Automatic focusing device for use in a camera

Claim 1

An automatic focusing system for use in a camera comprising: means for succesively driving an objective lens of said camera along its optical axis; means for repeatedly detecting a focusing condition of the objective lens during the movement of the objective lens to produce a direction signal which represents a defocus direction of the objective lens with respect to a predetermined image plane, and an amount signal which represents an amount of defocus of the objective lens; means for producing a predetermined signal which represents a predetermined amount of defocus of the objective lens; means for comparing said amount signal with said predetermined signal to produce a comparison signal which represents the compared result; means for monitoring the amount of axial movement of the objective lens between successive detections to produce a lens moving amount signal which represents the monitored amount; and means for controlling said driving means in accordance with said direction signal, said amount signal, said comparison signal, and said lens moving amount signal, said controlling means controlling said driving means in accordance with said direction signal when said comparison signal indicates that the amount of defocus represented by said amount signal is larger than said predetermined amount of defocus represented by said predetermined signal, and said controlling means controlling said driving means in accordance with said direction signal, said amount signal and said lens moving amount signal when said comparison signal represents that the amount of defocus is smaller than said predetermined amount.