JPS6415723A - Automatic focusing device - Google Patents

Abstract

PURPOSE:To improve operability by stopping automatic focusing, not depending on the brightness of an object and its shape to a large extent, in case the automatic focusing is impossible, and automatically and quickly switching operation to an automatic focusing action when the automatic focusing becomes feasible. CONSTITUTION:It is assumed that focus signals outputted from a focus signal forming circuit 16 are sufficiently great and the automatic focusing action is feasible. At that time, an output from a comparator circuit 46 is H, and therefore and output from an AND circuit 50 is L. Since the voltage of a non- inverted input terminal of a comparator circuit 52 is greater than a value that an S/H circuit 54 holds, an output from the comparator circuit 52 becomes H. Consequently, since the input S of an RS-FF56 is L and an input R is H, its output Q becomes L. A display device 58 displays that the automatic focusing is feasible or erases the displayed instructions of manual focusing. A switch 20 is turned off, and a loop for automatic focusing is closed as well; therefore an image pickup element 14 is adjusted to its focus position according to the focus signals.