| 摘要 |
PURPOSE:To allow a lens to coincide with the position of the image surface of an object by using the functional formula of low degree while the number of focus detecting action cycles is small so that correction is performed and switching to the functional formula of high degree according as the number of focus detecting action cycles increases. CONSTITUTION:By turning on an AF starting switch, defocusing quantity DF1 which does not show a focus detecting action is obtained at t1 and a lens is driven by DL1(DL1=DF1), so that the lens reaches l2. By performing a second focus detecting action at t2, DF2 is obtained and driving quantity DL2 is calculated with the approximation of the first degree, then the lens is driven to reach l3. Thereafter, by performing a 3rd focus detecting action at t3, defocusing quantity DF3 is obtained and DL3 is obtained with the approximate formula of the function of the second degree, then the lens is driven to l4. Thus, the lens is driven so that the position of the image surface of the object coincides with the position of the lens in a short time after starting a 1st focus detecting action cycle. |
