| 摘要 |
<p>A focus detecting system includes first and second lens devices for forming first and second auxiliary images of an object on first and second detector devices, respectively. Each detector device includes a plurality of linearly displaced light responsive elements. One of the lens devices is movable with respect to its associated detector device to shift the light distribution pattern of the corresponding auxiliary image in the direction of linear displacement of the light responsive elements. The movable lens device is so coupled to a movable objective lens, which focusses a principal image of the object on a light sensitive film, that when the principal image is in focus, the light distribution patterns of the first and second images will be correspondingly positioned with respect to the first and second detector devices, respectively. A reference signal of a predetermined frequency controls a switching circuit to compare the electrical signals from the light responsive elements in the first detector device, alternately, at the predetermined frequency of the reference signal, with electrical signals provided by first and second predetermined groups of the light responsive elements in the second detector array. Signals are thereby provided which are processed and phase detected to provide an output signal representative of the direction that the objective lens is displaced from a focus position at which the principal image is in sharpest focus.</p> |
