Range finder for focusable photographic or cinematographic camera

In a camera having an objective provided with setting means for varying the position of an axially shiftable lens member thereof to focus the objective upon an object within its field of view for projecting an image of said object upon a receiving surface which is part of an intermittently advancing motion-picture film,

• the combination therewith of:
• a pair of ancillary projection systems comprising light-guiding means disposed in part within said objective between said shiftable lens member and said receiving surface for intercepting incident light rays from an object and directing the intercepted light rays over two separate paths away from the objective axis in the form of a first and a second beam, the light-guiding means of at least one of said projection systems including a reflecting peripheral portion of a rotary shutter mechanically independent of said setting means and synchronized with the advance of said film for varying the relative orientation of incident light rays originating at a common point of said object and traveling over said paths;
• photoelectric comparison means illuminable by the light rays traveling over said paths for emitting a coincidence signal whenever two images respectively produced by said beams register with each other to indicate that said projection systems are trained upon the same object;
• drive means coupled with said shutter for displacing same in a succession of rotary sweeps whereby said coincidence signal appears in the form of a short first pulse during each sweep;
• sensing means operatively coupled with said drive means for generating a correlation signal in the form of a short second pulse during each sweep in a predetermined reference position of said shutter in which incident light rays from a point in an object plane conjugate with said receiving surface product registering images on said comparison means;
• and
• phase-detecting means connected to said comparison means and to said sensing means for determining the relative time position of said first and second pulses.

In a camera having an objective provided with setting means for varying the position of an axially shiftable lens member thereof to focus the objective upon an object within its field of view for projecting an image of said object upon a receiving surface,

• the combination therewith of:
• a pair of ancillary projection systems comprising light-guiding means disposed in part within said objective between said shiftable lens member and said receiving surface for intercepting incident light rays from an object and directing the intercepted light rays over two separate paths away from the objective axis in the form of a first and a second beam, the light-guiding means of at least one of said projection systems including a prism with a pair of relatively inclined faces respectively interposed in the paths of said first and second beams, said prism being mechanically independent of said setting means and movable in a direction bisecting the angle included by said faces for varying the relative orientation of incident light rays originating at a common point of said object and traveling over said paths;
• photoelectric comparison means illuminable by the light rays traveling over said paths for emitting a coincidence signal whenever two images respectively produced by said beams register with each other to indicate that said projection systems are trained upon the same object;
• drive means coupled with said movable prism for displacing same in a succession of sweeps whereby said coincidence signal appears in the form of a short first pulse during each sweep;
• sensing means operatively coupled with said drive means for generating a correlation signal in the form of a short second pulse during each sweep in a predetermined reference position of said movable prism in which incident light rays from a point in an object plane conjugate with said receiving surface produce registering images on said comparison means;
• and
• phase-detecting means connected to said comparison means and to said sensing means for determining the relative time position of said first and second pulses.