| 摘要 |
PURPOSE:To realize high-speed and highly precise focusing while maintaining simple configuration by selecting and switching either a range made to limit to arithmetic operation for calculating the DCT coefficient of a frequency domain or the range in which this limitation is not executed. CONSTITUTION:AF control based on an obtained transformation coefficient is executed by using a feature that a coefficient value is small both in the case that a lens position is at approximately infinite distance and the in the case that it is at the closest distance, and the coefficient value shows a peak at a focusing position. The AF control is executed in this way by using an increasing and decreasing variation of the transformation coefficient value, but if the area of the coefficient to be used for the AF control is fixed, and the AC transformation coefficient of only a part to be used is determined by DCT (discrete cosine transformation) operation, focusing speed is improved. For instance, if the transformation coefficient of only a hatched part area (to show frequency domain) is used for the AF control, the DCT operation can be finished only with that of the hatched part. Namely, in this case, the range of either the DCT operation of an AF area part or the DCT operation of compression recording can be switched. |
