IMAGE FOCUS DECTECTING METHOD AND DEVICE USING DYINAMIC THRESHOLDING METHOD

摘要

A device and a method for detecting a focus of an image are provided to adjust a focus of camera by calculating a focal distance from an inputted image to a subject in real time without an additional focus control device or a burden of large calculation. A camera(110) takes a photograph of a subject by selecting an accurate focal distance to the subject among unaccurate focal distances while a position of a lens is changing to the subject. An image signal processing circuit(120) processes each image signal photographed from the camera according to the various focal distances to generate digital image frame signals of the subject and a focal distance signal according to each frame signal. A dynamic thresholding circuit(130) processes dynamic thresholding to image frames inputted from the image signal processing circuit to obtain images to which dynamic thresholding is applied. A pixel calculator(140) counts the number of pixels of images processed by dynamic thresholding. A motor driving unit(150) adjusts the position of the lens for controlling the focal distance. A focal distance controller(160) transmits a control signal for a motor to the motor driving unit by considering a pixel number signal of each image frame transmitted from the pixel calculator and a focal distance signal corresponding to each image frame transmitted from the image signal processing circuit.