| 摘要 |
PURPOSE:To adjust a focus automatically without providing any optical system, etc., for focusing point detection separately by comparing the values of sharpness of the same position of a subject which are obtained at two positions in an optical-axis direction and obtaining information on the direction of a focusing point and the rough length of the movement of the lens. CONSTITUTION:A differential waveform is obtained by a differentiator 41 from an obtained image signal and this output is applied to a maximum value holding circuit 42 and a minimum value holding circuit 43, so that a subtracter 44 calculates their output difference as sharpness. When a focusing point is found, a CCD line sensor 17 is placed in the center of a scanning range and the lens is placed nearby the focusing point to find sharpness, which is written in a RAM 50. Then, the lens is moved up or down by specific length and sharpness is found by the same method and compared with the last sharpness to find the direction and rough length of the movement of the lens for obtaining the focusing point, thereby moving the lens. Then, the same operation is repeating. When the difference in sharpness becomes smaller than a specific value, the position is regarded as the focusing point. |
