An automatic focusing method is disclosed with which a plurality of selected objects can be held within the focusing range of the photographing lens of a camera. For each of object for which it is desired to keep within the focusing range, a focusing detection operation is carried out to provide defocusing data for the object. A weighted mean value of the defocusing data is employed as a common focal position.

A camera having an automatic focusing device, capable of automatically driving a lens to a shooting lens position where it can simultaneously focus different objects on different positions. The camera has a focus detection circuit capable of detecting focusing positions where the lens is focused on the respective objects. When one of the focusing positions is beyond the limit of drive of the lens, the driving to the shooting lens position is judged to be impossible and the control for driving the lens to the shooting lens position is prohibited.

An improved method and apparatus for optimally focusing an image at a focal plane of a plurality of subjects located at substantially different distances from an image-forming adjustable focus lens system of the type that is responsive to a rangefinder derived signal, where the rangefinder is one that normally generates a subject distance signal representative of the distance to the nearest of a plurality of different distance subjects. Improved focusing is achieved by generating a composite signal representative of the relative size of each of the plurality of subjects and their distance from the rangefinder and then comparing this composite signal with that of the above-mentioned nearest subject distance signal. A signal representative of the degree of deviation of these signals from one another is then employed to optimally focus an image of the plurality of different distance subjects at the lens system focal plane.

A range finding device and method for determining the distance between a merged submarine and a target above the surface having a first and second periscopes mounted on a submarine with a known separation. These periscopes are rotatable and extensible above the surface and can determine the bearing from each of the periscopes to the target. A computer receives the bearings from the first and second periscopes and uses the bearings with the known preset distance between the periscopes to calculate the distance between the submarine and the target.

A distance measuring technology capable of stably and accurately performing distance measurement of an object without any highly accurate focus control mechanism is provided. A distance measuring apparatus has a mask for restricting light so as to pass through two or more different light passing positions; a lens system for focusing the light passed through the mask; an image taking-in means for taking in images from the light focused by the lens system; and a distance calculating means for calculating a distance from an imaging element to an object using the taken-in images. The mask restricts the light so as to pass through only specified positions.