Patent GB-707139-A (GB)
Title: Improvements in, and relating to, twin-lens photographic cameras
IPC: G03B17/12
Filed: 1950-09-08
Abstract: 707,139. Lens fittings for photographic cameras. HEIDECKE, R., [trading as FRANKE & HEIDECKE]. Sept. 8, 1950 [Sept. 9, 1949], No. 22199/50 Classes 97 (1) and 98(1) In a twin lens camera having finding and taking objectives and having holding means at the front of the camera for mounting on or locating in front of the camera lenses a pair of interconnected supplementary or one of'a movable series of pairs of such lenses, one lens of the pair or of each pair having combined or co-operating therewith a wedge for parallax compensation, the holding means is constructed so as to locate that one of the pair or of a pair of supplementary lenses with which the wedge is combined or co-operated in front of the camera finding lens when the other one of said pair of supplementary lenses is mounted in a predetermined angular position on or is moved to a position in front of the camera taking lens. As shown, mounts 8, 12 of supplementary lenses for a twin lens camera are hinged together at 10, the mount 12 containing a combined lens and parallax correcting wedge 13. Each of the camera lenses 3, 5 is provided with identical sets of three equally spaced bayonet latches 4, 6 for the reception alternately of a single optical unit such as a telephoto lens for focusing and taking, while only the mount 8 has bayonet sockets, the mount 12 having instead a collar engaging the exterior of the bayonet latch when placed on the camera lens. The mount 8 is also provided with bayonet latches on its outer face for receiving further attachments, the mount 12 being recessed to allow a further similar mount to rest on to it and to locate the latches on the mount 8 when the two mounts are folded together. When the mount 8 is secured to the lens 3 an arm 14 on the mount 12 engaging the lens board 2 prevents movement of the centre of gravity of the mount beyond the pivot 10 so that the mount rests against the lens 5. If however the mount 8 is attached to the lens 5, the mount 12 stands clear of the lens 3, extending either vertically above the lens 5 or to either side of the lens 3 due to the arrangement of the latches 6 and the sockets on the mount 8 thereby indicating the incorrect attachment of the unit: As a modification, the hinge 10 is reversed so that the mount 12 covers the bayonet sockets on the mount 8, so that the unit must be opened before it can be attached to the camera. In a further embodiment, identical pairs of lenses 15, 16, 17 are carried on diameters of a disc 18 rotatably mounted on a shaft 28 in line with the camera lenses, and a second similarly disposed disc 19 fixed on the shaft 28 carries pairs of elements comprising parallax-correcting wedges 21, 22, 23 and apertures 20. The wedge is placed in front of the viewing lens 5 and by means of a 1:2 gear train 24 ... 27 the same wedge is always located in front of the lens 5 no matter which of the pair of supplementary lenses is so positioned. In an alternative form of this embodiment the disc 19 is replaced by a pair of contra-rotating wedges driven by gearing from the shaft of the disc 18. A differential may be included in the drive to the wedges so that they may also be adjusted in synchronism with the focusing of the camera.