GB895336A - Scale-reading device for measuring scales - Google Patents

Abstract

895,336. Scale reading devices. HENSOLDT & SOHNE, OPTISCHE WERKE A.G., M. July 4, 1960 [July 17, 1959; Feb. 11, 1960], No. 23222/60. Class 97(1). A scale reading device, wherein one scale graduation mark is projected into a reading window and means are provided for bring- ing the image thus formed into coincidence with an index mark(s) on said window, is characterized in that the projection means comprise a two-part objective of which the first part is arranged at a distance from the scale equal to its focal length and is displaceable by means of a screw relative to the second part and parallel to the measuring scale and in that the first part and the measuring screw are connected to scales appearing in the reading window. In the device shown in Figs. 3, 4, an image of a graduation line M on a scale 4 is formed by means of an objective 2, 3 and reflectors 8, 9, 13, 14 in the plane of a viewing window 15; the scale is illuminated by a lamp 10. Part 3 of the objective is fixed but part 2 is slidable in a guide 6 and is positioned with its focal point in the plane of scale 4 and its nodal point K in the plane of the guide. The movement of the line 2 is achieved against the force of spring 7 by rotation of screw 20 which causes a nut 21, a screw 20 of which is guided in a guide-way 23, to move, and by rotating a lever 28 about a pin 27 causes the block 6 supporting objective 2 to be moved also. A scale 17 fixed to the block 5 and a scale on a drum 24 attached to screw 20, are also moved by corresponding amounts and at least a part of each of these scales is visible in the window 15 to indicate scale intervals of for example millimetres and 1/100 millimetres. All three scales have corresponding reference marks on the window 15. The guideway 23 may be rotated in a plane perpendicular to the plane of the Figures to compensate for errors in the pitch of screw 23. A subsidiary prism may be positioned between the objective part 2 and the scale 4 to bend the light path. Moreover, part 2 of the objective together with prism 8 and mirror 9 may be positioned in an extension so that the objective 2 is positioned to the left of the housing 1 as shown in Fig. 3. In the embodiment showing this a series of rotatable rods are arranged between the nut 21 and the block 5 to effect movement thereof.