| 摘要 |
PURPOSE:To provide a device which can enjoy high efficiency at a low cost by using a pair of masks and photoelectric elements. CONSTITUTION:In the vicinity of the focal points of objective lenses 10 and 20 having parallel optical axes 11 and 21, there are arranged light receiving elements 12 and 22 having similar light receiving planes, in front of which are optically equivalently arranged masks 14 and 24 having a plurality of slits 31. In responsed to the change in the focal length (or range adjustment and focal adjustment) in a taking lens, the objective lens 20 is moved in the direction of arrow A, or a total reflecting prism 23 is turned in the direction of arrow B thereby to deflect the optical path of the light which is incident upon the element 22. The focal point is detected at the point where the outputs of the elements 12 and 22 at that time becomes identical. Thus, since it is sufficient to use only two elements, the production cost is lowered. Since no incident light is not divided, the quantity of incidence can be made sufficient to enhance the sensitivity. |
