Fokalsteuereinheit einer Kamera

摘要

To focus a video or disk camera 1, 2, 3, the high frequency detail of the scene is maximized. The camera output is passed through two filters 6, 7 having different pass-bands. The filter outputs are integrated 8, 9, and one is passed to a CPU 11 along with the ratio of the two integrated outputs, and the CPU determines whether the two signals are increasing or decreasing as the lens is moved. The invention exploits the fact that the ratio of the two filter outputs (fig 3) is approximately constant when the camera lens is near the in-focus position whilst the individual outputs (fig 2) have a well-defined peak. The CPU determines if the ratio is unchanging: if it is, the camera is approximately correctly focused and the lens is moved slowly. Otherwise the lens is moved quickly. The direction to move the lens is determined from the individual integrated output. <IMAGE>