Patent GB-453221-A (GB)
Title: Double lens system
IPC: G02B27/14
Filed: 1934-12-05
Abstract: 453,221. Lens mounts ; colour photography. THOMAS, R., and BRYAN, W. J., Richfield Building, Los Angeles, U.S.A. Dec. 5, 1934, No. 34979. Convention date, Dec. 5, 1933. [Class 97 (i)] In a double-lens system for producing complementary pairs of adjacent images in colour photography, or for projecting such images, in order to avoid parallax between the two images when the lenses are moved axially for focusing, each lens is divided into front and rear components and the front components are so mounted that their axial movement is accompanied by lateral movement towards or away from each other, the rear components being moved only in the axial direction. As shown in Fig. 4, the mounting comprises a member 54<1> secured to the wall 17 of the camera and having an externally - threaded projection 59 engaged by a rotatable member 60. The member 60 is internally threaded and engages external threads on the member 63 which carries the two lens systems which consist of rear components 75, 76 and front components 101, 102, and 103, 104. The threads on the member 63 have a different pitch from those on the projection 59, so that rotation of the adjusting- member 60 causes the member 63 to be moved axially for focusing, rotation of this member being prevented by keys 64. An opaque septum consisting of a pair of contiguous strips 140, 141 extends between the two lens systems. The lenses 75, 76 are carried by a support 71 which is fixed within the mount 63, while the supports 106, 107 carrying the lenses 101 .. 104 are arranged to be displaceable towards or away from the axis of the mounting, this displacement taking place simultaneously with the axial focusing-movement. For this purpose the supports 106, 107 are provided with cam grooves 125, 126 into which pass pins 120, 121 carried by the rotatable member 60 and passing through slots 122, 123 in the mount 63. The supports 106, 107 are guided radially by engagement of their edges with fixed members 112 and are maintained in contact with the pins 120, 121 by spring plungers 130 .. 133 bearing against the septum leaves 140, 141. Between the front and the rear components of the lenses is an adjustable diaphragm comprising two plates 78, Fig. 7, movable in guides 77 and each provided with slots 80, 81. These plates can be moved towards or away from each other to vary the size of the apertures bounded by the slots by a rotatable ring 84, within the mount 63, having pins 87 extending into spiral slots 86 in the plates, this ring being connected to an external adjusting-ring 93 by a pin 89. In a modification, instead of moving the front lens components laterally, parallax is avoided by the use of prisms which move axially relatively to the lenses when the latter are moved for focusing. In Fig. 11 each lens system is associated with a pair of prisms 210, 215, the prisms 210 being mounted in the lens barrel 204 so as to move axially with the lenses, while the prisms 215 are secured in the fixed support 216. The prisms 210 are arranged apex to apex and the prisms 215 base to base, or vice versa. Specification 322,801, [Class 97 (i)], is referred to.