Control method for an auto focus apparatus

A control method for an auto focus apparatus whereby the output data of a charge accumulation type sensor is processed and a defocus amount indicative of the amount and direction of the deviation from the actual focus position to an in-focus position is calculated by calculation means, and a photo-taking lens is driven to the in-focus position by driving means under servo control in accordance with said defocus amount, comprising the steps of:

• successively detecting the actual amount of movement of said photo-taking lens by lens movement amount detecting means;
• effecting the accumulation by said charge accumulation type sensor in an overlapping manner even while said driving means drives said photo-taking lens toward the in-focus position, and correcting a crude defocus amount said calculation means has calculated from the output of said charge accumulation type sensor by the amount of movement of the lens detected by said lens movement amount detecting means after the accumulation by said charge accumulation type sensor, thereby obtaining a corrected defocus amount;
• using said corrected defocus amount for the control of the next driving of the photo-taking lens, and controlling the accumulation by said charge accumulation type sensor and the driving under servo control so as to be effected successively in an overlapping manner;
• and
• judging whether said photo-taking lens is in the in-focus state;
• wherein said judgment is not done when the amount of lens driving during the time from the start of the accumulation by said charge accumulation type sensor till the calculation of the defocus amount is greater than a predetermined threshold value.

A control method for an auto focus apparatus whereby the output data of a charge accumulation type sensor is processed and a defocus amount indicative of the amount and direction of the deviation from the actual focus position to an in-focus position is calculated by calculation means, and a photo-taking lens is driven to the in-focus position by driving means under servo control in accordance with said defocus amount, comprising the steps of:

• successively detecting the actual amount of movement of said photo-taking lens by lens movement amount detecting means;
• effecting the accumulation by said charge accumulation type sensor in an overlapping manner even while said driving means drives said photo-taking lens toward the in-focus position, and correcting a crude defocus amount said calculation means has calculated from the output of said charge accumulation type sensor by the amount of movement of the lens detected by said lens movement amount detecting means after the accumulation by said charge accumulation type sensor, thereby obtaining a corrected defocus amount;
• using said corrected defocus amount for the control of the next driving of the photo-taking lens, and controlling the accumulation by said charge accumulation type sensor and the driving under servo control so as to be effected successively in an overlapping manner;
• and
• judging whether said photo-taking lens is in the in-focus state;
• wherein said judgment is not done when the amount of lens driving during the time from a certain point of time in the course of the accumulation by said charge accumulation type sensor till the calculation of the defocus amount is greater than a predetermined threshold value.