Patent US 4,967,280

In a video camera having an automatic focusing function, a focus evaluating value is calculated as the sum of first and second focus evaluating values extracted using output of two filters having different cut-off frequencies, and a relative ratio of the first and second focus evaluating value is also calculated. This relative ratio is compared with a predetermined reference value. Considering a case in which the focus evaluating value is below this reference value after an object is brought into focus, even if the focus evaluating value does not change, an auto-focus operation is resumed. On the other hand, considering a case in which the relative ratio is above the reference value, even if the focus evaluating value changes, the auto-focus operation is not resumed. In addition, even if the focus evaluating value reaches a maximum in the auto-focus operation, the auto-focus operation is not terminated if the relative ratio does not reach a predetermined reference value. Furthermore, the amount of slight movement of a lens in an object change confirming operation after bringing the object into focus is switched depending on the relative ratio. Additionally, it is determined whether or not the lens correctly moves toward an in-focus position by determining the increase or decrease of the relative ratio.