Patent GB-1027142-A (GB)
Title: Improvements in and relating to focusing mechanisms in photographic cameras
IPC: G03B3/00
Filed: 1963-07-25
Abstract: 1,027,142. Cameras. INTERNATIONAL POLAROID CORPORATION. July 25,1963 [Aug.3, 1962], No.29539/63. Heading G2A. Continuous focusing between a lens mounted on a lens board and the camera body is effected by a linkage between the said board and the said body. In the form shown, the camera body 10 is connected to the lens and shutter housing 14 by upper and lower linkage systems 18, 19 respectively. First linkage system 18 comprises a link 22 pivoted at one end to a bar 40 on housing 14, and slidably mounted at the other end by a pin 50 engaging in a slot 51 in body 10. Another link 20 is pivoted at one end to link 22 by a pin 32, and pivoted at the other end to a casing 31 on housing 10 which supports the release button 30. Second linkage system 19 comprises a link 24 pivoted at one end to bar 40 and having at the other end a pin 44 slidably engaged in a slot 46 in body 10. Another link 26 is pivoted at one end to the body 10 by a pin 34 and has at the other end a pin 36 slidably engaged in a slot 38 in housing 14. Links 24, 26 are pivoted together intermediately by a pin 48. Two tubular bars 40, 42 extend fixedly between the two linkage systems, bar 40 passing freely through housing 14. Pins 32 and 48 are not at the mid-point between the end connections of the links, so that the ends of the links on the camera body 10 are farther apart than the opposite ends on the lens housing 14. This asymmetrical arrangement allows housing 14 to be moved past bar 42 when the camera is being folded up, so providing a more compact retracted position. The rigidity imparted to the system by bars 40,42 is sufficient to maintain the lens board in registration with the film plane of the camera, without movement of the optical axis, as it is opened or closed. This rigidity of the linkage system is utilised to effect focusing adjustment by additional movement of the linkage. A movable member 52 is slidably mounted on camera body 10 by slot-andpin means 54, 58 and 56, 60. The member 52 has an integral projection 62 at one end, and another projection 64 pivoted to it at the other end by a pin 66. A lever 68 is pivoted on member 52 by a pin 70, and biased anticlockwise. When the camera is opened, pin 50 slides down slot 51, pushing past lever 68, which then swings back behind pin 50 (position of Fig. 6). Pin 50 is now latched to member 52, so that as the latter moves in the direction of its length (i.e. perpendicular to the optical axis) this movement is transmitted to the linkage to alter thedisance between lens and film plane for focusing adjustments. To close the camera, projection 64 is manually rotated, which engages with lever 68 and disengages it from pin 50, leaving the latter free to slide back up slot 51 as housing 14 is pushed back to its retracted position. Fig. 7 (not shown) is an alternative arrangement of connecting the movable member with the linkage to effect focusing adjustment. The focusing movement of member 52 can also be connected to a rangefinder system. This comprises a fixed half-silvered mirror 78. A rotatable mirror 80 on a base portion 82 pivoted at 84 to the camera body 10 is biased into contact with a cam surface 90 of member 52. Thus linear movement of member 52, besides being translated into focusing movement, is also translated into rotational movement of mirror 80. Thus the measuring beam of the rangefinder system is deflected in accordance with focusing movement of the lens.