GB133447A - - Google Patents

Abstract

133,447. Friedrich, C. Oct. 10, 1918. Eyepieces.-Luminous hair-lines are provided in optical and like instruments of precision, for work in subdued light, by suitably deep and narrow grooves in a glass or other transparent disk 6, Fig. 2, and radium-luminous material in the grooves or on the edge of the disk. The invention is described as applied to a telescope. The luminous material may be in powdered form in an annular groove 11, Fig. 3, an abutting ring 12 clamping the disk in place; or it may be placed in one or more symmetrically-disposed recesses 25 in a ring surrounding the disk, Fig. 5, the remaining portions of the disk being preferably silvered; or it may be contained between a bevelled edge of the glass disk and a clamping- ring. A method described for forming the grooves consists in coating the disk with acidresisting material, preferably transparent bakelite, removing a narrow band, say .001 inch wide, and exposing to acid fumes at # inch from the surface, neutralizing the acid by ammoniacal fumes, and washing off the coating, this cycle of operations being repeated till suitable grooves are formed. The times of exposure to the acid are, 5 seconds after the first and second coatings, 10 seconds after the third, 20 seconds after the fourth, fifth, and sixth. Lines capable of emitting light under the action of radium-luminous material may also be formed on the glass disk by deposition, for instance photographically.