GB639612A - Improvements in or relating to means for causing relative axial movements of nested tubes - Google Patents

Abstract

639,612. Optical systems. WATSON & SONS, Ltd., W., and WAITT, H. Nov. 3, 1947, No. 29322. [Class 97 (i)] [Also in Group XXIV] An optical system comprises two concentric relatively axially movable nested tubes, two lenses carried by the two tubes at opposite ends thereof respectively and on a common optical axis, a fixed support tube outside and concentric with the two movable tubes, two further lenses carried by the support tube and outside the first-mentioned lenses, a projection from one of the movable tubes extending radially through a longitudinal slot in the wall of the other movable tube into guiding engagement with a guide slot in the support tube, a projection from the other movable tube at a position diametrically opposed to the first projection and extending radially into guiding engagement with a second guide slot in the support tube, the guide slots extending in the axial direction of the system and the engagement of the projections with the slots limiting rotational movement of the movable tubes about the axis of the system, and cam means rotatable as a unit about the axis of the system and engaging, or engageable with, the two projections to effect, on rotation of the cam means, differential movements of the two projections and the tubes connected thereto in the axial direction relative to the support tube. The variable magnification system shown is for use with a kinematograph camera 17 and comprises an attachment 8 which is removably mounted on the front of said camera by means described in Specification 639,610. The attachment includes two lenses 13, 16 mounted on a body tube 7 as described in Specification 639,611 and two lenses 18, 19 which are respectively mounted in cells 20, 21 carried by telescoping tubes 23, 22. Pins 26, 27 extend radially outwards from the tubes 23, 22 on opposite sides of their axis and carry feathers 39, 40 engaging curved cam slots 28, 29 in a tube 30 which is partially rotatable around the body tube 7. Rotation of the tubes 22, 23 is prevented by two longitudinal slots 31, 32 in the body tube 7, which slots are engaged by feathers 33, 34 carried. on the pins 26, 27 respectively. A clearance slot 35 is formed in the tube 23 to prevent restriction of the movement of the pin 27 which passes therethrough; a clearance slot 38 is also provided in tube 22 to receive pin 26. A cover tube 37 provided with a handle is fitted to the tube 30 to project the pins 26, 27 and slots 28, 29.