Motion picture camera with automatic focusing device

Abstract

A motion picture camera provided with an automatic focusing device is arranged to have an image of light emitted from an infrared ray emitting diode projected toward an object to be photographed, and to detect an in-focus state by detecting a peak value of output voltage from a light sensitive element as the direction of the emitted light is varied by a rotatable distance measuring cam. The automatic focusing device is adapted for a zoom lens assembly and is arranged to drive an imaging lens, supported by a shaft which is guided by plate shaped masks at both ends of the lens assembly, in the direction of the lens optical axis. The force for driving the imaging lens is kept low, so that the imaging lens can be accurately adjusted by a rotatable focusing cam during a focusing operation. The rotational position of the distance measuring cam, and that of the focusing cam, are provided in the form of resistance values which vary according to the cam lifts, or in the form of digital codes. When digital codes are employed, distance intervals are established so that the depth of field at each interval overlaps an adjacent interval. Satisfactory focusing thus is provided for all distances within any measured interval.