An automatic focusing device for cameras, microscopes and the like for automatically adjusting the focal point of a lens with the aid of an operational circuit. The operational circuit derives brightness information of adjacent picture elements, calculates differences in picture element brightness from this brightness information, and aids in the smoothness of brightness change associated with this difference for a number of picture elements. An accumulated value of this smoothness of brightness change is obtained for all picture elements, and the optical system is moved to make the accumulated value a maximum and to adjust the focal point accordingly.

An automatic focus detecting device comprising a photoelectric converting device formed by arranging many elements, a pupil divider capable of forming two object images on the photoelectric converting device through different light paths, a device capable of detecting an in-focus position by processing two image data obtained as output signals from the photoelectric converting device, a device for determining the reciprocal numbers of the output signals obtained by applying a uniform light onto the photoelectric converting device and a device for receiving the image data to correct the signals for output multiplying the image data by these reciprocal numbers in order to enable accurate focusing. The photoelectric converting device is so arranged as to receive the light having passed through an infrared cut filter or a band pass filter.

An automatic focus adjusting device comprises a charge accumulating type photoelectric conversion element array, a circuit for outputting from the output of the photoelectric conversion element array a signal indicative of the in-focus state of the image of an object to be photographed on a film surface, a circuit for modifying the newest detection signal on the basis of at least one past detection signal and outputting out a modification signal, a circuit for selecting one of the detection signal and the modification signal in accordance with the brightness of the object to be photographed, and a circuit for driving a picture-taking lens in a direction in which the image of the object to be photographed is focused on the film surface, on the basis of the signal selected by the selecting circuit.

A range finder wherein the quantization of analog outputs from light receptor elements for converting an optical image into an electrical signal is accomplished by comparing the outputs from at least two of the light receptor elements in each group, by dividing the outputs into the following three cases: one output is greater than the other; both are equal; and one is smaller than the other.

Apparatus for detecting displacement of optical image is disclosed which comprises a photosensitive element array, a first circuit, a second circuit and a phase difference measuring circuit. The photosensitive element array is composed of a number of photosensitive elements disposed on and near the focal plane of an image forming optical system through which an optical image is formed. The first circuit multiplies the electric outputs from photosensitive elements in the array by vectors whose phases sequentially increase or decrease, and then adds the products together to form an added output. The second circuit multiplies the electric outputs from photosensitive elements slightly shifted from the above elements in the same array, and then adds the products together to form a second added output. The difference in phase between the first and second added outputs is measured by the phase difference measuring circuit.