GB810820A - Reading device for measuring scales - Google Patents

Abstract

810,820. Optical scale reading device. HENSOLDT & SOHNE, OPTISCHE WERKE A.G., M. Jan. 10, 1957 [Jan. 14, 1956], No. 1068/57. Class 97(1) A device for reading a coarse scale having divisions which are double lines is movable relative to the scale and comprises opticalelements for imaging at least one division of the scale in a scale reading window, a fine scale, having a division of single lines and mounted to appear in said window, means for moving the fine scale relative to the image on the coarse scale, a further rotatable scale mounted to appear in the reading window and connected with the means for moving the fine scale, and a fixed index arranged to give on the rotatable scale the amount of movement of the fine scale. In the form shown, an image of a coarse scale 1 is formed by a lens 3 and projected by mirrors 4, 5, 5a and 6 on to a scale reading window 7, the scale 1 being illuminated by lamp 8 and mirror 10. Window 7 is rotatable by a ring 12, mounting a magnifier 18 and connected through a pin 16 and eccentric 13 to a fine scale 14 so that the latter is linearly displaced as window 7 is rotated. This window has mounted thereon an annular scale 11 readable against an index 19 on a fixed mask 21 having apertures through which scales 1, 14 and 11 are visible. In use, window 7 is rotated until one of the graduations of fine scale 14 lies between a double line of the coarse scale 1, the scale 11 giving the amount of such rotation. Specification 643,590 is referred to.