| 摘要 |
PURPOSE:To eliminate undesired vibration of a lens and to shorten the focusing time, by setting the threshold value of frequency to decide the focusing degree by the presence or absence of a band component higher than the threshold value of frequency and then securing a focusing action having no relation with an object. CONSTITUTION:The light given from an object is formed into an image through a lens 1 and converted into electric signals by an optical converting circuit 2 to be applied to an f1 high band detecting circuit 12 as well as to an f2 high band detecting circuit 23. The high band components corresponding to frequencies f1 and f2 in the signal are detected by the circuits 12 and 23. The positions of front and rear helicoids are recorded to front and rear helicoid position recording circuits 16 and 18 respectively in response to the rise and fall of the high band component. The outputs of the circuits 16 and 18 are averaged by an averaging circuit 27 and applied to a helicoid position setting circuit 29. The circuit 29 is switched to a helicoid shifting circuit 30 by means of a control switching circuit 32, and a lens driving motor 7 is controlled to secure a focusing action having no relation with the object. Thus undesired vibration of the lens 1 is prevented to shorten the focusing time. |
