<title>Continuous focusing of moving objects using DFD1F</title>

Abstract

A method is presented for continuous focusing of moving objects. It is based on DFD1F [20] which is a method for determining distance of stationary objects using image defocus information. The proposed method requires recording of two images of a moving object with different degrees ofblur. The change in blur is caused by varying camera parameters such as lens position, focal length, and aperture diameter of the recording camera. The two images must be recorded simultaneously in a short time period. A new camera structure is proposed for such recording of the images. In the proposed method, the requirement of a large memory space has been avoided for storing the MTF data of the camera's optical system. This is achieved by using a parameterization scheme for the MTF data. The method has been implemented on an actual camera system. Experimental results on this system indicate that the method yields an RMS error in focusing of about 4.3% in lens position. The image blur caused by a focusing error of this magnitude is barely noticeable by humans. Therefore, in addition to machine vision, the method has practical applications in video cameras such as camcorders.