GB635170A - Improvements in or relating to light-beam indicating systems - Google Patents

Abstract

635,170. Indicating-apparatus. STANDARD TELEPHONES & CABLES, Ltd., and FELDHUSEN, I. V. Nov. 5, 1947, No. 29498. [Class 106 (iv)] [Also in Group XX] A light-beam system for indicating on a screen angular deflections of a rotational system comprises a collimating system including a transparent representation of a measuring scale, a deflecting mirror mounted on the rotational system and rotating with it, and an auxiliary reflector for directing the beam after reflection from the deflecting mirror on to a fixed screen bearing a fiduciary mark. A reflecting galvanometer 5 is mounted in a housing 1 having in its front face 2 a window 3 into which is let a ground-glass screen 4 with a fiduciary line thereon. A light concave mirror 7 is supported on the suspension for the moving system of the galvanometer 5 and rotates in front of a glass window 8. A collimator system comprises a lamp-housing 9 with lamp 10, and a lens tube 12 sliding on the housing 9 and carrying a condenser lens 13. An extension rod 14 attached to the tube 12 carries 'a holder for transparent member 16 on which is engraved a reduced scale. Alternatively, the member 16 may be fixed on the lens tube 12 just in front of the lens. The lamp 10 is connected to a battery or transformer which may be fltted inside the housing 1. Mounted on a pillar 20 is a slidable bracket 21 currying a Mangin reflector 22 preferably attached by a universal joint and facing both mirror 7 and screen 4. The whole collimator system may be mounted on the pillar 20. When correctly adjusted an image of the scale is formed after reflection from mirror 7 just outside the principal focus F of the reflector 22 and a magnified image is projected on to the screen 4. As the instrument mirror 7 rotates, different parts of the scale cross the fiduciary mark, which, to assist in the use of the instrument, may be supplemented by a sub-divided centimetre on either side. A modification is shown in Fig. 2, wherein a mangin reflector 38 is mounted slightly tilted in a lens tube to form a unit with the collimator. The centre of the Mangin reflector 38 is plain to allow the primary beam to fall on the instrument mirror from which it is reflected to strike the silvered part of the reflector 38, from which it is projected to a screen 41. If the mirror 40 is adapted for screen and lamp distances of a metre in normal use. a supplementary convex lens 42 will be required for use with the above unit.