| 摘要 |
PURPOSE:To decrease the number of times of calculation in correlation calculation by driving a lens to nearby a focusing point, calculating correlation and finding the picture element position of a minimum correlation quantity, and finding a defocusing quantity from it. CONSTITUTION:New light from a subject is picked up by a reference and a comparison picture element part at the same time after a movable lens is moved to nearby the focusing point. Pieces of density information on the subject which are obtained by those picture element parts are fetched into specific locations of the memory means 69 of a control part 49. Then those pieces of density information are contrasted with each other by a comparing means 65 to calculate the correlation. Further, an arithmetic means 67 finds the defocusing quantity from the difference between a picture element position on, for example, the other end side in a picture element area where the correlation calculation result indicates a minimum value and a focusing picture element position which indicates the focusing position in a comparison picture element part. Consequently, even when the density information of the comparison picture element part is reduced, the picture element position of the minimum correlation quantity is accurately found. Further, the processing time for the correlation calculation and minimum value selection can be shortened. |
