A device for detecting coincident focusing points for use in the controlling of the focusing of an automatically focusable lens comprises a single array of light receiving transducers for converting the distribution of light intensity of an image applied thereon to a set of corresponding electrical signals. The image applied to the array is from a first optical path from an object through the lens and from a second optical path from the object. At least one shutter is provided for cutting off one of the optical paths to alternatively effect the application of light from the one optical path on to the array to produce a first set of signals and thereafter the light from either the other optical path or the sum of the two optical paths on to the array to produce a second set of signals. The first set of signals are processed to produce a third set of signals which correspond to the ratio of each signal therein with respect to another of the signals and the second set of signals is processed to obtain a fourth set of signals corresponding to the ratio of each signal with respect to another of the signals. The third and fourth sets of signals, for each transducer, are compared and a signal is produced when a favorable comparison is obtained.