| 摘要 |
PURPOSE:To perform high-reliability automatic focusing operation by driving a photographic lens at a low speed when a conversion coefficient which indicates the quantity of driving of the photographic lens to the quantity of unit defocusing of the photographic lens is smaller than a specific value or at a high speed when larger. CONSTITUTION:When it is judged that a distance measurement is reliable, conversion to the number N of encoder pulses is performed on the basis of the conversion coefficient K and the quantity DF of defocusing. When the number N of driving encoder pulses required up to focusing is determined and a high speed flag is set to '1' to drive the motor at the high speed, the number N of encoder pulses is compared with the number NZON of linear zone pulses which is previously set. The NZON is used to decide the switching of the rotating speeds of the motor; when the lens is close to a focusing position and the number N of encoder pulses is smaller than the NZON, the rotating speed of the motor is set to the low speed and when larger than the NZON, the rotating speed of the motor is set to the high speed so as to shorten the driving time of the lens up to the focusing position. |
