FOCUS CONTROLLING METHOD AND VIDEO CAMERA DEVICE

摘要

An autofocus apparatus is one having at least an estimation-value calculating unit for extracting a horizontal-direction frequency component of a video signal corresponding to a specific image area and supplied from an imaging apparatus for carrying out an autofocus operation of a television camera at high speed, a signal processing unit for calculating a control value used for controlling an image pickup lens drive unit of said imaging apparatus in response to an estimation value calculated by the above estimation-value calculating unit, and an output unit for supplying the control value to said image pickup lens drive unit. The estimation values are calculated while a focus position of an image pickup lens is being shifted. When the estimation value reaches a maximum point of the estimation value, a focal point of the image pickup lens is moved from the position where the estimation value reaches the maximum point to a position located by a distance which is predetermined times as long as focal depth. It is determined which is larger the estimation value obtained at the position to which the lens is shifted or the above maximum value. If it is determined based on the above determination that the above maximum value is larger than the estimation value obtained when the focal point of the image pickup lens is shifted, then the position where the above maximum value is obtained is determined as the focus point. The focus point of the image pickup lens is positionally controlled so as to be agreed with the above focus point. <IMAGE>