| 摘要 |
PURPOSE:To make controlling simple and obtain good images by detecting the focal length and aperture value of a camera by detecting means, calculating the depth of field from the values thereof, limiting the extending amount of a helicoid according to said value and stopping the helicoid in a predetermined position when the depth is larger than a fixed value. CONSTITUTION:The camera automatic focusing device is provided with a focal length detector 1, an aperture value detector 2, a helicoid position detector 3, a helicoid driving motor 4, etc. Aperture value and focal length are detected with the detectors 1 and 2 respectively and the depth of field is calculated with a depth of field calculating circuit 5. When the value thereof is smaller than the depth of field critical value A common to the shortest subject distance and an infinite subject distance, the helicoid is driven according to said depth value by way of a helicoid lower limit limiting circuit 6 and upper limit limiting circuit 7, a motor driving circuit 8 and the helicoid driving motor 4. If it is larger than A, a distance measuring device 9 is stopped to fix the helicoid and fix the focus. Thereby, the controlling may be made simple and the image free from out-of-focus may be obtained. |
