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John Louis Borsch
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18,158. Borsch, J. L. Aug. 22. Lenses.-Bifocal or like lenses for spectacles, eyeglasses, and other optical devices, are made with different parts 1, 3 having different indices of refraction, to enable the same lens to be used for observing objects at different distances. Recesses are formed in the piece of glass 1 and pieces of glass 3 are ground to fit these recesses snugly ; the pieces are then welded together by heat so as to form a single plate, from which a lens is formed by grinding. Fig. 3 shows a bifocal lens, and Fig. 6 a trifocal lens, made in this manner. A small piece of glass 4, Fig. 7, may be welded to a larger piece 1 and the whole ground to form a lens of the form shown in Fig. 8. Fig. 9 shows a lens, and Fig. 10 a prism, made of two pieces of glass 6, 7 welded together edge to edge.
GB190418158D1904-08-221904-08-22Improvements in Rifocal Lenses and the like.
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