| 摘要 |
PURPOSE:To eliminate the time lag up to exposure and take an accurately in-focus picture of a subject which moves at a high speed through the focusing device of a camera, which has a function for fixing a focusing lens at a predetermined fixed position and automatically taking a picture when the subject reaches a focusing position, by previously detecting the motion speed of the subject and predicting the time required for the subject to reach a focus plane set at a specific distance. CONSTITUTION:A range finding device 1 repeatedly output range finding data in constant cycles based upon the output of a line sensor. An arithmetic unit 2 obtains variation in defocusing quantity from the range finding data and calculates the moving speed of the moving subject from the variation and the range finding cycle time. Then variation in the speed is obtained by repetitive range finding operation to predict the speed. The time required for the subject image to reach the focus plane is found from the predicted speed and the quantity of defocusing and then counted down. When the time is counted down to the same value as the time lag of an exposure device, an indication signal for photographing operation is outputted to the exposure device 5. |
