| 摘要 |
<p>An automatic focusing apparatus includes a circuit (5) for integrating high frequency component of a video signal every field to generate a focus evaluating value; a control unit (2, 3, 6, 7, 8, 9, 11, 12, 13, 14, 30, 110, 131) for moving position of a focusing lens (1) so that the focus evaluating value attains the maximum value; four memories (41 to 44) for respectively storing focus evaluating values of four fields successively supplied from the focus evaluating value generating circuit 5; and four memories (52 to 55) for storing four position data of the focusing lens corresponding to the focus evaluating values. The automatic focusing apparatus further includes a circuit (61) for calculating an amount of change of the focus evaluating value based on the focus evaluating values of the current and second last fields, a circuit (63) for calculating an amount of change of the lens position corresponding thereto, and a circuit (65) for calculating the rate of change of the focus evaluating value based on these amounts of change. The automatic focusing apparatus further includes a circuit (62) for calculating an amount of change of the focus evaluating value based on the focus evaluating values of the last and the third last fields, a circuit (54) for calculating an amount of change of the lens position corresponding thereto, and a circuit (66) for calculating rate of change of the focus evaluating value based on these amounts of change. The automatic focusing apparatus further includes a circuit (67) for comparing the change rates from these two change rate calculating circuits. In response to the comparison output from the change rate comparing circuit, the speed of moving the focusing lens is made lower when the change rate of the focus evaluating value is decreasing than when increasing. <IMAGE></p> |
