the amount of correlation are executed by using a larger number of pixels and a smaller amount of shifting. Accordingly, it is possible to reliably detect a large-defocus state through the first calculation, whereby it is possible to omit an unnecessary calculation to reduce the required calculation time. The automatic focusing device uses a phase difference detection method in which a focus state is detected by detecting the deviation between two incident images. The device includes two sensor portions for receiving two images which are each a variable in their image forming portions according to a focus state. The device also includes a correlation computing device for computing the correlation between signals from the two sensor portions by relatively shifting the output signals with a predetermined pitch. The device also includes a driver for driving a focus lens to the in-focus point according to the outputs of the computing device and also includes a control for changing the predetermined pitch with which the output signals of the two sensor portions are shifted.