Improvements in or relating to Synoptophores

1,157,447. Synoptophores. ALBERT OPTICAL CO. Ltd. Sept.14, 1966 [Sept. 14, 1965], No.39272/65. Heading G2J. In a synoptophore having optical tubes through which a patient views a pair of targets and a mechanism for controlling the angular movement of the tubes in a horizontal plane, the control mechanism comprises two platforms 38, 39, which can move towards or away from one another on guide tubes 40, 41, to allow for varying pupillary distances, each platform having a spindle on which one of the optical tubes is pivoted, the axis of each spindle being aligned with the approximate centre of rotation of an eye, and a differential mechanism coupling the optical tubes and having locking means so that when the differential mechanism is unlocked the optical tubes are allowed independent angular rotation and when the differential mechanism is locked the tubes are allowed to move in unison with a predetermined angle between them, the predetermined angle being capable of variation. As shown, a pair of gear segments 1, 2, are pivoted on platforms 38, 39 and are rigid with the optical tubes (not shown). Each segment 1, 2, is engaged with one of a pair of racks 3, 4, pivoted at 13, 14, to members 15, 16, which are slidable on rods 17, 18, protruding from a member 19. A pinion 24, engaged with a rack 23, can be coupled to a dial member (29, Fig. 2, not shown) by a dog clutch (30) the arrangement being such that when it is so coupled the rack 23 can only be moved by rotating the dial member, but when it is uncoupled the rack 23 can move freely. The rack 23 has an extension 21 slidable on a rod 22 and pivoted at 20 to the member 19, a spigot 26 on the extension 21 passing through a slot 25 in member 19 and having a locking mechanism 27 thereon to fix the relative angular positions of member 19 and extension 21. Several modes of operation are thus possible viz (1) locking device 27 is released and dog clutch (30) disengaged so that rack 23 can move freely. Either optical tube may be locked in position by means, not shown, and the other optical tube moved freely, the appropriate drum 11 or 12 then giving an angular reading of the segment 1 or 2; (2) locking device 27 is engaged so that movement of one optical tube (say segment 1) causes movement of the corresponding rack 3 and, through members 15-19 acting as a rigid bar, similar movement of the other rack 4 and thus equal but opposite rotation of the second optical tube; (3) locking device 27 is engaged and dog clutch (3